import { json } from "@sveltejs/kit";
import { env as publicEnv } from "$env/dynamic/public";
import { env as privateEnv } from "$env/dynamic/private";
import type { RequestHandler } from "./$types";
import { notifyMatrix } from "$lib/server/matrix";
import {
  HONEYPOT_FIELDS,
  LIMITS,
  validateContact,
} from "$lib/components/internal/contact-form-validation";

const TURNSTILE_SECRET = privateEnv.TURNSTILE_SECRET ?? "";
const TURNSTILE_ENABLED = TURNSTILE_SECRET !== "";

async function verifyTurnstile(token: string, ip: string): Promise<boolean> {
  if (!TURNSTILE_ENABLED) return true;
  if (!token) return false;
  try {
    const res = await fetch("https://challenges.cloudflare.com/turnstile/v0/siteverify", {
      method: "POST",
      headers: { "Content-Type": "application/x-www-form-urlencoded" },
      body: new URLSearchParams({ secret: TURNSTILE_SECRET, response: token, remoteip: ip }),
    });
    if (!res.ok) return false;
    const data = (await res.json()) as { success?: boolean };
    return data.success === true;
  } catch (e) {
    console.error("[contact] turnstile verify failed:", e);
    return false;
  }
}

const ALLOWED_ORIGINS = new Set([
  "https://windwiderstand.de",
  "https://www.windwiderstand.de",
  "http://localhost:5173",
  "http://localhost:4173",
]);

export const POST: RequestHandler = async ({ request, getClientAddress }) => {
  // Origin/Referer must match — blocks naive cross-site POSTs
  const origin = request.headers.get("origin") ?? "";
  const referer = request.headers.get("referer") ?? "";
  const refererOrigin = referer ? safeOrigin(referer) : "";
  if (!ALLOWED_ORIGINS.has(origin) && !ALLOWED_ORIGINS.has(refererOrigin)) {
    return json({ error: "Ungültige Anfrage." }, { status: 403 });
  }

  const raw = await request.json().catch(() => null);
  if (!raw || typeof raw !== "object") {
    return json({ error: "Ungültige Anfrage." }, { status: 400 });
  }
  const body = raw as Record<string, unknown>;

  // Honeypots — must all be empty
  for (const hp of HONEYPOT_FIELDS) {
    const val = body[hp];
    if (typeof val === "string" && val.trim() !== "") {
      // Pretend success so bots don't learn the trap exists
      return json({ ok: true }, { status: 201 });
    }
  }

  // Client age — bots usually post immediately
  const clientAge = Number(body._client_age_ms);
  if (!Number.isFinite(clientAge) || clientAge < LIMITS.MIN_CLIENT_AGE_MS) {
    return json({ error: "Bitte etwas mehr Zeit lassen." }, { status: 429 });
  }

  // Cloudflare Turnstile (skipped when no secret configured)
  if (TURNSTILE_ENABLED) {
    const token = typeof body.cf_turnstile_token === "string" ? body.cf_turnstile_token : "";
    const ok = await verifyTurnstile(token, getClientAddress());
    if (!ok) {
      return json({ error: "captcha" }, { status: 403 });
    }
  }

  // Full validation
  const fields = {
    name: typeof body.name === "string" ? body.name : "",
    email: typeof body.email === "string" ? body.email : "",
    subject: typeof body.subject === "string" ? body.subject : "",
    message: typeof body.message === "string" ? body.message : "",
    consent: body.consent === true,
  };
  const errors = validateContact(fields);
  if (Object.keys(errors).length > 0) {
    return json({ errors }, { status: 422 });
  }

  // Forward to CMS forms plugin
  const cmsBase = (publicEnv.PUBLIC_CMS_URL || "http://localhost:3099").replace(/\/$/, "");
  const cmsEnv = publicEnv.PUBLIC_CMS_ENV || "";
  const cmsUrl = cmsEnv
    ? `${cmsBase}/api/forms/kontakt/submit?_environment=${encodeURIComponent(cmsEnv)}`
    : `${cmsBase}/api/forms/kontakt/submit`;

  const payload = {
    name: fields.name.trim(),
    email: fields.email.trim(),
    subject: fields.subject.trim(),
    message: fields.message.trim(),
    consent_at: new Date().toISOString(),
    submitted_via: "windwiderstand.de/api/contact",
    user_agent: (request.headers.get("user-agent") ?? "").slice(0, 200),
  };

  let res: Response;
  try {
    // No Origin header — we already validated it at this server.
    // CMS forms plugin (REQUIRE_ORIGIN=false) accepts requests without one.
    res = await fetch(cmsUrl, {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
        "X-Forwarded-For": getClientAddress(),
      },
      body: JSON.stringify(payload),
    });
  } catch (e) {
    console.error("[contact] CMS fetch failed:", e);
    return json({ error: "Server nicht erreichbar." }, { status: 502 });
  }

  if (res.ok) {
    void notifyMatrix(
      `✉️ Neue Kontakt-Nachricht von ${payload.name} (${payload.email})${payload.subject ? `: ${payload.subject}` : ""}`,
    );
    return json({ ok: true }, { status: 201 });
  }
  if (res.status === 429) {
    return json({ error: "Zu viele Anfragen. Bitte später erneut versuchen." }, { status: 429 });
  }
  const text = await res.text().catch(() => "");
  console.error("[contact] CMS error", res.status, text);
  return json({ error: "Fehler beim Senden." }, { status: 502 });
};

function safeOrigin(u: string): string {
  try {
    return new URL(u).origin;
  } catch {
    return "";
  }
}