type Env = {
    TURNSTILE_SECRET_KEY?: string;
    AZURE_COMMUNICATION_CONNECTION_STRING?: 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() : "";

const parseConnectionString = (connectionString: string) => {
    const parts = connectionString.split(";").filter(Boolean);
    const map = new Map<string, string>();
    for (const part of parts) {
        const [rawKey, ...rest] = part.split("=");
        const key = rawKey?.trim().toLowerCase();
        const value = rest.join("=").trim();
        if (key && value) {
            map.set(key, value);
        }
    }
    return {
        endpoint: map.get("endpoint") ?? "",
        accessKey: map.get("accesskey") ?? map.get("access_key") ?? "",
    };
};

const handlePost: 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.AZURE_COMMUNICATION_CONNECTION_STRING) {
        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 { endpoint, accessKey } = parseConnectionString(
        env.AZURE_COMMUNICATION_CONNECTION_STRING,
    );
    if (!endpoint || !accessKey) {
        return jsonResponse(
            { ok: false, error: "Email provider not configured." },
            500,
        );
    }

    const emailPayload = {
        senderAddress: fromEmail,
        content: {
            subject: "New contact form submission",
            plainText: `Name: ${name}\nEmail: ${email}\n\n${message}`,
        },
        recipients: {
            to: [{ address: toEmail }],
        },
        replyTo: [{ address: email }],
    };

    const apiBase = endpoint.replace(/\/$/, "");
    const response = await fetch(
        apiBase + "/emails:send?api-version=2023-03-31",
        {
            method: "POST",
            headers: {
                "Content-Type": "application/json",
                "api-key": accessKey,
            },
            body: JSON.stringify(emailPayload),
        },
    );
    if (!response.ok) {
        const errorText = await response.text();
        return jsonResponse(
            {
                ok: false,
                error: "Failed to send email.",
                details: errorText.slice(0, 500),
            },
            502,
        );
    }

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

export const onRequest: PagesFunction<Env> = async (context) => {
    if (context.request.method !== "POST") {
        return jsonResponse({ ok: false, error: "Method not allowed." }, 405);
    }
    return handlePost(context);
};