digicraft-be/services/stickerSheetService.ts

import sharp from 'sharp';
import path from 'path';
import fs from 'fs';
import { v4 as uuidv4 } from 'uuid';

// Paper Dimensions (at 300 DPI)
const PAPER_SIZES: Record<string, { width: number, height: number }> = {
    'A4': { width: 2480, height: 3508 }, // 210mm x 297mm
    'Letter': { width: 2550, height: 3300 }, // 8.5in x 11in
    'A5': { width: 1748, height: 2480 } // 148mm x 210mm
};

export const stickerSheetService = {

    /**
     * Add a white border and optional cut line to an image.
     * @param inputPath Path to the source image (sticker).
     * @param borderWidth Width of the white contour in pixels (default 40).
     */
    async addCutContour(inputPath: string, borderWidth: number = 40): Promise<Buffer> {
        // 1. Load Image
        const image = sharp(inputPath);
        const metadata = await image.metadata();
        if (!metadata.width || !metadata.height) throw new Error("Invalid image metadata");

        // 2. Create Mask (Alpha Channel)
        const alpha = await image.clone()
            .toColourspace('b-w')
            .ensureAlpha()
            .extractChannel(3) // Get alpha channel
            .raw()
            .toBuffer();

        // 3. Dilate Mask to create Border Shape
        // Proper dilation requires morphological operations which Sharp doesn't support natively well for complex shapes without external libs.
        // TRICK: We will blur the alpha channel and threshold it to simulate dilation/expansion.
        const expandedMask = await sharp(alpha, { raw: { width: metadata.width, height: metadata.height, channels: 1 } })
            .blur(borderWidth) // Spread the alpha
            .threshold(10)     // Binarize to create hard edge
            .toBuffer();

        // 4. Create White Silhouette using the expanded mask
        const whiteBackground = await sharp({
            create: {
                width: metadata.width,
                height: metadata.height,
                channels: 4,
                background: { r: 255, g: 255, b: 255, alpha: 1 }
            }
        })
            .joinChannel(expandedMask) // Apply mask
            .png()
            .toBuffer();

        // 5. Composite Original Image ON TOP of White Silhouette
        return sharp(whiteBackground)
            .composite([{ input: inputPath }])
            .withMetadata({ density: 300 }) // Enforce 300 DPI
            .png()
            .toBuffer();
    },

    /**
     * Generate a BLACKOUT mask for Cricut Cut Lines.
     * Returns a binary verification image (Black shape on transparent background).
     */
    async generateCutMask(inputPath: string, borderWidth: number = 40): Promise<Buffer> {
        // 1. Load Image
        const image = sharp(inputPath);
        const metadata = await image.metadata();
        if (!metadata.width || !metadata.height) throw new Error("Invalid image metadata");

        // 2. Extract Alpha
        const alpha = await image.clone()
            .toColourspace('b-w')
            .ensureAlpha()
            .extractChannel(3)
            .raw()
            .toBuffer();

        // 3. Dilate (Same logic as addCutContour to match perfectly)
        const expandedMask = await sharp(alpha, { raw: { width: metadata.width, height: metadata.height, channels: 1 } })
            .blur(borderWidth)
            .threshold(10)
            .toBuffer();

        // 4. Create BLACK Silhouette
        return sharp({
            create: {
                width: metadata.width,
                height: metadata.height,
                channels: 4,
                background: { r: 0, g: 0, b: 0, alpha: 1 } // BLACK
            }
        })
            .joinChannel(expandedMask) // Apply same mask
            .withMetadata({ density: 300 }) // Enforce 300 DPI
            .png()
            .toBuffer();
    },

    /**
     * Arrange multiple stickers onto a single sheet.
     * @param stickerPaths Array of absolute paths to sticker images.
     * @param options Configuration for the sheet (target dimensions, paper size name)
     */
    async generateSheet(stickerPaths: string[], options: { width: number, height: number, paperSizeName?: string }): Promise<Buffer> {
        const { width, height } = options;

        // Target 4-5 columns for A4/Letter at 2500px width.
        // If width is ~5000px (High Res A4), we still want ~4-5 columns? 
        // Or do we want more stickers if we have them?
        // Usually a sticker sheet has a fixed number of stickers. 
        // Let's assume we want a standard grid. 
        // Let's base sticker size on WIDTH.
        // 4 cols + 5 gaps = width.
        // stickerW * 4 + gap * 5 = width.
        // let gap = stickerW / 10.
        // stickerW * 4 + stickerW/2 = width => 4.5 stickerW = width.

        const COLS = 4;
        // Calculation:
        // Width = COLS * StickerW + (COLS + 1) * GAP
        // Let GAP = StickerW * 0.1
        // Width = 4 * S + 5 * 0.1 * S = 4.5 S
        const stickerWidth = Math.floor(width / (COLS + (COLS + 1) * 0.1));
        const gap = Math.floor(stickerWidth * 0.1);

        console.log(`[StickerService] Generating Sheet ${width}x${height}. Sticker W: ${stickerWidth}, Gap: ${gap}`);

        const composites: sharp.OverlayOptions[] = [];

        let currentX = gap;
        let currentY = gap;
        let maxHeightInRow = 0;

        for (const stickerPath of stickerPaths) {
            let stickerBuffer;
            try {
                stickerBuffer = await this.addCutContour(stickerPath, Math.floor(stickerWidth * 0.05)); // Scale border too
            } catch (e) {
                console.error(`Failed to process sticker ${stickerPath}`, e);
                continue;
            }

            // Resize to target width
            const resizedSticker = await sharp(stickerBuffer)
                .resize({ width: stickerWidth })
                .toBuffer();

            const meta = await sharp(resizedSticker).metadata();
            const w = meta.width || stickerWidth;
            const h = meta.height || stickerWidth;

            // Check if fits in current row
            if (currentX + w + gap > width) {
                // Next Row
                currentX = gap;
                currentY += maxHeightInRow + gap;
                maxHeightInRow = 0;
            }

            // Check if fits in page (vertical)
            if (currentY + h + gap > height) {
                console.warn("Sheet full, skipping remaining stickers");
                break;
            }

            composites.push({
                input: resizedSticker,
                top: currentY,
                left: currentX
            });

            currentX += w + gap;
            if (h > maxHeightInRow) maxHeightInRow = h;
        }

        // Create Sheet Canvas
        return sharp({
            create: {
                width: width,
                height: height,
                channels: 4,
                background: { r: 255, g: 255, b: 255, alpha: 0 } // Transparent
            }
        })
            .composite(composites)
            .png()
            .toBuffer();
    }
};