// ═══════════════════════════════════════════════════
// PROJECT MNEMOSYNE — MEMORY PULSE
// ═══════════════════════════════════════════════════
//
// BFS wave animation triggered on crystal click.
// When a memory crystal is clicked, a visual pulse
// radiates through the connection graph — illuminating
// linked memories hop-by-hop with a glow that rises
// sharply and then fades.
//
// Usage:
//   MemoryPulse.init(SpatialMemory);
//   MemoryPulse.triggerPulse(memId);
//   MemoryPulse.update();  // called each frame
// ═══════════════════════════════════════════════════

const MemoryPulse = (() => {

  let _sm = null;

  // [{mesh, startTime, delay, duration, peakIntensity, baseIntensity}]
  const _activeEffects = [];

  // ── Config ───────────────────────────────────────
  const HOP_DELAY_MS   = 180;   // ms between hops
  const PULSE_DURATION = 650;   // ms for glow rise + fade per node
  const PEAK_INTENSITY = 5.5;   // emissiveIntensity at pulse peak
  const MAX_HOPS       = 8;     // BFS depth limit

  // ── Helpers ──────────────────────────────────────

  // Build memId -> mesh from SpatialMemory public API
  function _buildMeshMap() {
    const map = {};
    const meshes = _sm.getCrystalMeshes();
    for (const mesh of meshes) {
      const entry = _sm.getMemoryFromMesh(mesh);
      if (entry) map[entry.data.id] = mesh;
    }
    return map;
  }

  // Build bidirectional adjacency graph from memory connection data
  function _buildGraph() {
    const graph = {};
    const memories = _sm.getAllMemories();
    for (const mem of memories) {
      if (!graph[mem.id]) graph[mem.id] = [];
      if (mem.connections) {
        for (const targetId of mem.connections) {
          graph[mem.id].push(targetId);
          if (!graph[targetId]) graph[targetId] = [];
          graph[targetId].push(mem.id);
        }
      }
    }
    return graph;
  }

  // ── Public API ───────────────────────────────────

  function init(spatialMemory) {
    _sm = spatialMemory;
  }

  /**
   * Trigger a BFS pulse wave originating from memId.
   * Each hop level illuminates after HOP_DELAY_MS * hop ms.
   * @param {string} memId - ID of the clicked memory crystal
   */
  function triggerPulse(memId) {
    if (!_sm) return;

    const meshMap = _buildMeshMap();
    const graph   = _buildGraph();

    if (!meshMap[memId]) return;

    // Cancel any existing effects on the same meshes (avoids stacking)
    _activeEffects.length = 0;

    // BFS
    const visited = new Set([memId]);
    const queue   = [{ id: memId, hop: 0 }];
    const now     = performance.now();
    const scheduled = [];

    while (queue.length > 0) {
      const { id, hop } = queue.shift();
      if (hop > MAX_HOPS) continue;

      const mesh = meshMap[id];
      if (mesh) {
        const strength      = mesh.userData.strength || 0.7;
        const baseIntensity = 1.0 + Math.sin(mesh.userData.pulse || 0) * 0.5 * strength;

        scheduled.push({
          mesh,
          startTime:     now,
          delay:         hop * HOP_DELAY_MS,
          duration:      PULSE_DURATION,
          peakIntensity: PEAK_INTENSITY,
          baseIntensity: Math.max(0.5, baseIntensity)
        });
      }

      for (const neighborId of (graph[id] || [])) {
        if (!visited.has(neighborId)) {
          visited.add(neighborId);
          queue.push({ id: neighborId, hop: hop + 1 });
        }
      }
    }

    for (const effect of scheduled) {
      _activeEffects.push(effect);
    }

    console.info('[MemoryPulse] Pulse triggered from', memId, '—', scheduled.length, 'nodes in wave');
  }

  /**
   * Advance all active pulse animations. Call once per frame.
   */
  function update() {
    if (_activeEffects.length === 0) return;

    const now = performance.now();

    for (let i = _activeEffects.length - 1; i >= 0; i--) {
      const e = _activeEffects[i];
      const elapsed = now - e.startTime - e.delay;

      if (elapsed < 0) continue;  // waiting for its hop delay

      if (elapsed >= e.duration) {
        // Animation complete — restore base intensity
        if (e.mesh.material) {
          e.mesh.material.emissiveIntensity = e.baseIntensity;
        }
        _activeEffects.splice(i, 1);
        continue;
      }

      // t: 0 → 1 over duration
      const t    = elapsed / e.duration;
      // sin curve over [0, π]: smooth rise then fall
      const glow = Math.sin(t * Math.PI);

      if (e.mesh.material) {
        e.mesh.material.emissiveIntensity =
          e.baseIntensity + glow * (e.peakIntensity - e.baseIntensity);
      }
    }
  }

  return { init, triggerPulse, update };
})();

export { MemoryPulse };