email-proxy.js

export default {
    async fetch(request) {
        if (request.method !== 'POST') {
            return new Response('Only POST allowed', { status: 405 });
        }

        let data;
        try {
            data = await request.json();
        } catch (err) {
            return new Response('Invalid JSON', { status: 400 });
        }

        const { to, subject, body, contentType = "text/plain" } = data;

        if (!to || !subject || !body) {
            return new Response(
                JSON.stringify({ error: "Fields 'to', 'subject', and 'body' are required." }),
                {
                    status: 400,
                    headers: { "Content-Type": "application/json" }
                }
            );
        }

        // 🔠 Encode MIME header if needed
        function encodeMimeHeader(str) {
            if (/^[\x00-\x7F]*$/.test(str)) return str;
            const utf8 = new TextEncoder().encode(str);
            let binary = "";
            for (let i = 0; i < utf8.length; i++) {
                binary += String.fromCharCode(utf8[i]);
            }
            const base64 = btoa(binary);
            return `=?UTF-8?B?${base64}?=`;
        }

        // 🔐 Safe Base64url encode for full email
        function base64urlEncode(str) {
            const utf8 = new TextEncoder().encode(str);
            let binary = "";
            for (let i = 0; i < utf8.length; i++) {
                binary += String.fromCharCode(utf8[i]);
            }
            const base64 = btoa(binary);
            return base64.replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
        }

        const email = [
            `To: ${to}`,
            `Subject: ${encodeMimeHeader(subject)}`,
            `Content-Type: ${contentType}; charset="UTF-8"`,
            "",
            body
        ].join("\r\n");

        const raw = base64urlEncode(email);

        return new Response(JSON.stringify({ raw }), {
            headers: { "Content-Type": "application/json" }
        });
    }
};