zeppelin/backbone/state.js

const fs = require('fs');
const location = './state'

if(!fs.existsSync(location)) {
  fs.mkdir(location, err => {
    if(err) { console.error(err); }
  });
}

function l (id) { return `${location}/${id}.json` }

function c (id) {
  let path = l(id);
  if(fs.existsSync(path)) {
    console.info(`[${id}] State already exists`);
  } else {
    fs.writeFile(path, JSON.stringify({}), err => {
      if(err) {
        console.error(err);
      } else {
        console.info(`[${id}] Created new state`);
      }
    });
  }
}

function r (id) {
  return new Promise((resolve, reject) => {
    let path = l(id);
    if(fs.existsSync(path)) {
      console.info(`[${id}] Reading existing state`);
      fs.readFile(path, (err, data) => {
        if(err) {
          console.error(err);
          reject(err);
        } else {
          console.info(`[${id}] Read state`);
          try {
            let state = JSON.parse(data);
            console.info(`[${id}] Deserialized state`);
            resolve(state);
          } catch(err) {
            reject(err);
          }
        }
      });
    } else {
      console.error(`[${id}] Failed to locate state`);
      reject(new Error('State not found.'));
    }
  });

}

function u (id, state) {
  let path = l(id);
  if(fs.existsSync(path)) {
    fs.writeFile(path, JSON.stringify(state), err => {
      if(err) {
        console.error(err);
      } else {
        console.info(`[${id}] Updated state`);
      }
    });
  } else {
    console.error(`[${id}] Failed to locate state`);
  }
}

function d (id) {
  let path = l(id);
  if(fs.existsSync(path)) {
    fs.unlink(path, err=> {
      if(err) {
        console.error(err);
      } else {
        console.info(`[${id}] Removed state`);
      }
    });
  } else {
    console.error(`[${id}] Failed to locate state`);
  }
}

module.exports = {
  create: c,
  read: r,
  update: u,
  delete: d
}