package real

import (
	"io"
	"os"
	"path/filepath"
	"pad/internal/io/pool/types"
)

// RealFileSystem implements the pool.FileSystem interface using the real OS filesystem.
type RealFileSystem struct {
	Root string
}

func (fs *RealFileSystem) ReadDir(path string) ([]types.DirEntry, error) {
	entries, err := os.ReadDir(filepath.Join(fs.Root, path))
	if err != nil {
		return nil, err
	}
	var res []types.DirEntry
	for _, e := range entries {
		res = append(res, &realDirEntry{e})
	}
	return res, nil
}

func (fs *RealFileSystem) DirExists(path string) bool {
	info, err := os.Stat(filepath.Join(fs.Root, path))
	return err == nil && info.IsDir()
}

func (fs *RealFileSystem) FileExists(path string) bool {
	info, err := os.Stat(filepath.Join(fs.Root, path))
	return err == nil && !info.IsDir()
}

func (fs *RealFileSystem) ReadFile(path string) ([]byte, error) {
	return os.ReadFile(filepath.Join(fs.Root, path))
}

func (fs *RealFileSystem) ReadFileAt(path string, offset, size int) ([]byte, error) {
	fullPath := filepath.Join(fs.Root, path)
	f, err := os.Open(fullPath)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	buf := make([]byte, size)
	n, err := f.ReadAt(buf, int64(offset))
	if err != nil && err != io.EOF {
		return nil, err
	}
	return buf[:n], nil
}

func (fs *RealFileSystem) WriteFile(path string, content []byte) error {
	// Simple write for backward compatibility if needed, 
	// but defer to Atomic implementation.
	return fs.WriteFileAtomic(path, content)
}

func (fs *RealFileSystem) WriteFileAtomic(path string, content []byte) error {
	// Atomic write implementation
	fullPath := filepath.Join(fs.Root, path)
	// Temp file in the same directory as the target to ensure same filesystem rename
	tmpPath := filepath.Join(filepath.Dir(fullPath), "."+filepath.Base(path)+".tmp")
	
	if err := os.MkdirAll(filepath.Dir(tmpPath), 0755); err != nil {
		return err
	}
	
	if err := os.WriteFile(tmpPath, content, 0644); err != nil {
		return err
	}
	
	return os.Rename(tmpPath, fullPath)
}

func (fs *RealFileSystem) DeleteFile(path string) error {
	return os.Remove(filepath.Join(fs.Root, path))
}

func (fs *RealFileSystem) CreateDir(path string) error {
	return os.MkdirAll(filepath.Join(fs.Root, path), 0755)
}

// realDirEntry wraps os.DirEntry
type realDirEntry struct {
	entry os.DirEntry
}

func (e *realDirEntry) Name() string { return e.entry.Name() }
func (e *realDirEntry) IsDir() bool  { return e.entry.IsDir() }
func (e *realDirEntry) Info() (os.FileInfo, error) { return e.entry.Info() }