PageController = function() {
    this.lookup = new Array();
    this.documents = new Array();
    this.lock = false;
}
PageController.prototype = {
    showDocument: function(id) {
      //dummy
    },
    pushDocument: function(id) {
        this.documents.push(id);
    },
    init: function() {
        //Build lookup table
        this.lookup[this.documents[0]] = new Array();
        this.lookup[this.documents[0]][0] = -1;
        for(var i=1;i<this.documents.length;i++) {
            //Prev
            this.lookup[this.documents[i]] = new Array();
            this.lookup[this.documents[i]][0] = this.documents[i-1];
            //Next
            this.lookup[this.documents[i-1]][1] = this.documents[i];
        }
        this.lookup[this.documents[this.documents.length-1]][1] = -1;
    },
    getPrev: function(id) {
        return this.lookup[id][0];
    },
    getNext: function(id) {
        return this.lookup[id][1];
    }
}