// Copyright 2011 Mark Cavage, Inc.  All rights reserved.

const EventEmitter = require('events').EventEmitter
const util = require('util')

const assert = require('assert-plus')
const asn1 = require('@ldapjs/asn1')
const logger = require('../logger')

const messages = require('@ldapjs/messages')
const AbandonRequest = messages.AbandonRequest
const AddRequest = messages.AddRequest
const AddResponse = messages.AddResponse
const BindRequest = messages.BindRequest
const BindResponse = messages.BindResponse
const CompareRequest = messages.CompareRequest
const CompareResponse = messages.CompareResponse
const DeleteRequest = messages.DeleteRequest
const DeleteResponse = messages.DeleteResponse
const ExtendedRequest = messages.ExtensionRequest
const ExtendedResponse = messages.ExtensionResponse
const ModifyRequest = messages.ModifyRequest
const ModifyResponse = messages.ModifyResponse
const ModifyDNRequest = messages.ModifyDnRequest
const ModifyDNResponse = messages.ModifyDnResponse
const SearchRequest = messages.SearchRequest
const SearchEntry = messages.SearchResultEntry
const SearchReference = messages.SearchResultReference
const SearchResponse = require('./search_response')
const UnbindRequest = messages.UnbindRequest
const LDAPResult = messages.LdapResult

const Protocol = require('@ldapjs/protocol')

/// --- Globals

const BerReader = asn1.BerReader

/// --- API

function Parser (options = {}) {
  assert.object(options)

  EventEmitter.call(this)

  this.buffer = null
  this.log = options.log || logger
}
util.inherits(Parser, EventEmitter)

/**
 * The LDAP server/client implementations will receive data from a stream and feed
 * it into this method. This method will collect that data into an internal
 * growing buffer. As that buffer fills with enough data to constitute a valid
 * LDAP message, the data will be parsed, emitted as a message object, and
 * reset the buffer to account for any next message in the stream.
 */
Parser.prototype.write = function (data) {
  if (!data || !Buffer.isBuffer(data)) { throw new TypeError('data (buffer) required') }

  let nextMessage = null
  const self = this

  function end () {
    if (nextMessage) { return self.write(nextMessage) }

    return true
  }

  self.buffer = self.buffer ? Buffer.concat([self.buffer, data]) : data

  let ber = new BerReader(self.buffer)

  let foundSeq = false
  try {
    foundSeq = ber.readSequence()
  } catch (e) {
    this.emit('error', e)
  }

  if (!foundSeq || ber.remain < ber.length) {
    // ENOTENOUGH
    return false
  } else if (ber.remain > ber.length) {
    // ETOOMUCH

    // This is an odd branch. Basically, it is setting `nextMessage` to
    // a buffer that represents data part of a message subsequent to the one
    // being processed. It then re-creates `ber` as a representation of
    // the message being processed and advances its offset to the value
    // position of the TLV.

    // Set `nextMessage` to the bytes subsequent to the current message's
    // value bytes. That is, slice from the byte immediately following the
    // current message's value bytes until the end of the buffer.
    nextMessage = self.buffer.slice(ber.offset + ber.length)

    const currOffset = ber.offset
    ber = new BerReader(ber.buffer.subarray(0, currOffset + ber.length))
    ber.readSequence()

    assert.equal(ber.remain, ber.length)
  }

  // If we're here, ber holds the message, and nextMessage is temporarily
  // pointing at the next sequence of data (if it exists)
  self.buffer = null

  let message
  try {
    if (Object.prototype.toString.call(ber) === '[object BerReader]') {
      // Parse the BER into a JavaScript object representation. The message
      // objects require the full sequence in order to construct the object.
      // At this point, we have already read the sequence tag and length, so
      // we need to rewind the buffer a bit. The `.sequenceToReader` method
      // does this for us.
      message = messages.LdapMessage.parse(ber.sequenceToReader())
    } else {
      // Bail here if peer isn't speaking protocol at all
      message = this.getMessage(ber)
    }

    if (!message) {
      return end()
    }

    // TODO: find a better way to handle logging now that messages and the
    // server are decoupled. ~ jsumners 2023-02-17
    message.log = this.log
  } catch (e) {
    this.emit('error', e, message)
    return false
  }

  this.emit('message', message)
  return end()
}

Parser.prototype.getMessage = function (ber) {
  assert.ok(ber)

  const self = this

  const messageId = ber.readInt()
  const type = ber.readSequence()

  let Message
  switch (type) {
    case Protocol.operations.LDAP_REQ_ABANDON:
      Message = AbandonRequest
      break

    case Protocol.operations.LDAP_REQ_ADD:
      Message = AddRequest
      break

    case Protocol.operations.LDAP_RES_ADD:
      Message = AddResponse
      break

    case Protocol.operations.LDAP_REQ_BIND:
      Message = BindRequest
      break

    case Protocol.operations.LDAP_RES_BIND:
      Message = BindResponse
      break

    case Protocol.operations.LDAP_REQ_COMPARE:
      Message = CompareRequest
      break

    case Protocol.operations.LDAP_RES_COMPARE:
      Message = CompareResponse
      break

    case Protocol.operations.LDAP_REQ_DELETE:
      Message = DeleteRequest
      break

    case Protocol.operations.LDAP_RES_DELETE:
      Message = DeleteResponse
      break

    case Protocol.operations.LDAP_REQ_EXTENSION:
      Message = ExtendedRequest
      break

    case Protocol.operations.LDAP_RES_EXTENSION:
      Message = ExtendedResponse
      break

    case Protocol.operations.LDAP_REQ_MODIFY:
      Message = ModifyRequest
      break

    case Protocol.operations.LDAP_RES_MODIFY:
      Message = ModifyResponse
      break

    case Protocol.operations.LDAP_REQ_MODRDN:
      Message = ModifyDNRequest
      break

    case Protocol.operations.LDAP_RES_MODRDN:
      Message = ModifyDNResponse
      break

    case Protocol.operations.LDAP_REQ_SEARCH:
      Message = SearchRequest
      break

    case Protocol.operations.LDAP_RES_SEARCH_ENTRY:
      Message = SearchEntry
      break

    case Protocol.operations.LDAP_RES_SEARCH_REF:
      Message = SearchReference
      break

    case Protocol.operations.LDAP_RES_SEARCH:
      Message = SearchResponse
      break

    case Protocol.operations.LDAP_REQ_UNBIND:
      Message = UnbindRequest
      break

    default:
      this.emit('error',
        new Error('Op 0x' + (type ? type.toString(16) : '??') +
                        ' not supported'),
        new LDAPResult({
          messageId: messageId,
          protocolOp: type || Protocol.operations.LDAP_RES_EXTENSION
        }))

      return false
  }

  return new Message({
    messageId: messageId,
    log: self.log
  })
}

/// --- Exports

module.exports = Parser