import { isNotificationCategory, CATEGORY_INFO } from "~/lib/notification-categories";
import { enforceRateLimit, requestIp } from "../limits";
import { canUnsubscribe, unsubscribe, userForUnsubscribeToken } from "./prefs";
import type { UnsubscribeTarget } from "./prefs";

export const UNSUBSCRIBE_PATH = "/email/unsubscribe";
const HTML_ESCAPES: Record<string, string> = { "&": "&amp;", "<": "&lt;", ">": "&gt;", '"': "&quot;", "'": "&#39;" };

function escapeHtml(value: string): string {
  return value.replace(/[&<>"']/g, (char) => HTML_ESCAPES[char] ?? char);
}

function parseTarget(value: string | null): UnsubscribeTarget | null {
  if (value === "participating" || value === "watching") return value;
  return value && isNotificationCategory(value) ? value : null;
}

function targetLabel(target: UnsubscribeTarget): string {
  if (target === "participating") return "participating and @mention";
  if (target === "watching") return "watched repository";
  return CATEGORY_INFO[target].label.toLowerCase();
}

function page(body: string, status = 200): Response {
  return new Response(
    `<!doctype html><html><head><meta name="viewport" content="width=device-width"><title>Unsubscribe</title></head>
<body style="font-family:system-ui;background:#09090b;color:#e4e4e7;padding:32px"><div style="max-width:480px;margin:0 auto">${body}
<p><a href="/settings/notifications" style="color:#fb923c">Manage notification settings</a></p></div></body></html>`,
    {
      status,
      headers: {
        "content-type": "text/html; charset=utf-8",
        "content-security-policy": "default-src 'none'; style-src 'unsafe-inline'; form-action 'self'",
        "referrer-policy": "no-referrer",
      },
    },
  );
}

/**
 * GET shows a confirmation form so link scanners can't unsubscribe anyone; POST (the form or an RFC 8058
 * one-click request from the mail client) turns email off for that category. The token is the credential.
 */
export async function handleUnsubscribeRoute(request: Request, url: URL): Promise<Response | null> {
  if (url.pathname !== UNSUBSCRIBE_PATH) return null;
  const token = url.searchParams.get("token") ?? "";
  await enforceRateLimit("AUTH_LIMITER", `unsubscribe:${requestIp(request)}`);
  const target = parseTarget(url.searchParams.get("category"));
  if (target && !canUnsubscribe(target)) {
    return page(
      "<h1>Not available</h1><p>Security alerts can only be changed from your notification settings.</p>",
      403,
    );
  }
  const userId = token && target ? await userForUnsubscribeToken(token, target) : null;
  if (!userId || !target)
    return page("<h1>Link not valid</h1><p>This unsubscribe link is invalid or expired.</p>", 404);
  const label = escapeHtml(targetLabel(target));
  if (request.method === "POST") {
    await unsubscribe(userId, target);
    return page(`<h1>Unsubscribed</h1><p>You will no longer receive ${label} emails.</p>`);
  }
  if (request.method !== "GET" && request.method !== "HEAD") return page("<h1>Method not allowed</h1>", 405);
  const action = `${UNSUBSCRIBE_PATH}?${new URLSearchParams({ token, category: target })}`;
  return page(`<h1>Unsubscribe</h1><p>Stop sending ${label} emails? Web notifications are not affected.</p>
<form method="post" action="${escapeHtml(action)}"><button type="submit" style="background:#f97316;border:0;padding:10px 16px;border-radius:6px;font-weight:600">Unsubscribe</button></form>`);
}