import { resolve } from 'node:path';
import {
  CANARY_DEFAULT_PORT,
  CANARY_DEFAULT_UPSTREAM_PORT,
  type CanaryGatewayOptions,
} from './canary-gateway.js';

export interface CanaryRuntimeEnvironment {
  readonly CANARY_DIST_DIR?: string;
  readonly CANARY_PORT?: string;
  readonly CANARY_UPSTREAM_PORT?: string;
  readonly MULTI_SIMADMIN_GATEWAY_HOST?: string;
  readonly MULTI_SIMADMIN_GATEWAY_ALLOWED_HOSTS?: string;
  readonly MULTI_SIMADMIN_GATEWAY_TOKEN?: string;
  readonly MULTI_SIMADMIN_CUTOVER_ACK?: string;
}

export const PRODUCTION_CUTOVER_ACK = 'I ACKNOWLEDGE MULTI-SIMADMIN OWNS PORT 8788';

function environmentPort(value: string | undefined, name: string, fallback: number): number {
  if (value === undefined || value === '') return fallback;
  const port = Number(value);
  if (!Number.isInteger(port) || port < 1 || port > 65_535)
    throw new Error(`${name} must be an integer port`);
  return port;
}

export function readCanaryRuntimeOptions(
  environment: CanaryRuntimeEnvironment,
): CanaryGatewayOptions {
  const gatewayToken = environment.MULTI_SIMADMIN_GATEWAY_TOKEN;
  if (
    !gatewayToken ||
    Buffer.byteLength(gatewayToken) < 32 ||
    Buffer.byteLength(gatewayToken) > 512
  )
    throw new Error('Gateway token must contain between 32 and 512 bytes');
  return Object.freeze({
    distDir: resolve(environment.CANARY_DIST_DIR ?? 'apps/web/dist'),
    port: environmentPort(environment.CANARY_PORT, 'CANARY_PORT', CANARY_DEFAULT_PORT),
    upstreamPort: environmentPort(
      environment.CANARY_UPSTREAM_PORT,
      'CANARY_UPSTREAM_PORT',
      CANARY_DEFAULT_UPSTREAM_PORT,
    ),
    gatewayToken,
  });
}

export function readProductionGatewayRuntimeOptions(
  environment: CanaryRuntimeEnvironment,
): CanaryGatewayOptions {
  if (environment.MULTI_SIMADMIN_CUTOVER_ACK !== PRODUCTION_CUTOVER_ACK) {
    throw new Error(
      `Production gateway requires MULTI_SIMADMIN_CUTOVER_ACK=${PRODUCTION_CUTOVER_ACK}`,
    );
  }
  const options = readCanaryRuntimeOptions({ ...environment, CANARY_PORT: '8788' });
  const host = environment.MULTI_SIMADMIN_GATEWAY_HOST ?? options.host;
  const allowedHosts = environment.MULTI_SIMADMIN_GATEWAY_ALLOWED_HOSTS?.split(',')
    .map((value) => value.trim())
    .filter(Boolean);
  return Object.freeze({
    ...options,
    ...(host === undefined ? {} : { host }),
    ...(allowedHosts === undefined ? {} : { allowedHosts }),
    ownsProductionPort: true,
  });
}