// Package filesys implements helpers for converting various filesystems to
// Kustomize / kyaml filesystems.
package filesys

import (
	"embed"
	"fmt"
	"io/fs"
	"path/filepath"

	"sigs.k8s.io/kustomize/kyaml/filesys"
)

// ConvertEmbeddedFSToKustomizeFS performs a walk from the root of the provided
// embed.FS and copies the file tree into an in-memory Kustomize FileSystem,
// allowing the use of Kustomize APIs (build, etc) against embedded manifests.
func ConvertEmbeddedFSToKustomizeFS(efs embed.FS) (filesys.FileSystem, error) {
	return ConvertEmbeddedFSToKustomizeFSDir(efs, "")
}

func ConvertEmbeddedFSToKustomizeFSDir(efs embed.FS, dir string) (filesys.FileSystem, error) {
	fsys := filesys.MakeFsInMemory()
	return ConvertEmbeddedFSToKustomizeFSExisting(efs, fsys, dir)
}

func ConvertEmbeddedFSToKustomizeFSExisting(efs embed.FS, fsys filesys.FileSystem, dir string) (filesys.FileSystem, error) {
	err := fs.WalkDir(efs, ".", func(path string, d fs.DirEntry, walkErr error) error {
		// this shouldn't happe because we are traversing an embedded file system
		// from the root, but per io/fs we should handle this error explicitly
		if walkErr != nil {
			return fmt.Errorf("encountered a walk error: %w", walkErr)
		}

		if d.IsDir() {
			return fsys.Mkdir(filepath.Join(dir, path))
		}

		return writeEmbeddedFileToKustomizeFS(efs, fsys, path, dir)
	})
	if err != nil {
		return nil, fmt.Errorf("failed to convert embedded file system to in-memory kustomize file system: %w", err)
	}

	return fsys, nil
}

func writeEmbeddedFileToKustomizeFS(efs embed.FS, kfs filesys.FileSystem, path, dir string) error {
	data, err := efs.ReadFile(path)
	if err != nil {
		return fmt.Errorf("failed to read path %s from embedded file system: %w", path, err)
	}

	if err := kfs.WriteFile(filepath.Join(dir, path), data); err != nil {
		return fmt.Errorf("failed to write path %s to in-memory kustomize file system: %w", path, err)
	}
	return nil
}