Windows: CLI Improvement

The Ansi parser and their associated actions have been decoupled. Now
parsing results in call backs to an interface which performs the
appropriate actions depending on the environment.

This improvement provides a functional Vi experience and the vttest no
longer panics.

This PR replaces docker/docker #13224 with the latest console updates.

Signed-off-by: John Howard <jhoward@microsoft.com>

term/windows/console.go

@@ -0,0 +1,61 @@
+// +build windows
+
+package windows
+
+import (
+	"io"
+	"os"
+	"syscall"
+
+	. "github.com/Azure/go-ansiterm/winterm"
+)
+
+// ConsoleStreams, for each standard stream referencing a console, returns a wrapped version
+// that handles ANSI character sequences.
+func ConsoleStreams() (stdIn io.ReadCloser, stdOut, stdErr io.Writer) {
+	if IsConsole(os.Stdin.Fd()) {
+		stdIn = newAnsiReader(syscall.STD_INPUT_HANDLE)
+	} else {
+		stdIn = os.Stdin
+	}
+
+	if IsConsole(os.Stdout.Fd()) {
+		stdOut = newAnsiWriter(syscall.STD_OUTPUT_HANDLE)
+	} else {
+		stdOut = os.Stdout
+	}
+
+	if IsConsole(os.Stderr.Fd()) {
+		stdErr = newAnsiWriter(syscall.STD_ERROR_HANDLE)
+	} else {
+		stdErr = os.Stderr
+	}
+
+	return stdIn, stdOut, stdErr
+}
+
+// GetHandleInfo returns file descriptor and bool indicating whether the file is a console.
+func GetHandleInfo(in interface{}) (uintptr, bool) {
+	switch t := in.(type) {
+	case *ansiReader:
+		return t.Fd(), true
+	case *ansiWriter:
+		return t.Fd(), true
+	}
+
+	var inFd uintptr
+	var isTerminal bool
+
+	if file, ok := in.(*os.File); ok {
+		inFd = file.Fd()
+		isTerminal = IsConsole(inFd)
+	}
+	return inFd, isTerminal
+}
+
+// IsConsole returns true if the given file descriptor is a Windows Console.
+// The code assumes that GetConsoleMode will return an error for file descriptors that are not a console.
+func IsConsole(fd uintptr) bool {
+	_, e := GetConsoleMode(fd)
+	return e == nil
+}