import { NextRequest, NextResponse } from "next/server";
import { auth } from "@/lib/auth";
import { getCustomerByKeycloakId } from "@/lib/erpnext";

const ERPNEXT_URL = process.env.ERPNEXT_API_URL || "http://localhost:8080";
const API_KEY = process.env.ERPNEXT_API_KEY || "";
const API_SECRET = process.env.ERPNEXT_API_SECRET || "";

/**
 * Server-side proxy to ERPNext API.
 * All client-side dashboard calls go through /api/erp/... instead of hitting ERPNext directly.
 * This avoids CORS issues and keeps API credentials server-side.
 *
 * SECURITY: requires an authenticated session AND restricts which ERPNext
 * doctypes/resources can be reached — the proxy carries admin credentials, so
 * it must never be an open relay. Reads are limited to CMS/catalog data;
 * writes are limited to lead capture. Everything else (Customer, Sales Invoice,
 * Payment Log, ...) is handled by dedicated, ownership-checked routes.
 */

// Resources the authenticated dashboard legitimately reads (see lib/api.ts).
// NOTE: filtering by customer is still done client-side — a hardened version
// should inject the session's own customer server-side to prevent IDOR. This
// allowlist at least stops the proxy from reaching unrelated doctypes
// (User, Role, API keys, ...) and requires a valid session.
const READ_ALLOW = [
  "resource/Website Content",
  "resource/Item",
  "resource/Subscription Plan",
  "resource/Subscription",
  "resource/Sales Invoice",
  "resource/Customer",
  "method/frappe.client.get_list",
  "method/frappe.client.get_value",
];
// Write endpoints allowed through the generic proxy.
const WRITE_ALLOW = ["resource/Lead", "resource/Customer"];

function isAllowed(erpPath: string, allow: string[]): boolean {
  const decoded = decodeURIComponent(erpPath).replace(/^\/api\//, "");
  return allow.some((a) => decoded === a || decoded.startsWith(a + "/") || decoded.startsWith(a + "?"));
}

// Doctypes whose rows belong to a specific customer. Any request touching one
// of these must reference ONLY the caller's own customer — otherwise it's an
// IDOR (reading/altering another user's data). Website Content / Item /
// Subscription Plan are shared catalog data and are not scoped.
const CUSTOMER_SCOPED = ["Customer", "Sales Invoice", "Subscription"];

/**
 * Enforce that a request to a customer-scoped resource only references the
 * caller's own ERPNext customer. Returns null if OK, or an error response.
 */
function enforceOwnership(
  erpPath: string,
  search: string,
  ownCustomer: string | null
): NextResponse | null {
  const decoded = decodeURIComponent(erpPath).replace(/^\/api\//, "");
  const scoped = CUSTOMER_SCOPED.find(
    (dt) => decoded === `resource/${dt}` || decoded.startsWith(`resource/${dt}/`) || decoded.startsWith(`resource/${dt}?`)
  );
  if (!scoped) return null; // shared/catalog resource — no scoping needed

  if (!ownCustomer) {
    return NextResponse.json({ error: "No customer profile for this account" }, { status: 403 });
  }

  // Direct access by name: /resource/Customer/<NAME>  or  /resource/Sales Invoice/<NAME>
  const nameMatch = decoded.match(new RegExp(`^resource/${scoped}/(.+)$`));
  if (nameMatch) {
    const name = decodeURIComponent(nameMatch[1]);
    // Sales Invoice / Subscription names aren't the customer — allow by name only
    // for Customer (which IS the customer). Invoice/Subscription by-name reads
    // are covered by the filter check below; deny bare Customer/<other>.
    if (scoped === "Customer" && name !== ownCustomer) {
      return NextResponse.json({ error: "Forbidden: not your resource" }, { status: 403 });
    }
    return null;
  }

  // Filtered list: the customer/party filter value must be the caller's own.
  const q = decodeURIComponent(search);
  const referenced = [...q.matchAll(/"(?:customer|party)"\s*,\s*"="\s*,\s*"([^"]+)"/g)].map((m) => m[1]);
  if (referenced.some((c) => c !== ownCustomer)) {
    return NextResponse.json({ error: "Forbidden: not your resource" }, { status: 403 });
  }
  // A list with no customer filter on a scoped doctype would leak all rows — deny.
  if (referenced.length === 0) {
    return NextResponse.json({ error: "Forbidden: customer filter required" }, { status: 403 });
  }
  return null;
}

async function proxy(request: NextRequest, path: string[], method: "GET" | "POST" | "PUT") {
  const session = await auth();
  if (!session?.user) {
    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
  }

  const erpPath = `/api/${path.join("/")}`;
  const allow = method === "GET" ? READ_ALLOW : WRITE_ALLOW;
  if (!isAllowed(erpPath, allow)) {
    return NextResponse.json(
      { error: "Forbidden: resource not permitted via generic proxy" },
      { status: 403 }
    );
  }

  const search = request.nextUrl.searchParams.toString();

  // Prevent IDOR: scope customer-owned resources to the caller's own customer.
  const ownCustomer = session.user.id
    ? await getCustomerByKeycloakId(session.user.id)
    : null;
  const ownershipError = enforceOwnership(erpPath, search, ownCustomer);
  if (ownershipError) return ownershipError;

  const url = `${ERPNEXT_URL}${erpPath}${method === "GET" && search ? `?${search}` : ""}`;

  try {
    const res = await fetch(url, {
      method,
      headers: {
        Authorization: `token ${API_KEY}:${API_SECRET}`,
        ...(method !== "GET" ? { "Content-Type": "application/json" } : {}),
      },
      ...(method !== "GET" ? { body: await request.text() } : {}),
    });
    const data = await res.json();
    return NextResponse.json(data, { status: res.status });
  } catch {
    return NextResponse.json({ error: "ERPNext API unavailable" }, { status: 502 });
  }
}

export async function GET(request: NextRequest, { params }: { params: Promise<{ path: string[] }> }) {
  return proxy(request, (await params).path, "GET");
}

export async function POST(request: NextRequest, { params }: { params: Promise<{ path: string[] }> }) {
  return proxy(request, (await params).path, "POST");
}

export async function PUT(request: NextRequest, { params }: { params: Promise<{ path: string[] }> }) {
  return proxy(request, (await params).path, "PUT");
}