import koa from 'koa';
import Logger from '../../helper/logger/Logger';

type MiddlewareOptions = {
  logger: Logger;
};

/**
 * Global error handler which always output errors in JSON format
 * @param logger Logger to inject
 */
export default function errorHandler(
  options: MiddlewareOptions
): koa.Middleware {
  const { logger } = options;
  return async function(ctx: koa.Context, next): Promise<void> {
    try {
      await next();
    } catch (err) {
      logger.error(err.message);
      if ('stack' in err) logger.trace(err.stack);

      // Unexpected error, probably due to bugs
      let status = 500;
      let message = 'Internal server error.';

      // Exceptions with status code, probably doe to invalid request, etc.
      if (typeof err.status === 'number') {
        status = err.status;
        message = err.message;
      }

      const out: any = { status: 'ng', message };
      if (process.env.NODE_ENV !== 'production' && 'stack' in err) {
        out.stack = err.stack;
      }

      ctx.status = status;
      ctx.body = out;
    }
  };
}