/*
 * Licensed to Elasticsearch B.V. under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch B.V. licenses this file to you 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.
 */

'use strict'

const assert = require('assert')
const { inspect } = require('util')
const http = require('http')
const https = require('https')
const debug = require('debug')('elasticsearch')
const decompressResponse = require('decompress-response')
const pump = require('pump')
const INVALID_PATH_REGEX = /[^\u0021-\u00ff]/
const { TimeoutError, ConfigurationError } = require('./errors')

class Connection {
  constructor (opts = {}) {
    this.url = opts.url
    this.ssl = opts.ssl || null
    this.id = opts.id || stripAuth(opts.url.href)
    this.headers = opts.headers || null
    this.deadCount = 0
    this.resurrectTimeout = 0

    this._openRequests = 0
    this._status = opts.status || Connection.statuses.ALIVE
    this.roles = Object.assign({}, defaultRoles, opts.roles)

    if (!['http:', 'https:'].includes(this.url.protocol)) {
      throw new ConfigurationError(`Invalid protocol: '${this.url.protocol}'`)
    }

    if (typeof opts.agent === 'function') {
      this.agent = opts.agent()
    } else {
      const keepAliveFalse = opts.agent && opts.agent.keepAlive === false
      const agentOptions = Object.assign({}, {
        keepAlive: true,
        keepAliveMsecs: 1000,
        maxSockets: keepAliveFalse ? Infinity : 256,
        maxFreeSockets: 256
      }, opts.agent)
      this.agent = this.url.protocol === 'http:'
        ? new http.Agent(agentOptions)
        : new https.Agent(Object.assign({}, agentOptions, this.ssl))
    }

    this.makeRequest = this.url.protocol === 'http:'
      ? http.request
      : https.request
  }

  request (params, callback) {
    this._openRequests++
    var ended = false

    const requestParams = this.buildRequestObject(params)
    // https://github.com/nodejs/node/commit/b961d9fd83
    if (INVALID_PATH_REGEX.test(requestParams.path) === true) {
      callback(new TypeError(`ERR_UNESCAPED_CHARACTERS: ${requestParams.path}`), null)
      return { abort: () => {} }
    }

    debug('Starting a new request', params)
    const request = this.makeRequest(requestParams)

    // listen for the response event
    // TODO: handle redirects?
    request.on('response', response => {
      if (ended === false) {
        ended = true
        this._openRequests--

        if (params.asStream === true) {
          callback(null, response)
        } else {
          callback(null, decompressResponse(response))
        }
      }
    })

    // handles request timeout
    request.on('timeout', () => {
      if (ended === false) {
        ended = true
        this._openRequests--
        request.abort()
        callback(new TimeoutError('Request timed out', params), null)
      }
    })

    // handles request error
    request.on('error', err => {
      if (ended === false) {
        ended = true
        this._openRequests--
        callback(err, null)
      }
    })

    // updates the ended state
    request.on('abort', () => {
      debug('Request aborted', params)
      if (ended === false) {
        ended = true
        this._openRequests--
      }
    })

    // Disables the Nagle algorithm
    request.setNoDelay(true)

    // starts the request
    if (isStream(params.body) === true) {
      pump(params.body, request, err => {
        /* istanbul ignore if  */
        if (err != null && ended === false) {
          ended = true
          this._openRequests--
          callback(err, null)
        }
      })
    } else {
      request.end(params.body)
    }

    return request
  }

  // TODO: write a better closing logic
  close (callback = () => {}) {
    debug('Closing connection', this.id)
    if (this._openRequests > 0) {
      setTimeout(() => this.close(callback), 1000)
    } else {
      this.agent.destroy()
      callback()
    }
  }

  setRole (role, enabled) {
    if (validRoles.indexOf(role) === -1) {
      throw new ConfigurationError(`Unsupported role: '${role}'`)
    }
    if (typeof enabled !== 'boolean') {
      throw new ConfigurationError('enabled should be a boolean')
    }

    this.roles[role] = enabled
    return this
  }

  get status () {
    return this._status
  }

  set status (status) {
    assert(
      ~validStatuses.indexOf(status),
      `Unsupported status: '${status}'`
    )
    this._status = status
  }

  buildRequestObject (params) {
    const url = this.url
    const request = {
      protocol: url.protocol,
      hostname: url.hostname[0] === '['
        ? url.hostname.slice(1, -1)
        : url.hostname,
      hash: url.hash,
      search: url.search,
      pathname: url.pathname,
      path: '',
      href: url.href,
      origin: url.origin,
      port: url.port,
      headers: this.headers,
      auth: !!url.username === true || !!url.password === true
        ? `${url.username}:${url.password}`
        : undefined,
      agent: this.agent
    }

    const paramsKeys = Object.keys(params)
    for (var i = 0, len = paramsKeys.length; i < len; i++) {
      var key = paramsKeys[i]
      if (key === 'path') {
        request.pathname = resolve(request.pathname, params[key])
      } else if (key === 'querystring' && !!params[key] === true) {
        if (request.search === '') {
          request.search = '?' + params[key]
        } else {
          request.search += '&' + params[key]
        }
      } else if (key === 'headers') {
        request.headers = Object.assign({}, request.headers, params.headers)
      } else {
        request[key] = params[key]
      }
    }

    request.path = request.pathname + request.search

    return request
  }

  // Handles console.log and utils.inspect invocations.
  // We want to hide `agent` and `ssl` since they made
  // the logs very hard to read. The user can still
  // access them with `instance.agent` and `instance.ssl`.
  [inspect.custom] (depth, options) {
    return {
      url: this.url,
      id: this.id,
      headers: this.headers,
      deadCount: this.deadCount,
      resurrectTimeout: this.resurrectTimeout,
      _openRequests: this._openRequests,
      status: this.status,
      roles: this.roles
    }
  }
}

Connection.statuses = {
  ALIVE: 'alive',
  DEAD: 'dead'
}

Connection.roles = {
  MASTER: 'master',
  DATA: 'data',
  INGEST: 'ingest',
  ML: 'ml'
}

const defaultRoles = {
  [Connection.roles.MASTER]: true,
  [Connection.roles.DATA]: true,
  [Connection.roles.INGEST]: true,
  [Connection.roles.ML]: false
}

const validStatuses = Object.keys(Connection.statuses)
  .map(k => Connection.statuses[k])
const validRoles = Object.keys(Connection.roles)
  .map(k => Connection.roles[k])

function stripAuth (url) {
  if (url.indexOf('@') === -1) return url
  return url.slice(0, url.indexOf('//') + 2) + url.slice(url.indexOf('@') + 1)
}

function isStream (obj) {
  return obj != null && typeof obj.pipe === 'function'
}

function resolve (host, path) {
  const hostEndWithSlash = host[host.length - 1] === '/'
  const pathStartsWithSlash = path[0] === '/'

  if (hostEndWithSlash === true && pathStartsWithSlash === true) {
    return host + path.slice(1)
  } else if (hostEndWithSlash !== pathStartsWithSlash) {
    return host + path
  } else {
    return host + '/' + path
  }
}

module.exports = Connection