57 lines
1.7 KiB
TypeScript
57 lines
1.7 KiB
TypeScript
export type ChatAttachment = {
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type?: string;
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mimeType?: string;
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fileName?: string;
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content?: unknown;
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};
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export function buildMessageWithAttachments(
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message: string,
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attachments: ChatAttachment[] | undefined,
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opts?: { maxBytes?: number },
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): string {
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const maxBytes = opts?.maxBytes ?? 2_000_000; // 2 MB
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if (!attachments || attachments.length === 0) return message;
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const blocks: string[] = [];
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for (const [idx, att] of attachments.entries()) {
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if (!att) continue;
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const mime = att.mimeType ?? "";
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const content = att.content;
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const label = att.fileName || att.type || `attachment-${idx + 1}`;
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if (typeof content !== "string") {
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throw new Error(`attachment ${label}: content must be base64 string`);
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}
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if (!mime.startsWith("image/")) {
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throw new Error(`attachment ${label}: only image/* supported`);
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}
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let sizeBytes = 0;
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const b64 = content.trim();
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// Basic base64 sanity: length multiple of 4 and charset check.
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if (b64.length % 4 !== 0 || /[^A-Za-z0-9+/=]/.test(b64)) {
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throw new Error(`attachment ${label}: invalid base64 content`);
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}
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try {
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sizeBytes = Buffer.from(b64, "base64").byteLength;
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} catch {
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throw new Error(`attachment ${label}: invalid base64 content`);
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}
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if (sizeBytes <= 0 || sizeBytes > maxBytes) {
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throw new Error(
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`attachment ${label}: exceeds size limit (${sizeBytes} > ${maxBytes} bytes)`,
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);
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}
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const safeLabel = label.replace(/\s+/g, "_");
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const dataUrl = ``;
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blocks.push(dataUrl);
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}
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if (blocks.length === 0) return message;
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const separator = message.trim().length > 0 ? "\n\n" : "";
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return `${message}${separator}${blocks.join("\n\n")}`;
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}
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