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] = commentModif ; 

			for (var j = 0, jlen = comment.replies.length ; j < jlen ; j++) {

				var reply = comment.replies[j] ;

				var replyModif = reply.modified ;

				if (replyModif > mod[comment.id])

					mod[comment.id] = replyModif ;

			}

		}

		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 ; 

	},

	// 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)") ;

		}