package storage

import (
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
)

// Open validates the digest and returns a ReadCloser for the blob.
// Returns ErrBlobNotFound if the blob does not exist on disk.
func (s *Store) Open(digest string) (io.ReadCloser, error) {
	if err := validateDigest(digest); err != nil {
		return nil, err
	}

	f, err := os.Open(s.blobPath(digest))
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return nil, ErrBlobNotFound
		}
		return nil, fmt.Errorf("storage: open blob: %w", err)
	}
	return f, nil
}

// Stat returns the size of the blob in bytes.
// Returns ErrBlobNotFound if the blob does not exist on disk.
func (s *Store) Stat(digest string) (int64, error) {
	if err := validateDigest(digest); err != nil {
		return 0, err
	}

	info, err := os.Stat(s.blobPath(digest))
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return 0, ErrBlobNotFound
		}
		return 0, fmt.Errorf("storage: stat blob: %w", err)
	}
	return info.Size(), nil
}

// Delete removes the blob file and attempts to clean up its prefix
// directory. Non-empty or already-removed prefix directories are
// silently ignored.
func (s *Store) Delete(digest string) error {
	if err := validateDigest(digest); err != nil {
		return err
	}

	path := s.blobPath(digest)
	if err := os.Remove(path); err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return ErrBlobNotFound
		}
		return fmt.Errorf("storage: delete blob: %w", err)
	}

	// Best-effort cleanup of the prefix directory.
	_ = os.Remove(filepath.Dir(path))

	return nil
}

// Exists reports whether the blob exists on disk.
func (s *Store) Exists(digest string) bool {
	if err := validateDigest(digest); err != nil {
		return false
	}

	_, err := os.Stat(s.blobPath(digest))
	return err == nil
}