//+private
package os2

import "core:time"
import win32 "core:sys/windows"

_fstat :: proc(fd: Handle, allocator := context.allocator) -> (File_Info, Maybe(Path_Error)) {
	if fd == 0 {
		return {}, Path_Error{err = .Invalid_Argument}
	}
	context.allocator = allocator

	path, err := _cleanpath_from_handle(fd)
	if err != nil {
		return {}, err
	}

	h := win32.HANDLE(fd)
	switch win32.GetFileType(h) {
	case win32.FILE_TYPE_PIPE, win32.FILE_TYPE_CHAR:
		fi: File_Info
		fi.fullpath = path
		fi.name = basename(path)
		fi.mode |= file_type_mode(h)
		return fi, nil
	}

	return _file_info_from_get_file_information_by_handle(path, h)
}
_stat :: proc(name: string, allocator := context.allocator) -> (File_Info, Maybe(Path_Error)) {
	return internal_stat(name, win32.FILE_FLAG_BACKUP_SEMANTICS)
}
_lstat :: proc(name: string, allocator := context.allocator) -> (File_Info, Maybe(Path_Error)) {
	return internal_stat(name, win32.FILE_FLAG_BACKUP_SEMANTICS|win32.FILE_FLAG_OPEN_REPARSE_POINT)
}
_same_file :: proc(fi1, fi2: File_Info) -> bool {
	return fi1.fullpath == fi2.fullpath
}



_stat_errno :: proc(errno: win32.DWORD) -> Path_Error {
	return Path_Error{err = Platform_Error{i32(errno)}}
}


full_path_from_name :: proc(name: string, allocator := context.allocator) -> (path: string, err: Maybe(Path_Error)) {
	context.allocator = allocator
	
	name := name
	if name == "" {
		name = "."
	}
	p := win32.utf8_to_utf16(name, context.temp_allocator)
	buf := make([dynamic]u16, 100)
	for {
		n := win32.GetFullPathNameW(raw_data(p), u32(len(buf)), raw_data(buf), nil)
		if n == 0 {
			delete(buf)
			return "", _stat_errno(win32.GetLastError())
		}
		if n <= u32(len(buf)) {
			return win32.utf16_to_utf8(buf[:n]), nil
		}
		resize(&buf, len(buf)*2)
	}

	return
}


internal_stat :: proc(name: string, create_file_attributes: u32, allocator := context.allocator) -> (fi: File_Info, e: Maybe(Path_Error)) {
	if len(name) == 0 {
		return {}, Path_Error{err = .Not_Exist}
	}

	context.allocator = allocator


	wname := win32.utf8_to_wstring(_fix_long_path(name), context.temp_allocator)
	fa: win32.WIN32_FILE_ATTRIBUTE_DATA
	ok := win32.GetFileAttributesExW(wname, win32.GetFileExInfoStandard, &fa)
	if ok && fa.dwFileAttributes & win32.FILE_ATTRIBUTE_REPARSE_POINT == 0 {
		// Not a symlink
		return _file_info_from_win32_file_attribute_data(&fa, name)
	}

	err := 0 if ok else win32.GetLastError()

	if err == win32.ERROR_SHARING_VIOLATION {
		fd: win32.WIN32_FIND_DATAW
		sh := win32.FindFirstFileW(wname, &fd)
		if sh == win32.INVALID_HANDLE_VALUE {
			e = Path_Error{err = Platform_Error{i32(win32.GetLastError())}}
			return
		}
		win32.FindClose(sh)

		return _file_info_from_win32_find_data(&fd, name)
	}

	h := win32.CreateFileW(wname, 0, 0, nil, win32.OPEN_EXISTING, create_file_attributes, nil)
	if h == win32.INVALID_HANDLE_VALUE {
		e = Path_Error{err = Platform_Error{i32(win32.GetLastError())}}
		return
	}
	defer win32.CloseHandle(h)
	return _file_info_from_get_file_information_by_handle(name, h)
}


_cleanpath_strip_prefix :: proc(buf: []u16) -> []u16 {
	buf := buf
	N := 0
	for c, i in buf {
		if c == 0 { break }
		N = i+1
	}
	buf = buf[:N]

	if len(buf) >= 4 {
		if buf[0] == '\\' &&
		   buf[1] == '\\' &&
		   buf[2] == '?'  &&
		   buf[3] == '\\' {
			buf = buf[4:]
		}
	}
	return buf
}


_cleanpath_from_handle :: proc(fd: Handle) -> (string, Maybe(Path_Error)) {
	if fd == 0 {
		return "", Path_Error{err = .Invalid_Argument}
	}
	h := win32.HANDLE(fd)

	MAX_PATH := win32.DWORD(260) + 1
	buf: []u16
	for {
		buf = make([]u16, MAX_PATH, context.temp_allocator)
		err := win32.GetFinalPathNameByHandleW(h, raw_data(buf), MAX_PATH, 0)
		switch err {
		case win32.ERROR_PATH_NOT_FOUND, win32.ERROR_INVALID_PARAMETER:
			return "", _stat_errno(err)
		case win32.ERROR_NOT_ENOUGH_MEMORY:
			MAX_PATH = MAX_PATH*2 + 1
			continue
		}
		break
	}
	return _cleanpath_from_buf(buf), nil
}

_cleanpath_from_handle_u16 :: proc(fd: Handle) -> ([]u16, Maybe(Path_Error)) {
	if fd == 0 {
		return nil, Path_Error{err = .Invalid_Argument}
	}
	h := win32.HANDLE(fd)

	MAX_PATH := win32.DWORD(260) + 1
	buf: []u16
	for {
		buf = make([]u16, MAX_PATH, context.temp_allocator)
		err := win32.GetFinalPathNameByHandleW(h, raw_data(buf), MAX_PATH, 0)
		switch err {
		case win32.ERROR_PATH_NOT_FOUND, win32.ERROR_INVALID_PARAMETER:
			return nil, _stat_errno(err)
		case win32.ERROR_NOT_ENOUGH_MEMORY:
			MAX_PATH = MAX_PATH*2 + 1
			continue
		}
		break
	}
	return _cleanpath_strip_prefix(buf), nil
}

_cleanpath_from_buf :: proc(buf: []u16) -> string {
	buf := buf
	buf = _cleanpath_strip_prefix(buf)
	return win32.utf16_to_utf8(buf, context.allocator)
}


basename :: proc(name: string) -> (base: string) {
	name := name
	if len(name) > 3 && name[:3] == `\\?` {
		name = name[3:]
	}

	if len(name) == 2 && name[1] == ':' {
		return "."
	} else if len(name) > 2 && name[1] == ':' {
		name = name[2:]
	}
	i := len(name)-1

	for ; i > 0 && (name[i] == '/' || name[i] == '\\'); i -= 1 {
		name = name[:i]
	}
	for i -= 1; i >= 0; i -= 1 {
		if name[i] == '/' || name[i] == '\\' {
			name = name[i+1:]
			break
		}
	}
	return name
}


file_type_mode :: proc(h: win32.HANDLE) -> File_Mode {
	switch win32.GetFileType(h) {
	case win32.FILE_TYPE_PIPE:
		return File_Mode_Named_Pipe
	case win32.FILE_TYPE_CHAR:
		return File_Mode_Device | File_Mode_Char_Device
	}
	return 0
}



_file_mode_from_file_attributes :: proc(FileAttributes: win32.DWORD, h: win32.HANDLE, ReparseTag: win32.DWORD) -> (mode: File_Mode) {
	if FileAttributes & win32.FILE_ATTRIBUTE_READONLY != 0 {
		mode |= 0o444
	} else {
		mode |= 0o666
	}

	is_sym := false
	if FileAttributes & win32.FILE_ATTRIBUTE_REPARSE_POINT == 0 {
		is_sym = false
	} else {
		is_sym = ReparseTag == win32.IO_REPARSE_TAG_SYMLINK || ReparseTag == win32.IO_REPARSE_TAG_MOUNT_POINT
	}

	if is_sym {
		mode |= File_Mode_Sym_Link
	} else {
		if FileAttributes & win32.FILE_ATTRIBUTE_DIRECTORY != 0 {
			mode |= 0o111 | File_Mode_Dir
		}

		if h != nil {
			mode |= file_type_mode(h)
		}
	}

	return
}


_file_info_from_win32_file_attribute_data :: proc(d: ^win32.WIN32_FILE_ATTRIBUTE_DATA, name: string) -> (fi: File_Info, e: Maybe(Path_Error)) {
	fi.size = i64(d.nFileSizeHigh)<<32 + i64(d.nFileSizeLow)

	fi.mode |= _file_mode_from_file_attributes(d.dwFileAttributes, nil, 0)
	fi.is_dir = fi.mode & File_Mode_Dir != 0

	fi.creation_time     = time.unix(0, win32.FILETIME_as_unix_nanoseconds(d.ftCreationTime))
	fi.modification_time = time.unix(0, win32.FILETIME_as_unix_nanoseconds(d.ftLastWriteTime))
	fi.access_time       = time.unix(0, win32.FILETIME_as_unix_nanoseconds(d.ftLastAccessTime))

	fi.fullpath, e = full_path_from_name(name)
	fi.name = basename(fi.fullpath)

	return
}


_file_info_from_win32_find_data :: proc(d: ^win32.WIN32_FIND_DATAW, name: string) -> (fi: File_Info, e: Maybe(Path_Error)) {
	fi.size = i64(d.nFileSizeHigh)<<32 + i64(d.nFileSizeLow)

	fi.mode |= _file_mode_from_file_attributes(d.dwFileAttributes, nil, 0)
	fi.is_dir = fi.mode & File_Mode_Dir != 0

	fi.creation_time     = time.unix(0, win32.FILETIME_as_unix_nanoseconds(d.ftCreationTime))
	fi.modification_time = time.unix(0, win32.FILETIME_as_unix_nanoseconds(d.ftLastWriteTime))
	fi.access_time       = time.unix(0, win32.FILETIME_as_unix_nanoseconds(d.ftLastAccessTime))

	fi.fullpath, e = full_path_from_name(name)
	fi.name = basename(fi.fullpath)

	return
}


_file_info_from_get_file_information_by_handle :: proc(path: string, h: win32.HANDLE) -> (File_Info, Maybe(Path_Error)) {
	d: win32.BY_HANDLE_FILE_INFORMATION
	if !win32.GetFileInformationByHandle(h, &d) {
		return {}, _stat_errno(win32.GetLastError())

	}

	ti: win32.FILE_ATTRIBUTE_TAG_INFO
	if !win32.GetFileInformationByHandleEx(h, .FileAttributeTagInfo, &ti, size_of(ti)) {
		err := win32.GetLastError()
		if err != win32.ERROR_INVALID_PARAMETER {
			return {}, _stat_errno(err)
		}
		// Indicate this is a symlink on FAT file systems
		ti.ReparseTag = 0
	}

	fi: File_Info

	fi.fullpath = path
	fi.name = basename(path)
	fi.size = i64(d.nFileSizeHigh)<<32 + i64(d.nFileSizeLow)

	fi.mode |= _file_mode_from_file_attributes(ti.FileAttributes, h, ti.ReparseTag)
	fi.is_dir = fi.mode & File_Mode_Dir != 0

	fi.creation_time     = time.unix(0, win32.FILETIME_as_unix_nanoseconds(d.ftCreationTime))
	fi.modification_time = time.unix(0, win32.FILETIME_as_unix_nanoseconds(d.ftLastWriteTime))
	fi.access_time       = time.unix(0, win32.FILETIME_as_unix_nanoseconds(d.ftLastAccessTime))

	return fi, nil
}

_is_abs :: proc(path: string) -> bool {
	if len(path) > 0 && path[0] == '/' {
		return true
	}
	if len(path) > 2 {
		switch path[0] {
		case 'A'..='Z', 'a'..='z':
			return path[1] == ':' && is_path_separator(path[2])
		}
	}
	return false
}

_fix_long_path :: proc(path: string) -> string {
	if len(path) < 248 {
		return path
	}

	if len(path) >= 2 && path[:2] == `\\` {
		return path
	}
	if !_is_abs(path) {
		return path
	}

	prefix :: `\\?`

	path_buf := make([]byte, len(prefix)+len(path)+len(`\`), context.temp_allocator)
	copy(path_buf, prefix)
	n := len(path)
	r, w := 0, len(prefix)
	for r < n {
		switch {
		case is_path_separator(path[r]):
			r += 1
		case path[r] == '.' && (r+1 == n || is_path_separator(path[r+1])):
			r += 1
		case r+1 < n && path[r] == '.' && path[r+1] == '.' && (r+2 == n || is_path_separator(path[r+2])):
			return path
		case:
			path_buf[w] = '\\'
			w += 1
			for ; r < n && !is_path_separator(path[r]); r += 1 {
				path_buf[w] = path[r]
				w += 1
			}
		}
	}

	if w == len(`\\?\c:`) {
		path_buf[w] = '\\'
		w += 1
	}
	return string(path_buf[:w])
}