import { supabase } from './supabase-client.js';
import { authService } from './auth-service.js';
import { cryptoService } from './crypto-service.js';
import { db } from '../db/database.js';

class SyncManager {
  constructor() {
    this.isSyncing = false;
    this.lastSyncTime = 0;
    this.lastUploadedSettings = {}; // Cache to prevent redundant uploads
    
    // Listen for auth state changes
    authService.onAuthStateChange(async (event, session) => {
      if (event === 'SIGNED_IN' || event === 'TOKEN_REFRESHED') {
        // If we log in and the crypto is unlocked, we can trigger sync
        if (authService.isCryptoUnlocked()) {
          this.sync();
        }
      }
    });
  }

  async initialize() {
    // Called once on app startup to trigger initial sync if already logged in
    if (authService.user && authService.isCryptoUnlocked()) {
      this.sync();
      
      // Auto-Sync every 15 seconds
      setInterval(() => {
        if (authService.user && authService.isCryptoUnlocked()) {
          this.sync();
        }
      }, 15000);
    }
  }

  async sync() {
    if (!authService.user || !authService.isCryptoUnlocked() || this.isSyncing) return;
    this.isSyncing = true;
    const userId = authService.user.id;

    console.log('[Sync] Starting Sync...');
    try {
      let hasUpdates = false;
      if (await this.syncSettings(userId)) hasUpdates = true;
      if (await this.syncConversations(userId)) hasUpdates = true;
      if (await this.syncMessages(userId)) hasUpdates = true;
      if (await this.syncFlashcardDecks(userId)) hasUpdates = true;
      if (await this.syncFlashcards(userId)) hasUpdates = true;
      
      console.log('[Sync] Sync completed successfully.');
      
      if (hasUpdates) {
        console.log('[Sync] New remote changes found, dispatching event.');
        window.dispatchEvent(new CustomEvent('cloud_sync_updated'));
      }
      this.lastSyncTime = Date.now();
    } catch (e) {
      console.error('[Sync] Error during sync:', e);
    } finally {
      this.isSyncing = false;
    }
  }

  async syncSettings(userId) {
    // Local to Remote
    const localSettings = db.exec("SELECT key, value FROM settings");
    
    // Remote to Local
    const { data: remoteSettings, error } = await supabase
      .from('settings')
      .select('*')
      .eq('user_id', userId);
      
    if (error) throw error;

    const remoteSettingsMap = {};
    if (remoteSettings) {
      for (const row of remoteSettings) {
        remoteSettingsMap[row.key] = await cryptoService.decrypt(row.value);
      }
    }

    // Check if local settings is effectively empty (only defaults, no api keys)
    const hasLocalApiKey = localSettings.some(r => r.key.includes('api_key') && r.value && r.value.trim().length > 0);
    const hasRemoteApiKey = Object.keys(remoteSettingsMap).some(k => k.includes('api_key') && remoteSettingsMap[k] && remoteSettingsMap[k].trim().length > 0);

    // If local has no API keys, but remote has some, we assume this is a NEW login on a new device.
    // In this case, we DO NOT push our local defaults to remote. We just pull from remote.
    if (!hasLocalApiKey && hasRemoteApiKey) {
      for (const key of Object.keys(remoteSettingsMap)) {
        if (remoteSettingsMap[key]) {
          db.setSetting(key, remoteSettingsMap[key]);
        }
      }
      return; // Skip pushing to remote
    }

    // Otherwise, push local to remote

    for (const row of localSettings) {
      if (this.lastUploadedSettings[row.key] === row.value) continue; // Skip redundant uploads

      const encryptedValue = await cryptoService.encrypt(row.value);
      await supabase.from('settings').upsert({
        user_id: userId,
        key: row.key,
        value: encryptedValue,
        updated_at: new Date().toISOString()
      }, { onConflict: 'user_id, key' });
      
      this.lastUploadedSettings[row.key] = row.value; // Cache it
    }
    
    let updated = false;
    // Pull any setting from remote that isn't locally set (e.g. from another device)
    if (remoteSettings) {
      for (const row of remoteSettings) {
        const localVal = db.getSetting(row.key);
        if (!localVal) {
          const decrypted = await cryptoService.decrypt(row.value);
          if (decrypted) {
            db.setSetting(row.key, decrypted);
            updated = true;
          }
        }
      }
    }
    return updated;
  }

  async syncConversations(userId) {
    const localConvs = db.getConversations();
    
    const { data: remoteConvs, error } = await supabase
      .from('conversations')
      .select('*')
      .eq('user_id', userId);
      
    if (error) throw error;
    
    // Create map for fast lookup
    const remoteMap = {};
    if (remoteConvs) {
      for (const c of remoteConvs) remoteMap[c.id] = c;
    }

    for (const local of localConvs) {
      const remote = remoteMap[local.id];
      const localTime = new Date(local.updated_at).getTime();
      const remoteTime = remote ? new Date(remote.updated_at).getTime() : 0;

      // Push to remote if local is newer or doesn't exist on remote
      if (!remote || localTime > remoteTime) {
        await supabase.from('conversations').upsert({
          id: local.id,
          user_id: userId,
          title: await cryptoService.encrypt(local.title),
          emoji: await cryptoService.encrypt(local.emoji),
          preview: await cryptoService.encrypt(local.preview),
          model_used: local.model_used,
          created_at: local.created_at,
          updated_at: local.updated_at
        }, { onConflict: 'id, user_id' });
      }
    }

    let updated = false;
    // Pull from remote if remote is newer or doesn't exist locally
    if (remoteConvs) {
      for (const remote of remoteConvs) {
        const local = localConvs.find(c => c.id === remote.id);
        const remoteTime = new Date(remote.updated_at).getTime();
        const localTime = local ? new Date(local.updated_at).getTime() : 0;

        if (!local || remoteTime > localTime) {
          const title = await cryptoService.decrypt(remote.title);
          const emoji = await cryptoService.decrypt(remote.emoji);
          const preview = await cryptoService.decrypt(remote.preview);
          
          if (!local) {
            db.exec(
              "INSERT INTO conversations (id, title, emoji, preview, model_used, created_at, updated_at) VALUES (?, ?, ?, ?, ?, ?, ?)",
              [remote.id, title, emoji, preview, remote.model_used, remote.created_at, remote.updated_at]
            );
          } else {
            db.exec(
              "UPDATE conversations SET title = ?, emoji = ?, preview = ?, model_used = ?, updated_at = ? WHERE id = ?",
              [title, emoji, preview, remote.model_used, remote.updated_at, remote.id]
            );
          }
          updated = true;
        }
      }
    }
    return updated;
  }

  async syncMessages(userId) {
    const localMsgs = db.exec("SELECT * FROM messages");
    
    // Because messages can be large, we might only want to fetch IDs to see what's missing
    const { data: remoteMsgs, error } = await supabase
      .from('messages')
      .select('id, created_at')
      .eq('user_id', userId);
      
    if (error) throw error;
    
    const remoteIds = new Set((remoteMsgs || []).map(m => m.id));
    const localIds = new Set(localMsgs.map(m => m.id));
    
    // Push local to remote
    for (const local of localMsgs) {
      if (!remoteIds.has(local.id)) {
        await supabase.from('messages').upsert({
          id: local.id,
          conversation_id: local.conversation_id,
          user_id: userId,
          role: local.role,
          content: await cryptoService.encrypt(local.content),
          model_used: local.model_used,
          style_used: local.style_used,
          created_at: local.created_at
        }, { onConflict: 'id, user_id' });
      }
    }
    
    let updated = false;
    // Pull remote to local
    for (const remote of (remoteMsgs || [])) {
      if (!localIds.has(remote.id)) {
        const { data: remoteFull } = await supabase
          .from('messages')
          .select('*')
          .eq('id', remote.id)
          .single();
          
        if (remoteFull) {
          const content = await cryptoService.decrypt(remoteFull.content);
          db.exec(
            "INSERT INTO messages (id, conversation_id, role, content, model_used, style_used, created_at) VALUES (?, ?, ?, ?, ?, ?, ?)",
            [remoteFull.id, remoteFull.conversation_id, remoteFull.role, content, remoteFull.model_used, remoteFull.style_used, remoteFull.created_at]
          );
          updated = true;
        }
      }
    }
    return updated;
  }

  async syncFlashcardDecks(userId) {
    const localDecks = db.getDecks();
    
    const { data: remoteDecks, error } = await supabase
      .from('flashcard_decks')
      .select('*')
      .eq('user_id', userId);
      
    if (error) {
      console.error("[Sync] Error fetching decks", error);
      throw error;
    }
    
    const remoteMap = {};
    if (remoteDecks) {
      for (const c of remoteDecks) remoteMap[c.id] = c;
    }

    for (const local of localDecks) {
      const remote = remoteMap[local.id];
      const localTime = new Date(local.updated_at).getTime();
      const remoteTime = remote ? new Date(remote.updated_at).getTime() : 0;

      if (!remote || localTime > remoteTime) {
        await supabase.from('flashcard_decks').upsert({
          id: local.id,
          user_id: userId,
          title: await cryptoService.encrypt(local.title),
          description: await cryptoService.encrypt(local.description || ''),
          color: local.color,
          source_lang: local.source_lang,
          target_lang: local.target_lang,
          created_at: local.created_at,
          updated_at: local.updated_at
        }, { onConflict: 'id, user_id' });
      }
    }

    let updated = false;
    if (remoteDecks) {
      for (const remote of remoteDecks) {
        const local = localDecks.find(c => c.id === remote.id);
        const remoteTime = new Date(remote.updated_at).getTime();
        const localTime = local ? new Date(local.updated_at).getTime() : 0;

        if (!local || remoteTime > localTime) {
          const title = await cryptoService.decrypt(remote.title);
          const description = await cryptoService.decrypt(remote.description);
          
          if (!local) {
            db.exec(
              "INSERT INTO flashcard_decks (id, title, description, color, source_lang, target_lang, created_at, updated_at) VALUES (?, ?, ?, ?, ?, ?, ?, ?)",
              [remote.id, title, description, remote.color, remote.source_lang, remote.target_lang, remote.created_at, remote.updated_at]
            );
          } else {
            db.exec(
              "UPDATE flashcard_decks SET title = ?, description = ?, color = ?, source_lang = ?, target_lang = ?, updated_at = ? WHERE id = ?",
              [title, description, remote.color, remote.source_lang, remote.target_lang, remote.updated_at, remote.id]
            );
          }
          updated = true;
        }
      }
    }
    return updated;
  }

  async syncFlashcards(userId) {
    const localCards = db.exec("SELECT * FROM flashcards");
    
    const { data: remoteCardsRaw, error } = await supabase
      .from('flashcards')
      .select('id, updated_at')
      .eq('user_id', userId);
      
    if (error) {
      console.error("[Sync] Error fetching flashcards", error);
      throw error;
    }
    
    const remoteMapRaw = {};
    for (const r of (remoteCardsRaw || [])) {
      remoteMapRaw[r.id] = r;
    }

    for (const local of localCards) {
      const remoteRaw = remoteMapRaw[local.id];
      const localTime = new Date(local.updated_at).getTime();
      const remoteTime = remoteRaw ? new Date(remoteRaw.updated_at).getTime() : 0;

      if (!remoteRaw || localTime > remoteTime) {
        await supabase.from('flashcards').upsert({
          id: local.id,
          user_id: userId,
          deck_id: local.deck_id,
          front: await cryptoService.encrypt(local.front),
          back: await cryptoService.encrypt(local.back),
          image_url: local.image_url ? await cryptoService.encrypt(local.image_url) : null,
          next_review: local.next_review,
          ease_factor: local.ease_factor,
          interval: local.interval,
          repetitions: local.repetitions,
          created_at: local.created_at,
          updated_at: local.updated_at
        }, { onConflict: 'id, user_id' });
      }
    }
    
    let updated = false;
    for (const remoteRaw of (remoteCardsRaw || [])) {
      const local = localCards.find(c => c.id === remoteRaw.id);
      const remoteTime = new Date(remoteRaw.updated_at).getTime();
      const localTime = local ? new Date(local.updated_at).getTime() : 0;

      if (!local || remoteTime > localTime) {
        const { data: remoteFull } = await supabase
          .from('flashcards')
          .select('*')
          .eq('id', remoteRaw.id)
          .single();
          
        if (remoteFull) {
          const front = await cryptoService.decrypt(remoteFull.front);
          const back = await cryptoService.decrypt(remoteFull.back);
          const image_url = remoteFull.image_url ? await cryptoService.decrypt(remoteFull.image_url) : null;
          
          if (!local) {
            db.exec(
              "INSERT INTO flashcards (id, deck_id, front, back, image_url, next_review, ease_factor, interval, repetitions, created_at, updated_at) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)",
              [remoteFull.id, remoteFull.deck_id, front, back, image_url, remoteFull.next_review, remoteFull.ease_factor, remoteFull.interval, remoteFull.repetitions, remoteFull.created_at, remoteFull.updated_at]
            );
          } else {
            db.exec(
              "UPDATE flashcards SET front = ?, back = ?, image_url = ?, next_review = ?, ease_factor = ?, interval = ?, repetitions = ?, updated_at = ? WHERE id = ?",
              [front, back, image_url, remoteFull.next_review, remoteFull.ease_factor, remoteFull.interval, remoteFull.repetitions, remoteFull.updated_at, remoteFull.id]
            );
          }
          updated = true;
        }
      }
    }
    return updated;
  }
}

export const syncManager = new SyncManager();