goldilocks.js/lib/storage.js

'use strict';

var PromiseA = require('bluebird');
var path = require('path');
var fs = PromiseA.promisifyAll(require('fs'));

module.exports.create = function (deps, conf) {
  var hrIds = require('human-readable-ids').humanReadableIds;
  var scmp = require('scmp');
  var storageDir = path.join(__dirname, '..', 'var');

  function read(fileName) {
    return fs.readFileAsync(path.join(storageDir, fileName))
    .then(JSON.parse, function (err) {
      if (err.code === 'ENOENT') {
        return {};
      }
      throw err;
    });
  }
  function write(fileName, obj) {
    return fs.mkdirAsync(storageDir).catch(function (err) {
      if (err.code !== 'EEXIST') {
        console.error('failed to mkdir', storageDir, err.toString());
      }
    }).then(function () {
      return fs.writeFileAsync(path.join(storageDir, fileName), JSON.stringify(obj), 'utf8');
    });
  }

  var owners = {
    _filename: 'owners.json'
  , all: function () {
      return read(this._filename).then(function (owners) {
        return Object.keys(owners).map(function (id) {
          var owner = owners[id];
          owner.id = id;
          return owner;
        });
      });
    }
  , get: function (id) {
      // While we could directly read the owners file and access the id directly from
      // the resulting object I'm not sure of the details of how the object key lookup
      // works or whether that would expose us to timing attacks.
      // See https://codahale.com/a-lesson-in-timing-attacks/
      return this.all().then(function (owners) {
        return owners.filter(function (owner) {
          return scmp(id, owner.id);
        })[0];
      });
    }
  , exists: function (id) {
      return this.get(id).then(function (owner) {
        return !!owner;
      });
    }
  , set: function (id, obj) {
      var self = this;
      return read(self._filename).then(function (owners) {
        obj.id = id;
        owners[id] = obj;
        return write(self._filename, owners);
      });
    }
  };

  var config = {
    save: function (changes) {
      deps.messenger.send({
        type: 'com.daplie.goldilocks/config'
      , changes: changes
      });
    }
  };

  var mdnsId = {
    _filename: 'mdns-id'
  , get: function () {
      var self = this;
      return read("mdns-id").then(function (result) {
        if (typeof result !== 'string') {
          throw new Error('mDNS ID not present');
        }
        return result;
      }).catch(function () {
        return self.set(hrIds.random());
      });
    }

  , set: function (value) {
      var self = this;
      return write(self._filename, value).then(function () {
        return self.get();
      });
    }
  };

  return {
    owners: owners
  , config: config
  , mdnsId: mdnsId
  };
};