picoclaw/pkg/tools/filesystem.go

package tools

import (
	"context"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
	"strings"
	"time"
)

// validatePath ensures the given path is within the workspace if restrict is true.
func validatePath(path, workspace string, restrict bool) (string, error) {
	if workspace == "" {
		return path, fmt.Errorf("workspace is not defined")
	}

	absWorkspace, err := filepath.Abs(workspace)
	if err != nil {
		return "", fmt.Errorf("failed to resolve workspace path: %w", err)
	}

	var absPath string
	if filepath.IsAbs(path) {
		absPath = filepath.Clean(path)
	} else {
		absPath, err = filepath.Abs(filepath.Join(absWorkspace, path))
		if err != nil {
			return "", fmt.Errorf("failed to resolve file path: %w", err)
		}
	}

	if restrict {
		if !isWithinWorkspace(absPath, absWorkspace) {
			return "", fmt.Errorf("access denied: path is outside the workspace")
		}

		var resolved string
		workspaceReal := absWorkspace
		if resolved, err = filepath.EvalSymlinks(absWorkspace); err == nil {
			workspaceReal = resolved
		}

		if resolved, err = filepath.EvalSymlinks(absPath); err == nil {
			if !isWithinWorkspace(resolved, workspaceReal) {
				return "", fmt.Errorf("access denied: symlink resolves outside workspace")
			}
		} else if os.IsNotExist(err) {
			var parentResolved string
			if parentResolved, err = resolveExistingAncestor(filepath.Dir(absPath)); err == nil {
				if !isWithinWorkspace(parentResolved, workspaceReal) {
					return "", fmt.Errorf("access denied: symlink resolves outside workspace")
				}
			} else if !os.IsNotExist(err) {
				return "", fmt.Errorf("failed to resolve path: %w", err)
			}
		} else {
			return "", fmt.Errorf("failed to resolve path: %w", err)
		}
	}

	return absPath, nil
}

func resolveExistingAncestor(path string) (string, error) {
	for current := filepath.Clean(path); ; current = filepath.Dir(current) {
		if resolved, err := filepath.EvalSymlinks(current); err == nil {
			return resolved, nil
		} else if !os.IsNotExist(err) {
			return "", err
		}
		if filepath.Dir(current) == current {
			return "", os.ErrNotExist
		}
	}
}

func isWithinWorkspace(candidate, workspace string) bool {
	rel, err := filepath.Rel(filepath.Clean(workspace), filepath.Clean(candidate))
	return err == nil && filepath.IsLocal(rel)
}

type ReadFileTool struct {
	fs fileSystem
}

func NewReadFileTool(workspace string, restrict bool) *ReadFileTool {
	var fs fileSystem
	if restrict {
		fs = &sandboxFs{workspace: workspace}
	} else {
		fs = &hostFs{}
	}
	return &ReadFileTool{fs: fs}
}

func (t *ReadFileTool) Name() string {
	return "read_file"
}

func (t *ReadFileTool) Description() string {
	return "Read the contents of a file"
}

func (t *ReadFileTool) Parameters() map[string]any {
	return map[string]any{
		"type": "object",
		"properties": map[string]any{
			"path": map[string]any{
				"type":        "string",
				"description": "Path to the file to read",
			},
		},
		"required": []string{"path"},
	}
}

func (t *ReadFileTool) Execute(ctx context.Context, args map[string]any) *ToolResult {
	path, ok := args["path"].(string)
	if !ok {
		return ErrorResult("path is required")
	}

	content, err := t.fs.ReadFile(path)
	if err != nil {
		return ErrorResult(err.Error())
	}
	return NewToolResult(string(content))
}

type WriteFileTool struct {
	fs fileSystem
}

func NewWriteFileTool(workspace string, restrict bool) *WriteFileTool {
	var fs fileSystem
	if restrict {
		fs = &sandboxFs{workspace: workspace}
	} else {
		fs = &hostFs{}
	}
	return &WriteFileTool{fs: fs}
}

func (t *WriteFileTool) Name() string {
	return "write_file"
}

func (t *WriteFileTool) Description() string {
	return "Write content to a file"
}

func (t *WriteFileTool) Parameters() map[string]any {
	return map[string]any{
		"type": "object",
		"properties": map[string]any{
			"path": map[string]any{
				"type":        "string",
				"description": "Path to the file to write",
			},
			"content": map[string]any{
				"type":        "string",
				"description": "Content to write to the file",
			},
		},
		"required": []string{"path", "content"},
	}
}

func (t *WriteFileTool) Execute(ctx context.Context, args map[string]any) *ToolResult {
	path, ok := args["path"].(string)
	if !ok {
		return ErrorResult("path is required")
	}

	content, ok := args["content"].(string)
	if !ok {
		return ErrorResult("content is required")
	}

	if err := t.fs.WriteFile(path, []byte(content)); err != nil {
		return ErrorResult(err.Error())
	}

	return SilentResult(fmt.Sprintf("File written: %s", path))
}

type ListDirTool struct {
	fs fileSystem
}

func NewListDirTool(workspace string, restrict bool) *ListDirTool {
	var fs fileSystem
	if restrict {
		fs = &sandboxFs{workspace: workspace}
	} else {
		fs = &hostFs{}
	}
	return &ListDirTool{fs: fs}
}

func (t *ListDirTool) Name() string {
	return "list_dir"
}

func (t *ListDirTool) Description() string {
	return "List files and directories in a path"
}

func (t *ListDirTool) Parameters() map[string]any {
	return map[string]any{
		"type": "object",
		"properties": map[string]any{
			"path": map[string]any{
				"type":        "string",
				"description": "Path to list",
			},
		},
		"required": []string{"path"},
	}
}

func (t *ListDirTool) Execute(ctx context.Context, args map[string]any) *ToolResult {
	path, ok := args["path"].(string)
	if !ok {
		path = "."
	}

	entries, err := t.fs.ReadDir(path)
	if err != nil {
		return ErrorResult(fmt.Sprintf("failed to read directory: %v", err))
	}
	return formatDirEntries(entries)
}

func formatDirEntries(entries []os.DirEntry) *ToolResult {
	var result strings.Builder
	for _, entry := range entries {
		if entry.IsDir() {
			result.WriteString("DIR:  " + entry.Name() + "\n")
		} else {
			result.WriteString("FILE: " + entry.Name() + "\n")
		}
	}
	return NewToolResult(result.String())
}

// fileSystem abstracts reading, writing, and listing files, allowing both
// unrestricted (host filesystem) and sandbox (os.Root) implementations to share the same polymorphic interface.
type fileSystem interface {
	ReadFile(path string) ([]byte, error)
	WriteFile(path string, data []byte) error
	ReadDir(path string) ([]os.DirEntry, error)
}

// hostFs is an unrestricted fileReadWriter that operates directly on the host filesystem.
type hostFs struct{}

func (h *hostFs) ReadFile(path string) ([]byte, error) {
	content, err := os.ReadFile(path)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, fmt.Errorf("failed to read file: file not found: %w", err)
		}
		if os.IsPermission(err) {
			return nil, fmt.Errorf("failed to read file: access denied: %w", err)
		}
		return nil, fmt.Errorf("failed to read file: %w", err)
	}
	return content, nil
}

func (h *hostFs) ReadDir(path string) ([]os.DirEntry, error) {
	return os.ReadDir(path)
}

func (h *hostFs) WriteFile(path string, data []byte) error {
	dir := filepath.Dir(path)
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return fmt.Errorf("failed to create parent directories: %w", err)
	}

	// We use a "write-then-rename" pattern here to ensure an atomic write.
	// This prevents the target file from being left in a truncated or partial state
	// if the operation is interrupted, as the rename operation is atomic on Linux.
	tmpPath := fmt.Sprintf("%s.%d.tmp", path, time.Now().UnixNano())
	if err := os.WriteFile(tmpPath, data, 0o644); err != nil {
		os.Remove(tmpPath) // Ensure cleanup of partial/empty temp file
		return fmt.Errorf("failed to write temp file: %w", err)
	}

	if err := os.Rename(tmpPath, path); err != nil {
		os.Remove(tmpPath)
		return fmt.Errorf("failed to replace original file: %w", err)
	}
	return nil
}

// sandboxFs is a sandboxed fileSystem that operates within a strictly defined workspace using os.Root.
type sandboxFs struct {
	workspace string
}

func (r *sandboxFs) execute(path string, fn func(root *os.Root, relPath string) error) error {
	if r.workspace == "" {
		return fmt.Errorf("workspace is not defined")
	}

	root, err := os.OpenRoot(r.workspace)
	if err != nil {
		return fmt.Errorf("failed to open workspace: %w", err)
	}
	defer root.Close()

	relPath, err := getSafeRelPath(r.workspace, path)
	if err != nil {
		return err
	}

	return fn(root, relPath)
}

func (r *sandboxFs) ReadFile(path string) ([]byte, error) {
	var content []byte
	err := r.execute(path, func(root *os.Root, relPath string) error {
		fileContent, err := root.ReadFile(relPath)
		if err != nil {
			if os.IsNotExist(err) {
				return fmt.Errorf("failed to read file: file not found: %w", err)
			}
			// os.Root returns "escapes from parent" for paths outside the root
			if os.IsPermission(err) || strings.Contains(err.Error(), "escapes from parent") ||
				strings.Contains(err.Error(), "permission denied") {
				return fmt.Errorf("failed to read file: access denied: %w", err)
			}
			return fmt.Errorf("failed to read file: %w", err)
		}
		content = fileContent
		return nil
	})
	return content, err
}

func (r *sandboxFs) WriteFile(path string, data []byte) error {
	return r.execute(path, func(root *os.Root, relPath string) error {
		dir := filepath.Dir(relPath)
		if dir != "." && dir != "/" {
			if err := root.MkdirAll(dir, 0o755); err != nil {
				return fmt.Errorf("failed to create parent directories: %w", err)
			}
		}

		// We use a "write-then-rename" pattern here to ensure an atomic write.
		// This prevents the target file from being left in a truncated or partial state
		// if the operation is interrupted, as the rename operation is atomic on Linux.
		tmpRelPath := fmt.Sprintf("%s.%d.tmp", relPath, time.Now().UnixNano())

		if err := root.WriteFile(tmpRelPath, data, 0o644); err != nil {
			root.Remove(tmpRelPath) // Ensure cleanup of partial/empty temp file
			return fmt.Errorf("failed to write to temp file: %w", err)
		}

		if err := root.Rename(tmpRelPath, relPath); err != nil {
			root.Remove(tmpRelPath)
			return fmt.Errorf("failed to rename temp file over target: %w", err)
		}
		return nil
	})
}

func (r *sandboxFs) ReadDir(path string) ([]os.DirEntry, error) {
	var entries []os.DirEntry
	err := r.execute(path, func(root *os.Root, relPath string) error {
		dirEntries, err := fs.ReadDir(root.FS(), relPath)
		if err != nil {
			return err
		}
		entries = dirEntries
		return nil
	})
	return entries, err
}

// Helper to get a safe relative path for os.Root usage
func getSafeRelPath(workspace, path string) (string, error) {
	if workspace == "" {
		return "", fmt.Errorf("workspace is not defined")
	}

	rel := filepath.Clean(path)
	if filepath.IsAbs(rel) {
		var err error
		rel, err = filepath.Rel(workspace, rel)
		if err != nil {
			return "", fmt.Errorf("failed to calculate relative path: %w", err)
		}
	}

	if !filepath.IsLocal(rel) {
		return "", fmt.Errorf("path escapes workspace: %s", path)
	}

	return rel, nil
}