package storage_test

import (
	"context"
	"errors"
	"os"
	"path/filepath"
	"strings"
	"testing"

	"sneak.berlin/go/vaultik/internal/storage"
)

// errStreamInterrupted stands in for an upload cut off mid-stream.
var errStreamInterrupted = errors.New("connection reset mid-upload")

// failingReader yields its data once, then fails.
type failingReader struct {
	data []byte
	done bool
}

func (r *failingReader) Read(p []byte) (int, error) {
	if r.done {
		return 0, errStreamInterrupted
	}

	n := copy(p, r.data)
	r.done = true

	return n, nil
}

// TestFileStorer_InterruptedWriteLeavesNoTrustedObject checks that a write
// cut off mid-stream leaves nothing at the destination key, so a later run
// cannot Stat a truncated object and trust it as a complete blob.
func TestFileStorer_InterruptedWriteLeavesNoTrustedObject(t *testing.T) {
	t.Parallel()

	f, err := storage.NewFileStorer(t.TempDir())
	if err != nil {
		t.Fatalf("NewFileStorer: %v", err)
	}

	ctx := context.Background()
	key := "blobs/aa/bb/aabbccddeeff"

	err = f.PutWithProgress(ctx, key, &failingReader{data: []byte("partial")}, 4096, nil)
	if err == nil {
		t.Fatal("expected the interrupted write to fail, got nil")
	}

	_, err = f.Stat(ctx, key)
	if !errors.Is(err, storage.ErrNotFound) {
		t.Fatalf("expected key absent after interrupted write, got Stat err %v", err)
	}

	keys, err := f.List(ctx, "blobs/")
	if err != nil {
		t.Fatalf("List: %v", err)
	}

	if len(keys) != 0 {
		t.Fatalf("expected no keys listed after interrupted write, got %v", keys)
	}
}

// TestFileStorer_ListSkipsPartialFiles checks that a leftover temp file (the
// storage layer names them with a ".partial" suffix) is never surfaced as a
// key by List or ListStream.
func TestFileStorer_ListSkipsPartialFiles(t *testing.T) {
	t.Parallel()

	base := t.TempDir()

	f, err := storage.NewFileStorer(base)
	if err != nil {
		t.Fatalf("NewFileStorer: %v", err)
	}

	ctx := context.Background()
	realKey := "blobs/aa/bb/aabbccddeeff"

	err = f.Put(ctx, realKey, strings.NewReader("blob-bytes"))
	if err != nil {
		t.Fatalf("Put: %v", err)
	}

	// A stray temp file, as an interrupted write would leave behind.
	leftover := filepath.Join(base, "blobs/aa/bb/aabbccddeeff-123456.partial")

	err = os.WriteFile(leftover, []byte("half"), 0o600)
	if err != nil {
		t.Fatalf("writing leftover temp file: %v", err)
	}

	keys, err := f.List(ctx, "blobs/")
	if err != nil {
		t.Fatalf("List: %v", err)
	}

	if len(keys) != 1 || keys[0] != realKey {
		t.Fatalf("List should return only the real key, got %v", keys)
	}

	var streamed []string

	for obj := range f.ListStream(ctx, "blobs/") {
		if obj.Err != nil {
			t.Fatalf("ListStream: %v", obj.Err)
		}

		streamed = append(streamed, obj.Key)
	}

	if len(streamed) != 1 || streamed[0] != realKey {
		t.Fatalf("ListStream should return only the real key, got %v", streamed)
	}
}