package cache

import (
	"errors"
	"fmt"

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

// cachingIndex wraps access to v1.ImageIndex with a [Cache]. Implements v1.ImageIndex
type cachingIndex struct {
	wrappedIndex
	cache *LazyCache
}

// wrappedIndex lets us call index.wrappedIndex to delegate to the embedded
// field's method without colliding with the interface func ImageIndex
type wrappedIndex v1.ImageIndex

// ImageIndex returns a new v1.ImageIndex backed by a cachingIndex. OCI interface methods will
// read from the cache c, falling back to wrapped inner implementation if missing. Typically, the
// inner Index will be a github.com/google/go-containerregistry/pkg/v1/remote/remoteIndex
func ImageIndex(ii v1.ImageIndex, c *LazyCache) v1.ImageIndex {
	return &cachingIndex{
		wrappedIndex: ii,
		cache:        c,
	}
}

// Image returns a v1.Image that this ImageIndex references.
func (c *cachingIndex) Image(h v1.Hash) (v1.Image, error) {
	if cached, err := c.cache.getImage(h); err == nil {
		return cached, nil
	} else if !errors.Is(err, ErrNotFound) {
		return nil, err
	}
	img, err := c.wrappedIndex.Image(h)
	if err != nil {
		return nil, fmt.Errorf("failed to get uncached Image: %v", err)
	}
	return c.cache.putImage(img)
}

// ImageIndex returns a v1.ImageIndex that this ImageIndex references.
func (c *cachingIndex) ImageIndex(h v1.Hash) (v1.ImageIndex, error) {
	if cached, err := c.cache.getIndex(h); err == nil {
		return cached, nil
	} else if !errors.Is(err, ErrNotFound) {
		return nil, err
	}
	ii, err := c.wrappedIndex.ImageIndex(h)
	if err != nil {
		return nil, fmt.Errorf("failed to get uncached ImageIndex: %v", err)
	}

	return c.cache.putIndex(ii)
}