'use strict'
// external modules
var fs = require('fs')
var path = require('path')
var LZString = require('lz-string')
var base64url = require('base64url')
var md = require('markdown-it')()
var metaMarked = require('meta-marked')
var cheerio = require('cheerio')
var shortId = require('shortid')
var Sequelize = require('sequelize')
var async = require('async')
var moment = require('moment')
var DiffMatchPatch = require('diff-match-patch')
var dmp = new DiffMatchPatch()
var S = require('string')

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

// ot
var ot = require('../ot')

// permission types
var permissionTypes = ['freely', 'editable', 'limited', 'locked', 'protected', 'private']

module.exports = function (sequelize, DataTypes) {
  var Note = sequelize.define('Note', {
    id: {
      type: DataTypes.UUID,
      primaryKey: true,
      defaultValue: Sequelize.UUIDV4
    },
    shortid: {
      type: DataTypes.STRING,
      unique: true,
      allowNull: false,
      defaultValue: shortId.generate
    },
    alias: {
      type: DataTypes.STRING,
      unique: true
    },
    permission: {
      type: DataTypes.ENUM,
      values: permissionTypes
    },
    viewcount: {
      type: DataTypes.INTEGER,
      allowNull: false,
      defaultValue: 0
    },
    title: {
      type: DataTypes.TEXT,
      get: function () {
        return sequelize.processData(this.getDataValue('title'), '')
      },
      set: function (value) {
        this.setDataValue('title', 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))
      }
    },
    authorship: {
      type: DataTypes.TEXT('long'),
      get: function () {
        return sequelize.processData(this.getDataValue('authorship'), [], JSON.parse)
      },
      set: function (value) {
        this.setDataValue('authorship', JSON.stringify(value))
      }
    },
    lastchangeAt: {
      type: DataTypes.DATE
    },
    savedAt: {
      type: DataTypes.DATE
    }
  }, {
    paranoid: true,
    classMethods: {
      associate: function (models) {
        Note.belongsTo(models.User, {
          foreignKey: 'ownerId',
          as: 'owner',
          constraints: false
        })
        Note.belongsTo(models.User, {
          foreignKey: 'lastchangeuserId',
          as: 'lastchangeuser',
          constraints: false
        })
        Note.hasMany(models.Revision, {
          foreignKey: 'noteId',
          constraints: false
        })
        Note.hasMany(models.Author, {
          foreignKey: 'noteId',
          as: 'authors',
          constraints: false
        })
      },
      checkFileExist: function (filePath) {
        try {
          return fs.statSync(filePath).isFile()
        } catch (err) {
          return false
        }
      },
      encodeNoteId: function (id) {
        // remove dashes in UUID and encode in url-safe base64
        let str = id.replace(/-/g, '')
        let hexStr = Buffer.from(str, 'hex')
        return base64url.encode(hexStr)
      },
      decodeNoteId: function (encodedId) {
        // decode from url-safe base64
        let id = base64url.toBuffer(encodedId).toString('hex')
        // add dashes between the UUID string parts
        let idParts = []
        idParts.push(id.substr(0, 8))
        idParts.push(id.substr(8, 4))
        idParts.push(id.substr(12, 4))
        idParts.push(id.substr(16, 4))
        idParts.push(id.substr(20, 12))
        return idParts.join('-')
      },
      checkNoteIdValid: function (id) {
        var uuidRegex = /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i
        var result = id.match(uuidRegex)
        if (result && result.length === 1) { return true } else { return false }
      },
      parseNoteId: function (noteId, callback) {
        async.series({
          parseNoteIdByAlias: function (_callback) {
            // try to parse note id by alias (e.g. doc)
            Note.findOne({
              where: {
                alias: noteId
              }
            }).then(function (note) {
              if (note) {
                let filePath = path.join(config.docsPath, noteId + '.md')
                if (Note.checkFileExist(filePath)) {
                  // if doc in filesystem have newer modified time than last change time
                  // then will update the doc in db
                  var fsModifiedTime = moment(fs.statSync(filePath).mtime)
                  var dbModifiedTime = moment(note.lastchangeAt || note.createdAt)
                  var body = fs.readFileSync(filePath, 'utf8')
                  var contentLength = body.length
                  var title = Note.parseNoteTitle(body)
                  if (fsModifiedTime.isAfter(dbModifiedTime) && note.content !== body) {
                    note.update({
                      title: title,
                      content: body,
                      lastchangeAt: fsModifiedTime
                    }).then(function (note) {
                      sequelize.models.Revision.saveNoteRevision(note, function (err, revision) {
                        if (err) return _callback(err, null)
                        // update authorship on after making revision of docs
                        var patch = dmp.patch_fromText(revision.patch)
                        var operations = Note.transformPatchToOperations(patch, contentLength)
                        var authorship = note.authorship
                        for (let i = 0; i < operations.length; i++) {
                          authorship = Note.updateAuthorshipByOperation(operations[i], null, authorship)
                        }
                        note.update({
                          authorship: authorship
                        }).then(function (note) {
                          return callback(null, note.id)
                        }).catch(function (err) {
                          return _callback(err, null)
                        })
                      })
                    }).catch(function (err) {
                      return _callback(err, null)
                    })
                  } else {
                    return callback(null, note.id)
                  }
                } else {
                  return callback(null, note.id)
                }
              } else {
                var filePath = path.join(config.docsPath, noteId + '.md')
                if (Note.checkFileExist(filePath)) {
                  Note.create({
                    alias: noteId,
                    owner: null,
                    permission: 'locked'
                  }).then(function (note) {
                    return callback(null, note.id)
                  }).catch(function (err) {
                    return _callback(err, null)
                  })
                } else {
                  return _callback(null, null)
                }
              }
            }).catch(function (err) {
              return _callback(err, null)
            })
          },
          // parse note id by LZString is deprecated, here for compability
          parseNoteIdByLZString: function (_callback) {
            // try to parse note id by LZString Base64
            try {
              var id = LZString.decompressFromBase64(noteId)
              if (id && Note.checkNoteIdValid(id)) { return callback(null, id) } else { return _callback(null, null) }
            } catch (err) {
              logger.error(err)
              return _callback(null, null)
            }
          },
          parseNoteIdByBase64Url: function (_callback) {
            // try to parse note id by base64url
            try {
              var id = Note.decodeNoteId(noteId)
              if (id && Note.checkNoteIdValid(id)) { return callback(null, id) } else { return _callback(null, null) }
            } catch (err) {
              logger.error(err)
              return _callback(null, null)
            }
          },
          parseNoteIdByShortId: function (_callback) {
            // try to parse note id by shortId
            try {
              if (shortId.isValid(noteId)) {
                Note.findOne({
                  where: {
                    shortid: noteId
                  }
                }).then(function (note) {
                  if (!note) return _callback(null, null)
                  return callback(null, note.id)
                }).catch(function (err) {
                  return _callback(err, null)
                })
              } else {
                return _callback(null, null)
              }
            } catch (err) {
              return _callback(err, null)
            }
          }
        }, function (err, result) {
          if (err) {
            logger.error(err)
            return callback(err, null)
          }
          return callback(null, null)
        })
      },
      parseNoteInfo: function (body) {
        var parsed = Note.extractMeta(body)
        var $ = cheerio.load(md.render(parsed.markdown))
        return {
          title: Note.extractNoteTitle(parsed.meta, $),
          tags: Note.extractNoteTags(parsed.meta, $)
        }
      },
      parseNoteTitle: function (body) {
        var parsed = Note.extractMeta(body)
        var $ = cheerio.load(md.render(parsed.markdown))
        return Note.extractNoteTitle(parsed.meta, $)
      },
      extractNoteTitle: function (meta, $) {
        var title = ''
        if (meta.title && (typeof meta.title === 'string' || typeof meta.title === 'number')) {
          title = meta.title
        } else {
          var h1s = $('h1')
          if (h1s.length > 0 && h1s.first().text().split('\n').length === 1) { title = S(h1s.first().text()).stripTags().s }
        }
        if (!title) title = 'Untitled'
        return title
      },
      generateDescription: function (markdown) {
        return markdown.substr(0, 100).replace(/(?:\r\n|\r|\n)/g, ' ')
      },
      decodeTitle: function (title) {
        return title || 'Untitled'
      },
      generateWebTitle: function (title) {
        title = !title || title === 'Untitled' ? 'HackMD - Collaborative markdown notes' : title + ' - HackMD'
        return title
      },
      extractNoteTags: function (meta, $) {
        var tags = []
        var rawtags = []
        if (meta.tags && (typeof meta.tags === 'string' || typeof meta.tags === 'number')) {
          var metaTags = ('' + meta.tags).split(',')
          for (let i = 0; i < metaTags.length; i++) {
            var text = metaTags[i].trim()
            if (text) rawtags.push(text)
          }
        } else {
          var h6s = $('h6')
          h6s.each(function (key, value) {
            if (/^tags/gmi.test($(value).text())) {
              var codes = $(value).find('code')
              for (let i = 0; i < codes.length; i++) {
                var text = S($(codes[i]).text().trim()).stripTags().s
                if (text) rawtags.push(text)
              }
            }
          })
        }
        for (let i = 0; i < rawtags.length; i++) {
          var found = false
          for (let j = 0; j < tags.length; j++) {
            if (tags[j] === rawtags[i]) {
              found = true
              break
            }
          }
          if (!found) { tags.push(rawtags[i]) }
        }
        return tags
      },
      extractMeta: function (content) {
        var obj = null
        try {
          obj = metaMarked(content)
          if (!obj.markdown) obj.markdown = ''
          if (!obj.meta) obj.meta = {}
        } catch (err) {
          obj = {
            markdown: content,
            meta: {}
          }
        }
        return obj
      },
      parseMeta: function (meta) {
        var _meta = {}
        if (meta) {
          if (meta.title && (typeof meta.title === 'string' || typeof meta.title === 'number')) { _meta.title = meta.title }
          if (meta.description && (typeof meta.description === 'string' || typeof meta.description === 'number')) { _meta.description = meta.description }
          if (meta.robots && (typeof meta.robots === 'string' || typeof meta.robots === 'number')) { _meta.robots = meta.robots }
          if (meta.GA && (typeof meta.GA === 'string' || typeof meta.GA === 'number')) { _meta.GA = meta.GA }
          if (meta.disqus && (typeof meta.disqus === 'string' || typeof meta.disqus === 'number')) { _meta.disqus = meta.disqus }
          if (meta.slideOptions && (typeof meta.slideOptions === 'object')) { _meta.slideOptions = meta.slideOptions }
        }
        return _meta
      },
      updateAuthorshipByOperation: function (operation, userId, authorships) {
        var index = 0
        var timestamp = Date.now()
        for (let i = 0; i < operation.length; i++) {
          var op = operation[i]
          if (ot.TextOperation.isRetain(op)) {
            index += op
          } else if (ot.TextOperation.isInsert(op)) {
            let opStart = index
            let opEnd = index + op.length
            var inserted = false
            // authorship format: [userId, startPos, endPos, createdAt, updatedAt]
            if (authorships.length <= 0) authorships.push([userId, opStart, opEnd, timestamp, timestamp])
            else {
              for (let j = 0; j < authorships.length; j++) {
                let authorship = authorships[j]
                if (!inserted) {
                  let nextAuthorship = authorships[j + 1] || -1
                  if ((nextAuthorship !== -1 && nextAuthorship[1] >= opEnd) || j >= authorships.length - 1) {
                    if (authorship[1] < opStart && authorship[2] > opStart) {
                      // divide
                      let postLength = authorship[2] - opStart
                      authorship[2] = opStart
                      authorship[4] = timestamp
                      authorships.splice(j + 1, 0, [userId, opStart, opEnd, timestamp, timestamp])
                      authorships.splice(j + 2, 0, [authorship[0], opEnd, opEnd + postLength, authorship[3], timestamp])
                      j += 2
                      inserted = true
                    } else if (authorship[1] >= opStart) {
                      authorships.splice(j, 0, [userId, opStart, opEnd, timestamp, timestamp])
                      j += 1
                      inserted = true
                    } else if (authorship[2] <= opStart) {
                      authorships.splice(j + 1, 0, [userId, opStart, opEnd, timestamp, timestamp])
                      j += 1
                      inserted = true
                    }
                  }
                }
                if (authorship[1] >= opStart) {
                  authorship[1] += op.length
                  authorship[2] += op.length
                }
              }
            }
            index += op.length
          } else if (ot.TextOperation.isDelete(op)) {
            let opStart = index
            let opEnd = index - op
            if (operation.length === 1) {
              authorships = []
            } else if (authorships.length > 0) {
              for (let j = 0; j < authorships.length; j++) {
                let authorship = authorships[j]
                if (authorship[1] >= opStart && authorship[1] <= opEnd && authorship[2] >= opStart && authorship[2] <= opEnd) {
                  authorships.splice(j, 1)
                  j -= 1
                } else if (authorship[1] < opStart && authorship[1] < opEnd && authorship[2] > opStart && authorship[2] > opEnd) {
                  authorship[2] += op
                  authorship[4] = timestamp
                } else if (authorship[2] >= opStart && authorship[2] <= opEnd) {
                  authorship[2] = opStart
                  authorship[4] = timestamp
                } else if (authorship[1] >= opStart && authorship[1] <= opEnd) {
                  authorship[1] = opEnd
                  authorship[4] = timestamp
                }
                if (authorship[1] >= opEnd) {
                  authorship[1] += op
                  authorship[2] += op
                }
              }
            }
            index += op
          }
        }
        // merge
        for (let j = 0; j < authorships.length; j++) {
          let authorship = authorships[j]
          for (let k = j + 1; k < authorships.length; k++) {
            let nextAuthorship = authorships[k]
            if (nextAuthorship && authorship[0] === nextAuthorship[0] && authorship[2] === nextAuthorship[1]) {
              let minTimestamp = Math.min(authorship[3], nextAuthorship[3])
              let maxTimestamp = Math.max(authorship[3], nextAuthorship[3])
              authorships.splice(j, 1, [authorship[0], authorship[1], nextAuthorship[2], minTimestamp, maxTimestamp])
              authorships.splice(k, 1)
              j -= 1
              break
            }
          }
        }
        // clear
        for (let j = 0; j < authorships.length; j++) {
          let authorship = authorships[j]
          if (!authorship[0]) {
            authorships.splice(j, 1)
            j -= 1
          }
        }
        return authorships
      },
      transformPatchToOperations: function (patch, contentLength) {
        var operations = []
        if (patch.length > 0) {
          // calculate original content length
          for (let j = patch.length - 1; j >= 0; j--) {
            var p = patch[j]
            for (let i = 0; i < p.diffs.length; i++) {
              var diff = p.diffs[i]
              switch (diff[0]) {
                case 1: // insert
                  contentLength -= diff[1].length
                  break
                case -1: // delete
                  contentLength += diff[1].length
                  break
              }
            }
          }
          // generate operations
          var bias = 0
          var lengthBias = 0
          for (let j = 0; j < patch.length; j++) {
            var operation = []
            let p = patch[j]
            var currIndex = p.start1
            var currLength = contentLength - bias
            for (let i = 0; i < p.diffs.length; i++) {
              let diff = p.diffs[i]
              switch (diff[0]) {
                case 0: // retain
                  if (i === 0) {
                    // first
                    operation.push(currIndex + diff[1].length)
                  } else if (i !== p.diffs.length - 1) {
                    // mid
                    operation.push(diff[1].length)
                  } else {
                    // last
                    operation.push(currLength + lengthBias - currIndex)
                  }
                  currIndex += diff[1].length
                  break
                case 1: // insert
                  operation.push(diff[1])
                  lengthBias += diff[1].length
                  currIndex += diff[1].length
                  break
                case -1: // delete
                  operation.push(-diff[1].length)
                  bias += diff[1].length
                  currIndex += diff[1].length
                  break
              }
            }
            operations.push(operation)
          }
        }
        return operations
      }
    },
    hooks: {
      beforeCreate: function (note, options, callback) {
        // if no content specified then use default note
        if (!note.content) {
          var body = null
          let filePath = null
          if (!note.alias) {
            filePath = config.defaultNotePath
          } else {
            filePath = path.join(config.docsPath, note.alias + '.md')
          }
          if (Note.checkFileExist(filePath)) {
            var fsCreatedTime = moment(fs.statSync(filePath).ctime)
            body = fs.readFileSync(filePath, 'utf8')
            note.title = Note.parseNoteTitle(body)
            note.content = body
            if (filePath !== config.defaultNotePath) {
              note.createdAt = fsCreatedTime
            }
          }
        }
        // if no permission specified and have owner then give default permission in config, else default permission is freely
        if (!note.permission) {
          if (note.ownerId) {
            note.permission = config.defaultPermission
          } else {
            note.permission = 'freely'
          }
        }
        return callback(null, note)
      },
      afterCreate: function (note, options, callback) {
        sequelize.models.Revision.saveNoteRevision(note, function (err, revision) {
          callback(err, note)
        })
      }
    }
  })

  return Note
}
