historyview.js

define(['d3'], function () {
    "use strict";

    var REG_MARKER_END = 'url(#triangle)',
        MERGE_MARKER_END = 'url(#brown-triangle)',
        FADED_MARKER_END = 'url(#faded-triangle)',

        preventOverlap,
        applyBranchlessClass,
        cx, cy, fixCirclePosition,
        px1, py1, fixPointerStartPosition,
        px2, py2, fixPointerEndPosition,
        fixIdPosition, tagY;

    preventOverlap = function preventOverlap(commit, view) {
        var commitData = view.commitData,
            baseLine = view.baseLine,
            shift = view.commitRadius * 4.5,
            overlapped = null;

        for (var i = 0; i < commitData.length; i++) {
            var c = commitData[i];
            if (c.cx === commit.cx && c.cy === commit.cy && c !== commit) {
                overlapped = c;
                break;
            }
        }

        if (overlapped) {
            var oParent = view.getCommit(overlapped.parent),
                parent = view.getCommit(commit.parent);

            if (overlapped.cy < baseLine) {
                overlapped = oParent.cy < parent.cy ? overlapped : commit;
                overlapped.cy -= shift;
            } else {
                overlapped = oParent.cy > parent.cy ? overlapped : commit;
                overlapped.cy += shift;
            }

            preventOverlap(overlapped, view);
        }
    };

    applyBranchlessClass = function (selection) {
        if (selection.empty()) {
            return;
        }

        selection.classed('branchless', function (d) {
            return d.branchless;
        });

        if (selection.classed('commit-pointer')) {
            selection.attr('marker-end', function (d) {
                return d.branchless ? FADED_MARKER_END : REG_MARKER_END;
            });
        } else if (selection.classed('merge-pointer')) {
            selection.attr('marker-end', function (d) {
                return d.branchless ? FADED_MARKER_END : MERGE_MARKER_END;
            });
        }
    };

    cx = function (commit, view) {
        var parent = view.getCommit(commit.parent),
            parentCX = parent.cx;

        if (typeof commit.parent2 === 'string') {
            var parent2 = view.getCommit(commit.parent2);

            parentCX = parent.cx > parent2.cx ? parent.cx : parent2.cx;
        }

        return parentCX + (view.commitRadius * 4.5);
    };

    cy = function (commit, view) {
        var parent = view.getCommit(commit.parent),
            parentCY = parent.cy || cy(parent, view),
            baseLine = view.baseLine,
            shift = view.commitRadius * 4.5,
            branches = [], // count the existing branches
            branchIndex = 0;

        for (var i = 0; i < view.commitData.length; i++) {
            var d = view.commitData[i];

            if (d.parent === commit.parent) {
                branches.push(d.id);
            }
        }

        branchIndex = branches.indexOf(commit.id);

        if (commit.isNoFFBranch === true) {
            branchIndex++;
        }
        if (commit.isNoFFCommit === true) {
            branchIndex--;
        }

        if (parentCY === baseLine) {
            var direction = 1;
            for (var bi = 0; bi < branchIndex; bi++) {
                direction *= -1;
            }

            shift *= Math.ceil(branchIndex / 2);

            return parentCY + (shift * direction);
        }

        if (parentCY < baseLine) {
            return parentCY - (shift * branchIndex);
        } else if (parentCY > baseLine) {
            return parentCY + (shift * branchIndex);
        }
    };

    fixCirclePosition = function (selection) {
        selection
            .attr('cx', function (d) {
                return d.cx;
            })
            .attr('cy', function (d) {
                return d.cy;
            });
    };

    // calculates the x1 point for commit pointer lines
    px1 = function (commit, view, pp) {
        pp = pp || 'parent';

        var parent = view.getCommit(commit[pp]),
            startCX = commit.cx,
            diffX = startCX - parent.cx,
            diffY = parent.cy - commit.cy,
            length = Math.sqrt((diffX * diffX) + (diffY * diffY));

        return startCX - (view.pointerMargin * (diffX / length));
    };

    // calculates the y1 point for commit pointer lines
    py1 = function (commit, view, pp) {
        pp = pp || 'parent';

        var parent = view.getCommit(commit[pp]),
            startCY = commit.cy,
            diffX = commit.cx - parent.cx,
            diffY = parent.cy - startCY,
            length = Math.sqrt((diffX * diffX) + (diffY * diffY));

        return startCY + (view.pointerMargin * (diffY / length));
    };

    fixPointerStartPosition = function (selection, view) {
        selection.attr('x1', function (d) {
            return px1(d, view);
        }).attr('y1', function (d) {
            return py1(d, view);
        });
    };

    px2 = function (commit, view, pp) {
        pp = pp || 'parent';

        var parent = view.getCommit(commit[pp]),
            endCX = parent.cx,
            diffX = commit.cx - endCX,
            diffY = parent.cy - commit.cy,
            length = Math.sqrt((diffX * diffX) + (diffY * diffY));

        return endCX + (view.pointerMargin * 1.2 * (diffX / length));
    };

    py2 = function (commit, view, pp) {
        pp = pp || 'parent';

        var parent = view.getCommit(commit[pp]),
            endCY = parent.cy,
            diffX = commit.cx - parent.cx,
            diffY = endCY - commit.cy,
            length = Math.sqrt((diffX * diffX) + (diffY * diffY));

        return endCY - (view.pointerMargin * 1.2 * (diffY / length));
    };

    fixPointerEndPosition = function (selection, view) {
        selection.attr('x2', function (d) {
            return px2(d, view);
        }).attr('y2', function (d) {
            return py2(d, view);
        });
    };

    fixIdPosition = function (selection, view, delta) {
        selection.attr('x', function (d) {
            return d.cx;
        }).attr('y', function (d) {
            return d.cy + view.commitRadius + delta;
        });
    };

    tagY = function tagY(t, view) {
        var commit = view.getCommit(t.commit),
            commitCY = commit.cy,
            tags = commit.tags,
            tagIndex = tags.indexOf(t.name);

        if (tagIndex === -1) {
            tagIndex = tags.length;
        }

        if (commitCY < (view.baseLine)) {
            return commitCY - 45 - (tagIndex * 25);
        } else {
            return commitCY + 50 + (tagIndex * 25);
        }
    };

    /**
     * @class HistoryView
     * @constructor
     */
    function HistoryView(config) {
        var commitData = config.commitData || [],
            commit;

        for (var i = 0; i < commitData.length; i++) {
            commit = commitData[i];
            !commit.parent && (commit.parent = 'initial');
            !commit.tags && (commit.tags = []);
        }

        this.name = config.name || 'UnnamedHistoryView';
        this.commitData = commitData;

        this.branches = [];
        this.currentBranch = config.currentBranch || 'master';

        this.width = config.width;
        this.height = config.height || 400;
        this.orginalBaseLine = config.baseLine;
        this.baseLine = this.height * (config.baseLine || 0.6);

        this.commitRadius = config.commitRadius || 20;
        this.pointerMargin = this.commitRadius * 1.3;

        this.isRemote = typeof config.remoteName === 'string';
        this.remoteName = config.remoteName;

        this.initialCommit = {
            id: 'initial',
            parent: null,
            cx: -(this.commitRadius * 2),
            cy: this.baseLine
        };
    }

    HistoryView.generateId = function () {
        return Math.floor((1 + Math.random()) * 0x10000000).toString(16).substring(1);
    };

    HistoryView.prototype = {
        /**
         * @method getCommit
         * @param ref {String} the id or a tag name that refers to the commit
         * @return {Object} the commit datum object
         */
        getCommit: function getCommit(ref) {
            var commitData = this.commitData,
                headMatcher = /HEAD(\^+)/.exec(ref),
                matchedCommit = null;

            if (ref === 'initial') {
                return this.initialCommit;
            }

            if (headMatcher) {
                ref = 'HEAD';
            }

            for (var i = 0; i < commitData.length; i++) {
                var commit = commitData[i];
                if (commit === ref) {
                    matchedCommit = commit;
                    break;
                }

                if (commit.id === ref) {
                    matchedCommit = commit;
                    break;
                }

                var matchedTag = function() { 
                    for (var j = 0; j < commit.tags.length; j++) {
                        var tag = commit.tags[j];
                        if (tag === ref) {
                            matchedCommit = commit;
                            return true;
                        }
                        
                        if (tag.indexOf('[') === 0 && tag.indexOf(']') === tag.length - 1) {
                            tag = tag.substring(1, tag.length - 1);
                        }
                        if (tag === ref) {
                            matchedCommit = commit;
                            return true;
                        }
                    }
                }();
                if (matchedTag === true) {
                    break;
                }
            }

            if (headMatcher && matchedCommit) {
                for (var h = 0; h < headMatcher[1].length; h++) {
                    matchedCommit = getCommit.call(this, matchedCommit.parent);
                }
            }

            return matchedCommit;
        },

        /**
         * @method getCircle
         * @param ref {String} the id or a tag name that refers to the commit
         * @return {d3 Selection} the d3 selected SVG circle
         */
        getCircle: function (ref) {
            var circle = this.svg.select('#' + this.name + '-' + ref),
                commit;

            if (circle && !circle.empty()) {
                return circle;
            }

            commit = this.getCommit(ref);

            if (!commit) {
                return null;
            }

            return this.svg.select('#' + this.name + '-' + commit.id);
        },

        getCircles: function () {
            return this.svg.selectAll('circle.commit');
        },

        /**
         * @method render
         * @param container {String} selector for the container to render the SVG into
         */
        render: function (container) {
            var svgContainer, svg;

            svgContainer = container.append('div')
                .classed('svg-container', true)
                .classed('remote-container', this.isRemote);
                
            svg = svgContainer.append('svg:svg');

            svg.attr('id', this.name)
                .attr('width', this.width)
                .attr('height', this.height);

            if (this.isRemote) {
                svg.append('svg:text')
                    .classed('remote-name-display', true)
                    .text(this.remoteName)
                    .attr('x', 10)
                    .attr('y', 25);
            } else {
                svg.append('svg:text')
                    .classed('remote-name-display', true)
                    .text('Local Repository')
                    .attr('x', 10)
                    .attr('y', 25);

                svg.append('svg:text')
                    .classed('current-branch-display', true)
                    .attr('x', 10)
                    .attr('y', 45);
            }

            this.svgContainer = svgContainer;
            this.svg = svg;
            this.arrowBox = svg.append('svg:g').classed('pointers', true);
            this.commitBox = svg.append('svg:g').classed('commits', true);
            this.tagBox = svg.append('svg:g').classed('tags', true);

            this.renderCommits();

            this._setCurrentBranch(this.currentBranch);
        },

        destroy: function () {
            this.svg.remove();
            this.svgContainer.remove();
            clearInterval(this.refreshSizeTimer);

            for (var prop in this) {
                if (this.hasOwnProperty(prop)) {
                    this[prop] = null;
                }
            }
        },

        _calculatePositionData: function () {
            for (var i = 0; i < this.commitData.length; i++) {
                var commit = this.commitData[i];
                commit.cx = cx(commit, this);
                commit.cy = cy(commit, this);
                preventOverlap(commit, this);
            }
        },
        
        _resizeSvg: function() {
            var ele = document.getElementById(this.svg.node().id);
            var container = ele.parentNode;
            var currentWidth = ele.offsetWidth;
            var newWidth;

            if (ele.getBBox().width > container.offsetWidth)
                newWidth = Math.round(ele.getBBox().width);
            else
                newWidth = container.offsetWidth - 5;

            if (currentWidth != newWidth) {
                this.svg.attr('width', newWidth);
                container.scrollLeft = container.scrollWidth;
            }
        },

        renderCommits: function () {
            if (typeof this.height === 'string' && this.height.indexOf('%') >= 0) {
                var perc = this.height.substring(0, this.height.length - 1) / 100.0;
                var baseLineCalcHeight = Math.round(this.svg.node().parentNode.offsetHeight * perc) - 65;
                var newBaseLine = Math.round(baseLineCalcHeight * (this.originalBaseLine || 0.6));
                if (newBaseLine !== this.baseLine) {
                    this.baseLine = newBaseLine;
                    this.initialCommit.cy = newBaseLine;
                    this.svg.attr('height', baseLineCalcHeight);
                }
            }
            this._calculatePositionData();
            this._calculatePositionData(); // do this twice to make sure
            this._renderCircles();
            this._renderPointers();
            this._renderMergePointers();
            this._renderIdLabels();
            this._resizeSvg();
            this.checkout(this.currentBranch);
        },

        _renderCircles: function () {
            var view = this,
                existingCircles,
                newCircles;

            existingCircles = this.commitBox.selectAll('circle.commit')
                .data(this.commitData, function (d) { return d.id; })
                .attr('id', function (d) {
                    return view.name + '-' + d.id;
                })
                .classed('reverted', function (d) {
                    return d.reverted;
                })
                .classed('rebased', function (d) {
                    return d.rebased;
                });

            existingCircles.transition()
                .duration(500)
                .call(fixCirclePosition);

            newCircles = existingCircles.enter()
                .append('svg:circle')
                .attr('id', function (d) {
                    return view.name + '-' + d.id;
                })
                .classed('commit', true)
                .classed('merge-commit', function (d) {
                    return typeof d.parent2 === 'string';
                })
                .call(fixCirclePosition)
                .attr('r', 1)
                .transition("inflate")
                .duration(500)
                .attr('r', this.commitRadius);

        },

        _renderPointers: function () {
            var view = this,
                existingPointers,
                newPointers;

            existingPointers = this.arrowBox.selectAll('line.commit-pointer')
                .data(this.commitData, function (d) { return d.id; })
                .attr('id', function (d) {
                    return view.name + '-' + d.id + '-to-' + d.parent;
                });

            existingPointers.transition()
                .duration(500)
                .call(fixPointerStartPosition, view)
                .call(fixPointerEndPosition, view);

            newPointers = existingPointers.enter()
                .append('svg:line')
                .attr('id', function (d) {
                    return view.name + '-' + d.id + '-to-' + d.parent;
                })
                .classed('commit-pointer', true)
                .call(fixPointerStartPosition, view)
                .attr('x2', function () { return d3.select(this).attr('x1'); })
                .attr('y2', function () {  return d3.select(this).attr('y1'); })
                .attr('marker-end', REG_MARKER_END)
                .transition()
                .duration(500)
                .call(fixPointerEndPosition, view);
        },

        _renderMergePointers: function () {
            var view = this,
                mergeCommits = [],
                existingPointers, newPointers;

            for (var i = 0; i < this.commitData.length; i++) {
                var commit = this.commitData[i];
                if (typeof commit.parent2 === 'string') {
                    mergeCommits.push(commit);
                }
            }

            existingPointers = this.arrowBox.selectAll('polyline.merge-pointer')
                .data(mergeCommits, function (d) { return d.id; })
                .attr('id', function (d) {
                    return view.name + '-' + d.id + '-to-' + d.parent2;
                });

            existingPointers.transition().duration(500)
                .attr('points', function (d) {
                    var p1 = px1(d, view, 'parent2') + ',' + py1(d, view, 'parent2'),
                        p2 = px2(d, view, 'parent2') + ',' + py2(d, view, 'parent2');

                    return [p1, p2].join(' ');
                });

            newPointers = existingPointers.enter()
                .append('svg:polyline')
                .attr('id', function (d) {
                    return view.name + '-' + d.id + '-to-' + d.parent2;
                })
                .classed('merge-pointer', true)
                .attr('points', function (d) {
                    var x1 = px1(d, view, 'parent2'),
                        y1 = py1(d, view, 'parent2'),
                        p1 = x1 + ',' + y1;

                    return [p1, p1].join(' ');
                })
                .attr('marker-end', MERGE_MARKER_END)
                .transition()
                .duration(500)
                .attr('points', function (d) {
                    var points = d3.select(this).attr('points').split(' '),
                        x2 = px2(d, view, 'parent2'),
                        y2 = py2(d, view, 'parent2');

                    points[1] = x2 + ',' + y2;
                    return points.join(' ');
                });
        },

        _renderIdLabels: function () {
            this._renderText('id-label', function (d) { return d.id + '..'; }, 14);
            this._renderText('message-label', function (d) { return d.message; }, 24);
        },

        _renderText: function(className, getText, delta) {
            var view = this,
                existingTexts,
                newtexts;

            existingTexts = this.commitBox.selectAll('text.' + className)
                .data(this.commitData, function (d) { return d.id; })
                .text(getText);

            existingTexts.transition().call(fixIdPosition, view, delta);

            newtexts = existingTexts.enter()
                .insert('svg:text', ':first-child')
                .classed(className, true)
                .text(getText)
                .call(fixIdPosition, view, delta);
        },

        _parseTagData: function () {
            var tagData = [], i,
                headCommit = null;

            for (i = 0; i < this.commitData.length; i++) {
                var c = this.commitData[i];

                for (var t = 0; t < c.tags.length; t++) {
                    var tagName = c.tags[t];
                    if (tagName.toUpperCase() === 'HEAD') {
                        headCommit = c;
                    } else if (this.branches.indexOf(tagName) === -1) {
                        this.branches.push(tagName);
                    }

                    tagData.push({name: tagName, commit: c.id});
                }
            }

            if (!headCommit) {
                headCommit = this.getCommit(this.currentBranch);
                headCommit.tags.push('HEAD');
                tagData.push({name: 'HEAD', commit: headCommit.id});
            }

            // find out which commits are not branchless


            return tagData;
        },

        _markBranchlessCommits: function () {
            var branch, commit, parent, parent2, c, b;

            // first mark every commit as branchless
            for (c = 0; c < this.commitData.length; c++) {
                this.commitData[c].branchless = true;
            }

            for (b = 0; b < this.branches.length; b++) {
                branch = this.branches[b];
                if (branch.indexOf('/') === -1) {
                    commit = this.getCommit(branch);
                    parent = this.getCommit(commit.parent);
                    parent2 = this.getCommit(commit.parent2);

                    commit.branchless = false;

                    while (parent) {
                        parent.branchless = false;
                        parent = this.getCommit(parent.parent);
                    }

                    // just in case this is a merge commit
                    while (parent2) {
                        parent2.branchless = false;
                        parent2 = this.getCommit(parent2.parent);
                    }
                }
            }

            this.svg.selectAll('circle.commit').call(applyBranchlessClass);
            this.svg.selectAll('line.commit-pointer').call(applyBranchlessClass);
            this.svg.selectAll('polyline.merge-pointer').call(applyBranchlessClass);
        },

        renderTags: function () {
            var view = this,
                tagData = this._parseTagData(),
                existingTags, newTags;

            existingTags = this.tagBox.selectAll('g.branch-tag')
                .data(tagData, function (d) { return d.name; });

            existingTags.exit().remove();

            existingTags.select('rect')
                .transition()
                .duration(500)
                .attr('y', function (d) { return tagY(d, view); })
                .attr('x', function (d) {
                    var commit = view.getCommit(d.commit),
                        width = Number(d3.select(this).attr('width'));

                    return commit.cx - (width / 2);
                });

            existingTags.select('text')
                .transition()
                .duration(500)
                .attr('y', function (d) { return tagY(d, view) + 14; })
                .attr('x', function (d) {
                    var commit = view.getCommit(d.commit);
                    return commit.cx;
                });

            newTags = existingTags.enter()
                .append('g')
                .attr('class', function (d) {
                    var classes = 'branch-tag';
                    if (d.name.indexOf('[') === 0 && d.name.indexOf(']') === d.name.length - 1) {
                        classes += ' git-tag';
                    } else if (d.name.indexOf('/') >= 0) {
                        classes += ' remote-branch';
                    } else if (d.name.toUpperCase() === 'HEAD') {
                        classes += ' head-tag';
                    }
                    return classes;
                });

            newTags.append('svg:rect')
                .attr('width', function (d) {
                    return (d.name.length * 6) + 10;
                })
                .attr('height', 20)
                .attr('y', function (d) { return tagY(d, view); })
                .attr('x', function (d) {
                    var commit = view.getCommit(d.commit),
                        width = Number(d3.select(this).attr('width'));

                    return commit.cx - (width / 2);
                });

            newTags.append('svg:text')
                .text(function (d) {
                    if (d.name.indexOf('[') === 0 && d.name.indexOf(']') === d.name.length - 1)
                        return d.name.substring(1, d.name.length - 1); 
                    return d.name; 
                })
                .attr('y', function (d) {
                    return tagY(d, view) + 14;
                })
                .attr('x', function (d) {
                    var commit = view.getCommit(d.commit);
                    return commit.cx;
                });

            this._markBranchlessCommits();
        },

        _setCurrentBranch: function (branch) {
            var display = this.svg.select('text.current-branch-display'),
                text = 'Current Branch: ';

            if (branch && branch.indexOf('/') === -1) {
                text += branch;
                this.currentBranch = branch;
            } else {
                text += ' DETACHED HEAD';
                this.currentBranch = null;
            }

            display.text(text);
        },

        moveTag: function (tag, ref) {
            var currentLoc = this.getCommit(tag),
                newLoc = this.getCommit(ref);

            if (currentLoc) {
                currentLoc.tags.splice(currentLoc.tags.indexOf(tag), 1);
            }

            newLoc.tags.push(tag);
            return this;
        },

        /**
         * @method isAncestor
         * @param ref1
         * @param ref2
         * @return {Boolean} whether or not ref1 is an ancestor of ref2
         */
        isAncestor: function isAncestor(ref1, ref2) {
            var currentCommit = this.getCommit(ref1),
                targetTree = this.getCommit(ref2),
                inTree = false,
                additionalTrees = [];

            if (!currentCommit) {
                return false;
            }

            while (targetTree) {
                if (targetTree.id === currentCommit.id) {
                    inTree = true;
                    targetTree = null;
                } else {
                    if (targetTree.parent2) {
                        additionalTrees.push(targetTree.parent2);
                    }
                    targetTree = this.getCommit(targetTree.parent);
                }
            }

            if (inTree) {
                return true;
            }

            for (var i = 0; i < additionalTrees.length; i++) {
                inTree = isAncestor.call(this, currentCommit, additionalTrees[i]);
                if (inTree) break;
            }

            return inTree;
        },

        commit: function (commit, message) {
            commit = commit || {};

            !commit.id && (commit.id = HistoryView.generateId());
            !commit.tags && (commit.tags = []);

            commit.message = message;
            if (!commit.parent) {
                if (!this.currentBranch) {
                    throw new Error('Not a good idea to make commits while in a detached HEAD state.');
                }

                commit.parent = this.getCommit(this.currentBranch).id;
            }

            this.commitData.push(commit);
            this.moveTag(this.currentBranch, commit.id);

            this.renderCommits();

            this.checkout(this.currentBranch);
            return this;
        },

        branch: function (name) {
            if (!name || name.trim() === '') {
                throw new Error('You need to give a branch name.');
            }

            if (name === 'HEAD') {
                throw new Error('You cannot name your branch "HEAD".');
            }

            if (name.indexOf(' ') > -1) {
                throw new Error('Branch names cannot contain spaces.');
            }

            if (this.branches.indexOf(name) > -1) {
                throw new Error('Branch "' + name + '" already exists.');
            }

            this.getCommit('HEAD').tags.push(name);
            this.renderTags();
            return this;
        },

        tag: function (name) {
            this.branch('[' + name + ']');
        },

        deleteBranch: function (name) {
            var branchIndex,
                commit;

            if (!name || name.trim() === '') {
                throw new Error('You need to give a branch name.');
            }

            if (name === this.currentBranch) {
                throw new Error('Cannot delete the currently checked-out branch.');
            }

            branchIndex = this.branches.indexOf(name);

            if (branchIndex === -1) {
                throw new Error('That branch doesn\'t exist.');
            }

            this.branches.splice(branchIndex, 1);
            commit = this.getCommit(name);
            branchIndex = commit.tags.indexOf(name);

            if (branchIndex > -1) {
                commit.tags.splice(branchIndex, 1);
            }

            this.renderTags();
        },

        checkout: function (ref) {
            var commit = this.getCommit(ref);

            if (!commit) {
                throw new Error('Cannot find commit: ' + ref);
            }

            var previousHead = this.getCircle('HEAD'),
                newHead = this.getCircle(commit.id);

            if (previousHead && !previousHead.empty()) {
                previousHead.classed('checked-out', false);
            }

            this._setCurrentBranch(ref === commit.id ? null : ref);
            this.moveTag('HEAD', commit.id);
            this.renderTags();

            newHead.classed('checked-out', true);

            return this;
        },

        reset: function (ref) {
            var commit = this.getCommit(ref);

            if (!commit) {
                throw new Error('Cannot find ref: ' + ref);
            }

            if (this.currentBranch) {
                this.moveTag(this.currentBranch, commit.id);
                this.checkout(this.currentBranch);
            } else {
                this.checkout(commit.id);
            }

            return this;
        },

        revert: function (ref) {
            var commit = this.getCommit(ref);

            if (!commit) {
                throw new Error('Cannot find ref: ' + ref);
            }

            if (this.isAncestor(commit, 'HEAD')) {
                commit.reverted = true;
                this.commit({reverts: commit.id});
            } else {
                throw new Error(ref + 'is not an ancestor of HEAD.');
            }
        },

        fastForward: function (ref) {
            var targetCommit = this.getCommit(ref);

            if (this.currentBranch) {
                this.moveTag(this.currentBranch, targetCommit.id);
                this.checkout(this.currentBranch);
            } else {
                this.checkout(targetCommit.id);
            }
        },

        merge: function (ref, noFF) {
            var mergeTarget = this.getCommit(ref),
                currentCommit = this.getCommit('HEAD');

            if (!mergeTarget) {
                throw new Error('Cannot find ref: ' + ref);
            }

            if (currentCommit.id === mergeTarget.id) {
                throw new Error('Already up-to-date.');
            } else if (currentCommit.parent2 === mergeTarget.id) {
                throw new Error('Already up-to-date.');
            } else if (noFF === true) {
                var branchStartCommit = this.getCommit(mergeTarget.parent);
                while (branchStartCommit.parent !== currentCommit.id) {
                    branchStartCommit = this.getCommit(branchStartCommit.parent);
                }
                
                branchStartCommit.isNoFFBranch = true;
                
                this.commit({parent2: mergeTarget.id, isNoFFCommit: true});
            } else if (this.isAncestor(currentCommit, mergeTarget)) {
                this.fastForward(mergeTarget);
                return 'Fast-Forward';
            } else {
                this.commit({parent2: mergeTarget.id});
            }
        },

        rebase: function (ref) {
            var rebaseTarget = this.getCommit(ref),
                currentCommit = this.getCommit('HEAD'),
                isCommonAncestor,
                rebaseTreeLoc,
                rebaseMessage,
                toRebase = [], rebasedCommit,
                remainingHusk;

            if (!rebaseTarget) {
                throw new Error('Cannot find ref: ' + ref);
            }

            if (currentCommit.id === rebaseTarget.id) {
                throw new Error('Already up-to-date.');
            } else if (currentCommit.parent2 === rebaseTarget.id) {
                throw new Error('Already up-to-date.');
            }

            isCommonAncestor = this.isAncestor(currentCommit, rebaseTarget);

            if (isCommonAncestor) {
                this.fastForward(rebaseTarget);
                return 'Fast-Forward';
            }

            rebaseTreeLoc = rebaseTarget.id;

            while (!isCommonAncestor) {
                toRebase.unshift(currentCommit);
                currentCommit = this.getCommit(currentCommit.parent);
                isCommonAncestor = this.isAncestor(currentCommit, rebaseTarget);
            }

            for (var i = 0; i < toRebase.length; i++) {
                rebasedCommit = toRebase[i];
                rebaseMessage = rebasedCommit.message;

                remainingHusk = {
                    id: rebasedCommit.id,
                    parent: rebasedCommit.parent,
                    message: rebasedCommit.message,
                    tags: []
                };

                for (var t = 0; t < rebasedCommit.tags.length; t++) {
                    var tagName = rebasedCommit.tags[t];
                    if (tagName !== this.currentBranch && tagName !== 'HEAD') {
                        remainingHusk.tags.unshift(tagName);
                    }
                }

                this.commitData.push(remainingHusk);

                rebasedCommit.parent = rebaseTreeLoc;
                rebaseTreeLoc = HistoryView.generateId()
                rebasedCommit.id = rebaseTreeLoc;
                rebasedCommit.message = rebaseMessage;
                rebasedCommit.tags.length = 0;
                rebasedCommit.rebased = true;
            }

            if (this.currentBranch) {
                rebasedCommit.tags.push(this.currentBranch);
            }

            this.renderCommits();

            if (this.currentBranch) {
                this.checkout(this.currentBranch);
            } else {
                this.checkout(rebasedCommit.id);
            }
        }
    };

    return HistoryView;
});