Parse Windows commands differently than Unix commands

Stinkin' backslashes

middleware/commands.go

@@ -2,6 +2,9 @@ package middleware
 
 import (
 	"errors"
+	"runtime"
+	"strings"
+	"unicode"
 
 	"github.com/flynn/go-shlex"
 )
@@ -9,11 +12,19 @@ import (
 // SplitCommandAndArgs takes a command string and parses it
 // shell-style into the command and its separate arguments.
 func SplitCommandAndArgs(command string) (cmd string, args []string, err error) {
-	parts, err := shlex.Split(command)
-	if err != nil {
-		err = errors.New("error parsing command: " + err.Error())
-		return
-	} else if len(parts) == 0 {
+	var parts []string
+
+	if runtime.GOOS == "windows" {
+		parts = parseWindowsCommand(command) // parse it Windows-style
+	} else {
+		parts, err = shlex.Split(command) // parse it Unix-style
+		if err != nil {
+			err = errors.New("error parsing command: " + err.Error())
+			return
+		}
+	}
+
+	if len(parts) == 0 {
 		err = errors.New("no command contained in '" + command + "'")
 		return
 	}
@@ -25,3 +36,64 @@ func SplitCommandAndArgs(command string) (cmd string, args []string, err error)
 
 	return
 }
+
+// parseWindowsCommand is a sad but good-enough attempt to
+// split a command into the command and its arguments like
+// the Windows command line would; only basic parsing is
+// supported. This function has to be used on Windows instead
+// of the shlex package because this function treats backslash
+// characters properly.
+//
+// Loosely based off the rules here: http://stackoverflow.com/a/4094897/1048862
+// True parsing is much, much trickier.
+func parseWindowsCommand(cmd string) []string {
+	var parts []string
+	var part string
+	var quoted bool
+	var backslashes int
+
+	for _, ch := range cmd {
+		if ch == '\\' {
+			backslashes++
+			continue
+		}
+		var evenBacksl = (backslashes % 2) == 0
+		if backslashes > 0 && ch != '\\' {
+			numBacksl := (backslashes / 2) + 1
+			if ch == '"' {
+				numBacksl--
+			}
+			part += strings.Repeat(`\`, numBacksl)
+			backslashes = 0
+		}
+
+		if quoted {
+			if ch == '"' && evenBacksl {
+				quoted = false
+				continue
+			}
+			part += string(ch)
+			continue
+		}
+
+		if unicode.IsSpace(ch) && len(part) > 0 {
+			parts = append(parts, part)
+			part = ""
+			continue
+		}
+
+		if ch == '"' && evenBacksl {
+			quoted = true
+			continue
+		}
+
+		part += string(ch)
+	}
+
+	if len(part) > 0 {
+		parts = append(parts, part)
+		part = ""
+	}
+
+	return parts
+}