/** Geometry shared by independent partitions, saved room drafts and columns. */
import { difference, union } from 'polyclip-ts';
import { polygonArea } from './logic';
import { wallCmToUnits } from './wall-thickness';
import type {
  PartitionCfg, RoomDraftCfg, SpaceModel, WallColumnCfg,
} from './types';

export const COLUMN_MIN_CM = 1;
export const COLUMN_MAX_CM = 150;

export function clampColumnCm(cm: number): number {
  if (!Number.isFinite(cm)) return COLUMN_MIN_CM;
  return Math.max(COLUMN_MIN_CM, Math.min(COLUMN_MAX_CM, cm));
}

/** Square columns are symmetric every quarter turn. */
export function canonicalColumnAngle(angle: number | null | undefined): number {
  const a = Number.isFinite(Number(angle)) ? Number(angle) : 0;
  return ((a % 90) + 90) % 90;
}

const closedRing = (poly: number[][]): number[][][] => {
  const ring = poly.map((p) => [p[0], p[1]]);
  if (ring.length && (ring[0][0] !== ring[ring.length - 1][0]
      || ring[0][1] !== ring[ring.length - 1][1])) ring.push([...ring[0]]);
  return [ring];
};

export function polyclipPathD(geom: any): string {
  const out: string[] = [];
  for (const poly of geom || []) for (const ring of poly || []) {
    const pts = (ring || []).filter((p: any) => Array.isArray(p) && p.length >= 2);
    if (pts.length < 4) continue;
    out.push(`M ${pts.slice(0, -1).map((p: number[]) => `${p[0]} ${p[1]}`).join(' L ')} Z`);
  }
  return out.join(' ');
}

/** A wall segment has flat ends. Joining is delegated to polygon union. */
export function partitionBody(
  a: number[], b: number[], cm: number, cellCm: number, gridPitch: number,
): number[][] | null {
  const dx = b[0] - a[0], dy = b[1] - a[1];
  const len = Math.hypot(dx, dy);
  if (!(len > 1e-9)) return null;
  const half = wallCmToUnits(cm, cellCm, gridPitch) / 2;
  const nx = (-dy / len) * half, ny = (dx / len) * half;
  return [
    [a[0] + nx, a[1] + ny], [b[0] + nx, b[1] + ny],
    [b[0] - nx, b[1] - ny], [a[0] - nx, a[1] - ny],
  ];
}

export function columnBody(
  column: WallColumnCfg, cellCm: number, gridPitch: number,
): number[][] {
  const cell = Number(cellCm) > 0 ? Number(cellCm) : 5;
  const size = (clampColumnCm(column.cm) / cell) * gridPitch;
  const cx = column.center[0], cy = column.center[1];
  if (column.shape === 'circle') {
    const r = size / 2;
    return Array.from({ length: 96 }, (_, i) => {
      const a = (i / 96) * Math.PI * 2;
      return [cx + Math.cos(a) * r, cy + Math.sin(a) * r];
    });
  }
  const h = size / 2;
  const angle = canonicalColumnAngle(column.angle) * Math.PI / 180;
  const c = Math.cos(angle), s = Math.sin(angle);
  return [[-h, -h], [h, -h], [h, h], [-h, h]].map(([x, y]) =>
    [cx + x * c - y * s, cy + x * s + y * c]);
}

export function draftBodies(
  draft: RoomDraftCfg, cellCm: number, gridPitch: number,
): number[][][] {
  const out: number[][][] = [];
  for (let i = 0; i + 1 < draft.points.length; i++) {
    const body = partitionBody(
      draft.points[i], draft.points[i + 1], draft.segments[i]?.cm || 15,
      cellCm, gridPitch,
    );
    if (body) out.push(body);
  }
  return out;
}

export function physicalBodies(
  space: Pick<SpaceModel, 'partitions' | 'room_drafts' | 'wall_columns'>,
  cellCm: number,
  gridPitch: number,
): number[][][] {
  const out: number[][][] = [];
  for (const p of space.partitions || []) {
    const body = partitionBody(p.a, p.b, p.cm, cellCm, gridPitch);
    if (body) out.push(body);
  }
  for (const d of space.room_drafts || []) out.push(...draftBodies(d, cellCm, gridPitch));
  for (const c of space.wall_columns || []) out.push(columnBody(c, cellCm, gridPitch));
  return out;
}

export function unionBodies(bodies: number[][][]): any | null {
  try {
    const polygons = bodies.filter((body) => body.length >= 3).map((body) => closedRing(body));
    return polygons.length ? union(polygons[0] as any, ...polygons.slice(1) as any[]) : null;
  } catch {
    return null;
  }
}

export function physicalBodiesPath(bodies: number[][][]): string {
  const geom = unionBodies(bodies);
  if (geom) return polyclipPathD(geom);
  return bodies.map((body) =>
    `M ${body.map((p) => `${p[0]} ${p[1]}`).join(' L ')} Z`).join(' ');
}

/** Subtract only the physical bodies which overlap a room's clean floor. */
export function floorMinusBodies(floor: number[][], bodies: number[][][]): any {
  if (!bodies.length) return [closedRing(floor)];
  try {
    const obstacles = unionBodies(bodies);
    if (obstacles) return difference(closedRing(floor) as any, obstacles);
  } catch {
    // Fall through to the lossless sequential path below.
  }
  // A pathological multi-union must not restore the floor under masonry.
  // Sequential difference preserves overlap semantics and lets one malformed
  // body be skipped without discarding every valid neighbour.
  let geom: any = [closedRing(floor)];
  for (const body of bodies) {
    if (body.length < 3) continue;
    try { geom = difference(geom, closedRing(body) as any); } catch { /* skip invalid body */ }
  }
  return geom;
}

export function geometryArea(geom: any): number {
  let area = 0;
  for (const poly of geom || []) {
    if (!poly?.length) continue;
    area += polygonArea(poly[0] || []);
    for (let i = 1; i < poly.length; i++) area -= polygonArea(poly[i] || []);
  }
  return Math.max(0, area);
}

export function geometryOuterRings(geom: any): number[][][] {
  const out: number[][][] = [];
  for (const poly of geom || []) {
    const ring = poly?.[0];
    if (ring?.length >= 4) out.push(ring.slice(0, -1).map((p: number[]) => [p[0], p[1]]));
  }
  return out;
}

function convexHull(points: number[][]): number[][] {
  const p = [...points].sort((a, b) => a[0] - b[0] || a[1] - b[1]);
  if (p.length <= 2) return p;
  const cross = (o: number[], a: number[], b: number[]) =>
    (a[0] - o[0]) * (b[1] - o[1]) - (a[1] - o[1]) * (b[0] - o[0]);
  const lower: number[][] = [];
  for (const q of p) {
    while (lower.length >= 2 && cross(lower[lower.length - 2], lower[lower.length - 1], q) <= 0) lower.pop();
    lower.push(q);
  }
  const upper: number[][] = [];
  for (let i = p.length - 1; i >= 0; i--) {
    const q = p[i];
    while (upper.length >= 2 && cross(upper[upper.length - 2], upper[upper.length - 1], q) <= 0) upper.pop();
    upper.push(q);
  }
  return lower.slice(0, -1).concat(upper.slice(0, -1));
}

/** Opaque bodies extruded along parallel light travel (sun shafts). */
export function directionalOccluders(
  bodies: number[][][], dir: number[], length: number,
): number[][][] {
  if (!(length > 0)) return bodies;
  return bodies.map((body) => convexHull([
    ...body,
    ...body.map((p) => [p[0] + dir[0] * length, p[1] + dir[1] * length]),
  ])).filter((p) => p.length >= 3);
}

/** Approximate the hard shadow cast by each body away from a point source. */
export function radialOccluders(
  bodies: number[][][], source: number[], radius: number,
): number[][][] {
  if (!(radius > 0)) return [];
  const boundaryEps = Math.max(1e-9, radius * 1e-9);
  const onBoundary = (body: number[][]): boolean => body.some((a, i) => {
    const b = body[(i + 1) % body.length];
    const dx = b[0] - a[0], dy = b[1] - a[1];
    const len2 = dx * dx + dy * dy;
    if (!(len2 > 0)) return Math.hypot(source[0] - a[0], source[1] - a[1]) <= boundaryEps;
    const t = Math.max(0, Math.min(1,
      ((source[0] - a[0]) * dx + (source[1] - a[1]) * dy) / len2));
    return Math.hypot(source[0] - (a[0] + t * dx), source[1] - (a[1] + t * dy))
      <= boundaryEps;
  });
  // A misplaced source inside/on masonry is invalid input. Cover its entire
  // pool so it cannot illuminate through the body in any direction.
  if (bodies.some((body) => pointInPhysicalBody(source, body) || onBoundary(body))) {
    return [Array.from({ length: 128 }, (_, i) => {
      const a = (i / 128) * Math.PI * 2;
      return [source[0] + Math.cos(a) * radius * 1.01,
        source[1] + Math.sin(a) * radius * 1.01];
    })];
  }
  const out: number[][][] = [];
  for (const body of bodies) {
    if (body.length < 2) continue;
    out.push(body);
    // One quad per edge. Its far chord is deliberately pushed beyond the
    // glow circle even for an edge subtending almost 180°; a single hull with
    // a fixed projection distance lets that chord cut back through the pool.
    for (let i = 0; i < body.length; i++) {
      const a = body[i], b = body[(i + 1) % body.length];
      const ax = a[0] - source[0], ay = a[1] - source[1];
      const bx = b[0] - source[0], by = b[1] - source[1];
      const da = Math.hypot(ax, ay), db = Math.hypot(bx, by);
      if (!(da > boundaryEps) || !(db > boundaryEps)) continue;
      const cosTheta = Math.max(-1, Math.min(1, (ax * bx + ay * by) / (da * db)));
      const halfCos = Math.sqrt(Math.max(0, (1 + cosTheta) / 2));
      const far = Math.max(radius * 2, (radius * 1.02) / Math.max(halfCos, 1e-3));
      const pa = [source[0] + (ax / da) * far, source[1] + (ay / da) * far];
      const pb = [source[0] + (bx / db) * far, source[1] + (by / db) * far];
      out.push([a, b, pb, pa]);
    }
  }
  return out;
}

export function pointInPhysicalBody(point: number[], body: number[][]): boolean {
  let inside = false;
  for (let i = 0, j = body.length - 1; i < body.length; j = i++) {
    const xi = body[i][0], yi = body[i][1], xj = body[j][0], yj = body[j][1];
    const crosses = ((yi > point[1]) !== (yj > point[1]))
      && point[0] < ((xj - xi) * (point[1] - yi)) / ((yj - yi) || 1e-12) + xi;
    if (crosses) inside = !inside;
  }
  return inside;
}

export function sameColumnPlacement(a: WallColumnCfg, b: WallColumnCfg, eps: number): boolean {
  if (Math.hypot(a.center[0] - b.center[0], a.center[1] - b.center[1]) > eps) return false;
  if (Math.abs(clampColumnCm(a.cm) - clampColumnCm(b.cm)) > 1e-6) return false;
  if (a.shape !== b.shape) return true; // same outer body, different primitive
  if (a.shape === 'circle' || b.shape === 'circle') return true;
  const diff = Math.abs(canonicalColumnAngle(a.angle) - canonicalColumnAngle(b.angle));
  return Math.min(diff, 90 - diff) <= 1e-6;
}