Merge InputPrompt and multiline-editor and move autocomplete logic directly into InputPrompt (#453)

6 files changed, 598 insertions, 459 deletions

diff --git a/packages/cli/src/ui/App.tsx b/packages/cli/src/ui/App.tsx
index d168e0e6..7f16f4e5 100644
--- a/packages/cli/src/ui/App.tsx
+++ b/packages/cli/src/ui/App.tsx
@@ -17,7 +17,7 @@ import { Header } from './components/Header.js';
 import { LoadingIndicator } from './components/LoadingIndicator.js';
 import { AutoAcceptIndicator } from './components/AutoAcceptIndicator.js';
 import { ShellModeIndicator } from './components/ShellModeIndicator.js';
-import { EditorState, InputPrompt } from './components/InputPrompt.js';
+import { InputPrompt } from './components/InputPrompt.js';
 import { Footer } from './components/Footer.js';
 import { ThemeDialog } from './components/ThemeDialog.js';
 import { type Config } from '@gemini-code/server';
@@ -28,9 +28,6 @@ import { LoadedSettings } from '../config/settings.js';
 import { Tips } from './components/Tips.js';
 import { ConsoleOutput } from './components/ConsolePatcher.js';
 import { HistoryItemDisplay } from './components/HistoryItemDisplay.js';
-import { useCompletion } from './hooks/useCompletion.js';
-import { SuggestionsDisplay } from './components/SuggestionsDisplay.js';
-import { isAtCommand, isSlashCommand } from './utils/commandUtils.js';
 import { useHistory } from './hooks/useHistoryManager.js';
 import process from 'node:process'; // For performMemoryRefresh
 import { MessageType } from './types.js'; // For performMemoryRefresh
@@ -99,7 +96,6 @@ export const App = ({
       config.setGeminiMdFileCount(fileCount);
       setGeminiMdFileCount(fileCount);
 
-      // chatSessionRef.current = null; // This was in useGeminiStream, might need similar logic or pass chat ref
       addItem(
         {
           type: MessageType.INFO,
@@ -126,7 +122,7 @@ export const App = ({
   }, [config, addItem]);
 
   const { handleSlashCommand, slashCommands } = useSlashCommandProcessor(
-    config, // Pass config
+    config,
     addItem,
     clearItems,
     refreshStatic,
@@ -176,53 +172,24 @@ export const App = ({
 
   const isInputActive = streamingState === StreamingState.Idle && !initError;
 
-  const [query, setQuery] = useState('');
-  const [editorState, setEditorState] = useState<EditorState>({
-    key: 0,
-    initialCursorOffset: undefined,
-  });
-
-  const onChangeAndMoveCursor = useCallback(
-    (value: string) => {
-      setQuery(value);
-      setEditorState((s) => ({
-        key: s.key + 1,
-        initialCursorOffset: value.length,
-      }));
-    },
-    [setQuery, setEditorState],
-  );
-
   const handleClearScreen = useCallback(() => {
     clearItems();
     console.clear();
     refreshStatic();
   }, [clearItems, refreshStatic]);
 
-  const completion = useCompletion(
-    query,
-    config.getTargetDir(),
-    !shellModeActive &&
-      isInputActive &&
-      (isAtCommand(query) || isSlashCommand(query)),
-    slashCommands,
-  );
-
   // --- Render Logic ---
 
-  const { rows: terminalHeight, columns: terminalWidth } = useTerminalSize();
+  const { rows: terminalHeight } = useTerminalSize();
   const mainControlsRef = useRef<DOMElement>(null);
   const pendingHistoryItemRef = useRef<DOMElement>(null);
 
-  // Calculate width for suggestions, leave some padding
-  const suggestionsWidth = Math.max(60, Math.floor(terminalWidth * 0.8));
-
   useEffect(() => {
     if (mainControlsRef.current) {
       const fullFooterMeasurement = measureElement(mainControlsRef.current);
       setFooterHeight(fullFooterMeasurement.height);
     }
-  }, [terminalHeight]); // Re-calculate if terminalHeight changes, as it might affect footer's rendered height.
+  }, [terminalHeight]);
 
   const availableTerminalHeight = useMemo(() => {
     const staticExtraHeight = /* margins and padding */ 3;
@@ -326,7 +293,6 @@ export const App = ({
               onSelect={handleThemeSelect}
               onHighlight={handleThemeHighlight}
               settings={settings}
-              setQuery={setQuery}
             />
           </Box>
         ) : (
@@ -361,37 +327,16 @@ export const App = ({
               </Box>
             </Box>
             {isInputActive && (
-              <>
-                <InputPrompt
-                  query={query}
-                  onChange={setQuery}
-                  onChangeAndMoveCursor={onChangeAndMoveCursor}
-                  editorState={editorState}
-                  onSubmit={handleFinalSubmit} // Pass handleFinalSubmit directly
-                  showSuggestions={completion.showSuggestions}
-                  suggestions={completion.suggestions}
-                  activeSuggestionIndex={completion.activeSuggestionIndex}
-                  userMessages={userMessages} // Pass userMessages
-                  navigateSuggestionUp={completion.navigateUp}
-                  navigateSuggestionDown={completion.navigateDown}
-                  resetCompletion={completion.resetCompletionState}
-                  onClearScreen={handleClearScreen} // Added onClearScreen prop
-                  shellModeActive={shellModeActive}
-                  setShellModeActive={setShellModeActive}
-                />
-                {completion.showSuggestions && !shellModeActive && (
-                  <Box>
-                    <SuggestionsDisplay
-                      suggestions={completion.suggestions}
-                      activeIndex={completion.activeSuggestionIndex}
-                      isLoading={completion.isLoadingSuggestions}
-                      width={suggestionsWidth}
-                      scrollOffset={completion.visibleStartIndex}
-                      userInput={query}
-                    />
-                  </Box>
-                )}
-              </>
+              <InputPrompt
+                widthFraction={0.9}
+                onSubmit={handleFinalSubmit}
+                userMessages={userMessages}
+                onClearScreen={handleClearScreen}
+                config={config}
+                slashCommands={slashCommands}
+                shellModeActive={shellModeActive}
+                setShellModeActive={setShellModeActive}
+              />
             )}
           </>
         )}
diff --git a/packages/cli/src/ui/components/InputPrompt.tsx b/packages/cli/src/ui/components/InputPrompt.tsx
index 38af2a8c..26c9d14f 100644
--- a/packages/cli/src/ui/components/InputPrompt.tsx
+++ b/packages/cli/src/ui/components/InputPrompt.tsx
@@ -5,147 +5,174 @@
  */
 
 import React, { useCallback } from 'react';
-import { Text, Box, Key } from 'ink';
+import { Text, Box, useInput, useStdin } from 'ink';
 import { Colors } from '../colors.js';
-import { Suggestion } from './SuggestionsDisplay.js';
-import { MultilineTextEditor } from './shared/multiline-editor.js';
+import { SuggestionsDisplay } from './SuggestionsDisplay.js';
 import { useInputHistory } from '../hooks/useInputHistory.js';
+import { useTextBuffer, cpSlice, cpLen } from './shared/text-buffer.js';
+import chalk from 'chalk';
+import { useTerminalSize } from '../hooks/useTerminalSize.js';
+import stringWidth from 'string-width';
+import process from 'node:process';
+import { useCompletion } from '../hooks/useCompletion.js';
+import { isAtCommand, isSlashCommand } from '../utils/commandUtils.js';
+import { SlashCommand } from '../hooks/slashCommandProcessor.js';
+import { Config } from '@gemini-code/server';
 
 interface InputPromptProps {
-  query: string;
-  onChange: (value: string) => void;
-  onChangeAndMoveCursor: (value: string) => void;
-  editorState: EditorState;
   onSubmit: (value: string) => void;
-  showSuggestions: boolean;
-  suggestions: Suggestion[];
-  activeSuggestionIndex: number;
-  resetCompletion: () => void;
   userMessages: readonly string[];
-  navigateSuggestionUp: () => void;
-  navigateSuggestionDown: () => void;
   onClearScreen: () => void;
+  config: Config; // Added config for useCompletion
+  slashCommands: SlashCommand[]; // Added slashCommands for useCompletion
+  placeholder?: string;
+  height?: number; // Visible height of the editor area
+  focus?: boolean;
+  widthFraction: number;
   shellModeActive: boolean;
   setShellModeActive: (value: boolean) => void;
 }
 
-export interface EditorState {
-  key: number;
-  initialCursorOffset?: number;
-}
-
 export const InputPrompt: React.FC<InputPromptProps> = ({
-  query,
-  onChange,
-  onChangeAndMoveCursor,
-  editorState,
   onSubmit,
-  showSuggestions,
-  suggestions,
-  activeSuggestionIndex,
   userMessages,
-  navigateSuggestionUp,
-  navigateSuggestionDown,
-  resetCompletion,
   onClearScreen,
+  config,
+  slashCommands,
+  placeholder = 'Enter your message or use tools (e.g., @src/file.txt)...',
+  height = 10,
+  focus = true,
+  widthFraction,
   shellModeActive,
   setShellModeActive,
 }) => {
-  const handleSubmit = useCallback(
+  const terminalSize = useTerminalSize();
+  const padding = 3;
+  const effectiveWidth = Math.max(
+    20,
+    Math.round(terminalSize.columns * widthFraction) - padding,
+  );
+  const suggestionsWidth = Math.max(60, Math.floor(terminalSize.columns * 0.8));
+
+  const { stdin, setRawMode } = useStdin();
+
+  const buffer = useTextBuffer({
+    initialText: '',
+    viewport: { height, width: effectiveWidth },
+    stdin,
+    setRawMode,
+  });
+
+  const completion = useCompletion(
+    buffer.text,
+    config.getTargetDir(),
+    isAtCommand(buffer.text) || isSlashCommand(buffer.text),
+    slashCommands,
+  );
+
+  const resetCompletionState = completion.resetCompletionState;
+
+  const handleSubmitAndClear = useCallback(
     (submittedValue: string) => {
       onSubmit(submittedValue);
-      onChangeAndMoveCursor(''); // Clear query after submit
+      buffer.setText('');
+      resetCompletionState();
     },
-    [onSubmit, onChangeAndMoveCursor],
+    [onSubmit, buffer, resetCompletionState],
+  );
+
+  const onChangeAndMoveCursor = useCallback(
+    (newValue: string) => {
+      buffer.setText(newValue);
+      buffer.move('end');
+    },
+    [buffer],
   );
 
   const inputHistory = useInputHistory({
     userMessages,
-    onSubmit: handleSubmit,
-    isActive: !showSuggestions, // Input history is active when suggestions are not shown
-    currentQuery: query,
+    onSubmit: handleSubmitAndClear,
+    isActive: !completion.showSuggestions,
+    currentQuery: buffer.text,
     onChangeAndMoveCursor,
   });
 
+  const completionSuggestions = completion.suggestions;
   const handleAutocomplete = useCallback(
     (indexToUse: number) => {
-      if (indexToUse < 0 || indexToUse >= suggestions.length) {
+      if (indexToUse < 0 || indexToUse >= completionSuggestions.length) {
         return;
       }
-      const selectedSuggestion = suggestions[indexToUse];
-      const trimmedQuery = query.trimStart();
+      const query = buffer.text;
+      const selectedSuggestion = completionSuggestions[indexToUse];
 
-      if (trimmedQuery.startsWith('/')) {
-        // Handle / command completion
+      if (query.trimStart().startsWith('/')) {
         const slashIndex = query.indexOf('/');
         const base = query.substring(0, slashIndex + 1);
         const newValue = base + selectedSuggestion.value;
-        onChangeAndMoveCursor(newValue);
-        onSubmit(newValue); // Execute the command
-        onChangeAndMoveCursor(''); // Clear query after submit
+        buffer.setText(newValue);
+        handleSubmitAndClear(newValue);
       } else {
-        // Handle @ command completion
         const atIndex = query.lastIndexOf('@');
         if (atIndex === -1) return;
-
-        // Find the part of the query after the '@'
         const pathPart = query.substring(atIndex + 1);
-        // Find the last slash within that part
         const lastSlashIndexInPath = pathPart.lastIndexOf('/');
-
-        let base = '';
-        if (lastSlashIndexInPath === -1) {
-          // No slash after '@', replace everything after '@'
-          base = query.substring(0, atIndex + 1);
-        } else {
-          // Slash found, keep everything up to and including the last slash
-          base = query.substring(0, atIndex + 1 + lastSlashIndexInPath + 1);
+        let autoCompleteStartIndex = atIndex + 1;
+        if (lastSlashIndexInPath !== -1) {
+          autoCompleteStartIndex += lastSlashIndexInPath + 1;
         }
-
-        const newValue = base + selectedSuggestion.value;
-        onChangeAndMoveCursor(newValue);
+        buffer.replaceRangeByOffset(
+          autoCompleteStartIndex,
+          buffer.text.length,
+          selectedSuggestion.value,
+        );
       }
-
-      resetCompletion(); // Hide suggestions after selection
+      resetCompletionState();
     },
-    [query, suggestions, resetCompletion, onChangeAndMoveCursor, onSubmit],
+    [resetCompletionState, handleSubmitAndClear, buffer, completionSuggestions],
   );
 
-  const inputPreprocessor = useCallback(
-    (input: string, key: Key) => {
-      if (input === '!' && query === '' && !showSuggestions) {
+  useInput(
+    (input, key) => {
+      if (!focus) {
+        return;
+      }
+      const query = buffer.text;
+
+      if (input === '!' && query === '' && !completion.showSuggestions) {
         setShellModeActive(!shellModeActive);
-        onChangeAndMoveCursor(''); // Clear the '!' from input
+        buffer.setText(''); // Clear the '!' from input
         return true;
       }
-      if (showSuggestions) {
+
+      if (completion.showSuggestions) {
         if (key.upArrow) {
-          navigateSuggestionUp();
-          return true;
-        } else if (key.downArrow) {
-          navigateSuggestionDown();
-          return true;
-        } else if (key.tab) {
-          if (suggestions.length > 0) {
+          completion.navigateUp();
+          return;
+        }
+        if (key.downArrow) {
+          completion.navigateDown();
+          return;
+        }
+        if (key.tab) {
+          if (completion.suggestions.length > 0) {
             const targetIndex =
-              activeSuggestionIndex === -1 ? 0 : activeSuggestionIndex;
-            if (targetIndex < suggestions.length) {
+              completion.activeSuggestionIndex === -1
+                ? 0
+                : completion.activeSuggestionIndex;
+            if (targetIndex < completion.suggestions.length) {
               handleAutocomplete(targetIndex);
-              return true;
             }
           }
-        } else if (key.return) {
-          if (activeSuggestionIndex >= 0) {
-            handleAutocomplete(activeSuggestionIndex);
-          } else {
-            if (query.trim()) {
-              handleSubmit(query);
-            }
+          return;
+        }
+        if (key.return) {
+          if (completion.activeSuggestionIndex >= 0) {
+            handleAutocomplete(completion.activeSuggestionIndex);
+          } else if (query.trim()) {
+            handleSubmitAndClear(query);
           }
-          return true;
-        } else if (key.escape) {
-          resetCompletion();
-          return true;
+          return;
         }
       } else {
         // Keybindings when suggestions are not shown
@@ -161,60 +188,197 @@ export const InputPrompt: React.FC<InputPromptProps> = ({
           inputHistory.navigateDown();
           return true;
         }
+        if (key.escape) {
+          completion.resetCompletionState();
+          return;
+        }
+      }
+
+      // Ctrl+A (Home)
+      if (key.ctrl && input === 'a') {
+        buffer.move('home');
+        buffer.moveToOffset(0);
+        return;
+      }
+      // Ctrl+E (End)
+      if (key.ctrl && input === 'e') {
+        buffer.move('end');
+        buffer.moveToOffset(cpLen(buffer.text));
+        return;
+      }
+      // Ctrl+L (Clear Screen)
+      if (key.ctrl && input === 'l') {
+        onClearScreen();
+        return;
+      }
+      // Ctrl+P (History Up)
+      if (key.ctrl && input === 'p' && !completion.showSuggestions) {
+        inputHistory.navigateUp();
+        return;
+      }
+      // Ctrl+N (History Down)
+      if (key.ctrl && input === 'n' && !completion.showSuggestions) {
+        inputHistory.navigateDown();
+        return;
+      }
+
+      // Core text editing from MultilineTextEditor's useInput
+      if (key.ctrl && input === 'k') {
+        buffer.killLineRight();
+        return;
+      }
+      if (key.ctrl && input === 'u') {
+        buffer.killLineLeft();
+        return;
+      }
+      const isCtrlX =
+        (key.ctrl && (input === 'x' || input === '\x18')) || input === '\x18';
+      const isCtrlEFromEditor =
+        (key.ctrl && (input === 'e' || input === '\x05')) ||
+        input === '\x05' ||
+        (!key.ctrl &&
+          input === 'e' &&
+          input.length === 1 &&
+          input.charCodeAt(0) === 5);
+
+      if (isCtrlX || isCtrlEFromEditor) {
+        if (isCtrlEFromEditor && !(key.ctrl && input === 'e')) {
+          // Avoid double handling Ctrl+E
+          buffer.openInExternalEditor();
+          return;
+        }
+        if (isCtrlX) {
+          buffer.openInExternalEditor();
+          return;
+        }
+      }
+
+      if (
+        process.env['TEXTBUFFER_DEBUG'] === '1' ||
+        process.env['TEXTBUFFER_DEBUG'] === 'true'
+      ) {
+        console.log('[InputPromptCombined] event', { input, key });
+      }
+
+      // Ctrl+Enter for newline, Enter for submit
+      if (key.return) {
+        if (key.ctrl) {
+          // Ctrl+Enter for newline
+          buffer.newline();
+        } else {
+          // Enter for submit
+          if (query.trim()) {
+            handleSubmitAndClear(query);
+          }
+        }
+        return;
+      }
+
+      // Standard arrow navigation within the buffer
+      if (key.upArrow && !completion.showSuggestions) {
+        if (
+          buffer.visualCursor[0] === 0 &&
+          buffer.visualScrollRow === 0 &&
+          inputHistory.navigateUp
+        ) {
+          inputHistory.navigateUp();
+        } else {
+          buffer.move('up');
+        }
+        return;
       }
-      return false;
+      if (key.downArrow && !completion.showSuggestions) {
+        if (
+          buffer.visualCursor[0] === buffer.allVisualLines.length - 1 &&
+          inputHistory.navigateDown
+        ) {
+          inputHistory.navigateDown();
+        } else {
+          buffer.move('down');
+        }
+        return;
+      }
+
+      // Fallback to buffer's default input handling
+      buffer.handleInput(input, key as Record<string, boolean>);
+    },
+    {
+      isActive: focus,
     },
-    [
-      handleAutocomplete,
-      navigateSuggestionDown,
-      navigateSuggestionUp,
-      query,
-      suggestions,
-      showSuggestions,
-      resetCompletion,
-      activeSuggestionIndex,
-      handleSubmit,
-      inputHistory,
-      onClearScreen,
-      shellModeActive,
-      setShellModeActive,
-      onChangeAndMoveCursor,
-    ],
   );
 
+  const linesToRender = buffer.viewportVisualLines;
+  const [cursorVisualRowAbsolute, cursorVisualColAbsolute] =
+    buffer.visualCursor;
+  const scrollVisualRow = buffer.visualScrollRow;
+
   return (
-    <Box
-      borderStyle="round"
-      borderColor={shellModeActive ? Colors.AccentYellow : Colors.AccentBlue}
-      paddingX={1}
-    >
-      <Text color={shellModeActive ? Colors.AccentYellow : Colors.AccentPurple}>
-        {shellModeActive ? '! ' : '> '}
-      </Text>
-      <Box flexGrow={1}>
-        <MultilineTextEditor
-          key={editorState.key.toString()}
-          initialCursorOffset={editorState.initialCursorOffset}
-          initialText={query}
-          onChange={onChange}
-          placeholder="Type your message or @path/to/file"
-          /* Account for width used by the box and &gt; */
-          navigateUp={inputHistory.navigateUp}
-          navigateDown={inputHistory.navigateDown}
-          inputPreprocessor={inputPreprocessor}
-          widthUsedByParent={3}
-          widthFraction={0.9}
-          onSubmit={() => {
-            // This onSubmit is for the TextInput component itself.
-            // It should only fire if suggestions are NOT showing,
-            // as inputPreprocessor handles Enter when suggestions are visible.
-            const trimmedQuery = query.trim();
-            if (!showSuggestions && trimmedQuery) {
-              handleSubmit(trimmedQuery);
-            }
-          }}
-        />
+    <>
+      <Box
+        borderStyle="round"
+        borderColor={shellModeActive ? Colors.AccentYellow : Colors.AccentBlue}
+        paddingX={1}
+      >
+        <Text
+          color={shellModeActive ? Colors.AccentYellow : Colors.AccentPurple}
+        >
+          {shellModeActive ? '! ' : '> '}
+        </Text>
+        <Box flexGrow={1} flexDirection="column">
+          {buffer.text.length === 0 && placeholder ? (
+            <Text color={Colors.SubtleComment}>{placeholder}</Text>
+          ) : (
+            linesToRender.map((lineText, visualIdxInRenderedSet) => {
+              const cursorVisualRow = cursorVisualRowAbsolute - scrollVisualRow;
+              let display = cpSlice(lineText, 0, effectiveWidth);
+              const currentVisualWidth = stringWidth(display);
+              if (currentVisualWidth < effectiveWidth) {
+                display =
+                  display + ' '.repeat(effectiveWidth - currentVisualWidth);
+              }
+
+              if (visualIdxInRenderedSet === cursorVisualRow) {
+                const relativeVisualColForHighlight = cursorVisualColAbsolute;
+                if (relativeVisualColForHighlight >= 0) {
+                  if (relativeVisualColForHighlight < cpLen(display)) {
+                    const charToHighlight =
+                      cpSlice(
+                        display,
+                        relativeVisualColForHighlight,
+                        relativeVisualColForHighlight + 1,
+                      ) || ' ';
+                    const highlighted = chalk.inverse(charToHighlight);
+                    display =
+                      cpSlice(display, 0, relativeVisualColForHighlight) +
+                      highlighted +
+                      cpSlice(display, relativeVisualColForHighlight + 1);
+                  } else if (
+                    relativeVisualColForHighlight === cpLen(display) &&
+                    cpLen(display) === effectiveWidth
+                  ) {
+                    display = display + chalk.inverse(' ');
+                  }
+                }
+              }
+              return (
+                <Text key={`line-${visualIdxInRenderedSet}`}>{display}</Text>
+              );
+            })
+          )}
+        </Box>
       </Box>
-    </Box>
+      {completion.showSuggestions && (
+        <Box>
+          <SuggestionsDisplay
+            suggestions={completion.suggestions}
+            activeIndex={completion.activeSuggestionIndex}
+            isLoading={completion.isLoadingSuggestions}
+            width={suggestionsWidth}
+            scrollOffset={completion.visibleStartIndex}
+            userInput={buffer.text}
+          />
+        </Box>
+      )}
+    </>
   );
 };
diff --git a/packages/cli/src/ui/components/ThemeDialog.tsx b/packages/cli/src/ui/components/ThemeDialog.tsx
index 7ab4e3b1..58bfeffa 100644
--- a/packages/cli/src/ui/components/ThemeDialog.tsx
+++ b/packages/cli/src/ui/components/ThemeDialog.tsx
@@ -21,15 +21,12 @@ interface ThemeDialogProps {
   onHighlight: (themeName: string | undefined) => void;
   /** The settings object */
   settings: LoadedSettings;
-  /** Callback to set the query */
-  setQuery: (query: string) => void;
 }
 
 export function ThemeDialog({
   onSelect,
   onHighlight,
   settings,
-  setQuery,
 }: ThemeDialogProps): React.JSX.Element {
   const [selectedScope, setSelectedScope] = useState<SettingScope>(
     SettingScope.User,
@@ -59,7 +56,6 @@ export function ThemeDialog({
   ];
 
   const handleThemeSelect = (themeName: string) => {
-    setQuery(''); // Clear the query when user selects a theme
     onSelect(themeName, selectedScope);
   };
 
@@ -82,7 +78,6 @@ export function ThemeDialog({
       setFocusedSection((prev) => (prev === 'theme' ? 'scope' : 'theme'));
     }
     if (key.escape) {
-      setQuery(''); // Clear the query when user hits escape
       onSelect(undefined, selectedScope);
     }
   });
diff --git a/packages/cli/src/ui/components/shared/multiline-editor.tsx b/packages/cli/src/ui/components/shared/multiline-editor.tsx
deleted file mode 100644
index 890a9b47..00000000
--- a/packages/cli/src/ui/components/shared/multiline-editor.tsx
+++ /dev/null
@@ -1,249 +0,0 @@
-/**
- * @license
- * Copyright 2025 Google LLC
- * SPDX-License-Identifier: Apache-2.0
- */
-
-import { useTextBuffer, cpSlice, cpLen } from './text-buffer.js';
-import chalk from 'chalk';
-import { Box, Text, useInput, useStdin, Key } from 'ink';
-import React from 'react';
-import { useTerminalSize } from '../../hooks/useTerminalSize.js';
-import { Colors } from '../../colors.js';
-import stringWidth from 'string-width';
-
-export interface MultilineTextEditorProps {
-  // Initial contents.
-  readonly initialText?: string;
-
-  // Placeholder text.
-  readonly placeholder?: string;
-
-  // Visible width.
-  readonly width?: number;
-
-  // Visible height.
-  readonly height?: number;
-
-  // Called when the user submits (plain <Enter> key).
-  readonly onSubmit?: (text: string) => void;
-
-  // Capture keyboard input.
-  readonly focus?: boolean;
-
-  // Called when the internal text buffer updates.
-  readonly onChange?: (text: string) => void;
-
-  // Called when the user attempts to navigate past the start of the editor
-  // with the up arrow.
-  readonly navigateUp?: () => void;
-
-  // Called when the user attempts to navigate past the end of the editor
-  // with the down arrow.
-  readonly navigateDown?: () => void;
-
-  // Called on all key events to allow the caller. Returns true if the
-  // event was handled and should not be passed to the editor.
-  readonly inputPreprocessor?: (input: string, key: Key) => boolean;
-
-  // Optional initial cursor position (character offset)
-  readonly initialCursorOffset?: number;
-
-  readonly widthUsedByParent: number;
-
-  readonly widthFraction?: number;
-}
-
-export const MultilineTextEditor = ({
-  initialText = '',
-  placeholder = '',
-  width,
-  height = 10,
-  onSubmit,
-  focus = true,
-  onChange,
-  initialCursorOffset,
-  widthUsedByParent,
-  widthFraction = 1,
-  navigateUp,
-  navigateDown,
-  inputPreprocessor,
-}: MultilineTextEditorProps): React.ReactElement => {
-  const terminalSize = useTerminalSize();
-  const effectiveWidth = Math.max(
-    20,
-    width ??
-      Math.round(terminalSize.columns * widthFraction) - widthUsedByParent,
-  );
-
-  const { stdin, setRawMode } = useStdin();
-
-  const buffer = useTextBuffer({
-    initialText,
-    initialCursorOffset,
-    viewport: { height, width: effectiveWidth },
-    stdin,
-    setRawMode,
-    onChange, // Pass onChange to the hook
-  });
-
-  useInput(
-    (input, key) => {
-      if (!focus) {
-        return;
-      }
-
-      if (inputPreprocessor?.(input, key) === true) {
-        return;
-      }
-
-      if (key.ctrl && input === 'k') {
-        buffer.killLineRight();
-        return;
-      }
-
-      if (key.ctrl && input === 'u') {
-        buffer.killLineLeft();
-        return;
-      }
-
-      const isCtrlX =
-        (key.ctrl && (input === 'x' || input === '\x18')) || input === '\x18';
-      if (isCtrlX) {
-        buffer.openInExternalEditor();
-        return;
-      }
-
-      if (
-        process.env['TEXTBUFFER_DEBUG'] === '1' ||
-        process.env['TEXTBUFFER_DEBUG'] === 'true'
-      ) {
-        console.log('[MultilineTextEditor] event', { input, key });
-      }
-
-      if (input.startsWith('[') && input.endsWith('u')) {
-        const m = input.match(/^\[([0-9]+);([0-9]+)u$/);
-        if (m && m[1] === '13') {
-          const mod = Number(m[2]);
-          const hasCtrl = Math.floor(mod / 4) % 2 === 1;
-          if (hasCtrl) {
-            if (onSubmit) {
-              onSubmit(buffer.text);
-            }
-          } else {
-            buffer.newline();
-          }
-          return;
-        }
-      }
-
-      if (input.startsWith('[27;') && input.endsWith('~')) {
-        const m = input.match(/^\[27;([0-9]+);13~$/);
-        if (m) {
-          const mod = Number(m[1]);
-          const hasCtrl = Math.floor(mod / 4) % 2 === 1;
-          if (hasCtrl) {
-            if (onSubmit) {
-              onSubmit(buffer.text);
-            }
-          } else {
-            buffer.newline();
-          }
-          return;
-        }
-      }
-
-      if (input === '\n') {
-        buffer.newline();
-        return;
-      }
-
-      if (input === '\r') {
-        if (onSubmit) {
-          onSubmit(buffer.text);
-        }
-        return;
-      }
-
-      if (key.upArrow) {
-        if (
-          buffer.visualCursor[0] === 0 &&
-          buffer.visualScrollRow === 0 &&
-          navigateUp
-        ) {
-          navigateUp();
-          return;
-        }
-      }
-
-      if (key.downArrow) {
-        if (
-          buffer.visualCursor[0] === buffer.allVisualLines.length - 1 &&
-          navigateDown
-        ) {
-          navigateDown();
-          return;
-        }
-      }
-
-      buffer.handleInput(input, key as Record<string, boolean>);
-    },
-    { isActive: focus },
-  );
-
-  const linesToRender = buffer.viewportVisualLines; // This is the subset of visual lines for display
-  const [cursorVisualRowAbsolute, cursorVisualColAbsolute] =
-    buffer.visualCursor; // This is relative to *all* visual lines
-  const scrollVisualRow = buffer.visualScrollRow;
-  // scrollHorizontalCol removed as it's always 0 due to word wrap
-
-  return (
-    <Box flexDirection="column">
-      {buffer.text.length === 0 && placeholder ? (
-        <Text color={Colors.SubtleComment}>{placeholder}</Text>
-      ) : (
-        linesToRender.map((lineText, visualIdxInRenderedSet) => {
-          // cursorVisualRow is the cursor's row index within the currently *rendered* set of visual lines
-          const cursorVisualRow = cursorVisualRowAbsolute - scrollVisualRow;
-
-          let display = cpSlice(
-            lineText,
-            0, // Start from 0 as horizontal scroll is disabled
-            effectiveWidth, // This is still code point based for slicing
-          );
-          // Pad based on visual width
-          const currentVisualWidth = stringWidth(display);
-          if (currentVisualWidth < effectiveWidth) {
-            display = display + ' '.repeat(effectiveWidth - currentVisualWidth);
-          }
-
-          if (visualIdxInRenderedSet === cursorVisualRow) {
-            const relativeVisualColForHighlight = cursorVisualColAbsolute; // Directly use absolute as horizontal scroll is 0
-
-            if (relativeVisualColForHighlight >= 0) {
-              if (relativeVisualColForHighlight < cpLen(display)) {
-                const charToHighlight =
-                  cpSlice(
-                    display,
-                    relativeVisualColForHighlight,
-                    relativeVisualColForHighlight + 1,
-                  ) || ' ';
-                const highlighted = chalk.inverse(charToHighlight);
-                display =
-                  cpSlice(display, 0, relativeVisualColForHighlight) +
-                  highlighted +
-                  cpSlice(display, relativeVisualColForHighlight + 1);
-              } else if (
-                relativeVisualColForHighlight === cpLen(display) &&
-                cpLen(display) === effectiveWidth
-              ) {
-                display = display + chalk.inverse(' ');
-              }
-            }
-          }
-          return <Text key={visualIdxInRenderedSet}>{display}</Text>;
-        })
-      )}
-    </Box>
-  );
-};
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 acaa4179..704666d1 100644
--- a/packages/cli/src/ui/components/shared/text-buffer.test.ts
+++ b/packages/cli/src/ui/components/shared/text-buffer.test.ts
@@ -6,7 +6,12 @@
 
 import { describe, it, expect, beforeEach } from 'vitest';
 import { renderHook, act } from '@testing-library/react';
-import { useTextBuffer, Viewport, TextBuffer } from './text-buffer.js';
+import {
+  useTextBuffer,
+  Viewport,
+  TextBuffer,
+  offsetToLogicalPos,
+} from './text-buffer.js';
 
 // Helper to get the state from the hook
 const getBufferState = (result: { current: TextBuffer }) => ({
@@ -512,4 +517,200 @@ describe('useTextBuffer', () => {
   // - Selection and clipboard (copy/paste) - might need clipboard API mocks or internal state check
   // - openInExternalEditor (heavy mocking of fs, child_process, os)
   // - All edge cases for visual scrolling and wrapping with different viewport sizes and text content.
+
+  describe('replaceRange', () => {
+    it('should replace a single-line range with single-line text', () => {
+      const { result } = renderHook(() =>
+        useTextBuffer({ initialText: '@pac', viewport }),
+      );
+      act(() => result.current.replaceRange(0, 1, 0, 4, 'packages'));
+      const state = getBufferState(result);
+      expect(state.text).toBe('@packages');
+      expect(state.cursor).toEqual([0, 9]); // cursor after 'typescript'
+    });
+
+    it('should replace a multi-line range with single-line text', () => {
+      const { result } = renderHook(() =>
+        useTextBuffer({ initialText: 'hello\nworld\nagain', viewport }),
+      );
+      act(() => result.current.replaceRange(0, 2, 1, 3, ' new ')); // replace 'llo\nwor' with ' new '
+      const state = getBufferState(result);
+      expect(state.text).toBe('he new ld\nagain');
+      expect(state.cursor).toEqual([0, 7]); // cursor after ' new '
+    });
+
+    it('should delete a range when replacing with an empty string', () => {
+      const { result } = renderHook(() =>
+        useTextBuffer({ initialText: 'hello world', viewport }),
+      );
+      act(() => result.current.replaceRange(0, 5, 0, 11, '')); // delete ' world'
+      const state = getBufferState(result);
+      expect(state.text).toBe('hello');
+      expect(state.cursor).toEqual([0, 5]);
+    });
+
+    it('should handle replacing at the beginning of the text', () => {
+      const { result } = renderHook(() =>
+        useTextBuffer({ initialText: 'world', viewport }),
+      );
+      act(() => result.current.replaceRange(0, 0, 0, 0, 'hello '));
+      const state = getBufferState(result);
+      expect(state.text).toBe('hello world');
+      expect(state.cursor).toEqual([0, 6]);
+    });
+
+    it('should handle replacing at the end of the text', () => {
+      const { result } = renderHook(() =>
+        useTextBuffer({ initialText: 'hello', viewport }),
+      );
+      act(() => result.current.replaceRange(0, 5, 0, 5, ' world'));
+      const state = getBufferState(result);
+      expect(state.text).toBe('hello world');
+      expect(state.cursor).toEqual([0, 11]);
+    });
+
+    it('should handle replacing the entire buffer content', () => {
+      const { result } = renderHook(() =>
+        useTextBuffer({ initialText: 'old text', viewport }),
+      );
+      act(() => result.current.replaceRange(0, 0, 0, 8, 'new text'));
+      const state = getBufferState(result);
+      expect(state.text).toBe('new text');
+      expect(state.cursor).toEqual([0, 8]);
+    });
+
+    it('should correctly replace with unicode characters', () => {
+      const { result } = renderHook(() =>
+        useTextBuffer({ initialText: 'hello *** world', viewport }),
+      );
+      act(() => result.current.replaceRange(0, 6, 0, 9, '你好'));
+      const state = getBufferState(result);
+      expect(state.text).toBe('hello 你好 world');
+      expect(state.cursor).toEqual([0, 8]); // after '你好'
+    });
+
+    it('should handle invalid range by returning false and not changing text', () => {
+      const { result } = renderHook(() =>
+        useTextBuffer({ initialText: 'test', viewport }),
+      );
+      let success = true;
+      act(() => {
+        success = result.current.replaceRange(0, 5, 0, 3, 'fail'); // startCol > endCol in same line
+      });
+      expect(success).toBe(false);
+      expect(getBufferState(result).text).toBe('test');
+
+      act(() => {
+        success = result.current.replaceRange(1, 0, 0, 0, 'fail'); // startRow > endRow
+      });
+      expect(success).toBe(false);
+      expect(getBufferState(result).text).toBe('test');
+    });
+
+    it('replaceRange: multiple lines with a single character', () => {
+      const { result } = renderHook(() =>
+        useTextBuffer({ initialText: 'first\nsecond\nthird', viewport }),
+      );
+      act(() => result.current.replaceRange(0, 2, 2, 3, 'X')); // Replace 'rst\nsecond\nthi'
+      const state = getBufferState(result);
+      expect(state.text).toBe('fiXrd');
+      expect(state.cursor).toEqual([0, 3]); // After 'X'
+    });
+  });
+});
+
+describe('offsetToLogicalPos', () => {
+  it('should return [0,0] for offset 0', () => {
+    expect(offsetToLogicalPos('any text', 0)).toEqual([0, 0]);
+  });
+
+  it('should handle single line text', () => {
+    const text = 'hello';
+    expect(offsetToLogicalPos(text, 0)).toEqual([0, 0]); // Start
+    expect(offsetToLogicalPos(text, 2)).toEqual([0, 2]); // Middle 'l'
+    expect(offsetToLogicalPos(text, 5)).toEqual([0, 5]); // End
+    expect(offsetToLogicalPos(text, 10)).toEqual([0, 5]); // Beyond end
+  });
+
+  it('should handle multi-line text', () => {
+    const text = 'hello\nworld\n123';
+    // "hello" (5) + \n (1) + "world" (5) + \n (1) + "123" (3)
+    // h e l l o \n w o r l d \n 1 2 3
+    // 0 1 2 3 4  5  6 7 8 9 0  1  2 3 4
+    // Line 0: "hello" (length 5)
+    expect(offsetToLogicalPos(text, 0)).toEqual([0, 0]); // Start of 'hello'
+    expect(offsetToLogicalPos(text, 3)).toEqual([0, 3]); // 'l' in 'hello'
+    expect(offsetToLogicalPos(text, 5)).toEqual([0, 5]); // End of 'hello' (before \n)
+
+    // Line 1: "world" (length 5)
+    expect(offsetToLogicalPos(text, 6)).toEqual([1, 0]); // Start of 'world' (after \n)
+    expect(offsetToLogicalPos(text, 8)).toEqual([1, 2]); // 'r' in 'world'
+    expect(offsetToLogicalPos(text, 11)).toEqual([1, 5]); // End of 'world' (before \n)
+
+    // Line 2: "123" (length 3)
+    expect(offsetToLogicalPos(text, 12)).toEqual([2, 0]); // Start of '123' (after \n)
+    expect(offsetToLogicalPos(text, 13)).toEqual([2, 1]); // '2' in '123'
+    expect(offsetToLogicalPos(text, 15)).toEqual([2, 3]); // End of '123'
+    expect(offsetToLogicalPos(text, 20)).toEqual([2, 3]); // Beyond end of text
+  });
+
+  it('should handle empty lines', () => {
+    const text = 'a\n\nc'; // "a" (1) + \n (1) + "" (0) + \n (1) + "c" (1)
+    expect(offsetToLogicalPos(text, 0)).toEqual([0, 0]); // 'a'
+    expect(offsetToLogicalPos(text, 1)).toEqual([0, 1]); // End of 'a'
+    expect(offsetToLogicalPos(text, 2)).toEqual([1, 0]); // Start of empty line
+    expect(offsetToLogicalPos(text, 3)).toEqual([2, 0]); // Start of 'c'
+    expect(offsetToLogicalPos(text, 4)).toEqual([2, 1]); // End of 'c'
+  });
+
+  it('should handle text ending with a newline', () => {
+    const text = 'hello\n'; // "hello" (5) + \n (1)
+    expect(offsetToLogicalPos(text, 5)).toEqual([0, 5]); // End of 'hello'
+    expect(offsetToLogicalPos(text, 6)).toEqual([1, 0]); // Position on the new empty line after
+
+    expect(offsetToLogicalPos(text, 7)).toEqual([1, 0]); // Still on the new empty line
+  });
+
+  it('should handle text starting with a newline', () => {
+    const text = '\nhello'; // "" (0) + \n (1) + "hello" (5)
+    expect(offsetToLogicalPos(text, 0)).toEqual([0, 0]); // Start of first empty line
+    expect(offsetToLogicalPos(text, 1)).toEqual([1, 0]); // Start of 'hello'
+    expect(offsetToLogicalPos(text, 3)).toEqual([1, 2]); // 'l' in 'hello'
+  });
+
+  it('should handle empty string input', () => {
+    expect(offsetToLogicalPos('', 0)).toEqual([0, 0]);
+    expect(offsetToLogicalPos('', 5)).toEqual([0, 0]);
+  });
+
+  it('should handle multi-byte unicode characters correctly', () => {
+    const text = '你好\n世界'; // "你好" (2 chars) + \n (1) + "世界" (2 chars)
+    // Total "code points" for offset calculation: 2 + 1 + 2 = 5
+    expect(offsetToLogicalPos(text, 0)).toEqual([0, 0]); // Start of '你好'
+    expect(offsetToLogicalPos(text, 1)).toEqual([0, 1]); // After '你', before '好'
+    expect(offsetToLogicalPos(text, 2)).toEqual([0, 2]); // End of '你好'
+    expect(offsetToLogicalPos(text, 3)).toEqual([1, 0]); // Start of '世界'
+    expect(offsetToLogicalPos(text, 4)).toEqual([1, 1]); // After '世', before '界'
+    expect(offsetToLogicalPos(text, 5)).toEqual([1, 2]); // End of '世界'
+    expect(offsetToLogicalPos(text, 6)).toEqual([1, 2]); // Beyond end
+  });
+
+  it('should handle offset exactly at newline character', () => {
+    const text = 'abc\ndef';
+    // a b c \n d e f
+    // 0 1 2  3  4 5 6
+    expect(offsetToLogicalPos(text, 3)).toEqual([0, 3]); // End of 'abc'
+    // The next character is the newline, so an offset of 4 means the start of the next line.
+    expect(offsetToLogicalPos(text, 4)).toEqual([1, 0]); // Start of 'def'
+  });
+
+  it('should handle offset in the middle of a multi-byte character (should place at start of that char)', () => {
+    // This scenario is tricky as "offset" is usually character-based.
+    // Assuming cpLen and related logic handles this by treating multi-byte as one unit.
+    // The current implementation of offsetToLogicalPos uses cpLen, so it should be code-point aware.
+    const text = '🐶🐱'; // 2 code points
+    expect(offsetToLogicalPos(text, 0)).toEqual([0, 0]);
+    expect(offsetToLogicalPos(text, 1)).toEqual([0, 1]); // After 🐶
+    expect(offsetToLogicalPos(text, 2)).toEqual([0, 2]); // After 🐱
+  });
 });
diff --git a/packages/cli/src/ui/components/shared/text-buffer.ts b/packages/cli/src/ui/components/shared/text-buffer.ts
index f84d83bc..a8b8cef3 100644
--- a/packages/cli/src/ui/components/shared/text-buffer.ts
+++ b/packages/cli/src/ui/components/shared/text-buffer.ts
@@ -119,6 +119,56 @@ function calculateInitialCursorPosition(
   }
   return [0, 0]; // Default for empty text
 }
+
+export function offsetToLogicalPos(
+  text: string,
+  offset: number,
+): [number, number] {
+  let row = 0;
+  let col = 0;
+  let currentOffset = 0;
+
+  if (offset === 0) return [0, 0];
+
+  const lines = text.split('\n');
+  for (let i = 0; i < lines.length; i++) {
+    const line = lines[i];
+    const lineLength = cpLen(line);
+    const lineLengthWithNewline = lineLength + (i < lines.length - 1 ? 1 : 0);
+
+    if (offset <= currentOffset + lineLength) {
+      // Check against lineLength first
+      row = i;
+      col = offset - currentOffset;
+      return [row, col];
+    } else if (offset <= currentOffset + lineLengthWithNewline) {
+      // Check if offset is the newline itself
+      row = i;
+      col = lineLength; // Position cursor at the end of the current line content
+      // If the offset IS the newline, and it's not the last line, advance to next line, col 0
+      if (
+        offset === currentOffset + lineLengthWithNewline &&
+        i < lines.length - 1
+      ) {
+        return [i + 1, 0];
+      }
+      return [row, col]; // Otherwise, it's at the end of the current line content
+    }
+    currentOffset += lineLengthWithNewline;
+  }
+
+  // If offset is beyond the text length, place cursor at the end of the last line
+  // or [0,0] if text is empty
+  if (lines.length > 0) {
+    row = lines.length - 1;
+    col = cpLen(lines[row]);
+  } else {
+    row = 0;
+    col = 0;
+  }
+  return [row, col];
+}
+
 // Helper to calculate visual lines and map cursor positions
 function calculateVisualLayout(
   logicalLines: string[],
@@ -1178,6 +1228,31 @@ export function useTextBuffer({
     [visualLines, visualScrollRow, viewport.height],
   );
 
+  const replaceRangeByOffset = useCallback(
+    (
+      startOffset: number,
+      endOffset: number,
+      replacementText: string,
+    ): boolean => {
+      dbg('replaceRangeByOffset', { startOffset, endOffset, replacementText });
+      const [startRow, startCol] = offsetToLogicalPos(text, startOffset);
+      const [endRow, endCol] = offsetToLogicalPos(text, endOffset);
+      return replaceRange(startRow, startCol, endRow, endCol, replacementText);
+    },
+    [text, replaceRange],
+  );
+
+  const moveToOffset = useCallback(
+    (offset: number): void => {
+      const [newRow, newCol] = offsetToLogicalPos(text, offset);
+      setCursorRow(newRow);
+      setCursorCol(newCol);
+      setPreferredCol(null);
+      dbg('moveToOffset', { offset, newCursor: [newRow, newCol] });
+    },
+    [text, setPreferredCol],
+  );
+
   const returnValue: TextBuffer = {
     lines,
     text,
@@ -1199,6 +1274,8 @@ export function useTextBuffer({
     undo,
     redo,
     replaceRange,
+    replaceRangeByOffset,
+    moveToOffset, // Added here
     deleteWordLeft,
     deleteWordRight,
     killLineRight,
@@ -1342,4 +1419,10 @@ export interface TextBuffer {
   copy: () => string | null;
   paste: () => boolean;
   startSelection: () => void;
+  replaceRangeByOffset: (
+    startOffset: number,
+    endOffset: number,
+    replacementText: string,
+  ) => boolean;
+  moveToOffset(offset: number): void;
 }