(function($) {
    "use strict";

    if (typeof window.initEbookModule === 'function') {
        return;
    }

    window.initEbookModule = function(moduleId, pdfUrl, config) {
        var $module = $('#' + moduleId);
        if (!$module.length || !pdfUrl) return;

        var pdfDoc = null;
        var pageCount = 0;
        var currentScale = 1.0;
        var initialLoadCount = 6;
        var isInitialized = false;
        var loadedPageCount = 0;
        var renderedCount = 0;

        var $flipbook = $module.find('.flipbook');
        var $loadingOverlay = $module.find('.ebook-loading-overlay');
        var $loadingText = $module.find('.loading-text');
        var $viewport = $module.find('.flipbook-viewport');
        var $controls = $module.find('.ebook-controls');
        var $totalPages = $module.find('.total-pages');
        var $loadedPages = $module.find('.loaded-pages');
        var $pageInput = $module.find('.page-input');
        var $totalPagesWrap = $module.find('.total-pages-wrap');
        var $alertMsg = $module.find('.page-loading-alert');

        function startEbookProcess() {
            if ($flipbook.turn('is')) {
                $flipbook.turn('destroy');
            }
            $flipbook.empty();
            $loadingOverlay.show();
            $viewport.add($controls).addClass('loading');

            var availableWidth = $viewport.width() || config.width || 922;
            var availableHeight = $viewport.height() || config.height || 600;
            
            var bookWidth, bookHeight;

            function renderAllPages(pdf) {
                pdfDoc = pdf;
                pageCount = pdf.numPages;
                $totalPages.text(pageCount);
                $pageInput.attr('max', pageCount);

                pdf.getPage(1).then(function(page) {
                    var viewport = page.getViewport({ scale: 1 });
                    var pageRatio = viewport.width / viewport.height;
                    var bookRatio = pageRatio * 2;

                    bookWidth = availableWidth;
                    bookHeight = bookWidth / bookRatio;

                    if (bookHeight > availableHeight) {
                        bookHeight = availableHeight;
                        bookWidth = bookHeight * bookRatio;
                    }

                    var initialPromises = [];
                    var loadLimit = Math.min(pageCount, initialLoadCount);

                    for (var i = 1; i <= loadLimit; i++) {
                        initialPromises.push(renderPage(i, bookWidth, bookHeight, true, loadLimit));
                    }

                    Promise.all(initialPromises).then(function(pages) {
                        pages.forEach(function(pageDiv) {
                            $flipbook.append(pageDiv);
                        });

                        initTurnJs(bookWidth, bookHeight);
                        isInitialized = true;
                        loadedPageCount = loadLimit;
                        updatePageDisplay();
                        
                        $loadingOverlay.fadeOut(500);
                        $viewport.add($controls).removeClass('loading');

                        if (pageCount > initialLoadCount) {
                            loadRemainingPages(initialLoadCount + 1, bookWidth, bookHeight);
                        } else {
                            updatePageDisplay(true);
                        }
                    });
                });
            }

            if (pdfDoc) {
                run(pdfDoc);
            } else {
                pdfjsLib.getDocument(pdfUrl).promise.then(renderAllPages);
            }
        }

        function loadRemainingPages(pageNum, bookWidth, bookHeight) {
            if (pageNum > pageCount) {
                updatePageDisplay(true);
                return;
            }
            renderPage(pageNum, bookWidth, bookHeight, false).then(function(pageDiv) {
                if ($flipbook.turn('is')) {
                    $flipbook.turn('addPage', pageDiv, pageNum);
                }
                loadedPageCount = pageNum;
                updatePageDisplay();
                loadRemainingPages(pageNum + 1, bookWidth, bookHeight);
            });
        }

        function updatePageDisplay(isComplete = false) {
            if (isComplete) {
                $totalPagesWrap.hide();
                $loadedPages.text(pageCount);
            } else {
                $loadedPages.text(loadedPageCount);
                $totalPagesWrap.show();
            }
        }

        function renderPage(num, bookWidth, bookHeight, isInitial, loadLimit) {
            return pdfDoc.getPage(num).then(function(page) {
                var viewport = page.getViewport({ scale: 1.5 });
                var canvas = document.createElement('canvas');
                var ctx = canvas.getContext('2d');
                
                var pageWidth = bookWidth / 2;
                var pageHeight = bookHeight;
                var scaleX = pageWidth / viewport.width;
                var scaleY = pageHeight / viewport.height;
                var fitScale = Math.max(scaleX, scaleY);
                var fitViewport = page.getViewport({ scale: fitScale });

                canvas.height = pageHeight;
                canvas.width = pageWidth;

                var pageDiv = $('<div />').append(canvas);
                
                var renderContext = { canvasContext: ctx, viewport: fitViewport };
                
                return page.render(renderContext).promise.then(function() {
                    if (isInitial) {
                        renderedCount++;
                        var percent = Math.round((renderedCount / loadLimit) * 100);
                        $loadingText.text('Loading... (' + percent + '%)');
                    }
                    return pageDiv;
                });
            });
        }

        function initTurnJs(bookWidth, bookHeight) {
            if (typeof $flipbook.turn !== 'function') return;
            if ($flipbook.turn('is')) $flipbook.turn('destroy');

            $flipbook.turn({
                width: bookWidth,
                height: bookHeight,
                autoCenter: true,
                gradients: true,
                acceleration: true,
                elevation: 50,
                display: 'double',
                pages: pageCount,
                when: {
                    turned: function(event, page, view) {
                        $pageInput.val(page);
                    }
                }
            });
        }

        startEbookProcess();

        // 이벤트 핸들러 (한 번만 등록)
        $module.find('#prev-btn, .nav-prev').off().on('click', function() { $flipbook.turn('previous'); });
        $module.find('#next-btn, .nav-next').off().on('click', function() { $flipbook.turn('next'); });
        $pageInput.off().on('change keyup', function(e) {
            if (e.type === 'keyup' && e.keyCode !== 13) return;
            var page = parseInt($(this).val());
            if (page > 0 && page <= pageCount) $flipbook.turn('page', page);
        });
        function updateZoom() {
            $viewport.css('transform', 'scale(' + currentScale + ')');
            $module.find('.zoom-level').text(Math.round(currentScale * 100) + '%');
        }
        $module.find('#zoom-in-btn').off().on('click', function() { if (currentScale < 2.0) { currentScale += 0.2; updateZoom(); } });
        $module.find('#zoom-out-btn').off().on('click', function() { if (currentScale > 0.6) { currentScale -= 0.2; updateZoom(); } });
        $module.find('#zoom-reset-btn').off().on('click', function() { currentScale = 1.0; updateZoom(); });
        $module.find('#dark-mode-btn').off().on('click', function() {
            var currentTheme = $module.attr('data-theme');
            var newTheme = currentTheme === 'light' ? 'dark' : 'light';
            $module.attr('data-theme', newTheme);
            $(this).find('i').toggleClass('fa-sun fa-moon');
        });
        $module.find('#print-btn').off().on('click', function() {
            var $iframe = $module.find('iframe');
            $iframe.attr('src', pdfUrl);
            $iframe.on('load', function() {
                try { this.contentWindow.print(); } 
                catch (e) { window.open(pdfUrl, '_blank').print(); }
            });
        });
    };
})(jQuery);