Db = function() {
  //initial comment db as objs (TREE LIKE MODEL : replies are included in comment.replies)
  this.comments = null; // current set of (filtered) comments 
  this.allComments = null; // all server database comments

  // obj
  // keys : commentDbId as string 
  // values : comment db as obj
  this.commentsByDbId = {};
  this.allCommentsByDbId = {};
  
  // dictionary (always contains all comments (no reply) whatever the filter
  // order key --> ordered array of comment ids (no reply)
  this.ordered_comment_ids = {}; // all server database comments
  
}

Db.prototype = {
    
//////////////////////////////
//    CORE FUNCTIONS
//////////////////////////////
  init : function() {
    // at first server side ordered comment by asc ids, replies by creation date :
    this.allComments = CY.JSON.parse(sv_comments) ;
    if (sv_read_only) {
      this.initToReadOnly() ;
    }
    
      this._computeAllCommentsByDbId() ;
      
      this._reorder() ;
  },
  
  _del : function (arr, dic, id) {
    // first recursively remove all replies
    var comment = dic[id] ;
    
    for (var i = 0 ; i < comment.replies.length ; i++) {
      var rid = comment.replies[i].id ;
      this._del(comment.replies, dic, rid) ;
      i--;
    }
    
    for (var i = 0, ilen = arr.length ; i < ilen ; i++) {
      if (arr[i].id == id) {
        arr.splice(i, 1) ;
        delete dic[id] ;
        break ;
      }
    }
  },

  del : function(comment) {
    var arr = (comment.reply_to_id == null) ? this.comments : this.commentsByDbId[comment.reply_to_id].replies ; 
    this._del(arr, this.commentsByDbId, comment.id) ;
    arr = (comment.reply_to_id == null) ? this.allComments : this.allCommentsByDbId[comment.reply_to_id].replies ; 
    this._del(arr, this.allCommentsByDbId, comment.id) ;
    
    this._reorder() ;
    
  },
  
  // maintains the ordered lists
  _reorder : function() {
    
    // scope (order by start_wrapper, start_offset, end_wrapper, end_offset 
    var a = [] ;
      
    for (var i = 0, ilen = this.allComments.length ; i < ilen ; i++) {
      
      var comment = this.allComments[i] ;
      var found = false ;

      for (var j = 0, jlen = a.length ; j < jlen ; j++) {
        
        var id = a[j] ;
        var comment2 = this.allCommentsByDbId[id] ;
        
        if ((comment.start_wrapper < comment2.start_wrapper)
          ||
          ((comment.start_wrapper == comment2.start_wrapper) && (comment.start_offset < comment2.start_offset) )
          ||
          ((comment.start_wrapper == comment2.start_wrapper) && (comment.start_offset == comment2.start_offset) && (comment.end_wrapper < comment2.end_wrapper) ) 
          ||
          ((comment.start_wrapper == comment2.start_wrapper) && (comment.start_offset == comment2.start_offset) && (comment.end_wrapper == comment2.end_wrapper) && (comment.end_offset < comment2.end_offset) ) ) {
            a.splice(j, 0, comment.id) ;
            found = true ;
            break ;
          }
      }
      if (!found)  {
        a.push(comment.id) ;
      }
    }
    this.ordered_comment_ids['scope']  = a ;
    
    // modified thread  
    a = [] ;
    var mod = {} ; // we'll aggregate modification dates in this assoc array id --> latest modification
      
    for (var i = 0, ilen = this.allComments.length ; i < ilen ; i++) {
      
      var comment = this.allComments[i] ;
      var commentModif = comment.modified ;
      
      mod[comment.id] = this._latest_mod(comment);
    }
    
    for (var id in mod) {
      var numberId = this.allCommentsByDbId[id].id      
      var found = false ;
      for (var i = 0, ilen = a.length ; i < ilen ; i++) {
        var id2 = a[i] ;
        
        if (mod[id] < mod[id2]) {
          a.splice(i, 0, numberId) ;
          found = true ;
          break ;
        }
        
      }
      if (!found)  {
        a.push(numberId) ;
      }
    }
    
    this.ordered_comment_ids['modif_thread'] = a ; 
  },

   // Finds recursively the last modification date of a thread.
  _latest_mod : function(comment) {
    var latest_mod = comment.modified;
    for (var i=0; i<comment.replies.length; i++) {
      var reply = comment.replies[i] ;
      var reply_mod = this._latest_mod(reply);
      if (reply_mod > latest_mod)
        latest_mod = reply_mod;
    }
    return latest_mod;
  },

  // EDIT OR ADD CASE : when just added id is max and so both (comments and replies) initial id asc order remains
  _upd : function(arr, dic, c) {
    var found = false ;
    for (var i = 0, ilen = arr.length ; i < ilen ; i++) {
      if (arr[i].id == c.id) { // edit
        arr.splice(i, 1, c) ;
        found = true ;
        break ;
      }
    }
    
    if (!found) { // add
      arr.push(c) ;
    }
    
    dic[c.id] = c ;
  },

  // EDIT OR ADD CASE : when just added id is max and so both (comments and replies) initial id asc order respected
  upd : function(comment) {
    var arr = (comment.reply_to_id == null) ? this.allComments : this.allCommentsByDbId[comment.reply_to_id].replies ; 
    this._upd(arr, this.allCommentsByDbId, comment) ;
    
    var cloneComment = CY.clone(comment) ;
    
    arr = (comment.reply_to_id == null) ? this.comments : this.commentsByDbId[comment.reply_to_id].replies ; 
    this._upd(arr, this.commentsByDbId, cloneComment) ;
    
    this._reorder() ;   
    
  },

  // initializes this.comments
  // commentId is the result of a computeFilterResults call : no assumption can be made on the order of ids (!)
  // so we'll loop through allComments to carry order from allComments to comments
  initComments : function(commentIds) {
      this.comments = [] ;
    for (var i = 0, ilen = this.allComments.length ; i < ilen ; i++) {
      
      var index = CY.Array.indexOf(commentIds, this.allComments[i].id) ;
      if (index != -1) {
        
        var cloneComment = CY.clone(this.allComments[i]) ;
        
        this.comments.push(cloneComment) ;
      }
    }
      this._computeCommentsByDbId() ;
  },

  _computeCommentsByDbId : function() {
    this.commentsByDbId = {} ;
      var flatComments = this.getThreads(this.comments) ;
    for ( var i = 0; i < flatComments.length; i++)
      this.commentsByDbId[flatComments[i].id] = flatComments[i];
  },
  
  _computeAllCommentsByDbId : function() {
    this.allCommentsByDbId = {} ;
      var flatComments = this.getThreads(this.allComments) ;
    for (var i = 0; i < flatComments.length; i++) 
      this.allCommentsByDbId[flatComments[i].id] = flatComments[i];
  },
  
  // returns threads :
  // given an array [comment1, comment2, comment3], this function will return [comment1, comment1reply1, comment1reply1reply1, comment1reply1reply2, comment2, comment3, comment3reply1]
  //note : will return top parents ordered the way comments are
  getThreads : function(comments) {
    var ret = [] ;

    for (var i = 0 ; i < comments.length ; i++) {
      ret.push(comments[i]) ;
      if (comments[i].replies.length > 0)
        ret = ret.concat(this.getThreads(comments[i].replies)) ;
    }
    return ret ;
  },
  _getPath : function(dic, comment) {
    var ret = [comment] ;
    
    var c = comment ;
    while (c.reply_to_id != null) {
      c = dic[c.reply_to_id] ;
      ret.push(c) ;
    }
      
    return ret ;
  },
  // returns comments as array : [comment, ..., comment's top parent]
  getPath : function(comment) {
    return this._getPath(this.commentsByDbId, comment) ;
  },
  // getCommentFromIComment ...
  getComment : function(dbId) {
    return this.commentsByDbId[dbId] ;
  },  
  
  getCommentByIdKey : function(id_key) {
    for (var id in this.commentsByDbId) {
      var comment = this.commentsByDbId[id] ;
      if (comment.id_key == id_key) { 
        return comment ;
      }
    }
    return null ;
  },  
  
  isChild : function(commentDbId, parentDbId) {
    var comment = this.commentsByDbId[commentDbId] ;
    
    var isChild = (commentDbId == parentDbId) ;
    
    while ((!isChild) && (comment.reply_to_id != null)) {
      comment = this.commentsByDbId[comment.reply_to_id] ;
      isChild = (comment.id == parentDbId) ; ;
    }
    return isChild ;
  },  
  
  initToReadOnly : function(commentDbId, parentDbId) {
    for (var i = 0, ilen = this.allComments.length ; i < ilen ; i++) {
      var comment = this.allComments[i] ;
      for (var prop in comment) {
        if (0 == prop.indexOf("can_") && typeof comment[prop] === 'boolean')
          comment[prop] = false ;
      }
    }
  },  
  
//////////////////////////////
//  BROWSING FUNCTIONS
//////////////////////////////

  browsingIndex : function(dbId) {
    var indx = {} ;
    for (var order in this.ordered_comment_ids) {
      var inFilter =  CY.Array.filter(this.ordered_comment_ids[order], function(id) {return (id in this.commentsByDbId);}, this) ;
      indx[order] = CY.Array.indexOf(inFilter, dbId ) ;
    }
    //indx['total'] = this.ordered_comment_ids['scope'].length
    return indx ;
  },
  
  browse : function(order, whereto, dbId) {
    //var arr = this.ordered_comment_ids[gConf['defaultBrowsingOrder']] ;
//    CY.log(order) ;
    var arr = this.ordered_comment_ids[order] ;
    if (arr.length > 0) {
    
      var starti = -1 ; 
      if ((whereto == 'prev') || (whereto == 'next')) {
        
        for (var i = 0 ; i < arr.length ; i++) {
          var id = arr[i] ;
          if (id == dbId) {
            starti = (whereto == 'prev') ? i - 1 : i + 1 ;
            starti = (arr.length + starti) % arr.length ; // to guaranty a positive value 
            break ;
          }
        }
        if (starti == -1) {
          CY.error("internal error in db browse (was called with a dbId that isn't among the filtered ones)") ;
          return null;
        }
      }
      if (whereto == 'last') {
        starti = arr.length - 1 ;
      }
      if (whereto == 'first') {
        starti = 0 ;
      }
  
      for (var i = starti, j = 0 ; (i >= 0) && (i < arr.length) ; j++ ) {
        var id = arr[i] ;
        if (id in this.commentsByDbId) // checking id is among the filtered ones
          return this.commentsByDbId[id] ;
        if ((whereto == 'prev') || (whereto == 'last')) 
          i = i - 1 ;
        else  
          i = i + 1 ;
        i = (arr.length + i) % arr.length ; // to guaranty a positive value
        if (j > arr.length)// to prevent an infinite loop
          break ;
      }
      
      CY.error("internal error in db browse (could not find any filtered comment)") ;
    }
    return null;
  },
  
//////////////////////////////
//  FILTER FUNCTIONS
//////////////////////////////
  
  //returns the list of commentIds satisfying the filter
  computeFilterResults : function(filterGETValues) {
      var filterData = {} ;
      if (filterGETValues) {
      for (key in filterGETValues) {
        if (key.indexOf('filter_') == 0) 
          filterData[key.substr('filter_'.length)] = filterGETValues[key];
      }
      }
      else {
      if (gLayout.isInFrame()) 
        filterData = parent.f_getFrameFilterData() ;
      }

    var cWithNameIds = [] ;
    var rWithNameIds = [] ;
    var filterName = "" ;
    if ('name' in filterData)
      filterName = filterData['name'] ;
    this.filterByName(filterName, cWithNameIds, rWithNameIds) ;
    
    var cAfterDateIds = [] ;
    var rAfterDateIds = [] ;
    var filterDate = "" ;
    if ('date' in filterData)
      filterDate = filterData['date'] ;
    this.filterByDate(filterDate, cAfterDateIds, rAfterDateIds) ;

    var cWithTextIds = [] ;
    var rWithTextIds = [] ;
    var filterText = "" ;
    if ('text' in filterData)
      filterText = filterData['text'] ;
    this.filterByText(filterText, cWithTextIds, rWithTextIds) ;
    
    var cWithTagIds = [] ;
    var rWithTagIds = [] ;
    var filterTag = "" ;
    if ('tag' in filterData)
      filterTag = filterData['tag'] ;
    this.filterByTag(filterTag, cWithTagIds, rWithTagIds) ;
    
    var cWithStateIds = [] ;
    var rWithStateIds = [] ;
    var filterState = "" ;
    if ('state' in filterData)
      filterState = filterData['state'] ;
    this.filterByState(filterState, cWithStateIds, rWithStateIds) ;
    
    
    var commentIds = [] ;
    var replyIds = [] ;
    // find intersections
    for (var i = 0, ilen = cWithNameIds.length ; i < ilen ; i++) {
      var id = cWithNameIds[i] ;
      if ((CY.Array.indexOf(cAfterDateIds, id) != -1) && (CY.Array.indexOf(cWithTextIds,id) != -1) && (CY.Array.indexOf(cWithTagIds,id) != -1) && (CY.Array.indexOf(cWithStateIds,id) != -1)) {
        commentIds.push(id) ; 
      }
    }
    
    for (var i = 0, ilen = rWithNameIds.length ; i < ilen ; i++) {
      var id = rWithNameIds[i] ;
      if ((CY.Array.indexOf(rAfterDateIds,id) != -1) && (CY.Array.indexOf(rWithTextIds,id) != -1) && (CY.Array.indexOf(rWithTagIds,id) != -1) && (CY.Array.indexOf(rWithStateIds,id) != -1)) {
        replyIds.push(id) ; 
      }
    }
    
    var nbReplies = replyIds.length, nbComments = commentIds.length ;
    var nbDiscussions = nbComments ;
    
    // look for comments to add because a reply satisfies the filter
//    CY.log('replyIds:') ;
//    CY.log(replyIds) ;
//    CY.log('this.allCommentsByDbId :');CY.A
//    CY.log(this.allCommentsByDbId);
    for (var i = 0, ilen = replyIds.length ; i < ilen ; i++) {
      var id = replyIds[i] ;
      var reply = this.allCommentsByDbId[id] ;
      var parents = this._getPath(this.allCommentsByDbId, reply) ;
      var topComment = parents[parents.length - 1] ;
      var id = topComment.id ;
      if (CY.Array.indexOf(commentIds,id) == -1) {
        commentIds.push(id) ;
        nbDiscussions++ ;
      }
    }
    
    return {'commentIds': commentIds,'nbDiscussions':nbDiscussions, 'nbComments':nbComments, 'nbReplies':nbReplies} ;
  },

  filterByText : function(text, cWithTextIds, rWithTextIds) {
    var re = new RegExp(text, "gi");
    for (var id in this.allCommentsByDbId) {
      var comment = this.allCommentsByDbId[id] ;
      if (text == "" || re.exec(comment.title) != null || re.exec(comment.content) != null) { // search only in the comment (not the comment scope) for now
        if (comment.reply_to_id == null) 
          cWithTextIds.push(comment.id);
        else 
          rWithTextIds.push(comment.id) ;
      }
    }
  },

  filterByName : function(name, cWithNameIds, rWithNameIds) {
    for (var id in this.allCommentsByDbId) {
      var comment = this.allCommentsByDbId[id] ;
      if (name == "" || comment.name == name) { // sensitive exact match for now
        if (comment.reply_to_id == null) 
          cWithNameIds.push(comment.id);
        else 
          rWithNameIds.push(comment.id) ;
      }
    }
  },

  // warning : tags are case sensitive
  filterByTag : function(tag, cWithTagIds, rWithTagIds) {
    // cf ", ".join... in client.py 
    var re0 = new RegExp("^" + tag + "$", ''); 
    var re1 = new RegExp("^" + tag + ", ", '');
    var re2 = new RegExp(", " + tag + ", ", ''); 
    var re3 = new RegExp(", " + tag + "$", ''); 
    for (var id in this.allCommentsByDbId) {
      var comment = this.allCommentsByDbId[id] ;
      if ((tag == "") || re0.exec(comment.tags) != null || re1.exec(comment.tags) != null || re2.exec(comment.tags) != null || re3.exec(comment.tags) != null) { // search only in the comment (not the comment scope) for now
        if (comment.reply_to_id == null) 
          cWithTagIds.push(comment.id);
        else 
          rWithTagIds.push(comment.id) ;
      }
    }
  },

  filterByState : function(state, cWithStateIds, rWithStateIds) {
    for (var id in this.allCommentsByDbId) {
      var comment = this.allCommentsByDbId[id] ;
      if (state == "" || comment.state == state) { 
        if (comment.reply_to_id == null) 
          cWithStateIds.push(comment.id);
        else 
          rWithStateIds.push(comment.id) ;
      }
    }
  },

  filterByDate : function(date_str, cAfterDateIds, rAfterDateIds) {
    var date = (date_str == "") ? 0 : parseInt(date_str) ;
    for (var id in this.allCommentsByDbId) {
      var comment = this.allCommentsByDbId[id] ;
      if (comment.modified > date) { 
        if (comment.reply_to_id == null) 
          cAfterDateIds.push(comment.id); 
        else 
          rAfterDateIds.push(comment.id) ;
      }
    }
  },
//  filterByDate : function(date_str, cAfterDateIds, rAfterDateIds) {
//    var date = (date_str == "") ? "" : Date.parseDate(date_str, sv_client_date_fmt).getTime() ;
//    for (var id in this.allCommentsByDbId) {
//      var comment = this.allCommentsByDbId[id] ;
//      // TODO : created should be the date not a string !!
//      var create_date = (date_str == "") ? "" : Date.parseDate(comment.created_str, sv_client_date_fmt).getTime() ;
//      if (date_str == "" || create_date > date) { 
//        if (comment.reply_to_id == null) 
//          cAfterDateIds.push(comment.id); 
//        else 
//          rAfterDateIds.push(comment.id) ;
//      }
//    }
//  },
  
//////////////////////////////
//  COUNT FUNCTIONS
//////////////////////////////
  
  getCommentsAndRepliesCounts : function(all) {
    var cCount = 0 ;
    var rCount = 0 ;
    var arr = (all) ? this.allComments:this.comments;
      var flatComments = this.getThreads(arr) ;
    for ( var i = 0; i < flatComments.length; i++) {
      if (flatComments[i].reply_to_id == null)
        cCount++ ;
      else 
        rCount++ ;
    }
    return [cCount, rCount] ;
  },

  // counts both comments and comments 
  getCommentsNb : function(all) {
    var arr = (all) ? this.allComments:this.comments;
      return this.getThreads(arr).length ;
  },
  getFilteredCommentIdsAsString : function() {
    var ret = "" ;
    for (var id in this.commentsByDbId) 
      ret = ret + id + "," ;
    return ret ;
  }
}