refactor CLI logic and file input support

sparte.go

@@ -90,28 +90,51 @@ func SpartanParsedURL(u url.URL, input string) bool {
 	return true
 }
 
+func Usage() {
+	fmt.Fprintln(os.Stderr, `
+	Usage: sparte [--help] [URL] [-i INPUT] [-f FILE]
+
+		--help     usage
+		-i         send INPUT to URL
+		-f         send contents of FILE as input to UR
+
+	`)
+	return
+}
+
 func main() {
 	args := os.Args[1:]
 	if len(args) == 0 {
-		fmt.Println("do --help for help")
+		Usage()
+		return
 	}
+	url := args[0]
+	input := ""
 	for i, arg := range args {
 		if arg == "--help" {
-			fmt.Println("Usage: <program> [--help] [URL]")
+			Usage()
 			return
 		}
-		if arg == "-i" {
-			if len(args) < i+2 {
-				fmt.Println("argument needed for -i")
+		if arg == "-i" || arg == "-f" {
+			if len(args) < i+2 || (i==0 && len(args) < i+3) {
+				fmt.Println("input arument or URL missing")
 				return
 			}
-			if i == 0 {
-				fmt.Println("try this format instead: <program> URL -i INPUT")
-				return
+			url = args[i-1]
+			if arg == "-i" {
+				input = args[i+1]
+				break
 			}
-			SpartanURL(args[i-1], args[i+1])
-			return
+			// arg must be -f
+			inputBytes, err := ioutil.ReadFile(args[i+1])
+			if err != nil {
+				fmt.Fprintln(os.Stderr, "Error reading file")
+				os.Exit(1)
+			}
+			input = string(inputBytes)
+			break
+			// ignoring other args if any
 		}
 	}
-	SpartanURL(args[0], "")
+	SpartanURL(url, input)
 }