/**
 * Copyright 2020 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @file Add built in plug and play web framework support for express using body-parser
 */

import { Framework, StandardHandler } from './framework'
import { Request, Response } from 'express'
import { getLogger } from '../logger'

export interface ExpressHandler {
  /** @public */
  (request: Request, response: Response): void
}

export interface ExpressMetadata {
  /** @public */
  request: Request

  /** @public */
  response: Response
}

/** @hidden */
export class Express implements Framework<ExpressHandler> {
  handle(standard: StandardHandler) {
    return (request: Request, response: Response) => {
      const metadata: ExpressMetadata = {
        request,
        response,
      }
      const logger = getLogger()
      standard(request.body, request.headers, { express: metadata })
      .then(({ status, body, headers }) => {
        if (headers) {
          for (const key in headers) {
            response.setHeader(key, headers[key]!)
          }
        }
        response.status(status).send(body)
      })
      .catch((e: Error) => {
        logger.error(e?.stack || e)
        response.status(500).send({ error: e.message || e })
      })
    }
  }

  isResponse(second: {}): second is Response {
    return typeof (second as Response).send === 'function'
  }
  isRequest(first: {}): first is Request {
    return typeof (first as Request).get === 'function'
  }

  check(first: {}, second: {}) {
    return this.isRequest(first) && this.isResponse(second)
  }
}

/** @hidden */
export const express = new Express()