package disk

import (
	"fmt"
	"os"
	"path"
	"path/filepath"
	"sync"

	"github.com/google/go-containerregistry/pkg/name"

	"edge-infra.dev/pkg/f8n/warehouse/oci"
	"edge-infra.dev/pkg/f8n/warehouse/oci/layout"
)

// Cache is a thread-safe wrapper around an OCI Image Layout with functionality
// for purging.
type Cache struct {
	sync.RWMutex
	path *layout.Path
}

// New returns a new instance of the disk Cache.
func New(layoutPath *layout.Path) *Cache {
	return &Cache{path: layoutPath}
}

// FromPath returns a new instance of the disk Cache from an existing path.
func FromPath(path string) (*Cache, error) {
	layoutPath, err := layout.New(path)
	if err != nil {
		return nil, err
	}
	return &Cache{path: layoutPath}, nil
}

// Get fetches an oci artifact from an oci layout path.
func (d *Cache) Get(ref name.Reference) (oci.Artifact, error) {
	d.RLock()
	defer d.RUnlock()
	a, err := d.path.Get(ref)
	if err != nil {
		return nil, err
	}
	return a, nil
}

// Exists check if an oci artifact exists in the oci layout path.
func (d *Cache) Exists(ref name.Reference) bool {
	// TODO(aw18576): not needed because we will lock in Get?
	// d.RLock()
	// defer d.RUnlock()
	_, err := d.path.Get(ref)
	return err == nil
}

// Add appends an oci artifact to a layout path.
func (d *Cache) Add(ref name.Reference, a oci.Artifact) error {
	d.Lock()
	defer d.Unlock()
	return d.path.Append(ref, a)
}

// Purge deletes an oci layout path from disk.
func (d *Cache) Purge() error {
	layoutPath := string(d.path.Path)
	contents, err := filepath.Glob(path.Join(layoutPath, "/*"))
	if err != nil {
		return err
	}
	for _, item := range contents {
		err = os.RemoveAll(item)
		if err != nil {
			return err
		}
	}
	np, err := layout.New(layoutPath)
	if err != nil {
		return fmt.Errorf("failed to re-instantiate empty layout: %w", err)
	}
	d.path = np
	return nil
}