import { NextResponse } from "next/server";
import { z } from "zod";

import { getAppSettings, serializeAppSettings, toApprovalThresholdNumber } from "@/lib/app-settings";
import { snapshotAppSettings } from "@/lib/audit-snapshots";
import { createAuditLog } from "@/lib/audit-log";
import { APPROVAL_FLOW, canManageSettings, canManageUsers, normalizeRequiredApprovalTypes } from "@/lib/domain";
import prisma from "@/lib/prisma";
import { getCurrentViewer } from "@/lib/session";

const settingsSchema = z.object({
  approvalThreshold: z.coerce.number().min(0).max(100000).optional(),
  requiredApprovalTypes: z.array(z.enum(APPROVAL_FLOW)).min(1).optional(),
  budgetReleaseNotifyTarget: z.enum(["ALL_GROUP_USERS", "GROUP_MEMBERS_ONLY"]).optional()
});

export async function PATCH(request: Request) {
  const viewer = await getCurrentViewer();

  if (!viewer) {
    return NextResponse.json({ error: "Nicht angemeldet." }, { status: 401 });
  }

  if (!canManageUsers(viewer.role)) {
    return NextResponse.json({ error: "Nur Vorstand allgemein, AG Orga oder AG Finanzen duerfen Einstellungen aendern." }, { status: 403 });
  }

  const body = await request.json().catch(() => null);
  const parsed = settingsSchema.safeParse(body);

  if (!parsed.success) {
    return NextResponse.json({ error: "Bitte gueltige Einstellungen eingeben." }, { status: 400 });
  }

  const changesOrgaSettings =
    parsed.data.requiredApprovalTypes !== undefined || parsed.data.budgetReleaseNotifyTarget !== undefined;

  if (changesOrgaSettings && !canManageSettings(viewer.role)) {
    return NextResponse.json({ error: "Nur AG Orga darf Zuständigkeiten und Benachrichtigungen ändern." }, { status: 403 });
  }

  const existingSettings = await getAppSettings();
  const previousSnapshot = snapshotAppSettings(existingSettings);

  const appSettings = await prisma.appSettings.update({
    where: {
      id: existingSettings.id
    },
    data: {
      ...(parsed.data.approvalThreshold !== undefined ? { approvalThreshold: parsed.data.approvalThreshold } : {}),
      ...(parsed.data.requiredApprovalTypes !== undefined
        ? { requiredApprovalTypes: normalizeRequiredApprovalTypes(parsed.data.requiredApprovalTypes) }
        : {}),
      ...(parsed.data.budgetReleaseNotifyTarget !== undefined
        ? { budgetReleaseNotifyTarget: parsed.data.budgetReleaseNotifyTarget }
        : {})
    }
  });

  await createAuditLog(prisma, {
    actorId: viewer.id,
    action: "settings.update",
    entityType: "settings",
    entityId: appSettings.id,
    entityLabel: "Freigabe-Schwelle",
    summary: changesOrgaSettings
      ? "Zuständigkeiten und Benachrichtigungen wurden aktualisiert."
      : `Freigabe-Schwelle wurde auf ${toApprovalThresholdNumber(appSettings.approvalThreshold).toFixed(2)} EUR gesetzt.`,
    metadata: {
      settings: serializeAppSettings(appSettings),
      rollback: {
        kind: "settings.update",
        previous: previousSnapshot
      }
    }
  });

  return NextResponse.json({
    ok: true,
    settings: serializeAppSettings(appSettings)
  });
}