EDA Bridge Standard: one way for an AI to drive every PCB tool

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@@ -0,0 +1,441 @@+//! The copper of each layer as a raster (0.1 mm by default) inside the board outline, from the live board: tracks,+//! arcs, pads, vias and the copper Altium actually poured (its regions minus their holes); an internal plane counts as+//! copper everywhere. From it: how much of each layer is copper and how evenly the stack is balanced (bow and twist),+//! and where signal tracks run over a gap in the copper of the layer next to them (the return current's path).+use serde_json::{json, Value};+use std::collections::BTreeMap;++fn f(v: &Value) -> f64 { v.as_f64().unwrap_or(0.0) }+fn r1(v: f64) -> f64 { (v * 10.0).round() / 10.0 }+fn r3(v: f64) -> f64 { (v * 1000.0).round() / 1000.0 }++/// A layer's copper as cells of `res` mm from (x0, y0).+#[derive(Clone)]+pub struct Raster { pub x0: f64, pub y0: f64, pub res: f64, pub w: usize, pub h: usize, pub cells: Vec<bool> }++impl Raster {+    pub fn new(x0: f64, y0: f64, x1: f64, y1: f64, res: f64) -> Raster {+        let w = (((x1 - x0) / res).ceil() as usize).max(1);+        let h = (((y1 - y0) / res).ceil() as usize).max(1);+        Raster { x0, y0, res, w, h, cells: vec![false; w * h] }+    }+    fn centre(&self, i: usize, j: usize) -> (f64, f64) { (self.x0 + (i as f64 + 0.5) * self.res, self.y0 + (j as f64 + 0.5) * self.res) }+    /// cells whose centre is in [x0, x1] x [y0, y1], clipped+    fn span(&self, x0: f64, y0: f64, x1: f64, y1: f64) -> (usize, usize, usize, usize) {+        let c = |v: f64, o: f64, n: usize| (((v - o) / self.res - 0.5).max(0.0) as usize).min(n);+        let (i0, j0) = (c(x0, self.x0, self.w), c(y0, self.y0, self.h));+        let (i1, j1) = ((((x1 - self.x0) / self.res + 0.5).max(0.0) as usize).min(self.w), (((y1 - self.y0) / self.res + 0.5).max(0.0) as usize).min(self.h));+        (i0, j0, i1, j1)+    }+    pub fn at(&self, x: f64, y: f64) -> bool {+        let (i, j) = ((x - self.x0) / self.res, (y - self.y0) / self.res);+        if i < 0.0 || j < 0.0 || i >= self.w as f64 || j >= self.h as f64 { return false; }+        self.cells[j as usize * self.w + i as usize]+    }+    /// a segment of width w with round ends (a track, an arc's piece, an oval pad)+    pub fn capsule(&mut self, ax: f64, ay: f64, bx: f64, by: f64, w: f64) {+        let r = w / 2.0;+        let (i0, j0, i1, j1) = self.span(ax.min(bx) - r, ay.min(by) - r, ax.max(bx) + r, ay.max(by) + r);+        let (dx, dy) = (bx - ax, by - ay);+        let l2 = dx * dx + dy * dy;+        for j in j0..j1 { for i in i0..i1 {+            let (x, y) = self.centre(i, j);+            let t = if l2 > 0.0 { (((x - ax) * dx + (y - ay) * dy) / l2).clamp(0.0, 1.0) } else { 0.0 };+            let (px, py) = (ax + t * dx - x, ay + t * dy - y);+            if px * px + py * py <= r * r { self.cells[j * self.w + i] = true; }+        } }+    }+    /// a rectangle sx by sy centred at (cx, cy), turned `rot` degrees+    pub fn rect(&mut self, cx: f64, cy: f64, sx: f64, sy: f64, rot: f64) {+        let (c, s) = (rot.to_radians().cos(), rot.to_radians().sin());+        let e = (sx * sx + sy * sy).sqrt() / 2.0;+        let (i0, j0, i1, j1) = self.span(cx - e, cy - e, cx + e, cy + e);+        for j in j0..j1 { for i in i0..i1 {+            let (x, y) = self.centre(i, j);+            let (u, v) = ((x - cx) * c + (y - cy) * s, -(x - cx) * s + (y - cy) * c);+            if u.abs() <= sx / 2.0 && v.abs() <= sy / 2.0 { self.cells[j * self.w + i] = true; }+        } }+    }+    /// polygons filled by the even-odd rule (an outline with its holes), set to `on`+    pub fn polys(&mut self, rings: &[Vec<(f64, f64)>], on: bool) {+        let ys: Vec<f64> = rings.iter().flatten().map(|p| p.1).collect();+        if ys.is_empty() { return; }+        let (lo, hi) = (ys.iter().cloned().fold(f64::MAX, f64::min), ys.iter().cloned().fold(f64::MIN, f64::max));+        let (_, j0, _, j1) = self.span(self.x0, lo, self.x0, hi);+        for j in j0..j1 {+            let y = self.y0 + (j as f64 + 0.5) * self.res;+            let mut xs: Vec<f64> = Vec::new();+            for ring in rings {+                let n = ring.len();+                for k in 0..n {+                    let (a, b) = (ring[k], ring[(k + 1) % n]);+                    if (a.1 <= y) != (b.1 <= y) { xs.push(a.0 + (y - a.1) / (b.1 - a.1) * (b.0 - a.0)); }+                }+            }+            xs.sort_by(|a, b| a.partial_cmp(b).unwrap());+            for p in xs.chunks(2) {+                if p.len() < 2 { continue; }+                let (i0, _, i1, _) = self.span(p[0], y, p[1], y);+                for i in i0..i1 { self.cells[j * self.w + i] = on; }+            }+        }+    }+    pub fn and(&mut self, mask: &Raster) { for (c, m) in self.cells.iter_mut().zip(&mask.cells) { *c = *c && *m; } }+    pub fn count(&self) -> usize { self.cells.iter().filter(|c| **c).count() }+}++/// The stack's copper layers in order as (routing_state name, plane?, plane net).+pub fn stack_layers(stack: &Value) -> Vec<(String, bool, String)> {+    let ls: Vec<Value> = stack["layers"].as_array().cloned().unwrap_or_default();+    let n = ls.len();+    ls.iter().enumerate().map(|(i, l)| {+        if l["kind"] == "plane" { return (format!("L{}", 38 + l["plane"].as_i64().unwrap_or(1)), true, l["net"].as_str().unwrap_or("").to_string()); }+        let name = if i == 0 { "F.Cu".to_string() } else if i + 1 == n { "B.Cu".to_string() } else { format!("In{}.Cu", l["mid"].as_i64().unwrap_or(i as i64)) };+        (name, false, String::new())+    }).collect()+}++/// The outline as a ring in mm (arc edges sampled).+pub(crate) fn outline_ring(st: &Value) -> Vec<(f64, f64)> {+    let mut ring = Vec::new();+    for e in st["outlineEdges"].as_array().cloned().unwrap_or_default() {+        if e["kind"] == "arc" {+            let (cx, cy, r) = (f(&e["center"][0]), f(&e["center"][1]), f(&e["radius"]));+            let (a1, mut a2) = (f(&e["angle1"]), f(&e["angle2"]));+            if a2 <= a1 { a2 += 360.0; }+            // every 2 degrees: a chord cuts inside the arc by r(1 - cos 1deg), 3 um on a 20 mm radius (16 points per+            // arc put a hatched pour's ends 0.04 mm outside the Bluetooth Sentinel example's edge)+            let k = (((a2 - a1) / 2.0).ceil() as usize).max(4);+            for q in 0..=k { let t = (a1 + (a2 - a1) * q as f64 / k as f64).to_radians(); ring.push((cx + r * t.cos(), cy + r * t.sin())); }+        } else { ring.push((f(&e["start"][0]), f(&e["start"][1]))); }+    }+    if ring.is_empty() { ring = st["outline"].as_array().cloned().unwrap_or_default().iter().map(|p| (f(&p[0]), f(&p[1]))).collect(); }+    ring+}++/// Each layer's copper raster inside the outline. `refs` None: all copper. Some(nets): only the copper a return current+/// can use: pours, planes, those nets' own copper, and net-less copper (Altium lists a hatched pour's tracks with no+/// net: 8777 of the Bluetooth Sentinel example's 9378 tracks). Pure: routing_state, pour_state's zones, the stack.+pub fn rasters(st: &Value, zones: &[Value], layers: &[(String, bool, String)], res: f64, refs: Option<&[String]>) -> (Raster, BTreeMap<String, Raster>) {+    let ring = outline_ring(st);+    let (x0, x1) = ring.iter().fold((f64::MAX, f64::MIN), |a, p| (a.0.min(p.0), a.1.max(p.0)));+    let (y0, y1) = ring.iter().fold((f64::MAX, f64::MIN), |a, p| (a.0.min(p.1), a.1.max(p.1)));+    let mut board = Raster::new(x0, y0, x1, y1, res);+    board.polys(&[ring], true);+    let mut out = BTreeMap::new();+    for (name, plane, _) in layers {+        let mut r = Raster::new(x0, y0, x1, y1, res);+        if *plane { r.cells = board.cells.clone(); out.insert(name.clone(), r); continue; }+        {+            let keep = |n: &Value| match refs { None => true, Some(rs) => { let n = n.as_str().unwrap_or(""); n.is_empty() || rs.iter().any(|r| r.eq_ignore_ascii_case(n)) } };+            let on_layer = |l: &Value| l.as_str().map(|s| s == name || s == "*.Cu").unwrap_or(false);+            let on = |p: &Value| on_layer(&p["layer"]) && keep(&p["net"]);+            for t in st["tracks"].as_array().cloned().unwrap_or_default().iter().filter(|t| on(t)) {+                r.capsule(f(&t["start"]["x"]), f(&t["start"]["y"]), f(&t["end"]["x"]), f(&t["end"]["y"]), f(&t["width"]));+            }+            for a in st["arcs"].as_array().cloned().unwrap_or_default().iter().filter(|a| on(a)) {+                let (cx, cy, rad) = (f(&a["center"]["x"]), f(&a["center"]["y"]), f(&a["radius"]));+                let (s, mut e) = (f(&a["startAngle"]), f(&a["endAngle"]));+                if e <= s { e += 360.0; }+                let k = ((e - s) / 10.0).ceil().max(1.0) as usize;+                for q in 0..k {+                    let (t0, t1) = ((s + (e - s) * q as f64 / k as f64).to_radians(), (s + (e - s) * (q + 1) as f64 / k as f64).to_radians());+                    r.capsule(cx + rad * t0.cos(), cy + rad * t0.sin(), cx + rad * t1.cos(), cy + rad * t1.sin(), f(&a["width"]));+                }+            }+            for p in st["pads"].as_array().cloned().unwrap_or_default().iter().filter(|p| on(p)) {+                let (sx, sy) = (f(&p["sizeX"]), f(&p["sizeY"]));+                // a custom pad's real copper when the bridge sends it (Fusion's copperPoints); its bounding rectangle otherwise+                let outline: Vec<(f64, f64)> = p["copperPoints"].as_array().cloned().unwrap_or_default().iter().map(|q| (f(&q[0]), f(&q[1]))).collect();+                if outline.len() >= 3 { r.polys(&[outline], true); continue; }+                match p["shape"].as_str() {+                    Some("round") | Some("circle") if (sx - sy).abs() > 1e-6 => {+                        let (c, s) = (f(&p["rotation"]).to_radians().cos(), f(&p["rotation"]).to_radians().sin());+                        let (l, w) = ((sx - sy).abs() / 2.0, sx.min(sy));+                        let (ux, uy) = if sx > sy { (c * l, s * l) } else { (-s * l, c * l) };+                        r.capsule(f(&p["x"]) - ux, f(&p["y"]) - uy, f(&p["x"]) + ux, f(&p["y"]) + uy, w);+                    }+                    Some("round") | Some("circle") => r.capsule(f(&p["x"]), f(&p["y"]), f(&p["x"]), f(&p["y"]), sx),+                    _ => r.rect(f(&p["x"]), f(&p["y"]), sx, sy, f(&p["rotation"])),+                }+            }+            for v in st["vias"].as_array().cloned().unwrap_or_default().iter().filter(|v| keep(&v["net"])) {+                r.capsule(f(&v["position"]["x"]), f(&v["position"]["y"]), f(&v["position"]["x"]), f(&v["position"]["y"]), f(&v["size"]));+            }+        }+        for z in zones.iter().filter(|z| z["layer"].as_str() == Some(name)) {+            for fill in z["fills"].as_array().cloned().unwrap_or_default() {+                let pts = |v: &Value| v.as_array().cloned().unwrap_or_default().iter().map(|p| (f(&p[0]), f(&p[1]))).collect::<Vec<_>>();+                let mut rings = vec![pts(&fill["outline"])];+                rings.extend(fill["holes"].as_array().cloned().unwrap_or_default().iter().map(pts));+                r.polys(&rings, true);+            }+        }+        r.and(&board);+        out.insert(name.clone(), r);+    }+    (board, out)+}++/// Per layer: copper area and share of the board; per mirrored pair (1 with n, 2 with n-1...): the difference.+pub fn balance(board: &Raster, maps: &BTreeMap<String, Raster>, layers: &[(String, bool, String)]) -> (Vec<Value>, Vec<Value>) {+    let cell = board.res * board.res;+    let total = board.count() as f64;+    let pct = |name: &str| maps.get(name).map(|r| 100.0 * r.count() as f64 / total.max(1.0)).unwrap_or(0.0);+    let rows: Vec<Value> = layers.iter().map(|(n, plane, net)| {+        let mut o = json!({"layer": n, "copperMm2": r1(maps.get(n).map(|r| r.count()).unwrap_or(0) as f64 * cell), "percent": r1(pct(n))});+        if *plane { o["plane"] = json!(net); }+        o+    }).collect();+    let k = layers.len();+    let pairs = (0..k / 2).map(|i| {+        let (a, b) = (&layers[i].0, &layers[k - 1 - i].0);+        let d = (pct(a) - pct(b)).abs();+        json!({"layers": [a, b], "percent": [r1(pct(a)), r1(pct(b))], "differencePoints": r1(d), "ok": d <= 20.0})+    }).collect();+    (rows, pairs)+}++/// Per signal net: track length on each layer, and the length that runs over no reference copper on either+/// neighbouring layer, with where the first gap starts. `skip` nets are the references themselves. Pure.+pub fn return_paths(st: &Value, refs: &BTreeMap<String, Raster>, layers: &[(String, bool, String)], skip: &[String], step: f64) -> Vec<Value> {+    let idx: BTreeMap<&str, usize> = layers.iter().enumerate().map(|(i, l)| (l.0.as_str(), i)).collect();+    let mut acc: BTreeMap<(String, String), (f64, f64, Option<(f64, f64)>, Vec<(f64, f64)>)> = BTreeMap::new();+    for t in st["tracks"].as_array().cloned().unwrap_or_default() {+        let (net, layer) = (t["net"].as_str().unwrap_or(""), t["layer"].as_str().unwrap_or(""));+        if net.is_empty() || skip.iter().any(|s| s.eq_ignore_ascii_case(net)) { continue; }+        let Some(&i) = idx.get(layer) else { continue };+        let nb: Vec<&Raster> = [i.checked_sub(1), Some(i + 1)].iter().flatten().filter_map(|j| layers.get(*j)).filter_map(|l| refs.get(&l.0)).collect();+        let (ax, ay, bx, by) = (f(&t["start"]["x"]), f(&t["start"]["y"]), f(&t["end"]["x"]), f(&t["end"]["y"]));+        let len = ((bx - ax).powi(2) + (by - ay).powi(2)).sqrt();+        let n = (len / step).ceil().max(1.0) as usize;+        let e = acc.entry((net.to_string(), layer.to_string())).or_insert((0.0, 0.0, None, Vec::new()));+        e.0 += len;+        for k in 0..n {+            let s = (k as f64 + 0.5) / n as f64;+            let (x, y) = (ax + s * (bx - ax), ay + s * (by - ay));+            if !nb.iter().any(|r| r.at(x, y)) {+                e.1 += len / n as f64;+                if e.2.is_none() { e.2 = Some((r3(x), r3(y))); }+                e.3.push((x, y));+            }+        }+    }+    let mut out: Vec<Value> = acc.into_iter().filter(|(_, v)| v.1 > 0.0).map(|((net, layer), (len, gap, at, pts))| json!({+        "net": net, "layer": layer, "lengthMm": r3(len), "unreferencedMm": r3(gap), "percent": r1(100.0 * gap / len.max(1e-9)), "firstGapAt": at.map(|p| json!([p.0, p.1])),+        "gapRuns": gap_runs(&pts, 1.0).iter().map(|r| json!([r3(r.0), r3(r.1), r3(r.2), r3(r.3)])).collect::<Vec<_>>()})).collect();+    out.sort_by(|a, b| b["unreferencedMm"].as_f64().partial_cmp(&a["unreferencedMm"].as_f64()).unwrap());+    out+}++/// The gap sample points grouped into runs: boxes (x0, y0, x1, y1) of points within `join` mm of each other. Pure.+pub fn gap_runs(pts: &[(f64, f64)], join: f64) -> Vec<(f64, f64, f64, f64)> {+    let mut runs: Vec<(f64, f64, f64, f64)> = Vec::new();+    for &(x, y) in pts {+        match runs.iter_mut().find(|r| x >= r.0 - join && x <= r.2 + join && y >= r.1 - join && y <= r.3 + join) {+            Some(r) => { r.0 = r.0.min(x); r.1 = r.1.min(y); r.2 = r.2.max(x); r.3 = r.3.max(y); }+            None => runs.push((x, y, x, y)),+        }+    }+    // runs that grew into each other merge+    let mut merged = true;+    while merged {+        merged = false;+        'outer: for i in 0..runs.len() {+            for j in i + 1..runs.len() {+                let (a, b) = (runs[i], runs[j]);+                if a.0 <= b.2 + join && b.0 <= a.2 + join && a.1 <= b.3 + join && b.1 <= a.3 + join {+                    runs[i] = (a.0.min(b.0), a.1.min(b.1), a.2.max(b.2), a.3.max(b.3));+                    runs.remove(j);+                    merged = true;+                    break 'outer;+                }+            }+        }+    }+    runs+}++/// A plan that closes each gap: a pour patch `margin` mm round every gap run, on the neighbouring layer that already+/// carries the most reference copper, on that layer's reference net; as apply_pours arguments. Pure.+pub fn fix_plan(rows: &[Value], layers: &[(String, bool, String)], refs: &BTreeMap<String, Raster>, zones: &[Value], skip: &[String], board: (f64, f64, f64, f64), margin: f64) -> Vec<Value> {+    let idx: BTreeMap<&str, usize> = layers.iter().enumerate().map(|(i, l)| (l.0.as_str(), i)).collect();+    let mut pours = Vec::new();+    for row in rows {+        let Some(&i) = row["layer"].as_str().and_then(|l| idx.get(l)) else { continue };+        // a plane needs no patch (it is copper everywhere but its splits); pick the signal neighbour with most copper+        let best = [i.checked_sub(1), Some(i + 1)].iter().flatten().filter_map(|j| layers.get(*j)).filter(|l| !l.1)+            .max_by_key(|l| refs.get(&l.0).map(|r| r.count()).unwrap_or(0));+        let Some(nb) = best else { continue };+        let net = zones.iter().find(|z| z["layer"].as_str() == Some(nb.0.as_str())).and_then(|z| z["net"].as_str()).map(String::from)+            .or_else(|| skip.first().cloned());+        let Some(net) = net else { continue };+        for (k, r) in row["gapRuns"].as_array().cloned().unwrap_or_default().iter().enumerate() {+            let (x0, y0) = ((f(&r[0]) - margin).max(board.0 + 0.3), (f(&r[1]) - margin).max(board.1 + 0.3));+            let (x1, y1) = ((f(&r[2]) + margin).min(board.2 - 0.3), (f(&r[3]) + margin).min(board.3 - 0.3));+            if x1 <= x0 || y1 <= y0 { continue; }+            // does the patch overlap the reference copper already on that layer? (one that does not floats)+            let joins = refs.get(&nb.0).map(|ras| {+                let mut hit = false;+                let mut y = y0;+                while y <= y1 && !hit { let mut x = x0; while x <= x1 && !hit { hit = ras.at(x, y); x += ras.res; } y += ras.res; }+                hit+            }).unwrap_or(false);+            // removeDead off: a patch that only overlaps the pour it extends touches no pad or track of its net, and+            // Altium's dead-copper removal poured it as nothing (0 mm2, measured 2026-10-26)+            pours.push(json!({"net": net, "layer": nb.0, "name": format!("Return {} {}", row["net"].as_str().unwrap_or(""), k + 1), "removeDead": false,+                "points": [[r3(x0), r3(y0)], [r3(x1), r3(y0)], [r3(x1), r3(y1)], [r3(x0), r3(y1)]], "closes": {"net": row["net"], "layer": row["layer"]}, "joinsExistingCopper": joins}));+        }+    }+    pours+}++/// The board, its poured copper and its stack from the input bundle, or the refusal to answer.+fn gather(input: &Value) -> Result<(Value, Vec<Value>, Vec<(String, bool, String)>), Value> {+    let st = crate::input::board(input)?;+    if st["outline"].as_array().map(|a| a.len() < 3).unwrap_or(true) { return Err(crate::input::refuse("no_outline", "the board has no outline")); }+    let zones = crate::input::pours(input);+    let layers = crate::input::stack(input).map(|s| stack_layers(&s)).unwrap_or_default();+    if layers.is_empty() { return Err(crate::input::refuse("no_stack", "the input has no stack: pass the layer_stack companion as stack")); }+    Ok((st, zones, layers))+}++fn res_of(args: &Value) -> f64 { args.get("resolutionMm").and_then(|v| v.as_f64()).unwrap_or(0.1).clamp(0.02, 1.0) }++/// copper_balance: input {board, stack, pours, args: {resolutionMm?}}+pub fn copper_balance(input: &Value) -> Value {+    let (st, zones, layers) = match gather(input) { Ok(g) => g, Err(e) => return e };+    let args = &input["args"];+    let res = res_of(args);+    let (board, maps) = rasters(&st, &zones, &layers, res, None);+    let (rows, pairs) = balance(&board, &maps, &layers);+    let unpoured: Vec<Value> = st["polygons"].as_array().cloned().unwrap_or_default().iter()+        .filter(|g| !zones.iter().any(|z| z["layer"] == g["layer"] && z["net"] == g["net"] && z["filled"] == json!(true)))+        .map(|g| json!({"net": g["net"], "layer": g["layer"]})).collect();+    let ok = pairs.iter().all(|p| p["ok"] == json!(true));+    json!({"success": true, "boardMm2": r1(board.count() as f64 * res * res), "resolutionMm": res, "layers": rows, "pairs": pairs, "balanced": ok,+        "poursWithoutRegions": unpoured,+        "_hint": if ok { "Mirrored layers carry similar copper: the stack should stay flat through reflow." } else { "A mirrored pair differs by more than 20 points of copper: the board can bow or twist through reflow. Pour the lighter layer (apply_pours, a GND pour or copper thieving), or ask the fab to add thieving on its side." }})+}++/// return_path: input {board, stack, pours, args: {nets?, referenceNets?, resolutionMm?, fixMarginMm?}}+pub fn return_path(input: &Value) -> Value {+    let (st, zones, layers) = match gather(input) { Ok(g) => g, Err(e) => return e };+    let args = &input["args"];+    let res = res_of(args);+    // the reference nets: the ones that own pours or planes, unless named+    let mut skip: Vec<String> = args.get("referenceNets").and_then(|v| v.as_array()).map(|a| a.iter().filter_map(|v| v.as_str().map(String::from)).collect()).unwrap_or_default();+    if skip.is_empty() {+        skip = st["polygons"].as_array().cloned().unwrap_or_default().iter().filter_map(|g| g["net"].as_str().map(String::from))+            .chain(zones.iter().filter_map(|z| z["net"].as_str().map(String::from))).chain(layers.iter().filter(|l| l.1).map(|l| l.2.clone()))+            .filter(|n| !n.is_empty()).collect();+        skip.sort(); skip.dedup();+    }+    let (_, refs) = rasters(&st, &zones, &layers, res, Some(&skip));+    let mut rows = return_paths(&st, &refs, &layers, &skip, res);+    if let Some(want) = args.get("nets").and_then(|v| v.as_array()) {+        let w: Vec<String> = want.iter().filter_map(|v| v.as_str()).map(|s| s.to_ascii_lowercase()).collect();+        rows.retain(|r| r["net"].as_str().map(|n| w.contains(&n.to_ascii_lowercase())).unwrap_or(false));+    }+    let no_ref: Vec<&String> = layers.iter().map(|l| &l.0).filter(|n| refs.get(*n).map(|r| r.count() == 0).unwrap_or(true)).collect();+    // a plan to close the gaps, for the caller to read and run: nothing is changed here+    let bb = crate::geom::outline_bbox(&st).unwrap_or((0.0, 0.0, 0.0, 0.0));+    let margin = args.get("fixMarginMm").and_then(|v| v.as_f64()).unwrap_or(1.0);+    let patches = fix_plan(&rows, &layers, &refs, &zones, &skip, bb, margin);+    let fix = if patches.is_empty() { Value::Null } else {+        let pours: Vec<Value> = patches.iter().map(|p| { let mut q = p.clone(); if let Some(o) = q.as_object_mut() { o.remove("closes"); o.remove("joinsExistingCopper"); } q }).collect();+        let floating: Vec<Value> = patches.iter().filter(|p| p["joinsExistingCopper"] == json!(false)).map(|p| json!({"name": p["name"], "layer": p["layer"]})).collect();+        json!({"verb": "apply_pours", "args": {"pours": pours}, "patches": patches.len(), "closes": patches.iter().map(|p| p["closes"].clone()).collect::<Vec<_>>(),+               "floating": floating,+               "note": "A plan only: nothing changed. Each patch is a pour of the reference net round one gap run, on the neighbouring layer with the most reference copper. Read it (a patch can cut through other routing's space: the tool pours round it, keeping clearance), then run the verb with args, repour, and run return_path again. floating patches overlap no copper of their net yet: tie each to it with a via (place_vias) or it is an island."})+    };+    let note = if skip.is_empty() { json!("No net owns a pour or a plane on this board: there is no reference copper, so every signal is reported. Pour GND (apply_pours) or name referenceNets.") } else { Value::Null };+    json!({"success": true, "referenceNets": skip, "note": note, "layersWithNoReferenceCopper": no_ref, "nets": rows, "ok": rows.is_empty(), "resolutionMm": res, "fix": fix,+        "_hint": if rows.is_empty() { "Every signal track runs over pour or plane copper on a neighbouring layer." } else { "Each row is a net whose tracks on that layer run over no pour or plane on either neighbouring layer for unreferencedMm (from firstGapAt). Its return current detours around the gap: more loop area, more emission and crosstalk. Close the gap (extend the pour: apply_pours), route the net over solid copper, or add stitching capacitors or vias where it changes reference." }})+}++#[cfg(test)]+mod tests {+    use super::*;++    #[test]+    fn raster_shapes_have_their_area() {+        let mut r = Raster::new(0.0, 0.0, 20.0, 20.0, 0.05);+        r.rect(5.0, 5.0, 4.0, 2.0, 0.0);+        assert!((r.count() as f64 * 0.0025 - 8.0).abs() < 0.3);+        let mut c = Raster::new(0.0, 0.0, 20.0, 20.0, 0.05);+        c.capsule(10.0, 10.0, 10.0, 10.0, 4.0);+        assert!((c.count() as f64 * 0.0025 - std::f64::consts::PI * 4.0).abs() < 0.3);+        let mut p = Raster::new(0.0, 0.0, 20.0, 20.0, 0.05);+        p.polys(&[vec![(0.0, 0.0), (10.0, 0.0), (10.0, 10.0), (0.0, 10.0)], vec![(2.0, 2.0), (4.0, 2.0), (4.0, 4.0), (2.0, 4.0)]], true);+        assert!((p.count() as f64 * 0.0025 - 96.0).abs() < 0.5);+        assert!(!p.at(3.0, 3.0) && p.at(6.0, 6.0));+        // KiCad's fractured fill: the hole joined to the outline by a zero-width cut, holes empty. Same copper.+        let mut k = Raster::new(0.0, 0.0, 20.0, 20.0, 0.05);+        k.polys(&[vec![(0.0, 0.0), (10.0, 0.0), (10.0, 10.0), (0.0, 10.0), (0.0, 2.0), (2.0, 2.0), (2.0, 4.0), (4.0, 4.0), (4.0, 2.0), (2.0, 2.0), (0.0, 2.0)]], true);+        assert_eq!(k.count(), p.count());+        assert!(!k.at(3.0, 3.0) && k.at(6.0, 6.0));+    }++    #[test]+    fn a_custom_pad_is_its_copper_points_when_sent() {+        let pad = |extra: Value| { let mut p = json!({"ref": "Q1", "name": "5", "x": 5.0, "y": 5.0, "sizeX": 4.0, "sizeY": 4.0, "rotation": 0, "layer": "F.Cu", "net": "D", "shape": "rect"});+            if let Value::Object(m) = extra { for (k, v) in m { p[k] = v; } } p };+        let area = |p: Value| { let st = json!({"outline": [[0, 0], [10, 0], [10, 10], [0, 10]], "pads": [p]});+            let (_, m) = rasters(&st, &[], &[("F.Cu".into(), false, "".into())], 0.05, None); m["F.Cu"].count() as f64 * 0.0025 };+        assert!((area(pad(json!({}))) - 16.0).abs() < 0.5);+        // an L of copper inside that rectangle: 4x2 + 2x2 = 12 mm2+        assert!((area(pad(json!({"copperPoints": [[3, 3], [7, 3], [7, 5], [5, 5], [5, 7], [3, 7]]}))) - 12.0).abs() < 0.5);+    }++    fn st() -> Value {+        json!({"outline": [[0, 0], [20, 0], [20, 10], [0, 10]],+               "outlineEdges": [{"kind": "line", "start": [0.0, 0.0]}, {"kind": "line", "start": [20.0, 0.0]}, {"kind": "line", "start": [20.0, 10.0]}, {"kind": "line", "start": [0.0, 10.0]}],+               "tracks": [{"net": "SIG", "layer": "F.Cu", "width": 0.2, "start": {"x": 1.0, "y": 5.0}, "end": {"x": 19.0, "y": 5.0}}]})+    }++    #[test]+    fn balance_and_return_path_on_a_split_ground() {+        let layers = vec![("F.Cu".to_string(), false, String::new()), ("B.Cu".to_string(), false, String::new())];+        // GND poured on B.Cu over x 0..8 and 12..20: a 4 mm split under the signal+        let zones = vec![json!({"layer": "B.Cu", "net": "GND", "filled": true, "fills": [+            {"outline": [[0, 0], [8, 0], [8, 10], [0, 10]], "holes": []}, {"outline": [[12, 0], [20, 0], [20, 10], [12, 10]], "holes": []}]})];+        let (board, maps) = rasters(&st(), &zones, &layers, 0.1, None);+        let (rows, pairs) = balance(&board, &maps, &layers);+        assert!((rows[1]["percent"].as_f64().unwrap() - 80.0).abs() < 1.0);+        assert!((rows[0]["percent"].as_f64().unwrap() - 1.8).abs() < 0.5);+        assert_eq!(pairs[0]["ok"], json!(false));+        let (_, refs) = rasters(&st(), &zones, &layers, 0.1, Some(&["GND".to_string()]));+        // the signal itself is not reference copper+        assert!(!refs["F.Cu"].at(10.0, 5.0));+        let rp = return_paths(&st(), &refs, &layers, &["GND".to_string()], 0.1);+        assert_eq!(rp.len(), 1);+        assert!((rp[0]["unreferencedMm"].as_f64().unwrap() - 4.0).abs() < 0.2);+        assert_eq!(rp[0]["firstGapAt"][0].as_f64().unwrap().floor(), 8.0);+    }++    #[test]+    fn stack_names_match_routing_state() {+        let s = json!({"layers": [{"name": "Top"}, {"kind": "plane", "plane": 1, "net": "GND"}, {"kind": "signal", "mid": 1}, {"name": "Bottom"}]});+        let l = stack_layers(&s);+        assert_eq!(l.iter().map(|x| x.0.as_str()).collect::<Vec<_>>(), vec!["F.Cu", "L39", "In1.Cu", "B.Cu"]);+        assert!(l[1].1 && l[1].2 == "GND");+    }+    #[test]+    fn gap_runs_group_and_the_fix_patches_the_neighbour() {+        let pts: Vec<(f64, f64)> = (0..40).map(|k| (8.05 + k as f64 * 0.1, 5.0)).chain((0..5).map(|k| (15.0 + k as f64 * 0.1, 5.0))).collect();+        let runs = gap_runs(&pts, 1.0);+        assert_eq!(runs.len(), 2);+        let layers = vec![("F.Cu".to_string(), false, String::new()), ("B.Cu".to_string(), false, String::new())];+        let zones = vec![json!({"layer": "B.Cu", "net": "GND", "filled": true, "fills": [{"outline": [[0, 0], [8, 0], [8, 10], [0, 10]], "holes": []}]})];+        let (_, refs) = rasters(&st(), &zones, &layers, 0.1, Some(&["GND".to_string()]));+        let rows = vec![json!({"net": "SIG", "layer": "F.Cu", "gapRuns": [[8.05, 5.0, 11.95, 5.0]]})];+        let p = fix_plan(&rows, &layers, &refs, &zones, &["GND".to_string()], (0.0, 0.0, 20.0, 10.0), 1.0);+        assert_eq!(p.len(), 1);+        assert_eq!(p[0]["layer"], "B.Cu");+        assert_eq!(p[0]["net"], "GND");+        assert_eq!(p[0]["points"][0], json!([7.05, 4.0]));+        assert_eq!(p[0]["joinsExistingCopper"], json!(true));+        assert_eq!(p[0]["removeDead"], json!(false));+    }+}

@@ -0,0 +1,140 @@+//! Current capacity of a net's copper (IPC-2221): the width each layer needs for a current at an allowed temperature+//! rise, against the narrowest track the net actually has there, and how many of its vias one layer change needs.+use serde_json::{json, Map, Value};++fn f(v: &Value) -> f64 { v.as_f64().unwrap_or(0.0) }+fn r3(v: f64) -> f64 { (v * 1000.0).round() / 1000.0 }+fn r2(v: f64) -> f64 { (v * 100.0).round() / 100.0 }++const MIL: f64 = 0.0254;++/// IPC-2221's chart as a formula: the cross-section (mil^2) for `amps` at `rise` degrees C, outer or inner layer.+fn area_mil2(amps: f64, rise: f64, outer: bool) -> f64 {+    let k = if outer { 0.048 } else { 0.024 };+    (amps / (k * rise.powf(0.44))).powf(1.0 / 0.725)+}++/// The track width (mm) `amps` needs on copper `copper_um` thick.+pub fn width_for(amps: f64, rise: f64, copper_um: f64, outer: bool) -> f64 {+    let t_mil = copper_um / 1000.0 / MIL;+    area_mil2(amps, rise, outer) / t_mil * MIL+}++/// What one via carries: its barrel (plating `plating_um` around a `drill` mm hole) as an inner conductor.+pub fn via_amps(drill: f64, plating_um: f64, rise: f64) -> f64 {+    let t = plating_um / 1000.0;+    let a_mil2 = std::f64::consts::PI * (drill + t) * t / (MIL * MIL);+    0.024 * rise.powf(0.44) * a_mil2.powf(0.725)+}++/// routing_state's layer name to its index in the stack (F.Cu first, In<n>.Cu, B.Cu last).+fn stack_index(layer: &str, copper: usize) -> Option<usize> {+    match layer {+        "F.Cu" => Some(0),+        "B.Cu" => Some(copper.saturating_sub(1)),+        l => l.strip_prefix("In").and_then(|r| r.strip_suffix(".Cu")).and_then(|n| n.parse().ok()),+    }+}++/// Per net asked: each layer it is routed on with its narrowest track and the width the current needs. Pure.+pub fn check(state: &Value, copper_um: &[f64], nets: &Map<String, Value>, rise: f64, plating_um: f64) -> Vec<Value> {+    let tracks = state["tracks"].as_array().cloned().unwrap_or_default();+    let arcs = state["arcs"].as_array().cloned().unwrap_or_default();+    let vias = state["vias"].as_array().cloned().unwrap_or_default();+    let polys = state["polygons"].as_array().cloned().unwrap_or_default();+    let n = copper_um.len().max(2);+    nets.iter().map(|(net, amps)| {+        let amps = f(amps);+        let same = |v: &Value| v.as_str().map(|s| s.eq_ignore_ascii_case(net)).unwrap_or(false);+        // the narrowest piece of copper on each layer, tracks and arcs alike+        let mut narrow: std::collections::BTreeMap<String, (f64, Value)> = Default::default();+        let mut see = |layer: &str, w: f64, at: Value| {+            let e = narrow.entry(layer.to_string()).or_insert((f64::MAX, Value::Null));+            if w < e.0 { *e = (w, at); }+        };+        for t in tracks.iter().filter(|t| same(&t["net"])) { see(t["layer"].as_str().unwrap_or("?"), f(&t["width"]), json!([t["start"]["x"], t["start"]["y"]])); }+        for a in arcs.iter().filter(|a| same(&a["net"])) { see(a["layer"].as_str().unwrap_or("?"), f(&a["width"]), json!([a["center"]["x"], a["center"]["y"]])); }+        let mut short = Vec::new();+        let layers: Vec<Value> = narrow.into_iter().filter(|(l, _)| l.ends_with(".Cu")).map(|(layer, (w, at))| {+            let i = stack_index(&layer, n).unwrap_or(0);+            let outer = i == 0 || i + 1 == n;+            let cu = copper_um.get(i).copied().filter(|c| *c > 0.0).unwrap_or(35.0);+            let need = width_for(amps, rise, cu, outer);+            if w + 1e-9 < need { short.push(layer.clone()); }+            json!({"layer": layer, "copperUm": cu, "narrowestMm": r3(w), "at": at, "neededMm": r3(need), "ok": w + 1e-9 >= need})+        }).collect();+        let net_vias: Vec<&Value> = vias.iter().filter(|v| same(&v["net"])).collect();+        let smallest = net_vias.iter().map(|v| f(&v["drill"])).fold(f64::MAX, f64::min);+        let via = if net_vias.is_empty() { Value::Null } else {+            let each = via_amps(smallest, plating_um, rise);+            json!({"count": net_vias.len(), "smallestDrillMm": r3(smallest), "ampsEach": r2(each), "neededPerLayerChange": (amps / each).ceil() as i64})+        };+        let pours: Vec<Value> = polys.iter().filter(|p| same(&p["net"])).map(|p| p["layer"].clone()).collect();+        json!({"net": net, "amps": amps, "layers": layers, "shortOn": short, "ok": short.is_empty(), "vias": via, "poursOn": pours})+    }).collect()+}++/// current_capacity: input {board, stack?, args: {nets: {net: amps}, riseC?, platingUm?}}. Without a stack every layer+/// is taken as 35 um (1 oz) copper, and the reply says so.+pub fn current_capacity(input: &Value) -> Value {+    let args = &input["args"];+    let nets = match args.get("nets").and_then(|v| v.as_object()) {+        Some(m) if !m.is_empty() && m.values().all(|v| v.as_f64().map(|a| a > 0.0).unwrap_or(false)) => m.clone(),+        _ => return json!({"success": false, "errorCode": "bad_args", "error": "nets is {net: amps}, e.g. {\"VIN\": 3, \"GND\": 3}"}),+    };+    let rise = args.get("riseC").and_then(|v| v.as_f64()).unwrap_or(10.0);+    let plating = args.get("platingUm").and_then(|v| v.as_f64()).unwrap_or(25.0);+    let st = match crate::input::board(input) { Ok(b) => b, Err(e) => return e };+    let missing: Vec<&String> = nets.keys().filter(|k| !st["nets"].as_array().map(|a| a.iter().any(|n| n.as_str().map(|s| s.eq_ignore_ascii_case(k)).unwrap_or(false))).unwrap_or(false)).collect();+    if !missing.is_empty() { return json!({"success": false, "errorCode": "no_such_net", "error": format!("not nets on this board: {missing:?}"), "nets": st["nets"]}); }+    let stack = crate::input::stack(input);+    let copper: Vec<f64> = stack.as_ref().and_then(|s| s["layers"].as_array().cloned()).unwrap_or_default().iter().map(|l| f(&l["copperUm"])).collect();+    let rows = check(&st, &copper, &nets, rise, plating);+    let all_ok = rows.iter().all(|r| r["ok"].as_bool() == Some(true));+    json!({"success": true, "riseC": rise, "platingUm": plating, "nets": rows, "ok": all_ok,+        "assumed": if copper.is_empty() { json!("no stack in the input: every layer taken as 35 um (1 oz) copper") } else { Value::Null },+        "_hint": if all_ok { "Every routed layer of these nets carries its current within the temperature rise (IPC-2221). Vias: a layer change needs neededPerLayerChange of them side by side." }+                 else { "shortOn names the layers whose narrowest copper is under neededMm: widen it (set_track_width, or a width rule with add_rule) or pour the net (apply_pours). A pour on the same layer (poursOn) may already carry the current; the check reads tracks only." }})+}++#[cfg(test)]+mod tests {+    use super::*;++    #[test]+    fn ipc_2221_matches_its_chart() {+        // 1 oz (35 um) outer copper, 10 C rise: 1 A needs about 0.30 mm (12 mil), 3 A about 1.4 mm+        let w1 = width_for(1.0, 10.0, 35.0, true);+        assert!((0.25..0.35).contains(&w1), "{w1}");+        let w3 = width_for(3.0, 10.0, 35.0, true);+        assert!((1.2..1.6).contains(&w3), "{w3}");+        // inner layers need about 2.6x the width+        assert!(width_for(1.0, 10.0, 35.0, false) / w1 > 2.4);+        // a 0.3 mm via with 25 um plating carries roughly 1 to 1.5 A at 10 C+        let v = via_amps(0.3, 25.0, 10.0);+        assert!((0.8..1.6).contains(&v), "{v}");+    }++    #[test]+    fn check_finds_the_narrow_layer() {+        let st = json!({"tracks": [{"net": "VIN", "layer": "F.Cu", "width": 1.5, "start": {"x": 0.0, "y": 0.0}}, {"net": "VIN", "layer": "B.Cu", "width": 0.3, "start": {"x": 4.0, "y": 1.0}}],+                        "vias": [{"net": "VIN", "drill": 0.3}, {"net": "VIN", "drill": 0.4}], "polygons": [{"net": "VIN", "layer": "B.Cu"}]});+        let nets = json!({"VIN": 3.0}).as_object().unwrap().clone();+        let r = &check(&st, &[35.0, 35.0], &nets, 10.0, 25.0)[0];+        assert_eq!(r["shortOn"], json!(["B.Cu"]));+        assert_eq!(r["vias"]["smallestDrillMm"], 0.3);+        assert!(r["vias"]["neededPerLayerChange"].as_i64().unwrap() >= 2);+        assert_eq!(r["poursOn"], json!(["B.Cu"]));+    }++    #[test]+    fn the_verb_says_what_it_assumed_and_refuses_unknown_nets() {+        let st = json!({"nets": ["VIN"], "tracks": [{"net": "VIN", "layer": "F.Cu", "width": 0.2, "start": {"x": 0.0, "y": 0.0}}]});+        let r = current_capacity(&json!({"board": st, "args": {"nets": {"VIN": 2}}}));+        assert_eq!(r["ok"], json!(false));+        assert!(r["assumed"].as_str().unwrap().contains("35 um"));+        assert_eq!(current_capacity(&json!({"board": st, "args": {"nets": {"VOUT": 1}}}))["errorCode"], "no_such_net");+        assert_eq!(current_capacity(&json!({"board": st, "args": {}}))["errorCode"], "bad_args");+    }+}+

@@ -0,0 +1,294 @@+//! The board's fab-relevant minimums, measured from the board model, and how they compare with a fab's limits: the+//! numbers a fab's order form and capability page ask about, so the AI can check a board before ordering. Fab limits+//! are never kept here: they come in as a record from adom/pcb-design-rules (`fab`), or as explicit `limits`.+use serde_json::{json, Map, Value};++fn f(v: &Value) -> f64 { v.as_f64().unwrap_or(0.0) }+fn r3(v: f64) -> f64 { (v * 1000.0).round() / 1000.0 }++/// The nearest copper (track, arc, pad, via) to the real outline, edge of copper to the outline's line, mm. Pour+/// boundaries are left out: they are drawn on the edge and the tool pulls the poured copper back by its rules.+pub fn edge_distance(state: &Value) -> Option<(f64, Value)> {+    let ring = crate::coppermap::outline_ring(state);+    if ring.len() < 3 { return None; }+    let seg = |x: f64, y: f64| -> f64 {+        (0..ring.len()).map(|k| {+            let (a, b) = (ring[k], ring[(k + 1) % ring.len()]);+            let (dx, dy) = (b.0 - a.0, b.1 - a.1);+            let l2 = dx * dx + dy * dy;+            let t = if l2 > 0.0 { (((x - a.0) * dx + (y - a.1) * dy) / l2).clamp(0.0, 1.0) } else { 0.0 };+            ((a.0 + t * dx - x).powi(2) + (a.1 + t * dy - y).powi(2)).sqrt()+        }).fold(f64::MAX, f64::min)+    };+    let copper = |l: &Value| l.as_str().map(|s| s.ends_with(".Cu")).unwrap_or(false);+    let mut pts: Vec<(f64, f64, f64, Value)> = Vec::new();+    for t in state["tracks"].as_array().cloned().unwrap_or_default().iter().filter(|t| copper(&t["layer"])) {+        for p in [&t["start"], &t["end"]] { pts.push((f(&p["x"]), f(&p["y"]), f(&t["width"]) / 2.0, json!({"track": t["net"], "layer": t["layer"]}))); }+    }+    for v in state["vias"].as_array().cloned().unwrap_or_default() { pts.push((f(&v["position"]["x"]), f(&v["position"]["y"]), f(&v["size"]) / 2.0, json!({"via": v["net"]}))); }+    for p in state["pads"].as_array().cloned().unwrap_or_default() {+        let (rf, nm) = (p["ref"].as_str().unwrap_or(""), p["name"].as_str().unwrap_or(""));+        pts.push((f(&p["x"]), f(&p["y"]), f(&p["sizeX"]).max(f(&p["sizeY"])) / 2.0, json!({"pad": if rf.is_empty() { nm.to_string() } else { format!("{rf}.{nm}") }})));+    }+    pts.into_iter().map(|(x, y, half, mut what)| { what["at"] = json!([r3(x), r3(y)]); (r3(seg(x, y) - half), what) })+        .min_by(|a, b| a.0.partial_cmp(&b.0).unwrap())+}++/// The smallest of each feature with where it is. Pure, for the tests.+pub fn measure(state: &Value) -> Map<String, Value> {+    let mut m = Map::new();+    let mut min_by = |key: &str, items: Vec<(f64, Value)>| {+        if let Some((v, at)) = items.into_iter().filter(|(v, _)| *v > 0.0).min_by(|a, b| a.0.partial_cmp(&b.0).unwrap()) {+            m.insert(key.into(), json!({"mm": r3(v), "at": at}));+        }+    };+    // copper only: outline and drawing lines on mechanical layers (L57...) are not tracks a fab etches+    let copper = |l: &Value| l.as_str().map(|s| s == "F.Cu" || s == "B.Cu" || (s.starts_with("In") && s.ends_with(".Cu"))).unwrap_or(false);+    min_by("track", state["tracks"].as_array().cloned().unwrap_or_default().iter().filter(|t| copper(&t["layer"])).map(|t| (f(&t["width"]), json!({"net": t["net"], "layer": t["layer"], "from": [t["start"]["x"], t["start"]["y"]]}))).collect());+    let vias = state["vias"].as_array().cloned().unwrap_or_default();+    min_by("viaDrill", vias.iter().map(|v| (f(&v["drill"]), json!({"net": v["net"], "at": [v["position"]["x"], v["position"]["y"]]}))).collect());+    min_by("viaDiameter", vias.iter().map(|v| (f(&v["size"]), json!({"net": v["net"], "at": [v["position"]["x"], v["position"]["y"]]}))).collect());+    min_by("viaAnnularRing", vias.iter().map(|v| ((f(&v["size"]) - f(&v["drill"])) / 2.0, json!({"net": v["net"], "at": [v["position"]["x"], v["position"]["y"]]}))).collect());+    let pads = state["pads"].as_array().cloned().unwrap_or_default();+    let drilled: Vec<&Value> = pads.iter().filter(|p| f(&p["drill"]) > 0.0).collect();+    let label = |p: &Value| json!({"pad": format!("{}.{}", p["ref"].as_str().unwrap_or(""), p["name"].as_str().unwrap_or("")), "at": [p["x"], p["y"]]});+    min_by("padHole", drilled.iter().map(|p| (f(&p["drill"]), label(p))).collect());+    // a pad's ring on its narrow side (a round hole in an oblong pad)+    min_by("padAnnularRing", drilled.iter().filter(|p| f(&p["sizeX"]) > f(&p["drill"])).map(|p| ((f(&p["sizeX"]).min(f(&p["sizeY"])) - f(&p["drill"])) / 2.0, label(p))).collect());+    min_by("smdPad", pads.iter().filter(|p| f(&p["drill"]) == 0.0).map(|p| (f(&p["sizeX"]).min(f(&p["sizeY"])), label(p))).collect());+    if let Some((x0, y0, x1, y1)) = crate::geom::outline_bbox(state) {+        m.insert("boardSize".into(), json!({"mm": [r3(x1 - x0), r3(y1 - y0)]}));+        let _ = (x0, y0, x1, y1);+        if let Some((d, mut at)) = edge_distance(state) { at["mm"] = json!(d); m.insert("edgeClearance".into(), at); }+    }+    // drilled holes: the largest, and the closest pair edge to edge (via to via, and any pair with a pad hole)+    let mut holes: Vec<(f64, f64, f64, bool, Value)> = vias.iter().map(|v| (f(&v["position"]["x"]), f(&v["position"]["y"]), f(&v["drill"]), false, json!({"via": v["net"], "at": [v["position"]["x"], v["position"]["y"]]}))).collect();+    holes.extend(drilled.iter().map(|p| (f(&p["x"]), f(&p["y"]), f(&p["drill"]), true, label(p))));+    if let Some(h) = holes.iter().max_by(|a, b| a.2.partial_cmp(&b.2).unwrap()) { m.insert("largestDrill".into(), json!({"mm": r3(h.2), "at": h.4})); }+    holes.sort_by(|a, b| a.0.partial_cmp(&b.0).unwrap());+    let (mut vv, mut pp): (Option<(f64, Value)>, Option<(f64, Value)>) = (None, None);+    for i in 0..holes.len() {+        for j in i + 1..holes.len() {+            let (a, b) = (&holes[i], &holes[j]);+            if b.0 - a.0 > 10.0 { break; }+            let d = ((a.0 - b.0).powi(2) + (a.1 - b.1).powi(2)).sqrt() - (a.2 + b.2) / 2.0;+            if (a.0 - b.0).abs() < 1e-6 && (a.1 - b.1).abs() < 1e-6 { continue; } // a via in a pad+            let slot = if a.3 || b.3 { &mut pp } else { &mut vv };+            if slot.as_ref().map(|s| d < s.0).unwrap_or(true) { *slot = Some((d, json!([a.4.clone(), b.4.clone()]))); }+        }+    }+    if let Some((d, at)) = vv { m.insert("holeToHoleVia".into(), json!({"mm": r3(d), "at": at})); }+    if let Some((d, at)) = pp { m.insert("holeToHolePad".into(), json!({"mm": r3(d), "at": at})); }+    m.insert("counts".into(), json!({"tracks": state["tracks"].as_array().map(|a| a.len()), "vias": vias.len(), "pads": pads.len(), "drilledPads": drilled.len()}));+    m+}++/// The measured values against the caller's limits; each limit names its feature (min*, or max for board and layers).+pub fn compare(meas: &Map<String, Value>, limits: &Map<String, Value>, clearance: Option<f64>, layers: Option<i64>) -> Vec<Value> {+    let mut out = Vec::new();+    let got = |k: &str| meas.get(k).and_then(|v| v["mm"].as_f64());+    for (limit, feature) in [("minTrack", "track"), ("minViaDrill", "viaDrill"), ("minViaDiameter", "viaDiameter"), ("minViaAnnularRing", "viaAnnularRing"),+                             ("minPadHole", "padHole"), ("minPadAnnularRing", "padAnnularRing"), ("minSmdPad", "smdPad"),+                             ("minEdgeClearance", "edgeClearance"), ("minHoleToHoleVia", "holeToHoleVia"), ("minHoleToHolePad", "holeToHolePad"),+                             ("minSilkLine", "silkLine"), ("minSilkText", "silkText")] {+        if let (Some(l), Some(v)) = (limits.get(limit).and_then(|x| x.as_f64()), got(feature)) {+            if v + 1e-9 < l { out.push(json!({"limit": limit, "limitMm": l, "boardMm": v, "at": meas[feature]["at"]})); }+        }+    }+    if let (Some(l), Some(c)) = (limits.get("minClearance").and_then(|x| x.as_f64()), clearance) {+        if c + 1e-9 < l { out.push(json!({"limit": "minClearance", "limitMm": l, "boardMm": c, "at": "the board's clearance rule"})); }+    }+    if let (Some(l), Some(n)) = (limits.get("maxLayers").and_then(|x| x.as_i64()), layers) {+        if n > l { out.push(json!({"limit": "maxLayers", "limit_": l, "board": n})); }+    }+    if let (Some(l), Some(v)) = (limits.get("maxDrill").and_then(|x| x.as_f64()), got("largestDrill")) {+        if v > l + 1e-9 { out.push(json!({"limit": "maxDrill", "limitMm": l, "boardMm": v, "at": meas["largestDrill"]["at"], "note": "larger holes are milled (routed) instead"})); }+    }+    if let (Some(lim), Some(sz)) = (limits.get("minBoardMm").and_then(|x| x.as_array()), meas.get("boardSize").and_then(|b| b["mm"].as_array())) {+        let (lw, lh) = (lim.first().and_then(|x| x.as_f64()).unwrap_or(0.0), lim.get(1).and_then(|x| x.as_f64()).unwrap_or(0.0));+        let (w, h) = (sz[0].as_f64().unwrap_or(0.0), sz[1].as_f64().unwrap_or(0.0));+        if w.min(h) + 1e-9 < lw.min(lh) || w.max(h) + 1e-9 < lw.max(lh) { out.push(json!({"limit": "minBoardMm", "limitMm": [lw, lh], "boardMm": [w, h]})); }+    }+    if let (Some(lim), Some(sz)) = (limits.get("maxBoardMm").and_then(|x| x.as_array()), meas.get("boardSize").and_then(|b| b["mm"].as_array())) {+        let (lw, lh) = (lim.first().and_then(|x| x.as_f64()).unwrap_or(f64::MAX), lim.get(1).and_then(|x| x.as_f64()).unwrap_or(f64::MAX));+        let (w, h) = (sz[0].as_f64().unwrap_or(0.0), sz[1].as_f64().unwrap_or(0.0));+        // either orientation fits+        if !((w <= lw && h <= lh) || (w <= lh && h <= lw)) { out.push(json!({"limit": "maxBoardMm", "limitMm": [lw, lh], "boardMm": [w, h]})); }+    }+    out+}++/// The smallest clearance among the board's enabled clearance rules, in mm. A rule gives it as a number+/// (`clearanceMm`, `gapMm` or `minMm`) or in a descriptor the tool wrote ("Gap=10mil", "Gap=0.2mm": Altium's form).+pub fn min_clearance(rules: &[Value]) -> Option<f64> {+    rules.iter().filter(|r| r["kind"].as_i64() == Some(0) || r["kind"].as_str().map(|k| k.eq_ignore_ascii_case("clearance")).unwrap_or(false)+            || r["kindName"].as_str() == Some("Clearance") || r["name"].as_str().map(|n| n.to_lowercase().contains("clearance")).unwrap_or(false))+        .filter(|r| r["enabled"].as_bool() != Some(false))+        .filter_map(|r| {+            if let Some(v) = ["clearanceMm", "gapMm", "minMm"].iter().find_map(|k| r[*k].as_f64()) { return Some(v); }+            let d = r["descriptor"].as_str()?;+            let i = d.find("Gap=")? + 4;+            let num: String = d[i..].chars().take_while(|c| c.is_ascii_digit() || *c == '.').collect();+            let v: f64 = num.parse().ok()?;+            let unit = &d[i + num.len()..];+            Some(if unit.starts_with("mil") { v * 0.0254 } else { v })+        }).reduce(f64::min).map(r3)+}++/// A pcb-design-rules record (one entry of `rules/records/<vendor>.json`'s `records`, with the file's `vendor`) as the+/// limits this check compares, plus what to say about where they came from. Limits the record does not give are left+/// out, never guessed. Pure.+pub fn limits_from_record(rec: &Value, vendor: &str) -> (Map<String, Value>, Value) {+    let mut l = Map::new();+    let mut put = |k: &str, v: Option<f64>| { if let Some(v) = v { l.insert(k.into(), json!(v)); } };+    put("minTrack", rec["minTraceWidth"]["mm"].as_f64());+    put("minClearance", rec["minCopperClearance"]["mm"].as_f64().or(rec["minSpacing"]["mm"].as_f64()));+    put("minViaDrill", rec["minVia"]["drillMm"].as_f64());+    put("minViaDiameter", rec["minVia"]["padMm"].as_f64());+    put("minPadHole", rec["minDrill"]["mm"].as_f64());+    // the record's annular ring is the plated-through-hole ring ("PTH ... absolute minimum")+    put("minPadAnnularRing", rec["annularRing"]["viaMm"].as_f64());+    put("minEdgeClearance", rec["copperToBoardEdge"]["mm"].as_f64());+    put("minHoleToHoleVia", rec["holeToHole"]["mm"].as_f64());+    put("minSilkLine", rec["silkLineWidth"]["mm"].as_f64());+    if let (Some(x), Some(y)) = (rec["maxBoardSize"]["xMm"].as_f64(), rec["maxBoardSize"]["yMm"].as_f64()) { l.insert("maxBoardMm".into(), json!([x, y])); }+    if let Some(n) = rec["layerCount"].as_i64() { l.insert("maxLayers".into(), json!(n)); }+    let src = rec["sources"].as_array().and_then(|s| s.first()).cloned().unwrap_or(Value::Null);+    let conditions: Map<String, Value> = rec.as_object().map(|o| o.iter().filter_map(|(k, v)| v.get("condition").map(|c| (k.clone(), c.clone()))).collect()).unwrap_or_default();+    let fab = json!({"name": vendor, "process": rec["process"], "layers": rec["layerCount"], "source": src["url"], "read": src["dateRead"],+                     "conditions": conditions, "notes": rec["notes"]});+    (l, fab)+}++/// fab_check: input {board, stack?, rules?, silk?, fab?, args: {limits?, copperOz?}}. `fab` is a pcb-design-rules+/// record (one of a vendor file's `records`, with `vendor` beside it or given as args.vendor); `limits` adds or+/// overrides any limit by name, in mm.+pub fn fab_check(input: &Value) -> Value {+    let st = match crate::input::board(input) { Ok(b) => b, Err(e) => return e };+    let args = &input["args"];+    let mut meas = measure(&st);+    let rule_list = crate::input::rules(input);+    let clearance = min_clearance(&rule_list);+    if let Some(c) = clearance { meas.insert("clearanceRule".into(), json!({"mm": c})); }+    let stack = crate::input::stack(input);+    let layers = stack.as_ref().and_then(|s| s["copperLayers"].as_i64());+    if let Some(n) = layers { meas.insert("copperLayers".into(), json!(n)); }+    let mut limits = Map::new();+    let mut fab = Value::Null;+    if let Some(rec) = input.get("fab").filter(|r| !r.is_null()) {+        let vendor = rec["vendor"].as_str().or(args["vendor"].as_str()).unwrap_or("the fab").to_string();+        let (l, mut fv) = limits_from_record(rec, &vendor);+        if let (Some(want), Some(n)) = (rec["layerCount"].as_i64(), layers) {+            if want != n { fv["mismatch"] = json!(format!("the record is for {want} layers; the board has {n}: pass the {n}-layer record")); }+        }+        // the record's limits hold for its stated copper (1 oz outer as a rule); heavier copper needs wider tracks+        let outer_um = stack.as_ref().and_then(|s| s["layers"][0]["copperUm"].as_f64()).unwrap_or(35.0);+        let oz = args["copperOz"].as_f64().unwrap_or(outer_um / 35.0);+        fv["copperOz"] = json!(r3(oz));+        if oz >= 1.75 { fv["copperNote"] = json!("the board's outer copper is heavier than the record's 1 oz condition: its notes give the wider track and gap limits for heavier copper; pass them as limits"); }+        limits = l;+        fab = fv;+    }+    for (k, v) in args["limits"].as_object().cloned().unwrap_or_default() { limits.insert(k, v); }+    // silkscreen sizes from silk_state, only when a limit asks and the input has it+    if limits.contains_key("minSilkText") || limits.contains_key("minSilkLine") {+        if let Some(silk) = crate::input::part(input, "silk") {+            let mut texts: Vec<(f64, Value)> = silk["texts"].as_array().cloned().unwrap_or_default().iter().filter(|t| t["side"] != "other").map(|t| (f(&t["size"]), json!({"text": t["text"], "at": [t["x"], t["y"]]}))).collect();+            for c in silk["components"].as_array().cloned().unwrap_or_default() {+                for k in ["name", "comment"] { if c[k]["shown"].as_bool() == Some(true) { texts.push((f(&c[k]["size"]), json!({"ref": c["ref"], "text": c[k]["text"], "at": [c[k]["x"], c[k]["y"]]}))); } }+            }+            if let Some((v, at)) = texts.into_iter().filter(|t| t.0 > 0.0).min_by(|a, b| a.0.partial_cmp(&b.0).unwrap()) { meas.insert("silkText".into(), json!({"mm": r3(v), "at": at})); }+            if let Some(l) = silk["lines"].as_array().cloned().unwrap_or_default().iter().filter(|l| l["side"] != "other" && f(&l["width"]) > 0.0).min_by(|a, b| f(&a["width"]).partial_cmp(&f(&b["width"])).unwrap()) {+                meas.insert("silkLine".into(), json!({"mm": r3(f(&l["width"])), "at": [l["x1"], l["y1"]]}));+            }+        }+    }+    let mut fails = compare(&meas, &limits, clearance, layers);+    // each finding names where its limit came from+    if !fab.is_null() { for x in fails.iter_mut() { x["source"] = json!({"name": fab["name"], "url": fab["source"], "read": fab["read"]}); } }+    let unseen: Vec<&str> = [("minClearance", clearance.is_some()), ("minSilkText", meas.contains_key("silkText")), ("minSilkLine", meas.contains_key("silkLine")), ("maxLayers", layers.is_some())]+        .iter().filter(|(k, seen)| limits.contains_key(*k) && !seen).map(|(k, _)| *k).collect();+    json!({"success": true, "fab": fab, "measured": meas, "limitsChecked": limits.keys().collect::<Vec<_>>(), "outsideLimits": fails,+        "notChecked": unseen, "fits": if limits.is_empty() { Value::Null } else { json!(fails.is_empty()) },+        "costlierOrBelowRecommended": [],+        "_hint": if limits.is_empty() { "Measured only. Pass a fab's record from adom/pcb-design-rules as fab, or limits:{minTrack, minClearance, minViaDrill, minViaDiameter, minViaAnnularRing, minPadHole, minPadAnnularRing, minSmdPad, minEdgeClearance, minHoleToHoleVia, minHoleToHolePad, maxDrill, minSilkLine, minSilkText, maxLayers, minBoardMm:[w,h], maxBoardMm:[w,h]} in mm, to check them." }+                 else { "outsideLimits names each feature below the fab's limit, where it is, and the page the limit came from. notChecked lists limits the input gave nothing to measure against (pass rules, stack or silk). Read fab.notes: costlier options and recommended sizes are there. Fix the board (set_track_width, add_rule, a footprint change) or choose the fab's advanced service; then run run_drc." }})+}++#[cfg(test)]+mod tests {+    use super::*;++    fn board() -> Value {+        json!({"tracks": [{"width": 0.25, "net": "A", "layer": "F.Cu", "start": {"x": 0.0, "y": 0.0}}, {"width": 0.1, "net": "B", "layer": "B.Cu", "start": {"x": 5.0, "y": 5.0}}, {"width": 0.05, "net": "", "layer": "L57", "start": {"x": 0.0, "y": 0.0}}],+               "vias": [{"size": 0.6, "drill": 0.3, "net": "GND", "position": {"x": 1.0, "y": 1.0}}, {"size": 0.45, "drill": 0.25, "net": "B", "position": {"x": 2.0, "y": 2.0}}],+               "pads": [{"ref": "J1", "name": "1", "x": 0.0, "y": 0.0, "sizeX": 1.7, "sizeY": 1.7, "drill": 1.0}, {"ref": "U1", "name": "3", "x": 3.0, "y": 0.0, "sizeX": 0.3, "sizeY": 1.0, "drill": 0.0}],+               "outline": [[0, 0], [50, 0], [50, 30], [0, 30]]})+    }++    #[test]+    fn the_smallest_features_are_found_with_where_they_are() {+        let m = measure(&board());+        assert_eq!(m["track"]["mm"], json!(0.1));+        assert_eq!(m["track"]["at"]["net"], json!("B"));+        assert_eq!((m["viaDrill"]["mm"].clone(), m["viaDiameter"]["mm"].clone(), m["viaAnnularRing"]["mm"].clone()), (json!(0.25), json!(0.45), json!(0.1)));+        assert_eq!((m["padHole"]["mm"].clone(), m["padAnnularRing"]["mm"].clone(), m["smdPad"]["mm"].clone()), (json!(1.0), json!(0.35), json!(0.3)));+        assert_eq!(m["boardSize"]["mm"], json!([50.0, 30.0]));+    }++    #[test]+    fn arc_edges_count_toward_the_board_size() {+        let b = json!({"outline": [[0, 0], [10, 0]], "outlineEdges": [{"kind": "arc", "center": [5.0, 0.0], "radius": 5.0, "angle1": 0.0, "angle2": 180.0}]});+        assert_eq!(measure(&b)["boardSize"]["mm"], json!([10.0, 5.0]));+    }++    #[test]+    fn limits_name_what_falls_short_and_a_board_fits_either_way_round() {+        let m = measure(&board());+        let lim = json!({"minTrack": 0.127, "minViaDrill": 0.3, "maxBoardMm": [30, 60], "maxLayers": 2, "minClearance": 0.127});+        let f = compare(&m, lim.as_object().unwrap(), Some(0.1), Some(2));+        let names: Vec<&str> = f.iter().map(|x| x["limit"].as_str().unwrap()).collect();+        assert_eq!(names, vec!["minTrack", "minViaDrill", "minClearance"]);+    }++    #[test]+    fn clearance_is_read_from_rule_descriptors_in_mil_or_mm() {+        let rules = vec![json!({"kind": 0, "descriptor": "Clearance Constraint (Gap=10mil) (All),(All)", "enabled": true}),+                         json!({"kind": 0, "descriptor": "Clearance Constraint (Gap=0.15mm) (InNet('SW')),(All)", "enabled": true}),+                         json!({"kind": 0, "descriptor": "Clearance Constraint (Gap=0.05mm) (All),(All)", "enabled": false})];+        assert_eq!(min_clearance(&rules), Some(0.15));+    }+    /// JLCPCB's 2-layer record as adom/pcb-design-rules gives it (rules/records/jlcpcb.json, read 2026-09-03), trimmed+    fn jlc_2l() -> Value {+        json!({"vendor": "JLCPCB", "process": "standard", "layerCount": 2, "minTraceWidth": {"mm": 0.1, "condition": "1 oz copper outer layer"},+               "minSpacing": {"mm": 0.1}, "minDrill": {"mm": 0.15}, "minVia": {"drillMm": 0.15, "padMm": 0.25}, "annularRing": {"viaMm": 0.18},+               "copperToBoardEdge": {"mm": 0.2}, "holeToHole": {"mm": 0.2}, "silkLineWidth": {"mm": 0.15}, "minCopperClearance": {"mm": 0.1},+               "maxBoardSize": {"xMm": 670.0, "yMm": 600.0}, "notes": "Min drill 0.15 mm costs more.",+               "sources": [{"url": "https://jlcpcb.com/capabilities/pcb-capabilities", "dateRead": "2026-09-03"}]})+    }++    #[test]+    fn a_pcb_design_rules_record_becomes_limits_with_its_source() {+        let (l, fab) = limits_from_record(&jlc_2l(), "JLCPCB");+        assert_eq!((l["minTrack"].clone(), l["minClearance"].clone(), l["minPadAnnularRing"].clone()), (json!(0.1), json!(0.1), json!(0.18)));+        assert_eq!(l["maxBoardMm"], json!([670.0, 600.0]));+        assert!(!l.contains_key("minSilkText"), "a limit the record does not give is not guessed");+        assert_eq!((fab["source"].as_str(), fab["read"].as_str()), (Some("https://jlcpcb.com/capabilities/pcb-capabilities"), Some("2026-09-03")));+        // a 0.08 mm track fails, holes 0.15 mm apart edge to edge fail the via rule; each finding names the page+        let st = json!({"tracks": [{"width": 0.08, "net": "A", "layer": "F.Cu", "start": {"x": 1.0, "y": 1.0}}],+                        "vias": [{"drill": 0.3, "size": 0.6, "net": "A", "position": {"x": 0.0, "y": 0.0}}, {"drill": 0.3, "size": 0.6, "net": "B", "position": {"x": 0.45, "y": 0.0}}],+                        "outline": [[-5, -5], [5, -5], [5, 5], [-5, 5]]});+        let r = fab_check(&json!({"board": st, "stack": {"copperLayers": 2, "layers": [{"copperUm": 35}, {"copperUm": 35}]}, "fab": jlc_2l()}));+        let fails: Vec<&str> = r["outsideLimits"].as_array().unwrap().iter().map(|f| f["limit"].as_str().unwrap()).collect();+        assert!(fails.contains(&"minTrack") && fails.contains(&"minHoleToHoleVia"), "{fails:?}");+        assert_eq!(r["outsideLimits"][0]["source"]["read"], "2026-09-03");+        assert_eq!(r["fits"], json!(false));+        // no rules in the input: the clearance limit is reported as not checked, never passed+        assert!(r["notChecked"].as_array().unwrap().contains(&json!("minClearance")));+    }++    #[test]+    fn clearance_from_a_standard_rule() {+        assert_eq!(min_clearance(&[json!({"kind": "clearance", "clearanceMm": 0.127}), json!({"kind": "clearance", "gapMm": 0.2})]), Some(0.127));+    }+}

@@ -0,0 +1,234 @@+//! Controlled impedance from the board's stack-up (the layer_stack companion): the track width (and pair gap) each copper layer needs for a+//! target impedance, by closed-form models (Hammerstad-Jensen microstrip, Wheeler stripline, IPC-2141 coupling). Within+//! a few percent of a field solver for ordinary FR-4 geometry; the fab's stack-up and its solver have the last word.+use serde_json::{json, Value};+use std::f64::consts::PI;++fn r3(v: f64) -> f64 { (v * 1000.0).round() / 1000.0 }+fn r1(v: f64) -> f64 { (v * 10.0).round() / 10.0 }++/// Free-space impedance of a microstrip of width ratio u (Hammerstad-Jensen).+fn z01(u: f64) -> f64 {+    let f = 6.0 + (2.0 * PI - 6.0) * (-(30.666 / u).powf(0.7528)).exp();+    60.0 * (f / u + (1.0 + 4.0 / (u * u)).sqrt()).ln()+}++fn eeff0(u: f64, er: f64) -> f64 {+    let a = 1.0 + ((u.powi(4) + (u / 52.0).powi(2)) / (u.powi(4) + 0.432)).ln() / 49.0 + (1.0 + (u / 18.1).powi(3)).ln() / 18.7;+    let b = 0.564 * ((er - 0.9) / (er + 3.0)).powf(0.053);+    (er + 1.0) / 2.0 + (er - 1.0) / 2.0 * (1.0 + 10.0 / u).powf(-a * b)+}++/// Uncoated microstrip: width w over a plane h below, copper t thick, dielectric er (any length unit).+pub fn microstrip(w: f64, h: f64, t: f64, er: f64) -> f64 {+    let u = w / h;+    let tn = t / h;+    let coth = |x: f64| x.cosh() / x.sinh();+    let du1 = if tn > 0.0 { tn / PI * (1.0 + 4.0 * std::f64::consts::E / (tn * coth((6.517 * u).sqrt()).powi(2))).ln() } else { 0.0 };+    let dur = 0.5 * (1.0 + 1.0 / (er - 1.0).sqrt().cosh()) * du1;+    let (u1, ur) = (u + du1, u + dur);+    let ee = eeff0(ur, er) * (z01(u1) / z01(ur)).powi(2);+    z01(ur) / ee.sqrt()+}++/// Centred stripline (Wheeler 1978, thickness corrected): width w between planes b apart, copper t.+fn stripline_sym(w: f64, b: f64, t: f64, er: f64) -> f64 {+    let x = t / b;+    let bt = b - t;+    let dw = if x > 0.0 {+        let n = 2.0 / (1.0 + 2.0 * x / (3.0 * (1.0 - x)));+        bt * (x / (PI * (1.0 - x))) * (1.0 - 0.5 * ((x / (2.0 - x)).powi(2) + (0.0796 * x / (w / b + 1.1 * x)).powf(n)).ln())+    } else { 0.0 };+    let m = (w + dw) / bt;+    let k = 8.0 / (PI * m);+    30.0 / er.sqrt() * (1.0 + 4.0 / (PI * m) * (k + (k * k + 6.27).sqrt())).ln()+}++/// Stripline h1 above and h2 below the track (planes h1 + t + h2 apart): Cohn's combination of the two centred cases.+pub fn stripline(w: f64, h1: f64, h2: f64, t: f64, er: f64) -> f64 {+    let za = stripline_sym(w, 2.0 * h1 + t, t, er);+    let zb = stripline_sym(w, 2.0 * h2 + t, t, er);+    2.0 * za * zb / (za + zb)+}++/// Edge-coupled differential impedance (IPC-2141): the single-ended z0, gap s, and h (microstrip) or plane spacing b+/// (stripline).+pub fn differential(z0: f64, s: f64, hb: f64, strip: bool) -> f64 {+    if strip { 2.0 * z0 * (1.0 - 0.374 * (-2.9 * s / hb).exp()) } else { 2.0 * z0 * (1.0 - 0.48 * (-0.96 * s / hb).exp()) }+}++/// The width (same unit as the geometry) where `z(w)` meets `target`; z falls as w grows. None when out of range.+fn solve(target: f64, lo: f64, hi: f64, z: impl Fn(f64) -> f64) -> Option<f64> {+    if z(lo) < target || z(hi) > target { return None; }+    let (mut a, mut b) = (lo, hi);+    for _ in 0..80 {+        let m = (a + b) / 2.0;+        if z(m) > target { a = m } else { b = m }+    }+    Some((a + b) / 2.0)+}++/// One copper layer's geometry from the stack (mm): the dielectric to the copper above and below, and their Dk.+#[derive(Debug, Clone)]+pub struct Geo { pub name: String, pub t: f64, pub above: Option<(f64, f64)>, pub below: Option<(f64, f64)> }++/// The stack summary (`layer_stack` data) as each copper layer's geometry.+pub fn geometry(stack: &Value) -> Vec<Geo> {+    let ls: Vec<Value> = stack["layers"].as_array().cloned().unwrap_or_default();+    let um = |v: &Value| v.as_f64().unwrap_or(0.0) / 1000.0;+    let diel = |l: &Value| -> Option<(f64, f64)> {+        let h = um(&l["dielectricUm"]);+        if h <= 0.0 { None } else { Some((h, l["dk1000"].as_f64().map(|d| d / 1000.0).unwrap_or(4.3))) }+    };+    (0..ls.len()).map(|i| Geo {+        name: ls[i]["name"].as_str().unwrap_or("").to_string(),+        t: um(&ls[i]["copperUm"]).max(0.0),+        above: if i > 0 { diel(&ls[i - 1]) } else { None },+        below: diel(&ls[i]),+    }).collect()+}++/// Width (and gap) for each layer, mm. `diff` is the differential target; `gap` fixes the pair gap (else gap = width).+pub fn widths(geo: &[Geo], z0: Option<f64>, diff: Option<f64>, gap: Option<f64>) -> Vec<Value> {+    geo.iter().map(|g| {+        let (strip, z): (bool, Box<dyn Fn(f64) -> f64>) = match (g.above, g.below) {+            (Some((h1, e1)), Some((h2, e2))) => {+                let er = (e1 * h1 + e2 * h2) / (h1 + h2);+                let t = g.t;+                (true, Box::new(move |w| stripline(w, h1, h2, t, er)))+            }+            (None, Some((h, er))) | (Some((h, er)), None) => { let t = g.t; (false, Box::new(move |w| microstrip(w, h, t, er))) }+            (None, None) => return json!({"layer": g.name, "error": "no dielectric next to this layer in the stack"}),+        };+        // the spacing the coupling term uses: h for microstrip, plane to plane for stripline+        let hb = match (g.above, g.below) { (Some((a, _)), Some((b, _))) => a + b, (Some((h, _)), None) | (None, Some((h, _))) => h, _ => 1.0 };+        let mut o = json!({"layer": g.name, "model": if strip { "stripline" } else { "microstrip" }, "copperUm": r1(g.t * 1000.0),+                           "dielectricMm": [g.above.map(|a| r3(a.0)), g.below.map(|b| r3(b.0))]});+        if let Some(t) = z0 {+            match solve(t, 0.01, 20.0, &z) { Some(w) => { o["width"] = json!(r3(w)); o["z0"] = json!(r1(z(w))); } None => { o["z0Error"] = json!(format!("{t} ohm is out of reach on this layer (0.01 to 20 mm)")); } }+        }+        if let Some(t) = diff {+            let zd = |w: f64| differential(z(w), gap.unwrap_or(w), hb, strip);+            match solve(t, 0.01, 20.0, zd) {+                Some(w) => { o["diffWidth"] = json!(r3(w)); o["diffGap"] = json!(r3(gap.unwrap_or(w))); o["zdiff"] = json!(r1(zd(w))); o["diffZ0"] = json!(r1(z(w))); }+                None => { o["diffError"] = json!(format!("{t} ohm differential is out of reach on this layer with that gap")); }+            }+        }+        o+    }).collect()+}++/// impedance: input {stack, args: {z0?, diff?, gapMm?, layers?, apply?: {scope, name?}}}. Needs only the stack-up.+/// `apply` answers a plan, never writes: one `add_rule` per layer (a width rule, or a diffpair rule for `diff`) scoped+/// by the caller's `scope` in the tool's own query language, at +/-10%, for the bridge to run.+pub fn impedance(input: &Value) -> Value {+    let args = &input["args"];+    let z0 = args.get("z0").and_then(|v| v.as_f64());+    let diff = args.get("diff").and_then(|v| v.as_f64());+    let z0 = if z0.is_none() && diff.is_none() { Some(50.0) } else { z0 };+    let gap = args.get("gapMm").and_then(|v| v.as_f64());+    let Some(stack) = crate::input::stack(input) else { return crate::input::refuse("no_stack", "the input has no stack: pass the layer_stack companion as stack") };+    if stack.get("ok") == Some(&json!(false)) || stack["layers"].as_array().map(|a| a.is_empty()).unwrap_or(true) {+        return crate::input::refuse("no_stack", "the stack has no layers");+    }+    let mut geo = geometry(&stack);+    // each copper layer's board model name beside the tool's own (F.Cu, In1.Cu, B.Cu)+    let board_names: Vec<String> = crate::coppermap::stack_layers(&stack).into_iter().map(|l| l.0).collect();+    let mut named: Vec<(Geo, String)> = geo.drain(..).zip(board_names).collect();+    if let Some(want) = args.get("layers").and_then(|v| v.as_array()) {+        let names: Vec<String> = want.iter().filter_map(|v| v.as_str()).map(|s| s.to_ascii_lowercase()).collect();+        named.retain(|(g, b)| names.contains(&g.name.to_ascii_lowercase()) || names.contains(&b.to_ascii_lowercase()));+    }+    let geo: Vec<Geo> = named.iter().map(|n| n.0.clone()).collect();+    let mut rows = widths(&geo, z0, diff, gap);+    for (row, (_, b)) in rows.iter_mut().zip(&named) { row["boardLayer"] = json!(b); }+    // a rigid-flex stack (the Bluetooth Sentinel example) has a coverlay a few microns thick next to a copper layer:+    // the numbers are right for that geometry and useless for a rigid board, so say which rows to doubt+    let mut warnings = Vec::new();+    for (g, row) in geo.iter().zip(&rows) {+        for d in [g.above, g.below].iter().flatten() {+            if d.0 < 0.05 { warnings.push(format!("{}: a {} mm dielectric next to it (a flex coverlay or a stack-up typo?): check the stack-up in the tool", g.name, r3(d.0))); break; }+        }+        for k in ["width", "diffWidth", "diffGap"] {+            if let Some(w) = row[k].as_f64() { if w < 0.075 { warnings.push(format!("{}: {k} {w} mm is below what most fabs make (0.075 to 0.1 mm)", g.name)); } }+        }+    }+    let mut plan = Value::Null;+    if let Some(ap) = args.get("apply").filter(|a| !a.is_null()) {+        let Some(scope) = ap.get("scope").and_then(|v| v.as_str()) else { return crate::input::refuse("bad_args", "apply.scope is the tool's query for what the rule covers (Altium: InNetClass('RF'); KiCad: A.NetClass == 'RF')") };+        let base = ap.get("name").and_then(|v| v.as_str()).unwrap_or("Impedance");+        let mut rules = Vec::new();+        for row in &rows {+            let layer = row["layer"].as_str().unwrap_or("");+            let common = json!({"name": format!("{base} {layer}"), "scope": scope, "layer": row["boardLayer"], "toolLayer": layer});+            let mut a = if diff.is_some() {+                let (Some(w), Some(s)) = (row["diffWidth"].as_f64(), row["diffGap"].as_f64()) else { continue };+                json!({"kind": "diffpair", "width": w, "gap": s, "minWidth": r3(w * 0.9), "maxWidth": r3(w * 1.1), "minGap": r3(s * 0.9), "maxGap": r3(s * 1.1)})+            } else {+                let Some(w) = row["width"].as_f64() else { continue };+                json!({"kind": "width", "min": r3(w * 0.9), "preferred": w, "max": r3(w * 1.1)})+            };+            for (k, v) in common.as_object().unwrap() { a[k] = v.clone(); }+            rules.push(a);+        }+        plan = json!({"verb": "add_rule", "rules": rules, "note": "A plan only: nothing changed. Run add_rule once per rule; each is scoped to its layer and to scope."});+    }+    json!({"success": true, "targets": {"z0": z0, "diff": diff, "gapMm": gap}, "layers": rows, "apply": plan, "warnings": warnings,+        "stack": {"copperLayers": stack["copperLayers"], "totalUm": stack["totalUm"]},+        "_hint": "Widths are for uncoated copper: solder mask lowers an outer layer's impedance by about 1 to 3 ohm. Inner layers assume planes on both neighbours. Within a few percent of a field solver; send the fab the target and let its stack-up tune it. apply:{scope} answers one width or diffpair rule per layer at +/-10% for add_rule."})+}++#[cfg(test)]+mod tests {+    use super::*;++    #[test]+    fn microstrip_matches_the_textbook_50_ohm_line() {+        // FR-4 er 4.4, 1.6 mm, 35 um: a 50 ohm line is about 3.0 mm wide (Pozar, field solvers 2.9 to 3.1)+        let w = solve(50.0, 0.01, 20.0, |w| microstrip(w, 1.6, 0.035, 4.4)).unwrap();+        assert!((2.8..3.2).contains(&w), "{w}");+    }++    #[test]+    fn stripline_matches_the_textbook_case() {+        // centred stripline, planes 1 mm apart, er 4.3, t 17 um: IPC-2141's formula puts 50 ohm near 0.40 mm+        let w = solve(50.0, 0.01, 20.0, |w| stripline(w, 0.4915, 0.4915, 0.017, 4.3)).unwrap();+        assert!((0.38..0.48).contains(&w), "{w}");+        // off centre, the nearer plane pulls the impedance down+        assert!(stripline(0.3, 0.2, 0.8, 0.017, 4.3) < stripline(0.3, 0.5, 0.5, 0.017, 4.3));+    }++    #[test]+    fn geometry_and_widths_from_a_two_layer_stack() {+        let st = json!({"layers": [{"name": "Top Layer", "copperUm": 36, "dielectricUm": 320, "dk1000": 4800}, {"name": "Bottom Layer", "copperUm": 36}]});+        let g = geometry(&st);+        assert_eq!(g.len(), 2);+        assert!(g[1].above.is_some() && g[1].below.is_none());+        let rows = widths(&g, Some(50.0), Some(90.0), None);+        let w = rows[0]["width"].as_f64().unwrap();+        assert!((0.45..0.65).contains(&w), "{w}");+        assert_eq!(rows[0]["model"], "microstrip");+        // gap = width: a 90 ohm pair's tracks come out near the 50 ohm width+        assert!((rows[0]["diffWidth"].as_f64().unwrap() - w).abs() < 0.1);+        assert!(widths(&g, None, Some(90.0), Some(0.2))[0]["diffWidth"].as_f64().unwrap() < rows[0]["diffWidth"].as_f64().unwrap());+        assert!((rows[0]["zdiff"].as_f64().unwrap() - 90.0).abs() < 0.5);+    }++    #[test]+    fn apply_is_a_plan_of_add_rule_args_on_standard_layers() {+        let input = json!({"stack": {"copperLayers": 2, "layers": [{"name": "Top Layer", "copperUm": 36, "dielectricUm": 320, "dk1000": 4800}, {"name": "Bottom Layer", "copperUm": 36}]},+                           "args": {"z0": 50, "apply": {"scope": "InNetClass('RF')"}}});+        let r = impedance(&input);+        assert_eq!(r["layers"][0]["boardLayer"], "F.Cu");+        assert_eq!(r["apply"]["verb"], "add_rule");+        let rule = &r["apply"]["rules"][1];+        assert_eq!((rule["kind"].as_str(), rule["layer"].as_str(), rule["toolLayer"].as_str()), (Some("width"), Some("B.Cu"), Some("Bottom Layer")));+        assert_eq!(rule["scope"], "InNetClass('RF')");+        // a filter by either name+        let only = impedance(&json!({"stack": input["stack"], "args": {"layers": ["B.Cu"]}}));+        assert_eq!(only["layers"].as_array().unwrap().len(), 1);+        assert_eq!(impedance(&json!({"args": {}}))["errorCode"], "no_stack");+        assert_eq!(impedance(&json!({"stack": input["stack"], "args": {"apply": {}}}))["errorCode"], "bad_args");+    }+}+