bring back the cmd directory

.gitignore

@@ -1,2 +1,2 @@
-jsonstream
+/jsonstream
 *.log

cmd/jsonstream/jsonstream.go

@@ -0,0 +1,83 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/alexflint/go-arg"
+	"github.com/brettlangdon/jsonstream"
+)
+
+var args struct {
+	File string   `arg:"-f,help:JSON stream file to read from"`
+	TSV  bool     `arg:"-t,help:Reformat the JSON stream to TSV '<value>\t<value>'"`
+	Key  bool     `arg:"-k,help:Whether or not to include the key in --tsv. '<key>=<value>\t<key>=<value>'"`
+	Keys []string `arg:"positional,help:Which keys from the input JSON stream to include in the output"`
+}
+
+func init() {
+	arg.MustParse(&args)
+}
+
+func getReader() (reader *jsonstream.Reader, err error) {
+	var input io.Reader
+	input = os.Stdin
+	if args.File != "" {
+		input, err = os.Open(args.File)
+	}
+
+	if err == nil {
+		reader = jsonstream.NewReader(input, args.Keys)
+	}
+	return reader, err
+}
+
+func getFormatter() (formatter *jsonstream.Formatter, err error) {
+	var format jsonstream.FormatType
+	format = jsonstream.FormatJSON
+
+	if args.TSV {
+		format = jsonstream.FormatTSV
+		if args.Key {
+			format = jsonstream.FormatTSVKey
+		}
+	}
+
+	if err == nil {
+		formatter = jsonstream.NewFormatter(format)
+	}
+	return formatter, err
+}
+
+func main() {
+	var err error
+	var reader *jsonstream.Reader
+	var formatter *jsonstream.Formatter
+
+	reader, err = getReader()
+	if err != nil {
+		panic(err)
+	}
+	formatter, err = getFormatter()
+	if err != nil {
+		panic(err)
+	}
+
+	for {
+		data, err := reader.ReadLine()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			panic(err)
+		}
+
+		var output []byte
+		output, err = formatter.Format(data)
+		if err != nil {
+			panic(err)
+		}
+		fmt.Printf("%s\r\n", output)
+	}
+}