distro: introduce Arch and ImageType interfaces

Objects implementing these interfaces will represent the
architecture support for a given distro and the image type
support for a given architecture distro combination, respectively.

The idea is to always resolve to these objects early, and drop
the equilavent methods from the distro interface. This means that
we convert our input strings to real objects once, and then never
have to verify their correctness again.

Signed-off-by: Tom Gundersen <teg@jklm.no>

internal/distro/test/distro.go

@@ -4,15 +4,68 @@ import (
 	"errors"
 
 	"github.com/osbuild/osbuild-composer/internal/blueprint"
+	"github.com/osbuild/osbuild-composer/internal/distro"
 	"github.com/osbuild/osbuild-composer/internal/osbuild"
 	"github.com/osbuild/osbuild-composer/internal/rpmmd"
 )
 
 type TestDistro struct{}
+type TestArch struct{}
+type TestImageType struct{}
 
 const Name = "test-distro"
 const ModulePlatformID = "platform:test"
 
+func (d *TestDistro) GetArch(arch string) (distro.Arch, error) {
+	if arch != "test_arch" {
+		return nil, errors.New("invalid arch: " + arch)
+	}
+	return &TestArch{}, nil
+}
+
+func (a *TestArch) Name() string {
+	return Name
+}
+
+func (a *TestArch) ListImageTypes() []string {
+	return []string{"test-format"}
+}
+
+func (a *TestArch) GetImageType(imageType string) (distro.ImageType, error) {
+	if imageType != "test_output" {
+		return nil, errors.New("invalid image type: " + imageType)
+	}
+	return &TestImageType{}, nil
+}
+
+func (t *TestImageType) Name() string {
+	return "test-format"
+}
+
+func (t *TestImageType) Filename() string {
+	return "test.img"
+}
+
+func (t *TestImageType) MIMEType() string {
+	return "application/x-test"
+}
+
+func (t *TestImageType) Size(size uint64) uint64 {
+	return 0
+}
+
+func (t *TestImageType) BasePackages() ([]string, []string) {
+	return nil, nil
+}
+
+func (t *TestImageType) BuildPackages() []string {
+	return nil
+}
+
+func (t *TestImageType) Manifest(b *blueprint.Customizations, repos []rpmmd.RepoConfig, packageSpecs, buildPackageSpecs []rpmmd.PackageSpec, size uint64) (*osbuild.Manifest, error) {
+	return &osbuild.Manifest{}, nil
+}
+
 func New() *TestDistro {
 	return &TestDistro{}
 }