// The mail of the contact form (components/ContactForm.vue → POST /api/contact). The mail service (libreshop/mail src/app.py)
// sends it from POST /v1/send/message, whose JSON body is { to_email, subject, message, html? }. It sets no Reply-To, so the
// sender's address is in the text. Pure: no Nuxt, Nitro or h3 imports, tested in tests/unit/contactMail.test.ts.

export const CONTACT_RECIPIENT = "paperwork@muellerprints.de";
export const MAIL_SEND_PATH = "/v1/send/message";

/** The body of POST /v1/send/message. */
export type ContactMail = { to_email: string; subject: string; message: string };

/** The mail to send, or the German message of the 400 for the form. */
export type ContactMailResult = { ok: true; mail: ContactMail } | { ok: false; message: string };

const EMAIL = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;

const isObject = (value: unknown): value is Record<string, unknown> => typeof value === "object" && value !== null && !Array.isArray(value);

const isFilled = (value: unknown): value is string => typeof value === "string" && value.trim() !== "";

// A line break in the subject would end its header and start another one.
const oneLine = (text: string): string => text.replace(/[\r\n]+/g, " ").trim();

/** The URL of the mail service's send endpoint, from its base URL (runtimeConfig.mailApiUrl). */
export const mailSendUrl = (mailApiUrl: string): string => `${mailApiUrl.replace(/\/+$/, "")}${MAIL_SEND_PATH}`;

/** Checks the form's body { name, email, subject?, message } and builds the mail to the shop. */
export const contactMail = (body: unknown): ContactMailResult => {
	const fields: Record<string, unknown> = isObject(body) ? body : {};
	const { name, email, subject, message } = fields;
	if (!isFilled(name) || !isFilled(email) || !isFilled(message)) {
		return { ok: false, message: "Name, E-Mail und Nachricht sind erforderlich" };
	}
	if (!EMAIL.test(email)) {
		return { ok: false, message: "Ungültige E-Mail-Adresse" };
	}

	const topic = typeof subject === "string" ? oneLine(subject) : "";
	return {
		ok: true,
		mail: {
			to_email: CONTACT_RECIPIENT,
			subject: `Kontaktanfrage: ${topic || "Anfrage über Website"}`,
			message: [
				`Name: ${name}`,
				`E-Mail: ${email}`,
				`Betreff: ${topic || "Kontaktanfrage über Website"}`,
				"",
				"Nachricht:",
				message,
				"",
				"---",
				"Diese Nachricht wurde über das Kontaktformular auf muellerprints.de gesendet."
			].join("\n")
		}
	};
};