package storage

import (
	"bytes"
	"context"
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"testing"
	"time"
)

var testEncryptionKey = []byte("0123456789abcdef0123456789abcdef")

func mustTestAEAD(t *testing.T) cipher.AEAD {
	t.Helper()
	block, err := aes.NewCipher(testEncryptionKey)
	if err != nil {
		t.Fatalf("aes.NewCipher() error = %v", err)
	}
	aead, err := cipher.NewGCM(block)
	if err != nil {
		t.Fatalf("cipher.NewGCM() error = %v", err)
	}
	return aead
}

func TestCreateStoresGzipAndOpenIsTransparent(t *testing.T) {
	t.Parallel()

	store, err := NewFilesystemStore(filepath.Join(t.TempDir(), "data"), testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}

	original := bytes.Repeat([]byte("hello scratch "), 1024)
	meta, err := store.Create(context.Background(), bytes.NewReader(original), "text/plain; charset=utf-8", time.Hour)
	if err != nil {
		t.Fatalf("Create() error = %v", err)
	}
	if meta.Size != int64(len(original)) {
		t.Fatalf("meta.Size = %d, want %d", meta.Size, len(original))
	}

	onDisk, err := os.ReadFile(meta.FilePath)
	if err != nil {
		t.Fatalf("ReadFile() error = %v", err)
	}
	if len(onDisk) < 4 || string(onDisk[:4]) != "SBX1" {
		t.Fatalf("stored file does not have encrypted scratch header")
	}

	reader, _, err := store.Open(meta.ID)
	if err != nil {
		t.Fatalf("Open() error = %v", err)
	}
	defer reader.Close()
	got, err := io.ReadAll(reader)
	if err != nil {
		t.Fatalf("ReadAll() error = %v", err)
	}
	if !bytes.Equal(got, original) {
		t.Fatalf("open content mismatch: got %d bytes, want %d", len(got), len(original))
	}
}

func TestCreateEncryptedStoreDoesNotExposeGzipHeaderOnDisk(t *testing.T) {
	t.Parallel()

	key := make([]byte, 32)
	if _, err := rand.Read(key); err != nil {
		t.Fatalf("rand.Read() error = %v", err)
	}

	dataDir := filepath.Join(t.TempDir(), "data")
	store, err := NewFilesystemStore(dataDir, key)
	if err != nil {
		t.Fatalf("NewEncryptedFilesystemStore() error = %v", err)
	}

	original := bytes.Repeat([]byte("secret payload "), 1024)
	meta, err := store.Create(context.Background(), bytes.NewReader(original), "text/plain", time.Hour)
	if err != nil {
		t.Fatalf("Create() error = %v", err)
	}

	onDisk, err := os.ReadFile(meta.FilePath)
	if err != nil {
		t.Fatalf("ReadFile() error = %v", err)
	}
	if len(onDisk) < 2 {
		t.Fatalf("encrypted file too short")
	}
	if onDisk[0] == 0x1f && onDisk[1] == 0x8b {
		t.Fatalf("encrypted file unexpectedly starts with gzip header")
	}

	reader, _, err := store.Open(meta.ID)
	if err != nil {
		t.Fatalf("Open() error = %v", err)
	}
	defer reader.Close()
	got, err := io.ReadAll(reader)
	if err != nil {
		t.Fatalf("ReadAll() error = %v", err)
	}
	if !bytes.Equal(got, original) {
		t.Fatalf("Open() content mismatch: got %d bytes, want %d", len(got), len(original))
	}

	filePayload, err := os.ReadFile(meta.FilePath)
	if err != nil {
		t.Fatalf("ReadFile(encrypted) error = %v", err)
	}
	sum := sha256.Sum256(filePayload)
	wantBlobID := hex.EncodeToString(sum[:])
	if meta.BlobID != wantBlobID {
		t.Fatalf("meta.BlobID = %q, want SHA-256 of encrypted blob %q", meta.BlobID, wantBlobID)
	}
	if meta.ID == wantBlobID {
		t.Fatalf("meta.ID should be a short public id, got blob hash id %q", meta.ID)
	}
}

func TestEncryptedStoreFailsToOpenWithWrongKey(t *testing.T) {
	t.Parallel()

	keyA := make([]byte, 32)
	if _, err := rand.Read(keyA); err != nil {
		t.Fatalf("rand.Read(keyA) error = %v", err)
	}
	keyB := make([]byte, 32)
	if _, err := rand.Read(keyB); err != nil {
		t.Fatalf("rand.Read(keyB) error = %v", err)
	}

	dataDir := filepath.Join(t.TempDir(), "data")
	storeA, err := NewFilesystemStore(dataDir, keyA)
	if err != nil {
		t.Fatalf("NewEncryptedFilesystemStore(keyA) error = %v", err)
	}
	_, err = storeA.Create(context.Background(), bytes.NewReader([]byte("hello")), "text/plain", time.Hour)
	if err != nil {
		t.Fatalf("Create() error = %v", err)
	}

	if _, err := NewFilesystemStore(dataDir, keyB); err == nil {
		t.Fatalf("NewFilesystemStore() with wrong key error = nil, want non-nil")
	}
}

func TestCreateWithOriginalNameNormalizesFilename(t *testing.T) {
	t.Parallel()

	store, err := NewFilesystemStore(filepath.Join(t.TempDir(), "data"), testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}

	meta, err := store.CreateWithOriginalName(context.Background(), bytes.NewReader([]byte("hello")), "text/plain", "  ../../demo.txt  ", time.Hour)
	if err != nil {
		t.Fatalf("CreateWithOriginalName() error = %v", err)
	}
	if meta.OriginalName != "demo.txt" {
		t.Fatalf("meta.OriginalName = %q, want %q", meta.OriginalName, "demo.txt")
	}

	reloaded, err := NewFilesystemStore(store.dataDir, testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() reload error = %v", err)
	}
	got, err := reloaded.Get(meta.ID)
	if err != nil {
		t.Fatalf("Get() error = %v", err)
	}
	if got.OriginalName != "demo.txt" {
		t.Fatalf("persisted OriginalName = %q, want %q", got.OriginalName, "demo.txt")
	}
}

func TestCreateWithOriginalNameSameContentGetsDifferentIDs(t *testing.T) {
	t.Parallel()

	store, err := NewFilesystemStore(filepath.Join(t.TempDir(), "data"), testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}

	first, err := store.CreateWithOriginalName(context.Background(), bytes.NewReader([]byte("same body")), "text/plain", "one.txt", time.Hour)
	if err != nil {
		t.Fatalf("first CreateWithOriginalName() error = %v", err)
	}
	second, err := store.CreateWithOriginalName(context.Background(), bytes.NewReader([]byte("same body")), "text/plain", "two.txt", time.Hour)
	if err != nil {
		t.Fatalf("second CreateWithOriginalName() error = %v", err)
	}
	if first.ID == second.ID {
		t.Fatalf("IDs should differ because encrypted blobs include random nonce")
	}
}

func TestGetDeleteAndNotFound(t *testing.T) {
	t.Parallel()

	store, err := NewFilesystemStore(filepath.Join(t.TempDir(), "data"), testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}
	meta, err := store.Create(context.Background(), bytes.NewReader([]byte("hello")), "text/plain", time.Hour)
	if err != nil {
		t.Fatalf("Create() error = %v", err)
	}
	if _, err := store.Get(meta.ID); err != nil {
		t.Fatalf("Get() error = %v", err)
	}
	if err := store.Delete(meta.ID); err != nil {
		t.Fatalf("Delete() error = %v", err)
	}
	if _, err := store.Get(meta.ID); !errors.Is(err, ErrNotFound) {
		t.Fatalf("Get() error = %v, want ErrNotFound", err)
	}
	if err := store.Delete(meta.ID); !errors.Is(err, ErrNotFound) {
		t.Fatalf("Delete() error = %v, want ErrNotFound", err)
	}
}

func TestDeleteExpired(t *testing.T) {
	t.Parallel()

	store, err := NewFilesystemStore(filepath.Join(t.TempDir(), "data"), testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}
	expired, err := store.Create(context.Background(), bytes.NewReader([]byte("expired")), "text/plain", -time.Second)
	if err != nil {
		t.Fatalf("Create expired() error = %v", err)
	}
	active, err := store.Create(context.Background(), bytes.NewReader([]byte("active")), "text/plain", time.Hour)
	if err != nil {
		t.Fatalf("Create active() error = %v", err)
	}
	deleted, err := store.DeleteExpired(time.Now().UTC())
	if err != nil {
		t.Fatalf("DeleteExpired() error = %v", err)
	}
	if deleted != 1 {
		t.Fatalf("DeleteExpired() = %d, want 1", deleted)
	}
	if _, err := store.Get(expired.ID); !errors.Is(err, ErrNotFound) {
		t.Fatalf("expired Get() error = %v, want ErrNotFound", err)
	}
	if _, err := store.Get(active.ID); err != nil {
		t.Fatalf("active Get() error = %v", err)
	}
}

func TestOpenInvalidGzipFails(t *testing.T) {
	t.Parallel()

	store, err := NewFilesystemStore(filepath.Join(t.TempDir(), "data"), testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}
	id := "deadbeefdeadbeefdeadbeef"
	badPath := filepath.Join(store.filesDir, id)
	if err := os.WriteFile(badPath, []byte("not-gzip"), 0o644); err != nil {
		t.Fatalf("WriteFile() error = %v", err)
	}
	store.metadata[id] = Metadata{
		ID:          id,
		FilePath:    badPath,
		CreatedAt:   time.Now().UTC(),
		ExpiresAt:   time.Now().UTC().Add(time.Hour),
		ContentType: "text/plain",
		Size:        int64(len("not-gzip")),
	}
	if err := store.persistLocked(); err != nil {
		t.Fatalf("persistLocked() error = %v", err)
	}
	if _, _, err := store.Open(id); err == nil {
		t.Fatalf("Open() error = nil, want gzip reader error")
	}
}

func TestNewFilesystemStoreInvalidIndex(t *testing.T) {
	t.Parallel()

	root := t.TempDir()
	scratches := filepath.Join(root, filesDirName)
	if err := os.MkdirAll(scratches, 0o755); err != nil {
		t.Fatalf("MkdirAll() error = %v", err)
	}
	if err := os.WriteFile(filepath.Join(root, indexFilename), []byte("{bad"), 0o644); err != nil {
		t.Fatalf("WriteFile() error = %v", err)
	}
	if _, err := NewFilesystemStore(root, testEncryptionKey); err == nil {
		t.Fatalf("NewFilesystemStore() error = nil, want invalid index error")
	}
}

func TestNewFilesystemStoreReconcileOnStartup(t *testing.T) {
	t.Parallel()

	root := t.TempDir()
	scratches := filepath.Join(root, filesDirName)
	if err := os.MkdirAll(scratches, 0o755); err != nil {
		t.Fatalf("MkdirAll() error = %v", err)
	}
	keepID := "aaaaaaaaaaaaaaaaaaaaaaaa"
	missingID := "bbbbbbbbbbbbbbbbbbbbbbbb"
	expiredID := "cccccccccccccccccccccccc"
	keepPath := filepath.Join(scratches, keepID)
	expiredPath := filepath.Join(scratches, expiredID)
	if err := os.WriteFile(keepPath, []byte{0x1f, 0x8b, 0x08, 0x00}, 0o644); err != nil {
		t.Fatalf("WriteFile keep error = %v", err)
	}
	if err := os.WriteFile(expiredPath, []byte{0x1f, 0x8b, 0x08, 0x00}, 0o644); err != nil {
		t.Fatalf("WriteFile expired error = %v", err)
	}

	meta := map[string]Metadata{
		keepID: {
			ID:          keepID,
			FilePath:    keepPath,
			CreatedAt:   time.Now().UTC(),
			ExpiresAt:   time.Now().UTC().Add(time.Hour),
			ContentType: "text/plain",
			Size:        1,
		},
		missingID: {
			ID:          missingID,
			FilePath:    filepath.Join(scratches, missingID),
			CreatedAt:   time.Now().UTC(),
			ExpiresAt:   time.Now().UTC().Add(time.Hour),
			ContentType: "text/plain",
			Size:        1,
		},
		expiredID: {
			ID:          expiredID,
			FilePath:    expiredPath,
			CreatedAt:   time.Now().UTC(),
			ExpiresAt:   time.Now().UTC().Add(-time.Minute),
			ContentType: "text/plain",
			Size:        1,
		},
	}
	payload, err := json.Marshal(indexDocument{
		Scratches: meta,
	})
	if err != nil {
		t.Fatalf("json.Marshal() error = %v", err)
	}
	encryptedPayload, err := encryptIndexPayload(payload, mustTestAEAD(t))
	if err != nil {
		t.Fatalf("encryptIndexPayload() error = %v", err)
	}
	if err := os.WriteFile(filepath.Join(root, indexFilename), encryptedPayload, 0o644); err != nil {
		t.Fatalf("WriteFile index error = %v", err)
	}

	store, err := NewFilesystemStore(root, testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}
	if _, err := store.Get(keepID); err != nil {
		t.Fatalf("keep entry missing: %v", err)
	}
	if _, err := store.Get(missingID); !errors.Is(err, ErrNotFound) {
		t.Fatalf("missing entry error = %v, want ErrNotFound", err)
	}
	if _, err := store.Get(expiredID); !errors.Is(err, ErrNotFound) {
		t.Fatalf("expired entry error = %v, want ErrNotFound", err)
	}
}

func TestNewFilesystemStoreWithDefaultTTLShiftsExpiriesOnTTLChange(t *testing.T) {
	t.Parallel()

	dataDir := filepath.Join(t.TempDir(), "data")
	store, err := NewFilesystemStoreWithDefaultTTL(dataDir, time.Hour, testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStoreWithDefaultTTL() error = %v", err)
	}

	meta, err := store.Create(context.Background(), bytes.NewReader([]byte("hello")), "text/plain", time.Hour)
	if err != nil {
		t.Fatalf("Create() error = %v", err)
	}
	originalExpiry := meta.ExpiresAt

	reloaded, err := NewFilesystemStoreWithDefaultTTL(dataDir, 2*time.Hour, testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStoreWithDefaultTTL() reload error = %v", err)
	}
	got, err := reloaded.Get(meta.ID)
	if err != nil {
		t.Fatalf("Get() error = %v", err)
	}

	wantExpiry := originalExpiry.Add(time.Hour)
	if !got.ExpiresAt.Equal(wantExpiry) {
		t.Fatalf("ExpiresAt = %s, want %s", got.ExpiresAt, wantExpiry)
	}

	again, err := NewFilesystemStoreWithDefaultTTL(dataDir, 2*time.Hour, testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStoreWithDefaultTTL() second reload error = %v", err)
	}
	gotAgain, err := again.Get(meta.ID)
	if err != nil {
		t.Fatalf("Get() second reload error = %v", err)
	}
	if !gotAgain.ExpiresAt.Equal(wantExpiry) {
		t.Fatalf("ExpiresAt after unchanged TTL = %s, want %s", gotAgain.ExpiresAt, wantExpiry)
	}

	indexRaw, err := os.ReadFile(filepath.Join(dataDir, indexFilename))
	if err != nil {
		t.Fatalf("ReadFile(index) error = %v", err)
	}
	if bytes.Contains(indexRaw, []byte(`"default_ttl"`)) {
		t.Fatalf("index should not be plaintext JSON")
	}
	indexPlaintext, err := decryptIndexPayload(indexRaw, mustTestAEAD(t))
	if err != nil {
		t.Fatalf("decryptIndexPayload() error = %v", err)
	}
	if !bytes.Contains(indexPlaintext, []byte(`"default_ttl": "2h0m0s"`)) {
		t.Fatalf("decrypted index missing default ttl marker: %s", string(indexPlaintext))
	}
}

type errCloser struct{}

func (errCloser) Close() error { return errors.New("close failed") }

func TestCombinedReadCloserClosePropagatesFirstError(t *testing.T) {
	t.Parallel()

	c := &combinedReadCloser{
		reader:  bytes.NewReader([]byte("ok")),
		closers: []io.Closer{errCloser{}, errCloser{}},
	}
	if err := c.Close(); err == nil {
		t.Fatalf("Close() error = nil, want non-nil")
	}
}

type failingReader struct{}

func (failingReader) Read(_ []byte) (int, error) { return 0, errors.New("boom") }

func TestCreateRollbackOnPersistFailure(t *testing.T) {
	t.Parallel()

	store, err := NewFilesystemStore(filepath.Join(t.TempDir(), "data"), testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}

	badIndexDir := filepath.Join(t.TempDir(), "index-dir")
	if err := os.MkdirAll(badIndexDir, 0o755); err != nil {
		t.Fatalf("MkdirAll() error = %v", err)
	}
	store.index = badIndexDir

	if _, err := store.Create(context.Background(), bytes.NewReader([]byte("x")), "text/plain", time.Hour); err == nil {
		t.Fatalf("Create() error = nil, want persist failure")
	}
	if len(store.metadata) != 0 {
		t.Fatalf("metadata should be rolled back on persist failure")
	}
}

func TestCreateReaderFailure(t *testing.T) {
	t.Parallel()

	store, err := NewFilesystemStore(filepath.Join(t.TempDir(), "data"), testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}
	if _, err := store.Create(context.Background(), failingReader{}, "text/plain", time.Hour); err == nil {
		t.Fatalf("Create() error = nil, want reader failure")
	}
}

func TestDeletePersistFailureRestoresEntry(t *testing.T) {
	t.Parallel()

	store, err := NewFilesystemStore(filepath.Join(t.TempDir(), "data"), testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}
	meta, err := store.Create(context.Background(), bytes.NewReader([]byte("hello")), "text/plain", time.Hour)
	if err != nil {
		t.Fatalf("Create() error = %v", err)
	}

	badIndexDir := filepath.Join(t.TempDir(), "index-dir")
	if err := os.MkdirAll(badIndexDir, 0o755); err != nil {
		t.Fatalf("MkdirAll() error = %v", err)
	}
	store.index = badIndexDir

	if err := store.Delete(meta.ID); err == nil {
		t.Fatalf("Delete() error = nil, want persist failure")
	}
	if _, err := store.Get(meta.ID); err != nil {
		t.Fatalf("entry should be restored after delete persist failure: %v", err)
	}
}

func TestDeleteRemoveFailure(t *testing.T) {
	t.Parallel()

	store, err := NewFilesystemStore(filepath.Join(t.TempDir(), "data"), testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}

	nonEmptyDir := filepath.Join(t.TempDir(), "non-empty")
	if err := os.MkdirAll(nonEmptyDir, 0o755); err != nil {
		t.Fatalf("MkdirAll() error = %v", err)
	}
	if err := os.WriteFile(filepath.Join(nonEmptyDir, "child"), []byte("x"), 0o644); err != nil {
		t.Fatalf("WriteFile() error = %v", err)
	}
	id := "dddddddddddddddddddddddd"
	store.metadata[id] = Metadata{
		ID:          id,
		FilePath:    nonEmptyDir,
		CreatedAt:   time.Now().UTC(),
		ExpiresAt:   time.Now().UTC().Add(time.Hour),
		ContentType: "text/plain",
		Size:        1,
	}
	if err := store.persistLocked(); err != nil {
		t.Fatalf("persistLocked() error = %v", err)
	}
	if err := store.Delete(id); err == nil {
		t.Fatalf("Delete() error = nil, want remove failure")
	}
}

func TestDeleteExpiredPersistFailureRestoresEntries(t *testing.T) {
	t.Parallel()

	store, err := NewFilesystemStore(filepath.Join(t.TempDir(), "data"), testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}
	meta, err := store.Create(context.Background(), bytes.NewReader([]byte("expired")), "text/plain", -time.Second)
	if err != nil {
		t.Fatalf("Create() error = %v", err)
	}

	badIndexDir := filepath.Join(t.TempDir(), "index-dir")
	if err := os.MkdirAll(badIndexDir, 0o755); err != nil {
		t.Fatalf("MkdirAll() error = %v", err)
	}
	store.index = badIndexDir

	if _, err := store.DeleteExpired(time.Now().UTC()); err == nil {
		t.Fatalf("DeleteExpired() error = nil, want persist failure")
	}
	if _, err := store.Get(meta.ID); err != nil {
		t.Fatalf("entry should be restored after DeleteExpired persist failure: %v", err)
	}
}

func TestDeleteExpiredRemoveFailure(t *testing.T) {
	t.Parallel()

	store, err := NewFilesystemStore(filepath.Join(t.TempDir(), "data"), testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}
	nonEmptyDir := filepath.Join(t.TempDir(), "expired-non-empty")
	if err := os.MkdirAll(nonEmptyDir, 0o755); err != nil {
		t.Fatalf("MkdirAll() error = %v", err)
	}
	if err := os.WriteFile(filepath.Join(nonEmptyDir, "child"), []byte("x"), 0o644); err != nil {
		t.Fatalf("WriteFile() error = %v", err)
	}
	id := "eeeeeeeeeeeeeeeeeeeeeeee"
	store.metadata[id] = Metadata{
		ID:          id,
		FilePath:    nonEmptyDir,
		CreatedAt:   time.Now().UTC(),
		ExpiresAt:   time.Now().UTC().Add(-time.Second),
		ContentType: "text/plain",
		Size:        1,
	}
	if err := store.persistLocked(); err != nil {
		t.Fatalf("persistLocked() error = %v", err)
	}
	if _, err := store.DeleteExpired(time.Now().UTC()); err == nil {
		t.Fatalf("DeleteExpired() error = nil, want remove failure")
	}
}

func TestNewFilesystemStoreFailsWhenDataDirIsFile(t *testing.T) {
	t.Parallel()

	tmp := t.TempDir()
	filePath := filepath.Join(tmp, "not-dir")
	if err := os.WriteFile(filePath, []byte("x"), 0o644); err != nil {
		t.Fatalf("WriteFile() error = %v", err)
	}
	if _, err := NewFilesystemStore(filePath, testEncryptionKey); err == nil {
		t.Fatalf("NewFilesystemStore() error = nil, want mkdir failure")
	}
}

func TestNewFilesystemStoreRequires32ByteKey(t *testing.T) {
	t.Parallel()

	dataDir := filepath.Join(t.TempDir(), "data")
	if _, err := NewFilesystemStore(dataDir, nil); err == nil {
		t.Fatalf("NewFilesystemStore() with nil key error = nil, want non-nil")
	}
	if _, err := NewFilesystemStore(dataDir, []byte("short")); err == nil {
		t.Fatalf("NewFilesystemStore() with short key error = nil, want non-nil")
	}
}

func TestNewFilesystemStoreFailsToLoadEncryptedIndexWithWrongKey(t *testing.T) {
	t.Parallel()

	dataDir := filepath.Join(t.TempDir(), "data")
	store, err := NewFilesystemStore(dataDir, testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}
	if _, err := store.Create(context.Background(), bytes.NewReader([]byte("hello")), "text/plain", time.Hour); err != nil {
		t.Fatalf("Create() error = %v", err)
	}

	wrongKey := []byte("abcdef0123456789abcdef0123456789")
	if _, err := NewFilesystemStore(dataDir, wrongKey); err == nil {
		t.Fatalf("NewFilesystemStore() with wrong key error = nil, want non-nil")
	}
}

func TestConcurrentCreateWithOriginalNameProducesUniqueReadableEntries(t *testing.T) {
	t.Parallel()

	store, err := NewFilesystemStore(filepath.Join(t.TempDir(), "data"), testEncryptionKey)
	if err != nil {
		t.Fatalf("NewFilesystemStore() error = %v", err)
	}

	const writers = 64
	errCh := make(chan error, writers)
	idsCh := make(chan string, writers)
	var wg sync.WaitGroup

	for i := 0; i < writers; i++ {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()

			payload := fmt.Sprintf("storage-writer-%03d-%s", i, strings.Repeat("z", i%13))
			meta, createErr := store.CreateWithOriginalName(
				context.Background(),
				strings.NewReader(payload),
				"text/plain; charset=utf-8",
				fmt.Sprintf("w-%03d.txt", i),
				time.Hour,
			)
			if createErr != nil {
				errCh <- fmt.Errorf("CreateWithOriginalName() error: %w", createErr)
				return
			}

			reader, _, openErr := store.Open(meta.ID)
			if openErr != nil {
				errCh <- fmt.Errorf("Open() error: %w", openErr)
				return
			}
			defer reader.Close()

			got, readErr := io.ReadAll(reader)
			if readErr != nil {
				errCh <- fmt.Errorf("ReadAll() error: %w", readErr)
				return
			}
			if string(got) != payload {
				errCh <- fmt.Errorf("content mismatch = %q, want %q", string(got), payload)
				return
			}

			idsCh <- meta.ID
		}(i)
	}

	wg.Wait()
	close(errCh)
	close(idsCh)
	for err := range errCh {
		t.Error(err)
	}

	seen := make(map[string]struct{}, writers)
	for id := range idsCh {
		if _, exists := seen[id]; exists {
			t.Errorf("duplicate id detected: %s", id)
			continue
		}
		seen[id] = struct{}{}
	}
	if len(seen) != writers {
		t.Fatalf("unique IDs = %d, want %d", len(seen), writers)
	}
}