map/renderer.js

import { CELL_SIZE, MAP_H, MAP_W, clamp, valueNoise } from "./mapUtils.js";


const segmentVectorCache = new WeakMap();
const pathVectorCache = new WeakMap();
const coastlineCache = new WeakMap();
const rasterBorderCache = new WeakMap();
const baseImageCache = new WeakMap();
const MAX_BASE_CACHE_IMAGES = 4;

function mapWidth(map) {
  return Math.max(1, Math.floor(Number.isFinite(map?.width) ? map.width : MAP_W));
}

function mapHeight(map) {
  return Math.max(1, Math.floor(Number.isFinite(map?.height) ? map.height : MAP_H));
}

function cellIndex(map, x, y) {
  return y * mapWidth(map) + x;
}

function insideMap(map, x, y) {
  return x >= 0 && y >= 0 && x < mapWidth(map) && y < mapHeight(map);
}

function mapPixelWidth(map) {
  return mapWidth(map) * CELL_SIZE;
}

function mapPixelHeight(map) {
  return mapHeight(map) * CELL_SIZE;
}

function pointKey(p) {
  return `${p[0]},${p[1]}`;
}

function parsePointKey(key) {
  return key.split(",").map(Number);
}

function samePoint(a, b, eps = 1e-6) {
  return Math.abs(a[0] - b[0]) <= eps && Math.abs(a[1] - b[1]) <= eps;
}

function perpendicularDistance(p, a, b) {
  const dx = b[0] - a[0];
  const dy = b[1] - a[1];
  const len2 = dx * dx + dy * dy;
  if (len2 <= 1e-9) return Math.hypot(p[0] - a[0], p[1] - a[1]);
  const t = clamp(((p[0] - a[0]) * dx + (p[1] - a[1]) * dy) / len2, 0, 1);
  const x = a[0] + dx * t;
  const y = a[1] + dy * t;
  return Math.hypot(p[0] - x, p[1] - y);
}

function simplifyRdp(points, tolerance = 0.05) {
  if (!points || points.length <= 2) return points || [];
  let bestIndex = -1;
  let bestDistance = -1;
  const first = points[0];
  const last = points[points.length - 1];
  for (let i = 1; i < points.length - 1; i++) {
    const d = perpendicularDistance(points[i], first, last);
    if (d > bestDistance) {
      bestDistance = d;
      bestIndex = i;
    }
  }
  if (bestDistance <= tolerance) return [first, last];
  const left = simplifyRdp(points.slice(0, bestIndex + 1), tolerance);
  const right = simplifyRdp(points.slice(bestIndex), tolerance);
  return left.slice(0, -1).concat(right);
}

function removeCollinear(points) {
  if (!points || points.length <= 2) return points || [];
  const closed = samePoint(points[0], points[points.length - 1]);
  const core = closed ? points.slice(0, -1) : points.slice();
  if (core.length <= 2) return points;
  const out = [];
  const count = core.length;
  for (let i = 0; i < count; i++) {
    const prev = core[(i - 1 + count) % count];
    const cur = core[i];
    const next = core[(i + 1) % count];
    if (!closed && (i === 0 || i === count - 1)) {
      out.push(cur);
      continue;
    }
    const ax = cur[0] - prev[0];
    const ay = cur[1] - prev[1];
    const bx = next[0] - cur[0];
    const by = next[1] - cur[1];
    if (Math.abs(ax * by - ay * bx) > 1e-9) out.push(cur);
  }
  if (closed && out.length) out.push(out[0]);
  return out;
}

function chaikin(points, iterations = 1, closed = false) {
  if (!points || points.length < 3 || iterations <= 0) return points || [];
  let result = points.slice();
  for (let iter = 0; iter < iterations; iter++) {
    const src = closed && samePoint(result[0], result[result.length - 1]) ? result.slice(0, -1) : result;
    if (src.length < 3) break;
    const next = [];
    if (!closed) next.push(src[0]);
    const limit = closed ? src.length : src.length - 1;
    for (let i = 0; i < limit; i++) {
      const a = src[i];
      const b = src[(i + 1) % src.length];
      next.push([a[0] * 0.75 + b[0] * 0.25, a[1] * 0.75 + b[1] * 0.25]);
      next.push([a[0] * 0.25 + b[0] * 0.75, a[1] * 0.25 + b[1] * 0.75]);
    }
    if (!closed) next.push(src[src.length - 1]);
    if (closed && next.length) next.push(next[0]);
    result = next;
  }
  return result;
}

function traceSegmentChain(edges, adjacency, used, startKey, firstEdgeIndex) {
  const line = [parsePointKey(startKey)];
  let currentKey = startKey;
  let nextEdgeIndex = firstEdgeIndex;

  while (nextEdgeIndex !== undefined && nextEdgeIndex !== null && !used[nextEdgeIndex]) {
    used[nextEdgeIndex] = 1;
    const edge = edges[nextEdgeIndex];
    const toKey = edge.aKey === currentKey ? edge.bKey : edge.aKey;
    line.push(parsePointKey(toKey));
    currentKey = toKey;

    if (currentKey === startKey) break;
    const degree = adjacency.get(currentKey)?.length || 0;
    if (degree !== 2) break;
    nextEdgeIndex = (adjacency.get(currentKey) || []).find((idx) => !used[idx]);
  }

  return line;
}

function segmentChains(segments) {
  if (!segments?.length) return [];
  const edges = [];
  const adjacency = new Map();

  for (const seg of segments) {
    const aKey = pointKey(seg[0]);
    const bKey = pointKey(seg[1]);
    if (aKey === bKey) continue;
    const edgeIndex = edges.length;
    edges.push({ aKey, bKey });
    if (!adjacency.has(aKey)) adjacency.set(aKey, []);
    if (!adjacency.has(bKey)) adjacency.set(bKey, []);
    adjacency.get(aKey).push(edgeIndex);
    adjacency.get(bKey).push(edgeIndex);
  }

  const used = new Uint8Array(edges.length);
  const chains = [];

  for (let i = 0; i < edges.length; i++) {
    if (used[i]) continue;
    const edge = edges[i];
    const aDegree = adjacency.get(edge.aKey)?.length || 0;
    const bDegree = adjacency.get(edge.bKey)?.length || 0;
    if (aDegree === 2 && bDegree === 2) continue;
    const startKey = aDegree !== 2 ? edge.aKey : edge.bKey;
    chains.push(traceSegmentChain(edges, adjacency, used, startKey, i));
  }

  for (let i = 0; i < edges.length; i++) {
    if (used[i]) continue;
    chains.push(traceSegmentChain(edges, adjacency, used, edges[i].aKey, i));
  }

  return chains.filter((line) => line.length >= 2);
}

function vectorizeSegments(segments, { iterations = 2, tolerance = 0.08 } = {}) {
  if (!segments?.length) return [];
  const cacheKey = `${iterations}:${tolerance}`;
  let cachedByOption = segmentVectorCache.get(segments);
  if (!cachedByOption) {
    cachedByOption = new Map();
    segmentVectorCache.set(segments, cachedByOption);
  }
  if (cachedByOption.has(cacheKey)) return cachedByOption.get(cacheKey);

  const polylines = segmentChains(segments).map((line) => {
    const cleaned = removeCollinear(line);
    const closed = cleaned.length > 2 && samePoint(cleaned[0], cleaned[cleaned.length - 1]);
    const smoothed = chaikin(cleaned, iterations, closed);
    if (closed) return smoothed;
    return simplifyRdp(smoothed, tolerance);
  }).filter((line) => line.length >= 2);

  cachedByOption.set(cacheKey, polylines);
  return polylines;
}

function getCoastlineSegments(map) {
  if (!map?.sea) return [];
  const cached = coastlineCache.get(map.sea);
  if (cached) return cached;

  const segments = [];
  const w = mapWidth(map);
  const h = mapHeight(map);
  for (let y = 0; y < h; y++) {
    for (let x = 0; x < w; x++) {
      const i = cellIndex(map, x, y);
      const a = Boolean(map.sea[i]);
      if (x + 1 < w) {
        const b = Boolean(map.sea[cellIndex(map, x + 1, y)]);
        if (a !== b) segments.push([[x + 1, y], [x + 1, y + 1]]);
      }
      if (y + 1 < h) {
        const b = Boolean(map.sea[cellIndex(map, x, y + 1)]);
        if (a !== b) segments.push([[x, y + 1], [x + 1, y + 1]]);
      }
    }
  }

  coastlineCache.set(map.sea, segments);
  return segments;
}

function vectorPath(path) {
  if (!path || path.length < 2) return [];
  const cached = pathVectorCache.get(path);
  if (cached) return cached;

  const points = path.map(([x, y]) => [x * CELL_SIZE + CELL_SIZE / 2, y * CELL_SIZE + CELL_SIZE / 2]);
  // Transport routes are raster-routed, so shallow diagonal corridors can look
  // like stair steps.  Two light Chaikin passes remove that visual artifact
  // while a small RDP tolerance keeps valley and coastline bends intact.
  const smoothIterations = path.length > 12 ? 2 : path.length > 6 ? 1 : 0;
  const smoothedBase = chaikin(points, smoothIterations, false);
  const simplified = simplifyRdp(smoothedBase, CELL_SIZE * 0.10);
  pathVectorCache.set(path, simplified);
  return simplified;
}

function drawPolylinePoints(ctx, points) {
  if (!points || points.length < 2) return;
  ctx.moveTo(points[0][0], points[0][1]);
  for (let k = 1; k < points.length; k++) ctx.lineTo(points[k][0], points[k][1]);
}

function drawVectorSegments(ctx, segments, color, width, dashed = false, vectorOptions = {}) {
  const { offsetX = 0, offsetY = 0, ...shapeOptions } = vectorOptions || {};
  const polylines = vectorizeSegments(segments, shapeOptions);
  if (!polylines.length) return;
  ctx.save();
  ctx.strokeStyle = color;
  ctx.lineWidth = width;
  ctx.lineCap = "round";
  ctx.lineJoin = "round";
  if (dashed) ctx.setLineDash([6, 5]);

  for (const line of polylines) {
    ctx.beginPath();
    ctx.moveTo((line[0][0] + offsetX) * CELL_SIZE, (line[0][1] + offsetY) * CELL_SIZE);
    for (let k = 1; k < line.length; k++) ctx.lineTo((line[k][0] + offsetX) * CELL_SIZE, (line[k][1] + offsetY) * CELL_SIZE);
    ctx.stroke();
  }
  ctx.restore();
}

function sampleCellIndex(map, fx, fy) {
  const x = Math.max(0, Math.min(mapWidth(map) - 1, Math.floor(fx)));
  const y = Math.max(0, Math.min(mapHeight(map) - 1, Math.floor(fy)));
  return cellIndex(map, x, y);
}

function seaCoverageSample(map, fx, fy) {
  if (!map?.sea) return 0;
  // Coastlines are raster-derived, but the renderer should not expose the raw
  // cell stair-steps.  Sample a small footprint around each pixel and blend the
  // land/sea color at the edge; this keeps the mask stable while giving the
  // visible coastline a vector-like anti-aliased curve.
  const offsets = [
    [0, 0], [-0.34, 0], [0.34, 0], [0, -0.34], [0, 0.34],
    [-0.26, -0.26], [0.26, -0.26], [-0.26, 0.26], [0.26, 0.26],
  ];
  let sum = 0;
  for (const [ox, oy] of offsets) sum += fieldSample(map, map.sea, fx + ox, fy + oy);
  return clamp(sum / offsets.length);
}

function isWaterSample(map, fx, fy) {
  return seaCoverageSample(map, fx, fy) >= 0.50;
}

function terrainWorldPoint(map, fx, fy) {
  return {
    x: fx + (map?.worldCamera?.x || 0),
    y: fy + (map?.worldCamera?.y || 0),
  };
}

function waterVisualTone(map, fx, fy) {
  const p = terrainWorldPoint(map, fx, fy);
  const seed = (map?.seed || 0) >>> 0;
  const broad = valueNoise(p.x, p.y, seed ^ 0x5d2a9b31, 74);
  const mid = valueNoise(p.x, p.y, seed ^ 0x8f4c2d19, 29);
  return clamp(broad * 0.72 + mid * 0.28);
}

function waterVisualColor(map, fx, fy, waterCoverage = null) {
  const coverage = waterCoverage ?? seaCoverageSample(map, fx, fy);
  const tone = waterVisualTone(map, fx, fy) - 0.5;
  const offshore = clamp((coverage - 0.42) / 0.58);
  const depth = clamp(0.48 + offshore * 0.22 + tone * 0.10);
  return [
    Math.round(174 - depth * 6),
    Math.round(203 + depth * 2),
    Math.round(224 + depth * 4),
  ];
}

function waterVisualShade(map, fx, fy) {
  const tone = waterVisualTone(map, fx * 0.85 + 11.7, fy * 0.85 - 3.1) - 0.5;
  return clamp(0.992 + tone * 0.018, 0.976, 1.012);
}

function mixRgb(a, b, t) {
  return [
    Math.round(a[0] + (b[0] - a[0]) * t),
    Math.round(a[1] + (b[1] - a[1]) * t),
    Math.round(a[2] + (b[2] - a[2]) * t),
  ];
}


function distToNearest(points, x, y, fallback = 999) {
  let best = fallback;
  for (const p of points) best = Math.min(best, Math.hypot(p.x - x, p.y - y));
  return best;
}

function blendOutside(color, isInside) {
  if (isInside) return color;
  return [
    Math.round(color[0] * 0.8 + 50),
    Math.round(color[1] * 0.8 + 50),
    Math.round(color[2] * 0.8 + 50),
  ];
}

function fieldSample(map, field, fx, fy) {
  if (!field) return 0;
  const sx = Math.max(0, Math.min(mapWidth(map) - 1, fx));
  const sy = Math.max(0, Math.min(mapHeight(map) - 1, fy));
  const x0 = Math.floor(sx);
  const y0 = Math.floor(sy);
  const x1 = Math.max(0, Math.min(mapWidth(map) - 1, x0 + 1));
  const y1 = Math.max(0, Math.min(mapHeight(map) - 1, y0 + 1));
  const tx = sx - x0;
  const ty = sy - y0;

  const a = field[cellIndex(map, x0, y0)] || 0;
  const b = field[cellIndex(map, x1, y0)] || 0;
  const c = field[cellIndex(map, x0, y1)] || 0;
  const d = field[cellIndex(map, x1, y1)] || 0;

  return ((a * (1 - tx) + b * tx) * (1 - ty)) + ((c * (1 - tx) + d * tx) * ty);
}

function interpolateColorStops(value, stops) {
  if (value <= stops[0][0]) return stops[0][1].slice();
  for (let i = 1; i < stops.length; i++) {
    const [v, c] = stops[i];
    const [pv, pc] = stops[i - 1];
    if (value <= v) {
      const t = clamp((value - pv) / Math.max(0.0001, v - pv));
      return [
        Math.round(pc[0] + (c[0] - pc[0]) * t),
        Math.round(pc[1] + (c[1] - pc[1]) * t),
        Math.round(pc[2] + (c[2] - pc[2]) * t),
      ];
    }
  }
  return stops[stops.length - 1][1].slice();
}

function terrainColorContinuous(map, fx, fy, mode) {
  const i = sampleCellIndex(map, fx, fy);
  const isInside = Boolean(map.prefectureMask[i]);

  let color;

  const waterCoverage = seaCoverageSample(map, fx, fy);
  // Water must not inherit terrain DEM hill bands. Use a stable world-coordinate
  // visual water tone instead of elevation-derived depth; otherwise patched sea
  // areas expose rectangular/horizontal generation artefacts.
  const waterColor = waterVisualColor(map, fx, fy, waterCoverage);

  let landColor;
  if (mode === "development") {
    const dCity = distToNearest(map.modernCities, fx, fy);
    const urban = clamp(1 - dCity / 25);
    const density = map.populationDensity ? fieldSample(map, map.populationDensity, fx, fy) : urban;
    const base = 235;
    landColor = [
      Math.round(base + density * 20),
      Math.round(base + density * 5),
      Math.round(230 + density * 10),
    ];
  } else {
    // 地形の基底色は標高のみに従わせる。
    // 谷や微地形の見え方は陰影側で制御し、谷底だけが不自然に茶色化しないようにする。
    const e = fieldSample(map, map.elevation, fx, fy);
    landColor = interpolateColorStops(clamp(e), [
      [0.20, [231, 236, 223]],
      [0.30, [223, 231, 214]],
      [0.40, [213, 223, 201]],
      [0.50, [204, 215, 188]],
      [0.58, [195, 207, 173]],
      [0.65, [185, 196, 158]],
      [0.71, [177, 181, 141]],
      [0.76, [169, 164, 125]],
      [0.81, [157, 145, 105]],
      [0.86, [144, 128, 89]],
      [0.91, [130, 111, 79]],
      [0.95, [118, 103, 89]],
      [0.985, [146, 141, 133]],
      [1.00, [183, 179, 171]],
    ]);
  }

  const centerWater = Boolean(map.sea?.[i]);
  if (centerWater) {
    // Keep the visible coastline and the filled water side derived from the same
    // sea mask.  Only a very narrow anti-aliased edge borrows land color; broad
    // land/sea averaging made coast strokes disagree with the underlying fill.
    const edgeLand = clamp((0.58 - waterCoverage) / 0.26);
    color = edgeLand > 0 ? mixRgb(waterColor, landColor, edgeLand * 0.42) : waterColor;
  } else {
    const shore = clamp((waterCoverage - 0.10) / 0.42);
    const shoreColor = [224, 229, 213];
    color = shore > 0 ? mixRgb(landColor, shoreColor, shore * 0.34) : landColor;
  }
  return blendOutside(color, isInside);
}

function terrainShadeContinuous(map, fx, fy) {
  const i = sampleCellIndex(map, fx, fy);
  const waterCoverage = seaCoverageSample(map, fx, fy);
  if (map.sea?.[i] || waterCoverage >= 0.82) return waterVisualShade(map, fx, fy);

  const step = 0.50;
  const eC = fieldSample(map, map.elevation, fx, fy);
  const eL = fieldSample(map, map.elevation, fx - step, fy);
  const eR = fieldSample(map, map.elevation, fx + step, fy);
  const eU = fieldSample(map, map.elevation, fx, fy - step);
  const eD = fieldSample(map, map.elevation, fx, fy + step);

  // x は東向き, y は南向き。法線は (-dz/dx, -dz/dy, 1)。
  // 描画では地形生成上の差分をやや誇張し、粗いDEMでも山腹の起伏を読ませる。
  const dzdx = (eR - eL) / (step * 2);
  const dzdy = (eD - eU) / (step * 2);
  const nx = -dzdx * 4.4;
  const ny = -dzdy * 4.4;
  const nz = 1.0;
  const nLen = Math.hypot(nx, ny, nz) || 1;

  const lx = -0.5;
  const ly = -0.5;
  const lz = 0.7071067811865476;
  const hill = clamp((nx * lx + ny * ly + nz * lz) / nLen * 0.58 + 0.48);

  const slope = map.slope ? fieldSample(map, map.slope, fx, fy) : 0;
  const valley = map.valleyField ? fieldSample(map, map.valleyField, fx, fy) : 0;
  const ravine = map.visibleRavineField ? fieldSample(map, map.visibleRavineField, fx, fy) : 0;
  const tex = map.surfaceTextureField ? fieldSample(map, map.surfaceTextureField, fx, fy) : 0;
  const rvL = map.visibleRavineField ? fieldSample(map, map.visibleRavineField, fx - 0.90, fy) : 0;
  const rvR = map.visibleRavineField ? fieldSample(map, map.visibleRavineField, fx + 0.90, fy) : 0;
  const rvU = map.visibleRavineField ? fieldSample(map, map.visibleRavineField, fx, fy - 0.90) : 0;
  const rvD = map.visibleRavineField ? fieldSample(map, map.visibleRavineField, fx, fy + 0.90) : 0;
  const ravineRelief = (rvL - rvR) * 0.26 + (rvU - rvD) * 0.20;
  const concavity = clamp(((eL + eR + eU + eD) * 0.25 - eC) * 9.0, -0.18, 0.18);

  // 谷底の色保持は少し残すが、以前より圧縮を弱めて陰影の振幅を大きくする。
  const valleyFloor = clamp((valley - 0.18) * 1.45) * clamp((0.24 - slope) * 3.6);
  let shade = 0.66 + hill * 0.50 + ravineRelief - ravine * 0.12 - tex * 0.042 - concavity * 0.16 + slope * 0.030;
  if (shade < 1) shade = 1 - (1 - shade) * (1 - valleyFloor * 0.26);
  else shade = 1 + (shade - 1) * (1 - valleyFloor * 0.12);

  return clamp(shade, 0.54, 1.26);
}

function discreteColor(map, x, y, mode) {
  const i = cellIndex(map, x, y);
  let color;

  if (map.sea[i]) {
    color = [160, 205, 239];
  } else if (mode === "landuse") {
    const colors = {
      0: [244, 247, 240], // rural / natural land
      1: [222, 236, 188], // farmland
      2: [232, 222, 214], // old urban
      3: [221, 188, 184], // CBD / DID core
      4: [235, 225, 236], // suburb
      5: [223, 224, 232], // industrial
      6: [232, 237, 232], // logistics
      7: [231, 236, 246], // new town
      8: [243, 233, 210], // roadside
      9: [221, 236, 216], // forest / mountain land
    };
    color = colors[map.landuse[i]] || colors[0];
  } else if (mode === "admin") {
    const palette = [
      [250, 245, 242], [245, 250, 245], [245, 245, 252], 
      [252, 250, 242], [250, 245, 250], [242, 250, 250]
    ];
    const a = map.adminId[i];
    color = a >= 0 ? palette[a % palette.length] : [240, 242, 240];
  } else {
    color = terrainColorContinuous(map, x, y, "terrain");
  }
  return blendOutside(color, Boolean(map.prefectureMask[i]));
}

function baseCacheKey(mode, continuousTerrain, renderScale = 1) {
  const continuousModes = ["terrain", "development", "all"];
  const scaleKey = Math.round((renderScale || 1) * 20) / 20;
  if (continuousTerrain && continuousModes.includes(mode)) {
    return `continuous:${mode === "all" ? "terrain" : mode}:${scaleKey}`;
  }
  return `discrete:${mode}:${scaleKey}`;
}

function getCachedBaseCanvas(ctx, map, mode, continuousTerrain, renderScale = 1) {
  let cache = baseImageCache.get(map);
  if (!cache) {
    cache = new Map();
    baseImageCache.set(map, cache);
  }

  const key = baseCacheKey(mode, continuousTerrain, renderScale);
  let canvas = cache.get(key);
  if (canvas) return canvas;

  const sourceWidth = mapPixelWidth(map);
  const sourceHeight = mapPixelHeight(map);
  const targetScale = Math.max(0.35, Math.min(1, renderScale || 1));
  const width = Math.max(1, Math.round(sourceWidth * targetScale));
  const height = Math.max(1, Math.round(sourceHeight * targetScale));
  const img = ctx.createImageData(width, height);
  const continuousModes = ["terrain", "development", "all"];

  if (continuousTerrain && continuousModes.includes(mode)) {
    for (let py = 0; py < height; py++) {
      const fy = (py / Math.max(1, height)) * mapHeight(map);
      for (let px = 0; px < width; px++) {
        const fx = (px / Math.max(1, width)) * mapWidth(map);
        const [r, g, b] = terrainColorContinuous(map, fx, fy, mode === "all" ? "terrain" : mode);
        const shade = terrainShadeContinuous(map, fx, fy);

        const ii = (py * width + px) * 4;
        img.data[ii] = Math.round(r * shade);
        img.data[ii + 1] = Math.round(g * shade);
        img.data[ii + 2] = Math.round(b * shade);
        img.data[ii + 3] = 255;
      }
    }
  } else {
    const w = mapWidth(map);
    const h = mapHeight(map);
    for (let y = 0; y < h; y++) {
      for (let x = 0; x < w; x++) {
        const [r, g, b] = discreteColor(map, x, y, mode);
        for (let dy = 0; dy < CELL_SIZE; dy++) {
          for (let dx = 0; dx < CELL_SIZE; dx++) {
            const ii = ((y * CELL_SIZE + dy) * width + (x * CELL_SIZE + dx)) * 4;
            img.data[ii] = r;
            img.data[ii + 1] = g;
            img.data[ii + 2] = b;
            img.data[ii + 3] = 255;
          }
        }
      }
    }
  }

  canvas = document.createElement("canvas");
  canvas.width = width;
  canvas.height = height;
  const bctx = canvas.getContext("2d");
  bctx.putImageData(img, 0, 0);
  cache.set(key, canvas);
  if (cache.size > MAX_BASE_CACHE_IMAGES) cache.delete(cache.keys().next().value);
  return canvas;
}

function drawBase(ctx, map, mode, continuousTerrain, renderScale = 1) {
  // putImageData ignores the current transform, so it made the terrain layer
  // appear unzoomed while vector layers scaled.  Cache the raster into an
  // offscreen canvas and draw it with drawImage so wheel zoom applies to terrain.
  ctx.imageSmoothingEnabled = true;
  ctx.drawImage(getCachedBaseCanvas(ctx, map, mode, continuousTerrain, renderScale), 0, 0, mapPixelWidth(map), mapPixelHeight(map));
}


function getRasterBorderSegments(map, fieldName) {
  const field = map?.[fieldName];
  if (!field) return [];
  let cacheByField = rasterBorderCache.get(field);
  if (cacheByField?.segments) return cacheByField.segments;
  const segments = [];
  const w = mapWidth(map);
  const h = mapHeight(map);
  for (let y = 0; y < h; y++) {
    for (let x = 0; x < w; x++) {
      const i = cellIndex(map, x, y);
      const id = field[i];
      if (id < 0 || map.sea?.[i]) continue;
      if (x + 1 < w) {
        const ri = cellIndex(map, x + 1, y);
        const rid = field[ri];
        if (!map.sea?.[ri] && rid >= 0 && rid !== id) segments.push([[x + 0.5, y], [x + 0.5, y + 1]]);
      }
      if (y + 1 < h) {
        const di = cellIndex(map, x, y + 1);
        const did = field[di];
        if (!map.sea?.[di] && did >= 0 && did !== id) segments.push([[x, y + 0.5], [x + 1, y + 0.5]]);
      }
    }
  }
  rasterBorderCache.set(field, { segments });
  return segments;
}

function getDisplayBorderSegments(map, fieldName, precomputedSegments, mode) {
  // Raw raster borders expose every one-cell ID fragment and also reveal patch
  // ownership seams as long rectangular prefecture/municipality lines.  Keep
  // that extractor debug-only; normal modes must use prepared vector layers.
  if (mode === "borders-debug") return getRasterBorderSegments(map, fieldName);
  return Array.isArray(precomputedSegments) ? precomputedSegments : [];
}

function drawRiverPath(ctx, map, path, color, widthFn, alpha = 1) {
  if (!path || path.length < 2) return;
  ctx.save();
  ctx.lineCap = "round";
  ctx.lineJoin = "round";
  for (let k = 0; k < path.length - 1; k++) {
    const [x1, y1] = path[k];
    const [x2, y2] = path[k + 1];
    const i1 = cellIndex(map, Math.round(x1), Math.round(y1));
    const i2 = cellIndex(map, Math.round(x2), Math.round(y2));
    const strength = Math.max((map.river?.[i1] || 0) + (map.flowAccum?.[i1] || 0) * 0.95, (map.river?.[i2] || 0) + (map.flowAccum?.[i2] || 0) * 0.95);
    ctx.strokeStyle = color;
    ctx.globalAlpha = alpha;
    ctx.lineWidth = widthFn(strength, k / Math.max(1, path.length - 1));
    ctx.beginPath();
    ctx.moveTo(x1 * CELL_SIZE + CELL_SIZE / 2, y1 * CELL_SIZE + CELL_SIZE / 2);
    ctx.lineTo(x2 * CELL_SIZE + CELL_SIZE / 2, y2 * CELL_SIZE + CELL_SIZE / 2);
    ctx.stroke();
  }
  ctx.restore();
}

function drawPath(ctx, path, color, width, dashed = false) {
  const points = vectorPath(path);
  if (points.length < 2) return;
  ctx.save();
  ctx.lineCap = "round";
  ctx.lineJoin = "round";
  ctx.strokeStyle = color;
  ctx.lineWidth = width;
  if (dashed) ctx.setLineDash([8, 6]);
  ctx.beginPath();
  drawPolylinePoints(ctx, points);
  ctx.stroke();
  ctx.restore();
}

function landOnlySubpaths(map, path, minCells = 2) {
  if (!path || path.length < 2 || !map?.sea) return path?.length >= minCells ? [path] : [];
  const chunks = [];
  let cur = [];
  for (const p of path) {
    const [x, y] = p;
    const land = insideMap(map, x, y) && !map.sea[cellIndex(map, x, y)];
    if (land) {
      cur.push(p);
    } else if (cur.length >= minCells) {
      chunks.push(cur);
      cur = [];
    } else {
      cur = [];
    }
  }
  if (cur.length >= minCells) chunks.push(cur);
  return chunks;
}

function drawLandPath(ctx, map, path, color, width, dashed = false, minCells = 2) {
  for (const chunk of landOnlySubpaths(map, path, minCells)) drawPath(ctx, chunk, color, width, dashed);
}

// 魚の骨（私鉄記号）スタイルを描画するための専用関数
function drawRailway(ctx, path, color, lineWidth, tickLen, spacing) {
  const points = vectorPath(path);
  if (points.length < 2) return;
  ctx.save();
  ctx.lineCap = "butt";
  ctx.lineJoin = "round";
  ctx.strokeStyle = color;

  // 中心の実線を描画
  ctx.lineWidth = lineWidth;
  ctx.beginPath();
  drawPolylinePoints(ctx, points);
  ctx.stroke();

  // 棘（クロスハッチ）を描画
  ctx.lineWidth = 1.0;
  ctx.beginPath();
  let carry = spacing * 0.5;
  for (let k = 0; k < points.length - 1; k++) {
    const [x1, y1] = points[k];
    const [x2, y2] = points[k + 1];
    const dx = x2 - x1;
    const dy = y2 - y1;
    const dist = Math.hypot(dx, dy);
    if (dist <= 0.001) continue;

    const nx = dx / dist;
    const ny = dy / dist;
    const px = -ny * (tickLen / 2);
    const py = nx * (tickLen / 2);

    let d = carry;
    while (d < dist) {
      const cx = x1 + nx * d;
      const cy = y1 + ny * d;
      ctx.moveTo(cx + px, cy + py);
      ctx.lineTo(cx - px, cy - py);
      d += spacing;
    }
    carry = d - dist;
  }
  ctx.stroke();
  ctx.restore();
}

function drawLandRailway(ctx, map, path, color, lineWidth, tickLen, spacing) {
  for (const chunk of landOnlySubpaths(map, path, 3)) drawRailway(ctx, chunk, color, lineWidth, tickLen, spacing);
}

function drawSegments(ctx, segments, color, width, dashed = false) {
  ctx.save();
  ctx.strokeStyle = color;
  ctx.lineWidth = width;
  ctx.lineCap = "round";
  ctx.lineJoin = "round";
  if (dashed) ctx.setLineDash([6, 5]);

  for (const seg of segments) {
    ctx.beginPath();
    ctx.moveTo(seg[0][0] * CELL_SIZE, seg[0][1] * CELL_SIZE);
    ctx.lineTo(seg[1][0] * CELL_SIZE, seg[1][1] * CELL_SIZE);
    ctx.stroke();
  }
  ctx.restore();
}

function drawUrbanAreas(ctx, map, mode) {
  const visibleModes = ["all", "modern", "development", "landuse", "admin"];
  if (!visibleModes.includes(mode)) return;

  const detailedColors = {
    2: "rgba(223, 214, 206, 0.72)",
    3: "rgba(215, 175, 172, 0.88)",
    4: "rgba(231, 219, 231, 0.68)",
    5: "rgba(218, 218, 226, 0.64)",
    6: "rgba(225, 230, 225, 0.56)",
    7: "rgba(229, 234, 242, 0.64)",
    8: "rgba(231, 219, 231, 0.68)",
  };
  const cityColor = "rgba(232, 222, 228, 0.60)";
  const cbdColor = "rgba(215, 175, 172, 0.84)";

  ctx.save();
  const w = mapWidth(map);
  const h = mapHeight(map);
  for (let y = 0; y < h; y++) {
    for (let x = 0; x < w; x++) {
      const i = cellIndex(map, x, y);
      const areaMask = map.humanRegionMask || map.prefectureMask;
      if (areaMask && !areaMask[i]) continue;
      const lu = map.landuse[i];
      let fill = null;
      if (mode === "landuse") fill = detailedColors[lu] || null;
      else if (lu === 3) fill = cbdColor;
      else if (lu === 2 || lu === 4 || lu === 5 || lu === 6 || lu === 7 || lu === 8) fill = cityColor;
      if (!fill) continue;

      const px = x * CELL_SIZE;
      const py = y * CELL_SIZE;
      ctx.fillStyle = fill;
      ctx.fillRect(px, py, CELL_SIZE, CELL_SIZE);
    }
  }
  ctx.restore();
}

function drawDebugCells(ctx, map, field, color) {
  if (!field) return;
  ctx.save();
  const w = mapWidth(map);
  const h = mapHeight(map);
  for (let y = 0; y < h; y++) {
    for (let x = 0; x < w; x++) {
      const i = cellIndex(map, x, y);
      const debugMask = map.humanRegionMask || map.prefectureMask;
      if (!debugMask[i] || map.sea[i]) continue;
      const raw = field[i] || 0;
      const v = clamp(raw > 1 ? raw / 255 : raw, 0, 1);
      if (v <= 0.12) continue;
      ctx.fillStyle = color(v);
      ctx.fillRect(x * CELL_SIZE, y * CELL_SIZE, CELL_SIZE, CELL_SIZE);
    }
  }
  ctx.restore();
}

function drawTransportDebug(ctx, map) {
  const layers = map.transportDebug?.layers;
  if (!layers) return;
  drawDebugCells(ctx, map, layers.expresswayPotential, (v) => v < 0.16 ? "rgba(0,0,0,0)" : `rgba(80, 190, 110, ${0.035 + v * 0.13})`);
  drawDebugCells(ctx, map, layers.railPotential, (v) => v < 0.16 ? "rgba(0,0,0,0)" : `rgba(70, 120, 230, ${0.035 + v * 0.13})`);
  drawDebugCells(ctx, map, layers.nationalRoadPotential, (v) => v < 0.16 ? "rgba(0,0,0,0)" : `rgba(245, 205, 65, ${0.030 + v * 0.12})`);
  drawDebugCells(ctx, map, layers.slopeSeaPenalty, (v) => v < 0.45 ? "rgba(0,0,0,0)" : `rgba(80, 30, 30, ${0.025 + v * 0.10})`);

  const componentColors = {
    expressway: "rgba(60, 165, 80, 0.42)",
    rail: "rgba(65, 95, 210, 0.42)",
    national: "rgba(210, 155, 20, 0.42)",
  };
  ctx.save();
  for (const comp of layers.components || []) {
    ctx.fillStyle = componentColors[comp.mode] || "rgba(150,150,150,0.35)";
    for (const [x, y] of comp.cells || []) ctx.fillRect(x * CELL_SIZE, y * CELL_SIZE, CELL_SIZE, CELL_SIZE);
  }
  ctx.restore();

  for (const repair of layers.repairedSegments || []) {
    const color = repair.mode === "expressway" ? "rgba(0, 115, 40, 0.95)"
      : repair.mode === "rail" ? "rgba(35, 70, 210, 0.95)"
      : repair.mode === "national" ? "rgba(180, 120, 0, 0.95)"
      : "rgba(210, 35, 155, 0.92)";
    drawPath(ctx, repair.path, "rgba(255,255,255,0.92)", 5.0);
    drawPath(ctx, repair.path, color, 2.4);
  }
}

function prefectureRegionColor(id) {
  const palette = [
    [234, 220, 214], [218, 232, 218], [218, 224, 238], [238, 232, 208],
    [232, 218, 232], [214, 232, 234], [235, 224, 216], [222, 236, 210],
  ];
  return palette[Math.abs(id) % palette.length];
}

function drawPrefectureRegionFill(ctx, map, mode) {
  if (!["all", "admin", "borders-debug"].includes(mode)) return;
  const ids = map.prefectureRegionId;
  if (!ids) return;
  const alpha = mode === "borders-debug" ? 0.34 : 0.18;
  ctx.save();
  ctx.globalAlpha = alpha;
  const w = mapWidth(map);
  const h = mapHeight(map);
  for (let y = 0; y < h; y++) {
    for (let x = 0; x < w; x++) {
      const i = cellIndex(map, x, y);
      const id = ids[i];
      if (map.sea[i] || id < 0) continue;
      const [r, g, b] = prefectureRegionColor(id);
      ctx.fillStyle = `rgb(${r}, ${g}, ${b})`;
      ctx.fillRect(x * CELL_SIZE, y * CELL_SIZE, CELL_SIZE, CELL_SIZE);
    }
  }
  ctx.restore();
}

function dot(ctx, p, radius, fill, stroke = "white") {
  ctx.beginPath();
  ctx.arc(p.x * CELL_SIZE + CELL_SIZE / 2, p.y * CELL_SIZE + CELL_SIZE / 2, radius, 0, Math.PI * 2);
  ctx.fillStyle = fill;
  ctx.fill();
  ctx.lineWidth = 1.2;
  ctx.strokeStyle = stroke;
  ctx.stroke();
}

function boxesOverlap(a, b, pad = 3) {
  return !(a.x2 + pad < b.x1 || a.x1 - pad > b.x2 || a.y2 + pad < b.y1 || a.y1 - pad > b.y2);
}

function labelWithCollision(ctx, p, occupied) {
  if (!p.name) return false;
  const isPrefectureLabel = p.kind === "Prefecture" || p.kind === "Current Prefecture" || p.isPrefectureLabel;
  const isMunicipalityLabel = p.labelStyle === "municipality";
  ctx.save();
  ctx.font = isPrefectureLabel
    ? "900 20px ui-sans-serif, system-ui, -apple-system, sans-serif"
    : isMunicipalityLabel
      ? "600 10px ui-sans-serif, system-ui, -apple-system, sans-serif"
      : "600 11.5px ui-sans-serif, system-ui, -apple-system, sans-serif";
  const baseX = p.x * CELL_SIZE + CELL_SIZE / 2;
  const baseY = p.y * CELL_SIZE + CELL_SIZE / 2;
  const textW = ctx.measureText(p.name).width;
  const textH = isPrefectureLabel ? 22 : isMunicipalityLabel ? 10 : 12;
  const candidates = isPrefectureLabel
    ? [
        [-textW / 2, 6], [-textW / 2, -12], [-textW / 2, 24],
        [10, 6], [-textW - 10, 6],
      ]
    : isMunicipalityLabel
      ? [
          [6, -4], [6, 11], [-textW - 6, -4], [-textW - 6, 11],
          [-textW / 2, -10], [-textW / 2, 17], [10, 3], [-textW - 10, 3],
          [4, -12], [-textW - 4, -12], [4, 18], [-textW - 4, 18],
        ]
      : [
          [7, -4], [7, 13], [-textW - 7, -4], [-textW - 7, 13],
          [-textW / 2, -12], [-textW / 2, 20], [12, 4], [-textW - 12, 4],
        ];

  let fallback = null;
  for (const [ox, oy] of candidates) {
    const x = baseX + ox;
    const y = baseY + oy;
    const box = { x1: x - 3, y1: y - textH, x2: x + textW + 3, y2: y + 5 };
    if (box.x1 < 0 || box.y1 < 0 || box.x2 > (ctx.__mapPixelWidth || MAP_W * CELL_SIZE) || box.y2 > (ctx.__mapPixelHeight || MAP_H * CELL_SIZE)) continue;
    const overlaps = occupied.filter((b) => boxesOverlap(box, b, isPrefectureLabel ? 5 : isMunicipalityLabel ? 1 : 3));
    if (!overlaps.length) {
      ctx.lineJoin = "round";
      ctx.lineWidth = isPrefectureLabel ? 6.2 : isMunicipalityLabel ? 3.0 : 3.5;
      ctx.strokeStyle = isPrefectureLabel ? "rgba(255, 255, 255, 0.98)" : "rgba(255, 255, 255, 0.95)";
      ctx.strokeText(p.name, x, y);
      ctx.fillStyle = isPrefectureLabel ? "rgba(62, 38, 112, 0.98)" : p.isPrefecturalCapital ? "#111111" : isMunicipalityLabel ? "rgba(72, 62, 82, 0.92)" : "#333333";
      ctx.fillText(p.name, x, y);
      occupied.push(box);
      ctx.restore();
      return true;
    }
    if (p.forceLabel) {
      const score = overlaps.length;
      if (!fallback || score < fallback.score) fallback = { x, y, box, score };
    }
  }
  if (p.forceLabel && fallback) {
    ctx.lineJoin = "round";
    ctx.lineWidth = isPrefectureLabel ? 6.2 : isMunicipalityLabel ? 3.0 : 3.5;
    ctx.strokeStyle = isPrefectureLabel ? "rgba(255, 255, 255, 0.98)" : "rgba(255, 255, 255, 0.95)";
    ctx.strokeText(p.name, fallback.x, fallback.y);
    ctx.fillStyle = isPrefectureLabel ? "rgba(62, 38, 112, 0.98)" : p.isPrefecturalCapital ? "#111111" : isMunicipalityLabel ? "rgba(72, 62, 82, 0.92)" : "#333333";
    ctx.fillText(p.name, fallback.x, fallback.y);
    occupied.push(fallback.box);
    ctx.restore();
    return true;
  }
  ctx.restore();
  return false;
}

function drawLabels(ctx, points, limit = Infinity, occupied = null) {
  const used = occupied || [];
  const prioritized = points
    .filter((p) => p?.name)
    .map((p) => ({ ...p, labelPriority: (p.labelPriorityBase || 0) + (p.isPrefecturalCapital ? 1000 : 0) + (p.population || 0) / 900 + (p.portClass === "major" ? 170 : p.portClass === "regional" ? 95 : 0) }))
    .sort((a, b) => b.labelPriority - a.labelPriority);
  for (const p of prioritized.slice(0, limit)) labelWithCollision(ctx, p, used);
  return used;
}

function drawScaleBar(ctx, cellScreenSize = CELL_SIZE) {
  const kmPerCell = 0.5;
  const targetKm = 25;
  const lengthCells = Math.max(8, Math.round(targetKm / kmPerCell));
  const lengthPx = lengthCells * cellScreenSize;
  const margin = 14;
  const x = margin;
  const y = margin + 18;

  ctx.save();
  ctx.lineCap = "butt";
  ctx.strokeStyle = "rgba(0,0,0,0.78)";
  ctx.lineWidth = 2.2;
  ctx.fillStyle = "rgba(255,255,255,0.92)";
  ctx.fillRect(x - 8, y - 18, lengthPx + 16, 30);
  ctx.strokeStyle = "rgba(80,80,80,0.22)";
  ctx.strokeRect(x - 8, y - 18, lengthPx + 16, 30);
  ctx.strokeStyle = "rgba(30,30,30,0.82)";
  ctx.beginPath();
  ctx.moveTo(x, y);
  ctx.lineTo(x + lengthPx, y);
  ctx.stroke();
  for (let t = 0; t <= 2; t++) {
    const tx = x + (lengthPx * t) / 2;
    ctx.beginPath();
    ctx.moveTo(tx, y - 5);
    ctx.lineTo(tx, y + 5);
    ctx.stroke();
  }
  ctx.fillStyle = "rgba(20,20,20,0.88)";
  ctx.font = "600 11px ui-sans-serif, system-ui, -apple-system, sans-serif";
  ctx.textAlign = "center";
  ctx.fillText(`${targetKm} km`, x + lengthPx / 2, y - 7);
  ctx.restore();
}

export function drawMap(canvas, map, options) {
  const ctx = canvas.getContext("2d");
  if (!ctx) return;

  const mode = options.mode || "all";
  const showFeatures = options.showFeatures !== false;
  const showLabels = options.showLabels !== false;
  const continuousTerrain = options.continuousTerrain !== false;
  const outputWidth = MAP_W * CELL_SIZE;
  const outputHeight = MAP_H * CELL_SIZE;
  const sourceWidth = mapPixelWidth(map);
  const sourceHeight = mapPixelHeight(map);
  const drawScale = Math.min(outputWidth / Math.max(1, sourceWidth), outputHeight / Math.max(1, sourceHeight));
  const drawOffsetX = (outputWidth - sourceWidth * drawScale) * 0.5;
  const drawOffsetY = (outputHeight - sourceHeight * drawScale) * 0.5;
  const cellScreenSize = CELL_SIZE * drawScale;
  const terrainRenderScale = continuousTerrain ? clamp(drawScale * (options.fastTerrain ? 0.48 : 1.35), 0.30, 1) : 1;

  if (canvas.width !== outputWidth) canvas.width = outputWidth;
  if (canvas.height !== outputHeight) canvas.height = outputHeight;
  ctx.clearRect(0, 0, outputWidth, outputHeight);
  ctx.save();
  ctx.translate(drawOffsetX, drawOffsetY);
  ctx.scale(drawScale, drawScale);
  ctx.__mapPixelWidth = sourceWidth;
  ctx.__mapPixelHeight = sourceHeight;
  const finish = () => {
    ctx.restore();
    drawScaleBar(ctx, cellScreenSize);
    delete ctx.__mapPixelWidth;
    delete ctx.__mapPixelHeight;
  };

  // 1. Base Terrain & Urban
  drawBase(ctx, map, mode, continuousTerrain, terrainRenderScale);
  drawUrbanAreas(ctx, map, mode);
  const coastSegments = getCoastlineSegments(map);
  drawVectorSegments(ctx, coastSegments, "rgba(120, 175, 210, 0.22)", 2.2, false, { iterations: 2, tolerance: 0.06, offsetX: -0.5, offsetY: -0.5 });
  drawVectorSegments(ctx, coastSegments, "rgba(248, 250, 242, 0.68)", 1.1, false, { iterations: 2, tolerance: 0.06, offsetX: -0.5, offsetY: -0.5 });

  // 2. Rivers
  const waterBlue = "rgba(116, 165, 202, 0.92)";
  const mediumBlue = "rgba(132, 184, 220, 0.78)";
  const riverStrengthForPath = (path) => {
    if (!path || path.length === 0) return 0;
    let peak = 0;
    let tail = 0;
    const tailStart = Math.max(0, path.length - Math.min(path.length, 8));
    let tailCount = 0;
    for (let k = 0; k < path.length; k++) {
      const [x, y] = path[k];
      const i = cellIndex(map, Math.round(x), Math.round(y));
      const strength = (map.river?.[i] || 0) + (map.flowAccum?.[i] || 0) * 0.75;
      peak = Math.max(peak, strength);
      if (k >= tailStart) {
        tail += strength;
        tailCount++;
      }
    }
    return Math.max(peak, tail / Math.max(1, tailCount));
  };
  // Draw a dendritic river network.  Width is intentionally separated by
  // river order: small streams are hairline/low-alpha, tributaries are thin,
  // and only trunk rivers get a modestly wider stroke.
  for (const path of map.smallStreams || []) {
    const strength = riverStrengthForPath(path);
    if ((path?.length || 0) < 5 || strength < 0.045) continue;
    drawRiverPath(ctx, map, path, "rgba(140, 190, 224, 0.82)", (s) => s > 0.45 ? 0.52 : s > 0.22 ? 0.42 : 0.32, 0.28);
  }
  for (const path of map.tributaryRivers || []) {
    const strength = riverStrengthForPath(path);
    if ((path?.length || 0) < 9 || strength < 0.45) continue;
    drawRiverPath(ctx, map, path, mediumBlue, (s, t) => {
      const downstreamBoost = 0.92 + t * 0.18;
      if (s > 1.65) return 1.35 * downstreamBoost;
      if (s > 0.95) return 1.12 * downstreamBoost;
      return 0.94 * downstreamBoost;
    }, 0.92);
  }
  for (const path of map.mainRivers || []) {
    const strength = riverStrengthForPath(path);
    if ((path?.length || 0) < 9) continue;
    drawRiverPath(ctx, map, path, waterBlue, (s, t) => {
      const downstreamBoost = 0.96 + t * 0.24;
      if (s > 2.35) return 2.15 * downstreamBoost;
      if (s > 1.45) return 1.86 * downstreamBoost;
      return 1.55 * downstreamBoost;
    }, 1.0);
  }

  const showHistory = mode === "history";
  const showTransportDebug = mode === "transport-debug";
  const showModern = ["modern", "all", "development", "landuse", "borders-debug", "transport-debug"].includes(mode);
  const showRoads = ["all", "development", "transport-debug"].includes(mode);
  const showMinorRoads = ["all", "modern", "development", "transport-debug"].includes(mode);
  const showPremodernRoads = ["history", "all", "transport-debug"].includes(mode);
  const showAdmin = ["admin", "all", "borders-debug"].includes(mode);

  // 3. Borders
  const showPrefectureRegions = ["all", "admin", "borders-debug"].includes(mode);
  if (showPrefectureRegions) drawPrefectureRegionFill(ctx, map, mode);

  const adminBorderSegments = getDisplayBorderSegments(map, "adminId", map.adminBorders, mode);
  const prefectureBorderSegments = getDisplayBorderSegments(map, "prefectureRegionId", map.regionalPrefectureBorders, mode);
  if (showAdmin && adminBorderSegments?.length) {
    drawVectorSegments(ctx, adminBorderSegments, "rgba(255, 255, 255, 0.8)", 2.8, false, { iterations: 1, tolerance: 0.05, offsetX: -0.5, offsetY: -0.5 }); 
    drawVectorSegments(ctx, adminBorderSegments, "rgba(150, 140, 150, 0.9)", 1.2, true, { iterations: 1, tolerance: 0.05, offsetX: -0.5, offsetY: -0.5 }); 
  }
  if (mode === "borders-debug") {
    // Keep the natural barrier heatmap subtle. A dense cell fill can look like
    // artificial horizontal hatching, so only strong terrain dividers are shown.
    drawDebugCells(ctx, map, map.naturalBarrierScore, (v) => v < 0.42 ? "rgba(0,0,0,0)" : `rgba(255, 120, 40, ${0.025 + v * 0.075})`);
    if (map.adminDebug?.compartmentBorders) drawSegments(ctx, map.adminDebug.compartmentBorders, "rgba(45, 95, 160, 0.72)", 1.0, true);
    for (const p of map.adminDebug?.lowlandAdminSeeds || []) dot(ctx, p, 3.2, "rgba(255,255,255,0.9)", "rgba(40,150,95,0.95)");
  }
  if (showTransportDebug) drawTransportDebug(ctx, map);

  if (showPrefectureRegions && prefectureBorderSegments?.length) {
    drawVectorSegments(ctx, prefectureBorderSegments, "rgba(255, 255, 255, 0.90)", 4.2, false, { iterations: 2, tolerance: 0.06, offsetX: -0.5, offsetY: -0.5 });
    drawVectorSegments(ctx, prefectureBorderSegments, "rgba(82, 60, 102, 0.96)", 1.8, true, { iterations: 2, tolerance: 0.06, offsetX: -0.5, offsetY: -0.5 });
  }

  if (!showPrefectureRegions) {
    const finalPrefectureBorders = (prefectureBorderSegments && prefectureBorderSegments.length) ? prefectureBorderSegments : map.prefectureBorder;
    drawVectorSegments(ctx, finalPrefectureBorders, "rgba(255, 255, 255, 0.95)", 5.0, false, { iterations: 2, tolerance: 0.06, offsetX: -0.5, offsetY: -0.5 });
    drawVectorSegments(ctx, finalPrefectureBorders, "rgba(110, 90, 110, 1)", 2.2, true, { iterations: 2, tolerance: 0.06, offsetX: -0.5, offsetY: -0.5 });
  }

  if (!showFeatures) {
    finish();
    return;
  }

  // 4. Transport casings. Layer order: local roads, trunk roads, railways, expressways.
  const localRoadCasing = "rgba(112, 112, 104, 0.58)";
  const localRoadFill = "rgba(255, 255, 255, 0.98)";
  const generalRoadPaths = [
    ...(showPremodernRoads ? (map.premodernRoads || []) : []),
    ...(showMinorRoads ? (map.minorRoads || []) : []),
  ];
  if (generalRoadPaths.length) {
    // Ordinary roads: white centerline with a restrained grey casing.  Both the
    // current generated local roads and premodernRoads use the same appearance
    // in all / transport-debug so the old white layer no longer reads as a
    // second road system.
    for (const path of generalRoadPaths) drawLandPath(ctx, map, path, localRoadCasing, 3.05);
  }
  if (showRoads) {
    for (const path of map.nationalRoads) drawLandPath(ctx, map, path, "rgba(190, 175, 140, 1)", 3.8);
    for (const path of map.ringRoads || []) drawLandPath(ctx, map, path, "rgba(190, 175, 140, 1)", 3.8);
    for (const path of map.externalRoads) drawLandPath(ctx, map, path, "rgba(190, 175, 140, 1)", 3.8);
  }
  if (showModern || showRoads) {
    for (const path of map.railways) drawLandPath(ctx, map, path, "rgba(255, 255, 255, 0.78)", 3.6, false, 3);
    for (const path of map.branchRailways) drawLandPath(ctx, map, path, "rgba(255, 255, 255, 0.64)", 2.6, false, 3);
    for (const path of map.externalRailways) drawLandPath(ctx, map, path, "rgba(255, 255, 255, 0.78)", 3.6, false, 3);
  }
  if (showRoads) {
    for (const path of map.expressways) drawPath(ctx, path, "rgba(105, 125, 105, 0.78)", 4.6);
    for (const path of map.externalExpressways) drawPath(ctx, path, "rgba(105, 125, 105, 0.78)", 4.6);
  }

  // 5. Transport fills. Expressways remain above railways; railways sit above ordinary roads.
  if (generalRoadPaths.length) {
    for (const path of generalRoadPaths) drawLandPath(ctx, map, path, localRoadFill, 1.45, false);
  }
  if (showRoads) {
    for (const path of map.nationalRoads) drawLandPath(ctx, map, path, "rgba(245, 225, 130, 1)", 2.0);
    for (const path of map.ringRoads || []) drawLandPath(ctx, map, path, "rgba(245, 225, 130, 1)", 2.0);
    for (const path of map.externalRoads) drawLandPath(ctx, map, path, "rgba(245, 225, 130, 1)", 2.0);
  }
  if (showModern || showRoads) {
    for (const path of map.railways) drawLandRailway(ctx, map, path, "rgba(95, 95, 95, 1)", 1.55, 5.0, 7.0);
    for (const path of map.branchRailways) drawLandRailway(ctx, map, path, "rgba(125, 125, 125, 1)", 1.05, 4.0, 6.0);
    for (const path of map.externalRailways) drawLandRailway(ctx, map, path, "rgba(95, 95, 95, 1)", 1.55, 5.0, 7.0);
  }
  if (showRoads) {
    for (const path of map.expressways) drawPath(ctx, path, "rgba(135, 160, 135, 0.88)", 2.4);
    for (const path of map.externalExpressways) drawPath(ctx, path, "rgba(135, 160, 135, 0.88)", 2.4);
  }

  // 6. Icons & Labels
  if (["admin", "borders-debug"].includes(mode)) {
    for (const p of map.adminCenters || []) dot(ctx, p, 2.8, "rgba(255,255,255,0.96)", "rgba(75,60,90,0.95)");
  }

  const settlementIconLabelPoints = ["all", "modern", "history"].includes(mode)
    ? [
        ...(map.markets || []).filter((p) => (p.population || 0) >= 3000),
        ...(map.villages || []).filter((p) => (p.population || 0) >= 3000),
        ...(mode === "history" ? (map.ports || []).filter((p) => p.portClass === "major" || p.portClass === "regional") : []),
        ...(mode === "history" ? (map.castles || []) : []),
      ].filter((p) => !(map.modernCities || []).some((c) => c.x === p.x && c.y === p.y))
       .map((p) => ({ ...p, forceAllLayerTownLabel: true, labelPriorityBase: p.labelPriorityBase || (p.kind === "Village" ? 58 : p.kind === "Castle" ? 88 : 66) }))
    : [];

  if (["all", "modern", "history"].includes(mode)) {
    for (const p of settlementIconLabelPoints) dot(ctx, p, p.kind === "Castle" ? 3.2 : 3.1, "rgba(240, 110, 110, 0.95)", "rgba(255,255,255,0.88)");
  }

  if (showModern) {
    for (const p of map.stations) dot(ctx, p, 2.5, "#fff", "#444");
    for (const p of map.modernCities) {
      const popRadius = p.population ? Math.min(9.4, 3.8 + Math.sqrt(p.population) / 360) : 4.8;
      dot(ctx, p, popRadius, "rgba(240, 110, 110, 0.95)", "rgba(255,255,255,0.9)");
      if (p.isPrefecturalCapital) dot(ctx, p, popRadius + 3.4, "transparent", "rgba(200,80,80,0.9)");
      else if (p.isRegionalCapital) dot(ctx, p, popRadius + 2.4, "transparent", "rgba(190,95,95,0.62)");
    }
    for (const p of map.interchanges || []) dot(ctx, p, 2.7, "rgba(250, 250, 245, 0.95)", "rgba(95, 125, 95, 0.95)");
    for (const p of map.logisticsParks || []) dot(ctx, p, 2.4, "rgba(235, 238, 230, 0.95)", "rgba(105, 125, 105, 0.88)");
    if (mode === "borders-debug") {
      for (const p of map.externalGateways || []) dot(ctx, p, 5.5, "rgba(255,255,255,0.95)", "rgba(40,80,170,0.95)");
      for (const p of map.transportDebug?.missingRequiredNodes || []) dot(ctx, p, 6.5, "rgba(255,80,80,0.95)", "rgba(80,20,20,0.95)");
    }
    if (showTransportDebug) {
      for (const p of map.transportDebug?.layers?.unservedSettlements || []) {
        dot(ctx, p, p.repaired ? 3.4 : 4.8, p.repaired ? "rgba(255,255,255,0.92)" : "rgba(255,80,140,0.95)", "rgba(125,35,105,0.95)");
      }
    }
  }

  if (showLabels) {
    const prefectureLabels = (map.prefectureRegions || []).map((p) => ({ ...p, isPrefectureLabel: true, forceLabel: true, labelPriorityBase: p.labelPriorityBase || 1900 }));
    if (mode === "admin") {
      const municipalLabels = (map.adminCenters || [])
        .filter((p) => p && p.name && Number.isFinite(p.x) && Number.isFinite(p.y) && p.x >= 0 && p.y >= 0 && p.x < map.width && p.y < map.height && map.adminId?.[Math.round(p.y) * map.width + Math.round(p.x)] === (p.adminId ?? p.municipalityId ?? p.adminNumericId))
        .map((p) => ({ ...p, labelStyle: "municipality", forceLabel: true, labelPriorityBase: 1200 }));
      drawLabels(ctx, [...prefectureLabels, ...municipalLabels], Infinity);
      finish();
      return;
    }
    if (mode === "borders-debug") {
      drawLabels(ctx, prefectureLabels, Infinity);
      finish();
      return;
    }
    const important = [
      ...prefectureLabels,
      ...map.modernCities,
      ...map.ports,
      ...(map.satelliteCities || []),
      ...settlementIconLabelPoints,
    ].filter((p) => !p.suppressSettlementLabel && (p.isPrefectureLabel || p.forceAllLayerTownLabel || p.insidePrefecture || p.isRegionalCapital || p.kind === "External Gateway" || (p.population || 0) >= 5000));
    drawLabels(ctx, important, mode === "all" || mode === "history" ? 78 : 60);
  }
  finish();
}