function Pager(tableName, itemsPerPage) {
    this.tableName = tableName;
    this.itemsPerPage = itemsPerPage;
    this.currentPage = 1;
    this.pages = 0;
    this.inited = false;
    
    this.showRecords = function(from, to) {        
        var rows = document.getElementById(tableName).rows;
        // i starts from 1 to skip table header row
        for (var i = 0; i < rows.length; i++) {
            if (i < from || i > to)  
                rows[i].style.display = 'none';
            else
                rows[i].style.display = '';
        }
    }
    
    this.showPage = function(pageNumber) {
    	if (! this.inited) {
    		alert("not inited");
    		return;
    	}

        var oldPageAnchor = document.getElementById('pg'+this.currentPage);
        oldPageAnchor.className = '';
        
        this.currentPage = pageNumber;
        var newPageAnchor = document.getElementById('pg'+this.currentPage);
        newPageAnchor.className = 'paging-current';
        
        var from = (pageNumber - 1) * itemsPerPage + 1;
        var to = from + itemsPerPage - 1;
        this.showRecords(from, to);
	    this.showPageNav("pager", "pagenav");
    }   
    
    this.prev = function() {
        if (this.currentPage > 1)
            this.showPage(this.currentPage - 1);
    }
    
    this.next = function() {
        if (this.currentPage < this.pages) {
            this.showPage(this.currentPage + 1);
        }
    }                        
    
    this.init = function() {
        var rows = document.getElementById(tableName).rows;
        var records = (rows.length - 1); 
        this.pages = Math.ceil(records / itemsPerPage);
        this.inited = true;
    }

    this.showPageNav = function(pagerName, positionId) {
    	if (! this.inited) {
    		alert("not inited");
    		return;
    	}
    	var pagecount = 10;
	var page = this.currentPage-5>0?this.currentPage-5:1;
	if (this.pages - this.currentPage < 5 && page > 5) page = page - 4 + this.pages - this.currentPage;
    	var element = document.getElementById(positionId);
    	
    	var pagerHtml = '<p>Pages: </p>';
	if (this.currentPage != 1) pagerHtml += '<a onclick="' + pagerName + '.prev();"> Prev </a>';
	for (; page < this.currentPage; page++,pagecount--) 
		pagerHtml += '<a id="pg' + page + '" onclick="' + pagerName + '.showPage(' + page + ');">' + page + '</a>';
	pagerHtml += '<a id="pg' + page + '" onclick="' + pagerName + '.showPage(' + page + ');" class="paging-current" >' + page + '</a>';
        for ( page = page+1, pagecount = pagecount - 1; page <= this.pages && pagecount > 0; page++, pagecount--) 
            pagerHtml += '<a id="pg' + page + '" onclick="' + pagerName + '.showPage(' + page + ');">' + page + '</a>';
	if (this.currentPage != this.pages)
	        pagerHtml += '<a onclick="'+pagerName+'.next();" >Next</a>'; 
           
		
        element.innerHTML = pagerHtml;
    }
}