'use strict'

const url = require('url')
const fetch = require('minipass-fetch')
const pkg = require('./package.json')
const retry = require('promise-retry')
let ssri

const Minipass = require('minipass')
const MinipassPipeline = require('minipass-pipeline')
const getAgent = require('./agent')
const setWarning = require('./warning')

const configureOptions = require('./utils/configure-options')
const iterableToObject = require('./utils/iterable-to-object')
const makePolicy = require('./utils/make-policy')

const isURL = /^https?:/
const USER_AGENT = `${pkg.name}/${pkg.version} (+https://npm.im/${pkg.name})`

const RETRY_ERRORS = [
  'ECONNRESET', // remote socket closed on us
  'ECONNREFUSED', // remote host refused to open connection
  'EADDRINUSE', // failed to bind to a local port (proxy?)
  'ETIMEDOUT' // someone in the transaction is WAY TOO SLOW
  // Known codes we do NOT retry on:
  // ENOTFOUND (getaddrinfo failure. Either bad hostname, or offline)
]

const RETRY_TYPES = [
  'request-timeout'
]

// https://fetch.spec.whatwg.org/#http-network-or-cache-fetch
module.exports = cachingFetch
cachingFetch.defaults = function (_uri, _opts) {
  const fetch = this
  if (typeof _uri === 'object') {
    _opts = _uri
    _uri = null
  }

  function defaultedFetch (uri, opts) {
    const finalOpts = Object.assign({}, _opts || {}, opts || {})
    return fetch(uri || _uri, finalOpts)
  }

  defaultedFetch.defaults = fetch.defaults
  defaultedFetch.delete = fetch.delete
  return defaultedFetch
}

cachingFetch.delete = cacheDelete
function cacheDelete (uri, opts) {
  opts = configureOptions(opts)
  if (opts.cacheManager) {
    const req = new fetch.Request(uri, {
      method: opts.method,
      headers: opts.headers
    })
    return opts.cacheManager.delete(req, opts)
  }
}

function initializeSsri () {
  if (!ssri) {
    ssri = require('ssri')
  }
}

function cachingFetch (uri, _opts) {
  const opts = configureOptions(_opts)

  if (opts.integrity) {
    initializeSsri()
    // if verifying integrity, fetch must not decompress
    opts.compress = false
  }

  const isCachable = (
    (
      opts.method === 'GET' ||
      opts.method === 'HEAD'
    ) &&
      Boolean(opts.cacheManager) &&
      opts.cache !== 'no-store' &&
      opts.cache !== 'reload'
  )

  if (isCachable) {
    const req = new fetch.Request(uri, {
      method: opts.method,
      headers: opts.headers
    })

    return opts.cacheManager.match(req, opts).then(res => {
      if (res) {
        const warningCode = (res.headers.get('Warning') || '').match(/^\d+/)
        if (warningCode && +warningCode >= 100 && +warningCode < 200) {
          // https://tools.ietf.org/html/rfc7234#section-4.3.4
          //
          // If a stored response is selected for update, the cache MUST:
          //
          // * delete any Warning header fields in the stored response with
          //   warn-code 1xx (see Section 5.5);
          //
          // * retain any Warning header fields in the stored response with
          //   warn-code 2xx;
          //
          res.headers.delete('Warning')
        }

        if (opts.cache === 'default' && !isStale(req, res)) {
          return res
        }

        if (opts.cache === 'default' || opts.cache === 'no-cache') {
          return conditionalFetch(req, res, opts)
        }

        if (opts.cache === 'force-cache' || opts.cache === 'only-if-cached') {
          //   112 Disconnected operation
          // SHOULD be included if the cache is intentionally disconnected from
          // the rest of the network for a period of time.
          // (https://tools.ietf.org/html/rfc2616#section-14.46)
          setWarning(res, 112, 'Disconnected operation')
          return res
        }
      }

      if (!res && opts.cache === 'only-if-cached') {
        const errorMsg = `request to ${
          uri
        } failed: cache mode is 'only-if-cached' but no cached response available.`

        const err = new Error(errorMsg)
        err.code = 'ENOTCACHED'
        throw err
      }

      // Missing cache entry, or mode is default (if stale), reload, no-store
      return remoteFetch(req.url, opts)
    })
  }
  return remoteFetch(uri, opts)
}

// https://tools.ietf.org/html/rfc7234#section-4.2
function isStale (req, res) {
  const _req = {
    url: req.url,
    method: req.method,
    headers: iterableToObject(req.headers)
  }

  const policy = makePolicy(req, res)

  const responseTime = res.headers.get('x-local-cache-time') ||
    /* istanbul ignore next - would be weird to get a 'stale'
     * response that didn't come from cache with a cache time header */
    (res.headers.get('date') || 0)

  policy._responseTime = new Date(responseTime)

  const bool = !policy.satisfiesWithoutRevalidation(_req)
  const headers = policy.responseHeaders()
  if (headers.warning && /^113\b/.test(headers.warning)) {
    // Possible to pick up a rfc7234 warning at this point.
    // This is kind of a weird place to stick this, should probably go
    // in cachingFetch.  But by putting it here, we save an extra
    // CachePolicy object construction.
    res.headers.append('warning', headers.warning)
  }
  return bool
}

function mustRevalidate (res) {
  return (res.headers.get('cache-control') || '').match(/must-revalidate/i)
}

function conditionalFetch (req, cachedRes, opts) {
  const _req = {
    url: req.url,
    method: req.method,
    headers: Object.assign({}, opts.headers || {})
  }

  const policy = makePolicy(req, cachedRes)
  opts.headers = policy.revalidationHeaders(_req)

  return remoteFetch(req.url, opts)
    .then(condRes => {
      const revalidatedPolicy = policy.revalidatedPolicy(_req, {
        status: condRes.status,
        headers: iterableToObject(condRes.headers)
      })

      if (condRes.status >= 500 && !mustRevalidate(cachedRes)) {
        //   111 Revalidation failed
        // MUST be included if a cache returns a stale response because an
        // attempt to revalidate the response failed, due to an inability to
        // reach the server.
        // (https://tools.ietf.org/html/rfc2616#section-14.46)
        setWarning(cachedRes, 111, 'Revalidation failed')
        return cachedRes
      }

      if (condRes.status === 304) { // 304 Not Modified
        // Create a synthetic response from the cached body and original req
        const synthRes = new fetch.Response(cachedRes.body, condRes)
        return opts.cacheManager.put(req, synthRes, opts)
          .then(newRes => {
            // Get the list first, because if we delete while iterating,
            // it'll throw off the count and not make it through all
            // of them.
            const newHeaders = revalidatedPolicy.policy.responseHeaders()
            const toDelete = [...newRes.headers.keys()]
              .filter(k => !newHeaders[k])
            for (const key of toDelete) {
              newRes.headers.delete(key)
            }
            for (const [key, val] of Object.entries(newHeaders)) {
              newRes.headers.set(key, val)
            }
            return newRes
          })
      }

      return condRes
    })
    .then(res => res)
    .catch(err => {
      if (mustRevalidate(cachedRes)) {
        throw err
      } else {
        //   111 Revalidation failed
        // MUST be included if a cache returns a stale response because an
        // attempt to revalidate the response failed, due to an inability to
        // reach the server.
        // (https://tools.ietf.org/html/rfc2616#section-14.46)
        setWarning(cachedRes, 111, 'Revalidation failed')
        //   199 Miscellaneous warning
        // The warning text MAY include arbitrary information to be presented to
        // a human user, or logged. A system receiving this warning MUST NOT take
        // any automated action, besides presenting the warning to the user.
        // (https://tools.ietf.org/html/rfc2616#section-14.46)
        setWarning(
          cachedRes,
          199,
          `Miscellaneous Warning ${err.code}: ${err.message}`
        )

        return cachedRes
      }
    })
}

function remoteFetchHandleIntegrity (res, integrity) {
  const oldBod = res.body
  const newBod = ssri.integrityStream({
    integrity
  })
  return new fetch.Response(new MinipassPipeline(oldBod, newBod), res)
}

function remoteFetch (uri, opts) {
  const agent = getAgent(uri, opts)
  const headers = Object.assign({
    connection: agent ? 'keep-alive' : 'close',
    'user-agent': USER_AGENT
  }, opts.headers || {})

  const reqOpts = {
    agent,
    body: opts.body,
    compress: opts.compress,
    follow: opts.follow,
    headers: new fetch.Headers(headers),
    method: opts.method,
    redirect: 'manual',
    size: opts.size,
    counter: opts.counter,
    timeout: opts.timeout
  }

  return retry(
    (retryHandler, attemptNum) => {
      const req = new fetch.Request(uri, reqOpts)
      return fetch(req)
        .then((res) => {
          if (opts.integrity) {
            res = remoteFetchHandleIntegrity(res, opts.integrity)
          }

          res.headers.set('x-fetch-attempts', attemptNum)

          const isStream = Minipass.isStream(req.body)

          if (opts.cacheManager) {
            const isMethodGetHead = (
              req.method === 'GET' ||
              req.method === 'HEAD'
            )

            const isCachable = (
              opts.cache !== 'no-store' &&
              isMethodGetHead &&
              makePolicy(req, res).storable() &&
              res.status === 200 // No other statuses should be stored!
            )

            if (isCachable) {
              return opts.cacheManager.put(req, res, opts)
            }

            if (!isMethodGetHead) {
              return opts.cacheManager.delete(req).then(() => {
                if (res.status >= 500 && req.method !== 'POST' && !isStream) {
                  if (typeof opts.onRetry === 'function') {
                    opts.onRetry(res)
                  }

                  return retryHandler(res)
                }

                return res
              })
            }
          }

          const isRetriable = (
            req.method !== 'POST' &&
            !isStream &&
            (
              res.status === 408 || // Request Timeout
              res.status === 420 || // Enhance Your Calm (usually Twitter rate-limit)
              res.status === 429 || // Too Many Requests ("standard" rate-limiting)
              res.status >= 500 // Assume server errors are momentary hiccups
            )
          )

          if (isRetriable) {
            if (typeof opts.onRetry === 'function') {
              opts.onRetry(res)
            }

            return retryHandler(res)
          }

          if (!fetch.isRedirect(res.status)) {
            return res
          }
          if (opts.redirect === 'manual') {
            return res
          }
          // if (!fetch.isRedirect(res.status) || opts.redirect === 'manual') {
          //   return res
          // }

          // handle redirects - matches behavior of fetch: https://github.com/bitinn/node-fetch
          if (opts.redirect === 'error') {
            const err = new fetch.FetchError(`redirect mode is set to error: ${uri}`, 'no-redirect', { code: 'ENOREDIRECT' })
            throw err
          }

          if (!res.headers.get('location')) {
            const err = new fetch.FetchError(`redirect location header missing at: ${uri}`, 'no-location', { code: 'EINVALIDREDIRECT' })
            throw err
          }

          if (req.counter >= req.follow) {
            const err = new fetch.FetchError(`maximum redirect reached at: ${uri}`, 'max-redirect', { code: 'EMAXREDIRECT' })
            throw err
          }

          const resolvedUrlParsed = new url.URL(res.headers.get('location'), req.url)
          const resolvedUrl = url.format(resolvedUrlParsed)
          const redirectURL = (isURL.test(res.headers.get('location')))
            ? new url.URL(res.headers.get('location'))
            : resolvedUrlParsed

          // 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
          if (new url.URL(req.url).hostname !== redirectURL.hostname) {
            req.headers.delete('authorization')
          }

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

          opts.headers = {}
          req.headers.forEach((value, name) => {
            opts.headers[name] = value
          })

          opts.counter = ++req.counter
          return cachingFetch(resolvedUrl, opts)
        })
        .catch(err => {
          const code = (err.code === 'EPROMISERETRY')
            ? err.retried.code
            : err.code

          const isRetryError = (
            RETRY_ERRORS.indexOf(code) === -1 &&
            RETRY_TYPES.indexOf(err.type) === -1
          )

          if (req.method === 'POST' || isRetryError) {
            throw err
          }

          if (typeof opts.onRetry === 'function') {
            opts.onRetry(err)
          }

          return retryHandler(err)
        })
    },
    opts.retry
  ).catch(err => {
    if (err.status >= 400 && err.type !== 'system') {
      // this is an HTTP response "error" that we care about
      return err
    }

    throw err
  })
}