/**
 * Database initialization and migration.
 *
 * Handles:
 * - Creating/opening SQLite database
 * - Running DDL schema setup
 * - Migrating legacy JSON files (one-time)
 */

import BetterSqlite3 from 'better-sqlite3';
import { existsSync, readFileSync, renameSync } from 'fs';
import { randomUUID } from 'crypto';
import { DDL } from './queries.constant';
import { QueryBuilder } from '../utils/QueryBuilder';

export type Db = BetterSqlite3.Database;

// ── Types ────────────────────────────────────────────────────────────────────

interface LegacyHolding {
  ticker: string;
  shares: number;
  costBasis: number;
  type: string;
  source: string;
}

interface LegacyCall {
  id?: string;
  title: string;
  quarter: string;
  date: string;
  thesis: string;
  tickers: string[];
  snapshot: Record<string, unknown>;
  createdAt: string;
}

// ── Main Export ──────────────────────────────────────────────────────────────

/**
 * Initialize and open the SQLite database.
 *
 * Steps:
 * 1. Create/open database file
 * 2. Enable WAL mode (concurrent read safety)
 * 3. Enable foreign keys
 * 4. Run DDL (create tables if missing)
 * 5. Migrate legacy JSON files (one-time)
 *
 * @param path Path to database file (default: ./market-screener.db)
 * @returns Opened database instance (wrap in DatabaseConnection for safe access)
 */
export function createDb(path = './market-screener.db'): Db {
  const db = new BetterSqlite3(path);
  db.pragma('journal_mode = WAL');
  db.pragma('foreign_keys = ON');
  db.exec(DDL);
  migrateJson(db);
  return db;
}

// ── Migration Helpers ────────────────────────────────────────────────────────

/**
 * Migrate legacy JSON files to SQLite (one-time, non-fatal).
 * Called automatically during database initialization.
 */
function migrateJson(db: Db): void {
  migratePortfolio(db);
  migrateCalls(db);
}

/**
 * Migrate portfolio.json → holdings table.
 * If portfolio.json exists, import all holdings and rename to portfolio.json.migrated.
 * If import fails, leave portfolio.json in place (non-fatal).
 */
function migratePortfolio(db: Db): void {
  const src = './portfolio.json';
  if (!existsSync(src)) return;

  try {
    const { holdings } = JSON.parse(readFileSync(src, 'utf8')) as {
      holdings: LegacyHolding[];
    };

    const insertAll = db.transaction((rows: LegacyHolding[]) => {
      for (const h of rows) {
        const qb = new QueryBuilder('MIGRATION_QUERIES.HOLDINGS_INSERT_OR_IGNORE', [
          h.ticker.toUpperCase(),
          h.shares,
          h.costBasis ?? 0,
          h.type ?? 'stock',
          h.source ?? 'Manual',
        ]);
        db.prepare(qb.sql).run(...qb.queryParams);
      }
    });

    insertAll(holdings);
    renameSync(src, `${src}.migrated`);
  } catch {
    // Non-fatal: leave portfolio.json in place if migration fails
  }
}

/**
 * Migrate market-calls.json → market_calls table.
 * If market-calls.json exists, import all calls and rename to market-calls.json.migrated.
 * If import fails, leave market-calls.json in place (non-fatal).
 */
function migrateCalls(db: Db): void {
  const src = './market-calls.json';
  if (!existsSync(src)) return;

  try {
    const { calls } = JSON.parse(readFileSync(src, 'utf8')) as {
      calls: LegacyCall[];
    };

    const insertAll = db.transaction((rows: LegacyCall[]) => {
      for (const c of rows) {
        const qb = new QueryBuilder('MIGRATION_QUERIES.MARKET_CALLS_INSERT_OR_IGNORE', [
          c.id ?? randomUUID(),
          c.title,
          c.quarter,
          c.date,
          c.thesis,
          JSON.stringify(c.tickers ?? []),
          JSON.stringify(c.snapshot ?? {}),
          c.createdAt,
        ]);
        db.prepare(qb.sql).run(...qb.queryParams);
      }
    });

    insertAll(calls);
    renameSync(src, `${src}.migrated`);
  } catch {
    // Non-fatal: leave market-calls.json in place if migration fails
  }
}