package sysfs

import (
	"os"
	"path"
	"regexp"
)

// A File represents basic IO interactions with the underlying file system
type File interface {
	Write(b []byte) (n int, err error)
	WriteString(s string) (ret int, err error)
	Sync() (err error)
	Read(b []byte) (n int, err error)
	ReadAt(b []byte, off int64) (n int, err error)
	Seek(offset int64, whence int) (ret int64, err error)
	Fd() uintptr
	Close() error
}

// Filesystem opens files and returns either a native file system or user defined
type Filesystem interface {
	OpenFile(name string, flag int, perm os.FileMode) (file File, err error)
	Stat(name string) (os.FileInfo, error)
	Find(baseDir string, pattern string) (dirs []string, err error)
}

// NativeFilesystem represents the native file system implementation
type NativeFilesystem struct{}

// Default to the host filesystem.
var fs Filesystem = &NativeFilesystem{}

// SetFilesystem sets the filesystem implementation.
func SetFilesystem(f Filesystem) {
	fs = f
}

// OpenFile calls os.OpenFile().
func (fs *NativeFilesystem) OpenFile(name string, flag int, perm os.FileMode) (file File, err error) {
	return os.OpenFile(name, flag, perm)
}

// Stat calls os.Stat()
func (fs *NativeFilesystem) Stat(name string) (os.FileInfo, error) {
	return os.Stat(name)
}

// Find returns all items (files or folders) below the given directory matching the given pattern.
func (fs *NativeFilesystem) Find(baseDir string, pattern string) ([]string, error) {
	reg, err := regexp.Compile(pattern)
	if err != nil {
		return nil, err
	}

	items, err := os.ReadDir(baseDir)
	if err != nil {
		return nil, err
	}

	var found []string
	for _, item := range items {
		if reg.MatchString(item.Name()) {
			found = append(found, path.Join(baseDir, item.Name()))

		}
	}
	return found, nil
}

// OpenFile calls either the NativeFilesystem or user defined OpenFile
func OpenFile(name string, flag int, perm os.FileMode) (file File, err error) {
	return fs.OpenFile(name, flag, perm)
}

// Stat calls either the NativeFilesystem or user defined Stat
func Stat(name string) (os.FileInfo, error) {
	return fs.Stat(name)
}

// Find calls either the implementation with NativeFilesystem or user defined Find
func Find(baseDir string, pattern string) ([]string, error) {
	return fs.Find(baseDir, pattern)
}