feat: Add --safe flag for file edit preview mode

- Add --safe CLI flag to prevent actual file modifications
- Implement CatConfig and FileEditorConfig for type-safe configuration
- Display safe mode indicator in EditAction component
- FileEditor creates diffs but skips file replacement in safe mode

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: koki-develop

src/App.tsx

@@ -7,9 +7,12 @@ import { Spinner } from "./components/Spinner";
 import type { Message } from "./components/types";
 import { Cat } from "./lib/cat";
 
-const cat = new Cat();
+type AppProps = {
+  safeMode: boolean;
+};
 
-export const App: React.FC = () => {
+export const App: React.FC<AppProps> = ({ safeMode }) => {
+  const cat = new Cat({ safeMode });
   const [messages, setMessages] = useState<Message[]>([]);
   const [input, setInput] = useState("");
   const [isLoading, setIsLoading] = useState(false);

src/components/EditAction.tsx

@@ -52,6 +52,9 @@ export const EditAction: React.FC<EditActionProps> = ({ action }) => {
       <Text>
         <Text color="green">⏺</Text> <Text bold>Update</Text>(
         {action.diff.fileName})
+        {action.safeMode && (
+          <Text color="yellow"> [SAFE MODE - No actual changes]</Text>
+        )}
       </Text>
       <Box paddingLeft={2} paddingY={1}>
         <Text>{formatDiffs(action.diff.diffs)}</Text>

src/components/types.ts

@@ -3,6 +3,7 @@ export type Action = EditAction;
 export type EditAction = {
   type: "edit";
   diff: FileDiff;
+  safeMode: boolean;
 };
 
 export type FileDiff = {
@@ -22,3 +23,11 @@ export type Message = {
   sender: "user" | "cat";
   action?: Action;
 };
+
+export type CatConfig = {
+  safeMode: boolean;
+};
+
+export type FileEditorConfig = {
+  safeMode: boolean;
+};

src/index.tsx

@@ -18,10 +18,11 @@ const program = new Command();
 program
   .name("cat-code")
   .version(packageJson.version)
-  .action(() => {
+  .option("--safe", "enable safe mode (no actual file modifications)")
+  .action((options) => {
     console.log(logo);
 
-    render(<App />, {
+    render(<App safeMode={!!options.safe} />, {
       exitOnCtrlC: false, // Disable default Ctrl+C exit behavior
     });
   });

src/lib/cat.ts

@@ -1,4 +1,4 @@
-import type { Action } from "../components/types";
+import type { Action, CatConfig } from "../components/types";
 import { FileEditor } from "./fileEditor";
 
 export type CatResponse = {
@@ -60,7 +60,13 @@ const emotionKeywords: Record<Emotion, string[]> = {
 } as const;
 
 export class Cat {
-  private fileEditor = new FileEditor();
+  private fileEditor: FileEditor;
+  private safeMode: boolean;
+
+  constructor(config: CatConfig) {
+    this.safeMode = config.safeMode;
+    this.fileEditor = new FileEditor({ safeMode: config.safeMode });
+  }
 
   private detectEmotion(message: string): Emotion | null {
     const lowerMessage = message.toLowerCase();
@@ -99,7 +105,7 @@ export class Cat {
       if (diff) {
         return {
           text: catText,
-          action: { type: "edit", diff },
+          action: { type: "edit", diff, safeMode: this.safeMode },
         };
       }
     }

src/lib/fileEditor.ts

@@ -2,7 +2,7 @@ import { createReadStream, createWriteStream } from "node:fs";
 import { rename } from "node:fs/promises";
 import { createInterface } from "node:readline";
 import { glob } from "glob";
-import type { Diff, FileDiff } from "../components/types";
+import type { Diff, FileDiff, FileEditorConfig } from "../components/types";
 import { Git } from "./git";
 
 const textFileExtensions: string[] = [
@@ -54,6 +54,11 @@ const textFileExtensions: string[] = [
 
 export class FileEditor {
   private git = new Git();
+  private safeMode: boolean;
+
+  constructor(config: FileEditorConfig) {
+    this.safeMode = config.safeMode;
+  }
   // Text file extension patterns
   private readonly textFilePatterns = textFileExtensions.map(
     (ext) => `**/*.${ext}`,
@@ -204,8 +209,14 @@ export class FileEditor {
     writeStream.end();
     await new Promise<void>((resolve) => writeStream.on("finish", resolve));
 
-    // Atomically replace original file
-    await rename(tempPath, filePath);
+    // Atomically replace original file (only if not in safe mode)
+    if (!this.safeMode) {
+      await rename(tempPath, filePath);
+    } else {
+      // In safe mode, delete the temporary file
+      const { unlink } = await import("node:fs/promises");
+      await unlink(tempPath);
+    }
 
     return { diffs };
   }