Improved command line parsing, started on json-based parsing instructions

cmd/sutron/main.go

@@ -1,45 +1,83 @@
 package main
 
 import (
-	"git.binarythought.com/cdramey/sutron"
-	"fmt"
 	"bytes"
+	"flag"
+	"fmt"
+	"encoding/json"
+	"git.binarythought.com/cdramey/sutron"
 	"io/ioutil"
 	"os"
 )
 
+type ParserConfig struct {
+	ParserType string `json:"parser_type"`
+}
+
 func main() {
-	if len(os.Args) < 2 {
-		fmt.Fprintf(os.Stderr,
-			"required argument missing\n")
+	flags := flag.NewFlagSet("sutron", flag.ExitOnError)
+	flags.SetOutput(os.Stdout)
+	flags.Usage = func() {
+		fmt.Fprintf(flags.Output(),
+			"Usage: %s [OPTION] <files> ...\nOptions:\n",
+			os.Args[0])
+		flags.PrintDefaults()
+	}
+
+	jsonfn := flags.String("json", "sutron.json",
+		"json parser definition file name")
+
+	flags.Parse(os.Args[1:])
+
+	if flags.NArg() < 1 {
+		fmt.Fprintf(os.Stderr, "files parameter cannot be empty\n")
 		os.Exit(1)
 	}
 
-	var raw []byte
-	var err error
-	if os.Args[1] == "-" {
-		raw, err = ioutil.ReadAll(os.Stdin)
-	} else {
-		raw, err = ioutil.ReadFile(os.Args[1])
-	}
+	jsonsrc, err := ioutil.ReadFile(*jsonfn)
 	if err != nil {
 		fmt.Fprintf(os.Stderr,
 			"error reading \"%s\": %s\n",
 			os.Args[1], err.Error())
 	}
 
-	i := bytes.Index(raw, []byte("B"))
-	if i != -1 {
-		sutrondata, err := sutron.ParseSutronB(raw[i:])
+	var pcfg ParserConfig
+	err = json.Unmarshal(jsonsrc, &pcfg)
+	if err != nil {
+		fmt.Fprintf(os.Stderr,
+			"parser config error: %s\n", err.Error())
+		os.Exit(1)
+	}
+
+	fmt.Printf("Parser type: %s\n", pcfg.ParserType)
+
+	for _, fn := range flags.Args() {
+		var raw []byte
+		var err error
+		if fn == "-" {
+			raw, err = ioutil.ReadAll(os.Stdin)
+		} else {
+			raw, err = ioutil.ReadFile(fn)
+		}
 		if err != nil {
 			fmt.Fprintf(os.Stderr,
-				"%s\n", err.Error())
-			os.Exit(1)
+				"error reading \"%s\": %s\n",
+				os.Args[1], err.Error())
 		}
 
-		fmt.Printf("Sutron Block: %s\n", string(sutrondata.Block))
-		fmt.Printf("Sutron Group: %s\n", string(sutrondata.Group))
-		fmt.Printf("Sutron Delta: %s\n", string(sutrondata.Delta))
-		fmt.Printf("Sutron Voltage: %s\n", string(sutrondata.Voltage))
+		i := bytes.Index(raw, []byte("B"))
+		if i != -1 {
+			sutrondata, err := sutron.ParseSutronB(raw[i:])
+			if err != nil {
+				fmt.Fprintf(os.Stderr,
+					"%s\n", err.Error())
+				os.Exit(1)
+			}
+
+			fmt.Printf("Sutron Block: %s\n", string(sutrondata.Block))
+			fmt.Printf("Sutron Group: %s\n", string(sutrondata.Group))
+			fmt.Printf("Sutron Delta: %s\n", string(sutrondata.Delta))
+			fmt.Printf("Sutron Voltage: %s\n", string(sutrondata.Voltage))
+		}
 	}
 }

sutron.go

@@ -5,10 +5,10 @@ import (
 )
 
 type SutronB struct {
-	Block byte
-	Group byte
-	Delta byte
-	Data []byte
+	Block   byte
+	Group   byte
+	Delta   byte
+	Data    []byte
 	Voltage byte
 }
 
@@ -40,7 +40,7 @@ func ParseSutronB(raw []byte) (*SutronB, error) {
 	data.Block = raw[0]
 	data.Group = raw[1]
 	data.Delta = raw[2]
-	data.Data = raw[3:raw_len - 1]
-	data.Voltage = raw[raw_len - 1]
+	data.Data = raw[3 : raw_len-1]
+	data.Voltage = raw[raw_len-1]
 	return &data, nil
 }