diff2textv1.js

// Translates a Google diff-match-patch diff to an array of ottypes textv1 ops
// Pretty straight-forward!
module.exports = function (diff) {
  var ops = [];
  for(var i = 0; i < diff.length; i++) {
    var diffComp = diff[i];
    switch(diffComp[0]) {
      case -1: // DELETION
        ops.push({d:diffComp[1].length});
        break;
      case 0: // EQUALITY
        if (i != diff.length -1) { // ottypes doesn't like a skip op at the end
          ops.push(diffComp[1].length);
        }
      break;
        case 1: // INSERTION
        ops.push(diffComp[1]);
    }
  }
  return ops;
};

diff2textv1_test.js

var fmt = require('util').format;
var assert = require('assert');
var livedb = require('livedb');
var diff2textv1 = require('../lib/diff2textv1');
var Dmp = require('diff-match-patch');
var dmp = new Dmp();

function assertTransform(before, after) {
  var diff = dmp.diff_main(before, after);
  var ops = diff2textv1(diff);
  var data = {
    type: 'http://sharejs.org/types/textv1',
    data: before
  };
  var err = livedb.ot.apply(data, {op: ops});
  if (data.data != after) {
    console.error(before);
    console.error(after);
    console.error(diff);
    console.error(ops);
    if (err) throw new Error(err);
    assert.equal(data.data, after);
  }
}

function randomInt(range) {
  return Math.floor(Math.random() * range);
}

function randomText(length) {
  var text = "";
  var possible = "ABCDEFGH";

  for( var i=0; i < length; i++ ) {
    text += possible.charAt(randomInt(possible.length));
  }
  return text;
}

describe('diff2textv1', function () {
  it('handles insertion at end', function () {
    var before = 'Hello\n';
    var after  = 'Hello\nWorld\n';

    assertTransform(before, after);
  });

  it('handles deletion at end', function () {
    var before = 'Hello\nWorld\n';
    var after  = 'Hello\n';

    assertTransform(before, after);
  });

  it('handles deletion at beginning', function () {
    var before = 'Hello\nWorld\n';
    var after  = 'World\n';

    assertTransform(before, after);
  });

  it('handles complicated stuff', function () {
    var before = 'mouse';
    var after  = 'sofas';

    assertTransform(before, after);
  });

  // fuzzing
  for(var i = 0; i < 20; i++) {
    var before = randomText(randomInt(10));
    var after = randomText(randomInt(10));

    it(fmt("handles '%s' => '%s'", before, after), function () {
      assertTransform(before, after);
    });
  }
});