feat: complete v0.3.1 agent workflow

internal/tools/file.go

@@ -13,6 +13,7 @@ import (
 	"sort"
 	"strings"
 
+	"agentu/internal/safeio"
 	"agentu/pkg/llm"
 )
 
@@ -83,6 +84,33 @@ func NewFileWriteTool(workingDir string) *FileWriteTool {
 }
 func (*FileWriteTool) Mutates() bool { return true }
 
+func (t *FileWriteTool) Preview(ctx context.Context, raw json.RawMessage) (string, error) {
+	var args fileWriteArgs
+	if err := json.Unmarshal(raw, &args); err != nil {
+		return "", fmt.Errorf("parse arguments: %w", err)
+	}
+	action := "write"
+	if args.Append {
+		action = "append"
+	}
+	return fmt.Sprintf("%s %d bytes to %s", action, len(args.Content), args.Path), ctx.Err()
+}
+
+func (t *FileWriteTool) TargetPaths(raw json.RawMessage) ([]string, error) {
+	var args fileWriteArgs
+	if err := json.Unmarshal(raw, &args); err != nil {
+		return nil, fmt.Errorf("parse arguments: %w", err)
+	}
+	if strings.TrimSpace(args.Path) == "" {
+		return nil, errors.New("path is required")
+	}
+	path, err := resolvePathForWrite(t.workingDir, args.Path)
+	if err != nil {
+		return nil, err
+	}
+	return []string{path}, nil
+}
+
 func (t *FileWriteTool) Definition() llm.Tool {
 	return llm.Tool{
 		Type: "function",
@@ -117,28 +145,28 @@ func (t *FileWriteTool) Execute(ctx context.Context, raw json.RawMessage) (strin
 	if strings.TrimSpace(args.Path) == "" {
 		return "", errors.New("path is required")
 	}
-	path, err := resolvePath(t.workingDir, args.Path)
+	path, err := resolvePathForWrite(t.workingDir, args.Path)
 	if err != nil {
 		return "", err
 	}
-	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
-		return "", err
-	}
-	flag := os.O_CREATE | os.O_WRONLY | os.O_TRUNC
-	if args.Append {
-		flag = os.O_CREATE | os.O_WRONLY | os.O_APPEND
-	}
-	file, err := os.OpenFile(path, flag, 0o644)
-	if err != nil {
-		return "", err
-	}
-	defer file.Close()
-	if _, err := file.WriteString(args.Content); err != nil {
-		return "", err
-	}
 	if err := ctx.Err(); err != nil {
 		return "", err
 	}
+	content := []byte(args.Content)
+	perm := os.FileMode(0o644)
+	if info, statErr := os.Stat(path); statErr == nil {
+		perm = info.Mode().Perm()
+	}
+	if args.Append {
+		existing, readErr := os.ReadFile(path)
+		if readErr != nil && !os.IsNotExist(readErr) {
+			return "", readErr
+		}
+		content = append(existing, content...)
+	}
+	if err := safeio.AtomicWriteFile(path, content, perm); err != nil {
+		return "", err
+	}
 	action := "wrote"
 	if args.Append {
 		action = "appended"