package storage_test

import (
	"context"
	"errors"
	"io/fs"
	"os"
	"path/filepath"
	"reflect"
	"strings"
	"testing"

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

// newFileStorer builds a file:// backend rooted at a fresh temp directory.
//
//nolint:ireturn // conformance runs against the Storer interface by design
func newFileStorer(t *testing.T) storage.Storer {
	t.Helper()

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

	return s
}

// TestFileStorer runs the shared Storer contract against the file:// backend.
func TestFileStorer(t *testing.T) {
	t.Parallel()
	runStorerConformance(t, newFileStorer)
}

// TestFileStorerListMissingDestination checks that List and ListStream
// fail when the destination directory does not exist, instead of
// reporting an empty store.
func TestFileStorerListMissingDestination(t *testing.T) {
	t.Parallel()

	ctx := context.Background()

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

	keys, err := s.List(ctx, "metadata/")
	if !errors.Is(err, fs.ErrNotExist) {
		t.Errorf("List = %v, %v; want a not-exist error", keys, err)
	}

	var streamErr error

	for object := range s.ListStream(ctx, "metadata/") {
		if object.Err != nil {
			streamErr = object.Err
		}
	}

	if !errors.Is(streamErr, fs.ErrNotExist) {
		t.Errorf("ListStream error = %v, want a not-exist error", streamErr)
	}
}

// The two directories at the top of a destination, either of which the
// tests below replace with a symlink.
const (
	metadataDir = "metadata"
	blobsDir    = "blobs"
)

// moveBehindSymlink moves base/dir to a directory elsewhere and puts a
// symlink to it in its place.
func moveBehindSymlink(t *testing.T, base, dir string) {
	t.Helper()

	linkPath := filepath.Join(base, dir)
	movedPath := filepath.Join(t.TempDir(), dir)

	err := os.Rename(linkPath, movedPath)
	if err != nil {
		t.Fatalf("moving %s away: %v", dir, err)
	}

	err = os.Symlink(movedPath, linkPath)
	if err != nil {
		t.Fatalf("linking %s: %v", dir, err)
	}
}

// TestFileStorerListsThroughSymlinkedDirectory checks that List and
// ListStream read through a symlinked metadata/ or blobs/ directory, as Get
// and Stat do, instead of listing the link as one key. Listing the whole
// destination meets the link part-way through the walk; listing its prefix
// starts the walk at the link. A prefix missing behind the link lists as
// empty.
func TestFileStorerListsThroughSymlinkedDirectory(t *testing.T) {
	t.Parallel()

	for _, dir := range []string{metadataDir, blobsDir} {
		t.Run(dir, func(t *testing.T) {
			t.Parallel()

			base := t.TempDir()
			key := dir + "/aa/bb/object"

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

			err = s.Put(context.Background(), key, strings.NewReader("data"))
			if err != nil {
				t.Fatalf("Put: %v", err)
			}

			moveBehindSymlink(t, base, dir)

			want := []string{key}

			for _, prefix := range []string{"", dir + "/"} {
				got := listSorted(t, s, prefix)
				if !reflect.DeepEqual(got, want) {
					t.Errorf("List(%q) = %v, want %v", prefix, got, want)
				}

				got = listStreamKeys(t, s, prefix)
				if !reflect.DeepEqual(got, want) {
					t.Errorf("ListStream(%q) = %v, want %v", prefix, got, want)
				}
			}

			absent := dir + "/absent/"

			if got := listSorted(t, s, absent); len(got) != 0 {
				t.Errorf("List(%q) = %v, want empty", absent, got)
			}

			if got := listStreamKeys(t, s, absent); len(got) != 0 {
				t.Errorf("ListStream(%q) = %v, want empty", absent, got)
			}
		})
	}
}

// TestFileStorerListFailsOnSymlinkWithMissingTarget checks that List and
// ListStream fail on a symlinked metadata/ or blobs/ directory whose target
// is missing, such as a link to a volume that is not mounted, as they do on
// a missing destination directory, instead of listing it as empty. That
// holds for a prefix below the link too.
func TestFileStorerListFailsOnSymlinkWithMissingTarget(t *testing.T) {
	t.Parallel()

	ctx := context.Background()

	for _, dir := range []string{metadataDir, blobsDir} {
		t.Run(dir, func(t *testing.T) {
			t.Parallel()

			base := t.TempDir()

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

			unmounted := filepath.Join(t.TempDir(), "unmounted")

			err = os.Symlink(unmounted, filepath.Join(base, dir))
			if err != nil {
				t.Fatalf("Symlink: %v", err)
			}

			for _, prefix := range []string{"", dir + "/", dir + "/aa/"} {
				keys, err := s.List(ctx, prefix)
				if !errors.Is(err, fs.ErrNotExist) {
					t.Errorf("List(%q) = %v, %v; want a not-exist error",
						prefix, keys, err)
				}

				var streamErr error

				for object := range s.ListStream(ctx, prefix) {
					if object.Err != nil {
						streamErr = object.Err
					}
				}

				if !errors.Is(streamErr, fs.ErrNotExist) {
					t.Errorf("ListStream(%q) error = %v, want a not-exist error",
						prefix, streamErr)
				}
			}
		})
	}
}

// TestFileStorerListFailsOnSymlinkLoop checks that a symlink pointing back
// at the destination makes List and ListStream fail instead of walking it
// forever.
func TestFileStorerListFailsOnSymlinkLoop(t *testing.T) {
	t.Parallel()

	ctx := context.Background()
	base := t.TempDir()

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

	err = s.Put(ctx, testBlobKey, strings.NewReader("data"))
	if err != nil {
		t.Fatalf("Put: %v", err)
	}

	err = os.Symlink(base, filepath.Join(base, "blobs", "loop"))
	if err != nil {
		t.Fatalf("Symlink: %v", err)
	}

	keys, err := s.List(ctx, "blobs/")
	if err == nil {
		t.Errorf("List = %d keys and no error, want an error", len(keys))
	}

	var streamErr error

	for object := range s.ListStream(ctx, "blobs/") {
		if object.Err != nil {
			streamErr = object.Err
		}
	}

	if streamErr == nil {
		t.Error("ListStream sent no error, want one")
	}
}

// TestFileStorerDeletePartialUploadsThroughSymlinkedDirectory checks that
// DeletePartialUploads, which remote nuke uses, removes a leftover temp
// file behind a symlinked metadata/ or blobs/ directory and keeps the
// object at the real key.
func TestFileStorerDeletePartialUploadsThroughSymlinkedDirectory(t *testing.T) {
	t.Parallel()

	ctx := context.Background()

	for _, dir := range []string{metadataDir, blobsDir} {
		t.Run(dir, func(t *testing.T) {
			t.Parallel()

			base := t.TempDir()
			key := dir + "/aa/bb/object"

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

			err = s.Put(ctx, key, strings.NewReader("data"))
			if err != nil {
				t.Fatalf("Put: %v", err)
			}

			leftover := filepath.Join(base, key+"-123456.partial")

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

			moveBehindSymlink(t, base, dir)

			err = s.DeletePartialUploads(ctx, dir+"/")
			if err != nil {
				t.Fatalf("DeletePartialUploads: %v", err)
			}

			// leftover runs through the link.
			_, err = os.Stat(leftover)
			if !os.IsNotExist(err) {
				t.Errorf("leftover temp file was not removed: %v", err)
			}

			_, err = s.Stat(ctx, key)
			if err != nil {
				t.Errorf("Stat of the real key: %v", err)
			}
		})
	}
}

// TestFileStorerPutMissingDestination checks that a write fails when the
// destination directory has gone, even after earlier writes to it
// succeeded, and that it does not create the directory again.
func TestFileStorerPutMissingDestination(t *testing.T) {
	t.Parallel()

	ctx := context.Background()
	base := filepath.Join(t.TempDir(), "usbstick")

	err := os.Mkdir(base, 0o750)
	if err != nil {
		t.Fatalf("Mkdir: %v", err)
	}

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

	err = s.Put(ctx, "blobs/aa/bb/first", strings.NewReader("first"))
	if err != nil {
		t.Fatalf("first Put: %v", err)
	}

	err = os.Rename(base, base+"-unplugged")
	if err != nil {
		t.Fatalf("Rename: %v", err)
	}

	err = s.Put(ctx, "blobs/aa/bb/second", strings.NewReader("second"))
	if !errors.Is(err, fs.ErrNotExist) {
		t.Errorf("Put = %v, want a not-exist error", err)
	}

	_, err = os.Stat(base)
	if !errors.Is(err, fs.ErrNotExist) {
		t.Errorf("Put created the destination directory again (Stat = %v)", err)
	}
}