/**
 * World Trace Placement — places ruins and markers from past runs
 *
 * GDD (Law of Trace): "Nothing disappears without a trace;
 * each cycle leaves an imprint in the next."
 *
 * When generating a new world, we check for traces from past runs
 * in the same biome (from the current and previous great cycle).
 * Death sites become ruin markers; discovery sites become faded experiment traces.
 */

import { addEntity, addComponent } from 'bitecs';
import type { World } from '../ecs/world';
import { Position, SpriteRef, WorldTrace, TraceType } from '../ecs/components';
import type { BiomeData } from './types';
import type { RunTrace, GreatCycleState } from '../run/types';
import { getTracesForBiome, getDeathTraces } from '../run/cycle';

/** String data for a world trace entity (not stored in ECS — numeric only there) */
export interface WorldTraceInfo {
  /** Entity ID */
  eid: number;
  /** Type of trace */
  traceType: 'death_site' | 'discovery_site';
  /** Run that left this trace */
  sourceRunId: number;
  /** School used in that run */
  schoolId: string;
  /** Key elements discovered (for discovery sites) */
  keyElements: string[];
  /** Tile position */
  tileX: number;
  tileY: number;
}

/** Visual config for trace markers */
const TRACE_CONFIG = {
  death_site: {
    color: 0x884444,     // dark red — blood/decay
    radius: 6,
    interactRange: 40,
    glowColor: 0xaa3333, // red glow
  },
  discovery_site: {
    color: 0x446688,     // blue-gray — knowledge
    radius: 5,
    interactRange: 36,
    glowColor: 0x4488aa, // blue glow
  },
} as const;

/**
 * Spawn world trace entities from past run traces.
 *
 * For each trace from the current/previous cycle in this biome:
 * - Death sites: place a ruin marker at the death position
 * - Remaining traces: place discovery markers at a position derived from
 *   the run's world seed (since we don't store exact discovery locations)
 *
 * @returns Array of WorldTraceInfo for display/interaction
 */
export function spawnWorldTraces(
  world: World,
  cycleState: GreatCycleState,
  biomeId: string,
  biome: BiomeData,
): WorldTraceInfo[] {
  const traces = getTracesForBiome(cycleState, biomeId);
  if (traces.length === 0) return [];

  const result: WorldTraceInfo[] = [];
  const tileSize = biome.tileSize;
  const mapW = biome.mapWidth;
  const mapH = biome.mapHeight;

  // Place death site markers
  const deathTraces = getDeathTraces(traces);
  for (const trace of deathTraces) {
    const pos = trace.deathPosition;
    if (!pos) continue;

    // Clamp to map bounds
    const tx = Math.max(0, Math.min(pos.tileX, mapW - 1));
    const ty = Math.max(0, Math.min(pos.tileY, mapH - 1));

    const eid = createTraceEntity(
      world, tx, ty, tileSize,
      TraceType.DeathSite, trace.runId,
      TRACE_CONFIG.death_site,
    );

    result.push({
      eid,
      traceType: 'death_site',
      sourceRunId: trace.runId,
      schoolId: trace.schoolId,
      keyElements: trace.keyElements,
      tileX: tx,
      tileY: ty,
    });
  }

  // Place discovery markers for traces with significant discoveries
  // (Only for traces without death sites, to avoid double-marking)
  const deathRunIds = new Set(deathTraces.map(t => t.runId));
  const discoveryTraces = traces.filter(
    t => !deathRunIds.has(t.runId) && t.discoveryCount >= 3,
  );

  for (const trace of discoveryTraces) {
    // Derive a position from the run's seed (deterministic but varied)
    const tx = deriveTracePosition(trace.worldSeed, 0, mapW);
    const ty = deriveTracePosition(trace.worldSeed, 1, mapH);

    const eid = createTraceEntity(
      world, tx, ty, tileSize,
      TraceType.DiscoverySite, trace.runId,
      TRACE_CONFIG.discovery_site,
    );

    result.push({
      eid,
      traceType: 'discovery_site',
      sourceRunId: trace.runId,
      schoolId: trace.schoolId,
      keyElements: trace.keyElements,
      tileX: tx,
      tileY: ty,
    });
  }

  return result;
}

/** Create a single trace entity with position, sprite, and trace component */
function createTraceEntity(
  world: World,
  tileX: number,
  tileY: number,
  tileSize: number,
  traceType: number,
  sourceRunId: number,
  config: { color: number; radius: number; interactRange: number },
): number {
  const eid = addEntity(world);

  addComponent(world, eid, Position);
  Position.x[eid] = tileX * tileSize + tileSize / 2;
  Position.y[eid] = tileY * tileSize + tileSize / 2;

  addComponent(world, eid, SpriteRef);
  SpriteRef.color[eid] = config.color;
  SpriteRef.radius[eid] = config.radius;

  addComponent(world, eid, WorldTrace);
  WorldTrace.traceType[eid] = traceType;
  WorldTrace.sourceRunId[eid] = sourceRunId;
  WorldTrace.glowPhase[eid] = Math.random() * Math.PI * 2;
  WorldTrace.interactRange[eid] = config.interactRange;

  return eid;
}

/**
 * Derive a deterministic tile position from a seed.
 * Ensures traces from the same run appear in consistent locations.
 */
function deriveTracePosition(seed: number, axis: number, mapSize: number): number {
  // Mulberry32-style hash
  let t = (seed + axis * 0x6d2b79f5 + 0x9e3779b9) | 0;
  t = Math.imul(t ^ (t >>> 15), t | 1);
  t ^= t + Math.imul(t ^ (t >>> 7), t | 61);
  const normalized = ((t ^ (t >>> 14)) >>> 0) / 4294967296;

  // Keep away from edges (10% margin)
  const margin = Math.floor(mapSize * 0.1);
  return margin + Math.floor(normalized * (mapSize - 2 * margin));
}

/**
 * Update trace glow animation (pulsing effect).
 * Called in the game update loop.
 */
export function updateTraceGlow(
  traceInfos: WorldTraceInfo[],
  delta: number,
): void {
  const pulseSpeed = 1.2; // radians per second
  const deltaSec = delta / 1000;

  for (const info of traceInfos) {
    WorldTrace.glowPhase[info.eid] += pulseSpeed * deltaSec;
  }
}