const fs = require('fs');
const path = require('path');
const mkdirp = require('mkdirp');

const CONFIG_FILENAME = 'pkgcomp.json';

exports.read = (fileRoot, ident) => {
  const stats = fs.statSync(fileRoot);
  const filePath = path.join(fileRoot, CONFIG_FILENAME);

  // throw if pointing to a file
  if (stats.isFile()) throw new Error(`getData expects a directory, got a file; ${fileRoot}`);

  // create file if it's missing
  if (!stats.isDirectory()) {
    mkdirp.sync(fileRoot);
  }

  try {
    const data = JSON.parse(fs.readFileSync(filePath));
    return data[ident] || {};
  } catch (err) {
    if (err.code === 'ENOENT') {
      fs.writeFileSync(filePath, JSON.stringify({}));
      return {};
    }
    throw err;
  }
};

exports.write = (fileRoot, ident, payload) => {
  const filePath = path.join(fileRoot, CONFIG_FILENAME);
  const existingCache = JSON.parse(fs.readFileSync(filePath));

  // update the cache
  existingCache[ident] = payload;

  fs.writeFileSync(filePath, JSON.stringify(existingCache));
};