// +build windows

package client

import (
	"fmt"
	"io"
	"os"
	"syscall"
	"time"
	"unsafe"

	"github.com/sirupsen/logrus"
)

var (
	modkernel32   = syscall.NewLazyDLL("kernel32.dll")
	procCopyFileW = modkernel32.NewProc("CopyFileW")
)

// writeFileFromReader writes an output file from an io.Reader
func writeFileFromReader(path string, reader io.Reader, timeoutSeconds int, context string) (int64, error) {
	outFile, err := os.Create(path)
	if err != nil {
		return 0, fmt.Errorf("opengcs: writeFileFromReader: failed to create %s: %s", path, err)
	}
	defer outFile.Close()
	return copyWithTimeout(outFile, reader, 0, timeoutSeconds, context)
}

// copyWithTimeout is a wrapper for io.Copy using a timeout duration
func copyWithTimeout(dst io.Writer, src io.Reader, size int64, timeoutSeconds int, context string) (int64, error) {
	logrus.Debugf("opengcs: copywithtimeout: size %d: timeout %d: (%s)", size, timeoutSeconds, context)

	type resultType struct {
		err   error
		bytes int64
	}

	done := make(chan resultType, 1)
	go func() {
		result := resultType{}
		result.bytes, result.err = io.Copy(dst, src)
		done <- result
	}()

	var result resultType
	timedout := time.After(time.Duration(timeoutSeconds) * time.Second)

	select {
	case <-timedout:
		return 0, fmt.Errorf("opengcs: copyWithTimeout: timed out (%s)", context)
	case result = <-done:
		if result.err != nil && result.err != io.EOF {
			// See https://github.com/golang/go/blob/f3f29d1dea525f48995c1693c609f5e67c046893/src/os/exec/exec_windows.go for a clue as to why we are doing this :)
			if se, ok := result.err.(syscall.Errno); ok {
				const (
					errNoData     = syscall.Errno(232)
					errBrokenPipe = syscall.Errno(109)
				)
				if se == errNoData || se == errBrokenPipe {
					logrus.Debugf("opengcs: copyWithTimeout: hit NoData or BrokenPipe: %d: %s", se, context)
					return result.bytes, nil
				}
			}
			return 0, fmt.Errorf("opengcs: copyWithTimeout: error reading: '%s' after %d bytes (%s)", result.err, result.bytes, context)
		}
	}
	logrus.Debugf("opengcs: copyWithTimeout: success - copied %d bytes (%s)", result.bytes, context)
	return result.bytes, nil
}

// CopyFile is a utility for copying a file - used for the sandbox cache.
// Uses CopyFileW win32 API for performance
func CopyFile(srcFile, destFile string, overwrite bool) error {
	var bFailIfExists uint32 = 1
	if overwrite {
		bFailIfExists = 0
	}

	lpExistingFileName, err := syscall.UTF16PtrFromString(srcFile)
	if err != nil {
		return err
	}
	lpNewFileName, err := syscall.UTF16PtrFromString(destFile)
	if err != nil {
		return err
	}
	r1, _, err := syscall.Syscall(
		procCopyFileW.Addr(),
		3,
		uintptr(unsafe.Pointer(lpExistingFileName)),
		uintptr(unsafe.Pointer(lpNewFileName)),
		uintptr(bFailIfExists))
	if r1 == 0 {
		return fmt.Errorf("failed CopyFileW Win32 call from '%s' to '%s': %s", srcFile, destFile, err)
	}
	return nil
}