1 files changed, 120 insertions, 0 deletions
diff --git a/middleware/commands.go b/middleware/commands.go
new file mode 100644
index 000000000..5c241161e
--- /dev/null
+++ b/middleware/commands.go
@@ -0,0 +1,120 @@
+package middleware
+
+import (
+	"errors"
+	"runtime"
+	"unicode"
+
+	"github.com/flynn/go-shlex"
+)
+
+var runtimeGoos = runtime.GOOS
+
+// 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) {
+	var parts []string
+
+	if runtimeGoos == "windows" {
+		parts = parseWindowsCommand(command) // parse it Windows-style
+	} else {
+		parts, err = parseUnixCommand(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
+	}
+
+	cmd = parts[0]
+	if len(parts) > 1 {
+		args = parts[1:]
+	}
+
+	return
+}
+
+// parseUnixCommand parses a unix style command line and returns the
+// command and its arguments or an error
+func parseUnixCommand(cmd string) ([]string, error) {
+	return shlex.Split(cmd)
+}
+
+// parseWindowsCommand parses windows command lines and
+// returns the command and the arguments as an array. It
+// should be able to parse commonly used command lines.
+// Only basic syntax is supported:
+//  - spaces in double quotes are not token delimiters
+//  - double quotes are escaped by either backspace or another double quote
+//  - except for the above case backspaces are path separators (not special)
+//
+// Many sources point out that escaping quotes using backslash can be unsafe.
+// Use two double quotes when possible. (Source: http://stackoverflow.com/a/31413730/2616179 )
+//
+// This function has to be used on Windows instead
+// of the shlex package because this function treats backslash
+// characters properly.
+func parseWindowsCommand(cmd string) []string {
+	const backslash = '\\'
+	const quote = '"'
+
+	var parts []string
+	var part string
+	var inQuotes bool
+	var lastRune rune
+
+	for i, ch := range cmd {
+
+		if i != 0 {
+			lastRune = rune(cmd[i-1])
+		}
+
+		if ch == backslash {
+			// put it in the part - for now we don't know if it's an
+			// escaping char or path separator
+			part += string(ch)
+			continue
+		}
+
+		if ch == quote {
+			if lastRune == backslash {
+				// remove the backslash from the part and add the escaped quote instead
+				part = part[:len(part)-1]
+				part += string(ch)
+				continue
+			}
+
+			if lastRune == quote {
+				// revert the last change of the inQuotes state
+				// it was an escaping quote
+				inQuotes = !inQuotes
+				part += string(ch)
+				continue
+			}
+
+			// normal escaping quotes
+			inQuotes = !inQuotes
+			continue
+
+		}
+
+		if unicode.IsSpace(ch) && !inQuotes && len(part) > 0 {
+			parts = append(parts, part)
+			part = ""
+			continue
+		}
+
+		part += string(ch)
+	}
+
+	if len(part) > 0 {
+		parts = append(parts, part)
+		part = ""
+	}
+
+	return parts
+}