/*
 * 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 { URL } = require('url')
const debug = require('debug')('elasticsearch')
const Connection = require('../Connection')
const noop = () => {}

class BaseConnectionPool {
  constructor (opts) {
    // list of nodes and weights
    this.connections = []
    // how many nodes we have in our scheduler
    this.size = this.connections.length
    this.Connection = opts.Connection
    this.emit = opts.emit || noop
    this.auth = opts.auth || null
    this._ssl = opts.ssl
    this._agent = opts.agent
    this._proxy = opts.proxy || null
  }

  getConnection () {
    throw new Error('getConnection must be implemented')
  }

  markAlive () {
    return this
  }

  markDead () {
    return this
  }

  /**
   * Creates a new connection instance.
   */
  createConnection (opts) {
    if (typeof opts === 'string') {
      opts = this.urlToHost(opts)
    }

    if (this.auth !== null) {
      opts.auth = this.auth
    } else if (opts.url.username !== '' && opts.url.password !== '') {
      opts.auth = {
        username: decodeURIComponent(opts.url.username),
        password: decodeURIComponent(opts.url.password)
      }
    }

    if (opts.ssl == null) opts.ssl = this._ssl
    /* istanbul ignore else */
    if (opts.agent == null) opts.agent = this._agent
    /* istanbul ignore else */
    if (opts.proxy == null) opts.proxy = this._proxy

    const connection = new this.Connection(opts)

    for (const conn of this.connections) {
      if (conn.id === connection.id) {
        throw new Error(`Connection with id '${connection.id}' is already present`)
      }
    }

    return connection
  }

  /**
   * Adds a new connection to the pool.
   *
   * @param {object|string} host
   * @returns {ConnectionPool}
   */
  addConnection (opts) {
    if (Array.isArray(opts)) {
      return opts.forEach(o => this.addConnection(o))
    }

    if (typeof opts === 'string') {
      opts = this.urlToHost(opts)
    }

    const connectionById = this.connections.find(c => c.id === opts.id)
    const connectionByUrl = this.connections.find(c => c.id === opts.url.href)

    if (connectionById || connectionByUrl) {
      throw new Error(`Connection with id '${opts.id || opts.url.href}' is already present`)
    }

    this.update([...this.connections, opts])
    return this.connections[this.size - 1]
  }

  /**
   * Removes a new connection to the pool.
   *
   * @param {object} connection
   * @returns {ConnectionPool}
   */
  removeConnection (connection) {
    debug('Removing connection', connection)
    return this.update(this.connections.filter(c => c.id !== connection.id))
  }

  /**
   * Empties the connection pool.
   *
   * @returns {ConnectionPool}
   */
  empty (callback) {
    debug('Emptying the connection pool')
    var openConnections = this.size
    this.connections.forEach(connection => {
      connection.close(() => {
        if (--openConnections === 0) {
          this.connections = []
          this.size = this.connections.length
          callback()
        }
      })
    })
  }

  /**
   * Update the ConnectionPool with new connections.
   *
   * @param {array} array of connections
   * @returns {ConnectionPool}
   */
  update (nodes) {
    debug('Updating the connection pool')
    const newConnections = []
    const oldConnections = []

    for (const node of nodes) {
      // if we already have a given connection in the pool
      // we mark it as alive and we do not close the connection
      // to avoid socket issues
      const connectionById = this.connections.find(c => c.id === node.id)
      const connectionByUrl = this.connections.find(c => c.id === node.url.href)
      if (connectionById) {
        debug(`The connection with id '${node.id}' is already present`)
        this.markAlive(connectionById)
        newConnections.push(connectionById)
      // in case the user has passed a single url (or an array of urls),
      // the connection id will be the full href; to avoid closing valid connections
      // because are not present in the pool, we check also the node url,
      // and if is already present we update its id with the ES provided one.
      } else if (connectionByUrl) {
        connectionByUrl.id = node.id
        this.markAlive(connectionByUrl)
        newConnections.push(connectionByUrl)
      } else {
        newConnections.push(this.createConnection(node))
      }
    }

    const ids = nodes.map(c => c.id)
    // remove all the dead connections and old connections
    for (const connection of this.connections) {
      if (ids.indexOf(connection.id) === -1) {
        oldConnections.push(connection)
      }
    }

    // close old connections
    oldConnections.forEach(connection => connection.close())

    this.connections = newConnections
    this.size = this.connections.length

    return this
  }

  /**
   * Transforms the nodes objects to a host object.
   *
   * @param {object} nodes
   * @returns {array} hosts
   */
  nodesToHost (nodes, protocol) {
    const ids = Object.keys(nodes)
    const hosts = []

    for (var i = 0, len = ids.length; i < len; i++) {
      const node = nodes[ids[i]]
      // If there is no protocol in
      // the `publish_address` new URL will throw
      // the publish_address can have two forms:
      //   - ip:port
      //   - hostname/ip:port
      // if we encounter the second case, we should
      // use the hostname instead of the ip
      var address = node.http.publish_address
      const parts = address.split('/')
      // the url is in the form of hostname/ip:port
      if (parts.length > 1) {
        const hostname = parts[0]
        const port = parts[1].match(/((?::))(?:[0-9]+)$/g)[0].slice(1)
        address = `${hostname}:${port}`
      }

      address = address.slice(0, 4) === 'http'
        /* istanbul ignore next */
        ? address
        : `${protocol}//${address}`
      const roles = node.roles.reduce((acc, role) => {
        acc[role] = true
        return acc
      }, {})

      hosts.push({
        url: new URL(address),
        id: ids[i],
        roles: Object.assign({
          [Connection.roles.MASTER]: false,
          [Connection.roles.DATA]: false,
          [Connection.roles.INGEST]: false,
          [Connection.roles.ML]: false
        }, roles)
      })
    }

    return hosts
  }

  /**
   * Transforms an url string to a host object
   *
   * @param {string} url
   * @returns {object} host
   */
  urlToHost (url) {
    return {
      url: new URL(url)
    }
  }
}

module.exports = BaseConnectionPool
