Adding support for JSON files as a data source for the template

Signed-off-by: Dave Henderson <dhenderson@gmail.com>

context.go

@@ -1,12 +1,46 @@
 package main
 
 import (
+	"encoding/json"
+	"io/ioutil"
+	"log"
 	"os"
+	"path/filepath"
 	"strings"
 )
 
 // Context for templates
 type Context struct {
+	Data map[string]interface{}
+}
+
+func parseFiles(context *Context, files []string) {
+	for _, file := range files {
+		ext := filepath.Ext(file)
+		if ext != ".json" {
+			log.Fatalf("Only JSON data files are supported right now (%v)", file)
+		}
+		name := strings.Split(filepath.Base(file), ext)[0]
+		log.Printf("Parsing %q", name)
+		f, err := ioutil.ReadFile(file)
+		if err != nil {
+			log.Fatalf("Error while reading %q: %v", file, err)
+		}
+		context.Data[name] = parseJSON(f)
+	}
+}
+
+func parseJSON(bytes []byte) interface{} {
+	var obj interface{}
+	json.Unmarshal(bytes, &obj)
+	return obj
+}
+
+// NewContext - constructor
+func NewContext(files []string) *Context {
+	context := &Context{make(map[string]interface{})}
+	parseFiles(context, files)
+	return context
 }
 
 // Env - Map environment variables for use in a template

main.go

@@ -14,8 +14,29 @@ import (
 	"text/template"
 )
 
+// version
+const Version = "0.1.0"
+
+type dataFiles []string
+
+var (
+	context       *Context
+	dataFilesFlag dataFiles
+	verFlag       *bool
+)
+
+func (d *dataFiles) String() string {
+	return fmt.Sprint(*d)
+}
+
+func (d *dataFiles) Set(value string) error {
+	*d = append(*d, value)
+	return nil
+}
+
 func init() {
 	ver := flag.Bool("v", false, "Print version and exit")
+	flag.Var(&dataFilesFlag, "d", "Data file to resolve. Repeat to add more to the context.")
 	flag.Parse()
 	if *ver {
 		fmt.Println(version.Version)
@@ -34,7 +55,6 @@ type Gomplate struct {
 
 // RunTemplate -
 func (g *Gomplate) RunTemplate(in io.Reader, out io.Writer) {
-	context := &Context{}
 	text, err := ioutil.ReadAll(in)
 	if err != nil {
 		log.Fatalf("Read failed!\n%v\n", err)
@@ -76,6 +96,15 @@ func NewGomplate() *Gomplate {
 }
 
 func main() {
+	flag.Parse()
+
+	if *verFlag {
+		fmt.Println(Version)
+		os.Exit(0)
+	}
+
+	context = NewContext(dataFilesFlag)
+
 	g := NewGomplate()
 	g.RunTemplate(os.Stdin, os.Stdout)
 }