Initial patterm project

internal/app/tree.go

@@ -0,0 +1,59 @@
+package app
+
+func visibleSessionTree(children []*Child, focusID string) []*Child {
+	rootID := activeRootID(children, focusID)
+	if rootID == "" {
+		return nil
+	}
+	out := make([]*Child, 0, len(children))
+	for _, c := range children {
+		if c.Status() != StatusRunning {
+			continue
+		}
+		if c.ID == rootID || c.ParentID == rootID {
+			out = append(out, c)
+		}
+	}
+	return out
+}
+
+func activeRootID(children []*Child, focusID string) string {
+	if focusID != "" {
+		for _, c := range children {
+			if c.ID != focusID {
+				continue
+			}
+			if c.ParentID == "" {
+				return c.ID
+			}
+			if parent := findChildInSnapshot(children, c.ParentID); parent != nil {
+				return parent.ID
+			}
+			return ""
+		}
+	}
+	for _, c := range children {
+		if c.ParentID == "" && c.Status() == StatusRunning {
+			return c.ID
+		}
+	}
+	return ""
+}
+
+func findChildInSnapshot(children []*Child, id string) *Child {
+	for _, c := range children {
+		if c.ID == id {
+			return c
+		}
+	}
+	return nil
+}
+
+func firstRunningTopLevel(children []*Child) *Child {
+	for _, c := range children {
+		if c.ParentID == "" && c.Status() == StatusRunning {
+			return c
+		}
+	}
+	return nil
+}