//go:build windows

package safeio

import (
	"errors"
	"io"
	"os"
	"path/filepath"

	"golang.org/x/sys/windows"
)

type windowsPrivateRegular struct {
	parents *windowsParentHandles
	handle  windows.Handle
	path    string
	info    windows.ByHandleFileInformation
}

func (value *windowsPrivateRegular) Close() {
	if value.handle != 0 {
		_ = windows.CloseHandle(value.handle)
		value.handle = 0
	}
	if value.parents != nil {
		value.parents.Close()
		value.parents = nil
	}
}

func openWindowsPrivateRegular(path string, links uint32) (*windowsPrivateRegular, error) {
	parents, target, err := openCanonicalWindowsParent(path)
	if err != nil || parents == nil || len(parents.handles) == 0 || validateOwnerOnlyDACL(parents.handles[len(parents.handles)-1]) != nil {
		if parents != nil {
			parents.Close()
		}
		return nil, ErrUnsafeFile
	}
	value, err := openWindowsPrivateRegularAt(parents.handles[len(parents.handles)-1], target, windows.GENERIC_READ, links)
	if err != nil {
		parents.Close()
		return nil, err
	}
	handle := value.handle
	value.handle = 0
	return &windowsPrivateRegular{
		parents: parents,
		handle:  handle,
		path:    filepath.Join(parents.directory, target),
		info:    value.info,
	}, nil
}

func claimCanonicalPrivateRegular(source, claim string) (bool, error) {
	sourceFile, err := openWindowsPrivateRegular(source, 1)
	if err != nil {
		if windowsPrivateClaimPairExists(source, claim) {
			return false, nil
		}
		if isWindowsNotFound(err) && windowsPrivateClaimAbsentOrOrphan(claim) {
			return false, nil
		}
		return false, ErrUnsafeFile
	}
	defer sourceFile.Close()
	if err := windows.CreateHardLink(windows.StringToUTF16Ptr(claim), windows.StringToUTF16Ptr(sourceFile.path), 0); err != nil {
		if errors.Is(err, windows.ERROR_FILE_EXISTS) || errors.Is(err, windows.ERROR_ALREADY_EXISTS) {
			if existing, existingErr := openWindowsPrivateRegularWithAllowedLinks(claim, 1, 2); existingErr == nil {
				existing.Close()
				return false, nil
			}
		}
		return false, ErrUnsafeFile
	}
	if err := windows.GetFileInformationByHandle(sourceFile.handle, &sourceFile.info); err != nil || sourceFile.info.NumberOfLinks != 2 {
		return false, ErrUnsafeFile
	}
	claimFile, err := openWindowsPrivateRegular(claim, 2)
	if err != nil {
		return false, ErrUnsafeFile
	}
	defer claimFile.Close()
	if !sameWindowsPrivateFile(sourceFile.info, claimFile.info) {
		return false, ErrUnsafeFile
	}
	return true, nil
}

func readCanonicalPrivateClaim(source, claim string, maximum int64) ([]byte, bool, error) {
	sourceFile, err := openWindowsPrivateRegular(source, 2)
	if err != nil {
		if isWindowsNotFound(err) && windowsPrivateClaimAbsentOrOrphan(claim) {
			return nil, false, nil
		}
		return nil, false, ErrUnsafeFile
	}
	defer sourceFile.Close()
	claimFile, err := openWindowsPrivateRegular(claim, 2)
	if err != nil {
		if isWindowsNotFound(err) {
			return nil, false, nil
		}
		return nil, false, ErrUnsafeFile
	}
	defer claimFile.Close()
	if !sameWindowsPrivateFile(sourceFile.info, claimFile.info) {
		return nil, false, ErrUnsafeFile
	}
	file := os.NewFile(uintptr(sourceFile.handle), "tht-safeio-oidc-claim")
	if file == nil {
		return nil, false, ErrUnsafeFile
	}
	contents, readErr := io.ReadAll(io.LimitReader(file, maximum+1))
	file.Close()
	sourceFile.handle = 0
	if readErr != nil || int64(len(contents)) > maximum {
		return nil, false, ErrUnsafeFile
	}
	if err := windows.GetFileInformationByHandle(claimFile.handle, &claimFile.info); err != nil || claimFile.info.NumberOfLinks != 2 || !sameWindowsPrivateFile(sourceFile.info, claimFile.info) {
		return nil, false, ErrUnsafeFile
	}
	return contents, true, nil
}

func removeCanonicalPrivateClaim(source, claim string) (bool, error) {
	sourceFile, err := openWindowsPrivateRegular(source, 2)
	if err != nil {
		if isWindowsNotFound(err) && windowsPrivateClaimAbsentOrOrphan(claim) {
			return false, nil
		}
		return false, ErrUnsafeFile
	}
	claimFile, err := openWindowsPrivateRegular(claim, 2)
	if err != nil {
		sourceFile.Close()
		if isWindowsNotFound(err) {
			return false, nil
		}
		return false, ErrUnsafeFile
	}
	if !sameWindowsPrivateFile(sourceFile.info, claimFile.info) {
		sourceFile.Close()
		claimFile.Close()
		return false, ErrUnsafeFile
	}
	sourceFile.Close()
	claimFile.Close()
	if err := windows.DeleteFile(windows.StringToUTF16Ptr(source)); err != nil {
		return false, ErrUnsafeFile
	}
	remaining, err := openWindowsPrivateRegular(claim, 1)
	if err != nil {
		return false, ErrUnsafeFile
	}
	remaining.Close()
	if err := windows.DeleteFile(windows.StringToUTF16Ptr(claim)); err != nil {
		return false, ErrUnsafeFile
	}
	return true, nil
}

func openWindowsPrivateRegularWithAllowedLinks(path string, allowed ...uint32) (*windowsPrivateRegular, error) {
	for _, links := range allowed {
		value, err := openWindowsPrivateRegular(path, links)
		if err == nil {
			return value, nil
		}
	}
	return nil, ErrUnsafeFile
}

func windowsPrivateClaimAbsentOrOrphan(claim string) bool {
	claimFile, err := openWindowsPrivateRegular(claim, 1)
	if err != nil {
		return isWindowsNotFound(err)
	}
	claimFile.Close()
	return true
}

func windowsPrivateClaimPairExists(source, claim string) bool {
	sourceFile, sourceErr := openWindowsPrivateRegular(source, 2)
	if sourceErr != nil {
		return false
	}
	defer sourceFile.Close()
	claimFile, claimErr := openWindowsPrivateRegular(claim, 2)
	if claimErr != nil {
		return false
	}
	defer claimFile.Close()
	return sameWindowsPrivateFile(sourceFile.info, claimFile.info)
}

func isWindowsNotFound(err error) bool {
	return errors.Is(err, windows.ERROR_FILE_NOT_FOUND) || errors.Is(err, windows.ERROR_PATH_NOT_FOUND)
}

func sameWindowsPrivateFile(left, right windows.ByHandleFileInformation) bool {
	return left.VolumeSerialNumber == right.VolumeSerialNumber && left.FileIndexHigh == right.FileIndexHigh && left.FileIndexLow == right.FileIndexLow && left.FileSizeHigh == right.FileSizeHigh && left.FileSizeLow == right.FileSizeLow && left.LastWriteTime == right.LastWriteTime
}