import {
  applyLandscapeUnitAdminPartition,
  assignAdminRegionsFromNaturalCompartments,
  lockSmallUrbanComponentsToMunicipality,
  mergeTinyMunicipalities,
  removeMunicipalExclaves,
  smoothAdminRegionsTerrainAware,
  splitOversizedLowlandMunicipalities,
  snapAdminBoundariesToTerrain,
} from "./adminRegions.js";
import { INF, MAP_H, MAP_W, SIZE, MinHeap, clamp, hash2, indexOf, inside, pickEntities, rand, xyOf } from "./mapUtils.js";
import { extractAdminBorderSegments } from "./mapGeneratorHelpers.js";

const OUTER_ANCHOR_REGION_ID = -2;

function adminGenerationRegionIdAt(i, prefectureMask, prefectureRegionId) {
  if (prefectureMask[i]) return 0;
  const regionalId = prefectureRegionId?.[i] ?? -1;
  if (regionalId === 0) return OUTER_ANCHOR_REGION_ID;
  return regionalId;
}

function changedCellsSince(before, after, prefectureMask, sea) {
  let changed = 0;
  for (let i = 0; i < SIZE; i++) if (prefectureMask[i] && !sea[i] && before[i] !== after[i]) changed++;
  return changed;
}

function municipalityAreaById(adminId, prefectureMask, sea) {
  const area = new Map();
  for (let i = 0; i < SIZE; i++) {
    if (!prefectureMask[i] || sea[i] || adminId[i] < 0) continue;
    area.set(adminId[i], (area.get(adminId[i]) || 0) + 1);
  }
  return area;
}

function isProtectedAdminSeed(seed) {
  if (!seed) return false;
  if (seed.seedKind === "capital" || seed.protectedCity?.isPrefecturalCapital) return true;
  if (seed.seedKind === "modernCity" && (seed.protectedCity?.population || seed.population || 0) >= 180000) return true;
  if (seed.seedKind === "port" && seed.portClass === "major") return true;
  if (seed.seedKind === "satelliteCity" && (seed.protectedSatellite?.population || seed.population || 0) >= 60000) return true;
  return false;
}

function buildSeedLifecycle(adminCenters, adminId, prefectureMask, sea, minArea = 80) {
  const areaById = municipalityAreaById(adminId, prefectureMask, sea);
  const lifecycle = adminCenters.map((center, id) => {
    const protectedSeed = isProtectedAdminSeed(center);
    const area = areaById.get(id) || 0;
    const enoughArea = area >= (protectedSeed ? 28 : minArea);
    return {
      id,
      protected: protectedSeed,
      area,
      state: enoughArea || protectedSeed ? "survived" : "pending",
    };
  });
  return lifecycle;
}

function activeSeedIds(seedLifecycle) {
  return new Set(seedLifecycle.filter((seed) => seed.state === "survived" || seed.protected).map((seed) => seed.id));
}

function dominantCompartmentOwners(compartments, adminId) {
  const owner = new Int16Array(compartments.length);
  owner.fill(-1);
  for (const unit of compartments) {
    if (!unit || unit.area === 0) continue;
    const counts = new Map();
    for (const i of unit.cells) {
      const id = adminId[i];
      if (id >= 0) counts.set(id, (counts.get(id) || 0) + 1);
    }
    let bestId = -1, best = -1;
    for (const [id, count] of counts) if (count > best) { best = count; bestId = id; }
    owner[unit.id] = bestId;
  }
  return owner;
}

function applyCompartmentOwners(adminId, compartments, owner) {
  for (const unit of compartments) {
    if (!unit || unit.area === 0) continue;
    const id = owner[unit.id];
    if (id < 0) continue;
    for (const i of unit.cells) adminId[i] = id;
  }
}

function absorbSeedCompartments(adminId, compartments, seedLifecycle) {
  const owner = dominantCompartmentOwners(compartments, adminId);
  const absorbed = new Set(seedLifecycle.filter((seed) => seed.state === "absorbed").map((seed) => seed.id));
  let changed = 0;
  for (const unit of compartments) {
    if (!unit || unit.area === 0 || !absorbed.has(owner[unit.id])) continue;
    let bestId = -1, bestScore = -INF;
    for (const [neighborId, edge] of unit.adjacent) {
      const candidate = owner[neighborId];
      if (candidate < 0 || absorbed.has(candidate)) continue;
      const neighbor = compartments[neighborId];
      const score = edge.count * 2 - (edge.target / Math.max(1, edge.count)) * 2 + (neighbor?.area || 0) * 0.002;
      if (score > bestScore) { bestScore = score; bestId = candidate; }
    }
    if (bestId < 0) continue;
    owner[unit.id] = bestId;
    changed += unit.area;
  }
  applyCompartmentOwners(adminId, compartments, owner);
  return changed;
}

function splitOversizedLowlandsWithPendingSeeds(adminId, prefectureMask, sea, fields, compartments, adminCenters, seedLifecycle, settlements = []) {
  const { plain, agriculture, basinField, coastalLowland, valleyField, ridgeField, slope, elevation } = fields;
  const areaById = municipalityAreaById(adminId, prefectureMask, sea);
  const areas = [...areaById.values()].sort((a, b) => a - b);
  const median = areas.length ? areas[Math.floor(areas.length / 2)] : 0;
  if (!median) return { changedCells: 0, splitMunicipalities: 0, pendingSeedsUsed: 0 };
  const owner = dominantCompartmentOwners(compartments, adminId);
  const unitsByOwner = new Map();
  for (const unit of compartments) {
    if (!unit || unit.area === 0 || owner[unit.id] < 0) continue;
    if (!unitsByOwner.has(owner[unit.id])) unitsByOwner.set(owner[unit.id], []);
    unitsByOwner.get(owner[unit.id]).push(unit);
  }
  const pending = seedLifecycle.filter((seed) => seed.state === "pending" && !seed.protected);
  let changedCells = 0;
  let splitMunicipalities = 0;
  let pendingSeedsUsed = 0;
  for (const [id, units] of unitsByOwner) {
    const area = areaById.get(id) || 0;
    if (area < Math.max(260, median * 1.45) || units.length < 6) continue;
    let lowland = 0, rough = 0;
    for (const unit of units) {
      for (const i of unit.cells) {
        lowland += (plain[i] || 0) * 0.38 + (agriculture[i] || 0) * 0.20 + basinField[i] * 0.22 + coastalLowland[i] * 0.22 + valleyField[i] * 0.10;
        rough += ridgeField[i] * 0.48 + slope[i] * 0.34 + Math.max(0, elevation[i] - 0.58) * 0.30;
      }
    }
    if (lowland / area < 0.26 || rough / area > 0.48) continue;
    const localPending = pending.filter((seed) => {
      const center = adminCenters[seed.id];
      if (!center || !inside(center.x, center.y)) return false;
      const centerOwner = adminId[indexOf(center.x, center.y)];
      return centerOwner === id || Math.hypot(center.x - (adminCenters[id]?.x || center.x), center.y - (adminCenters[id]?.y || center.y)) < 28;
    });
    const localSettlements = settlements.filter((p) => p && inside(p.x, p.y) && adminId[indexOf(p.x, p.y)] === id);
    if (localPending.length === 0 || localPending.length + localSettlements.length < 2) continue;
    let municipalitySplit = false;
    for (const seed of localPending.slice(0, 3)) {
      const center = adminCenters[seed.id];
      if (!center) continue;
      const targetArea = clamp(95 + (center.score || 0.5) * 60, 90, 180);
      let claimed = 0;
      const candidates = units
        .filter((unit) => owner[unit.id] === id && unit.classId !== 8 && unit.classId !== 9)
        .map((unit) => ({
          unit,
          score: Math.hypot(unit.x - center.x, unit.y - center.y) - (unit.lowlandFitness || 0) * 8 - (unit.urbanWeight || 0) * 3,
        }))
        .sort((a, b) => a.score - b.score);
      if (candidates.length < 2) continue;
      for (const { unit } of candidates) {
        if (claimed >= targetArea && claimed >= 2) break;
        owner[unit.id] = seed.id;
        claimed += unit.area;
        changedCells += unit.area;
      }
      if (claimed >= 45) {
        seed.state = "survived";
        seed.area = claimed;
        pendingSeedsUsed++;
        municipalitySplit = true;
      }
    }
    if (municipalitySplit) splitMunicipalities++;
  }
  applyCompartmentOwners(adminId, compartments, owner);
  return { changedCells, splitMunicipalities, pendingSeedsUsed };
}

function promotePendingSeedsForMunicipalityCount(adminId, prefectureMask, sea, fields, compartments, adminCenters, seedLifecycle, targetMinCount = 20) {
  const { plain, agriculture, basinField, coastalLowland, valleyField, ridgeField, slope, elevation } = fields;
  let areaById = municipalityAreaById(adminId, prefectureMask, sea);
  let currentCount = areaById.size;
  if (currentCount >= targetMinCount) return { changedCells: 0, promotedSeeds: 0 };
  const owner = dominantCompartmentOwners(compartments, adminId);
  let changedCells = 0;
  let promotedSeeds = 0;
  const pending = seedLifecycle
    .filter((seed) => seed.state === "pending" && !seed.protected)
    .sort((a, b) => (adminCenters[b.id]?.score || 0) - (adminCenters[a.id]?.score || 0));
  for (const seed of pending) {
    if (currentCount >= targetMinCount) break;
    const center = adminCenters[seed.id];
    if (!center || !inside(center.x, center.y)) continue;
    const existingArea = areaById.get(seed.id) || 0;
    if (existingArea >= 12) {
      seed.state = "survived";
      seed.area = existingArea;
      promotedSeeds++;
      continue;
    }
    const candidates = compartments
      .filter((unit) => {
        if (!unit || unit.area === 0) return false;
        const currentOwner = owner[unit.id];
        if (currentOwner < 0 || currentOwner === seed.id) return false;
        const ownerArea = areaById.get(currentOwner) || 0;
        if (ownerArea < 90) return false;
        const lowlandFit = (unit.lowlandFitness || 0) + (unit.basinIdentity || 0) * 0.15 + (unit.coastalExposure || 0) * 0.15;
        if (lowlandFit < 0.26) return false;
        return Math.hypot(unit.x - center.x, unit.y - center.y) < 36;
      })
      .map((unit) => ({
        unit,
        score: Math.hypot(unit.x - center.x, unit.y - center.y) - (unit.lowlandFitness || 0) * 6 - (unit.urbanWeight || 0) * 2,
      }))
      .sort((a, b) => a.score - b.score);
    if (candidates.length === 0) continue;
    let claimed = 0;
    for (const { unit } of candidates) {
      const currentOwner = owner[unit.id];
      if ((areaById.get(currentOwner) || 0) - unit.area < 70) continue;
      owner[unit.id] = seed.id;
      areaById.set(currentOwner, (areaById.get(currentOwner) || 0) - unit.area);
      areaById.set(seed.id, (areaById.get(seed.id) || 0) + unit.area);
      claimed += unit.area;
      changedCells += unit.area;
      if (claimed >= 55) break;
    }
    if (claimed >= 25) {
      seed.state = "survived";
      seed.area = areaById.get(seed.id) || claimed;
      promotedSeeds++;
      currentCount++;
    }
  }
  applyCompartmentOwners(adminId, compartments, owner);
  return { changedCells, promotedSeeds };
}

function restoreSurvivedSeedsByCompartment(adminId, prefectureMask, sea, compartments, adminCenters, seedLifecycle, targetMinCount = 20) {
  const areaById = municipalityAreaById(adminId, prefectureMask, sea);
  let currentCount = areaById.size;
  if (currentCount >= targetMinCount) return { changedCells: 0, restoredSeeds: 0 };
  const owner = dominantCompartmentOwners(compartments, adminId);
  let changedCells = 0;
  let restoredSeeds = 0;
  const missing = seedLifecycle
    .filter((seed) => (seed.state === "survived" || seed.protected) && (areaById.get(seed.id) || 0) === 0)
    .sort((a, b) => (b.protected ? 1 : 0) - (a.protected ? 1 : 0));
  for (const seed of missing) {
    if (currentCount >= targetMinCount) break;
    const center = adminCenters[seed.id];
    if (!center || !inside(center.x, center.y)) continue;
    const candidates = compartments
      .filter((unit) => {
        if (!unit || unit.area === 0 || unit.classId === 8 || unit.classId === 9) return false;
        const currentOwner = owner[unit.id];
        if (currentOwner < 0 || currentOwner === seed.id) return false;
        if ((areaById.get(currentOwner) || 0) - unit.area < 25) return false;
        return Math.hypot(unit.x - center.x, unit.y - center.y) < 90 && ((unit.lowlandFitness || 0) > 0.08 || seed.protected);
      })
      .map((unit) => ({
        unit,
        score: Math.hypot(unit.x - center.x, unit.y - center.y) - (unit.lowlandFitness || 0) * 6 - (unit.urbanWeight || 0) * 2 + (unit.classId === 8 || unit.classId === 9 ? 20 : 0),
      }))
      .sort((a, b) => a.score - b.score);
    if (candidates.length === 0) continue;
    const unit = candidates[0].unit;
    const oldOwner = owner[unit.id];
    if ((areaById.get(oldOwner) || 0) - unit.area < 25) continue;
    owner[unit.id] = seed.id;
    const claimed = unit.area;
    areaById.set(oldOwner, (areaById.get(oldOwner) || 0) - claimed);
    changedCells += claimed;
    areaById.set(seed.id, claimed);
    seed.area = claimed;
    restoredSeeds++;
    currentCount++;
  }
  applyCompartmentOwners(adminId, compartments, owner);
  return { changedCells, restoredSeeds };
}

function municipalityCountBoundsForRegion(landCells, meta = {}) {
  const focused = meta.isFocusedRegion !== false;
  if (focused) return { min: 20, max: 50 };
  // Neighbor prefectures are often visible only as clipped map-edge slivers.
  // Avoid giving every tiny visible fragment the full 20-municipality floor.
  let min = 1;
  if (landCells >= 500) min = 2;
  if (landCells >= 950) min = 3;
  if (landCells >= 1700) min = 5;
  if (landCells >= 2800) min = 7;
  if (landCells >= 4300) min = 10;
  const max = clamp(Math.round(landCells / 260 + 2), Math.max(min, 2), 34);
  return { min, max };
}

function computeTargetMunicipalityCount({ prefectureMask, sea, elevation, slope, ridgeField, coastalLowland, basinField, modernCities, markets, ports, satelliteCities, villages, adminRegionMeta = {} }) {
  let landCells = 0;
  let habitableCells = 0;
  let lowlandCells = 0;
  let coastlineComplexity = 0;
  let mountainCells = 0;
  for (let y = 1; y < MAP_H - 1; y++) {
    for (let x = 1; x < MAP_W - 1; x++) {
      const i = indexOf(x, y);
      if (!prefectureMask[i] || sea[i]) continue;
      landCells++;
      if (slope[i] < 0.42 && ridgeField[i] < 0.55 && (!elevation || elevation[i] < 0.72)) habitableCells++;
      if ((coastalLowland[i] > 0.20 || basinField[i] > 0.24) && slope[i] < 0.36 && ridgeField[i] < 0.52) lowlandCells++;
      if (ridgeField[i] > 0.52 || slope[i] > 0.48) mountainCells++;
      for (const [nx, ny] of [[x + 1, y], [x - 1, y], [x, y + 1], [x, y - 1]]) {
        const ni = indexOf(nx, ny);
        if (sea[ni]) {
          coastlineComplexity += 1 + coastalLowland[i] * 0.8;
          break;
        }
      }
    }
  }
  const independentSatellites = (satelliteCities || []).filter((p) => p.municipalityClass === "independentSatelliteMunicipality").length;
  const settlementWeight = modernCities.length * 1.6 + markets.length * 1.0 + ports.length * 0.8 + independentSatellites * 0.7 + villages.length * 0.25;
  const basinBonus = Math.min(8, [...basinField].filter((v, i) => prefectureMask[i] && !sea[i] && v > 0.34).length / 520);
  const mountainRatio = landCells ? mountainCells / landCells : 0;
  const lowlandBonus = Math.min(7, lowlandCells / 430);
  const rawTarget = Math.round(habitableCells / 230 + settlementWeight + coastlineComplexity * 0.03 + basinBonus * 0.55 + lowlandBonus - mountainRatio * 2.2);
  const { min, max } = municipalityCountBoundsForRegion(landCells, adminRegionMeta);
  return clamp(rawTarget, min, max);
}

function lowlandAdminSeedScore(i, { elevation, slope, ridgeField, plain, basinField, coastalLowland, settlementScore, populationDensity, roadInfluence, railInfluence2, stationInfluence, landuse }) {
  const lowRelief = clamp((0.70 - elevation[i]) * 1.35) + clamp((0.34 - slope[i]) * 1.55) + clamp((0.48 - ridgeField[i]) * 1.10);
  const landuseFit = [1, 2, 3, 4, 7, 8].includes(landuse[i]) ? 0.40 : landuse[i] === 5 || landuse[i] === 6 ? 0.12 : 0;
  return clamp(
    lowRelief * 0.25 +
    plain[i] * 0.28 +
    basinField[i] * 0.24 +
    coastalLowland[i] * 0.24 +
    settlementScore[i] * 0.30 +
    populationDensity[i] * 0.32 +
    roadInfluence[i] * 0.16 +
    railInfluence2[i] * 0.16 +
    (stationInfluence?.[i] || 0) * 0.18 +
    landuseFit -
    Math.max(0, elevation[i] - 0.62) * 1.2 -
    Math.max(0, ridgeField[i] - 0.54) * 0.9
  );
}

function buildLowlandAdminSeeds({
  seed,
  targetMunicipalityCount,
  prefectureMask,
  sea,
  elevation,
  slope,
  ridgeField,
  plain,
  basinField,
  coastalLowland,
  settlementScore,
  populationDensity,
  roadInfluence,
  railInfluence2,
  stationInfluence,
  landuse,
  modernCities,
  satelliteCities,
  markets,
  ports,
  newTowns,
  stations,
}) {
  const fields = { elevation, slope, ridgeField, plain, basinField, coastalLowland, settlementScore, populationDensity, roadInfluence, railInfluence2, stationInfluence, landuse };
  function validLowlandPoint(p, strict = true) {
    if (!p || !inside(p.x, p.y)) return false;
    const i = indexOf(p.x, p.y);
    if (!prefectureMask[i] || sea[i]) return false;
    const score = lowlandAdminSeedScore(i, fields);
    const mountain = elevation[i] > 0.70 || slope[i] > 0.52 || ridgeField[i] > 0.62;
    return score >= (strict ? 0.34 : 0.24) && (!mountain || p.isPrefecturalCapital || (p.population || 0) >= 220000 || p.portClass === "major");
  }
  const realSeeds = [];
  for (const city of modernCities || []) {
    if (!validLowlandPoint(city, !city.isPrefecturalCapital)) continue;
    if (!city.isPrefecturalCapital && (city.population || 0) < 85000) continue;
    const i = indexOf(city.x, city.y);
    realSeeds.push({ x: city.x, y: city.y, score: 1.35 + (city.population || 0) / 650000 + lowlandAdminSeedScore(i, fields), population: city.population || 0, protectedCity: city, seedKind: city.isPrefecturalCapital ? "capital" : "modernCity" });
  }
  for (const city of satelliteCities || []) {
    if (city.municipalityClass !== "independentSatelliteMunicipality" || !validLowlandPoint(city, false)) continue;
    const i = indexOf(city.x, city.y);
    realSeeds.push({ x: city.x, y: city.y, score: 0.92 + (city.population || 0) / 260000 + lowlandAdminSeedScore(i, fields), population: city.population || 0, protectedSatellite: city, seedKind: "satelliteCity" });
  }
  for (const p of [...(markets || []), ...(ports || []), ...(newTowns || [])]) {
    if (!validLowlandPoint(p, true)) continue;
    const i = indexOf(p.x, p.y);
    const portBonus = p.portClass === "major" ? 0.45 : p.portClass === "regional" ? 0.26 : 0;
    realSeeds.push({ x: p.x, y: p.y, score: 0.74 + lowlandAdminSeedScore(i, fields) + portBonus + (p.population || 0) / 420000, population: p.population || 0, portClass: p.portClass, source: p, seedKind: p.portClass ? "port" : "marketTown" });
  }
  const picked = pickEntities(realSeeds, {
    max: targetMunicipalityCount,
    minDistance: 5 + Math.floor(rand(seed, 1302) * 3),
    threshold: 0.62,
    seed: seed + 1300,
    jitter: 0.025,
  });
  const invisibleCandidates = [];
  for (let y = 2; y < MAP_H - 2; y++) {
    for (let x = 2; x < MAP_W - 2; x++) {
      const i = indexOf(x, y);
      if (!prefectureMask[i] || sea[i]) continue;
      const score = lowlandAdminSeedScore(i, fields) + hash2(x, y, seed + 1311) * 0.045;
      if (score < 0.48) continue;
      const insideDenseCore = modernCities.some((city) => (city.population || 0) >= 180000 && Math.hypot(city.x - x, city.y - y) < Math.max(5, (city.coreRadius || 4) * 1.7));
      if (insideDenseCore) continue;
      invisibleCandidates.push({ x, y, score, invisibleLowlandAdminSeed: true, seedKind: "invisibleLowland" });
    }
  }
  if (picked.length < targetMunicipalityCount) {
    const extra = pickEntities(invisibleCandidates, {
      max: targetMunicipalityCount - picked.length,
      minDistance: 5,
      threshold: 0.48,
      seed: seed + 1304,
      jitter: 0.02,
    });
    for (const p of extra) if (picked.every((q) => Math.hypot(p.x - q.x, p.y - q.y) >= 4)) picked.push(p);
  }
  if (picked.length < Math.min(targetMunicipalityCount, 20)) {
    const relaxed = pickEntities(invisibleCandidates, {
      max: Math.min(targetMunicipalityCount, 20) - picked.length,
      minDistance: 4,
      threshold: 0.38,
      seed: seed + 1305,
      jitter: 0.02,
    });
    for (const p of relaxed) if (picked.length < targetMunicipalityCount && picked.every((q) => Math.hypot(p.x - q.x, p.y - q.y) >= 3.5)) picked.push(p);
  }
  return picked.slice(0, targetMunicipalityCount);
}

function estimateUrbanComponentArea(city, prefectureMask, sea, landuse, populationDensity) {
  if (!city || !inside(city.x, city.y)) return 0;
  const start = indexOf(city.x, city.y);
  if (!prefectureMask[start] || sea[start]) return 0;
  const radius = Math.ceil(Math.max(7, (city.urbanRadius || 6) * 1.7));
  const seen = new Uint8Array(SIZE);
  const queue = [start];
  seen[start] = 1;
  let area = 0;
  for (let q = 0; q < queue.length; q++) {
    const cur = queue[q];
    const [x, y] = xyOf(cur);
    const d = Math.hypot(x - city.x, y - city.y);
    if (d > radius) continue;
    const urban = (landuse[cur] >= 2 && landuse[cur] <= 4) || landuse[cur] === 7 || landuse[cur] === 8 || populationDensity[cur] > 0.18;
    if (!urban) continue;
    area++;
    for (const [dx, dy] of [[1, 0], [-1, 0], [0, 1], [0, -1]]) {
      const nx = x + dx, ny = y + dy;
      if (!inside(nx, ny)) continue;
      const ni = indexOf(nx, ny);
      if (seen[ni] || !prefectureMask[ni] || sea[ni]) continue;
      seen[ni] = 1;
      queue.push(ni);
    }
  }
  return area;
}

function terrainSeparationBetween(a, b, ridgeField, river, flowAccum, populationDensity, landuse) {
  if (!a || !b) return { separatedByBarrier: false, ruralGap: false, averageDensity: 0, maxBarrier: 0 };
  const steps = Math.max(1, Math.ceil(Math.hypot(a.x - b.x, a.y - b.y)));
  let maxBarrier = 0;
  let lowUrbanRun = 0;
  let bestLowUrbanRun = 0;
  let densitySum = 0;
  for (let s = 0; s <= steps; s++) {
    const t = s / steps;
    const x = Math.round(a.x + (b.x - a.x) * t);
    const y = Math.round(a.y + (b.y - a.y) * t);
    if (!inside(x, y)) continue;
    const i = indexOf(x, y);
    const barrier = Math.max(ridgeField[i] * 0.95, river[i] * 0.85, flowAccum[i] * 0.42);
    maxBarrier = Math.max(maxBarrier, barrier);
    densitySum += populationDensity[i];
    const urban = (landuse[i] >= 2 && landuse[i] <= 4) || landuse[i] === 7 || populationDensity[i] > 0.20;
    if (urban) lowUrbanRun = 0;
    else {
      lowUrbanRun++;
      bestLowUrbanRun = Math.max(bestLowUrbanRun, lowUrbanRun);
    }
  }
  return {
    separatedByBarrier: maxBarrier > 0.56,
    ruralGap: bestLowUrbanRun >= 4,
    averageDensity: densitySum / (steps + 1),
    maxBarrier,
  };
}

function classifySatelliteMunicipalities(satelliteCities, modernCities, prefectureMask, sea, landuse, populationDensity, roadInfluence, railInfluence2, ridgeField, river, flowAccum) {
  let independent = 0;
  let attached = 0;
  for (const sat of satelliteCities || []) {
    if (!sat || !inside(sat.x, sat.y) || !prefectureMask[indexOf(sat.x, sat.y)] || sea[indexOf(sat.x, sat.y)]) continue;
    const parent = modernCities[sat.parentCityIndex] || modernCities.slice().sort((a, b) => Math.hypot(a.x - sat.x, a.y - sat.y) - Math.hypot(b.x - sat.x, b.y - sat.y))[0];
    const parentDistance = parent ? Math.hypot(parent.x - sat.x, parent.y - sat.y) : 99;
    const separation = terrainSeparationBetween(sat, parent, ridgeField, river, flowAccum, populationDensity, landuse);
    const urbanArea = estimateUrbanComponentArea(sat, prefectureMask, sea, landuse, populationDensity);
    const i = indexOf(sat.x, sat.y);
    const continuousUrban = parent && parentDistance < Math.max(10, (parent.urbanRadius || 12) + (sat.urbanRadius || 5) + 5) && separation.averageDensity > 0.14 && !separation.ruralGap && !separation.separatedByBarrier;
    const newTownLike = landuse[i] === 7 || (railInfluence2[i] > 0.22 && roadInfluence[i] > 0.12 && (sat.population || 0) < 70000);
    let municipalityClass = "independentSatelliteMunicipality";
    if (continuousUrban && (sat.population || 0) < 90000) municipalityClass = "suburbanDistrictMergedWithParent";
    else if (newTownLike && (sat.population || 0) < 85000 && !separation.separatedByBarrier) municipalityClass = "newTownDistrict";
    else if ((sat.population || 0) < 42000 && urbanArea < 55 && !separation.separatedByBarrier) municipalityClass = "smallTownAttachedToRuralMunicipality";
    else if ((sat.population || 0) >= 60000 && urbanArea >= 42 && (separation.separatedByBarrier || separation.ruralGap || parentDistance > 15)) municipalityClass = "independentSatelliteMunicipality";

    sat.municipalityClass = municipalityClass;
    sat.parentX = parent?.x;
    sat.parentY = parent?.y;
    sat.parentAdminHint = -1;
    sat.distinctUrbanComponentArea = urbanArea;
    sat.separatedByBarrier = separation.separatedByBarrier || separation.ruralGap;
    sat.satelliteMinArea = clamp(90 + Math.sqrt(sat.population || 24000) * 0.62 + (sat.urbanRadius || 5) * 12, 80, 360);
    if (municipalityClass === "independentSatelliteMunicipality") independent++;
    else attached++;
  }
  return { independent, attached };
}

function expandSatelliteMunicipalityCatchment(adminId, satellite, targetAdmin, context) {
  const { prefectureMask, sea, elevation, slope, river, ridgeField, valleyField, basinField, coastalLowland, flowAccum, landuse, populationDensity, roadInfluence, railInfluence2, stationInfluence, modernCities } = context;
  if (!satellite || targetAdmin < 0 || !inside(satellite.x, satellite.y)) return 0;
  const start = indexOf(satellite.x, satellite.y);
  if (!prefectureMask[start] || sea[start]) return 0;
  const targetAreaBase = clamp(90 + Math.sqrt(satellite.population || 24000) * 0.8 + (satellite.urbanRadius || 5) * 18, 120, 520);
  const targetArea = satellite.municipalityClass === "smallTownAttachedToRuralMunicipality"
    ? Math.min(130, targetAreaBase * 0.55)
    : satellite.municipalityClass === "suburbanDistrictMergedWithParent" || satellite.municipalityClass === "newTownDistrict"
      ? Math.min(190, targetAreaBase * 0.62)
      : targetAreaBase;
  const maxCost = satellite.municipalityClass === "independentSatelliteMunicipality" ? 46 : 32;
  const heap = new MinHeap();
  const best = new Float32Array(SIZE);
  best.fill(INF);
  heap.push({ i: start, f: 0 });
  best[start] = 0;
  const claimed = [];
  while (heap.length > 0 && claimed.length < targetArea) {
    const cur = heap.pop();
    if (!cur || cur.f > best[cur.i] + 1e-5 || cur.f > maxCost) continue;
    const [x, y] = xyOf(cur.i);
    const d = Math.hypot(x - satellite.x, y - satellite.y);
    if (!prefectureMask[cur.i] || sea[cur.i]) continue;
    let invadesOtherCore = false;
    for (const city of modernCities || []) {
      if (!city || (city.population || 0) < 140000) continue;
      if (Math.hypot(city.x - satellite.x, city.y - satellite.y) < 4) continue;
      if (Math.hypot(city.x - x, city.y - y) <= Math.max(3.5, (city.coreRadius || 4) * 1.25)) {
        invadesOtherCore = true;
        break;
      }
    }
    if (invadesOtherCore) continue;
    const compatible = d <= (satellite.urbanRadius || 5) * 1.25 ||
      [2, 3, 4, 7, 8].includes(landuse[cur.i]) ||
      populationDensity[cur.i] > 0.12 ||
      roadInfluence[cur.i] > 0.12 ||
      railInfluence2[cur.i] > 0.10 ||
      stationInfluence?.[cur.i] > 0.10 ||
      basinField[cur.i] > 0.22 ||
      valleyField[cur.i] > 0.24 ||
      coastalLowland[cur.i] > 0.20;
    if (!compatible && claimed.length > targetArea * 0.55) continue;
    claimed.push(cur.i);
    for (const [dx, dy, step] of [[1, 0, 1], [-1, 0, 1], [0, 1, 1], [0, -1, 1], [1, 1, 1.41], [-1, 1, 1.41], [1, -1, 1.41], [-1, -1, 1.41]]) {
      const nx = x + dx, ny = y + dy;
      if (!inside(nx, ny)) continue;
      const ni = indexOf(nx, ny);
      if (!prefectureMask[ni] || sea[ni]) continue;
      const barrier = ridgeField[ni] * 5.2 + Math.max(0, elevation[ni] - 0.58) * 4.0 + slope[ni] * 2.2 + (river[ni] > 0.55 || flowAccum[ni] > 0.70 ? 7.5 : river[ni] > 0.30 ? 2.8 : 0);
      const living = ([2, 3, 4, 7, 8].includes(landuse[ni]) ? 2.2 : 0) + populationDensity[ni] * 2.0 + roadInfluence[ni] * 0.85 + railInfluence2[ni] * 0.95 + (stationInfluence?.[ni] || 0) * 1.2 + basinField[ni] * 0.42 + valleyField[ni] * 0.48 + coastalLowland[ni] * 0.32;
      const distanceCost = Math.hypot(nx - satellite.x, ny - satellite.y) / Math.max(7, (satellite.urbanRadius || 5) * 1.9);
      const nd = cur.f + Math.max(0.28, 1.05 + barrier - living + distanceCost) * step;
      if (nd < best[ni]) {
        best[ni] = nd;
        heap.push({ i: ni, f: nd });
      }
    }
  }
  let changed = 0;
  for (const i of claimed) {
    if (adminId[i] !== targetAdmin) changed++;
    adminId[i] = targetAdmin;
  }
  return changed;
}

function generateAdminLayoutForMask({
  seed,
  prefectureMask,
  sea,
  elevation,
  slope,
  river,
  ridgeField,
  naturalBarrierScore,
  valleyField,
  basinField,
  coastalLowland,
  flowAccum,
  plain,
  agriculture,
  settlementScore,
  populationDensity,
  stationInfluence,
  roadInfluence,
  railInfluence2,
  villageInfluence,
  landuse,
  modernCities,
  satelliteCities,
  newTowns,
  markets,
  villages,
  ports,
  stations,
  industrialZones,
  logisticsParks,
  adminRegionMeta = {},
  adminProgress = null,
}) {
  const boundaryRidgeField = naturalBarrierScore
    ? Float32Array.from(ridgeField, (value, i) => clamp(value * 0.72 + naturalBarrierScore[i] * 0.46))
    : ridgeField;
  adminProgress?.({ status: "admin-step", regionId: adminRegionMeta.regionId, step: "classify satellites" });
  const satelliteClassificationDebug = classifySatelliteMunicipalities(satelliteCities, modernCities, prefectureMask, sea, landuse, populationDensity, roadInfluence, railInfluence2, boundaryRidgeField, river, flowAccum);
  const targetMunicipalityCount = computeTargetMunicipalityCount({ prefectureMask, sea, elevation, slope, ridgeField: boundaryRidgeField, coastalLowland, basinField, modernCities, markets, ports, satelliteCities, villages, adminRegionMeta });
  const compartmentMultiplier = clamp(4.6 + rand(seed, 1320) * 2.4, 4.6, 7.0);
  const regionLandArea = adminRegionMeta.landArea || maskLandArea(prefectureMask, sea);
  const minCompartmentTarget = adminRegionMeta.isFocusedRegion === false
    ? clamp(Math.round(Math.max(targetMunicipalityCount * 3.2, regionLandArea / 75)), 18, 90)
    : 120;
  const maxCompartmentTarget = adminRegionMeta.isFocusedRegion === false
    ? clamp(Math.round(Math.max(targetMunicipalityCount * 5.8, regionLandArea / 38)), minCompartmentTarget, 220)
    : 360;
  let targetCompartmentCount = clamp(Math.round(targetMunicipalityCount * compartmentMultiplier), minCompartmentTarget, maxCompartmentTarget);
  let adminCentersRaw = buildLowlandAdminSeeds({
    seed,
    targetMunicipalityCount,
    prefectureMask,
    sea,
    elevation,
    slope,
    ridgeField: boundaryRidgeField,
    plain,
    basinField,
    coastalLowland,
    settlementScore,
    populationDensity,
    roadInfluence,
    railInfluence2,
    stationInfluence,
    landuse,
    modernCities,
    satelliteCities,
    markets,
    ports,
    newTowns,
    stations,
  });
  if (adminCentersRaw.length < 20) targetCompartmentCount = Math.max(targetCompartmentCount, minCompartmentTarget);
  adminProgress?.({ status: "admin-step", regionId: adminRegionMeta.regionId, step: "natural compartments", targetMunicipalityCount, targetCompartmentCount, seedCount: adminCentersRaw.length });
  const compartmentAssignment = assignAdminRegionsFromNaturalCompartments(prefectureMask, sea, elevation, slope, river, boundaryRidgeField, valleyField, basinField, coastalLowland, flowAccum, plain, agriculture, populationDensity, landuse, adminCentersRaw, {
    seed,
    targetMunicipalityCount,
    targetCompartmentCount,
    maxNaturalCompartmentArea: Math.max(32, Math.round(maskLandArea(prefectureMask, sea) / Math.max(1, targetCompartmentCount) * 1.65)),
    progress: (step) => adminProgress?.({ status: "admin-step", regionId: adminRegionMeta.regionId, step }),
  });
  const adminId = compartmentAssignment.adminId;
  let previousSnapshot = new Int16Array(adminId);
  const adminDebug = {
    changedAfterSmooth: 0,
    changedAfterUrbanLock: 0,
    changedAfterSmallUrbanLock: 0,
    changedAfterInitialMerge: 0,
    changedAfterInitialExclaveRemoval: 0,
    changedAfterLandscapePartition: 0,
    changedAfterSnap: 0,
    changedAfterOversizedRuralSplit: 0,
    changedAfterFinalExclaveRemoval: 0,
    changedAfterFinalMerge: 0,
    targetMunicipalityCount,
    actualMunicipalityCount: 0,
    municipalityCountReason: "habitable cells, settlement weight, coastline complexity, basin/lowland bonus, and mountain-ratio adjustment",
    changedAfterCompartmentAssignment: compartmentAssignment.debug?.naturalCompartmentCount || 0,
    oversizedRuralSplits: 0,
    oversizedLowlandSplits: 0,
    ruralSplitsAccepted: 0,
    ruralSplitsRejected: 0,
    targetNaturalCompartmentCount: targetCompartmentCount,
    compartmentMultiplier,
    lowlandAdminSeedCount: adminCentersRaw.filter((p) => p.invisibleLowlandAdminSeed).length,
    lowlandAdminSeeds: adminCentersRaw.filter((p) => p.invisibleLowlandAdminSeed).map((p) => ({ x: p.x, y: p.y })),
    realAdminSeedCount: adminCentersRaw.filter((p) => !p.invisibleLowlandAdminSeed).length,
    highMountainAdminSeedCount: adminCentersRaw.filter((p) => {
      const i = indexOf(p.x, p.y);
      return elevation[i] > 0.70 || slope[i] > 0.52 || boundaryRidgeField[i] > 0.62;
    }).length,
    candidateSeedCount: adminCentersRaw.length,
    protectedSeedCount: adminCentersRaw.filter(isProtectedAdminSeed).length,
    survivedSeedCount: 0,
    pendingSeedCount: 0,
    absorbedSeedCount: 0,
    pendingSeedsUsedForLowlandSplit: 0,
    finalMunicipalityCount: 0,
    finalTinyMunicipalityCount: 0,
    seedCellRevivalCount: 0,
    satelliteMunicipalitiesCreated: adminCentersRaw.filter((p) => p.protectedSatellite).length,
    satelliteMunicipalitiesMerged: 0,
    satelliteMunicipalitiesExpanded: 0,
    satelliteMunicipalitiesTooSmall: 0,
    averageSatelliteMunicipalityArea: 0,
    minSatelliteMunicipalityArea: 0,
    satelliteMunicipalityAreaByNameOrIndex: {},
    independentSatelliteMunicipalities: satelliteClassificationDebug.independent,
    attachedSatelliteDistricts: satelliteClassificationDebug.attached,
    satelliteMunicipalityStats: satelliteClassificationDebug,
    ...compartmentAssignment.debug,
  };
  adminProgress?.({ status: "admin-step", regionId: adminRegionMeta.regionId, step: "seed lifecycle" });
  const seedLifecycle = buildSeedLifecycle(adminCentersRaw, adminId, prefectureMask, sea, 35);
  const pendingSplitDebug = splitOversizedLowlandsWithPendingSeeds(adminId, prefectureMask, sea, {
    plain, agriculture, basinField, coastalLowland, valleyField, ridgeField: boundaryRidgeField, slope, elevation,
  }, compartmentAssignment.compartments, adminCentersRaw, seedLifecycle, [...(satelliteCities || []), ...newTowns, ...markets, ...villages, ...ports]);
  adminDebug.changedAfterPendingSeedLowlandSplit = pendingSplitDebug.changedCells;
  adminDebug.pendingSeedsUsedForLowlandSplit = pendingSplitDebug.pendingSeedsUsed;
  adminDebug.oversizedLowlandSplits += pendingSplitDebug.splitMunicipalities;
  const pendingPromotionDebug = promotePendingSeedsForMunicipalityCount(adminId, prefectureMask, sea, {
    plain, agriculture, basinField, coastalLowland, valleyField, ridgeField: boundaryRidgeField, slope, elevation,
  }, compartmentAssignment.compartments, adminCentersRaw, seedLifecycle, Math.min(24, targetMunicipalityCount));
  adminDebug.changedAfterPendingSeedCountRepair = pendingPromotionDebug.changedCells;
  adminDebug.pendingSeedsPromotedForCount = pendingPromotionDebug.promotedSeeds;
  let areaAfterPendingSplit = municipalityAreaById(adminId, prefectureMask, sea);
  for (const seedState of seedLifecycle) {
    if (seedState.state !== "pending") continue;
    seedState.area = areaAfterPendingSplit.get(seedState.id) || 0;
    if (seedState.area >= 35) seedState.state = "survived";
    else seedState.state = "absorbed";
  }
  adminDebug.changedAfterAbsorbingSeeds = absorbSeedCompartments(adminId, compartmentAssignment.compartments, seedLifecycle);
  let activeAdminIds = activeSeedIds(seedLifecycle);
  function markChanged(field) {
    adminDebug[field] = changedCellsSince(previousSnapshot, adminId, prefectureMask, sea);
    previousSnapshot = new Int16Array(adminId);
  }
  adminProgress?.({ status: "admin-step", regionId: adminRegionMeta.regionId, step: "smooth boundaries" });
  smoothAdminRegionsTerrainAware(adminId, prefectureMask, sea, elevation, slope, river, boundaryRidgeField, valleyField, populationDensity, landuse, 2);
  markChanged("changedAfterSmooth");

  function lockUrbanClusterToMunicipality(city, radius, allowSuburban = true) {
    if (!city || !prefectureMask[indexOf(city.x, city.y)]) return;
    let bestAdmin = -1;
    let bestD = INF;
    adminCentersRaw.forEach((center, id) => {
      if (!activeAdminIds.has(id)) return;
      const d = Math.hypot(center.x - city.x, center.y - city.y);
      if (d < bestD) { bestD = d; bestAdmin = id; }
    });
    if (bestAdmin < 0) return;
    const r = Math.ceil(radius);
    for (let dy = -r; dy <= r; dy++) {
      for (let dx = -r; dx <= r; dx++) {
        const x = city.x + dx;
        const y = city.y + dy;
        if (!inside(x, y)) continue;
        const i = indexOf(x, y);
        if (!prefectureMask[i] || sea[i]) continue;
        const d = Math.hypot(dx, dy);
        if (d > radius) continue;
        const urban = landuse[i] === 2 || landuse[i] === 3 || (allowSuburban && (landuse[i] === 4 || landuse[i] === 7 || landuse[i] === 8));
        if (urban || populationDensity[i] > 0.22) adminId[i] = bestAdmin;
      }
    }
  }
  for (const city of modernCities) {
    const radius = (city.population || 0) >= 500000
      ? clamp(17 + Math.sqrt(city.population) / 120, 20, 38)
      : clamp(5 + Math.sqrt(city.population || 70000) / 210, 6, 11);
    lockUrbanClusterToMunicipality(city, radius, true);
  }
  for (const sat of satelliteCities || []) {
    if (!prefectureMask[indexOf(sat.x, sat.y)]) continue;
    let bestAdmin = -1;
    if (sat.municipalityClass === "independentSatelliteMunicipality") {
      let bestD = INF;
      adminCentersRaw.forEach((center, id) => {
        if (!activeAdminIds.has(id)) return;
        const d = Math.hypot(center.x - sat.x, center.y - sat.y);
        if (d < bestD) { bestD = d; bestAdmin = id; }
      });
    } else if (inside(sat.parentX ?? -1, sat.parentY ?? -1)) {
      bestAdmin = adminId[indexOf(sat.parentX, sat.parentY)];
    }
    if (bestAdmin < 0) continue;
    sat.parentAdminHint = bestAdmin;
    const changed = expandSatelliteMunicipalityCatchment(adminId, sat, bestAdmin, {
      prefectureMask, sea, elevation, slope, river, ridgeField: boundaryRidgeField, valleyField, basinField, coastalLowland, flowAccum,
      landuse, populationDensity, roadInfluence, railInfluence2, stationInfluence, modernCities,
    });
    if (changed > 0 && sat.municipalityClass === "independentSatelliteMunicipality") adminDebug.satelliteMunicipalitiesExpanded++;
  }
  markChanged("changedAfterUrbanLock");
  lockSmallUrbanComponentsToMunicipality(adminId, prefectureMask, sea, landuse, populationDensity, 520);
  lockSmallUrbanComponentsToMunicipality(adminId, prefectureMask, sea, landuse, populationDensity, 620);
  markChanged("changedAfterSmallUrbanLock");
  const activeAdminCenters = () => adminCentersRaw.filter((_, id) => activeAdminIds.has(id));
  mergeTinyMunicipalities(adminId, prefectureMask, sea, populationDensity, modernCities, 120, { satelliteCities, satelliteStats: adminDebug, satelliteMinArea: 100, protectedPoints: activeAdminCenters() });
  markChanged("changedAfterInitialMerge");
  adminProgress?.({ status: "admin-step", regionId: adminRegionMeta.regionId, step: "topology cleanup" });
  removeMunicipalExclaves(adminId, prefectureMask, sea, adminCentersRaw, modernCities, 180);
  markChanged("changedAfterInitialExclaveRemoval");
  // The initial compartment graph assignment is now the primary natural partition.
  // Re-running the older raw landscape-unit pass here collapses lowland seeds into a few broad owners.
  markChanged("changedAfterLandscapePartition");
  adminProgress?.({ status: "admin-step", regionId: adminRegionMeta.regionId, step: "split oversized municipalities" });
  // The older oversized-lowland pass rebuilds natural compartments a second time.
  // The current pipeline already performs pending-seed lowland splitting on the active
  // compartment graph above, so keep the full admin layout while avoiding the duplicate
  // high-cost recomputation.
  const oversizedSplitDebug = {
    changedCells: 0,
    splitMunicipalities: 0,
    rejectedMunicipalities: 0,
    skippedDuplicateCompartmentRebuild: true,
    skippedForVisibleFragment: adminRegionMeta.isFocusedRegion === false && regionLandArea < 6500,
  };
  adminDebug.changedAfterOversizedRuralSplit = oversizedSplitDebug.changedCells;
  adminDebug.oversizedRuralMunicipalitiesSplit = oversizedSplitDebug.splitMunicipalities;
  adminDebug.oversizedRuralSplits = oversizedSplitDebug.splitMunicipalities;
  adminDebug.oversizedLowlandSplits = oversizedSplitDebug.splitMunicipalities;
  adminDebug.ruralSplitsAccepted = oversizedSplitDebug.splitMunicipalities;
  adminDebug.ruralSplitsRejected = oversizedSplitDebug.rejectedMunicipalities || 0;
  adminDebug.oversizedSplitSkippedForVisibleFragment = Boolean(oversizedSplitDebug.skippedForVisibleFragment);
  adminDebug.oversizedSplitSkippedDuplicateCompartmentRebuild = Boolean(oversizedSplitDebug.skippedDuplicateCompartmentRebuild);
  previousSnapshot = new Int16Array(adminId);
  adminProgress?.({ status: "admin-step", regionId: adminRegionMeta.regionId, step: "terrain snap" });
  snapAdminBoundariesToTerrain(adminId, prefectureMask, sea, elevation, slope, river, boundaryRidgeField, valleyField, flowAccum, populationDensity, landuse, adminCentersRaw, [...modernCities, ...satelliteCities, ...ports, ...industrialZones, ...logisticsParks], 2);
  markChanged("changedAfterSnap");
  removeMunicipalExclaves(adminId, prefectureMask, sea, adminCentersRaw, [...modernCities, ...activeAdminCenters()], 360);
  markChanged("changedAfterFinalExclaveRemoval");
  mergeTinyMunicipalities(adminId, prefectureMask, sea, populationDensity, modernCities, 80, { satelliteCities, satelliteStats: adminDebug, satelliteMinArea: 90, protectedPoints: activeAdminCenters() });
  markChanged("changedAfterFinalMerge");

  for (const sat of satelliteCities || []) {
    if (sat.municipalityClass !== "independentSatelliteMunicipality" || !inside(sat.x, sat.y)) continue;
    const targetAdmin = adminId[indexOf(sat.x, sat.y)];
    if (targetAdmin < 0) continue;
    expandSatelliteMunicipalityCatchment(adminId, sat, targetAdmin, {
      prefectureMask, sea, elevation, slope, river, ridgeField: boundaryRidgeField, valleyField, basinField, coastalLowland, flowAccum,
      landuse, populationDensity, roadInfluence, railInfluence2, stationInfluence, modernCities,
    });
  }
  removeMunicipalExclaves(adminId, prefectureMask, sea, adminCentersRaw, [...modernCities, ...activeAdminCenters()], 260);
  const finalPromotionDebug = promotePendingSeedsForMunicipalityCount(adminId, prefectureMask, sea, {
    plain, agriculture, basinField, coastalLowland, valleyField, ridgeField: boundaryRidgeField, slope, elevation,
  }, compartmentAssignment.compartments, adminCentersRaw, seedLifecycle, Math.min(22, targetMunicipalityCount));
  adminDebug.changedAfterFinalPendingSeedCountRepair = finalPromotionDebug.changedCells;
  adminDebug.pendingSeedsPromotedForCount += finalPromotionDebug.promotedSeeds;
  const restoredSeedDebug = restoreSurvivedSeedsByCompartment(adminId, prefectureMask, sea, compartmentAssignment.compartments, adminCentersRaw, seedLifecycle, Math.min(22, targetMunicipalityCount));
  adminDebug.changedAfterSurvivedSeedCompartmentRestore = restoredSeedDebug.changedCells;
  adminDebug.survivedSeedsRestoredByCompartment = restoredSeedDebug.restoredSeeds;
  let finalAreaBySeed = municipalityAreaById(adminId, prefectureMask, sea);
  for (const seedState of seedLifecycle) {
    seedState.area = finalAreaBySeed.get(seedState.id) || 0;
    if (!seedState.protected && seedState.state === "pending" && seedState.area < 25) seedState.state = "absorbed";
  }
  absorbSeedCompartments(adminId, compartmentAssignment.compartments, seedLifecycle);
  activeAdminIds = activeSeedIds(seedLifecycle);

  const areaById = municipalityAreaById(adminId, prefectureMask, sea);
  const satelliteAreas = [];
  (satelliteCities || []).forEach((sat, index) => {
    if (!inside(sat.x, sat.y) || !prefectureMask[indexOf(sat.x, sat.y)]) return;
    const id = adminId[indexOf(sat.x, sat.y)];
    const area = areaById.get(id) || 0;
    const key = sat.name || `satellite-${index}`;
    adminDebug.satelliteMunicipalityAreaByNameOrIndex[key] = area;
    if (sat.municipalityClass === "independentSatelliteMunicipality" && (area < Math.max(120, sat.satelliteMinArea || 0) || ((sat.population || 0) >= 60000 && area < 150))) {
      sat.municipalityClass = "smallTownAttachedToRuralMunicipality";
      adminDebug.satelliteMunicipalitiesTooSmall++;
      return;
    }
    if (sat.municipalityClass === "independentSatelliteMunicipality") {
      satelliteAreas.push(area);
      if (area < 80) adminDebug.satelliteMunicipalitiesTooSmall++;
    }
  });
  adminDebug.averageSatelliteMunicipalityArea = satelliteAreas.length ? satelliteAreas.reduce((sum, value) => sum + value, 0) / satelliteAreas.length : 0;
  adminDebug.minSatelliteMunicipalityArea = satelliteAreas.length ? Math.min(...satelliteAreas) : 0;
  adminDebug.satelliteMunicipalitiesIndependent = satelliteAreas.length;
  const landscapeDebug = applyLandscapeUnitAdminPartition.lastDebug || {};
  Object.assign(adminDebug, landscapeDebug);
  adminDebug.targetNaturalCompartmentCount = compartmentAssignment.debug?.targetNaturalCompartmentCount || targetCompartmentCount;
  adminDebug.naturalCompartmentCount = compartmentAssignment.debug?.naturalCompartmentCount || adminDebug.naturalCompartmentCount || adminDebug.compartmentCount || 0;
  adminDebug.compartmentCount = adminDebug.naturalCompartmentCount;
  adminDebug.averageCompartmentsPerMunicipality = compartmentAssignment.debug?.averageCompartmentsPerMunicipality || adminDebug.averageCompartmentsPerMunicipality || 0;
  adminDebug.singleCompartmentMunicipalityRatio = compartmentAssignment.debug?.singleCompartmentMunicipalityRatio ?? adminDebug.singleCompartmentMunicipalityRatio ?? 0;
  adminDebug.actualMunicipalityCount = new Set([...adminId].filter((id, i) => id >= 0 && prefectureMask[i] && !sea[i])).size;
  adminDebug.averageCompartmentsPerMunicipality = adminDebug.actualMunicipalityCount ? adminDebug.naturalCompartmentCount / adminDebug.actualMunicipalityCount : 0;
  adminDebug.survivedSeedCount = seedLifecycle.filter((seed) => seed.state === "survived").length;
  adminDebug.pendingSeedCount = seedLifecycle.filter((seed) => seed.state === "pending").length;
  adminDebug.absorbedSeedCount = seedLifecycle.filter((seed) => seed.state === "absorbed").length;
  adminDebug.finalMunicipalityCount = adminDebug.actualMunicipalityCount;
  adminDebug.finalTinyMunicipalityCount = [...areaById.values()].filter((area) => area > 0 && area < 8).length;
  adminDebug.seedLifecycle = seedLifecycle.map((seed) => ({ id: seed.id, state: seed.state, protected: seed.protected, area: seed.area }));
  adminDebug.borderNaturalBarrierAverage = adminDebug.finalBorderNaturalBarrierAverage ?? 0;
  adminDebug.voronoiLikeRate = adminDebug.voronoiLikeRateAfter ?? 0;
  adminProgress?.({ status: "admin-step", regionId: adminRegionMeta.regionId, step: "extract borders" });
  const adminBorders = extractAdminBorderSegments(adminId, prefectureMask);


  return { adminCentersRaw, adminId, adminBorders, adminDebug };
}


function filterPointsForMask(points = [], mask, sea) {
  return (points || [])
    .filter((p) => p && inside(p.x, p.y) && mask[indexOf(p.x, p.y)] && !sea[indexOf(p.x, p.y)])
    .map((p) => ({ ...p }));
}

function buildRegionMask(prefectureMask, prefectureRegionId, sea, regionId) {
  const mask = new Uint8Array(SIZE);
  for (let i = 0; i < SIZE; i++) {
    if (sea[i]) continue;
    mask[i] = adminGenerationRegionIdAt(i, prefectureMask, prefectureRegionId) === regionId ? 1 : 0;
  }
  return mask;
}

function maskLandArea(mask, sea) {
  let area = 0;
  for (let i = 0; i < SIZE; i++) if (mask[i] && !sea[i]) area++;
  return area;
}


function compactAdminIdsAndCenters(adminId, humanMask, sea, centers = [], fields = {}) {
  const activeIds = [...new Set([...adminId].filter((id, i) => id >= 0 && humanMask[i] && !sea[i]))].sort((a, b) => a - b);
  const idMap = new Map(activeIds.map((oldId, newId) => [oldId, newId]));
  const newAdminId = new Int16Array(SIZE);
  newAdminId.fill(-1);
  const cellsByNewId = Array.from({ length: activeIds.length }, () => []);
  for (let i = 0; i < SIZE; i++) {
    if (!humanMask[i] || sea[i]) continue;
    const newId = idMap.get(adminId[i]);
    if (newId === undefined) continue;
    newAdminId[i] = newId;
    cellsByNewId[newId].push(i);
  }

  const chooseOffice = (newId, oldId) => {
    const cells = cellsByNewId[newId] || [];
    const current = centers[oldId];
    if (current && inside(current.x, current.y)) {
      const ci = indexOf(current.x, current.y);
      if (newAdminId[ci] === newId && humanMask[ci] && !sea[ci]) {
        return { ...current, localAdminId: newId, oldAdminId: oldId, municipalityOffice: true };
      }
    }
    let sx = 0, sy = 0;
    for (const i of cells) {
      const [x, y] = xyOf(i);
      sx += x;
      sy += y;
    }
    const cx = cells.length ? sx / cells.length : current?.x || 0;
    const cy = cells.length ? sy / cells.length : current?.y || 0;
    let bestI = cells[0] ?? -1;
    let bestScore = -INF;
    for (const i of cells) {
      const [x, y] = xyOf(i);
      const land = fields.landuse?.[i] ?? 0;
      const urbanBonus = land === 3 ? 1.2 : land === 2 ? 1.0 : land === 4 || land === 7 || land === 8 ? 0.55 : land === 1 ? 0.24 : 0;
      const density = fields.populationDensity?.[i] || 0;
      const settlement = fields.settlementScore?.[i] || 0;
      const score =
        density * 2.25 +
        settlement * 0.75 +
        urbanBonus +
        (fields.plain?.[i] || 0) * 0.32 +
        (fields.basinField?.[i] || 0) * 0.24 +
        (fields.coastalLowland?.[i] || 0) * 0.18 +
        (fields.roadInfluence?.[i] || 0) * 0.34 +
        (fields.stationInfluence?.[i] || 0) * 0.45 -
        (fields.slope?.[i] || 0) * 0.52 -
        Math.hypot(x - cx, y - cy) * 0.018 +
        hash2(x, y, 91337 + newId) * 0.012;
      if (score > bestScore) { bestScore = score; bestI = i; }
    }
    const [bx, by] = bestI >= 0 ? xyOf(bestI) : [Math.round(cx), Math.round(cy)];
    return {
      ...(current || {}),
      x: bx,
      y: by,
      score: bestScore > -INF ? bestScore : 0,
      seedKind: current?.seedKind || "generatedMunicipalOffice",
      invisibleLowlandAdminSeed: current?.invisibleLowlandAdminSeed ?? true,
      localAdminId: newId,
      oldAdminId: oldId,
      municipalityOffice: true,
      generatedOfficePoint: !current || !inside(current.x, current.y) || newAdminId[indexOf(current.x, current.y)] !== newId,
    };
  };

  const adminCenters = activeIds.map((oldId, newId) => chooseOffice(newId, oldId));
  return {
    adminId: newAdminId,
    adminCenters,
    activeMunicipalityCount: activeIds.length,
    removedUnusedAdminCenterCount: Math.max(0, centers.length - activeIds.length),
    generatedOfficePointCount: adminCenters.filter((p) => p.generatedOfficePoint).length,
  };
}

function discoverAdminRegionIds(prefectureMask, prefectureRegionId, sea) {
  const ids = new Set();
  for (let i = 0; i < SIZE; i++) {
    if (sea[i]) continue;
    const id = adminGenerationRegionIdAt(i, prefectureMask, prefectureRegionId);
    if (id >= 0 || id === OUTER_ANCHOR_REGION_ID) ids.add(id);
  }
  return [...ids].sort((a, b) => a - b);
}

export function generateAdminLayout(context) {
  const { prefectureMask, prefectureRegionId, sea, populationDensity, plain, slope, adminProgress } = context;
  const minFullAdminRegionArea = 1500;
  const regionIds = discoverAdminRegionIds(prefectureMask, prefectureRegionId, sea)
    .filter((regionId) => regionId === 0 || (regionId !== OUTER_ANCHOR_REGION_ID && maskLandArea(buildRegionMask(prefectureMask, prefectureRegionId, sea, regionId), sea) >= minFullAdminRegionArea));

  if (!prefectureRegionId || regionIds.length <= 1) return generateAdminLayoutForMask(context);

  let combinedAdminId = new Int16Array(SIZE);
  combinedAdminId.fill(-1);
  const combinedHumanMask = new Uint8Array(SIZE);
  let combinedCenters = [];
  const combinedCompartmentBorders = [];
  const perRegion = [];
  let idOffset = 0;

  for (const regionId of regionIds) {
    const regionMask = buildRegionMask(prefectureMask, prefectureRegionId, sea, regionId);
    const regionArea = maskLandArea(regionMask, sea);
    if (regionId !== 0 && regionArea < minFullAdminRegionArea) continue;

    const localContext = {
      ...context,
      seed: (context.seed + regionId * 10007) >>> 0,
      prefectureMask: regionMask,
      modernCities: filterPointsForMask(context.modernCities, regionMask, sea),
      satelliteCities: filterPointsForMask(context.satelliteCities, regionMask, sea),
      newTowns: filterPointsForMask(context.newTowns, regionMask, sea),
      markets: filterPointsForMask(context.markets, regionMask, sea),
      villages: filterPointsForMask(context.villages, regionMask, sea),
      ports: filterPointsForMask(context.ports, regionMask, sea),
      stations: filterPointsForMask(context.stations, regionMask, sea),
      industrialZones: filterPointsForMask(context.industrialZones, regionMask, sea),
      logisticsParks: filterPointsForMask(context.logisticsParks, regionMask, sea),
      adminRegionMeta: {
        regionId,
        landArea: regionArea,
        isFocusedRegion: regionId === 0,
        isOuterAnchorRegion: regionId === OUTER_ANCHOR_REGION_ID,
      },
      adminProgress,
    };

    adminProgress?.({ status: "region-start", regionId, area: regionArea });
    const local = generateAdminLayoutForMask(localContext);
    adminProgress?.({ status: "region-done", regionId, area: regionArea, municipalities: local.adminDebug?.finalMunicipalityCount || local.adminDebug?.actualMunicipalityCount || 0 });
    if (local.adminDebug?.compartmentBorders?.length) combinedCompartmentBorders.push(...local.adminDebug.compartmentBorders);
    let localMaxAdminId = -1;
    for (let i = 0; i < SIZE; i++) if (regionMask[i] && !sea[i] && (local.adminId?.[i] ?? -1) > localMaxAdminId) localMaxAdminId = local.adminId[i];
    const localSlotCount = Math.max(local.adminCentersRaw?.length || 0, localMaxAdminId + 1);
    const localCenters = [];
    for (let localAdminId = 0; localAdminId < localSlotCount; localAdminId++) {
      let center = local.adminCentersRaw?.[localAdminId];
      if (!center) {
        let sx = 0, sy = 0, count = 0, bestI = -1, bestScore = -INF;
        for (let i = 0; i < SIZE; i++) {
          if (!regionMask[i] || sea[i] || local.adminId?.[i] !== localAdminId) continue;
          const [x, y] = xyOf(i);
          sx += x;
          sy += y;
          count++;
          const score = (populationDensity?.[i] || 0) + (plain?.[i] || 0) * 0.2 - (slope?.[i] || 0) * 0.2;
          if (score > bestScore) { bestScore = score; bestI = i; }
        }
        if (count && bestI >= 0) {
          const [bx, by] = xyOf(bestI);
          center = { x: bx, y: by, score: bestScore, seedKind: "generatedAdminSlot", invisibleLowlandAdminSeed: true };
        }
      }
      if (!center) center = { x: 0, y: 0, score: 0, seedKind: "emptyAdminSlot", invisibleLowlandAdminSeed: true };
      localCenters.push({
        ...center,
        regionId,
        localAdminId,
        adminIdOffset: idOffset,
      });
    }
    combinedCenters.push(...localCenters);

    for (let i = 0; i < SIZE; i++) {
      if (!regionMask[i] || sea[i]) continue;
      combinedHumanMask[i] = 1;
      const localId = local.adminId?.[i] ?? -1;
      if (localId >= 0) combinedAdminId[i] = localId + idOffset;
    }

    perRegion.push({
      regionId,
      area: regionArea,
      centerCount: localCenters.length,
      municipalityCount: local.adminDebug?.finalMunicipalityCount || local.adminDebug?.actualMunicipalityCount || new Set([...local.adminId].filter((id, i) => id >= 0 && regionMask[i] && !sea[i])).size,
      naturalCompartmentCount: local.adminDebug?.naturalCompartmentCount || 0,
      targetNaturalCompartmentCount: local.adminDebug?.targetNaturalCompartmentCount || 0,
      averageCompartmentArea: local.adminDebug?.averageCompartmentArea || 0,
      maxCompartmentArea: local.adminDebug?.maxCompartmentArea || 0,
      maxCompartmentElongation: local.adminDebug?.maxCompartmentElongation || 1,
      worstNaturalCompartments: local.adminDebug?.worstNaturalCompartments || [],
      singleCompartmentMunicipalityRatio: local.adminDebug?.singleCompartmentMunicipalityRatio || 0,
    });
    idOffset += localSlotCount;
  }

  const leftoverByRegion = new Map();
  for (let i = 0; i < SIZE; i++) {
    if (sea[i]) continue;
    const regionId = adminGenerationRegionIdAt(i, prefectureMask, prefectureRegionId);
    if ((regionId < 0 && regionId !== OUTER_ANCHOR_REGION_ID) || combinedAdminId[i] >= 0) continue;
    if (!leftoverByRegion.has(regionId)) leftoverByRegion.set(regionId, []);
    leftoverByRegion.get(regionId).push(i);
  }
  for (const [regionId, cells] of leftoverByRegion) {
    let sx = 0, sy = 0, bestI = cells[0], bestScore = -INF;
    for (const i of cells) {
      const [x, y] = xyOf(i);
      sx += x;
      sy += y;
      const score = (populationDensity?.[i] || 0) + (plain?.[i] || 0) * 0.2 - (slope?.[i] || 0) * 0.2;
      if (score > bestScore) { bestScore = score; bestI = i; }
    }
    const [cx, cy] = xyOf(bestI);
    const id = combinedCenters.length;
    combinedCenters.push({ x: cx, y: cy, score: bestScore, regionId, localAdminId: 0, seedKind: "tinyRegionAdminSeed", invisibleLowlandAdminSeed: true });
    for (const i of cells) {
      combinedHumanMask[i] = 1;
      combinedAdminId[i] = id;
    }
    perRegion.push({ regionId, area: cells.length, centerCount: 1, municipalityCount: 1, naturalCompartmentCount: 1, targetNaturalCompartmentCount: 1, averageCompartmentArea: cells.length, maxCompartmentArea: cells.length, maxCompartmentElongation: 1, singleCompartmentMunicipalityRatio: 1, tinyRegionFallback: true });
  }

  const compactedAdmin = compactAdminIdsAndCenters(combinedAdminId, combinedHumanMask, sea, combinedCenters, {
    populationDensity,
    plain,
    slope,
    settlementScore: context.settlementScore,
    landuse: context.landuse,
    basinField: context.basinField,
    coastalLowland: context.coastalLowland,
    roadInfluence: context.roadInfluence,
    stationInfluence: context.stationInfluence,
  });
  combinedAdminId = compactedAdmin.adminId;
  combinedCenters = compactedAdmin.adminCenters;
  const adminBorders = extractAdminBorderSegments(combinedAdminId, combinedHumanMask);
  const totalMunicipalityCount = compactedAdmin.activeMunicipalityCount;
  const totalNaturalCompartmentCount = perRegion.reduce((sum, row) => sum + (row.naturalCompartmentCount || 0), 0);
  const totalTargetNaturalCompartmentCount = perRegion.reduce((sum, row) => sum + (row.targetNaturalCompartmentCount || 0), 0);
  const weightedCompartmentArea = perRegion.reduce((sum, row) => sum + (row.averageCompartmentArea || 0) * (row.naturalCompartmentCount || 0), 0);
  const weightedSingleRatio = perRegion.reduce((sum, row) => sum + (row.singleCompartmentMunicipalityRatio || 0) * (row.municipalityCount || 0), 0);
  const adminDebug = {
    multiRegionAdmin: true,
    adminRegionCount: perRegion.length,
    minFullAdminRegionArea,
    perRegion,
    finalMunicipalityCount: totalMunicipalityCount,
    actualMunicipalityCount: totalMunicipalityCount,
    candidateSeedCount: combinedCenters.length,
    municipalOfficePointCount: combinedCenters.length,
    generatedOfficePointCount: compactedAdmin.generatedOfficePointCount,
    removedUnusedAdminCenterCount: compactedAdmin.removedUnusedAdminCenterCount,
    naturalCompartmentCount: totalNaturalCompartmentCount,
    compartmentCount: totalNaturalCompartmentCount,
    targetNaturalCompartmentCount: totalTargetNaturalCompartmentCount,
    averageCompartmentArea: totalNaturalCompartmentCount ? weightedCompartmentArea / totalNaturalCompartmentCount : 0,
    maxCompartmentArea: Math.max(0, ...perRegion.map((row) => row.maxCompartmentArea || 0)),
    maxCompartmentElongation: Math.max(1, ...perRegion.map((row) => row.maxCompartmentElongation || 1)),
    averageCompartmentsPerMunicipality: totalMunicipalityCount ? totalNaturalCompartmentCount / totalMunicipalityCount : 0,
    singleCompartmentMunicipalityRatio: totalMunicipalityCount ? weightedSingleRatio / totalMunicipalityCount : 0,
    compartmentBorders: combinedCompartmentBorders,
  };

  return { adminCentersRaw: combinedCenters, adminId: combinedAdminId, adminBorders, adminDebug };
}