import { mkdir, stat, writeFile } from "fs/promises";
import path from "path";
import { randomUUID } from "crypto";
import { NextResponse } from "next/server";
import { requireCurrentUser, UnauthorizedError } from "@/lib/auth";
import { prisma } from "@/lib/prisma";

const uploadRoot = "/data/uploads";
const maxFileSizeBytes = 2 * 1024 * 1024;

const allowedMimeTypes: Record<string, string> = {
  "image/png": "png",
  "image/svg+xml": "svg",
  "image/x-icon": "ico",
  "image/vnd.microsoft.icon": "ico"
};

function getExtension(file: File): string | null {
  return allowedMimeTypes[file.type] ?? null;
}

async function ensureSettings(userId: string, email: string) {
  const existingSettings = await prisma.settings.findUnique({
    where: { userId }
  });

  if (existingSettings) {
    return existingSettings;
  }

  return prisma.settings.create({
    data: {
      userId,
      darkMode: false,
      calendarIcsUrl: null,
      calendarMaxEvents: 8,
      calendarLookaheadDays: 60,
      dashboardTitle: "Personal Dashboard",
      dashboardSubtitle: email,
      logoUrl: "/logo.svg",
      faviconUrl: "/favicon.ico",
      backgroundImageUrl: "/background-fancy.svg",
      backgroundImageOpacity: 32,
      primaryColor: "#2563eb",
      secondaryColor: "#dbeafe",
      customCss: ""
    }
  });
}

export async function POST(request: Request) {
  try {
    const user = await requireCurrentUser();
    await ensureSettings(user.id, user.email);

    const formData = await request.formData();
    const file = formData.get("file");

    if (!(file instanceof File)) {
      return NextResponse.json({ error: "Keine Datei hochgeladen." }, { status: 400 });
    }

    if (file.size <= 0 || file.size > maxFileSizeBytes) {
      return NextResponse.json({ error: "Datei ist leer oder größer als 2 MB." }, { status: 400 });
    }

    const extension = getExtension(file);

    if (!extension) {
      return NextResponse.json({ error: "Nur ICO, PNG oder SVG sind erlaubt." }, { status: 400 });
    }

    const userUploadDirectory = path.join(uploadRoot, "users", user.id);
    await mkdir(userUploadDirectory, { recursive: true });

    const fileName = `favicon-${Date.now()}-${randomUUID()}.${extension}`;
    const filePath = path.join(userUploadDirectory, fileName);
    const bytes = await file.arrayBuffer();

    await writeFile(filePath, Buffer.from(bytes));

    const writtenFile = await stat(filePath);

    if (!writtenFile.isFile() || writtenFile.size <= 0) {
      return NextResponse.json({ error: "Favicon wurde nicht korrekt gespeichert." }, { status: 500 });
    }

    const faviconUrl = `/api/uploads/users/${user.id}/${fileName}`;

    const settings = await prisma.settings.update({
      where: { userId: user.id },
      data: { faviconUrl }
    });

    return NextResponse.json({ settings });
  } catch (error) {
    if (error instanceof UnauthorizedError) {
      return NextResponse.json({ error: "Nicht angemeldet." }, { status: 401 });
    }

    return NextResponse.json({ error: "Favicon konnte nicht hochgeladen werden." }, { status: 500 });
  }
}

export async function DELETE() {
  try {
    const user = await requireCurrentUser();
    await ensureSettings(user.id, user.email);

    const settings = await prisma.settings.update({
      where: { userId: user.id },
      data: { faviconUrl: "/favicon.ico" }
    });

    return NextResponse.json({ settings });
  } catch (error) {
    if (error instanceof UnauthorizedError) {
      return NextResponse.json({ error: "Nicht angemeldet." }, { status: 401 });
    }

    return NextResponse.json({ error: "Favicon konnte nicht zurückgesetzt werden." }, { status: 500 });
  }
}