import fs from 'fs'
import request from 'request'
import stream from 'stream'
import logger from '@overleaf/logger'
import _ from 'lodash'
import BPromise from 'bluebird'
import { URL } from 'url'
import OError from '@overleaf/o-error'
import Settings from '@overleaf/settings'
import * as Versions from './Versions.js'
import * as Errors from './Errors.js'
import * as LocalFileWriter from './LocalFileWriter.js'
import * as HashManager from './HashManager.js'

const HTTP_REQUEST_TIMEOUT = 300 * 1000 // 5 minutes

/**
 * Container for functions that need to be mocked in tests
 *
 * TODO: Rewrite tests in terms of exported functions only
 */
export const _mocks = {}

class StringStream extends stream.Readable {
  _read() {}
}

_mocks.getMostRecentChunk = (projectId, historyId, callback) => {
  const path = `projects/${historyId}/latest/history`
  logger.debug({ projectId, historyId }, 'getting chunk from history service')
  _requestChunk({ path, json: true }, callback)
}

export function getMostRecentChunk(...args) {
  _mocks.getMostRecentChunk(...args)
}

export function getChunkAtVersion(projectId, historyId, version, callback) {
  const path = `projects/${historyId}/versions/${version}/history`
  logger.debug(
    { projectId, historyId, version },
    'getting chunk from history service for version'
  )
  _requestChunk({ path, json: true }, callback)
}

export function getMostRecentVersion(projectId, historyId, callback) {
  getMostRecentChunk(projectId, historyId, (error, chunk) => {
    if (error) {
      return callback(OError.tag(error))
    }
    const mostRecentVersion =
      chunk.chunk.startVersion + (chunk.chunk.history.changes || []).length
    const lastChange = _.last(
      _.sortBy(chunk.chunk.history.changes || [], x => x.timestamp)
    )
    // find the latest project and doc versions in the chunk
    _getLatestProjectVersion(projectId, chunk, (err1, projectVersion) =>
      _getLatestV2DocVersions(projectId, chunk, (err2, v2DocVersions) => {
        // return the project and doc versions
        const projectStructureAndDocVersions = {
          project: projectVersion,
          docs: v2DocVersions,
        }
        callback(
          err1 || err2,
          mostRecentVersion,
          projectStructureAndDocVersions,
          lastChange
        )
      })
    )
  })
}

function _requestChunk(options, callback) {
  _requestHistoryService(options, (err, chunk) => {
    if (err) {
      return callback(OError.tag(err))
    }
    if (
      chunk == null ||
      chunk.chunk == null ||
      chunk.chunk.startVersion == null
    ) {
      return callback(new OError('unexpected response'))
    }
    callback(null, chunk)
  })
}

function _getLatestProjectVersion(projectId, chunk, callback) {
  // find the initial project version
  let projectVersion =
    chunk.chunk.history.snapshot && chunk.chunk.history.snapshot.projectVersion
  // keep track of any errors
  let error = null
  // iterate over the changes in chunk to find the most recent project version
  for (const change of chunk.chunk.history.changes || []) {
    if (change.projectVersion != null) {
      if (
        projectVersion != null &&
        Versions.lt(change.projectVersion, projectVersion)
      ) {
        logger.warn(
          { projectId, chunk, projectVersion, change },
          'project structure version out of order in chunk'
        )
        if (!error) {
          error = new Errors.OpsOutOfOrderError(
            'project structure version out of order'
          )
        }
      } else {
        projectVersion = change.projectVersion
      }
    }
  }
  callback(error, projectVersion)
}

function _getLatestV2DocVersions(projectId, chunk, callback) {
  // find the initial doc versions (indexed by docId as this is immutable)
  const v2DocVersions =
    (chunk.chunk.history.snapshot &&
      chunk.chunk.history.snapshot.v2DocVersions) ||
    {}
  // keep track of any errors
  let error = null
  // iterate over the changes in the chunk to find the most recent doc versions
  for (const change of chunk.chunk.history.changes || []) {
    if (change.v2DocVersions != null) {
      for (const docId in change.v2DocVersions) {
        const docInfo = change.v2DocVersions[docId]
        const { v } = docInfo
        if (
          v2DocVersions[docId] &&
          v2DocVersions[docId].v != null &&
          Versions.lt(v, v2DocVersions[docId].v)
        ) {
          logger.warn(
            {
              projectId,
              docId,
              changeVersion: docInfo,
              previousVersion: v2DocVersions[docId],
            },
            'doc version out of order in chunk'
          )
          if (!error) {
            error = new Errors.OpsOutOfOrderError('doc version out of order')
          }
        } else {
          v2DocVersions[docId] = docInfo
        }
      }
    }
  }
  callback(error, v2DocVersions)
}

export function getProjectBlob(historyId, blobHash, callback) {
  logger.debug({ historyId, blobHash }, 'getting blob from history service')
  _requestHistoryService(
    { path: `projects/${historyId}/blobs/${blobHash}` },
    callback
  )
}

export function getProjectBlobStream(historyId, blobHash, callback) {
  logger.debug(
    { historyId, blobHash },
    'getting blob stream from history service'
  )
  _requestHistoryServiceStream(
    { path: `projects/${historyId}/blobs/${blobHash}` },
    callback
  )
}

export function sendChanges(
  projectId,
  historyId,
  changes,
  endVersion,
  callback
) {
  logger.debug(
    { projectId, historyId, endVersion },
    'sending changes to history service'
  )
  _requestHistoryService(
    {
      path: `projects/${historyId}/legacy_changes`,
      qs: { end_version: endVersion },
      method: 'POST',
      json: changes,
    },
    error => {
      if (error) {
        OError.tag(error, 'failed to send changes to v1', {
          projectId,
          historyId,
          endVersion,
          errorCode: error.code,
          statusCode: error.statusCode,
          body: error.body,
        })
        logger.warn(error)
        return callback(error)
      }
      callback()
    }
  )
}

export function createBlobForUpdate(projectId, historyId, update, callback) {
  callback = _.once(callback)

  if (update.doc != null && update.docLines != null) {
    const stringStream = new StringStream()
    stringStream.push(update.docLines)
    stringStream.push(null)

    LocalFileWriter.bufferOnDisk(
      stringStream,
      `project-${projectId}-doc-${update.doc}`,
      (fsPath, cb) => {
        _createBlob(historyId, fsPath, cb)
      },
      callback
    )
  } else if (update.file != null && update.url != null) {
    // Rewrite the filestore url to point to the location in the local
    // settings for this service (this avoids problems with cross-
    // datacentre requests when running filestore in multiple locations).
    const { pathname: fileStorePath } = new URL(update.url)
    const urlMatch = /^\/project\/([0-9a-f]{24})\/file\/([0-9a-f]{24})$/.exec(
      fileStorePath
    )
    if (urlMatch == null) {
      return callback(new OError('invalid file for blob creation'))
    }
    if (urlMatch[1] !== projectId) {
      return callback(new OError('invalid project for blob creation'))
    }
    const fileId = urlMatch[2]
    const fileStoreStream = request.get({
      url: `${Settings.apis.filestore.url}/project/${projectId}/file/${fileId}`,
      timeout: HTTP_REQUEST_TIMEOUT,
    })
    fileStoreStream.pause()
    fileStoreStream.on('error', err => {
      callback(OError.tag(err, 'error from filestore', { url: update.url }))
    })
    fileStoreStream.on('response', response => {
      if (response.statusCode >= 200 && response.statusCode < 300) {
        LocalFileWriter.bufferOnDisk(
          fileStoreStream,
          `project-${projectId}-file-${fileId}`,
          (fsPath, cb) => {
            _createBlob(historyId, fsPath, cb)
          },
          callback
        )
        fileStoreStream.resume() // start data flowing when ready
      } else if (response.statusCode === 404) {
        logger.warn(
          { projectId, historyId, fileStoreUrl: update.url },
          'File contents not found in filestore. Storing in history as an empty file'
        )
        const emptyStream = new StringStream()
        LocalFileWriter.bufferOnDisk(
          emptyStream,
          `project-${projectId}-file-${fileId}`,
          (fsPath, cb) => {
            _createBlob(historyId, fsPath, cb)
          },
          callback
        )
        fileStoreStream.resume() // Drain the filestore stream
        emptyStream.push(null) // send an EOF signal
      } else {
        const error = new OError(
          `bad response from filestore: ${response.statusCode}`,
          { url: update.url, statusCode: response.statusCode }
        )
        fileStoreStream.resume() // See https://github.com/overleaf/write_latex/wiki/Streams-and-pipes-in-Node.js#discard-data-if-necessary-in-the-response-handler
        callback(error)
      }
    })
  } else {
    const error = new OError('invalid update for blob creation')
    callback(error)
  }
}

function _createBlob(historyId, fsPath, _callback) {
  const callback = _.once(_callback)

  HashManager._getBlobHash(fsPath, (error, hash, byteLength) => {
    if (error) {
      return callback(OError.tag(error))
    }
    const outStream = fs.createReadStream(fsPath)

    outStream.on('error', err => {
      callback(
        OError.tag(err, 'error streaming file from disk', {
          fsPath,
          hash,
          byteLength,
        })
      )
    })

    logger.debug(
      { fsPath, hash, byteLength },
      'sending blob to history service'
    )
    _requestHistoryService(
      {
        method: 'PUT',
        path: `projects/${historyId}/blobs/${hash}`,
        body: outStream,
      },
      error => {
        if (error) {
          return callback(OError.tag(error))
        }
        callback(null, hash)
      }
    )
  })
}

export function initializeProject(historyId, callback) {
  _requestHistoryService(
    {
      method: 'POST',
      path: 'projects',
      json: historyId == null ? true : { projectId: historyId },
    },
    (error, project) => {
      if (error) {
        return callback(OError.tag(error))
      }

      const id = project.projectId
      if (id == null) {
        error = new OError('history store did not return a project id', id)
        return callback(error)
      }

      callback(null, id)
    }
  )
}

export function deleteProject(projectId, callback) {
  _requestHistoryService(
    { method: 'DELETE', path: `projects/${projectId}` },
    callback
  )
}

const getProjectBlobAsync = BPromise.promisify(getProjectBlob)

class BlobStore {
  constructor(projectId) {
    this.projectId = projectId
  }

  getString(hash) {
    return getProjectBlobAsync(this.projectId, hash)
  }
}

export function getBlobStore(projectId) {
  return new BlobStore(projectId)
}

function _requestOptions(options) {
  const requestOptions = {
    method: options.method || 'GET',
    url: `${Settings.overleaf.history.host}/${options.path}`,
    timeout: HTTP_REQUEST_TIMEOUT,
    auth: {
      user: Settings.overleaf.history.user,
      pass: Settings.overleaf.history.pass,
      sendImmediately: true,
    },
  }

  if (options.json != null) {
    requestOptions.json = options.json
  }

  if (options.body != null) {
    requestOptions.body = options.body
  }

  if (options.qs != null) {
    requestOptions.qs = options.qs
  }

  return requestOptions
}

function _requestHistoryService(options, callback) {
  const requestOptions = _requestOptions(options)
  request(requestOptions, (error, res, body) => {
    if (error) {
      return callback(OError.tag(error))
    }

    if (res.statusCode >= 200 && res.statusCode < 300) {
      callback(null, body)
    } else {
      error = new OError(
        `history store a non-success status code: ${res.statusCode}`
      )
      error.statusCode = res.statusCode
      error.body = body
      logger.warn({ err: error }, error.message)
      callback(error)
    }
  })
}

function _requestHistoryServiceStream(options, callback) {
  callback = _.once(callback)
  const requestOptions = _requestOptions(options)
  const stream = request(requestOptions)
  stream.on('error', callback)
  stream.on('response', res => {
    if (res.statusCode >= 200 && res.statusCode < 300) {
      callback(null, stream)
    } else {
      const error = new OError(
        `history store a non-success status code: ${res.statusCode}`
      )
      logger.warn({ err: error, options }, error.message)
      callback(error)
    }
  })
}