var repoindex = (function(repoindex) {

    // Adds a bootstrap pagination to the HTML element with the specified id
    repoindex.Pagination = function(containerId) {
        // basic initialization
        this.containerId = containerId;
        this.containerElement = document.getElementById(containerId);
        this.currentElement = undefined;
        this.elements = [];
        this.entriesPerPage = 20;
        this.entryCount = 0;
        this.visibleElementsBeforeAfter = 7;

        // define a default function which will be called when a pageElement is selected
        this.pageSelected = function() {};

        this.internalPageSelected = function(pageElement) {
            repoindex.pageManager.rehash(pageElement && pageElement.pageIndex > 0 ? function(hash) {
                hash[1].p = pageElement.pageIndex;
            } : function(hash) {
                delete hash[1].p;
            });
            this.pageSelected(pageElement);
        };

        // define a function to create page elements
        this.createPageElement = function() {
            var pageElement = document.createElement("li");
            pageElement.pagination = this;
            var aElement = document.createElement("a");
            aElement.href = "#";
            aElement.pageElement = pageElement;
            pageElement.appendChild(aElement);
            pageElement.setVisible = function(visible) {
                this.style.display = visible ? "inline" : "none";
            };
            pageElement.setEnabled = function(enabled) {
                this.className = enabled ? "" : "disabled";
            };
            pageElement.setActive = function(active) {
                this.className = active ? "active" : "";
            };
            pageElement.setVisible(false);
            return pageElement;
        };

        // initialize the "previous element"
        this.previousElement = this.createPageElement();
        this.previousElement.firstChild.setAttribute("aria-label", "Previous");
        this.previousElement.firstChild.innerHTML = '<span aria-hidden="true">&laquo;</span>';
        this.previousElement.select = function() {
            var currentElement = this.pagination.currentElement;
            if(currentElement && currentElement.previousElement) {
                currentElement.previousElement.select();
            }
        };

        this.previousElement.firstChild.onclick = function() {
            this.pageElement.select();
            return false;
        };
        this.previousElement.setVisible(true);
        this.containerElement.appendChild(this.previousElement);

        // initialize the "next element"
        this.nextElement = this.createPageElement();
        this.nextElement.firstChild.setAttribute("aria-label", "Next");
        this.nextElement.firstChild.innerHTML = '<span aria-hidden="true">&raquo;</span>';
        this.nextElement.select = function() {
            var currentElement = this.pagination.currentElement;
            if(currentElement && currentElement.nextElement) {
                currentElement.nextElement.select();
            }
        };

        // initialize the "settings element"


        this.nextElement.firstChild.onclick = function() {
            this.pageElement.select();
            return false;
        };
        this.nextElement.setVisible(true);
        this.containerElement.appendChild(this.nextElement);

        // provide a function to append a page element
        this.appendPage = function(name) {
            // create and initiate the new page element
            var pageElement = this.createPageElement();

            // provide a select function for the page element (will be called when the page element
            // is clicked)
            pageElement.select = function() {
                // update active/inactive status and visibility of all page elements
                var pagination = this.pagination;
                var updateVisibility = function(index, visible) {
                    var lowest = 0;
                    var highest = pagination.elements.length - 1;
                    var low = index - pagination.visibleElementsBeforeAfter;
                    var high = index + pagination.visibleElementsBeforeAfter;
                    if(low < lowest) {
                        high = Math.min(highest, high + lowest - low);
                        low = lowest;
                    } else if(high > highest) {
                        low = Math.max(lowest, low + highest - high);
                        high = highest;
                    }
                    for(var i = low; i <= high; ++i) {
                        pagination.elements[i].setVisible(visible);
                    }
                }
                if(pagination.currentElement) {
                    updateVisibility(pagination.currentElement.pageIndex, false);
                    pagination.currentElement.setActive(false);
                }
                updateVisibility(this.pageIndex, true);
                this.setActive(true);

                // update status of the containing pagination object
                pagination.currentElement = this;
                pagination.previousElement.setEnabled(this !== pagination.elements.first());
                pagination.nextElement.setEnabled(this !== pagination.elements.last());
                // call the pageSelected function to allow the managing objects to handle the page selection
                pagination.internalPageSelected(this);
            };

            // invokes the specified function for each index of the currently visible range
            pageElement.forRange = function(func, maxIndex) {
                for(var i = this.pageIndex * this.pagination.entriesPerPage, pagesLeft = this.pagination.entriesPerPage;
                    pagesLeft > 0 && i < maxIndex; ++i, --pagesLeft) {
                    func(i);
                }
            };

            // further initialization of the page element
            pageElement.pageName = name;
            var aElement = pageElement.firstChild;
            aElement.appendChild(document.createTextNode(name));
            // invoke the select method of the page element when clicked
            aElement.onclick = function() {
                this.pageElement.select();
                return false;
            };

            if((pageElement.previousElement = this.elements.last())) {
                pageElement.pageIndex = pageElement.previousElement.pageIndex + 1;
                pageElement.previousElement.nextElement = pageElement;
            } else {
                pageElement.pageIndex = 0;
            }

            this.containerElement.insertBefore(pageElement, this.nextElement);
            this.elements.push(pageElement);
        };

        // provide a function to append a range of page elements
        this.appendPageRange = function(from, to) {
            for(var i = from; i <= to; ++i) {
                this.appendPage(i);
            }
        };

        // provide a function to void selection
        this.voidSelection = function() {
            this.currentElement = undefined;
            this.previousElement.setEnabled(false);
            this.nextElement.setEnabled(false);
            this.internalPageSelected();
        }

        // provide a function to remove all page elements
        this.removePages = function(startIndex) {
            if(!startIndex) {
                startIndex = 0;
            }
            for(var i = startIndex, end = this.elements.length; i < end; ++i) {
                this.containerElement.removeChild(this.elements[i]);
            }
            if(startIndex !== 0) {
                this.elements.splice(startIndex, this.elements.length - startIndex);
                this.elements.last().nextElement = null; // ensure the last element has no next element anymore
            } else {
                this.elements = [];
            }
            this.currentElement = undefined;
        };

        // provide a function to update the pagination (after properties such as the entryCount have been changed)
        this.update = function() {
            var requiredPages = Math.ceil(this.entryCount / this.entriesPerPage);
            var currentPages = this.elements.length;
            if(requiredPages < currentPages) {
                this.removePages(requiredPages);
            } else if(currentPages < requiredPages) {
                this.appendPageRange(currentPages + 1, requiredPages);
            }
            // select the noted page or first element or void selection if there are no pages
            if(this.notedPageIndex && (this.notedPageIndex < this.elements.length)) {
                this.elements[this.notedPageIndex].select();
            } else if(this.elements.first()) {
                this.elements.first().select();
            } else {
                this.voidSelection();
            }
        };

        this.currentPageIndex = function() {
            if(this.currentElement && this.currentElement.pageIndex > 0) {
                return this.currentElement.pageIndex;
            }
        };

        this.selectPage = function(pageIndex) {
            if(pageIndex && pageIndex >= 0) {
                this.notedPageIndex = pageIndex;
                if(pageIndex < this.elements.length) {
                    this.elements[pageIndex].select();
                }
            }
        };
    };

    return repoindex;

})(repoindex || {});