parsing refactor

texture.js

@@ -0,0 +1,80 @@
+export class TextureHandler {
+    constructor(size) {
+        this.canvas = document.createElement('canvas');
+        this.canvas.width = size;
+        this.canvas.height = size;
+        this.ctx = this.canvas.getContext('2d', {willReadFrequently: true});
+        this.ctx.imageSmoothingEnabled = false;
+
+        this.uvmap = new Map();
+        this.pendingDraws = new Map();
+
+        this.cellSize = 16;
+        this.padding = 1;
+        this.x = 0;
+        this.y = 0;
+        this.rowHeight = 0;
+    }
+
+    prepare(cache, id, url) {
+        if (this.x + this.cellSize > this.canvas.width) {
+            this.x = 0;
+            this.y += this.rowHeight + this.padding;
+            this.rowHeight = 0;
+        }
+
+        const currentX = this.x;
+        const currentY = this.y;
+
+        this.x += this.cellSize + this.padding;
+        this.rowHeight = Math.max(this.rowHeight, this.cellSize);
+
+        const uvData = {
+            u: currentX / this.canvas.width,
+            v: currentY / this.canvas.height,
+            du: this.cellSize / this.canvas.width,
+            dv: this.cellSize / this.canvas.height,
+        };
+
+        this.uvmap.set(id, uvData);
+        this.pendingDraws.set(id, {x: currentX, y: currentY});
+    }
+
+    async process(cache, id, url) {
+        const pos = this.pendingDraws.get(id);
+        if (!pos) throw new Error(`Not prepared for ${id}.`);
+        this.pendingDraws.delete(id);
+
+        const drawMissing = () => {
+            const half = this.cellSize / 2;
+            this.ctx.fillStyle = '#ff00ff'; // Magenta
+            this.ctx.fillRect(pos.x, pos.y, half, half);
+            this.ctx.fillRect(pos.x + half, pos.y + half, half, half);
+            this.ctx.fillStyle = '#000000'; // Black
+            this.ctx.fillRect(pos.x + half, pos.y, half, half);
+            this.ctx.fillRect(pos.x, pos.y + half, half, half);
+        };
+
+        // Short circuit to avoid unnecessary network requests for known missing ids
+        if (id === ':missing') {
+            drawMissing();
+            return this.uvmap.get(id);
+        }
+
+        try {
+            const img = await new Promise((resolve, reject) => {
+                const i = new Image();
+                i.crossOrigin = 'anonymous';
+                i.onload = () => resolve(i);
+                i.onerror = () => reject(new Error(`Image load failed`));
+                i.src = url + '.png';
+            });
+            this.ctx.drawImage(img, pos.x, pos.y, this.cellSize, this.cellSize);
+        } catch (e) {
+            console.warn(`Missing texture: ${id}`);
+            drawMissing();
+        }
+
+        return this.uvmap.get(id);
+    }
+}