'use strict'
// external modules
var Sequelize = require('sequelize')
var async = require('async')
var moment = require('moment')
var childProcess = require('child_process')
var shortId = require('shortid')

// core
var config = require('../config')
var logger = require('../logger')

var dmpWorker = createDmpWorker()
var dmpCallbackCache = {}

function createDmpWorker () {
  var worker = childProcess.fork('./lib/workers/dmpWorker.js', {
    stdio: 'ignore'
  })
  if (config.debug) logger.info('dmp worker process started')
  worker.on('message', function (data) {
    if (!data || !data.msg || !data.cacheKey) {
      return logger.error('dmp worker error: not enough data on message')
    }
    var cacheKey = data.cacheKey
    switch (data.msg) {
      case 'error':
        dmpCallbackCache[cacheKey](data.error, null)
        break
      case 'check':
        dmpCallbackCache[cacheKey](null, data.result)
        break
    }
    delete dmpCallbackCache[cacheKey]
  })
  worker.on('close', function (code) {
    dmpWorker = null
    if (config.debug) logger.info('dmp worker process exited with code ' + code)
  })
  return worker
}

function sendDmpWorker (data, callback) {
  if (!dmpWorker) dmpWorker = createDmpWorker()
  var cacheKey = Date.now() + '_' + shortId.generate()
  dmpCallbackCache[cacheKey] = callback
  data = Object.assign(data, {
    cacheKey: cacheKey
  })
  dmpWorker.send(data)
}

module.exports = function (sequelize, DataTypes) {
  var Revision = sequelize.define('Revision', {
    id: {
      type: DataTypes.UUID,
      primaryKey: true,
      defaultValue: Sequelize.UUIDV4
    },
    patch: {
      type: DataTypes.TEXT('long'),
      get: function () {
        return sequelize.processData(this.getDataValue('patch'), '')
      },
      set: function (value) {
        this.setDataValue('patch', sequelize.stripNullByte(value))
      }
    },
    lastContent: {
      type: DataTypes.TEXT('long'),
      get: function () {
        return sequelize.processData(this.getDataValue('lastContent'), '')
      },
      set: function (value) {
        this.setDataValue('lastContent', sequelize.stripNullByte(value))
      }
    },
    content: {
      type: DataTypes.TEXT('long'),
      get: function () {
        return sequelize.processData(this.getDataValue('content'), '')
      },
      set: function (value) {
        this.setDataValue('content', sequelize.stripNullByte(value))
      }
    },
    length: {
      type: DataTypes.INTEGER
    },
    authorship: {
      type: DataTypes.TEXT('long'),
      get: function () {
        return sequelize.processData(this.getDataValue('authorship'), [], JSON.parse)
      },
      set: function (value) {
        this.setDataValue('authorship', value ? JSON.stringify(value) : value)
      }
    }
  }, {
    classMethods: {
      associate: function (models) {
        Revision.belongsTo(models.Note, {
          foreignKey: 'noteId',
          as: 'note',
          constraints: false,
          onDelete: 'CASCADE',
          hooks: true
        })
      },
      getNoteRevisions: function (note, callback) {
        Revision.findAll({
          where: {
            noteId: note.id
          },
          order: [['createdAt', 'DESC']]
        }).then(function (revisions) {
          var data = []
          for (var i = 0, l = revisions.length; i < l; i++) {
            var revision = revisions[i]
            data.push({
              time: moment(revision.createdAt).valueOf(),
              length: revision.length
            })
          }
          callback(null, data)
        }).catch(function (err) {
          callback(err, null)
        })
      },
      getPatchedNoteRevisionByTime: function (note, time, callback) {
        // find all revisions to prepare for all possible calculation
        Revision.findAll({
          where: {
            noteId: note.id
          },
          order: [['createdAt', 'DESC']]
        }).then(function (revisions) {
          if (revisions.length <= 0) return callback(null, null)
          // measure target revision position
          Revision.count({
            where: {
              noteId: note.id,
              createdAt: {
                $gte: time
              }
            },
            order: [['createdAt', 'DESC']]
          }).then(function (count) {
            if (count <= 0) return callback(null, null)
            sendDmpWorker({
              msg: 'get revision',
              revisions: revisions,
              count: count
            }, callback)
          }).catch(function (err) {
            return callback(err, null)
          })
        }).catch(function (err) {
          return callback(err, null)
        })
      },
      checkAllNotesRevision: function (callback) {
        Revision.saveAllNotesRevision(function (err, notes) {
          if (err) return callback(err, null)
          if (!notes || notes.length <= 0) {
            return callback(null, notes)
          } else {
            Revision.checkAllNotesRevision(callback)
          }
        })
      },
      saveAllNotesRevision: function (callback) {
        sequelize.models.Note.findAll({
          // query all notes that need to save for revision
          where: {
            $and: [
              {
                lastchangeAt: {
                  $or: {
                    $eq: null,
                    $and: {
                      $ne: null,
                      $gt: sequelize.col('createdAt')
                    }
                  }
                }
              },
              {
                savedAt: {
                  $or: {
                    $eq: null,
                    $lt: sequelize.col('lastchangeAt')
                  }
                }
              }
            ]
          }
        }).then(function (notes) {
          if (notes.length <= 0) return callback(null, notes)
          var savedNotes = []
          async.each(notes, function (note, _callback) {
            // revision saving policy: note not been modified for 5 mins or not save for 10 mins
            if (note.lastchangeAt && note.savedAt) {
              var lastchangeAt = moment(note.lastchangeAt)
              var savedAt = moment(note.savedAt)
              if (moment().isAfter(lastchangeAt.add(5, 'minutes'))) {
                savedNotes.push(note)
                Revision.saveNoteRevision(note, _callback)
              } else if (lastchangeAt.isAfter(savedAt.add(10, 'minutes'))) {
                savedNotes.push(note)
                Revision.saveNoteRevision(note, _callback)
              } else {
                return _callback(null, null)
              }
            } else {
              savedNotes.push(note)
              Revision.saveNoteRevision(note, _callback)
            }
          }, function (err) {
            if (err) {
              return callback(err, null)
            }
            // return null when no notes need saving at this moment but have delayed tasks to be done
            var result = ((savedNotes.length === 0) && (notes.length > savedNotes.length)) ? null : savedNotes
            return callback(null, result)
          })
        }).catch(function (err) {
          return callback(err, null)
        })
      },
      saveNoteRevision: function (note, callback) {
        Revision.findAll({
          where: {
            noteId: note.id
          },
          order: [['createdAt', 'DESC']]
        }).then(function (revisions) {
          if (revisions.length <= 0) {
            // if no revision available
            Revision.create({
              noteId: note.id,
              lastContent: note.content ? note.content : '',
              length: note.content ? note.content.length : 0,
              authorship: note.authorship
            }).then(function (revision) {
              Revision.finishSaveNoteRevision(note, revision, callback)
            }).catch(function (err) {
              return callback(err, null)
            })
          } else {
            var latestRevision = revisions[0]
            var lastContent = latestRevision.content || latestRevision.lastContent
            var content = note.content
            sendDmpWorker({
              msg: 'create patch',
              lastDoc: lastContent,
              currDoc: content
            }, function (err, patch) {
              if (err) logger.error('save note revision error', err)
              if (!patch) {
                // if patch is empty (means no difference) then just update the latest revision updated time
                latestRevision.changed('updatedAt', true)
                latestRevision.update({
                  updatedAt: Date.now()
                }).then(function (revision) {
                  Revision.finishSaveNoteRevision(note, revision, callback)
                }).catch(function (err) {
                  return callback(err, null)
                })
              } else {
                Revision.create({
                  noteId: note.id,
                  patch: patch,
                  content: note.content,
                  length: note.content.length,
                  authorship: note.authorship
                }).then(function (revision) {
                  // clear last revision content to reduce db size
                  latestRevision.update({
                    content: null
                  }).then(function () {
                    Revision.finishSaveNoteRevision(note, revision, callback)
                  }).catch(function (err) {
                    return callback(err, null)
                  })
                }).catch(function (err) {
                  return callback(err, null)
                })
              }
            })
          }
        }).catch(function (err) {
          return callback(err, null)
        })
      },
      finishSaveNoteRevision: function (note, revision, callback) {
        note.update({
          savedAt: revision.updatedAt
        }).then(function () {
          return callback(null, revision)
        }).catch(function (err) {
          return callback(err, null)
        })
      }
    }
  })

  return Revision
}
