import { NextResponse } from "next/server";
import { unzipSync, strFromU8 } from "fflate";
import { z } from "zod";
import { UserRole } from "@prisma/client";
import { db } from "@/lib/db";
import { requireAuth, isAdmin } from "@/lib/auth";

export const dynamic = "force-dynamic";

// A malformed/crafted backup must not be able to inject arbitrary auth rows.
// users is the security boundary, so it's validated strictly (known fields only,
// role constrained to the enum). Other tables are app-owned data — we only check
// they're arrays; Prisma rejects any unknown columns on insert.
class BadBackup extends Error {}

const userSchema = z
  .object({
    id: z.string(),
    email: z.string(),
    username: z.string().nullable().optional(),
    name: z.string(),
    passwordHash: z.string(),
    role: z.nativeEnum(UserRole).optional(),
    active: z.boolean().optional(),
    mustChangePassword: z.boolean().optional(),
    createdAt: z.string().optional(),
    updatedAt: z.string().optional(),
  })
  .strict();

export async function POST(req: Request) {
  let session;
  try {
    session = await requireAuth();
  } catch {
    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
  }
  if (!isAdmin(session.user.role)) {
    return NextResponse.json({ error: "Forbidden" }, { status: 403 });
  }

  try {
    const form = await req.formData();
    const file = form.get("file") as File | null;
    if (!file) return NextResponse.json({ error: "No file uploaded" }, { status: 400 });

    let files: Record<string, Uint8Array>;
    try {
      files = unzipSync(new Uint8Array(await file.arrayBuffer()));
    } catch {
      throw new BadBackup("not a valid zip");
    }

    const parse = (name: string): unknown => {
      if (!files[name]) throw new BadBackup(`missing ${name}`);
      try {
        return JSON.parse(strFromU8(files[name]));
      } catch {
        throw new BadBackup(`invalid JSON in ${name}`);
      }
    };
    const asArray = (name: string): unknown[] => {
      const v = parse(name);
      if (!Array.isArray(v)) throw new BadBackup(`${name} is not an array`);
      return v;
    };

    const manifest = parse("manifest.json") as { version?: number; exportedAt?: string };
    if (manifest?.version !== 1) {
      return NextResponse.json({ error: "Unsupported backup version" }, { status: 400 });
    }

    // Older backups won't have newer tables — tolerate their absence.
    const locations = files["locations.json"] ? asArray("locations.json") : [];
    const plantTypes = files["plantTypes.json"] ? asArray("plantTypes.json") : [];
    const users = z.array(userSchema).parse(asArray("users.json"));
    const apiTokens = files["apiTokens.json"] ? asArray("apiTokens.json") : [];
    const plantGroups = asArray("plantGroups.json");
    const plants = asArray("plants.json");
    const plantLogs = asArray("plantLogs.json");
    const tasks = asArray("tasks.json");
    const taskCompletions = asArray("taskCompletions.json");
    const labels = files["labels.json"] ? asArray("labels.json") : [];
    const items = files["items.json"] ? asArray("items.json") : [];
    const labelOnItems = files["labelOnItems.json"] ? asArray("labelOnItems.json") : [];
    const itemAttachments = files["itemAttachments.json"] ? asArray("itemAttachments.json") : [];
    const itemLogs = files["itemLogs.json"] ? asArray("itemLogs.json") : [];
    const animals = files["animals.json"] ? asArray("animals.json") : [];
    const animalLogs = files["animalLogs.json"] ? asArray("animalLogs.json") : [];
    const auditEvents = asArray("auditEvents.json");

    // Restore inside a transaction — wipe then reload in FK order.
    await db.$transaction(async (tx) => {
      await tx.taskCompletion.deleteMany();
      await tx.plantLog.deleteMany();
      await tx.itemLog.deleteMany();
      await tx.itemAttachment.deleteMany();
      await tx.labelOnItem.deleteMany();
      await tx.animalLog.deleteMany();
      await tx.task.deleteMany();
      await tx.item.deleteMany();
      await tx.label.deleteMany();
      await tx.animal.deleteMany();
      await tx.plant.deleteMany();
      await tx.plantGroup.deleteMany();
      await tx.plantType.deleteMany();
      await tx.location.deleteMany();
      await tx.apiToken.deleteMany();
      await tx.auditEvent.deleteMany();
      await tx.user.deleteMany();

      if (users.length) await tx.user.createMany({ data: users });
      if (apiTokens.length) await tx.apiToken.createMany({ data: apiTokens as never });
      // Location self-references parentId; a single createMany is one statement,
      // so the FK is validated only after every row exists — order-independent.
      if (locations.length) await tx.location.createMany({ data: locations as never });
      if (plantTypes.length) await tx.plantType.createMany({ data: plantTypes as never });
      if (plantGroups.length) await tx.plantGroup.createMany({ data: plantGroups as never });
      if (plants.length) await tx.plant.createMany({ data: plants as never });
      if (plantLogs.length) await tx.plantLog.createMany({ data: plantLogs as never });
      if (labels.length) await tx.label.createMany({ data: labels as never });
      // Item self-references parentItemId; one createMany statement validates the
      // FK only after all rows exist — order-independent.
      if (items.length) await tx.item.createMany({ data: items as never });
      if (labelOnItems.length) await tx.labelOnItem.createMany({ data: labelOnItems as never });
      if (itemAttachments.length) await tx.itemAttachment.createMany({ data: itemAttachments as never });
      if (itemLogs.length) await tx.itemLog.createMany({ data: itemLogs as never });
      if (animals.length) await tx.animal.createMany({ data: animals as never });
      if (animalLogs.length) await tx.animalLog.createMany({ data: animalLogs as never });
      if (tasks.length) await tx.task.createMany({ data: tasks as never });
      if (taskCompletions.length) await tx.taskCompletion.createMany({ data: taskCompletions as never });
      if (auditEvents.length) await tx.auditEvent.createMany({ data: auditEvents as never });
    });

    await db.auditEvent.create({
      data: {
        action: "admin.restore",
        actorId: session.user.id,
        payload: { exportedAt: manifest.exportedAt, restoredAt: new Date().toISOString() },
      },
    });

    return NextResponse.json({ ok: true, exportedAt: manifest.exportedAt });
  } catch (err) {
    if (err instanceof BadBackup || err instanceof z.ZodError) {
      return NextResponse.json(
        { error: "The backup file is invalid or corrupted." },
        { status: 400 }
      );
    }
    console.error("restore failed:", err);
    return NextResponse.json({ error: "Restore failed." }, { status: 500 });
  }
}