var Change;
var TestModel;

describe('Change', function(){
  beforeEach(function() {
    var memory = loopback.createDataSource({
      connector: loopback.Memory
    });
    TestModel = loopback.DataModel.extend('chtest', {}, {
      trackChanges: true
    });
    this.modelName = TestModel.modelName;
    TestModel.attachTo(memory);
    Change = TestModel.getChangeModel();
  });

  beforeEach(function(done) {
    var test = this;
    test.data = {
      foo: 'bar'
    };
    TestModel.create(test.data, function(err, model) {
      if(err) return done(err);
      test.model = model;
      test.modelId = model.id;
      test.revisionForModel = Change.revisionForInst(model);
      done();
    });
  });

  describe('change.id', function () {
    it('should be a hash of the modelName and modelId', function () {
      var change = new Change({
        rev: 'abc',
        modelName: 'foo',
        modelId: 'bar'
      });

      var hash = Change.hash([change.modelName, change.modelId].join('-'));

      assert.equal(change.id, hash);
    });
  });

  describe('Change.rectifyModelChanges(modelName, modelIds, callback)', function () {
    describe('using an existing untracked model', function () {
      beforeEach(function(done) {
        var test = this;
        Change.rectifyModelChanges(this.modelName, [this.modelId], function(err, trackedChanges) {
          if(err) return done(err);
          test.trackedChanges = trackedChanges;
          done();
        });
      });

      it('should create an entry', function () {
        assert(Array.isArray(this.trackedChanges));
        assert.equal(this.trackedChanges[0].modelId, this.modelId);
      });

      it('should only create one change', function (done) {
        Change.count(function(err, count) {
          assert.equal(count, 1);
          done();
        });
      });
    });
  });

  describe('Change.findOrCreate(modelName, modelId, callback)', function () {
    
    describe('when a change doesnt exist', function () {
      beforeEach(function(done) {
        var test = this;
        Change.findOrCreate(this.modelName, this.modelId, function(err, result) {
          if(err) return done(err);
          test.result = result;
          done();
        });
      });

      it('should create an entry', function (done) {
        var test = this;
        Change.findById(this.result.id, function(err, change) {
          assert.equal(change.id, test.result.id);
          done();
        });
      });
    });

    describe('when a change does exist', function () {
      beforeEach(function(done) {
        var test = this;
        Change.create({
          modelName: test.modelName,
          modelId: test.modelId
        }, function(err, change) {
          test.existingChange = change;
          done();
        });
      });

      beforeEach(function(done) {
        var test = this;
        Change.findOrCreate(this.modelName, this.modelId, function(err, result) {
          if(err) return done(err);
          test.result = result;
          done();
        });
      });

      it('should find the entry', function (done) {
        var test = this;      
        assert.equal(test.existingChange.id, test.result.id);
        done();
      });
    });
  });

  describe('change.rectify(callback)', function () {
    it('should create a new change with the correct revision', function (done) {
      var test = this;
      var change = new Change({
        modelName: this.modelName,
        modelId: this.modelId
      });

      change.rectify(function(err, ch) {
        assert.equal(ch.rev, test.revisionForModel);
        done();
      });
    });
  });

  describe('change.currentRevision(callback)', function () {
    it('should get the correct revision', function (done) {
      var test = this;
      var change = new Change({
        modelName: this.modelName,
        modelId: this.modelId
      });

      change.currentRevision(function(err, rev) {
        assert.equal(rev, test.revisionForModel);
        done();
      });
    });
  });

  describe('Change.hash(str)', function () {
    // todo(ritch) test other hashing algorithms
    it('should hash the given string', function () {
      var str = 'foo';
      var hash = Change.hash(str);
      assert(hash !== str);
      assert(typeof hash === 'string');
    });
  });

  describe('Change.revisionForInst(inst)', function () {
    it('should return the same revision for the same data', function () {
      var a = {
        b: {
          b: ['c', 'd'],
          c: ['d', 'e']
        }
      };
      var b = {
        b: {
          c: ['d', 'e'],
          b: ['c', 'd']
        }
      };

      var aRev = Change.revisionForInst(a);
      var bRev = Change.revisionForInst(b);
      assert.equal(aRev, bRev);
    });
  });

  describe('change.type()', function () {
    it('CREATE', function () {
      var change = new Change({
        rev: this.revisionForModel
      });
      assert.equal(Change.CREATE, change.type());
    });
    it('UPDATE', function () {
      var change = new Change({
        rev: this.revisionForModel,
        prev: this.revisionForModel
      });
      assert.equal(Change.UPDATE, change.type());
    });
    it('DELETE', function () {
      var change = new Change({
        prev: this.revisionForModel
      });
      assert.equal(Change.DELETE, change.type());
    });
    it('UNKNOWN', function () {
      var change = new Change();
      assert.equal(Change.UNKNOWN, change.type());
    });
  });

  describe('change.getModelCtor()', function () {
    it('should get the correct model class', function () {
      var change = new Change({
        modelName: this.modelName
      });

      assert.equal(change.getModelCtor(), TestModel);
    });
  });

  describe('change.equals(otherChange)', function () {
    it('should return true when the change is equal', function () {
      var change = new Change({
        rev: this.revisionForModel
      });

      var otherChange = new Change({
        rev: this.revisionForModel
      });

      assert.equal(change.equals(otherChange), true);
    });

    it('should return true when both changes are deletes', function () {
      var REV = 'foo';
      var change = new Change({
        rev: null,
        prev: REV,
      });

      var otherChange = new Change({
        rev: undefined,
        prev: REV
      });

      assert.equal(change.type(), Change.DELETE);
      assert.equal(otherChange.type(), Change.DELETE);

      assert.equal(change.equals(otherChange), true);
    });
  });

  describe('change.isBasedOn(otherChange)', function () {
    it('should return true when the change is based on the other', function () {
      var change = new Change({
        prev: this.revisionForModel
      });

      var otherChange = new Change({
        rev: this.revisionForModel
      });

      assert.equal(change.isBasedOn(otherChange), true);
    });
  });

  describe('Change.diff(modelName, since, remoteChanges, callback)', function () {
    beforeEach(function(done) {
      Change.create([
        {rev: 'foo', modelName: this.modelName, modelId: 9, checkpoint: 1},
        {rev: 'bar', modelName: this.modelName, modelId: 10, checkpoint: 1},
        {rev: 'bat', modelName: this.modelName, modelId: 11, checkpoint: 1},
      ], done);
    });

    it('should return delta and conflict lists', function (done) {
      var remoteChanges = [
        // an update => should result in a delta
        {rev: 'foo2', prev: 'foo', modelName: this.modelName, modelId: 9, checkpoint: 1},
        // no change => should not result in a delta / conflict
        {rev: 'bar', prev: 'bar', modelName: this.modelName, modelId: 10, checkpoint: 1},
        // a conflict => should result in a conflict
        {rev: 'bat2', prev: 'bat0', modelName: this.modelName, modelId: 11, checkpoint: 1},
      ];

      Change.diff(this.modelName, 0, remoteChanges, function(err, diff) {
        assert.equal(diff.deltas.length, 1);
        assert.equal(diff.conflicts.length, 1);
        done();
      });
    });
  });
});