1 files changed, 138 insertions, 0 deletions
diff --git a/pkg/gui/filetree/file_change_manager.go b/pkg/gui/filetree/file_change_manager.go
new file mode 100644
index 000000000..925398827
--- /dev/null
+++ b/pkg/gui/filetree/file_change_manager.go
@@ -0,0 +1,138 @@
+package filetree
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/jesseduffield/lazygit/pkg/commands/models"
+	"github.com/jesseduffield/lazygit/pkg/gui/presentation"
+	"github.com/sirupsen/logrus"
+)
+
+const EXPANDED_ARROW = "▼"
+const COLLAPSED_ARROW = "►"
+
+type FileChangeManager struct {
+	Files          []*models.File
+	Tree           *models.FileChangeNode
+	ShowTree       bool
+	Log            *logrus.Entry
+	CollapsedPaths map[string]bool
+}
+
+func NewFileChangeManager(files []*models.File, log *logrus.Entry, showTree bool) *FileChangeManager {
+	return &FileChangeManager{
+		Files:          files,
+		Log:            log,
+		ShowTree:       showTree,
+		CollapsedPaths: map[string]bool{},
+	}
+}
+
+func (m *FileChangeManager) GetItemAtIndex(index int) *models.FileChangeNode {
+	// need to traverse the three depth first until we get to the index.
+	return m.Tree.GetNodeAtIndex(index+1, m.CollapsedPaths) // ignoring root
+}
+
+func (m *FileChangeManager) GetIndexForPath(path string) (int, bool) {
+	index, found := m.Tree.GetIndexForPath(path, m.CollapsedPaths)
+	return index - 1, found
+}
+
+func (m *FileChangeManager) GetAllItems() []*models.FileChangeNode {
+	if m.Tree == nil {
+		return nil
+	}
+
+	return m.Tree.Flatten(m.CollapsedPaths)[1:] // ignoring root
+}
+
+func (m *FileChangeManager) GetItemsLength() int {
+	return m.Tree.Size(m.CollapsedPaths) - 1 // ignoring root
+}
+
+func (m *FileChangeManager) GetAllFiles() []*models.File {
+	return m.Files
+}
+
+func (m *FileChangeManager) SetFiles(files []*models.File) {
+	m.Files = files
+
+	m.SetTree()
+}
+
+func (m *FileChangeManager) SetTree() {
+	if m.ShowTree {
+		m.Tree = BuildTreeFromFiles(m.Files)
+	} else {
+		m.Tree = BuildFlatTreeFromFiles(m.Files)
+	}
+}
+
+func (m *FileChangeManager) Render(diffName string, submoduleConfigs []*models.SubmoduleConfig) []string {
+	return m.renderAux(m.Tree, "", -1, diffName, submoduleConfigs)
+}
+
+const INNER_ITEM = "├─ "
+const LAST_ITEM = "└─ "
+const NESTED = "│  "
+const NOTHING = "   "
+
+func (m *FileChangeManager) IsCollapsed(s *models.FileChangeNode) bool {
+	return m.CollapsedPaths[s.GetPath()]
+}
+
+func (m *FileChangeManager) ToggleCollapsed(s *models.FileChangeNode) {
+	m.CollapsedPaths[s.GetPath()] = !m.CollapsedPaths[s.GetPath()]
+}
+
+func (m *FileChangeManager) renderAux(s *models.FileChangeNode, prefix string, depth int, diffName string, submoduleConfigs []*models.SubmoduleConfig) []string {
+	isRoot := depth == -1
+	if s == nil {
+		return []string{}
+	}
+
+	getLine := func() string {
+		return prefix + presentation.GetFileLine(s.GetHasUnstagedChanges(), s.GetHasStagedChanges(), s.NameAtDepth(depth), diffName, submoduleConfigs, s.File)
+	}
+
+	if s.IsLeaf() {
+		if isRoot {
+			return []string{}
+		}
+		return []string{getLine()}
+	}
+
+	if m.IsCollapsed(s) {
+		return []string{fmt.Sprintf("%s %s", getLine(), COLLAPSED_ARROW)}
+	}
+
+	arr := []string{}
+	if !isRoot {
+		arr = append(arr, fmt.Sprintf("%s %s", getLine(), EXPANDED_ARROW))
+	}
+
+	newPrefix := prefix
+	if strings.HasSuffix(prefix, LAST_ITEM) {
+		newPrefix = strings.TrimSuffix(prefix, LAST_ITEM) + NOTHING
+	} else if strings.HasSuffix(prefix, INNER_ITEM) {
+		newPrefix = strings.TrimSuffix(prefix, INNER_ITEM) + NESTED
+	}
+
+	for i, child := range s.Children {
+		isLast := i == len(s.Children)-1
+
+		var childPrefix string
+		if isRoot {
+			childPrefix = newPrefix
+		} else if isLast {
+			childPrefix = newPrefix + LAST_ITEM
+		} else {
+			childPrefix = newPrefix + INNER_ITEM
+		}
+
+		arr = append(arr, m.renderAux(child, childPrefix, depth+1+s.CompressionLevel, diffName, submoduleConfigs)...)
+	}
+
+	return arr
+}