// PDF.js Viewer for Blazor WASM
window.pdfViewer = {
    pdfDoc: null,
    pageNum: 1,
    pageRendering: false,
    pageNumPending: null,
    scale: 1.5,
    canvas: null,
    ctx: null,
    totalPages: 0,

    async initialize(canvasId, pdfDataUrl) {
        try {
            console.log('PDF.js initialization started for canvas:', canvasId);

            // Wait for PDF.js to load
            if (typeof window.pdfjsLib === 'undefined') {
                console.error('PDF.js library not loaded, waiting...');
                await this.waitForPdfJs();
            }

            const pdfjsLib = window.pdfjsLib;
            pdfjsLib.GlobalWorkerOptions.workerSrc = 'https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.worker.min.js';

            this.canvas = document.getElementById(canvasId);
            if (!this.canvas) {
                console.error('Canvas element not found:', canvasId);
                return false;
            }

            console.log('Canvas element found, loading PDF...');

            this.ctx = this.canvas.getContext('2d');

            // Load PDF from data URL
            const uint8Array = this.base64ToUint8Array(pdfDataUrl);
            console.log('PDF data converted to Uint8Array, size:', uint8Array.length);

            const loadingTask = pdfjsLib.getDocument({ data: uint8Array });
            this.pdfDoc = await loadingTask.promise;
            this.totalPages = this.pdfDoc.numPages;

            console.log('PDF loaded successfully, total pages:', this.totalPages);

            // Render first page
            await this.renderPage(this.pageNum);
            return true;
        } catch (error) {
            console.error('Error initializing PDF viewer:', error);
            return false;
        }
    },

    async waitForPdfJs() {
        for (let i = 0; i < 50; i++) {
            if (typeof window.pdfjsLib !== 'undefined') {
                console.log('PDF.js loaded after', i * 100, 'ms');
                return;
            }
            await new Promise(resolve => setTimeout(resolve, 100));
        }
        throw new Error('PDF.js failed to load after 5 seconds');
    },

    base64ToUint8Array(base64) {
        // Remove data URL prefix if present
        const base64String = base64.includes(',') ? base64.split(',')[1] : base64;
        const raw = atob(base64String);
        const uint8Array = new Uint8Array(raw.length);
        for (let i = 0; i < raw.length; i++) {
            uint8Array[i] = raw.charCodeAt(i);
        }
        return uint8Array;
    },

    async renderPage(num) {
        this.pageRendering = true;

        try {
            const page = await this.pdfDoc.getPage(num);
            const viewport = page.getViewport({ scale: this.scale });

            console.log('Rendering page:', num, 'Viewport:', viewport.width, 'x', viewport.height);

            this.canvas.height = viewport.height;
            this.canvas.width = viewport.width;

            const renderContext = {
                canvasContext: this.ctx,
                viewport: viewport
            };

            await page.render(renderContext).promise;

            console.log('Page rendered successfully');

            this.pageRendering = false;

            if (this.pageNumPending !== null) {
                this.renderPage(this.pageNumPending);
                this.pageNumPending = null;
            }
        } catch (error) {
            console.error('Error rendering page:', error);
            this.pageRendering = false;
        }
    },

    queueRenderPage(num) {
        if (this.pageRendering) {
            this.pageNumPending = num;
        } else {
            this.renderPage(num);
        }
    },

    nextPage() {
        if (this.pageNum >= this.totalPages) {
            return false;
        }
        this.pageNum++;
        this.queueRenderPage(this.pageNum);
        return true;
    },

    previousPage() {
        if (this.pageNum <= 1) {
            return false;
        }
        this.pageNum--;
        this.queueRenderPage(this.pageNum);
        return true;
    },

    goToPage(num) {
        if (num < 1 || num > this.totalPages) {
            return false;
        }
        this.pageNum = num;
        this.queueRenderPage(this.pageNum);
        return true;
    },

    zoomIn() {
        this.scale += 0.25;
        this.queueRenderPage(this.pageNum);
    },

    zoomOut() {
        if (this.scale > 0.5) {
            this.scale -= 0.25;
            this.queueRenderPage(this.pageNum);
        }
    },

    getCurrentPage() {
        return this.pageNum;
    },

    getTotalPages() {
        return this.totalPages;
    },

    getScale() {
        return this.scale;
    }
};