import { plainToInstance } from 'class-transformer';
import { IsInt, IsNotEmpty, IsOptional, IsString, IsUrl, Max, Min, validateSync } from 'class-validator';

/** Environment variables read by the app. A missing or malformed required one stops the startup. */
export class EnvironmentVariables {
  @IsString()
  @IsNotEmpty()
  DATABASE_URL!: string;

  /** HTTPS only: the Hiboutik credentials are sent with HTTP Basic auth. */
  @IsUrl({ protocols: ['https'], require_protocol: true })
  HIBOUTIK_BASE_URL!: string;

  @IsString()
  @IsNotEmpty()
  HIBOUTIK_USERNAME!: string;

  @IsString()
  @IsNotEmpty()
  HIBOUTIK_PASSWORD!: string;

  @IsOptional()
  @IsInt()
  @Min(1)
  @Max(65535)
  PORT?: number;

  /** Comma-separated list of origins allowed by CORS. Empty or unset: CORS stays disabled. */
  @IsOptional()
  @IsString()
  CORS_ORIGINS?: string;

  /** Number of reverse proxies in front of the app (so the real client IP is used for rate limiting). Unset: no proxy. */
  @IsOptional()
  @IsInt()
  @Min(1)
  @Max(10)
  TRUST_PROXY?: number;
}

/** `ConfigModule` validation hook: fails fast with the names of the faulty variables (never their values, they may be secrets). */
export function validateEnv(config: Record<string, unknown>): Record<string, unknown> {
  const validated = plainToInstance(EnvironmentVariables, config, { enableImplicitConversion: true });
  const errors = validateSync(validated, { whitelist: false });

  if (errors.length > 0) {
    const details = errors.map((error) => `${error.property}: ${Object.values(error.constraints ?? {}).join(', ')}`).join('\n  ');
    throw new Error(`Invalid environment configuration:\n  ${details}`);
  }
  return config;
}