import Database from 'better-sqlite3';
import type { Config } from '../config/index.js';
import path from 'path';
import fs from 'fs';

export function createDatabase(config: Config): Database.Database {
  const dbPath = path.resolve(process.cwd(), config.database.path);
  const dbDir = path.dirname(dbPath);

  // Ensure directory exists
  if (!fs.existsSync(dbDir)) {
    fs.mkdirSync(dbDir, { recursive: true });
  }

  const db = new Database(dbPath);

  // Enable WAL mode for better concurrency
  db.pragma('journal_mode = WAL');
  db.pragma('foreign_keys = ON');

  return db;
}

export function runMigrations(db: Database.Database): void {
  // Create tables if they don't exist
  db.exec(`
    CREATE TABLE IF NOT EXISTS processed_posts (
      id TEXT PRIMARY KEY,
      subreddit TEXT NOT NULL,
      author TEXT NOT NULL,
      title TEXT NOT NULL,
      image_url TEXT,
      image_analysis TEXT,
      generated_message TEXT,
      processed_at INTEGER NOT NULL,
      message_sent INTEGER DEFAULT 0,
      error TEXT
    );

    CREATE TABLE IF NOT EXISTS sent_messages (
      id INTEGER PRIMARY KEY AUTOINCREMENT,
      post_id TEXT NOT NULL,
      recipient TEXT NOT NULL,
      subject TEXT NOT NULL,
      message TEXT NOT NULL,
      sent_at INTEGER NOT NULL,
      FOREIGN KEY (post_id) REFERENCES processed_posts(id)
    );

    CREATE TABLE IF NOT EXISTS successful_messages (
      id INTEGER PRIMARY KEY AUTOINCREMENT,
      sent_message_id INTEGER,
      original_message TEXT NOT NULL,
      image_analysis TEXT,
      post_title TEXT,
      response_snippet TEXT,
      created_at INTEGER NOT NULL
    );

    CREATE TABLE IF NOT EXISTS activity_log (
      id INTEGER PRIMARY KEY AUTOINCREMENT,
      timestamp INTEGER NOT NULL,
      type TEXT NOT NULL,
      message TEXT NOT NULL,
      recipient TEXT,
      image_url TEXT
    );

    CREATE INDEX IF NOT EXISTS idx_posts_subreddit
      ON processed_posts(subreddit);
    CREATE INDEX IF NOT EXISTS idx_posts_processed_at
      ON processed_posts(processed_at);
    CREATE INDEX IF NOT EXISTS idx_posts_message_sent
      ON processed_posts(message_sent);
    CREATE INDEX IF NOT EXISTS idx_activity_log_timestamp
      ON activity_log(timestamp);
  `);

  // Add new columns to existing tables (safe to run multiple times)
  const addColumnIfNotExists = (table: string, column: string, definition: string) => {
    const columns = db.prepare(`PRAGMA table_info(${table})`).all() as { name: string }[];
    const exists = columns.some((c) => c.name === column);
    if (!exists) {
      db.exec(`ALTER TABLE ${table} ADD COLUMN ${column} ${definition}`);
    }
  };

  addColumnIfNotExists('sent_messages', 'got_response', 'INTEGER DEFAULT 0');
  addColumnIfNotExists('sent_messages', 'response_checked_at', 'INTEGER');

  // Create index for response checking
  db.exec(`CREATE INDEX IF NOT EXISTS idx_sent_messages_response ON sent_messages(got_response)`);
  db.exec(`CREATE INDEX IF NOT EXISTS idx_sent_messages_recipient ON sent_messages(recipient)`);

  // Add strategy_id column for A/B testing
  addColumnIfNotExists('sent_messages', 'strategy_id', 'TEXT');

  // Add subreddit column to successful_messages for smarter example selection
  addColumnIfNotExists('successful_messages', 'subreddit', 'TEXT');

  // Migration: Make sent_message_id nullable in successful_messages
  // SQLite doesn't support ALTER COLUMN, so we need to recreate the table
  const successfulMsgColumns = db.prepare(`PRAGMA table_info(successful_messages)`).all() as { name: string; notnull: number }[];
  const sentMsgIdCol = successfulMsgColumns.find((c) => c.name === 'sent_message_id');

  if (sentMsgIdCol && sentMsgIdCol.notnull === 1) {
    // Column is currently NOT NULL, we need to migrate
    db.exec(`
      -- Create new table with nullable sent_message_id
      CREATE TABLE successful_messages_new (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        sent_message_id INTEGER,
        original_message TEXT NOT NULL,
        image_analysis TEXT,
        post_title TEXT,
        response_snippet TEXT,
        created_at INTEGER NOT NULL
      );
      
      -- Copy existing data
      INSERT INTO successful_messages_new 
        SELECT id, sent_message_id, original_message, image_analysis, post_title, response_snippet, created_at
        FROM successful_messages;
      
      -- Drop old table
      DROP TABLE successful_messages;
      
      -- Rename new table
      ALTER TABLE successful_messages_new RENAME TO successful_messages;
    `);
  }
}