import { promises as fs } from "node:fs";
import path from "node:path";

import type { AppData } from "@/modules/core/types";

const DATA_DIR = process.env.TEATEA_DATA_DIR ?? path.join(process.cwd(), ".data");
const DATA_FILE = path.join(DATA_DIR, "teatea.json");

function createEmptyData(): AppData {
  return {
    accounts: [],
    sessions: [],
    elders: [],
    auditLogs: [],
  };
}

function normalizeData(data: Partial<AppData>): AppData {
  return {
    accounts: Array.isArray(data.accounts) ? data.accounts : [],
    sessions: Array.isArray(data.sessions) ? data.sessions : [],
    elders: Array.isArray(data.elders) ? data.elders : [],
    auditLogs: Array.isArray(data.auditLogs) ? data.auditLogs : [],
  };
}

function isMissingFileError(error: unknown): boolean {
  return (
    typeof error === "object" &&
    error !== null &&
    "code" in error &&
    (error as { code?: unknown }).code === "ENOENT"
  );
}

export async function readData(): Promise<AppData> {
  try {
    const raw = await fs.readFile(DATA_FILE, "utf8");
    const parsed = JSON.parse(raw) as Partial<AppData>;
    return normalizeData(parsed);
  } catch (error) {
    if (isMissingFileError(error)) {
      return createEmptyData();
    }

    throw error;
  }
}

export async function writeData(data: AppData): Promise<void> {
  await fs.mkdir(DATA_DIR, { recursive: true });
  const temporaryFile = `${DATA_FILE}.tmp`;
  await fs.writeFile(temporaryFile, JSON.stringify(data, null, 2), "utf8");
  await fs.rename(temporaryFile, DATA_FILE);
}

export async function updateData<T>(mutator: (data: AppData) => T): Promise<T> {
  const data = await readData();
  const result = mutator(data);
  await writeData(data);
  return result;
}