import { tmpdir }  from 'os'
import * as path from 'path'
import * as Promise from 'bluebird'
import * as winston from 'winston'
import { CoError } from '../../../modules/co-error'
import PresentationSettings from '../../../modules/presentation-settings'
import { PresentationClient } from '../../../services/presentation'
import clonePresentation from '../src/clonePresentation'
import { copy, remove } from '../src/fs'
import PresentationFileDiff from '../src/PresentationFileDiff'
import PresentationChecksums from '../src/PresentationChecksums'

export function pull (presentationChecksums: PresentationChecksums,
                      presentationClient: PresentationClient, presentationDir: string, force: boolean = false): Promise<void> {

  const update = updatePresentation.bind(null, presentationChecksums, presentationClient, presentationDir);

  if (force) {
    return update()
  }
  return checkFilesDiff(presentationChecksums, presentationDir)
    .then(update)
}

function updatePresentation(presentationChecksums: PresentationChecksums, presentationClient: PresentationClient, presentationDir: string) {
  const appDir = path.join(presentationDir, 'app');
  const backupDir = getTempBackupDir();

  return createBackup(appDir, backupDir)
    .then(() => pullPresentation(presentationClient, presentationDir, appDir, backupDir))
    .then(createChecksums(presentationChecksums, presentationDir))
    .finally(removeBackup(backupDir))
}

function checkFilesDiff(presentationChecksums: PresentationChecksums, presentationDir: string): Promise<void> {
  return presentationChecksums.findDiff(presentationDir)
    .then((diff: PresentationFileDiff) => {
      const { added, updated, removed } = diff;
      const diffs: string[] = [...added, ...updated, ...removed];

      if (diffs.length) {
        return Promise.reject(new CoError('PRESENTATION_HAS_LOCAL_CHANGES'))
      }
      return Promise.resolve()
    });
}

function pullPresentation(presentationClient: PresentationClient, presentationDir: string, appDir: string, backupDir: string): Promise<void> {
    return getPresentationId(presentationDir)
      .then(removeLocalPresentation(appDir))
      .then(downloadPresentation(presentationClient, presentationDir))
      .catch(rollBackChanges(backupDir, appDir))
}

function createBackup(srcDir: string, backupDir: string): Promise<void> {
  return copy(srcDir, backupDir);
}

function getTempBackupDir() {
  return path.join(tmpdir(), 'backup' + Date.now())
}

function getPresentationId(presentationDir: string): Promise<string | undefined> {
    const presentationSettings = new PresentationSettings(presentationDir)

    return presentationSettings.get('id')
}

function downloadPresentation(presentationClient: PresentationClient, presentationDir: string): (id: string) => Promise<void> {
  return function (presentationId) {
    return clonePresentation(presentationClient, presentationDir, presentationId)
  }
}

function createChecksums(presentationChecksums: PresentationChecksums, presentationDir: string): () => Promise<void> {
  return function () {
    return presentationChecksums.createChecksums(presentationDir);
  }
}

function removeLocalPresentation(dir: string): (id: string) => Promise<string> {
  return function (presentationId) {
    return remove(dir)
      .then(() => presentationId)
  }
}

function rollBackChanges(backupDir: string, srcDir: string): (err: Error) => Promise<void> {
  return function (err) {
    return rollBack(backupDir, srcDir)
      .finally(() => {
        throw err
      })
  }
}

function rollBack (backupDir: string, destDir: string) {
  return Promise.resolve(remove(destDir))
    .finally(() => copy(backupDir, destDir))
}

function removeBackup(backupDir: string): () => Promise<void> {
  return function () {
    return remove(backupDir)
  }
}