package files

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

type FileInfo struct {
	Name  string     `json:"name"`
	Path  string     `json:"path"`
	IsDir bool       `json:"isDir"`
	Children []FileInfo `json:"children,omitempty"`
}

// UserDir returns the base directory for a user's files.
func UserDir(dataDir, userID string) string {
	return filepath.Join(dataDir, "files", userID)
}

// EnsureUserDir creates the user's file directory if it doesn't exist.
func EnsureUserDir(dataDir, userID string) error {
	return os.MkdirAll(UserDir(dataDir, userID), 0755)
}

// ReadFile reads a markdown file for a user.
func ReadFile(dataDir, userID, relPath string) (string, error) {
	p := safePath(dataDir, userID, relPath)
	if p == "" {
		return "", os.ErrPermission
	}
	b, err := os.ReadFile(p)
	return string(b), err
}

// WriteFile writes content to a markdown file for a user.
func WriteFile(dataDir, userID, relPath, content string) error {
	p := safePath(dataDir, userID, relPath)
	if p == "" {
		return os.ErrPermission
	}
	if err := os.MkdirAll(filepath.Dir(p), 0755); err != nil {
		return err
	}
	return os.WriteFile(p, []byte(content), 0644)
}

// CreateFolder creates a directory for a user.
func CreateFolder(dataDir, userID, relPath string) error {
	p := safePath(dataDir, userID, relPath)
	if p == "" {
		return os.ErrPermission
	}
	return os.MkdirAll(p, 0755)
}

// DeleteFile removes a file or folder for a user.
func DeleteFile(dataDir, userID, relPath string) error {
	p := safePath(dataDir, userID, relPath)
	if p == "" {
		return os.ErrPermission
	}
	return os.RemoveAll(p)
}

// MoveFile moves a file or folder to a new path.
func MoveFile(dataDir, userID, fromRel, toRel string) error {
	from := safePath(dataDir, userID, fromRel)
	to := safePath(dataDir, userID, toRel)
	if from == "" || to == "" {
		return os.ErrPermission
	}
	if err := os.MkdirAll(filepath.Dir(to), 0755); err != nil {
		return err
	}
	return os.Rename(from, to)
}

// ListTree returns the file tree for a user.
func ListTree(dataDir, userID string) ([]FileInfo, error) {
	root := UserDir(dataDir, userID)
	if err := os.MkdirAll(root, 0755); err != nil {
		return nil, err
	}
	return listDir(root, "")
}

func listDir(base, rel string) ([]FileInfo, error) {
	dir := filepath.Join(base, rel)
	entries, err := os.ReadDir(dir)
	if err != nil {
		return nil, err
	}
	var result []FileInfo
	for _, e := range entries {
		entryRel := filepath.Join(rel, e.Name())
		info := FileInfo{
			Name:  e.Name(),
			Path:  entryRel,
			IsDir: e.IsDir(),
		}
		if e.IsDir() {
			children, err := listDir(base, entryRel)
			if err == nil {
				info.Children = children
			}
		}
		result = append(result, info)
	}
	return result, nil
}

// safePath validates and returns the absolute path, preventing traversal.
func safePath(dataDir, userID, relPath string) string {
	if strings.Contains(relPath, "..") {
		return ""
	}
	root := UserDir(dataDir, userID)
	p := filepath.Join(root, filepath.Clean(relPath))
	if !strings.HasPrefix(p, root) {
		return ""
	}
	return p
}

// GetCreatedTime returns the file's modification time as ISO string.
func GetCreatedTime(dataDir, userID, relPath string) string {
	p := safePath(dataDir, userID, relPath)
	if p == "" {
		return ""
	}
	info, err := os.Stat(p)
	if err != nil {
		return ""
	}
	return info.ModTime().UTC().Format("2006-01-02T15:04:05Z")
}