// 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.
//
// Under Electron all SQL goes through the main-process sql bridge
// (better-sqlite3). Public API below is identical to the Tauri-era
// version — callers don't change.

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

import { isTauriRuntime } from './globalShortcut';

const DB_NAME = 'chatapp-cache';

let loadPromise: Promise<string | null> | null = null;

async function getHandle(): Promise<string | null> {
  if (loadPromise) return loadPromise;
  if (!isTauriRuntime()) {
    loadPromise = Promise.resolve(null);
    return loadPromise;
  }
  loadPromise = (async (): Promise<string | null> => {
    try {
      const handle = await window.electronAPI.sqlLoad({ name: DB_NAME });
      await execute(
        handle,
        `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 execute(
        handle,
        'CREATE INDEX IF NOT EXISTS idx_msgs_conv_created ON messages(conversation_id, created_at);',
      );
      // FTS5 — conditional since not every SQLite build has it.
      try {
        await execute(
          handle,
          `CREATE VIRTUAL TABLE IF NOT EXISTS messages_fts USING fts5(
             message_id UNINDEXED,
             conversation_id UNINDEXED,
             plaintext,
             tokenize = 'unicode61 remove_diacritics 2'
           );`,
        );
        await execute(
          handle,
          `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 execute(
          handle,
          `CREATE TRIGGER IF NOT EXISTS messages_ad AFTER DELETE ON messages BEGIN
             DELETE FROM messages_fts WHERE message_id = old.id;
           END;`,
        );
        await execute(
          handle,
          `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 handle;
    } catch (err: unknown) {
      console.warn('messageCache init failed — falling back to memory-only', err);
      return null;
    }
  })();
  return loadPromise;
}

async function execute(handle: string, query: string, bindings?: unknown[]): Promise<void> {
  await window.electronAPI.sqlExecute({ handle, query, bindings: bindings ?? [] });
}

async function selectRows<T = Row>(
  handle: string,
  query: string,
  bindings?: unknown[],
): Promise<T[]> {
  const rows = await window.electronAPI.sqlSelect({
    handle,
    query,
    bindings: bindings ?? [],
  });
  return rows as unknown as T[];
}

// ---------------------------------------------------------------------------

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 handle = await getHandle();
  if (!handle) return [];
  try {
    const rows = await selectRows<Row>(
      handle,
      '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 handle = await getHandle();
  if (!handle || messages.length === 0) return;
  try {
    for (const m of messages) {
      await execute(
        handle,
        `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 handle = await getHandle();
  if (!handle) return;
  try {
    await execute(handle, 'DELETE FROM messages WHERE id = $1', [id]);
  } catch (err: unknown) {
    console.warn('deleteCachedMessage failed', err);
  }
}

// Full-text search across cached messages. Empty result on cache-miss
// or FTS5 unavailable — caller should fall back to in-memory regex.
export async function searchCachedMessages(
  conversationId: string,
  query: string,
  limit = 200,
): Promise<DecryptedMessage[]> {
  const handle = await getHandle();
  if (!handle) return [];
  const trimmed = query.trim();
  if (trimmed.length === 0) return [];
  const tokens = trimmed
    .replace(/["' -]/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 selectRows<Row>(
      handle,
      `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 — bound the cache size.
const KEEP_PER_CONV = 1000;

export async function pruneCache(): Promise<void> {
  const handle = await getHandle();
  if (!handle) return;
  try {
    await execute(
      handle,
      `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);
  }
}