import { MAP_H, MAP_W, SIZE } from "./mapUtils.js";

const EMPTY_ARRAY_KEYS = new Set([
  "villages", "markets", "castles", "ports", "modernCities", "satelliteCities", "stations",
  "interchanges", "industrialZones", "logisticsParks", "newTowns", "adminCenters",
  "premodernRoads", "minorRoads", "nationalRoads", "ringRoads", "externalRoads",
  "railways", "branchRailways", "ringRailways", "externalRailways", "expressways", "externalExpressways",
  "mainRivers", "tributaryRivers", "smallStreams", "prefectureBorder", "regionalPrefectureBorders",
  "adminBorders", "externalGateways", "prefectureRegions",
]);

const PATH_ARRAY_KEYS = new Set([
  "premodernRoads", "minorRoads", "nationalRoads", "ringRoads", "externalRoads",
  "railways", "branchRailways", "ringRailways", "externalRailways", "expressways", "externalExpressways",
  "mainRivers", "tributaryRivers", "smallStreams",
]);

const SEGMENT_ARRAY_KEYS = new Set([
  "prefectureBorder", "regionalPrefectureBorders", "adminBorders",
]);

const POINT_ARRAY_KEYS = new Set([
  "villages", "markets", "castles", "ports", "modernCities", "satelliteCities", "stations",
  "interchanges", "industrialZones", "logisticsParks", "newTowns", "adminCenters",
  "externalGateways", "prefectureRegions",
]);

const NEGATIVE_ONE_FIELDS = new Set([
  "adminId",
  "prefectureRegionId",
  "regionId",
  "municipalityId",
  "naturalCompartmentId",
  "watershedId",
]);

function isCellField(value) {
  return ArrayBuffer.isView(value) && typeof value.length === "number" && value.length === SIZE;
}

function defaultForField(name, Constructor) {
  if (name === "sea") return 1;
  if (name === "elevation") return 0.08;
  if (NEGATIVE_ONE_FIELDS.has(name)) return -1;
  if (Constructor === Float32Array || Constructor === Float64Array) return 0;
  return 0;
}

function worldIndex(world, x, y) {
  if (!world || x < 0 || y < 0 || x >= world.width || y >= world.height) return -1;
  return y * world.width + x;
}

function copyViewportField(name, source, world, camera, viewWidth, viewHeight) {
  const Constructor = source.constructor;
  const out = new Constructor(viewWidth * viewHeight);
  const fallback = defaultForField(name, Constructor);
  if (fallback !== 0) out.fill(fallback);

  const cx = Math.round(camera.x || 0);
  const cy = Math.round(camera.y || 0);
  for (let y = 0; y < viewHeight; y++) {
    for (let x = 0; x < viewWidth; x++) {
      const src = worldIndex(world, cx + x, cy + y);
      if (src >= 0) out[y * viewWidth + x] = source[src];
    }
  }
  return out;
}

function inViewportPoint(p, margin = 0, viewWidth = MAP_W, viewHeight = MAP_H) {
  return p && p.x >= -margin && p.y >= -margin && p.x < viewWidth + margin && p.y < viewHeight + margin;
}

function transformPointObject(point, camera, originX, originY) {
  if (!point || !Number.isFinite(point.x) || !Number.isFinite(point.y)) return null;
  return {
    ...point,
    x: point.x + originX - camera.x,
    y: point.y + originY - camera.y,
    worldX: point.x + originX,
    worldY: point.y + originY,
  };
}

function transformPointArray(items, camera, originX, originY, margin = 36, preserveIndexes = false, viewWidth = MAP_W, viewHeight = MAP_H) {
  const mapped = (items || []).map((item) => transformPointObject(item, camera, originX, originY));
  return preserveIndexes ? mapped : mapped.filter((item) => inViewportPoint(item, margin, viewWidth, viewHeight));
}

function transformTuple(tuple, camera, originX, originY) {
  if (!Array.isArray(tuple) || tuple.length < 2) return null;
  return [tuple[0] + originX - camera.x, tuple[1] + originY - camera.y];
}

function tupleInside(tuple, margin = 0, viewWidth = MAP_W, viewHeight = MAP_H) {
  return tuple && tuple[0] >= -margin && tuple[1] >= -margin && tuple[0] < viewWidth + margin && tuple[1] < viewHeight + margin;
}

function splitTransformedPath(path, camera, originX, originY, margin = 0, viewWidth = MAP_W, viewHeight = MAP_H) {
  const chunks = [];
  let current = [];
  for (const tuple of path || []) {
    const p = transformTuple(tuple, camera, originX, originY);
    const inside = tupleInside(p, margin, viewWidth, viewHeight);
    if (inside) {
      current.push([Math.round(p[0]), Math.round(p[1])]);
    } else if (current.length >= 2) {
      chunks.push(current);
      current = [];
    } else {
      current = [];
    }
  }
  if (current.length >= 2) chunks.push(current);
  return chunks;
}

function transformPaths(paths, camera, originX, originY, viewWidth = MAP_W, viewHeight = MAP_H) {
  const out = [];
  for (const path of paths || []) out.push(...splitTransformedPath(path, camera, originX, originY, 0, viewWidth, viewHeight));
  return out;
}

function segmentIntersectsViewport(seg, margin = 4, viewWidth = MAP_W, viewHeight = MAP_H) {
  if (!seg || seg.length < 2) return false;
  const xs = [seg[0][0], seg[1][0]];
  const ys = [seg[0][1], seg[1][1]];
  return Math.max(...xs) >= -margin && Math.min(...xs) <= viewWidth + margin && Math.max(...ys) >= -margin && Math.min(...ys) <= viewHeight + margin;
}

function transformSegments(segments, camera, originX, originY, viewWidth = MAP_W, viewHeight = MAP_H) {
  return (segments || [])
    .map((seg) => [transformTuple(seg?.[0], camera, originX, originY), transformTuple(seg?.[1], camera, originX, originY)])
    .filter((seg) => segmentIntersectsViewport(seg, 4, viewWidth, viewHeight));
}


function copySourceMapViewportField(source, camera, originX, originY, viewWidth, viewHeight) {
  if (!ArrayBuffer.isView(source) || typeof source.length !== "number" || source.length !== SIZE) return source;
  const out = new source.constructor(viewWidth * viewHeight);
  const cx = Math.round(camera.x || 0);
  const cy = Math.round(camera.y || 0);
  for (let y = 0; y < viewHeight; y++) {
    for (let x = 0; x < viewWidth; x++) {
      const sx = cx + x - originX;
      const sy = cy + y - originY;
      if (sx >= 0 && sy >= 0 && sx < MAP_W && sy < MAP_H) out[y * viewWidth + x] = source[sy * MAP_W + sx];
    }
  }
  return out;
}

function transformTransportDebug(debug, camera, originX, originY, viewport = null, viewWidth = MAP_W, viewHeight = MAP_H) {
  if (!debug?.layers) return debug;
  const layers = { ...debug.layers };
  for (const [key, value] of Object.entries(layers)) {
    if (ArrayBuffer.isView(value) && value.length === SIZE) layers[key] = copySourceMapViewportField(value, camera, originX, originY, viewWidth, viewHeight);
  }
  // The original transport-debug potential layers are fixed-map arrays.  Once the
  // viewport pans into patched world cells, synthesize equivalent viewport-sized
  // debug fields from the current world-backed fields so the color overlay moves
  // with the terrain instead of staying tied to the initial source map.
  if (viewport) {
    const n = viewWidth * viewHeight;
    const make = (fn) => {
      const out = new Float32Array(n);
      for (let i = 0; i < n; i++) out[i] = fn(i);
      return out;
    };
    const sea = viewport.sea || new Uint8Array(n);
    const slope = viewport.slope || new Float32Array(n);
    const plain = viewport.plain || new Float32Array(n);
    const pop = viewport.populationDensity || viewport.settlementScore || new Float32Array(n);
    const road = viewport.roadInfluence || new Float32Array(n);
    const rail = viewport.railInfluence2 || viewport.stationInfluence || new Float32Array(n);
    layers.expresswayPotential = make((i) => sea[i] ? 0 : Math.max(0, Math.min(1, road[i] * 0.72 + pop[i] * 0.42 + plain[i] * 0.22 - slope[i] * 0.52)));
    layers.nationalRoadPotential = make((i) => sea[i] ? 0 : Math.max(0, Math.min(1, road[i] * 0.58 + pop[i] * 0.55 + plain[i] * 0.18 - slope[i] * 0.38)));
    layers.railPotential = make((i) => sea[i] ? 0 : Math.max(0, Math.min(1, rail[i] * 0.72 + pop[i] * 0.38 + plain[i] * 0.26 - slope[i] * 0.72)));
    layers.slopeSeaPenalty = make((i) => sea[i] ? 1 : Math.max(0, Math.min(1, slope[i] * 1.35)));
  }
  if (Array.isArray(layers.components)) {
    layers.components = layers.components.map((component) => ({
      ...component,
      cells: (component.cells || [])
        .map((cell) => transformTuple(cell, camera, originX, originY))
        .filter((cell) => tupleInside(cell, 0, viewWidth, viewHeight))
        .map(([x, y]) => [Math.round(x), Math.round(y)]),
    })).filter((component) => component.cells.length);
  }
  if (Array.isArray(layers.repairedSegments)) {
    layers.repairedSegments = layers.repairedSegments.flatMap((repair) => transformPaths([repair.path || []], camera, originX, originY, viewWidth, viewHeight).map((path) => ({ ...repair, path })));
  }
  if (Array.isArray(layers.unservedSettlements)) layers.unservedSettlements = transformPointArray(layers.unservedSettlements, camera, originX, originY, 36, false, viewWidth, viewHeight);
  return { ...debug, layers };
}

function buildEmptyViewportFromSource(sourceMap, world, camera, viewWidth, viewHeight) {
  const viewport = { ...sourceMap };
  viewport.width = viewWidth;
  viewport.height = viewHeight;
  viewport.worldCamera = { x: camera.x, y: camera.y };
  viewport.worldOrigin = { x: world.originX, y: world.originY };
  viewport.generatedRects = world.generatedRects || [];
  for (const key of EMPTY_ARRAY_KEYS) if (Array.isArray(viewport[key])) viewport[key] = [];
  return viewport;
}

export function getViewportMap(world, camera, viewWidth = MAP_W, viewHeight = MAP_H, options = {}) {
  const sourceMap = world?.sourceMap || {};
  const normalizedCamera = {
    x: Math.round(camera?.x || 0),
    y: Math.round(camera?.y || 0),
  };
  const viewport = buildEmptyViewportFromSource(sourceMap, world, normalizedCamera, viewWidth, viewHeight);

  for (const [name, value] of Object.entries(world?.fields || {})) {
    viewport[name] = copyViewportField(name, value, world, normalizedCamera, viewWidth, viewHeight);
  }

  if (options.light) {
    // Light/fast redraws are used while panning and zooming.  Do not leave
    // source-space debug vectors on the viewport; in borders-debug this made
    // natural compartment lines appear fixed on screen while the map moved.
    viewport.adminDebug = null;
    viewport.transportDebug = null;
    return viewport;
  }

  const originX = world?.originX || 0;
  const originY = world?.originY || 0;
  for (const key of POINT_ARRAY_KEYS) {
    if (!Array.isArray(sourceMap[key])) continue;
    viewport[key] = transformPointArray(sourceMap[key], normalizedCamera, originX, originY, 36, key === "adminCenters", viewWidth, viewHeight);
  }
  for (const key of PATH_ARRAY_KEYS) if (Array.isArray(sourceMap[key])) viewport[key] = transformPaths(sourceMap[key], normalizedCamera, originX, originY, viewWidth, viewHeight);
  for (const key of SEGMENT_ARRAY_KEYS) if (Array.isArray(sourceMap[key])) viewport[key] = transformSegments(sourceMap[key], normalizedCamera, originX, originY, viewWidth, viewHeight);

  if (sourceMap.adminDebug) {
    viewport.adminDebug = {
      ...sourceMap.adminDebug,
      compartmentBorders: transformSegments(sourceMap.adminDebug.compartmentBorders || [], normalizedCamera, originX, originY, viewWidth, viewHeight),
      lowlandAdminSeeds: transformPointArray(sourceMap.adminDebug.lowlandAdminSeeds || [], normalizedCamera, originX, originY, 36, false, viewWidth, viewHeight),
    };
  }
  if (sourceMap.transportDebug) viewport.transportDebug = transformTransportDebug(sourceMap.transportDebug, normalizedCamera, originX, originY, viewport, viewWidth, viewHeight);
  if (sourceMap.neighborPrefectureDetails) {
    viewport.neighborPrefectureDetails = {
      ...sourceMap.neighborPrefectureDetails,
      cities: transformPointArray(sourceMap.neighborPrefectureDetails.cities || [], normalizedCamera, originX, originY, 36, false, viewWidth, viewHeight),
      adminCenters: transformPointArray(sourceMap.neighborPrefectureDetails.adminCenters || [], normalizedCamera, originX, originY, 36, false, viewWidth, viewHeight),
      roads: transformPaths(sourceMap.neighborPrefectureDetails.roads || [], normalizedCamera, originX, originY, viewWidth, viewHeight),
    };
  }

  return viewport;
}