'use strict'

/**
 * index.js
 *
 * a request API compatible with window.fetch
 */

const url = require('url')
const http = require('http')
const https = require('https')
const zlib = require('zlib')
const PassThrough = require('stream').PassThrough

const Body = require('./body.js')
const writeToStream = Body.writeToStream
const Response = require('./response')
const Headers = require('./headers')
const Request = require('./request')
const getNodeRequestOptions = Request.getNodeRequestOptions
const FetchError = require('./fetch-error')
const isURL = /^https?:/

/**
 * Fetch function
 *
 * @param   Mixed    url   Absolute url or Request instance
 * @param   Object   opts  Fetch options
 * @return  Promise
 */
exports = module.exports = fetch
function fetch (uri, opts) {
  // allow custom promise
  if (!fetch.Promise) {
    throw new Error('native promise missing, set fetch.Promise to your favorite alternative')
  }

  Body.Promise = fetch.Promise

  // wrap http.request into fetch
  return new fetch.Promise((resolve, reject) => {
    // build request object
    const request = new Request(uri, opts)
    const options = getNodeRequestOptions(request)

    const send = (options.protocol === 'https:' ? https : http).request

    // http.request only support string as host header, this hack make custom host header possible
    if (options.headers.host) {
      options.headers.host = options.headers.host[0]
    }

    // send request
    const req = send(options)
    let reqTimeout

    if (request.timeout) {
      req.once('socket', socket => {
        reqTimeout = setTimeout(() => {
          req.abort()
          reject(new FetchError(`network timeout at: ${request.url}`, 'request-timeout'))
        }, request.timeout)
      })
    }

    req.on('error', err => {
      clearTimeout(reqTimeout)
      reject(new FetchError(`request to ${request.url} failed, reason: ${err.message}`, 'system', err))
    })

    req.on('response', res => {
      clearTimeout(reqTimeout)

      // handle redirect
      if (fetch.isRedirect(res.statusCode) && request.redirect !== 'manual') {
        if (request.redirect === 'error') {
          reject(new FetchError(`redirect mode is set to error: ${request.url}`, 'no-redirect'))
          return
        }

        if (request.counter >= request.follow) {
          reject(new FetchError(`maximum redirect reached at: ${request.url}`, 'max-redirect'))
          return
        }

        if (!res.headers.location) {
          reject(new FetchError(`redirect location header missing at: ${request.url}`, 'invalid-redirect'))
          return
        }
        // Remove authorization if changing hostnames (but not if just
        // changing ports or protocols).  This matches the behavior of request:
        // https://github.com/request/request/blob/b12a6245/lib/redirect.js#L134-L138
        const resolvedUrl = url.resolve(request.url, res.headers.location)
        let redirectURL = ''
        if (!isURL.test(res.headers.location)) {
          redirectURL = url.parse(resolvedUrl)
        } else {
          redirectURL = url.parse(res.headers.location)
        }
        if (url.parse(request.url).hostname !== redirectURL.hostname) {
          request.headers.delete('authorization')
        }

        // per fetch spec, for POST request with 301/302 response, or any request with 303 response, use GET when following redirect
        if (res.statusCode === 303 ||
          ((res.statusCode === 301 || res.statusCode === 302) && request.method === 'POST')) {
          request.method = 'GET'
          request.body = null
          request.headers.delete('content-length')
        }

        request.counter++

        resolve(fetch(resolvedUrl, request))
        return
      }

      // normalize location header for manual redirect mode
      const headers = new Headers()
      for (const name of Object.keys(res.headers)) {
        if (Array.isArray(res.headers[name])) {
          for (const val of res.headers[name]) {
            headers.append(name, val)
          }
        } else {
          headers.append(name, res.headers[name])
        }
      }
      if (request.redirect === 'manual' && headers.has('location')) {
        headers.set('location', url.resolve(request.url, headers.get('location')))
      }

      // prepare response
      let body = res.pipe(new PassThrough())
      const responseOptions = {
        url: request.url,
        status: res.statusCode,
        statusText: res.statusMessage,
        headers: headers,
        size: request.size,
        timeout: request.timeout
      }

      // HTTP-network fetch step 16.1.2
      const codings = headers.get('Content-Encoding')

      // HTTP-network fetch step 16.1.3: handle content codings

      // in following scenarios we ignore compression support
      // 1. compression support is disabled
      // 2. HEAD request
      // 3. no Content-Encoding header
      // 4. no content response (204)
      // 5. content not modified response (304)
      if (!request.compress || request.method === 'HEAD' || codings === null || res.statusCode === 204 || res.statusCode === 304) {
        resolve(new Response(body, responseOptions))
        return
      }

      // Be less strict when decoding compressed responses, since sometimes
      // servers send slightly invalid responses that are still accepted
      // by common browsers.
      // Always using Z_SYNC_FLUSH is what cURL does.
      const zlibOptions = {
        flush: zlib.Z_SYNC_FLUSH,
        finishFlush: zlib.Z_SYNC_FLUSH
      }

      // for gzip
      if (codings === 'gzip' || codings === 'x-gzip') {
        body = body.pipe(zlib.createGunzip(zlibOptions))
        resolve(new Response(body, responseOptions))
        return
      }

      // for deflate
      if (codings === 'deflate' || codings === 'x-deflate') {
        // handle the infamous raw deflate response from old servers
        // a hack for old IIS and Apache servers
        const raw = res.pipe(new PassThrough())
        raw.once('data', chunk => {
          // see http://stackoverflow.com/questions/37519828
          if ((chunk[0] & 0x0F) === 0x08) {
            body = body.pipe(zlib.createInflate(zlibOptions))
          } else {
            body = body.pipe(zlib.createInflateRaw(zlibOptions))
          }
          resolve(new Response(body, responseOptions))
        })
        return
      }

      // otherwise, use response as-is
      resolve(new Response(body, responseOptions))
    })

    writeToStream(req, request)
  })
};

/**
 * Redirect code matching
 *
 * @param   Number   code  Status code
 * @return  Boolean
 */
fetch.isRedirect = code => code === 301 || code === 302 || code === 303 || code === 307 || code === 308

// expose Promise
fetch.Promise = global.Promise
exports.Headers = Headers
exports.Request = Request
exports.Response = Response
exports.FetchError = FetchError