type Env = {
    TURNSTILE_SECRET_KEY?: string;
    RESEND_API_KEY?: string;
    CONTACT_FROM_EMAIL?: string;
    CONTACT_TO_EMAIL?: string;
};

const jsonResponse = (data: Record<string, unknown>, status = 200) =>
    new Response(JSON.stringify(data), {
        status,
        headers: { "content-type": "application/json" },
    });

const readFormField = (value: FormDataEntryValue | null) =>
    typeof value === "string" ? value.trim() : "";

export const onRequestPost: PagesFunction<Env> = async ({
    request,
    env,
}) => {
    const formData = await request.formData();
    const name = readFormField(formData.get("name"));
    const email = readFormField(formData.get("email"));
    const message = readFormField(formData.get("message"));
    const turnstileToken = readFormField(
        formData.get("cf-turnstile-response")
    );

    if (!name || !email || !message) {
        return jsonResponse(
            { ok: false, error: "Missing required fields." },
            400
        );
    }

    if (!env.TURNSTILE_SECRET_KEY) {
        return jsonResponse(
            { ok: false, error: "Turnstile secret key not configured." },
            500
        );
    }

    if (!turnstileToken) {
        return jsonResponse(
            { ok: false, error: "Turnstile verification failed." },
            400
        );
    }

    const verifyBody = new URLSearchParams({
        secret: env.TURNSTILE_SECRET_KEY,
        response: turnstileToken,
        remoteip: request.headers.get("CF-Connecting-IP") ?? "",
    });

    const verifyResponse = await fetch(
        "https://challenges.cloudflare.com/turnstile/v0/siteverify",
        {
            method: "POST",
            body: verifyBody,
        }
    );
    const verifyResult = (await verifyResponse.json()) as {
        success?: boolean;
    };

    if (!verifyResult.success) {
        return jsonResponse(
            { ok: false, error: "Turnstile verification failed." },
            400
        );
    }

    if (!env.RESEND_API_KEY) {
        return jsonResponse(
            { ok: false, error: "Email provider not configured." },
            500
        );
    }

    const fromEmail = env.CONTACT_FROM_EMAIL;
    if (!fromEmail) {
        return jsonResponse(
            { ok: false, error: "Sender email not configured." },
            500
        );
    }

    const toEmail = env.CONTACT_TO_EMAIL ?? "calum@muir.in";

    const emailPayload = {
        from: fromEmail,
        to: [toEmail],
        reply_to: email,
        subject: "New contact form submission",
        text: `Name: ${name}\nEmail: ${email}\n\n${message}`,
    };

    const emailResponse = await fetch("https://api.resend.com/emails", {
        method: "POST",
        headers: {
            Authorization: `Bearer ${env.RESEND_API_KEY}`,
            "Content-Type": "application/json",
        },
        body: JSON.stringify(emailPayload),
    });

    if (!emailResponse.ok) {
        return jsonResponse(
            { ok: false, error: "Failed to send email." },
            502
        );
    }

    return jsonResponse({ ok: true });
};