// Stands in for https://esm.town/v/std/email: sends through exe.dev's
// email gateway (https://exe.dev/docs/send-email). With no `to`, mail goes
// to the VM's owner, as on Val Town. The gateway sends plain text, from the
// VM's own address, to you, your team, people you share the VM with, and
// people who emailed the VM; `from` and custom headers are ignored.
type Address = string | { email: string; name?: string };
interface Attachment {
  content: string; // base64
  filename: string;
  type?: string;
}
export interface EmailOptions {
  to?: Address | Address[];
  cc?: Address | Address[];
  bcc?: Address | Address[];
  from?: Address;
  replyTo?: Address | Address[];
  subject?: string;
  text?: string;
  html?: string;
  attachments?: Attachment[];
  headers?: Record<string, string>;
}

let owner: string | undefined;
async function ownerEmail() {
  if (!owner) {
    const res = await fetch("https://reflection.int.exe.xyz/email");
    if (!res.ok) throw new Error(`reflection: ${res.status}`);
    const body = (await res.text()).trim();
    owner = body.startsWith("{") ? JSON.parse(body).email : body;
  }
  return owner!;
}
const list = (a?: Address | Address[]) =>
  (Array.isArray(a) ? a : a ? [a] : []).map((x) => (typeof x === "string" ? x : x.email));
const htmlToText = (html: string) =>
  html.replace(/<(br|\/p|\/div|\/h\d|\/li|\/tr)\b[^>]*>/gi, "\n").replace(/<[^>]+>/g, "")
    .replace(/&nbsp;/g, " ").replace(/&lt;/g, "<").replace(/&gt;/g, ">")
    .replace(/&quot;/g, '"').replace(/&#39;/g, "'").replace(/&amp;/g, "&")
    .replace(/\n{3,}/g, "\n\n").trim();

export async function email(data: EmailOptions) {
  const to = [...list(data.to), ...list(data.cc), ...list(data.bcc)];
  if (!to.length) to.push(await ownerEmail());
  const body = data.text ?? (data.html ? htmlToText(data.html) : "");
  for (const recipient of to) {
    const res = await fetch("http://169.254.169.254/gateway/email/send", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({
        to: recipient,
        subject: data.subject ?? `Message from ${Deno.env.get("VAL_NAME") ?? "a val"}`,
        body,
        reply_to: list(data.replyTo)[0],
        attachments: data.attachments?.map((a) => ({
          filename: a.filename,
          content: a.content,
          content_type: a.type,
        })),
      }),
    });
    const result = await res.json().catch(() => ({}));
    if (!res.ok || result.error) {
      throw new Error(`exe.dev email error: ${result.error ?? res.status}`);
    }
  }
  return { message: "Email accepted to be sent" };
}
export default email;