experiment with encoder/decoder for data encapsulation

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

internal/formats/formats.go

@@ -15,7 +15,7 @@ import (
 // TODO: eventually this is the source of truth for all formatters
 func All() []format.Format {
 	return []format.Format{
-		syftjson.Format(),
+		syftjson.Format( /*...now there is a requirement for app config here...*/ ),
 		table.Format(),
 		cyclonedx12xml.Format(),
 		spdx22json.Format(),

internal/formats/syftjson/decoder.go

@@ -10,7 +10,10 @@ import (
 	"github.com/anchore/syft/internal/formats/syftjson/model"
 )
 
-func decoder(reader io.Reader) (*sbom.SBOM, error) {
+type decoder struct {
+}
+
+func (d decoder) Decode(reader io.Reader) (*sbom.SBOM, error) {
 	dec := json.NewDecoder(reader)
 
 	var doc model.Document

internal/formats/syftjson/encoder.go

@@ -7,8 +7,12 @@ import (
 	"github.com/anchore/syft/syft/sbom"
 )
 
-func encoder(output io.Writer, s sbom.SBOM, appConfig interface{}) error {
-	doc := ToFormatModel(s, appConfig)
+type encoder struct {
+	appConfig interface{}
+}
+
+func (e encoder) Encode(output io.Writer, s sbom.SBOM) error {
+	doc := ToFormatModel(s, e.appConfig)
 
 	enc := json.NewEncoder(output)
 	// prevent > and < from being escaped in the payload

internal/formats/syftjson/format.go

@@ -2,11 +2,25 @@ package syftjson
 
 import "github.com/anchore/syft/syft/format"
 
-func Format() format.Format {
+func Format(appConfig interface{}) format.Format {
 	return format.NewFormat(
 		format.JSONOption,
-		encoder,
-		decoder,
-		validator,
+		Encoder(appConfig),
+		Decoder(),
+		Validator(),
 	)
 }
+
+func Encoder(appConfig interface{}) format.Encoder {
+	return &encoder{
+		appConfig: appConfig,
+	}
+}
+
+func Decoder() format.Decoder {
+	return &decoder{}
+}
+
+func Validator() format.Validator {
+	return &validator{}
+}

internal/formats/syftjson/validator.go

@@ -9,7 +9,10 @@ import (
 	"github.com/anchore/syft/internal/formats/syftjson/model"
 )
 
-func validator(reader io.Reader) error {
+type validator struct {
+}
+
+func (v validator) Validate(reader io.Reader) error {
 	type Document struct {
 		Schema model.Schema `json:"schema"`
 	}