const fs = require('fs');
const os = require('os');
const npmName = require('npm-name');
const pify = require('pify');
const recast = require('recast');

const fileName = `${os.homedir()}/.hyper.js`;

let fileContents;
let parsedFile;
let plugins;
let localPlugins;

try {
  fileContents = fs.readFileSync(fileName, 'utf8');

  parsedFile = recast.parse(fileContents);

  const properties = parsedFile.program.body[0].expression.right.properties;
  plugins = properties.find(property => {
    return property.key.name === 'plugins';
  }).value.elements;

  localPlugins = properties.find(property => {
    return property.key.name === 'localPlugins';
  }).value.elements;
} catch (err) {
  if (err.code !== 'ENOENT') {
    // ENOENT === !exists()
    throw err;
  }
}

function exists() {
  return fileContents !== undefined;
}

function isInstalled(plugin, locally) {
  const array = locally ? localPlugins : plugins;
  if (array && Array.isArray(array)) {
    return array.find(entry => entry.value === plugin) !== undefined;
  }
  return false;
}

function save() {
  return pify(fs.writeFile)(fileName, recast.print(parsedFile).code, 'utf8');
}

function existsOnNpm(plugin) {
  plugin = plugin.split('#')[0].split('@')[0];
  return npmName(plugin).then(unavailable => {
    if (unavailable) {
      const err = new Error(`${plugin} not found on npm`);
      err.code = 'NOT_FOUND_ON_NPM';
      throw err;
    }
  });
}

function install(plugin, locally) {
  const array = locally ? localPlugins : plugins;
  return new Promise((resolve, reject) => {
    existsOnNpm(plugin)
      .then(() => {
        if (isInstalled(plugin, locally)) {
          return reject(`${plugin} is already installed`);
        }

        array.push(recast.types.builders.literal(plugin));
        save()
          .then(resolve)
          .catch(err => reject(err));
      })
      .catch(err => {
        if (err.code === 'NOT_FOUND_ON_NPM') {
          reject(err.message);
        } else {
          reject(err);
        }
      });
  });
}

function uninstall(plugin) {
  return new Promise((resolve, reject) => {
    if (!isInstalled(plugin)) {
      return reject(`${plugin} is not installed`);
    }

    const index = plugins.findIndex(entry => entry.value === plugin);
    plugins.splice(index, 1);
    save()
      .then(resolve)
      .catch(err => reject(err));
  });
}

function list() {
  if (Array.isArray(plugins)) {
    return plugins.map(plugin => plugin.value).join('\n');
  }
  return false;
}

module.exports.configPath = fileName;
module.exports.exists = exists;
module.exports.existsOnNpm = existsOnNpm;
module.exports.isInstalled = isInstalled;
module.exports.install = install;
module.exports.uninstall = uninstall;
module.exports.list = list;