import { Injectable, OnModuleDestroy, OnModuleInit } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { drizzle } from 'drizzle-orm/node-postgres';
import { Pool } from 'pg';
import * as schema from './schema';
import { runMigrations } from './migrations/migrate';

@Injectable()
export class DatabaseService implements OnModuleInit, OnModuleDestroy {
  private readonly pool: Pool;
  private readonly db: ReturnType<typeof drizzle>;

  constructor(private configService: ConfigService) {
    // Create the PostgreSQL pool
    const connectionString = this.getDatabaseConnectionString();
    this.pool = new Pool({
      connectionString,
    });

    // Create the Drizzle ORM instance
    this.db = drizzle(this.pool, { schema });
  }

  async onModuleInit() {
    // Log database connection
    console.log('Connecting to database...');

    // Test the connection
    try {
      const client = await this.pool.connect();
      try {
        await client.query('SELECT NOW()');
        console.log('Database connection established successfully');
      } finally {
        client.release();
      }
    } catch (error) {
      console.error('Failed to connect to database:', error.message);
      throw error;
    }

    // Run migrations in all environments
    const result = await runMigrations({ migrationsFolder: './src/database/migrations/sql' });

    // In production, we want to fail if migrations fail
    if (!result.success && this.configService.get('NODE_ENV') === 'production') {
      throw result.error;
    }
  }

  async onModuleDestroy() {
    // Close the database connection
    await this.pool.end();
    console.log('Database connection closed');
  }

  // Get the database connection string from environment variables
  private getDatabaseConnectionString(): string {
    // First try to get the full DATABASE_URL
    const databaseUrl = this.configService.get<string>('DATABASE_URL');
    if (databaseUrl) {
      return databaseUrl;
    }

    // If DATABASE_URL is not provided, construct it from individual variables
    const password = this.configService.get<string>('POSTGRES_PASSWORD');
    const username = this.configService.get<string>('POSTGRES_USER');
    const host = this.configService.get<string>('POSTGRES_HOST');
    const port = this.configService.get<string>('POSTGRES_PORT');
    const database = this.configService.get<string>('POSTGRES_DB');

    const missingVars: string[] = [];
    if (!password) missingVars.push('POSTGRES_PASSWORD');
    if (!username) missingVars.push('POSTGRES_USER');
    if (!host) missingVars.push('POSTGRES_HOST');
    if (!port) missingVars.push('POSTGRES_PORT');
    if (!database) missingVars.push('POSTGRES_DB');

    if (missingVars.length > 0) {
      throw new Error(
        `Database configuration is missing. Missing variables: ${missingVars.join(', ')}. Please check your .env file.`,
      );
    }

    return `postgres://${username}:${password}@${host}:${port}/${database}`;
  }

  // Get the Drizzle ORM instance
  getDb() {
    return this.db;
  }

  // Get the PostgreSQL pool
  getPool() {
    return this.pool;
  }
}