// Variablen für hochgeladene Bilder und deren Position
let uploadedImage = null;
let uploadedLogo = null;
let imageOffsetX = 0;
let imageOffsetY = 0;
let isDragging = false;
let dragStartX = 0;
let dragStartY = 0;

// Standardwerte für Bild, Logo und Texte
const defaultImage = 'assets/images/defaultBackground.jpg';
const defaultLogo = 'assets/images/defaultLogo.svg';
const defaultHeadline = 'iFSR sharepic Headline';
const defaultSubline = 'Hier könnte ein unfassbar fesselnder Werbetext des Fachschaftsrats Informatik stehen.';

// Initialisierung beim Laden der Seite
window.onload = function () {
    document.getElementById('headline').value = defaultHeadline;
    document.getElementById('subline').value = defaultSubline;

    loadDefaultImage();
    loadDefaultLogo();
    generateSharepic();
};

// Lädt das Standardhintergrundbild
function loadDefaultImage() {
    uploadedImage = new Image();
    uploadedImage.onload = drawCanvas;
    uploadedImage.src = defaultImage;
}

// Lädt das Standardlogo
function loadDefaultLogo() {
    uploadedLogo = new Image();
    uploadedLogo.onload = drawCanvas;
    uploadedLogo.src = defaultLogo;
}

// Event-Listener für Datei-Uploads und Eingaben
document.getElementById('imageUpload').addEventListener('change', handleImageUpload);
document.getElementById('logoUpload').addEventListener('change', handleLogoUpload);
document.getElementById('headline').addEventListener('input', generateSharepic);
document.getElementById('subline').addEventListener('input', generateSharepic);
document.getElementById('fontSize').addEventListener('input', generateSharepic);
document.getElementById('boxHeight').addEventListener('input', generateSharepic);
document.getElementById('logoSize').addEventListener('input', generateSharepic);
document.getElementById('logoLeft').addEventListener('change', generateSharepic);

// Verarbeitet den Upload eines neuen Hintergrundbildes
function handleImageUpload(event) {
    const file = event.target.files[0];
    if (file) {
        const imageUrl = URL.createObjectURL(file);
        uploadedImage = new Image();
        uploadedImage.onload = function () {
            imageOffsetX = 0;
            imageOffsetY = 0;
            drawCanvas();
        };
        uploadedImage.src = imageUrl;
    }
}

// Verarbeitet den Upload eines neuen Logos
function handleLogoUpload(event) {
    const file = event.target.files[0];
    if (file) {
        const logoUrl = URL.createObjectURL(file);
        uploadedLogo = new Image();
        uploadedLogo.onload = drawCanvas;
        uploadedLogo.src = logoUrl;
    }
}

// Generiert das Sharepic neu
function generateSharepic() {
    drawCanvas();
}

// Berechnet die Bildgröße passend zur Canvas-Größe
function calculateImageDimensions(image, canvas) {
    let imageWidth, imageHeight;

    if (image.width > image.height) {
        imageHeight = canvas.height;
        imageWidth = image.width * (imageHeight / image.height);
    } else {
        imageWidth = canvas.width;
        imageHeight = image.height * (imageWidth / image.width);
    }

    return { width: imageWidth, height: imageHeight };
}

// Zeichnet das Canvas mit Bild, Logo und Text
function drawCanvas() {
    const canvas = document.getElementById('canvas');
    const ctx = canvas.getContext('2d');

    canvas.width = 1080;
    canvas.height = 1080;

    // Zeichnet das hochgeladene Hintergrundbild
    if (uploadedImage) {
        const { width, height } = calculateImageDimensions(uploadedImage, canvas);
        ctx.drawImage(uploadedImage, imageOffsetX, imageOffsetY, width, height);
    }

    // Zeichnet das weiße Textfeld
    const boxHeight = parseInt(document.getElementById('boxHeight').value);
    const boxPadding = 20;
    ctx.fillStyle = 'white';
    ctx.fillRect(boxPadding, canvas.height - boxHeight - boxPadding, canvas.width - 2 * boxPadding, boxHeight);

    // Holt die Texteingaben
    const headline = document.getElementById('headline').value;
    const subline = document.getElementById('subline').value;
    const fontSize = parseInt(document.getElementById('fontSize').value);

    // Setzt Schriftfarbe
    ctx.fillStyle = 'black';

    const headlineFont = `bold ${fontSize * 1.2}px 'Cairo', sans-serif`;
    const sublineFont = `${fontSize}px 'Cairo', sans-serif`;
    const maxWidth = canvas.width - 2 * boxPadding - 40;

    // Funktion zum Umbruch langer Texte
    function wrapText(ctx, text, x, y, maxWidth, font) {
        ctx.font = font;
        const lineHeight = parseInt(font.match(/\d+/)[0]) * 1.2;

        const words = text.split(' ');
        let line = '';
        let lines = [];

        for (let n = 0; n < words.length; n++) {
            let testLine = line + words[n] + ' ';
            let testWidth = ctx.measureText(testLine).width;

            if (testWidth > maxWidth && n > 0) {
                lines.push(line);
                line = words[n] + ' ';
            } else {
                line = testLine;
            }
        }
        lines.push(line);

        lines.forEach((line, i) => ctx.fillText(line, x, y + i * lineHeight));
    }

    // Zeichnet Headline und Subline ins Canvas
    wrapText(ctx, headline, boxPadding + 20, canvas.height - boxHeight - boxPadding + 80, maxWidth, headlineFont);
    wrapText(ctx, subline, boxPadding + 20, canvas.height - boxHeight - boxPadding + 150, maxWidth, sublineFont);

    // Zeichnet das Logo
    if (uploadedLogo) {
        const logoSize = parseInt(document.getElementById('logoSize').value);
        const logoRatio = uploadedLogo.width / uploadedLogo.height;
        let logoWidth = logoSize * logoRatio;
        let logoHeight = logoSize;

        if (logoWidth > canvas.width - 40) {
            logoWidth = canvas.width - 40;
            logoHeight = logoWidth / logoRatio;
        }

        const logoLeft = document.getElementById('logoLeft').checked;
        const logoX = logoLeft ? 20 : canvas.width - logoWidth - 20;

        ctx.drawImage(uploadedLogo, logoX, 20, logoWidth, logoHeight);
    }
}

// Bild-Drag-Funktionalität
const canvas = document.getElementById('canvas');
canvas.addEventListener('mousedown', function (e) {
    if (uploadedImage) {
        isDragging = true;
        dragStartX = e.offsetX - imageOffsetX;
        dragStartY = e.offsetY - imageOffsetY;
    }
});

canvas.addEventListener('mousemove', function (e) {
    if (isDragging && uploadedImage) {
        const { width, height } = calculateImageDimensions(uploadedImage, canvas);

        if (uploadedImage.width > uploadedImage.height) {
            imageOffsetX = e.offsetX - dragStartX;
            imageOffsetX = Math.min(0, Math.max(imageOffsetX, canvas.width - width));
        } else {
            imageOffsetY = e.offsetY - dragStartY;
            imageOffsetY = Math.min(0, Math.max(imageOffsetY, canvas.height - height));
        }
        drawCanvas();
    }
});

canvas.addEventListener('mouseup', () => isDragging = false);
canvas.addEventListener('mouseout', () => isDragging = false);

// Download-Button für das Sharepic
document.getElementById('downloadBtn').addEventListener('click', function (event) {
    event.preventDefault();

    const dataUrl = canvas.toDataURL('image/png');
    const a = document.createElement('a');
    a.href = dataUrl;
    a.download = 'sharepic.png';
    document.body.appendChild(a);
    a.click();
    document.body.removeChild(a);
});