feat: separate frontend and backend services

server/src/lib/image-attachments.ts

@@ -0,0 +1,121 @@
+/// <reference lib="dom" />
+// compressImageFile below is browser-only (canvas/ImageBitmap) and never runs
+// here; the dom reference lets this file stay a verbatim copy of the pi-web
+// module without adding "dom" to the whole server program.
+export const MAX_ATTACHED_IMAGE_BYTES = 10 * 1024 * 1024;
+export const MAX_ATTACHED_IMAGES = 10;
+
+/** 上传时自动压缩：长边超过此像素的 JPEG 缩到此边长（相机照片主场景，视觉模型输入上限 ~1344px，1600 无损）。 */
+export const MAX_IMAGE_EDGE_PX = 1600;
+/** JPEG 重编码质量：避免伪影糊掉边缘/小字。 */
+export const IMAGE_JPEG_QUALITY = 0.85;
+
+export interface Base64ImageAttachment {
+	data: string;
+	mimeType: string;
+}
+
+function isBase64DataChar(code: number): boolean {
+	return (
+		(code >= 0x41 && code <= 0x5a) ||
+		(code >= 0x61 && code <= 0x7a) ||
+		(code >= 0x30 && code <= 0x39) ||
+		code === 0x2b ||
+		code === 0x2f
+	);
+}
+
+export function getBase64DecodedByteLength(data: string): number | null {
+	if (!data || data.length % 4 !== 0) return null;
+	const padding = data.endsWith("==") ? 2 : data.endsWith("=") ? 1 : 0;
+	const dataEnd = data.length - padding;
+	for (let index = 0; index < dataEnd; index += 1) {
+		if (!isBase64DataChar(data.charCodeAt(index))) return null;
+	}
+	for (let index = dataEnd; index < data.length; index += 1) {
+		if (data[index] !== "=") return null;
+	}
+	return (data.length / 4) * 3 - padding;
+}
+
+export function isBase64ImageWithinLimits(
+	value: unknown,
+): value is Base64ImageAttachment {
+	if (!value || typeof value !== "object") return false;
+	const image = value as Partial<Base64ImageAttachment>;
+	if (
+		typeof image.data !== "string" ||
+		typeof image.mimeType !== "string" ||
+		!image.mimeType.startsWith("image/")
+	) {
+		return false;
+	}
+	const bytes = getBase64DecodedByteLength(image.data);
+	return bytes !== null && bytes <= MAX_ATTACHED_IMAGE_BYTES;
+}
+
+/**
+ * 上传前压缩：JPEG 和 PNG 且长边超过 MAX_IMAGE_EDGE_PX 时缩放并统一转 JPEG。
+ * PNG 截图（代码编辑器/UI）通常无透明通道，转 JPEG 体积大幅减小。
+ * WebP/GIF 原样返回（WebP 已经高效；GIF 可能是动画）。
+ * 重编码无收益（更小或失败）时退回原文件。
+ */
+export async function compressImageFile(file: File): Promise<File> {
+	// 仅压缩 JPEG 和 PNG（最常见的截图/照片格式）
+	if (
+		!file.type ||
+		!(file.type.startsWith("image/jpeg") || file.type.startsWith("image/png"))
+	) {
+		return file;
+	}
+	let bitmap: ImageBitmap;
+	try {
+		bitmap = await createImageBitmap(file);
+	} catch {
+		return file; // 解码失败退化为原文件
+	}
+	try {
+		const edge = Math.max(bitmap.width, bitmap.height);
+		if (edge <= MAX_IMAGE_EDGE_PX) return file; // 本就不大，避免无谓重编码
+		const scale = MAX_IMAGE_EDGE_PX / edge;
+		const width = Math.max(1, Math.round(bitmap.width * scale));
+		const height = Math.max(1, Math.round(bitmap.height * scale));
+		const canvas = document.createElement("canvas");
+		canvas.width = width;
+		canvas.height = height;
+		const ctx = canvas.getContext("2d");
+		if (!ctx) return file;
+		ctx.drawImage(bitmap, 0, 0, width, height);
+		const blob = await new Promise<Blob | null>((resolve) =>
+			canvas.toBlob(resolve, "image/jpeg", IMAGE_JPEG_QUALITY),
+		);
+		if (!blob || blob.size >= file.size) return file; // 重编码无收益则用原文件
+		return new File([blob], file.name.replace(/\.\w+$/, ".jpg"), {
+			type: "image/jpeg",
+		});
+	} finally {
+		bitmap.close();
+	}
+}
+
+/** Return an API-safe error for prompt, steering, and follow-up image arrays. */
+export function validateAgentImages(value: unknown): string | null {
+	if (value === undefined) return null;
+	if (!Array.isArray(value)) return "images must be an array";
+	if (value.length > MAX_ATTACHED_IMAGES) {
+		return `A message can include at most ${MAX_ATTACHED_IMAGES} images`;
+	}
+	for (const image of value) {
+		if (
+			!image ||
+			typeof image !== "object" ||
+			(image as { type?: unknown }).type !== "image"
+		) {
+			return "Each attachment must be an image";
+		}
+		if (!isBase64ImageWithinLimits(image)) {
+			return `Each image must be valid base64 image data of ${MAX_ATTACHED_IMAGE_BYTES / (1024 * 1024)}MB or smaller`;
+		}
+	}
+	return null;
+}