gun/lib/level.js

// CAUTION: This adapter does NOT handle encoding. an encoding mechanism like the encoding-down package will need to be included
// Based on localStorage adapter in 05349a5

var Gun   = ('undefined' !== typeof window) ? window.Gun : require('../gun');
var debug = false;

Gun.on('opt', function(ctx) {
  var opt = ctx.opt;
  var ev  = this.to;

  if (debug) debug.emit('create');
  if (ctx.once) return ev.next(ctx);

  // Check if the given 'level' argument implements all the components we need
  // Intentionally doesn't check for levelup explicitly, to allow different handlers implementing the same api
  if (
    (!opt.level) ||
    ('object' !== typeof opt.level) ||
    ('function' !== typeof opt.level.get) ||
    ('function' !== typeof opt.level.put)
  ) {
    return;
  }

  ctx.on('put', function(msg) {
   this.to.next(msg);

    // Extract data from message
    var put   = msg.put;
    var soul  = put['#'];
    var key   = put['.'];
    var val   = put[':'];
    var state = put['>'];

    if (debug) debug.emit('put', soul, val);

    // Fetch previous version
    opt.level.get(soul, function(err, data) {
      if (err && (err.name === 'NotFoundError')) err = undefined;
      if (debug && err) debug.emit('error', err);
      if (err) return;

      // Unclear required transformation
      data = Gun.state.ify(data, key, state, val, soul);

      // Write into storage
      opt.level.put(soul, data, function(err) {
        if (err) return;
        if (debug) debug.emit('put', soul, val);

        // Bail if message was an ack
        if (msg['@']) return;

        // Send ack back
        ctx.on('in', {
          '@' : msg['@'],
          ok  : 0,
        });
      });
    });
  });

  ctx.on('get', function(msg) {
    this.to.next(msg);

    // Extract soul from message
    var lex = msg.get;
    if (!lex || !(soul = lex['#'])) return;
    var has = lex['.'];

    if (debug) debug.emit('get', soul);

    // Fetch data from storage
    opt.level.get(soul, function(err, data) {
      if (err) return;

      // Another unclear transformation
      if (data && has) {
        data = Gun.state.to(data, has);
      }

      // Emulate incoming ack
      ctx.on('in', {
        '@' : msg['#'],
        put : Gun.graph.node(data),
      });
    });
  });

});

// Export debug interface
if ('undefined' === typeof window) {
  var EventEmitter = require('events').EventEmitter;
  module.exports = debug = new EventEmitter();
}