/**
 * Database configuration types and loader.
 * Supports SQLite (local) and PostgreSQL (production) via environment variables.
 */

export interface SqliteConfig {
  path: string;
}

export interface PostgresConfig {
  host: string;
  port: number;
  database: string;
  user: string;
  password: string;
}

export interface PostgresUrlConfig {
  connectionString: string;
}

export type DatabaseType = 'sqlite' | 'postgres';

export interface DatabaseConfig {
  type: DatabaseType;
  sqlite?: SqliteConfig;
  postgres?: PostgresConfig | PostgresUrlConfig;
}

function getEnvVar(name: string, defaultValue?: string): string {
  const value = process.env[name];
  if (value === undefined) {
    if (defaultValue !== undefined) {
      return defaultValue;
    }
    throw new Error(`Missing required environment variable: ${name}`);
  }
  return value;
}

export function loadConfig(): DatabaseConfig {
  const type = getEnvVar('PULSE_DATABASE_TYPE', 'sqlite') as DatabaseType;

  if (type === 'sqlite') {
    return {
      type: 'sqlite',
      sqlite: {
        path: getEnvVar('PULSE_SQLITE_PATH', './data/pulse.db'),
      },
    };
  }

  if (type === 'postgres') {
    const connectionString = process.env.PULSE_DATABASE_URL;
    
    if (connectionString) {
      return {
        type: 'postgres',
        postgres: { connectionString },
      };
    }

    return {
      type: 'postgres',
      postgres: {
        host: getEnvVar('PULSE_POSTGRES_HOST'),
        port: parseInt(getEnvVar('PULSE_POSTGRES_PORT', '5432'), 10),
        database: getEnvVar('PULSE_POSTGRES_DATABASE'),
        user: getEnvVar('PULSE_POSTGRES_USER'),
        password: getEnvVar('PULSE_POSTGRES_PASSWORD'),
      },
    };
  }

  throw new Error(`Unsupported database type: ${type}. Use 'sqlite' or 'postgres'.`);
}

export function validateConfig(config: DatabaseConfig): void {
  if (config.type === 'sqlite') {
    if (!config.sqlite) {
      throw new Error('SQLite configuration missing');
    }
    if (!config.sqlite.path) {
      throw new Error('SQLite path is required');
    }
  } else if (config.type === 'postgres') {
    if (!config.postgres) {
      throw new Error('PostgreSQL configuration missing');
    }
  }
}