import { Pool, type PoolClient, type QueryResult, type QueryResultRow } from "pg";
import { readFileSync, existsSync, writeFileSync } from "fs";
import { resolve } from "path";

interface DbConfig {
  host: string;
  port: number;
  database: string;
  user: string;
  password: string;
  ssl?: boolean;
}

const CONFIG_PATH = resolve(process.cwd(), "data", "db-config.json");

let pool: Pool | null = null;
let currentConfig: DbConfig | null = null;

function loadConfigFromEnv(): DbConfig {
  return {
    host: process.env.FINANCE_DB_HOST || process.env.DB_HOST || "localhost",
    port: parseInt(process.env.FINANCE_DB_PORT || process.env.DB_PORT || "5432", 10),
    database: process.env.FINANCE_DB_NAME || process.env.DB_NAME || "postgres",
    user: process.env.FINANCE_DB_USER || process.env.DB_USER || "postgres",
    password: process.env.FINANCE_DB_PASSWORD || process.env.DB_PASSWORD || "",
    ssl: process.env.FINANCE_DB_SSL === "true" || process.env.DB_SSL === "true",
  };
}

function loadConfigFromFile(): DbConfig | null {
  if (!existsSync(CONFIG_PATH)) return null;
  try {
    const raw = readFileSync(CONFIG_PATH, "utf-8");
    const parsed = JSON.parse(raw) as DbConfig;
    if (parsed.host && parsed.database && parsed.user) {
      return parsed;
    }
    return null;
  } catch {
    return null;
  }
}

function createPool(config: DbConfig): Pool {
  return new Pool({
    host: config.host,
    port: config.port,
    database: config.database,
    user: config.user,
    password: config.password,
    ssl: config.ssl ? { rejectUnauthorized: false } : false,
    max: 10,
    connectionTimeoutMillis: 10000,
  });
}

export function getPool(): Pool {
  if (!pool) {
    const fileConfig = loadConfigFromFile();
    const envConfig = loadConfigFromEnv();
    currentConfig = fileConfig || envConfig;
    if (!currentConfig) {
      throw new Error("Database configuration not found");
    }
    pool = createPool(currentConfig);
    pool.on("error", (err) => {
      console.error("Unexpected finance DB pool error:", err);
    });
  }
  return pool;
}

export async function query<T extends QueryResultRow = any>(sql: string, params?: any[]): Promise<QueryResult<T>> {
  const p = getPool();
  return p.query<T>(sql, params);
}

// Клиент для ручных транзакций (BEGIN/COMMIT/ROLLBACK) — см. google-auth.ts (синхронизация зарплат)
export async function getPoolClient(): Promise<PoolClient> {
  const p = getPool();
  return p.connect();
}

export async function testConnection(config: DbConfig): Promise<{ ok: boolean; message: string }> {
  const testPool = createPool(config);
  try {
    const client = await testPool.connect();
    try {
      await client.query("SELECT 1");
      return { ok: true, message: "Подключение успешно" };
    } finally {
      client.release();
    }
  } catch (err: any) {
    return { ok: false, message: err?.message || "Ошибка подключения" };
  } finally {
    await testPool.end();
  }
}

export function setConfig(config: DbConfig): void {
  if (pool) {
    pool.end().catch(() => {});
  }
  pool = null;
  currentConfig = config;
  writeFileSync(CONFIG_PATH, JSON.stringify(config, null, 2), "utf-8");
  pool = createPool(config);
  pool.on("error", (err) => {
    console.error("Unexpected finance DB pool error:", err);
  });
}

export function getConfig(): Omit<DbConfig, "password"> | null {
  if (!currentConfig) return null;
  const { password: _password, ...rest } = currentConfig;
  return rest;
}

export async function isConnected(): Promise<boolean> {
  try {
    await query("SELECT 1");
    return true;
  } catch {
    return false;
  }
}

const CONNECTION_ERROR_CODES = new Set(["57P01", "57P02", "57P03", "08000", "08001", "08003", "08006"]);

export function isConnectionError(err: unknown): boolean {
  if (!(err instanceof Error)) return false;
  const code = (err as any).code;
  if (code && CONNECTION_ERROR_CODES.has(code)) return true;
  const msg = err.message.toLowerCase();
  return msg.includes("econnrefused") || msg.includes("etimedout") || msg.includes("enotfound") ||
    msg.includes("connection terminated") || msg.includes("connection timeout") ||
    msg.includes("закрытие подключения") || msg.includes("the database system is shutting down");
}