package app

import (
	"context"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"time"
)

type mediaUploadObject struct {
	Key, ContentType string
	Size             int64
	Body             io.Reader
}

type localMediaStorage struct{ directory string }

func (s localMediaStorage) Bucket() string { return "" }
func (s localMediaStorage) Put(_ context.Context, key, _ string, _ int64, body io.Reader) error {
	if err := os.MkdirAll(s.directory, 0o755); err != nil {
		return err
	}
	target := filepath.Join(s.directory, filepath.Base(key))
	file, err := os.OpenFile(target, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o644)
	if err != nil {
		return err
	} // Never remove an existing file on collision.
	_, copyErr := io.Copy(file, body)
	closeErr := file.Close()
	if copyErr != nil || closeErr != nil {
		_ = os.Remove(target)
		if copyErr != nil {
			return copyErr
		}
		return closeErr
	}
	return nil
}
func (s localMediaStorage) Delete(_ context.Context, key string) error {
	return os.Remove(filepath.Join(s.directory, filepath.Base(key)))
}

// Return a cleanup function for both a partially failed upload and a failed DB
// finalization. Cleanup gets its own deadline even if the HTTP client cancels.
func putMediaObjects(ctx context.Context, storage mediaObjectStorage, objects []mediaUploadObject) (func(), error) {
	var uploaded []string
	cleanup := func() {
		cleanupCtx, cancel := context.WithTimeout(context.WithoutCancel(ctx), 15*time.Second)
		defer cancel()
		for i := len(uploaded) - 1; i >= 0; i-- {
			_ = storage.Delete(cleanupCtx, uploaded[i])
		}
	}
	for _, object := range objects {
		if err := storage.Put(ctx, object.Key, object.ContentType, object.Size, object.Body); err != nil {
			cleanup()
			return func() {}, fmt.Errorf("store media object: %w", err)
		}
		uploaded = append(uploaded, object.Key)
	}
	return cleanup, nil
}