// run.ts: run one trigger of a val the way Val Town did.
//
//   run.ts http          serve $VAL_HTTP on $PORT (default 8000)
//   run.ts cron          call $VAL_CRON once with { lastRunAt }
//   run.ts email <file>  call $VAL_EMAIL with the message in <file>
//
// It runs in the val's directory, which holds its code, deno.json, .env,
// and data/. The handler is the file's default export, or its only export.
import PostalMime from "npm:postal-mime@4";

const [mode, arg] = Deno.args;
const dir = Deno.cwd();

async function handler(variable: string) {
  const file = Deno.env.get(variable);
  if (!file) throw new Error(`${variable} is not set in ${dir}/.env`);
  const mod = await import(new URL(file, `file://${dir}/`).href);
  const exported = mod.default ?? Object.values(mod).find((v) => typeof v === "function");
  if (typeof exported === "function") return exported;
  if (typeof exported?.fetch === "function") return exported.fetch.bind(exported);
  throw new Error(`${file} has no default export to run`);
}

if (mode === "http") {
  const fn = await handler("VAL_HTTP");
  Deno.serve({ port: Number(Deno.env.get("PORT") ?? 8000) }, (req) => {
    // Give the val its public host, as on val.run, rather than localhost.
    // Behind front.ts at /<val>/, the val still sees its paths from /, and
    // the prefix arrives in the X-Forwarded-Prefix header.
    const host = req.headers.get("x-forwarded-host");
    if (host) {
      const proto = req.headers.get("x-forwarded-proto") ?? "https";
      const u = new URL(req.url);
      req = new Request(`${proto}://${host}${u.pathname}${u.search}`, req);
    }
    return fn(req);
  });
} else if (mode === "cron") {
  const fn = await handler("VAL_CRON");
  await Deno.mkdir(`${dir}/data`, { recursive: true });
  const state = `${dir}/data/cron-last-run`;
  let lastRunAt: Date | undefined;
  try {
    lastRunAt = new Date((await Deno.readTextFile(state)).trim());
  } catch { /* first run */ }
  const started = new Date();
  await fn({ lastRunAt });
  await Deno.writeTextFile(state, started.toISOString() + "\n");
  Deno.exit(0);
} else if (mode === "email" && arg) {
  const fn = await handler("VAL_EMAIL");
  const m = await PostalMime.parse(await Deno.readFile(arg));
  const addr = (a?: { name?: string; address?: string }) =>
    a?.name ? `${a.name} <${a.address}>` : a?.address ?? "";
  await fn({
    from: addr(m.from),
    to: (m.to ?? []).map(addr),
    cc: m.cc?.map(addr),
    bcc: m.bcc?.map(addr),
    subject: m.subject,
    text: m.text,
    html: m.html,
    attachments: m.attachments.map((a) =>
      new File([a.content], a.filename ?? "attachment", { type: a.mimeType })
    ),
    headers: Object.fromEntries(m.headers.map((h) => [h.key, h.value])),
  });
  Deno.exit(0);
} else {
  console.error("usage: run.ts http | cron | email <message file>");
  Deno.exit(2);
}