/**
 * dirPagination - AngularJS module for paginating (almost) anything.
 *
 *
 * Credits
 * =======
 *
 * Daniel Tabuenca: https://groups.google.com/d/msg/angular/an9QpzqIYiM/r8v-3W1X5vcJ
 * for the idea on how to dynamically invoke the ng-repeat directive.
 *
 * I borrowed a couple of lines and a few attribute names from the AngularUI Bootstrap project:
 * https://github.com/angular-ui/bootstrap/blob/master/src/pagination/pagination.js
 *
 * Copyright 2014 Michael Bromley <michael@michaelbromley.co.uk>
 */

(function() {

    /**
     * Config
     */
    var moduleName = 'angularUtils.directives.dirPagination';
    var DEFAULT_ID = '__default';

    /**
     * Module
     */
    var module;
    try {
        module = angular.module(moduleName);
    } catch(err) {
        // named module does not exist, so create one
        module = angular.module(moduleName, []);
    }

    module
        .directive('dirPaginate', ['$compile', '$parse', 'paginationService', dirPaginateDirective])
        .directive('dirPaginateNoCompile', noCompileDirective)
        .directive('dirPaginationControls', ['paginationService', 'paginationTemplate', dirPaginationControlsDirective])
        .filter('itemsPerPage', ['paginationService', itemsPerPageFilter])
        .service('paginationService', paginationService)
        .provider('paginationTemplate', paginationTemplateProvider)
        .run(['$templateCache',dirPaginationControlsTemplateInstaller]);

    function dirPaginateDirective($compile, $parse, paginationService) {

        return  {
            terminal: true,
            multiElement: true,
            compile: dirPaginationCompileFn
        };

        function dirPaginationCompileFn(tElement, tAttrs){

            var expression = tAttrs.dirPaginate;
            // regex taken directly from https://github.com/angular/angular.js/blob/master/src/ng/directive/ngRepeat.js#L211
            var match = expression.match(/^\s*([\s\S]+?)\s+in\s+([\s\S]+?)(?:\s+track\s+by\s+([\s\S]+?))?\s*$/);

            var filterPattern = /\|\s*itemsPerPage\s*:[^|]*/;
            if (match[2].match(filterPattern) === null) {
                throw 'pagination directive: the \'itemsPerPage\' filter must be set.';
            }
            var itemsPerPageFilterRemoved = match[2].replace(filterPattern, '');
            var collectionGetter = $parse(itemsPerPageFilterRemoved);

            addNoCompileAttributes(tElement);

            // If any value is specified for paginationId, we register the un-evaluated expression at this stage for the benefit of any
            // dir-pagination-controls directives that may be looking for this ID.
            var rawId = tAttrs.paginationId || DEFAULT_ID;
            paginationService.registerInstance(rawId);

            return function dirPaginationLinkFn(scope, element, attrs){

                // Now that we have access to the `scope` we can interpolate any expression given in the paginationId attribute and
                // potentially register a new ID if it evaluates to a different value than the rawId.
                var paginationId = $parse(attrs.paginationId)(scope) || attrs.paginationId || DEFAULT_ID;
                paginationService.registerInstance(paginationId);

                var repeatExpression = getRepeatExpression(expression, paginationId);
                addNgRepeatToElement(element, attrs, repeatExpression);

                removeTemporaryAttributes(element);
                var compiled =  $compile(element);

                var currentPageGetter = makeCurrentPageGetterFn(scope, attrs, paginationId);
                paginationService.setCurrentPageParser(paginationId, currentPageGetter, scope);

                if (typeof attrs.totalItems !== 'undefined') {
                    paginationService.setAsyncModeTrue(paginationId);
                    scope.$watch(function() {
                        return $parse(attrs.totalItems)(scope);
                    }, function (result) {
                        if (0 <= result) {
                            paginationService.setCollectionLength(paginationId, result);
                        }
                    });
                } else {
                    scope.$watchCollection(function() {
                        return collectionGetter(scope);
                    }, function(collection) {
                        if (collection) {
                            paginationService.setCollectionLength(paginationId, collection.length);
                        }
                    });
                }

                // Delegate to the link function returned by the new compilation of the ng-repeat
                compiled(scope);
            };
        }

        /**
         * If a pagination id has been specified, we need to check that it is present as the second argument passed to
         * the itemsPerPage filter. If it is not there, we add it and return the modified expression.
         *
         * @param expression
         * @param paginationId
         * @returns {*}
         */
        function getRepeatExpression(expression, paginationId) {
            var repeatExpression,
                idDefinedInFilter = !!expression.match(/(\|\s*itemsPerPage\s*:[^|]*:[^|]*)/);

            if (paginationId !== DEFAULT_ID && !idDefinedInFilter) {
                repeatExpression = expression.replace(/(\|\s*itemsPerPage\s*:[^|]*)/, "$1 : '" + paginationId + "'");
            } else {
                repeatExpression = expression;
            }

            return repeatExpression;
        }

        /**
         * Adds the ng-repeat directive to the element. In the case of multi-element (-start, -end) it adds the
         * appropriate multi-element ng-repeat to the first and last element in the range.
         * @param element
         * @param attrs
         * @param repeatExpression
         */
        function addNgRepeatToElement(element, attrs, repeatExpression) {
            if (element[0].hasAttribute('dir-paginate-start') || element[0].hasAttribute('data-dir-paginate-start')) {
                // using multiElement mode (dir-paginate-start, dir-paginate-end)
                attrs.$set('ngRepeatStart', repeatExpression);
                element.eq(element.length - 1).attr('ng-repeat-end', true);
            } else {
                attrs.$set('ngRepeat', repeatExpression);
            }
        }

        /**
         * Adds the dir-paginate-no-compile directive to each element in the tElement range.
         * @param tElement
         */
        function addNoCompileAttributes(tElement) {
            angular.forEach(tElement, function(el) {
                if (el.nodeType === Node.ELEMENT_NODE) {
                    angular.element(el).attr('dir-paginate-no-compile', true);
                }
            });
        }

        /**
         * Removes the variations on dir-paginate (data-, -start, -end) and the dir-paginate-no-compile directives.
         * @param element
         */
        function removeTemporaryAttributes(element) {
            angular.forEach(element, function(el) {
                if (el.nodeType === Node.ELEMENT_NODE) {
                    angular.element(el).removeAttr('dir-paginate-no-compile');
                }
            });
            element.eq(0).removeAttr('dir-paginate-start').removeAttr('dir-paginate').removeAttr('data-dir-paginate-start').removeAttr('data-dir-paginate');
            element.eq(element.length - 1).removeAttr('dir-paginate-end').removeAttr('data-dir-paginate-end');
        }

        /**
         * Creates a getter function for the current-page attribute, using the expression provided or a default value if
         * no current-page expression was specified.
         *
         * @param scope
         * @param attrs
         * @param paginationId
         * @returns {*}
         */
        function makeCurrentPageGetterFn(scope, attrs, paginationId) {
            var currentPageGetter;
            if (attrs.currentPage) {
                currentPageGetter = $parse(attrs.currentPage);
            } else {
                // if the current-page attribute was not set, we'll make our own
                var defaultCurrentPage = paginationId + '__currentPage';
                scope[defaultCurrentPage] = 1;
                currentPageGetter = $parse(defaultCurrentPage);
            }
            return currentPageGetter;
        }
    }

    /**
     * This is a helper directive that allows correct compilation when in multi-element mode (ie dir-paginate-start, dir-paginate-end).
     * It is dynamically added to all elements in the dir-paginate compile function, and it prevents further compilation of
     * any inner directives. It is then removed in the link function, and all inner directives are then manually compiled.
     */
    function noCompileDirective() {
        return {
            priority: 5000,
            terminal: true
        };
    }

    function dirPaginationControlsTemplateInstaller($templateCache) {
        $templateCache.put('angularUtils.directives.dirPagination.template', '<ul class="pagination" ng-if="1 < pages.length"><li ng-if="boundaryLinks" ng-class="{ disabled : pagination.current == 1 }"><a href="" ng-click="setCurrent(1)">&laquo;</a></li><li ng-if="directionLinks" ng-class="{ disabled : pagination.current == 1 }"><a href="" ng-click="setCurrent(pagination.current - 1)">&lsaquo;</a></li><li ng-repeat="pageNumber in pages track by $index" ng-class="{ active : pagination.current == pageNumber, disabled : pageNumber == \'...\' }"><a href="" ng-click="setCurrent(pageNumber)">{{ pageNumber }}</a></li><li ng-if="directionLinks" ng-class="{ disabled : pagination.current == pagination.last }"><a href="" ng-click="setCurrent(pagination.current + 1)">&rsaquo;</a></li><li ng-if="boundaryLinks"  ng-class="{ disabled : pagination.current == pagination.last }"><a href="" ng-click="setCurrent(pagination.last)">&raquo;</a></li></ul>');
    }

    function dirPaginationControlsDirective(paginationService, paginationTemplate) {

        var numberRegex = /^\d+$/;

        return {
            restrict: 'AE',
            templateUrl: function(elem, attrs) {
                return attrs.templateUrl || paginationTemplate.getPath();
            },
            scope: {
                maxSize: '=?',
                onPageChange: '&?',
                paginationId: '=?'
            },
            link: dirPaginationControlsLinkFn
        };

        function dirPaginationControlsLinkFn(scope, element, attrs) {

            // rawId is the un-interpolated value of the pagination-id attribute. This is only important when the corresponding dir-paginate directive has
            // not yet been linked (e.g. if it is inside an ng-if block), and in that case it prevents this controls directive from assuming that there is
            // no corresponding dir-paginate directive and wrongly throwing an exception.
            var rawId = attrs.paginationId ||  DEFAULT_ID;
            var paginationId = scope.paginationId || attrs.paginationId ||  DEFAULT_ID;

            if (!paginationService.isRegistered(paginationId) && !paginationService.isRegistered(rawId)) {
                var idMessage = (paginationId !== DEFAULT_ID) ? ' (id: ' + paginationId + ') ' : ' ';
                throw 'pagination directive: the pagination controls' + idMessage + 'cannot be used without the corresponding pagination directive.';
            }

            if (!scope.maxSize) { scope.maxSize = 9; }
            scope.directionLinks = angular.isDefined(attrs.directionLinks) ? scope.$parent.$eval(attrs.directionLinks) : true;
            scope.boundaryLinks = angular.isDefined(attrs.boundaryLinks) ? scope.$parent.$eval(attrs.boundaryLinks) : false;

            var paginationRange = Math.max(scope.maxSize, 5);
            scope.pages = [];
            scope.pagination = {
                last: 1,
                current: 1
            };
            scope.range = {
                lower: 1,
                upper: 1,
                total: 1
            };

            scope.$watch(function() {
                return (paginationService.getCollectionLength(paginationId) + 1) * paginationService.getItemsPerPage(paginationId);
            }, function(length) {
                if (0 < length) {
                    generatePagination();
                }
            });

            scope.$watch(function() {
                return (paginationService.getItemsPerPage(paginationId));
            }, function(current, previous) {
                if (current != previous && typeof previous !== 'undefined') {
                    goToPage(scope.pagination.current);
                }
            });

            scope.$watch(function() {
                return paginationService.getCurrentPage(paginationId);
            }, function(currentPage, previousPage) {
                if (currentPage != previousPage) {
                    goToPage(currentPage);
                }
            });

            scope.setCurrent = function(num) {
                if (isValidPageNumber(num)) {
                    num = parseInt(num, 10);
                    paginationService.setCurrentPage(paginationId, num);
                }
            };

            function goToPage(num) {
                if (isValidPageNumber(num)) {
                    scope.pages = generatePagesArray(num, paginationService.getCollectionLength(paginationId), paginationService.getItemsPerPage(paginationId), paginationRange);
                    scope.pagination.current = num;
                    updateRangeValues();

                    // if a callback has been set, then call it with the page number as an argument
                    if (scope.onPageChange) {
                        scope.onPageChange({ newPageNumber : num });
                    }
                }
            }

            function generatePagination() {
                var page = parseInt(paginationService.getCurrentPage(paginationId)) || 1;

                scope.pages = generatePagesArray(page, paginationService.getCollectionLength(paginationId), paginationService.getItemsPerPage(paginationId), paginationRange);
                scope.pagination.current = page;
                scope.pagination.last = scope.pages[scope.pages.length - 1];
                if (scope.pagination.last < scope.pagination.current) {
                    scope.setCurrent(scope.pagination.last);
                } else {
                    updateRangeValues();
                }
            }

            /**
             * This function updates the values (lower, upper, total) of the `scope.range` object, which can be used in the pagination
             * template to display the current page range, e.g. "showing 21 - 40 of 144 results";
             */
            function updateRangeValues() {
                var currentPage = paginationService.getCurrentPage(paginationId),
                    itemsPerPage = paginationService.getItemsPerPage(paginationId),
                    totalItems = paginationService.getCollectionLength(paginationId);

                scope.range.lower = (currentPage - 1) * itemsPerPage + 1;
                scope.range.upper = Math.min(currentPage * itemsPerPage, totalItems);
                scope.range.total = totalItems;
            }

            function isValidPageNumber(num) {
                return (numberRegex.test(num) && (0 < num && num <= scope.pagination.last));
            }
        }

        /**
         * Generate an array of page numbers (or the '...' string) which is used in an ng-repeat to generate the
         * links used in pagination
         *
         * @param currentPage
         * @param rowsPerPage
         * @param paginationRange
         * @param collectionLength
         * @returns {Array}
         */
        function generatePagesArray(currentPage, collectionLength, rowsPerPage, paginationRange) {
            var pages = [];
            var totalPages = Math.ceil(collectionLength / rowsPerPage);
            var halfWay = Math.ceil(paginationRange / 2);
            var position;

            if (currentPage <= halfWay) {
                position = 'start';
            } else if (totalPages - halfWay < currentPage) {
                position = 'end';
            } else {
                position = 'middle';
            }

            var ellipsesNeeded = paginationRange < totalPages;
            var i = 1;
            while (i <= totalPages && i <= paginationRange) {
                var pageNumber = calculatePageNumber(i, currentPage, paginationRange, totalPages);

                var openingEllipsesNeeded = (i === 2 && (position === 'middle' || position === 'end'));
                var closingEllipsesNeeded = (i === paginationRange - 1 && (position === 'middle' || position === 'start'));
                if (ellipsesNeeded && (openingEllipsesNeeded || closingEllipsesNeeded)) {
                    pages.push('...');
                } else {
                    pages.push(pageNumber);
                }
                i ++;
            }
            return pages;
        }

        /**
         * Given the position in the sequence of pagination links [i], figure out what page number corresponds to that position.
         *
         * @param i
         * @param currentPage
         * @param paginationRange
         * @param totalPages
         * @returns {*}
         */
        function calculatePageNumber(i, currentPage, paginationRange, totalPages) {
            var halfWay = Math.ceil(paginationRange/2);
            if (i === paginationRange) {
                return totalPages;
            } else if (i === 1) {
                return i;
            } else if (paginationRange < totalPages) {
                if (totalPages - halfWay < currentPage) {
                    return totalPages - paginationRange + i;
                } else if (halfWay < currentPage) {
                    return currentPage - halfWay + i;
                } else {
                    return i;
                }
            } else {
                return i;
            }
        }
    }

    /**
     * This filter slices the collection into pages based on the current page number and number of items per page.
     * @param paginationService
     * @returns {Function}
     */
    function itemsPerPageFilter(paginationService) {

        return function(collection, itemsPerPage, paginationId) {
            if (typeof (paginationId) === 'undefined') {
                paginationId = DEFAULT_ID;
            }
            if (!paginationService.isRegistered(paginationId)) {
                throw 'pagination directive: the itemsPerPage id argument (id: ' + paginationId + ') does not match a registered pagination-id.';
            }
            var end;
            var start;
            if (collection instanceof Array) {
                itemsPerPage = parseInt(itemsPerPage) || 9999999999;
                if (paginationService.isAsyncMode(paginationId)) {
                    start = 0;
                } else {
                    start = (paginationService.getCurrentPage(paginationId) - 1) * itemsPerPage;
                }
                end = start + itemsPerPage;
                paginationService.setItemsPerPage(paginationId, itemsPerPage);

                return collection.slice(start, end);
            } else {
                return collection;
            }
        };
    }

    /**
     * This service allows the various parts of the module to communicate and stay in sync.
     */
    function paginationService() {

        var instances = {};
        var lastRegisteredInstance;

        this.registerInstance = function(instanceId) {
            if (typeof instances[instanceId] === 'undefined') {
                instances[instanceId] = {
                    asyncMode: false
                };
                lastRegisteredInstance = instanceId;
            }
        };

        this.isRegistered = function(instanceId) {
            return (typeof instances[instanceId] !== 'undefined');
        };

        this.getLastInstanceId = function() {
            return lastRegisteredInstance;
        };

        this.setCurrentPageParser = function(instanceId, val, scope) {
            instances[instanceId].currentPageParser = val;
            instances[instanceId].context = scope;
        };
        this.setCurrentPage = function(instanceId, val) {
            instances[instanceId].currentPageParser.assign(instances[instanceId].context, val);
        };
        this.getCurrentPage = function(instanceId) {
            var parser = instances[instanceId].currentPageParser;
            return parser ? parser(instances[instanceId].context) : 1;
        };

        this.setItemsPerPage = function(instanceId, val) {
            instances[instanceId].itemsPerPage = val;
        };
        this.getItemsPerPage = function(instanceId) {
            return instances[instanceId].itemsPerPage;
        };

        this.setCollectionLength = function(instanceId, val) {
            instances[instanceId].collectionLength = val;
        };
        this.getCollectionLength = function(instanceId) {
            return instances[instanceId].collectionLength;
        };

        this.setAsyncModeTrue = function(instanceId) {
            instances[instanceId].asyncMode = true;
        };

        this.isAsyncMode = function(instanceId) {
            return instances[instanceId].asyncMode;
        };
    }

    /**
     * This provider allows global configuration of the template path used by the dir-pagination-controls directive.
     */
    function paginationTemplateProvider() {

        var templatePath = 'angularUtils.directives.dirPagination.template';

        this.setPath = function(path) {
            templatePath = path;
        };

        this.$get = function() {
            return {
                getPath: function() {
                    return templatePath;
                }
            };
        };
    }
})();