From a7e45d47cda0b2b4f6325e8700434e7b2a2660ed Mon Sep 17 00:00:00 2001
From: Jacob Richman <jacob314@gmail.com>
Date: Mon, 16 Jun 2025 22:21:22 +0000
Subject: [PATCH] =?UTF-8?q?Fix=20bug=20where=20single=20line=20inserts=20w?=
 =?UTF-8?q?ere=20deleting=20all=20text=20after=20the=20in=E2=80=A6=20(#111?=
 =?UTF-8?q?4)?=
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---
 .../src/ui/components/shared/text-buffer.test.ts  | 15 +++++++++++++++
 .../cli/src/ui/components/shared/text-buffer.ts   |  4 +++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/packages/cli/src/ui/components/shared/text-buffer.test.ts b/packages/cli/src/ui/components/shared/text-buffer.test.ts
index c5295fc1..218ed1c3 100644
--- a/packages/cli/src/ui/components/shared/text-buffer.test.ts
+++ b/packages/cli/src/ui/components/shared/text-buffer.test.ts
@@ -173,6 +173,21 @@ describe('useTextBuffer', () => {
       expect(state.visualCursor).toEqual([0, 2]);
     });
 
+    it('insert: should insert text in the middle of a line', () => {
+      const { result } = renderHook(() =>
+        useTextBuffer({
+          initialText: 'abc',
+          viewport,
+          isValidPath: () => false,
+        }),
+      );
+      act(() => result.current.move('right'));
+      act(() => result.current.insert('-NEW-'));
+      const state = getBufferState(result);
+      expect(state.text).toBe('a-NEW-bc');
+      expect(state.cursor).toEqual([0, 6]);
+    });
+
     it('newline: should create a new line and move cursor', () => {
       const { result } = renderHook(() =>
         useTextBuffer({
diff --git a/packages/cli/src/ui/components/shared/text-buffer.ts b/packages/cli/src/ui/components/shared/text-buffer.ts
index ef21d00a..6b025dd5 100644
--- a/packages/cli/src/ui/components/shared/text-buffer.ts
+++ b/packages/cli/src/ui/components/shared/text-buffer.ts
@@ -635,9 +635,9 @@ export function useTextBuffer({
           const lineContent = currentLine(newCursorRow);
           const before = cpSlice(lineContent, 0, newCursorCol);
           const after = cpSlice(lineContent, newCursorCol);
-          newLines[newCursorRow] = before + parts[0];
 
           if (parts.length > 1) {
+            newLines[newCursorRow] = before + parts[0];
             const remainingParts = parts.slice(1);
             const lastPartOriginal = remainingParts.pop() ?? '';
             newLines.splice(newCursorRow + 1, 0, ...remainingParts);
@@ -649,6 +649,8 @@ export function useTextBuffer({
             newCursorRow = newCursorRow + parts.length - 1;
             newCursorCol = cpLen(lastPartOriginal);
           } else {
+            newLines[newCursorRow] = before + parts[0] + after;
+
             newCursorCol = cpLen(before) + cpLen(parts[0]);
           }
         } else if (op.type === 'backspace') {