ChatApp/apps/desktop/src/lib/messageCache.ts

// Local SQLite message cache. Persists decrypted messages so startup +
// conversation-switch hydrate from disk instantly instead of waiting on a
// network round-trip + batch decrypt.
//
// The cache is per-device-local (app-local-data dir, same trust boundary as
// the device private key). Plaintext is stored because the threat model
// already assumes local-disk access means compromise — same as the existing
// outbox + secret store. Ciphertext + nonce are kept alongside so a future
// key-rotation migration can re-derive plaintext when a new bundle arrives.

import type { DecryptedMessage } from '@chat-app/shared/chat';

import { isTauriRuntime } from './globalShortcut';

interface Database {
  execute: (sql: string, values?: unknown[]) => Promise<{ rowsAffected?: number }>;
  select: <T>(sql: string, values?: unknown[]) => Promise<T[]>;
  close: () => Promise<boolean>;
}

interface DatabaseStatic {
  load: (path: string) => Promise<Database>;
}

const DB_NAME = 'chatapp-cache.db';

let dbPromise: Promise<Database | null> | null = null;

async function loadDb(): Promise<Database | null> {
  if (!isTauriRuntime()) return null;
  try {
    // Dynamic import so browser-preview builds don't choke on the tauri
    // plugin module. Vite will statically analyse this + split it into a
    // chunk that only loads inside Tauri.
    const mod = (await import('@tauri-apps/plugin-sql')) as {
      default: DatabaseStatic;
      Database?: DatabaseStatic;
    };
    const DatabaseCtor: DatabaseStatic = mod.default ?? (mod as { Database: DatabaseStatic }).Database;
    const db = await DatabaseCtor.load('sqlite:' + DB_NAME);
    await db.execute(`
      CREATE TABLE IF NOT EXISTS messages (
        id TEXT PRIMARY KEY,
        conversation_id TEXT NOT NULL,
        sender_id TEXT NOT NULL,
        sender_device_id TEXT,
        reply_to_id TEXT,
        edited_at TEXT,
        deleted_at TEXT,
        created_at TEXT NOT NULL,
        plaintext TEXT
      );
    `);
    await db.execute(
      'CREATE INDEX IF NOT EXISTS idx_msgs_conv_created ON messages(conversation_id, created_at);',
    );
    // FTS5 virtual table for instant full-text search across the cache.
    // Keeps only the searchable text columns (plaintext + sender), keyed
    // by the message id so we can join back to the main row. Triggers
    // mirror inserts/updates/deletes so the index never drifts.
    //
    // Falls back gracefully on FTS5-less builds: the IF NOT EXISTS keeps
    // the call idempotent, and the surrounding try/catch already handles
    // a CREATE failure by skipping the whole cache.
    try {
      await db.execute(
        `CREATE VIRTUAL TABLE IF NOT EXISTS messages_fts USING fts5(
          message_id UNINDEXED,
          conversation_id UNINDEXED,
          plaintext,
          tokenize = 'unicode61 remove_diacritics 2'
        );`,
      );
      await db.execute(
        `CREATE TRIGGER IF NOT EXISTS messages_ai AFTER INSERT ON messages BEGIN
           INSERT INTO messages_fts (message_id, conversation_id, plaintext)
           VALUES (new.id, new.conversation_id, COALESCE(new.plaintext, ''));
         END;`,
      );
      await db.execute(
        `CREATE TRIGGER IF NOT EXISTS messages_ad AFTER DELETE ON messages BEGIN
           DELETE FROM messages_fts WHERE message_id = old.id;
         END;`,
      );
      await db.execute(
        `CREATE TRIGGER IF NOT EXISTS messages_au AFTER UPDATE ON messages BEGIN
           DELETE FROM messages_fts WHERE message_id = old.id;
           INSERT INTO messages_fts (message_id, conversation_id, plaintext)
           VALUES (new.id, new.conversation_id, COALESCE(new.plaintext, ''));
         END;`,
      );
    } catch (err: unknown) {
      console.warn('FTS5 init failed — search falls back to in-memory scan', err);
    }
    return db;
  } catch (err: unknown) {
    console.warn('messageCache init failed — falling back to memory-only', err);
    return null;
  }
}

function getDb(): Promise<Database | null> {
  if (!dbPromise) dbPromise = loadDb();
  return dbPromise;
}

// ---------------------------------------------------------------------------
// Public API — all calls are no-ops when the cache isn't available (browser
// preview, init error, etc.), so callers never need to guard.
// ---------------------------------------------------------------------------

interface Row {
  id: string;
  conversation_id: string;
  sender_id: string;
  sender_device_id: string | null;
  reply_to_id: string | null;
  edited_at: string | null;
  deleted_at: string | null;
  created_at: string;
  plaintext: string | null;
}

export async function loadCachedMessages(
  conversationId: string,
  limit = 500,
): Promise<DecryptedMessage[]> {
  const db = await getDb();
  if (!db) return [];
  try {
    const rows = await db.select<Row>(
      'SELECT * FROM messages WHERE conversation_id = $1 ORDER BY created_at DESC LIMIT $2',
      [conversationId, limit],
    );
    return rows
      .reverse()
      .map((r) => ({
        id: r.id,
        conversationId: r.conversation_id,
        senderId: r.sender_id,
        senderDeviceId: r.sender_device_id,
        replyToId: r.reply_to_id,
        editedAt: r.edited_at,
        deletedAt: r.deleted_at,
        createdAt: r.created_at,
        plaintext: r.plaintext,
      }));
  } catch (err: unknown) {
    console.warn('loadCachedMessages failed', err);
    return [];
  }
}

export async function persistMessages(
  conversationId: string,
  messages: DecryptedMessage[],
): Promise<void> {
  const db = await getDb();
  if (!db || messages.length === 0) return;
  try {
    // Replace strategy: each message is keyed by id so upsert is "INSERT OR
    // REPLACE". Attachments + forward chains are part of `plaintext` JSON so
    // nothing lives outside this table.
    for (const m of messages) {
      await db.execute(
        `INSERT OR REPLACE INTO messages
         (id, conversation_id, sender_id, sender_device_id, reply_to_id,
          edited_at, deleted_at, created_at, plaintext)
         VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)`,
        [
          m.id,
          conversationId,
          m.senderId,
          m.senderDeviceId,
          m.replyToId,
          m.editedAt,
          m.deletedAt,
          m.createdAt,
          m.plaintext,
        ],
      );
    }
  } catch (err: unknown) {
    console.warn('persistMessages failed', err);
  }
}

export async function deleteCachedMessage(id: string): Promise<void> {
  const db = await getDb();
  if (!db) return;
  try {
    await db.execute('DELETE FROM messages WHERE id = $1', [id]);
  } catch (err: unknown) {
    console.warn('deleteCachedMessage failed', err);
  }
}

// Full-text search across cached messages. Returns rows in newest-first
// order; caller maps to DecryptedMessage. Empty result on cache-miss or
// FTS5 not available — caller should fall back to in-memory regex.
export async function searchCachedMessages(
  conversationId: string,
  query: string,
  limit = 200,
): Promise<DecryptedMessage[]> {
  const db = await getDb();
  if (!db) return [];
  const trimmed = query.trim();
  if (trimmed.length === 0) return [];
  // Sanitize for FTS5 MATCH syntax. Strip quotes + control chars; wrap in
  // an OR over each token with a trailing wildcard so partial words match.
  // Hyphens + colons are FTS5 operators so we drop them.
  const tokens = trimmed
    .replace(/["'\u0000-\u001f]/g, ' ')
    .replace(/[-:^]/g, ' ')
    .split(/\s+/)
    .filter(Boolean);
  if (tokens.length === 0) return [];
  const matchExpr = tokens.map((t) => '"' + t.replace(/"/g, '') + '"*').join(' AND ');
  try {
    const rows = await db.select<Row>(
      `SELECT m.* FROM messages m
       JOIN messages_fts f ON f.message_id = m.id
       WHERE f.conversation_id = $1 AND messages_fts MATCH $2
       ORDER BY m.created_at DESC
       LIMIT $3`,
      [conversationId, matchExpr, limit],
    );
    return rows.map((r) => ({
      id: r.id,
      conversationId: r.conversation_id,
      senderId: r.sender_id,
      senderDeviceId: r.sender_device_id,
      replyToId: r.reply_to_id,
      editedAt: r.edited_at,
      deletedAt: r.deleted_at,
      createdAt: r.created_at,
      plaintext: r.plaintext,
    }));
  } catch (err: unknown) {
    console.warn('searchCachedMessages failed', err);
    return [];
  }
}

// Housekeeping — run once per session to bound the cache size. Keeps the
// latest KEEP_PER_CONV messages per conversation.
const KEEP_PER_CONV = 1000;

export async function pruneCache(): Promise<void> {
  const db = await getDb();
  if (!db) return;
  try {
    await db.execute(
      `DELETE FROM messages WHERE id IN (
         SELECT id FROM messages m
         WHERE (
           SELECT COUNT(*) FROM messages m2
           WHERE m2.conversation_id = m.conversation_id
             AND m2.created_at > m.created_at
         ) >= $1
       )`,
      [KEEP_PER_CONV],
    );
  } catch (err: unknown) {
    console.warn('pruneCache failed', err);
  }
}