builder/amazonebs: Read config

builder/amazonebs/builder.go

 package amazonebs
 
 import (
+	"encoding/json"
+	"errors"
 	"github.com/mitchellh/packer/packer"
 )
 
 type config struct {
-	AccessKey string
+	AccessKey string `json:"access_key"`
 	Region    string
-	SecretKey string
-	SourceAmi string
+	SecretKey string `json:"secret_key"`
+	SourceAmi string `json:"source_ami"`
 }
 
 type Builder struct {
 	config config
 }
 
-func (*Builder) Prepare(interface{}) error {
-	return nil
+func (b *Builder) Prepare(raw interface{}) (err error) {
+	_, ok := raw.(map[string]interface{})
+	if !ok {
+		err = errors.New("configuration isn't a valid map")
+		return
+	}
+
+	jsonBytes, err := json.Marshal(raw)
+	if err != nil {
+		return
+	}
+
+	err = json.Unmarshal(jsonBytes, &b.config)
+	if err != nil {
+		return
+	}
+
+	return
 }
 
 func (*Builder) Run(packer.Build, packer.Ui) {}

builder/amazonebs/builder_test.go

@@ -12,3 +12,41 @@ func TestBuilder_ImplementsBuilder(t *testing.T) {
 	var actual packer.Builder
 	assert.Implementor(&Builder{}, &actual, "should be a Builder")
 }
+
+func TestBuilder_Prepare_NotMap(t *testing.T) {
+	assert := asserts.NewTestingAsserts(t, true)
+
+	b := &Builder{}
+	err := b.Prepare(42)
+	assert.NotNil(err, "should have an error")
+	assert.Equal(err.Error(), "configuration isn't a valid map", "config is not a map")
+}
+
+func TestBuilder_Prepare_BadType(t *testing.T) {
+	assert := asserts.NewTestingAsserts(t, true)
+
+	b := &Builder{}
+	c := map[string]interface{} {
+		"access_key": []string{},
+	}
+
+	err := b.Prepare(c)
+	assert.NotNil(err, "should have an error")
+}
+
+func TestBuilder_Prepare_Good(t *testing.T) {
+	assert := asserts.NewTestingAsserts(t, true)
+
+	b := &Builder{}
+	c := map[string]interface{} {
+		"access_key": "foo",
+		"secret_key": "bar",
+		"source_ami": "123456",
+	}
+
+	err := b.Prepare(c)
+	assert.Nil(err, "should not have an error")
+	assert.Equal(b.config.AccessKey, "foo", "should be valid access key")
+	assert.Equal(b.config.SecretKey, "bar", "should be valid secret key")
+	assert.Equal(b.config.SourceAmi, "123456", "should have source AMI")
+}