package services

import (
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"
)

type FSService struct {
	root string
}

type Entry struct {
	Name    string    `json:"name"`
	Path    string    `json:"path"`
	Size    int64     `json:"size"`
	IsDir   bool      `json:"isDir"`
	ModTime time.Time `json:"modTime"`
}

func NewFSService(root string) *FSService {
	return &FSService{root: filepath.Clean(root)}
}

func (s *FSService) ResolvePath(raw string) (string, error) {
	clean := filepath.Clean(filepath.Join(s.root, raw))
	rootWithSep := s.root + string(os.PathSeparator)
	if clean != s.root && !strings.HasPrefix(clean, rootWithSep) {
		return "", errors.New("path out of root directory")
	}
	return clean, nil
}

func (s *FSService) List(raw string) ([]Entry, error) {
	path, err := s.ResolvePath(raw)
	if err != nil {
		return nil, err
	}
	entries, err := os.ReadDir(path)
	if err != nil {
		return nil, fmt.Errorf("read dir: %w", err)
	}

	result := make([]Entry, 0, len(entries))
	for _, e := range entries {
		info, err := e.Info()
		if err != nil {
			continue
		}
		full := filepath.Join(path, e.Name())
		rel, _ := filepath.Rel(s.root, full)
		result = append(result, Entry{
			Name:    e.Name(),
			Path:    filepath.ToSlash(rel),
			Size:    info.Size(),
			IsDir:   e.IsDir(),
			ModTime: info.ModTime(),
		})
	}

	sort.Slice(result, func(i, j int) bool {
		if result[i].IsDir != result[j].IsDir {
			return result[i].IsDir
		}
		return strings.ToLower(result[i].Name) < strings.ToLower(result[j].Name)
	})
	return result, nil
}

func (s *FSService) Delete(raw string) error {
	path, err := s.ResolvePath(raw)
	if err != nil {
		return err
	}
	return os.RemoveAll(path)
}

func (s *FSService) Rename(rawPath, newName string) error {
	if strings.Contains(newName, "/") || strings.Contains(newName, "\\") {
		return errors.New("invalid name")
	}
	path, err := s.ResolvePath(rawPath)
	if err != nil {
		return err
	}
	target := filepath.Join(filepath.Dir(path), newName)
	target, err = s.ResolvePath(mustRel(s.root, target))
	if err != nil {
		return err
	}
	return os.Rename(path, target)
}

func (s *FSService) Move(fromRaw, toRaw string) error {
	fromPath, err := s.ResolvePath(fromRaw)
	if err != nil {
		return err
	}
	toPath, err := s.ResolvePath(toRaw)
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(toPath), 0o755); err != nil {
		return err
	}
	return os.Rename(fromPath, toPath)
}

func (s *FSService) SaveUploadedFile(src io.Reader, targetRaw string) error {
	targetPath, err := s.ResolvePath(targetRaw)
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(targetPath), 0o755); err != nil {
		return err
	}
	dst, err := os.Create(targetPath)
	if err != nil {
		return err
	}
	defer dst.Close()

	_, err = io.Copy(dst, src)
	return err
}

func mustRel(root, target string) string {
	rel, err := filepath.Rel(root, target)
	if err != nil {
		return "."
	}
	return rel
}