package ociimg

import (
	"context"
	"fmt"

	"github.com/google/go-containerregistry/pkg/name"
	v1 "github.com/google/go-containerregistry/pkg/v1"
	"github.com/google/go-containerregistry/pkg/v1/remote"
	"github.com/google/go-containerregistry/pkg/v1/types"
)

func imageFromIndex(index v1.ImageIndex, platform *v1.Platform) (v1.Image, v1.Descriptor, error) {
	im, err := index.IndexManifest()
	if err != nil {
		return nil, v1.Descriptor{}, err
	}

	for i := range im.Manifests {
		manifest := im.Manifests[i]
		if manifest.MediaType != types.OCIManifestSchema1 && im.MediaType != types.DockerManifestSchema2 {
			return nil, v1.Descriptor{}, fmt.Errorf("%q has unexpected mediaType %q in base for %q", manifest.Digest, manifest.MediaType, platform)
		}
		if manifest.Platform.Satisfies(*platform) {
			img, err := index.Image(manifest.Digest)
			return img, manifest, err
		}
	}

	return nil, v1.Descriptor{}, fmt.Errorf("index does not contain image satisfying the requested platoform %q", platform)
}

func fetch(ctx context.Context, ref name.Reference) (imageOrIndex, error) {
	ropt := []remote.Option{
		remote.WithUserAgent(userAgent),
		remote.WithContext(ctx),
	}

	desc, err := remote.Get(ref, ropt...)
	if err != nil {
		return nil, err
	}
	if desc.MediaType.IsIndex() {
		return desc.ImageIndex()
	}
	return desc.Image()
}