import { Prisma } from "@prisma/client";
import { NextResponse } from "next/server";
import { z } from "zod";

import { snapshotBudget } from "@/lib/audit-snapshots";
import { createAuditLog } from "@/lib/audit-log";
import { canManageBudgets } from "@/lib/domain";
import prisma from "@/lib/prisma";
import { getCurrentViewer } from "@/lib/session";

const updateBudgetSchema = z
  .object({
    name: z.string().trim().min(2).max(80),
    totalBudget: z.coerce.number().min(0),
    releasedAmount: z.coerce.number().min(0).optional(),
    colorCode: z.string().regex(/^#([0-9a-fA-F]{6})$/)
  })
  .superRefine((value, ctx) => {
    if (value.releasedAmount !== undefined && value.releasedAmount > value.totalBudget) {
      ctx.addIssue({
        code: z.ZodIssueCode.custom,
        message: "Der bereits an die AG uebergebene Betrag darf das Budget nicht uebersteigen.",
        path: ["releasedAmount"]
      });
    }
  });

type Context = {
  params: Promise<{
    id: string;
  }>;
};

export async function PATCH(request: Request, { params }: Context) {
  const { id } = await params;
  const viewer = await getCurrentViewer();

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

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

  const budget = await prisma.budget.findUnique({
    where: { id }
  });

  if (!budget) {
    return NextResponse.json({ error: "Budget nicht gefunden." }, { status: 404 });
  }

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

  if (!parsed.success) {
    return NextResponse.json({ error: "Budgetname, Betrag, Mitteluebergabe oder Farbe sind ungueltig." }, { status: 400 });
  }

  try {
    const previousBudget = budget;
    const nextReleasedAmount = parsed.data.releasedAmount ?? Number(previousBudget.releasedAmount);
    const updatedBudget = await prisma.budget.update({
      where: { id },
      data: {
        name: parsed.data.name,
        totalBudget: parsed.data.totalBudget,
        releasedAmount: nextReleasedAmount,
        colorCode: parsed.data.colorCode
      }
    });

    await createAuditLog(prisma, {
      actorId: viewer.id,
      action: "budget.update",
      entityType: "budget",
      entityId: updatedBudget.id,
      entityLabel: updatedBudget.name,
      summary: `Budget ${updatedBudget.name} wurde aktualisiert.`,
      metadata: {
        totalBudget: parsed.data.totalBudget,
        releasedAmount: nextReleasedAmount,
        colorCode: parsed.data.colorCode,
        rollback: {
          kind: "budget.update",
          previous: snapshotBudget(previousBudget),
          next: snapshotBudget(updatedBudget)
        }
      }
    });

    return NextResponse.json({ budget: updatedBudget });
  } catch (error) {
    if (
      error instanceof Prisma.PrismaClientKnownRequestError &&
      error.code === "P2002"
    ) {
      return NextResponse.json(
        { error: "In dieser AG gibt es bereits ein Budget mit diesem Namen." },
        { status: 409 }
      );
    }

    throw error;
  }
}

export async function DELETE(_: Request, { params }: Context) {
  const { id } = await params;
  const viewer = await getCurrentViewer();

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

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

  const budget = await prisma.budget.findUnique({
    where: { id },
    include: {
      _count: {
        select: {
          expenses: true
        }
      }
    }
  });

  if (!budget) {
    return NextResponse.json({ error: "Budget nicht gefunden." }, { status: 404 });
  }

  if (budget._count.expenses > 0) {
    return NextResponse.json(
      { error: "Dieses Budget enthaelt noch Ausgaben. Bitte loesche oder verschiebe erst die Posten." },
      { status: 400 }
    );
  }

  await prisma.budget.delete({
    where: { id }
  });

  await createAuditLog(prisma, {
    actorId: viewer.id,
    action: "budget.delete",
    entityType: "budget",
    entityId: budget.id,
    entityLabel: budget.name,
    summary: `Budget ${budget.name} wurde geloescht.`,
    metadata: {
      rollback: {
        kind: "budget.delete",
        deleted: snapshotBudget(budget)
      }
    }
  });

  return NextResponse.json({ ok: true });
}