package fs

import (
	"os"
	"path/filepath"
	"sort"
	"strings"

	"codespace/internal/util"
)

// LocalFS implements FileSystem bound to a single workspace root directory.
type LocalFS struct {
	root string
}

// NewLocal creates a LocalFS whose root is absolute and cleaned if possible.
func NewLocal(root string) *LocalFS {
	abs, err := filepath.Abs(root)
	if err != nil {
		abs = filepath.Clean(root)
	}
	return &LocalFS{root: abs}
}

// resolve validates path, cleans it, and returns the absolute path on disk
// plus the workspace-relative form. It rejects paths that escape the root.
func (l *LocalFS) resolve(path string) (abs string, rel string, err error) {
	rel, err = util.CleanRelative(path)
	if err != nil {
		return "", "", err
	}
	abs = filepath.Join(l.root, rel)
	// Final containment check: ensure abs is within root.
	if abs != l.root && !strings.HasPrefix(abs, l.root+string(filepath.Separator)) {
		return "", "", util.New(util.CodeBadRequest, "path escapes workspace root")
	}
	return abs, rel, nil
}

// List returns sorted directory entries for path.
func (l *LocalFS) List(path string) ([]FileInfo, error) {
	abs, rel, err := l.resolve(path)
	if err != nil {
		return nil, err
	}
	entries, err := os.ReadDir(abs)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, util.New(util.CodeNotFound, "path not found")
		}
		return nil, util.Wrap(util.CodeInternal, "failed to list directory", err)
	}
	result := make([]FileInfo, 0, len(entries))
	for _, e := range entries {
		info, err := e.Info()
		if err != nil {
			return nil, util.Wrap(util.CodeInternal, "failed to get file info", err)
		}
		result = append(result, FileInfo{
			Name:    e.Name(),
			Path:    filepath.Join(rel, e.Name()),
			IsDir:   e.IsDir(),
			Size:    info.Size(),
			ModTime: info.ModTime(),
		})
	}
	sort.Slice(result, func(i, j int) bool {
		return result[i].Name < result[j].Name
	})
	return result, nil
}

// Read returns the contents of path.
func (l *LocalFS) Read(path string) ([]byte, error) {
	abs, _, err := l.resolve(path)
	if err != nil {
		return nil, err
	}
	data, err := os.ReadFile(abs)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, util.New(util.CodeNotFound, "file not found")
		}
		return nil, util.Wrap(util.CodeInternal, "failed to read file", err)
	}
	return data, nil
}

// Write writes data to path, creating parent directories as needed.
func (l *LocalFS) Write(path string, data []byte) error {
	abs, _, err := l.resolve(path)
	if err != nil {
		return err
	}
	parent := filepath.Dir(abs)
	if err := os.MkdirAll(parent, 0o755); err != nil {
		return util.Wrap(util.CodeInternal, "failed to create parent directories", err)
	}
	if err := os.WriteFile(abs, data, 0o644); err != nil {
		return util.Wrap(util.CodeInternal, "failed to write file", err)
	}
	return nil
}

// Mkdir creates a directory at path.
func (l *LocalFS) Mkdir(path string) error {
	abs, _, err := l.resolve(path)
	if err != nil {
		return err
	}
	if err := os.MkdirAll(abs, 0o755); err != nil {
		return util.Wrap(util.CodeInternal, "failed to create directory", err)
	}
	return nil
}

// Remove removes path (file or directory recursively).
func (l *LocalFS) Remove(path string) error {
	abs, rel, err := l.resolve(path)
	if err != nil {
		return err
	}
	if rel == "." {
		return util.New(util.CodeBadRequest, "cannot remove workspace root")
	}
	if err := os.RemoveAll(abs); err != nil {
		return util.Wrap(util.CodeInternal, "failed to remove path", err)
	}
	return nil
}

// Rename moves oldPath to newPath, creating destination parent dirs.
func (l *LocalFS) Rename(oldPath, newPath string) error {
	oldAbs, _, err := l.resolve(oldPath)
	if err != nil {
		return err
	}
	newAbs, _, err := l.resolve(newPath)
	if err != nil {
		return err
	}
	parent := filepath.Dir(newAbs)
	if err := os.MkdirAll(parent, 0o755); err != nil {
		return util.Wrap(util.CodeInternal, "failed to create parent directories", err)
	}
	if err := os.Rename(oldAbs, newAbs); err != nil {
		return util.Wrap(util.CodeInternal, "failed to rename", err)
	}
	return nil
}

// Stat returns metadata for path.
func (l *LocalFS) Stat(path string) (*FileInfo, error) {
	abs, rel, err := l.resolve(path)
	if err != nil {
		return nil, err
	}
	info, err := os.Stat(abs)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, util.New(util.CodeNotFound, "path not found")
		}
		return nil, util.Wrap(util.CodeInternal, "failed to stat path", err)
	}
	return &FileInfo{
		Name:    filepath.Base(rel),
		Path:    rel,
		IsDir:   info.IsDir(),
		Size:    info.Size(),
		ModTime: info.ModTime(),
	}, nil
}