/**
 * agentMemory.ts — Agent Memory Store (Sessione 15: localStorage → Dexie)
 *
 * Strategia:
 *  - In-memory cache (_cache) come layer sincrono per i caller esistenti
 *  - Dexie (agentMemoryDb) come persistence primaria (write-behind, async)
 *  - localStorage come fallback read-once al boot → poi rimosso (migrazione one-shot)
 *  - Backend sync (fire-and-forget) invariato
 *
 * API pubblica invariata → zero regressioni nei caller.
 *
 * Invarianti:
 *  - Mai chiamare localStorage nel render path React
 *  - MAX_ENTRIES=500 LRU enforced su Dexie ogni 50 writes (non bloccante)
 *  - GAP 4: auto-summarization via Gemini Flash quando entries > SUMMARIZE_THRESHOLD=400
 *  - initMemory() va chiamato da main.tsx prima del mount (async, una volta)
 */

import { agentMemoryDb, type StoredMemoryEntry } from "@/lib/vfsDb";
import { makeTimedSignal } from "./agentLoop/networkConstants"; // iOS-safe timeout
import { getEmbedding } from "@/lib/agent/semanticEmbeddings";
import {
  syncMemoryToCloud,
  deleteMemoryFromCloud,
  clearMemoryFromCloud,
  hydrateMemoryFromCloud,
  subscribeToMemoryChanges,
  isMemoryCloudEnabled,
} from "@/lib/memoryCloud";
import {
  summarizeOldEntries,
  SUMMARIZE_THRESHOLD,
  SUMMARIZE_BATCH,
} from "@/lib/agent/memorySummarizer";

const LS_KEY     = "agente-memory";
const MIGRATE_KEY = "agente-memory-migrated-v6";
const MAX_ENTRIES = 500;
const PRUNE_EVERY = 50;  // prune Dexie ogni N writes

export type { StoredMemoryEntry as MemoryEntry };

type MemStore = Record<string, StoredMemoryEntry>;
type Listener = () => void;

// ─── In-memory cache ──────────────────────────────────────────────────────────
let _cache: MemStore = {};
let _writeCount = 0;
let _summarizing = false; // GAP 4: prevent concurrent summarization
const _listeners = new Set<Listener>();

// ─── Backend config ───────────────────────────────────────────────────────────
const BACKEND = (import.meta.env.VITE_BACKEND_URL ?? "").replace(/\/$/, "");

// ─── Notify listeners ─────────────────────────────────────────────────────────
function _notify(): void {
  _listeners.forEach(fn => fn());
}

// ─── Write-behind: persiste su Dexie (fire-and-forget) ───────────────────────
function _persist(entry: StoredMemoryEntry): void {
  agentMemoryDb.put(entry).catch(() => {});
  _writeCount++;
  // LRU prune ogni PRUNE_EVERY writes (non bloccante)
  if (_writeCount % PRUNE_EVERY === 0) {
    _pruneLRU();
  }
}

function _persistDelete(key: string): void {
  agentMemoryDb.delete(key).catch(() => {});
}

/** GAP 4: prune via Gemini summarization (se sopra soglia) o LRU classica */
function _pruneLRU(): void {
  const entries = Object.values(_cache).sort((a, b) => a.updatedAt - b.updatedAt);
  if (entries.length <= MAX_ENTRIES) return;

  // GAP 4: se sopra soglia summarization e nessun job già in corso → comprimi
  if (entries.length > SUMMARIZE_THRESHOLD && !_summarizing) {
    _summarizing = true;
    summarizeOldEntries(entries, SUMMARIZE_BATCH)
      .then(result => {
        if (result) {
          // Elimina entry originali dalla cache e da Dexie
          for (const e of result.replaced) {
            delete _cache[e.key];
            agentMemoryDb.delete(e.key).catch(() => {});
            deleteMemoryFromCloud(e.key).catch(() => {});
          }
          // Aggiungi il riassunto come nuova entry di memoria
          const summaryEntry: StoredMemoryEntry = {
            key:       result.key,
            value:     result.summary,
            category:  "summary",
            createdAt: Date.now(),
            updatedAt: Date.now(),
          };
          _cache[summaryEntry.key] = summaryEntry;
          agentMemoryDb.put(summaryEntry).catch(() => {});
          syncMemoryToCloud(summaryEntry).catch(() => {});
          _notify();
        } else {
          // Gemini non disponibile → fallback LRU classica
          const toRemove = entries.slice(0, entries.length - MAX_ENTRIES);
          for (const e of toRemove) {
            delete _cache[e.key];
            agentMemoryDb.delete(e.key).catch(() => {});
            deleteMemoryFromCloud(e.key).catch(() => {});
          }
        }
      })
      .catch(() => {
        // Fallback LRU classica su errore
        const toRemove = entries.slice(0, entries.length - MAX_ENTRIES);
        for (const e of toRemove) {
          delete _cache[e.key];
          agentMemoryDb.delete(e.key).catch(() => {});
        }
      })
      .finally(() => { _summarizing = false; });
    agentMemoryDb.pruneToLimit(MAX_ENTRIES).catch(() => {});
    return;
  }

  // Sotto soglia summarization → LRU classica
  const toRemove = entries.slice(0, entries.length - MAX_ENTRIES);
  for (const e of toRemove) {
    delete _cache[e.key];
    agentMemoryDb.delete(e.key).catch(() => {});
  }
  agentMemoryDb.pruneToLimit(MAX_ENTRIES).catch(() => {});
}

// ─── Backend sync helpers ──────────────────────────────────────────────────────

async function backendGet(key: string): Promise<string | null> {
  if (!BACKEND) return null;
  try {
    const res = await fetch(`${BACKEND}/api/memory/agent/${encodeURIComponent(key)}`, {
      signal: makeTimedSignal(4000),
    });
    if (!res.ok) return null;
    const data = await res.json() as { value?: string };
    return data.value ?? null;
  } catch { return null; }
}

async function backendLoadAll(): Promise<StoredMemoryEntry[]> {
  if (!BACKEND) return [];
  try {
    const res = await fetch(`${BACKEND}/api/memory/agent`, { signal: makeTimedSignal(6000) });
    if (!res.ok) return [];
    const data = await res.json() as { entries?: StoredMemoryEntry[] };
    return data.entries ?? [];
  } catch { return []; }
}

// ─── Boot initialization (chiamato da main.tsx) ────────────────────────────────
/**
 * Carica la memoria da Dexie nella cache in-memory.
 * Se Dexie è vuoto + localStorage ha dati (prima volta) → migra one-shot.
 * NON blocca il render — chiamato in main.tsx con await prima del mount React.
 */
export async function initMemory(): Promise<void> {
  try {
    // 1. Carica da Dexie
    const dexieEntries = await agentMemoryDb.getAll();

    if (dexieEntries.length > 0) {
      // Dexie ha dati → usa quelli come source of truth
      for (const e of dexieEntries) {
        _cache[e.key] = e;
      }
    } else {
      // Dexie vuoto → controlla localStorage (migrazione one-shot)
      const alreadyMigrated = localStorage.getItem(MIGRATE_KEY);
      if (!alreadyMigrated) {
        try {
          const raw = localStorage.getItem(LS_KEY);
          if (raw) {
            const lsData = JSON.parse(raw) as MemStore;
            const entries = Object.values(lsData);
            if (entries.length > 0) {
              // Migra → Dexie
              await agentMemoryDb.putMany(entries);
              for (const e of entries) { _cache[e.key] = e; }
            }
          }
        } catch { /* non-fatal */ }
        // Marca migrazione completata e rimuovi da localStorage
        try {
          localStorage.setItem(MIGRATE_KEY, "1");
          localStorage.removeItem(LS_KEY);
        } catch { /* non-fatal */ }
      }
    }
  } catch {
    // Fallback ultimo: leggi localStorage se Dexie non disponibile
    try {
      const raw = localStorage.getItem(LS_KEY);
      if (raw) {
        _cache = JSON.parse(raw) as MemStore;
      }
    } catch { /* non-fatal */ }
  }

  // GAP 3: hydrate from Supabase and merge (cloud vince se più recente)
  try {
    const cloudEntries = await hydrateMemoryFromCloud();
    let merged = 0;
    for (const e of cloudEntries) {
      const local = _cache[e.key];
      if (!local || e.updatedAt > local.updatedAt) {
        _cache[e.key] = e;
        agentMemoryDb.put(e).catch(() => {});
        merged++;
      }
    }
    if (merged > 0) _notify();
  } catch { /* non-fatal */ }

  // GAP 3: subscribe to Realtime changes from other devices
  subscribeToMemoryChanges({
    onUpsert: (e) => {
      const local = _cache[e.key];
      if (!local || e.updatedAt > local.updatedAt) {
        _cache[e.key] = e;
        agentMemoryDb.put(e).catch(() => {});
        _notify();
      }
    },
    onDelete: (key) => {
      if (_cache[key]) {
        delete _cache[key];
        agentMemoryDb.delete(key).catch(() => {});
        _notify();
      }
    },
  });

  // S140: backfill embedding per entry caricate da Dexie senza vettore.
  // Fire-and-forget: parte in background dopo 3s per non competere con LLM al boot.
  _backfillEmbeddings();
}

// ─── Backfill embeddings (S140) ───────────────────────────────────────────────
// Calcola embedding per le entry caricate da Dexie che non ce l'hanno ancora.
// Gira in background, batch da 5 con pausa 1.2s tra batch (rate limit Gemini free).
// Con 50 entry: ~12s totali. Con 500 entry: ~2min. Completamente trasparente.
async function _backfillEmbeddings(): Promise<void> {
  // Aspetta 3s dopo il boot: non compete con richieste LLM iniziali
  await new Promise(r => setTimeout(r, 3_000));

  const entries = Object.values(_cache).filter(e => !e.embedding && e.value.length > 0);
  if (!entries.length) return;

  const BATCH = 5;
  for (let i = 0; i < entries.length; i += BATCH) {
    const batch = entries.slice(i, i + BATCH);
    await Promise.all(
      batch.map(async (e) => {
        const vec = await getEmbedding(e.value).catch(() => null);
        if (vec && _cache[e.key]) {
          const updated: StoredMemoryEntry = { ..._cache[e.key], embedding: vec };
          _cache[e.key] = updated;
          agentMemoryDb.put(updated).catch(() => {});
        }
      })
    );
    // Pausa tra batch: evita burst su Gemini free tier (1500 req/min)
    if (i + BATCH < entries.length) {
      await new Promise(r => setTimeout(r, 1_200));
    }
  }
}

// ─── Public API (invariata) ────────────────────────────────────────────────────
// ─── S166-Fix5: re-trigger backfill quando viene aggiunto token Gemini ─────────
/** Avvia (o ri-avvia) il backfill degli embedding per entry senza vettore.
 *  Chiamare quando l'utente aggiunge un token Gemini durante la sessione. */
export function triggerEmbeddingBackfill(): void {
  const needsBackfill = Object.values(_cache).some(e => !e.embedding && e.value.length > 0);
  if (needsBackfill) _backfillEmbeddings().catch(() => {});
}

/**
 * S460: Trigger esplicito post-bulk-save (MemoryUpdater.ts).
 * Controlla la pressione della memoria e avvia summarization se sopra soglia.
 * Fire-and-forget — non blocca mai il chiamante.
 */
export function triggerMemoryPrune(): void {
  const count = Object.keys(_cache).length;
  if (count > SUMMARIZE_THRESHOLD) {
    _pruneLRU();
  }
}

export const agentMemory = {
  set(key: string, value: string, category = "general"): StoredMemoryEntry {
    const now = Date.now();
    const e: StoredMemoryEntry = {
      key, value, category,
      createdAt: _cache[key]?.createdAt ?? now,
      updatedAt: now,
    };
    _cache[key] = e;
    _persist(e);
    _notify();
    // S85: fire-and-forget embedding (Gemini text-embedding-004)
    getEmbedding(value).then(vec => {
      if (vec && _cache[key]) {
        const withEmbed: StoredMemoryEntry = { ..._cache[key], embedding: vec };
        _cache[key] = withEmbed;
        agentMemoryDb.put(withEmbed).catch(() => {});
      }
    }).catch(() => {});
    // S281-FIX-MEMORY_CONFLICT-5: singolo write Supabase (diretto dal frontend).
    // backendSet rimosso: causava double-write su stessa riga agent_memory →
    // race condition last-write-wins. Backend resta solo fallback di LETTURA.
    syncMemoryToCloud(e).catch(() => {});
    return e;
  },

  get(key: string): string | null {
    return _cache[key]?.value ?? null;
  },

  // Async get: in-memory first, then backend fallback
  async getAsync(key: string): Promise<string | null> {
    const cached = _cache[key]?.value ?? null;
    if (cached !== null) return cached;
    const remote = await backendGet(key);
    if (remote !== null) {
      agentMemory.set(key, remote);
      return remote;
    }
    return null;
  },

  list(category?: string): StoredMemoryEntry[] {
    const all = Object.values(_cache);
    return category ? all.filter(e => e.category === category) : all;
  },

  delete(key: string): boolean {
    if (!_cache[key]) return false;
    delete _cache[key];
    _persistDelete(key);
    deleteMemoryFromCloud(key).catch(() => {});
    _notify();
    return true;
  },

  clear(): void {
    _cache = {};
    agentMemoryDb.clear().catch(() => {});
    clearMemoryFromCloud().catch(() => {});
    try { localStorage.removeItem(LS_KEY); } catch { /* non-fatal */ }
    _notify();
  },

  subscribe(fn: Listener): () => void {
    _listeners.add(fn);
    return () => { _listeners.delete(fn); };
  },

  // S281-FIX-MEMORY_CONFLICT-5: syncFromBackend è fallback puro.
  // Se Supabase è attivo, il frontend è già idratato da hydrateMemoryFromCloud.
  // Il backend viene consultato solo quando Supabase non è disponibile.
  async syncFromBackend(): Promise<void> {
    if (isMemoryCloudEnabled) return; // Supabase attivo → nessun roundtrip backend
    const entries = await backendLoadAll();
    if (!entries.length) return;
    for (const e of entries) {
      const local = _cache[e.key];
      if (!local || e.updatedAt > local.updatedAt) {
        _cache[e.key] = e;
        _persist(e);
      }
    }
    _notify();
  },
};

export default agentMemory;