import { NextResponse } from "next/server";
import { z } from "zod";
import { requirePlatformRole } from "@/lib/session";
import { generateInvoice } from "@/lib/billing";
import { safeError } from "@/lib/errors";

/**
 * POST /api/admin/billing/generate
 *
 * Compute (and optionally commit) an invoice for an (org, year,
 * month). Platform-only — this is the testing/admin tool.
 *
 * Body:
 *   {
 *     zitadelOrgId: string,
 *     year: number (e.g. 2026),
 *     month: number (1-12),
 *     locale?: 'de' | 'en' | 'fr' | 'it',  // default: from country
 *     dryRun?: boolean                      // default: false
 *   }
 *
 * Response on success:
 *   {
 *     draft: InvoiceDraft,           // line breakdown + warnings
 *     invoice: Invoice | null,       // null when dryRun=true
 *   }
 *
 * If an invoice for that (org, period) already exists, returns
 * 409 with a clear message. Use the delete endpoint first to
 * regenerate.
 */

const bodySchema = z.object({
  zitadelOrgId: z.string().min(1),
  year: z.number().int().min(2020).max(2100),
  month: z.number().int().min(1).max(12),
  locale: z.enum(["de", "en", "fr", "it"]).optional(),
  dryRun: z.boolean().optional().default(false),
});

export async function POST(request: Request) {
  try {
    await requirePlatformRole();
  } catch {
    return NextResponse.json({ error: "Forbidden" }, { status: 403 });
  }
  const body = await request.json().catch(() => ({}));
  const parsed = bodySchema.safeParse(body);
  if (!parsed.success) {
    return NextResponse.json(
      { error: "Invalid request", details: parsed.error.flatten() },
      { status: 400 }
    );
  }
  try {
    const result = await generateInvoice(parsed.data);
    return NextResponse.json(result);
  } catch (e: any) {
    console.error("Invoice generation failed:", e);
    const msg = safeError(e, "Generation failed");
    // Specific 409 for the "already exists" case so the UI can
    // show a "delete first" link.
    const status = /already exists/i.test(msg) ? 409 : 500;
    return NextResponse.json({ error: msg }, { status });
  }
}