import path from "path";
import fs from "fs";
import os from "os";
import { sync as mkdirpSync } from "mkdirp";
import * as babel from "@babel/core";
import findCacheDir from "find-cache-dir";

const DEFAULT_CACHE_DIR =
  findCacheDir({ name: "@babel/register" }) || os.homedir() || os.tmpdir();
const DEFAULT_FILENAME = path.join(
  DEFAULT_CACHE_DIR,
  `.babel.${babel.version}.${babel.getEnv()}.json`,
);
const FILENAME: string = process.env.BABEL_CACHE_PATH || DEFAULT_FILENAME;
let data: Object = {};

/**
 * Write stringified cache to disk.
 */

export function save() {
  let serialised: string = "{}";

  try {
    serialised = JSON.stringify(data, null, "  ");
  } catch (err) {
    if (err.message === "Invalid string length") {
      err.message = "Cache too large so it's been cleared.";
      console.error(err.stack);
    } else {
      throw err;
    }
  }

  mkdirpSync(path.dirname(FILENAME));
  fs.writeFileSync(FILENAME, serialised);
}

/**
 * Load cache from disk and parse.
 */

export function load() {
  if (process.env.BABEL_DISABLE_CACHE) return;

  process.on("exit", save);
  process.nextTick(save);

  if (!fs.existsSync(FILENAME)) return;

  try {
    data = JSON.parse(fs.readFileSync(FILENAME));
  } catch (err) {
    return;
  }
}

/**
 * Retrieve data from cache.
 */

export function get(): Object {
  return data;
}

/**
 * Clear the cache object.
 */

export function clear() {
  data = {};
}