const debug = require('debug')('growi:models:page');
const nodePath = require('path');
const mongoose = require('mongoose');
const uniqueValidator = require('mongoose-unique-validator');
const ObjectId = mongoose.Schema.Types.ObjectId;

const escapeStringRegexp = require('escape-string-regexp');

const templateChecker = require('@commons/util/template-checker');

/*
 * define schema
 */
const GRANT_PUBLIC = 1
  , GRANT_RESTRICTED = 2
  , GRANT_SPECIFIED = 3
  , GRANT_OWNER = 4
  , GRANT_USER_GROUP = 5
  , PAGE_GRANT_ERROR = 1

  , STATUS_PUBLISHED  = 'published'
  , STATUS_DELETED    = 'deleted'
;
const pageSchema = new mongoose.Schema({
  path: { type: String, required: true, index: true, unique: true },
  revision: { type: ObjectId, ref: 'Revision' },
  redirectTo: { type: String, index: true },
  status: { type: String, default: STATUS_PUBLISHED, index: true },
  grant: { type: Number, default: GRANT_PUBLIC, index: true },
  grantedUsers: [{ type: ObjectId, ref: 'User' }],
  grantedGroup: { type: ObjectId, ref: 'UserGroup', index: true },
  creator: { type: ObjectId, ref: 'User', index: true },
  lastUpdateUser: { type: ObjectId, ref: 'User', index: true },
  liker: [{ type: ObjectId, ref: 'User', index: true }],
  seenUsers: [{ type: ObjectId, ref: 'User', index: true }],
  commentCount: { type: Number, default: 0 },
  extended: {
    type: String,
    default: '{}',
    get: function(data) {
      try {
        return JSON.parse(data);
      }
      catch (e) {
        return data;
      }
    },
    set: function(data) {
      return JSON.stringify(data);
    }
  },
  pageIdOnHackmd: String,
  revisionHackmdSynced: { type: ObjectId, ref: 'Revision' },  // the revision that is synced to HackMD
  hasDraftOnHackmd: { type: Boolean },                        // set true if revision and revisionHackmdSynced are same but HackMD document has modified
  createdAt: { type: Date, default: Date.now },
  updatedAt: Date
}, {
  toJSON: {getters: true},
  toObject: {getters: true}
});
// apply plugins
pageSchema.plugin(uniqueValidator);



const addSlashOfEnd = (path) => {
  let returnPath = path;
  if (!path.match(/\/$/)) {
    returnPath += '/';
  }
  return returnPath;
};

/**
 * populate page (Query or Document) to show revision
 * @param {any} page Query or Document
 * @param {string} userPublicFields string to set to select
 */
const populateDataToShowRevision = (page, userPublicFields) => {
  return page
    .populate({ path: 'lastUpdateUser', model: 'User', select: userPublicFields })
    .populate({ path: 'creator', model: 'User', select: userPublicFields })
    .populate({ path: 'grantedGroup', model: 'UserGroup' })
    .populate({ path: 'revision', model: 'Revision', populate: {
      path: 'author', model: 'User', select: userPublicFields
    } });
};


class PageQueryBuilder {
  constructor(query) {
    this.query = query;
  }

  addConditionToExcludeTrashed() {
    this.query = this.query
      .and({
        $or: [
          {status: null},
          {status: STATUS_PUBLISHED},
        ]
      });

    return this;
  }

  addConditionToExcludeRedirect() {
    this.query = this.query.and({ redirectTo: null });
    return this;
  }

  /**
   * generate the query to find the page that is match with `path` and its descendants
   */
  addConditionToListWithDescendants(path, option) {
    // ignore other pages than descendants
    path = addSlashOfEnd(path);

    // add option to escape the regex strings
    const combinedOption = Object.assign({isRegExpEscapedFromPath: true}, option);

    this.addConditionToListByStartWith(path, combinedOption);

    return this;
  }

  /**
   * generate the query to find pages that start with `path`
   *
   * (GROWI) If 'isRegExpEscapedFromPath' is true, `path` should have `/` at the end
   *   -> returns '{path}/*' and '{path}' self.
   * (Crowi) If 'isRegExpEscapedFromPath' is false and `path` has `/` at the end
   *   -> returns '{path}*'
   * (Crowi) If 'isRegExpEscapedFromPath' is false and `path` doesn't have `/` at the end
   *   -> returns '{path}*'
   *
   * *option*
   *   - isRegExpEscapedFromPath -- if true, the regex strings included in `path` is escaped (default: false)
   */
  addConditionToListByStartWith(path, option) {
    const pathCondition = [];
    const isRegExpEscapedFromPath = option.isRegExpEscapedFromPath || false;

    /*
     * 1. add condition for finding the page completely match with `path` w/o last slash
     */
    let pathSlashOmitted = path;
    if (path.match(/\/$/)) {
      pathSlashOmitted = path.substr(0, path.length -1);
      pathCondition.push({path: pathSlashOmitted});
    }

    /*
     * 2. add decendants
     */
    const pattern = (isRegExpEscapedFromPath)
      ? escapeStringRegexp(path)  // escape
      : pathSlashOmitted;

    const queryReg = new RegExp('^' + pattern);
    pathCondition.push({path: queryReg});

    this.query = this.query
      .and({
        $or: pathCondition
      });

    return this;
  }

  addConditionToFilteringByViewer(user, userGroups) {
    const grantConditions = [
      {grant: null},
      {grant: GRANT_PUBLIC},
    ];

    if (user == null) {
      grantConditions.push(
        {grant: GRANT_RESTRICTED},
        {grant: GRANT_SPECIFIED},
        {grant: GRANT_OWNER},
      );
    }
    else {
      grantConditions.push(
        {grant: GRANT_RESTRICTED, grantedUsers: user._id},
        {grant: GRANT_SPECIFIED, grantedUsers: user._id},
        {grant: GRANT_OWNER, grantedUsers: user._id},
      );
    }

    if (userGroups == null) {
      grantConditions.push(
        {grant: GRANT_USER_GROUP},
      );
    }
    else {
      grantConditions.push(
        {grant: GRANT_USER_GROUP, grantedGroup: { $in: userGroups }},
      );
    }

    this.query = this.query
      .and({
        $or: grantConditions
      });

    return this;
  }

  addConditionToPagenate(offset, limit, sortOpt) {
    this.query = this.query
      .sort(sortOpt).skip(offset).limit(limit);

    return this;
  }

  populateDataToShowRevision(userPublicFields) {
    this.query = populateDataToShowRevision(this.query, userPublicFields);
    return this;
  }

}

module.exports = function(crowi) {
  let pageEvent;

  // init event
  if (crowi != null) {
    pageEvent = crowi.event('page');
    pageEvent.on('create', pageEvent.onCreate);
    pageEvent.on('update', pageEvent.onUpdate);
  }

  function isPortalPath(path) {
    if (path.match(/.*\/$/)) {
      return true;
    }

    return false;
  }

  function validateCrowi() {
    if (crowi == null) {
      throw new Error('"crowi" is null. Init User model with "crowi" argument first.');
    }
  }

  pageSchema.methods.isDeleted = function() {
    return (this.status === STATUS_DELETED) || checkIfTrashed(this.path);
  };

  pageSchema.methods.isPublic = function() {
    if (!this.grant || this.grant == GRANT_PUBLIC) {
      return true;
    }

    return false;
  };

  pageSchema.methods.isPortal = function() {
    return isPortalPath(this.path);
  };

  pageSchema.methods.isTemplate = function() {
    return templateChecker(this.path);
  };

  pageSchema.methods.isLatestRevision = function() {
    // populate されていなくて判断できない
    if (!this.latestRevision || !this.revision) {
      return true;
    }

    return (this.latestRevision == this.revision._id.toString());
  };

  pageSchema.methods.isUpdatable = function(previousRevision) {
    var revision = this.latestRevision || this.revision;
    if (revision != previousRevision) {
      return false;
    }
    return true;
  };

  pageSchema.methods.isLiked = function(userData) {
    return this.liker.some(function(likedUser) {
      return likedUser == userData._id.toString();
    });
  };

  pageSchema.methods.like = function(userData) {
    var self = this,
      Page = self;

    return new Promise(function(resolve, reject) {
      var added = self.liker.addToSet(userData._id);
      if (added.length > 0) {
        self.save(function(err, data) {
          if (err) {
            return reject(err);
          }
          debug('liker updated!', added);
          return resolve(data);
        });
      }
      else {
        debug('liker not updated');
        return reject(self);
      }
    });

  };

  pageSchema.methods.unlike = function(userData, callback) {
    var self = this,
      Page = self;

    return new Promise(function(resolve, reject) {
      var beforeCount = self.liker.length;
      self.liker.pull(userData._id);
      if (self.liker.length != beforeCount) {
        self.save(function(err, data) {
          if (err) {
            return reject(err);
          }
          return resolve(data);
        });
      }
      else {
        debug('liker not updated');
        return reject(self);
      }
    });

  };

  pageSchema.methods.isSeenUser = function(userData) {
    return this.seenUsers.includes(userData._id);
  };

  pageSchema.methods.seen = async function(userData) {
    if (this.isSeenUser(userData)) {
      debug('seenUsers not updated');
      return this;
    }

    if (!userData || !userData._id) {
      throw new Error('User data is not valid');
    }

    const added = this.seenUsers.addToSet(userData);
    const saved = await this.save();

    debug('seenUsers updated!', added);

    return saved;
  };

  pageSchema.methods.getSlackChannel = function() {
    const extended = this.get('extended');
    if (!extended) {
      return '';
    }

    return extended.slack || '';
  };

  pageSchema.methods.updateSlackChannel = function(slackChannel) {
    const extended = this.extended;
    extended.slack = slackChannel;

    return this.updateExtended(extended);
  };

  pageSchema.methods.updateExtended = function(extended) {
    const page = this;
    page.extended = extended;
    return new Promise(function(resolve, reject) {
      return page.save(function(err, doc) {
        if (err) {
          return reject(err);
        }
        return resolve(doc);
      });
    });
  };

  pageSchema.methods.initLatestRevisionField = async function(revisionId) {
    this.latestRevision = this.revision;
    if (revisionId != null) {
      this.revision = revisionId;
    }
  };

  pageSchema.methods.populateDataToShowRevision = async function() {
    validateCrowi();

    const User = crowi.model('User');
    return populateDataToShowRevision(this, User.USER_PUBLIC_FIELDS)
      .execPopulate();
  };

  pageSchema.methods.populateDataToMakePresentation = async function(revisionId) {
    this.latestRevision = this.revision;
    if (revisionId != null) {
      this.revision = revisionId;
    }
    return this.populate('revision').execPopulate();
  };


  pageSchema.statics.updateCommentCount = function(pageId) {
    validateCrowi();

    const self = this;
    const Comment = crowi.model('Comment');
    return Comment.countCommentByPageId(pageId)
    .then(function(count) {
      self.update({_id: pageId}, {commentCount: count}, {}, function(err, data) {
        if (err) {
          debug('Update commentCount Error', err);
          throw err;
        }

        return data;
      });
    });
  };

  pageSchema.statics.getGrantLabels = function() {
    var grantLabels = {};
    grantLabels[GRANT_PUBLIC]     = 'Public'; // 公開
    grantLabels[GRANT_RESTRICTED] = 'Anyone with the link'; // リンクを知っている人のみ
    //grantLabels[GRANT_SPECIFIED]  = 'Specified users only'; // 特定ユーザーのみ
    grantLabels[GRANT_USER_GROUP] = 'Only inside the group'; // 特定グループのみ
    grantLabels[GRANT_OWNER]      = 'Just me'; // 自分のみ

    return grantLabels;
  };

  pageSchema.statics.normalizePath = function(path) {
    if (!path.match(/^\//)) {
      path = '/' + path;
    }

    path = path.replace(/\/\s+?/g, '/').replace(/\s+\//g, '/');

    return path;
  };

  pageSchema.statics.getUserPagePath = function(user) {
    return '/user/' + user.username;
  };

  pageSchema.statics.getDeletedPageName = function(path) {
    if (path.match('\/')) {
      path = path.substr(1);
    }
    return '/trash/' + path;
  };

  pageSchema.statics.getRevertDeletedPageName = function(path) {
    return path.replace('\/trash', '');
  };

  pageSchema.statics.isDeletableName = function(path) {
    var notDeletable = [
      /^\/user\/[^\/]+$/, // user page
    ];

    for (var i = 0; i < notDeletable.length; i++) {
      var pattern = notDeletable[i];
      if (path.match(pattern)) {
        return false;
      }
    }

    return true;
  };

  pageSchema.statics.isCreatableName = function(name) {
    var forbiddenPages = [
      /\^|\$|\*|\+|#|%/,
      /^\/-\/.*/,
      /^\/_r\/.*/,
      /^\/_apix?(\/.*)?/,
      /^\/?https?:\/\/.+$/, // avoid miss in renaming
      /\/{2,}/,             // avoid miss in renaming
      /\s+\/\s+/,           // avoid miss in renaming
      /.+\/edit$/,
      /.+\.md$/,
      /^\/(installer|register|login|logout|admin|me|files|trash|paste|comments)(\/.*|$)/,
    ];

    var isCreatable = true;
    forbiddenPages.forEach(function(page) {
      var pageNameReg = new RegExp(page);
      if (name.match(pageNameReg)) {
        isCreatable = false;
        return ;
      }
    });

    return isCreatable;
  };

  pageSchema.statics.fixToCreatableName = function(path) {
    return path
      .replace(/\/\//g, '/')
    ;
  };

  pageSchema.statics.updateRevision = function(pageId, revisionId, cb) {
    this.update({_id: pageId}, {revision: revisionId}, {}, function(err, data) {
      cb(err, data);
    });
  };

  /**
   * return whether the user is accessible to the page
   * @param {string} id ObjectId
   * @param {User} user
   */
  pageSchema.statics.isAccessiblePageByViewer = async function(id, user) {
    const baseQuery = this.count({_id: id});

    let userGroups = [];
    if (user != null) {
      validateCrowi();
      const UserGroupRelation = crowi.model('UserGroupRelation');
      userGroups = await UserGroupRelation.findAllUserGroupIdsRelatedToUser(user);
    }

    const queryBuilder = new PageQueryBuilder(baseQuery);
    queryBuilder.addConditionToFilteringByViewer(user, userGroups);

    const count = await queryBuilder.query.exec();
    return count > 0;
  };

  /**
   * @param {string} id ObjectId
   * @param {User} user User instance
   */
  pageSchema.statics.findByIdAndViewer = async function(id, user) {
    const baseQuery = this.findOne({_id: id});

    let userGroups = [];
    if (user != null) {
      validateCrowi();
      const UserGroupRelation = crowi.model('UserGroupRelation');
      userGroups = await UserGroupRelation.findAllUserGroupIdsRelatedToUser(user);
    }

    const queryBuilder = new PageQueryBuilder(baseQuery);
    queryBuilder.addConditionToFilteringByViewer(user, userGroups);

    return await queryBuilder.query.exec();
  };

  // find page by path
  pageSchema.statics.findByPath = function(path) {
    if (path == null) {
      return null;
    }
    return this.findOne({path});
  };

  pageSchema.statics.findByPathAndViewer = async function(path, user) {
    if (path == null) {
      throw new Error('path is required.');
    }

    // const Page = this;
    const baseQuery = this.findOne({path});
    const queryBuilder = new PageQueryBuilder(baseQuery);

    if (user != null) {
      validateCrowi();
      const UserGroupRelation = crowi.model('UserGroupRelation');
      const userGroups = await UserGroupRelation.findAllUserGroupIdsRelatedToUser(user);
      queryBuilder.addConditionToFilteringByViewer(user, userGroups);
    }

    return await queryBuilder.query.exec();
  };

  pageSchema.statics.findByRedirectTo = function(path) {
    return this.findOne({redirectTo: path});
  };

  /**
   * find pages that is match with `path` and its descendants
   */
  pageSchema.statics.findListWithDescendants = async function(path, user, option) {
    const builder = new PageQueryBuilder(this.find());
    builder.addConditionToListWithDescendants(path, option);

    return await findListFromBuilderAndViewer(builder, user, option);
  };

  /**
   * find pages that start with `path`
   */
  pageSchema.statics.findListByStartWith = async function(path, user, option) {
    const builder = new PageQueryBuilder(this.find());
    builder.addConditionToListByStartWith(path, option);

    return await findListFromBuilderAndViewer(builder, user, option);
  };

  /**
   * find pages that is created by targetUser
   *
   * @param {User} targetUser
   * @param {User} currentUser
   * @param {any} option
   */
  pageSchema.statics.findListByCreator = async function(targetUser, currentUser, option) {
    const opt = Object.assign({sort: 'createdAt', desc: -1}, option);
    const builder = new PageQueryBuilder(this.find({ creator: targetUser._id }));

    return await findListFromBuilderAndViewer(builder, currentUser, opt);
  };

  pageSchema.statics.findListByPageIds = async function(ids, option) {
    const User = crowi.model('User');

    const opt = Object.assign({}, option);
    const builder = new PageQueryBuilder(this.find({ _id: { $in: ids } }));

    builder.addConditionToExcludeRedirect();
    builder.addConditionToPagenate(opt.offset, opt.limit);

    const totalCount = await builder.query.exec('count');
    const q = builder.query
      .populate({ path: 'lastUpdateUser', model: 'User', select: User.USER_PUBLIC_FIELDS });
    const pages = await q.exec('find');

    const result = { pages, totalCount, offset: opt.offset, limit: opt.limit };
    return result;
  };


  /**
   * find pages by PageQueryBuilder
   * @param {PageQueryBuilder} builder
   * @param {User} user
   * @param {any} option
   */
  async function findListFromBuilderAndViewer(builder, user, option) {
    validateCrowi();

    const User = crowi.model('User');

    const opt = Object.assign({sort: 'updatedAt', desc: -1}, option);
    const sortOpt = {};
    sortOpt[opt.sort] = opt.desc;

    // exclude trashed pages
    if (!opt.includeTrashed) {
      builder.addConditionToExcludeTrashed();
    }
    // exclude redirect pages
    if (!opt.includeRedirect) {
      builder.addConditionToExcludeRedirect();
    }

    // add grant conditions
    await addConditionToFilteringByViewerForList(builder, user);

    builder.addConditionToPagenate(opt.offset, opt.limit, sortOpt);

    const totalCount = await builder.query.exec('count');
    const q = builder.query
      .populate({ path: 'lastUpdateUser', model: 'User', select: User.USER_PUBLIC_FIELDS });
    const pages = await q.exec('find');

    const result = { pages, totalCount, offset: opt.offset, limit: opt.limit };
    return result;
  }

  /**
   * Add condition that filter pages by viewer
   *  by considering Config
   *
   * @param {PageQueryBuilder} builder
   * @param {User} user
   */
  async function addConditionToFilteringByViewerForList(builder, user) {
    validateCrowi();

    const Config = crowi.model('Config');
    const config = crowi.getConfig();

    // determine User condition
    const hidePagesRestrictedByOwner = Config.hidePagesRestrictedByOwnerInList(config);
    const userCondition = hidePagesRestrictedByOwner ? user : null;

    // determine UserGroup condition
    let groupCondition = null;
    const hidePagesRestrictedByGroup = Config.hidePagesRestrictedByGroupInList(config);
    if (hidePagesRestrictedByGroup && user != null) {
      const UserGroupRelation = crowi.model('UserGroupRelation');
      groupCondition = await UserGroupRelation.findAllUserGroupIdsRelatedToUser(user);
    }

    return builder.addConditionToFilteringByViewer(userCondition, groupCondition);
  }

  /**
   * export addConditionToFilteringByViewerForList as static method
   */
  pageSchema.statics.addConditionToFilteringByViewerForList = async function(builder, user) {
    return addConditionToFilteringByViewerForList(builder, user);
  };

  /**
   * Throw error for growi-lsx-plugin (v1.x)
   */
  pageSchema.statics.generateQueryToListByStartWith = function(path, user, option) {
    const dummyQuery = this.find();
    dummyQuery.exec = async() => {
      throw new Error('Plugin version mismatch. Upgrade growi-lsx-plugin to v2.0.0 or above.');
    };
    return dummyQuery;
  };
  pageSchema.statics.generateQueryToListWithDescendants = pageSchema.statics.generateQueryToListByStartWith;


  /**
   * find all templates applicable to the new page
   */
  pageSchema.statics.findTemplate = function(path) {
    const templatePath = nodePath.posix.dirname(path);
    const pathList = generatePathsOnTree(path, []);
    const regexpList = pathList.map(path => new RegExp(`^${escapeStringRegexp(path)}/_{1,2}template$`));

    return this
      .find({path: {$in: regexpList}})
      .populate({path: 'revision', model: 'Revision'})
      .then(templates => {
        return fetchTemplate(templates, templatePath);
      });
  };

  const generatePathsOnTree = (path, pathList) => {
    pathList.push(path);

    if (path === '/') {
      return pathList;
    }

    const newPath = nodePath.posix.dirname(path);

    return generatePathsOnTree(newPath, pathList);
  };

  const assignTemplateByType = (templates, path, type) => {
    for (let i = 0; i < templates.length; i++) {
      if (templates[i].path === `${path}/${type}template`) {
        return templates[i];
      }
    }
  };

  const assignDecendantsTemplate = (decendantsTemplates, path) => {
    const decendantsTemplate = assignTemplateByType(decendantsTemplates, path, '__');
    if (decendantsTemplate) {
      return decendantsTemplate;
    }

    if (path === '/') {
      return;
    }

    const newPath = nodePath.posix.dirname(path);
    return assignDecendantsTemplate(decendantsTemplates, newPath);
  };

  const fetchTemplate = (templates, templatePath) => {
    let templateBody;
    /**
     * get children template
     * __tempate: applicable only to immediate decendants
     */
    const childrenTemplate = assignTemplateByType(templates, templatePath, '_');

    /**
     * get decendants templates
     * _tempate: applicable to all pages under
     */
    const decendantsTemplate = assignDecendantsTemplate(templates, templatePath);

    if (childrenTemplate) {
      templateBody =  childrenTemplate.revision.body;
    }
    else if (decendantsTemplate) {
      templateBody = decendantsTemplate.revision.body;
    }

    return templateBody;
  };

  /**
   * Bulk get (for internal only)
   */
  pageSchema.statics.getStreamOfFindAll = function(options) {
    const criteria = { redirectTo: null };

    return this.find(criteria)
      .populate([
        { path: 'creator', model: 'User' },
        { path: 'revision', model: 'Revision' },
      ])
      .lean()
      .cursor();
  };

  async function pushRevision(pageData, newRevision, user, grant, grantUserGroupId) {
    await newRevision.save();
    debug('Successfully saved new revision', newRevision);

    pageData.revision = newRevision;
    pageData.lastUpdateUser = user;
    pageData.updatedAt = Date.now();

    return pageData.save();
  }

  async function applyGrant(page, user, grant, grantUserGroupId) {
    if (grant == GRANT_USER_GROUP && grantUserGroupId == null) {
      throw new Error('grant userGroupId is not specified');
    }

    page.grant = grant;
    if (grant == GRANT_PUBLIC || grant == GRANT_USER_GROUP) {
      page.grantedUsers = [];
    }
    else {
      page.grantedUsers = [];
      page.grantedUsers.push(user._id);
    }

    if (grant == GRANT_USER_GROUP) {
      const UserGroupRelation = crowi.model('UserGroupRelation');
      const count = await UserGroupRelation.countByGroupIdAndUser(grantUserGroupId, user);

      if (count === 0) {
        throw new Error('no relations were exist for group and user.');
      }

      page.grantedGroup = grantUserGroupId;
    }
  }

  pageSchema.statics.create = function(path, body, user, options = {}) {
    validateCrowi();

    const Page = this
      , Revision = crowi.model('Revision')
      , format = options.format || 'markdown'
      , redirectTo = options.redirectTo || null
      , grantUserGroupId = options.grantUserGroupId || null
      , socketClientId = options.socketClientId || null
      ;

    let grant = options.grant || GRANT_PUBLIC;

    // sanitize path
    path = crowi.xss.process(path);

    // force public
    if (isPortalPath(path)) {
      grant = GRANT_PUBLIC;
    }

    let savedPage = undefined;
    return Page.findOne({path: path})
      .then(pageData => {
        if (pageData) {
          throw new Error('Cannot create new page to existed path');
        }

        const newPage = new Page();
        newPage.path = path;
        newPage.creator = user;
        newPage.lastUpdateUser = user;
        newPage.createdAt = Date.now();
        newPage.updatedAt = Date.now();
        newPage.redirectTo = redirectTo;
        newPage.status = STATUS_PUBLISHED;
        applyGrant(newPage, user, grant, grantUserGroupId);

        return newPage.save();
      })
      .then((newPage) => {
        savedPage = newPage;
      })
      .then(() => {
        const newRevision = Revision.prepareRevision(savedPage, body, null, user, {format: format});
        return pushRevision(savedPage, newRevision, user);
      })
      .then(() => {
        if (socketClientId != null) {
          pageEvent.emit('create', savedPage, user, socketClientId);
        }
        return savedPage;
      });
  };

  pageSchema.statics.updatePage = async function(pageData, body, previousBody, user, options = {}) {
    validateCrowi();

    const Page = this
      , Revision = crowi.model('Revision')
      , grant = options.grant || null
      , grantUserGroupId = options.grantUserGroupId || null
      , isSyncRevisionToHackmd = options.isSyncRevisionToHackmd
      , socketClientId = options.socketClientId || null
      ;

    // update existing page
    applyGrant(pageData, user, grant, grantUserGroupId);
    let savedPage = await pageData.save();
    const newRevision = await Revision.prepareRevision(pageData, body, previousBody, user);
    const revision = await pushRevision(savedPage, newRevision, user, grant, grantUserGroupId);
    savedPage = await Page.findByPath(revision.path).populate('revision').populate('creator');

    if (isSyncRevisionToHackmd) {
      savedPage = await Page.syncRevisionToHackmd(savedPage);
    }

    if (socketClientId != null) {
      pageEvent.emit('update', savedPage, user, socketClientId);
    }
    return savedPage;
  };

  pageSchema.statics.deletePage = async function(pageData, user, options = {}) {
    const newPath = this.getDeletedPageName(pageData.path)
      , isTrashed = checkIfTrashed(pageData.path)
      , socketClientId = options.socketClientId || null
      ;

    if (this.isDeletableName(pageData.path)) {
      if (isTrashed) {
        return this.completelyDeletePage(pageData, user, options);
      }

      pageData.status = STATUS_DELETED;
      const updatedPageData = await this.rename(pageData, newPath, user, {createRedirectPage: true});

      if (socketClientId != null) {
        pageEvent.emit('delete', updatedPageData, user, socketClientId);
      }
      return updatedPageData;
    }
    else {
      return Promise.reject('Page is not deletable.');
    }
  };

  const checkIfTrashed = (path) => {
    return (path.search(/^\/trash/) !== -1);
  };

  pageSchema.statics.deletePageRecursively = async function(targetPage, user, options = {}) {
    const isTrashed = checkIfTrashed(targetPage.path);

    if (isTrashed) {
      return this.completelyDeletePageRecursively(targetPage, user, options);
    }

    const findOpts = { includeRedirect: true };
    const result = await this.findListWithDescendants(targetPage.path, user, findOpts);
    const pages = result.pages;

    let updatedPage = null;
    await Promise.all(pages.map(page => {
      const isParent = (page.path === targetPage.path);
      const p = this.deletePage(page, user, options);
      if (isParent) {
        updatedPage = p;
      }
      return p;
    }));

    return updatedPage;
  };

  pageSchema.statics.revertDeletedPage = async function(page, user, options = {}) {
    const newPath = this.getRevertDeletedPageName(page.path);

    const originPage = await this.findByPath(newPath);
    if (originPage != null) {
      // 削除時、元ページの path には必ず redirectTo 付きで、ページが作成される。
      // そのため、そいつは削除してOK
      // が、redirectTo ではないページが存在している場合それは何かがおかしい。(データ補正が必要)
      if (originPage.redirectTo !== page.path) {
        throw new Error('The new page of to revert is exists and the redirect path of the page is not the deleted page.');
      }

      await this.completelyDeletePage(originPage, options);
    }

    page.status = STATUS_PUBLISHED;
    page.lastUpdateUser = user;
    debug('Revert deleted the page', page, newPath);
    const updatedPage = await this.rename(page, newPath, user, {});

    return updatedPage;
  };

  pageSchema.statics.revertDeletedPageRecursively = async function(targetPage, user, options = {}) {
    const findOpts = { includeRedirect: true, includeTrashed: true };
    const result = await this.findListWithDescendants(targetPage.path, user, findOpts);
    const pages = result.pages;

    let updatedPage = null;
    await Promise.all(pages.map(page => {
      const isParent = (page.path === targetPage.path);
      const p = this.revertDeletedPage(page, user, options);
      if (isParent) {
        updatedPage = p;
      }
      return p;
    }));

    return updatedPage;
  };

  /**
   * This is danger.
   */
  pageSchema.statics.completelyDeletePage = async function(pageData, user, options = {}) {
    validateCrowi();

    // Delete Bookmarks, Attachments, Revisions, Pages and emit delete
    const Bookmark = crowi.model('Bookmark');
    const Attachment = crowi.model('Attachment');
    const Comment = crowi.model('Comment');
    const Revision = crowi.model('Revision');
    const PageGroupRelation = crowi.model('PageGroupRelation');
    const pageId = pageData._id;
    const socketClientId = options.socketClientId || null;

    debug('Completely delete', pageData.path);

    await Bookmark.removeBookmarksByPageId(pageId);
    await Attachment.removeAttachmentsByPageId(pageId);
    await Comment.removeCommentsByPageId(pageId);
    await Revision.removeRevisionsByPath(pageData.path);
    await this.findByIdAndRemove(pageId);
    await this.removeRedirectOriginPageByPath(pageData.path);
    await PageGroupRelation.removeAllByPage(pageData);
    if (socketClientId != null) {
      pageEvent.emit('delete', pageData, user, socketClientId); // update as renamed page
    }
    return pageData;
  };

  /**
   * Delete Bookmarks, Attachments, Revisions, Pages and emit delete
   */
  pageSchema.statics.completelyDeletePageRecursively = async function(pageData, user, options = {}) {
    const path = pageData.path;

    const findOpts = { includeRedirect: true, includeTrashed: true };
    const result = await this.findListWithDescendants(path, user, findOpts);
    const pages = result.pages;

    await Promise.all(pages.map(page => {
      return this.completelyDeletePage(page, user, options);
    }));

    return pageData;
  };

  pageSchema.statics.removeByPath = function(path) {
    if (path == null) {
      throw new Error('path is required');
    }
    return this.findOneAndRemove({ path }).exec();
  };

  /**
   * remove the page that is redirecting to specified `pagePath` recursively
   *  ex: when
   *    '/page1' redirects to '/page2' and
   *    '/page2' redirects to '/page3'
   *    and given '/page3',
   *    '/page1' and '/page2' will be removed
   *
   * @param {string} pagePath
   */
  pageSchema.statics.removeRedirectOriginPageByPath = async function(pagePath) {
    const redirectPage = await this.findByRedirectTo(pagePath);

    if (redirectPage == null) {
      return;
    }

    // remove
    await this.findByIdAndRemove(redirectPage.id);
    // remove recursive
    await this.removeRedirectOriginPageByPath(redirectPage.path);
  };

  pageSchema.statics.rename = async function(pageData, newPagePath, user, options) {
    validateCrowi();

    const Page = this
      , Revision = crowi.model('Revision')
      , path = pageData.path
      , createRedirectPage = options.createRedirectPage || 0
      , socketClientId = options.socketClientId || null
      ;

    // sanitize path
    newPagePath = crowi.xss.process(newPagePath);

    // update Page
    pageData.path = newPagePath;
    pageData.lastUpdateUser = user;
    pageData.updatedAt = Date.now();
    const updatedPageData = await pageData.save();

    // update Rivisions
    await Revision.updateRevisionListByPath(path, {path: newPagePath}, {});

    if (createRedirectPage) {
      const body = 'redirect ' + newPagePath;
      await Page.create(path, body, user, {redirectTo: newPagePath});
    }

    pageEvent.emit('delete', pageData, user, socketClientId);
    pageEvent.emit('create', updatedPageData, user, socketClientId);

    return updatedPageData;
  };

  pageSchema.statics.renameRecursively = async function(pageData, newPagePathPrefix, user, options) {
    validateCrowi();

    const path = pageData.path;
    const pathRegExp = new RegExp('^' + escapeStringRegexp(path), 'i');

    // sanitize path
    newPagePathPrefix = crowi.xss.process(newPagePathPrefix);

    const result = await this.findListWithDescendants(path, user, options);
    await Promise.all(result.pages.map(page => {
      const newPagePath = page.path.replace(pathRegExp, newPagePathPrefix);
      return this.rename(page, newPagePath, user, options);
    }));
    pageData.path = newPagePathPrefix;
    return pageData;
  };

  /**
   * associate GROWI page and HackMD page
   * @param {Page} pageData
   * @param {string} pageIdOnHackmd
   */
  pageSchema.statics.registerHackmdPage = function(pageData, pageIdOnHackmd) {
    if (pageData.pageIdOnHackmd != null) {
      throw new Error(`'pageIdOnHackmd' of the page '${pageData.path}' is not empty`);
    }

    pageData.pageIdOnHackmd = pageIdOnHackmd;

    return this.syncRevisionToHackmd(pageData);
  };

  /**
   * update revisionHackmdSynced
   * @param {Page} pageData
   * @param {bool} isSave whether save or not
   */
  pageSchema.statics.syncRevisionToHackmd = function(pageData, isSave = true) {
    pageData.revisionHackmdSynced = pageData.revision;
    pageData.hasDraftOnHackmd = false;

    let returnData = pageData;
    if (isSave) {
      returnData = pageData.save();
    }
    return returnData;
  };

  /**
   * update hasDraftOnHackmd
   * !! This will be invoked many time from many people !!
   *
   * @param {Page} pageData
   * @param {Boolean} newValue
   */
  pageSchema.statics.updateHasDraftOnHackmd = async function(pageData, newValue) {
    if (pageData.hasDraftOnHackmd === newValue) {
      // do nothing when hasDraftOnHackmd equals to newValue
      return;
    }

    pageData.hasDraftOnHackmd = newValue;
    return pageData.save();
  };

  pageSchema.statics.getHistories = function() {
    // TODO
    return;
  };

  /**
   * return path that added slash to the end for specified path
   */
  pageSchema.statics.addSlashOfEnd = function(path) {
    return addSlashOfEnd(path);
  };

  pageSchema.statics.allPageCount = function() {
    return this.count({ redirectTo: null });
  };

  pageSchema.statics.GRANT_PUBLIC = GRANT_PUBLIC;
  pageSchema.statics.GRANT_RESTRICTED = GRANT_RESTRICTED;
  pageSchema.statics.GRANT_SPECIFIED = GRANT_SPECIFIED;
  pageSchema.statics.GRANT_OWNER = GRANT_OWNER;
  pageSchema.statics.GRANT_USER_GROUP = GRANT_USER_GROUP;
  pageSchema.statics.PAGE_GRANT_ERROR = PAGE_GRANT_ERROR;

  pageSchema.statics.PageQueryBuilder = PageQueryBuilder;

  return mongoose.model('Page', pageSchema);
};