Do not duplicate Content-Type and Accept headers if provided

Fixes: #4

args/parse.go

@@ -27,13 +27,34 @@ func (opts Opts) Has(opt string) bool {
 	return opts.index(opt) != -1
 }
 
+// Val return the value of the first occurance of opt.
 func (opts Opts) Val(opt string) string {
 	if idx := opts.index(opt); idx != -1 && idx+1 < len(opts) {
 		return opts[idx+1]
 	}
 	return ""
 }
 
+// Vals return the values of all occurances of opt.
+func (opts Opts) Vals(opt string) []string {
+	var vals []string
+	off := 1
+	if len(opt) > 1 {
+		off = 2
+	}
+	for i, o := range opts {
+		if len(o) >= 2 && o[0] == '-' {
+			if o[off:] == opt {
+				if i+1 < len(opts) {
+					i++
+					vals = append(vals, opts[i])
+				}
+			}
+		}
+	}
+	return vals
+}
+
 // Remove removes all occurrences of opt and return true if found.
 func (opts *Opts) Remove(opt string) bool {
 	found := false

main.go

@@ -84,10 +84,14 @@ func main() {
 			hasInput = false
 		}
 		if hasInput {
-			opts = append(opts, "-H", "Content-Type: application/json")
+			if !headerSupplied(opts, "Content-Type") {
+				opts = append(opts, "-H", "Content-Type: application/json")
+			}
 		}
 	}
-	opts = append(opts, "-H", "Accept: application/json, */*")
+	if !headerSupplied(opts, "Accept") {
+		opts = append(opts, "-H", "Accept: application/json, */*")
+	}
 	if opts.Has("curl") {
 		opts.Remove("curl")
 		fmt.Print("curl")
@@ -128,3 +132,13 @@ func main() {
 	}
 	os.Exit(status)
 }
+
+func headerSupplied(opts args.Opts, header string) bool {
+	header = strings.ToLower(header)
+	for _, h := range append(opts.Vals("H"), opts.Vals("header")...) {
+		if strings.HasPrefix(strings.ToLower(h), header+":") {
+			return true
+		}
+	}
+	return false
+}