package wincmd

import (
	"b612.me/win32api"
	"golang.org/x/sys/windows"
	"os"
	"sync"
	"syscall"
	"time"
)

const DevNull = "NUL"

// A fileStat is the implementation of FileInfo returned by Stat and Lstat.
type FileStat struct {
	name string

	// from ByHandleFileInformation, Win32FileAttributeData and Win32finddata
	FileAttributes uint32
	CreationTime   syscall.Filetime
	LastAccessTime syscall.Filetime
	LastWriteTime  syscall.Filetime
	FileSizeHigh   uint32
	FileSizeLow    uint32

	// from Win32finddata
	Reserved0 uint32

	// what syscall.GetFileType returns
	filetype uint32

	// used to implement SameFile
	sync.Mutex
	path             string
	vol              uint32
	idxhi            uint32
	idxlo            uint32
	appendNameToPath bool
}

// newFileStatFromWin32finddata copies all required information
// from syscall.Win32finddata d into the newly created fileStat.
func newFileStatFromInformation(d *syscall.ByHandleFileInformation, name string, path string) *FileStat {
	return &FileStat{
		name:           name,
		path:           path,
		FileAttributes: d.FileAttributes,
		CreationTime:   d.CreationTime,
		LastAccessTime: d.LastAccessTime,
		LastWriteTime:  d.LastWriteTime,
		FileSizeHigh:   d.FileSizeHigh,
		FileSizeLow:    d.FileSizeLow,
	}
}

func (fs *FileStat) Name() string {
	return fs.name
}

func (fs *FileStat) IsDir() bool {
	return fs.FileAttributes&win32api.FILE_ATTRIBUTE_DIRECTORY != 0
}

func (fs *FileStat) isSymlink() bool {
	// Use instructions described at
	// https://blogs.msdn.microsoft.com/oldnewthing/20100212-00/?p=14963/
	// to recognize whether it's a symlink.
	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT == 0 {
		return false
	}
	return fs.Reserved0 == syscall.IO_REPARSE_TAG_SYMLINK ||
		fs.Reserved0 == windows.IO_REPARSE_TAG_MOUNT_POINT
}

func (fs *FileStat) Size() int64 {
	return int64(fs.FileSizeHigh)<<32 + int64(fs.FileSizeLow)
}

func (fs *FileStat) Mode() (m os.FileMode) {
	if fs == &devNullStat {
		return os.ModeDevice | os.ModeCharDevice | 0666
	}
	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_READONLY != 0 {
		m |= 0444
	} else {
		m |= 0666
	}
	if fs.isSymlink() {
		return m | os.ModeSymlink
	}
	if fs.FileAttributes&syscall.FILE_ATTRIBUTE_DIRECTORY != 0 {
		m |= os.ModeDir | 0111
	}
	switch fs.filetype {
	case syscall.FILE_TYPE_PIPE:
		m |= os.ModeNamedPipe
	case syscall.FILE_TYPE_CHAR:
		m |= os.ModeDevice | os.ModeCharDevice
	}
	return m
}

func (fs *FileStat) ModTime() time.Time {
	return time.Unix(0, fs.LastWriteTime.Nanoseconds())
}

// Sys returns syscall.Win32FileAttributeData for file fs.
func (fs *FileStat) Sys() interface{} {
	return &syscall.Win32FileAttributeData{
		FileAttributes: fs.FileAttributes,
		CreationTime:   fs.CreationTime,
		LastAccessTime: fs.LastAccessTime,
		LastWriteTime:  fs.LastWriteTime,
		FileSizeHigh:   fs.FileSizeHigh,
		FileSizeLow:    fs.FileSizeLow,
	}
}

// saveInfoFromPath saves full path of the file to be used by os.SameFile later,
// and set name from path.

// devNullStat is fileStat structure describing DevNull file ("NUL").
var devNullStat = FileStat{
	name: DevNull,
	// hopefully this will work for SameFile
	vol:   0,
	idxhi: 0,
	idxlo: 0,
}