Adding in a history buffer (#38)

Up and down arrows traverse the command history.

packages/cli/src/ui/hooks/useGeminiStream.ts

@@ -112,7 +112,7 @@ export const useGeminiStream = (
 
           const maybeCommand = trimmedQuery.split(/\s+/)[0];
           if (allowlistedCommands.includes(maybeCommand)) {
-            exec(trimmedQuery, (error, stdout, stderr) => {
+            exec(trimmedQuery, (error, stdout) => {
               const timestamp = getNextMessageId(userMessageTimestamp);
               // TODO: handle stderr, error
               addHistoryItem(

packages/cli/src/ui/hooks/useInputHistory.ts

@@ -0,0 +1,125 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { useState, useCallback } from 'react';
+import { useInput } from 'ink';
+
+// Props for the hook
+interface UseInputHistoryProps {
+  userMessages: readonly string[]; // History of user messages
+  onSubmit: (value: string) => void; // Original submit function from App
+  isActive: boolean; // To enable/disable the useInput hook
+}
+
+// Return type of the hook
+interface UseInputHistoryReturn {
+  query: string; // The current input query managed by the hook
+  setQuery: React.Dispatch<React.SetStateAction<string>>; // Setter for the query
+  handleSubmit: (value: string) => void; // Wrapped submit handler
+  inputKey: number; // Key to force input reset
+}
+
+export function useInputHistory({
+  userMessages,
+  onSubmit,
+  isActive,
+}: UseInputHistoryProps): UseInputHistoryReturn {
+  const [query, setQuery] = useState(''); // Hook manages its own query state
+  const [historyIndex, setHistoryIndex] = useState<number>(-1); // -1 means current query
+  const [originalQueryBeforeNav, setOriginalQueryBeforeNav] =
+    useState<string>('');
+  const [inputKey, setInputKey] = useState<number>(0); // Key for forcing input reset
+
+  // Function to reset navigation state, called on submit or manual reset
+  const resetHistoryNav = useCallback(() => {
+    setHistoryIndex(-1);
+    setOriginalQueryBeforeNav('');
+  }, []);
+
+  // Wrapper for the onSubmit prop to include resetting history navigation
+  const handleSubmit = useCallback(
+    (value: string) => {
+      const trimmedValue = value.trim();
+      if (trimmedValue) {
+        // Only submit non-empty values
+        onSubmit(trimmedValue); // Call the original submit function
+      }
+      setQuery(''); // Clear the input field managed by this hook
+      resetHistoryNav(); // Reset history state
+      // Don't increment inputKey here, only on nav changes
+    },
+    [onSubmit, resetHistoryNav],
+  );
+
+  useInput(
+    (input, key) => {
+      // Do nothing if the hook is not active
+      if (!isActive) {
+        return;
+      }
+
+      let didNavigate = false;
+
+      if (key.upArrow) {
+        if (userMessages.length === 0) return;
+
+        let nextIndex = historyIndex;
+        if (historyIndex === -1) {
+          // Starting navigation UP, save current input
+          setOriginalQueryBeforeNav(query);
+          nextIndex = 0; // Go to the most recent item (index 0 in reversed view)
+        } else if (historyIndex < userMessages.length - 1) {
+          // Continue navigating UP (towards older items)
+          nextIndex = historyIndex + 1;
+        } else {
+          return; // Already at the oldest item
+        }
+
+        if (nextIndex !== historyIndex) {
+          setHistoryIndex(nextIndex);
+          // History is ordered newest to oldest, so access from the end
+          const newValue = userMessages[userMessages.length - 1 - nextIndex];
+          setQuery(newValue);
+          setInputKey((k) => k + 1); // Increment key on navigation change
+          didNavigate = true;
+        }
+      } else if (key.downArrow) {
+        if (historyIndex === -1) return; // Already at the bottom (current input)
+
+        const nextIndex = historyIndex - 1; // Move towards more recent items / current input
+        setHistoryIndex(nextIndex);
+
+        if (nextIndex === -1) {
+          // Restore original query
+          setQuery(originalQueryBeforeNav);
+        } else {
+          // Set query based on reversed index
+          const newValue = userMessages[userMessages.length - 1 - nextIndex];
+          setQuery(newValue);
+        }
+        setInputKey((k) => k + 1); // Increment key on navigation change
+        didNavigate = true;
+      } else {
+        // If user types anything other than arrows while navigating, reset history navigation state
+        if (historyIndex !== -1 && !didNavigate) {
+          // Check if it's a key that modifies input content
+          if (input || key.backspace || key.delete) {
+            resetHistoryNav();
+            // The actual query state update for typing is handled by the component's onChange calling setQuery
+          }
+        }
+      }
+    },
+    { isActive }, // Pass isActive to useInput
+  );
+
+  return {
+    query,
+    setQuery, // Return the hook's setQuery
+    handleSubmit, // Return the wrapped submit handler
+    inputKey, // Return the key
+  };
+}