package session

import (
	"context"
	"errors"
	"net/http"
	"net/http/httptest"
	"reflect"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/alicebob/miniredis/v2"
	"github.com/redis/go-redis/v9"
)

// redisTestHook can pause one Redis command and/or inject an error into script
// and TTL commands. The optional entered channel lets a test wait until the
// command has reached the pause point without relying on a sleep.
type redisTestHook struct {
	gateCommand string
	commandGate chan struct{}
	gateUsed    bool
	commandErrs map[string]error

	mu          sync.Mutex
	entered     chan struct{}
	enteredOnce sync.Once
}

func (hook *redisTestHook) DialHook(next redis.DialHook) redis.DialHook {
	return next
}

func (hook *redisTestHook) ProcessHook(next redis.ProcessHook) redis.ProcessHook {
	return func(ctx context.Context, command redis.Cmder) error {
		commandName := strings.ToLower(command.Name())

		hook.mu.Lock()
		gate := (<-chan struct{})(nil)
		if commandName == hook.gateCommand && hook.commandGate != nil && !hook.gateUsed {
			hook.gateUsed = true
			gate = hook.commandGate
		}
		injectedErr := hook.commandErrs[commandName]
		hook.mu.Unlock()

		if gate != nil {
			if hook.entered != nil {
				hook.enteredOnce.Do(func() { close(hook.entered) })
			}
			<-gate
		}
		if injectedErr != nil && (commandName == "evalsha" || commandName == "eval" || commandName == "pttl") {
			return injectedErr
		}
		return next(ctx, command)
	}
}

func (hook *redisTestHook) ProcessPipelineHook(next redis.ProcessPipelineHook) redis.ProcessPipelineHook {
	return next
}

type redisContextCaptureHook struct {
	mu       sync.Mutex
	contexts []context.Context
}

func (hook *redisContextCaptureHook) DialHook(next redis.DialHook) redis.DialHook {
	return next
}

func (hook *redisContextCaptureHook) ProcessHook(next redis.ProcessHook) redis.ProcessHook {
	return func(ctx context.Context, command redis.Cmder) error {
		commandName := strings.ToLower(command.Name())
		if commandName == "evalsha" || commandName == "eval" {
			hook.mu.Lock()
			hook.contexts = append(hook.contexts, ctx)
			hook.mu.Unlock()
		}
		return next(ctx, command)
	}
}

func (hook *redisContextCaptureHook) ProcessPipelineHook(next redis.ProcessPipelineHook) redis.ProcessPipelineHook {
	return next
}

func (hook *redisContextCaptureHook) snapshot() []context.Context {
	hook.mu.Lock()
	defer hook.mu.Unlock()
	return append([]context.Context(nil), hook.contexts...)
}

func newTest(t *testing.T, ttl time.Duration) (*miniredis.Miniredis, *redis.Client, *Manager) {
	t.Helper()
	miniRedis := miniredis.RunT(t)
	client := redis.NewClient(&redis.Options{Addr: miniRedis.Addr()})
	t.Cleanup(func() { _ = client.Close() })
	return miniRedis, client, NewManager(client, "sid", ttl, false)
}

func (manager *Manager) cachedSession(sid string) (*Session, bool) {
	manager.cacheMu.Lock()
	defer manager.cacheMu.Unlock()
	session, found := manager.cache[sid]
	return session, found
}

func seedCachedSession(manager *Manager, session *Session) *Session {
	manager.cacheMu.Lock()
	defer manager.cacheMu.Unlock()
	manager.cache[session.sid] = session
	return session
}

func expireSessionForTest(session *Session) {
	session.mutex.Lock()
	session.expiresAt = time.Now().Add(-time.Second)
	session.mutex.Unlock()
	session.expire()
}

func getSessionRequest(t *testing.T, manager *Manager, sid string) (SessionInterface, *httptest.ResponseRecorder, error) {
	t.Helper()
	if sid == "" {
		t.Fatal("getSessionRequest requires a non-empty session ID")
	}
	request := httptest.NewRequest(http.MethodGet, "/", nil)
	request.AddCookie(&http.Cookie{Name: "sid", Value: sid})
	recorder := httptest.NewRecorder()
	session, err := manager.GetSession(recorder, request)
	return session, recorder, err
}

func responseSessionID(t *testing.T, recorder *httptest.ResponseRecorder) string {
	t.Helper()
	cookies := recorder.Result().Cookies()
	if len(cookies) == 0 {
		return ""
	}
	return cookies[0].Value
}

func createSession(t *testing.T, manager *Manager) (*Session, string) {
	t.Helper()
	request := httptest.NewRequest(http.MethodGet, "/", nil)
	recorder := httptest.NewRecorder()
	sessionInterface, err := manager.CreateSession(recorder, request)
	if err != nil {
		t.Fatalf("CreateSession returned an error: %v", err)
	}
	session, ok := sessionInterface.(*Session)
	if !ok {
		t.Fatalf("CreateSession returned %T, want *Session", sessionInterface)
	}
	return session, responseSessionID(t, recorder)
}

func waitForHookEntry(t *testing.T, entered <-chan struct{}) {
	t.Helper()
	select {
	case <-entered:
	case <-time.After(time.Second):
		t.Fatal("timed out waiting for Redis command to reach test hook")
	}
}

func TestCreateSessionCanceledRequest(t *testing.T) {
	_, _, manager := newTest(t, time.Minute)
	requestContext, cancel := context.WithCancel(context.Background())
	cancel()
	request := httptest.NewRequest(http.MethodGet, "/", nil).WithContext(requestContext)
	recorder := httptest.NewRecorder()

	session, err := manager.CreateSession(recorder, request)
	if session != nil {
		t.Fatalf("canceled request returned session %v, want nil", session)
	}
	if !errors.Is(err, context.Canceled) {
		t.Fatalf("canceled request error = %v, want context.Canceled", err)
	}
	if cookies := recorder.Result().Cookies(); len(cookies) != 0 {
		t.Fatalf("canceled request emitted %d cookies, want none", len(cookies))
	}
}

func TestGetSessionRequestDeadline(t *testing.T) {
	_, client, manager := newTest(t, time.Minute)
	_, sessionID := createSession(t, manager)
	manager = NewManager(client, "sid", time.Minute, false)
	contextHook := &redisContextCaptureHook{}
	client.AddHook(contextHook)

	request := httptest.NewRequest(http.MethodGet, "/", nil)
	request.AddCookie(&http.Cookie{Name: "sid", Value: sessionID})
	recorder := httptest.NewRecorder()
	startedAt := time.Now()
	session, err := manager.GetSession(recorder, request)
	if err != nil {
		t.Fatalf("GetSession returned an error: %v", err)
	}
	if session == nil {
		t.Fatal("GetSession returned nil session, want existing session")
	}

	contexts := contextHook.snapshot()
	if len(contexts) < 2 {
		t.Fatalf("captured %d Redis script contexts, want read and refresh contexts", len(contexts))
	}
	firstDeadline, hasDeadline := contexts[0].Deadline()
	if !hasDeadline {
		t.Fatal("first Redis script context has no deadline")
	}
	if firstDeadline.Before(startedAt.Add(800*time.Millisecond)) || firstDeadline.After(startedAt.Add(1100*time.Millisecond)) {
		t.Fatalf("first Redis deadline = %v, want approximately one second after request start %v", firstDeadline, startedAt)
	}
	for index, redisContext := range contexts[1:] {
		deadline, hasDeadline := redisContext.Deadline()
		if !hasDeadline || !deadline.Equal(firstDeadline) {
			t.Fatalf("Redis script context %d deadline = %v (has deadline = %v), want shared deadline %v", index+1, deadline, hasDeadline, firstDeadline)
		}
		if redisContext != contexts[0] {
			t.Fatalf("Redis script context %d is not the request-derived context", index+1)
		}
	}
}

func TestCreateSessionIgnoresExistingCookie(t *testing.T) {
	miniRedis, _, manager := newTest(t, time.Minute)
	oldSession, oldSessionID := createSession(t, manager)
	if err := oldSession.Set("marker", "old"); err != nil {
		t.Fatalf("setting marker on old session: %v", err)
	}

	request := httptest.NewRequest(http.MethodGet, "/", nil)
	request.AddCookie(&http.Cookie{Name: "sid", Value: oldSessionID})
	recorder := httptest.NewRecorder()
	createdSession, err := manager.CreateSession(recorder, request)
	if err != nil {
		t.Fatalf("CreateSession returned an error: %v", err)
	}
	newSessionID := responseSessionID(t, recorder)
	if createdSession == nil {
		t.Fatal("CreateSession returned nil session")
	}
	if newSessionID == "" {
		t.Fatal("CreateSession emitted an empty session ID")
	}
	if createdSession.ID() != newSessionID {
		t.Fatalf("created session ID = %q, response cookie ID = %q", createdSession.ID(), newSessionID)
	}
	if newSessionID == oldSessionID {
		t.Fatalf("CreateSession reused old session ID %q", oldSessionID)
	}
	oldKey := sessionKeyPrefix + oldSessionID
	if !miniRedis.Exists(oldKey) || miniRedis.HGet(oldKey, encodeUserField("marker")) != `"old"` {
		t.Fatal("creating a new session changed or removed the old Redis session")
	}
}

func TestGetSessionWithoutID(t *testing.T) {
	testCases := []struct {
		name   string
		cookie *http.Cookie
	}{
		{name: "no cookie"},
		{name: "empty cookie", cookie: &http.Cookie{Name: "sid", Value: ""}},
	}

	for _, testCase := range testCases {
		t.Run(testCase.name, func(t *testing.T) {
			_, client, manager := newTest(t, time.Minute)
			request := httptest.NewRequest(http.MethodGet, "/", nil)
			if testCase.cookie != nil {
				request.AddCookie(testCase.cookie)
			}
			recorder := httptest.NewRecorder()

			gotSession, gotErr := manager.GetSession(recorder, request)
			if gotSession != nil {
				t.Fatalf("GetSession session = %v, want nil", gotSession)
			}
			if !errors.Is(gotErr, ErrSessionNotFound) {
				t.Fatalf("GetSession error = %v, want ErrSessionNotFound", gotErr)
			}
			if gotCookies := len(recorder.Result().Cookies()); gotCookies != 0 {
				t.Fatalf("missing session lookup cookies = %d, want 0", gotCookies)
			}
			if gotCacheSize := len(manager.cache); gotCacheSize != 0 {
				t.Fatalf("missing session lookup cache size = %d, want 0", gotCacheSize)
			}
			keys, err := client.Keys(context.Background(), sessionKeyPrefix+"*").Result()
			if err != nil {
				t.Fatalf("listing session keys: %v", err)
			}
			if len(keys) != 0 {
				t.Fatalf("missing session lookup created Redis keys: %v", keys)
			}
		})
	}
}

func TestGetSessionRefreshesTTL(t *testing.T) {
	const managerTTL = time.Minute
	miniRedis, client, manager := newTest(t, managerTTL)
	createdSession, sessionID := createSession(t, manager)
	miniRedis.FastForward(20 * time.Second)
	beforeRefresh, err := client.PTTL(context.Background(), sessionKeyPrefix+sessionID).Result()
	if err != nil {
		t.Fatalf("reading TTL before retrieval: %v", err)
	}
	if beforeRefresh >= managerTTL-time.Second {
		t.Fatalf("TTL before retrieval = %v, want less than configured TTL %v", beforeRefresh, managerTTL)
	}

	foundSession, recorder, err := getSessionRequest(t, manager, sessionID)
	if err != nil {
		t.Fatalf("GetSession returned an error: %v", err)
	}
	wantSession := createdSession
	if gotSession := foundSession; gotSession != wantSession {
		t.Fatalf("GetSession returned %p, want interned session %p", gotSession, wantSession)
	}
	wantSessionID := sessionID
	if gotSessionID := foundSession.ID(); gotSessionID != wantSessionID {
		t.Fatalf("retrieved session ID = %q, want %q", gotSessionID, wantSessionID)
	}
	wantCookieID := sessionID
	if gotCookieID := responseSessionID(t, recorder); gotCookieID != wantCookieID {
		t.Fatalf("response session ID = %q, want %q", gotCookieID, wantCookieID)
	}
	afterRefresh, err := client.PTTL(context.Background(), sessionKeyPrefix+sessionID).Result()
	if err != nil {
		t.Fatalf("reading TTL after retrieval: %v", err)
	}
	wantMinTTL, wantMaxTTL := managerTTL-time.Second, managerTTL
	if afterRefresh < wantMinTTL || afterRefresh > wantMaxTTL {
		t.Fatalf("TTL after retrieval = %v, want within one second of configured TTL %v", afterRefresh, managerTTL)
	}
}

func TestGetSessionConcurrentLookupsShareSession(t *testing.T) {
	miniRedis, client, writerManager := newTest(t, time.Minute)
	_, sessionID := createSession(t, writerManager)
	readerManager := NewManager(client, "sid", time.Minute, false)
	readGate := make(chan struct{})
	readEntered := make(chan struct{})
	client.AddHook(&redisTestHook{
		gateCommand: "evalsha",
		commandGate: readGate,
		entered:     readEntered,
	})

	const callerCount = 2
	start := make(chan struct{})
	results := make(chan struct {
		session SessionInterface
		err     error
	}, callerCount)
	var waitGroup sync.WaitGroup
	waitGroup.Add(callerCount)
	for range callerCount {
		go func() {
			defer waitGroup.Done()
			<-start
			session, _, err := getSessionRequest(t, readerManager, sessionID)
			results <- struct {
				session SessionInterface
				err     error
			}{session: session, err: err}
		}()
	}
	close(start)
	waitForHookEntry(t, readEntered)
	close(readGate)
	waitGroup.Wait()
	close(results)

	var sessions []SessionInterface
	for result := range results {
		if result.err != nil {
			t.Fatalf("concurrent GetSession returned an error: %v", result.err)
		}
		sessions = append(sessions, result.session)
	}
	if len(sessions) != callerCount {
		t.Fatalf("received %d concurrent results, want %d", len(sessions), callerCount)
	}
	if sessions[0].(*Session) != sessions[1].(*Session) {
		t.Fatal("concurrent lookups returned different in-memory sessions")
	}
	if len(readerManager.cache) != 1 {
		t.Fatalf("reader cache contains %d sessions, want one interned entry", len(readerManager.cache))
	}
	if !miniRedis.Exists(sessionKeyPrefix + sessionID) {
		t.Fatal("concurrent lookup removed the Redis session")
	}
}

func TestGetSessionMissingSIDDoesNotCreate(t *testing.T) {
	_, client, manager := newTest(t, time.Minute)
	missingSessionID := "expired-concurrent"
	seedCachedSession(manager, &Session{sid: missingSessionID, manager: manager})
	readGate := make(chan struct{})
	readEntered := make(chan struct{})
	client.AddHook(&redisTestHook{
		gateCommand: "evalsha",
		commandGate: readGate,
		entered:     readEntered,
	})

	const callerCount = 8
	type lookupResult struct {
		session SessionInterface
		cookies int
		err     error
	}
	start := make(chan struct{})
	ready := make(chan struct{}, callerCount)
	results := make(chan lookupResult, callerCount)
	var waitGroup sync.WaitGroup
	waitGroup.Add(callerCount)
	for range callerCount {
		go func() {
			defer waitGroup.Done()
			<-start
			ready <- struct{}{}
			session, recorder, err := getSessionRequest(t, manager, missingSessionID)
			results <- lookupResult{
				session: session,
				cookies: len(recorder.Result().Cookies()),
				err:     err,
			}
		}()
	}
	close(start)
	for range callerCount {
		<-ready
	}
	waitForHookEntry(t, readEntered)
	close(readGate)
	waitGroup.Wait()
	close(results)

	for result := range results {
		if result.session != nil {
			t.Fatalf("missing lookup returned session %v, want nil", result.session)
		}
		if !errors.Is(result.err, ErrSessionNotFound) {
			t.Fatalf("missing lookup error = %v, want ErrSessionNotFound", result.err)
		}
		if result.cookies != 0 {
			t.Fatalf("missing lookup emitted %d cookies, want none", result.cookies)
		}
	}
	keys, err := client.Keys(context.Background(), sessionKeyPrefix+"*").Result()
	if err != nil {
		t.Fatalf("listing session keys: %v", err)
	}
	if len(keys) != 0 {
		t.Fatalf("missing lookup created Redis keys: %v", keys)
	}
	if _, found := manager.cachedSession(missingSessionID); found {
		t.Fatal("missing lookup retained a cache placeholder")
	}
}

func TestRedisReadSerializesMutation(t *testing.T) {
	_, client, manager := newTest(t, time.Minute)
	session, sessionID := createSession(t, manager)
	readGate := make(chan struct{})
	readEntered := make(chan struct{})
	client.AddHook(&redisTestHook{
		gateCommand: "evalsha",
		commandGate: readGate,
		entered:     readEntered,
	})

	readDone := make(chan struct{})
	go func() {
		_, _, _ = getSessionRequest(t, manager, sessionID)
		close(readDone)
	}()
	waitForHookEntry(t, readEntered)

	mutationDone := make(chan error)
	go func() { mutationDone <- session.Set("x", 1) }()
	select {
	case err := <-mutationDone:
		t.Fatalf("session mutation completed before Redis read released: %v", err)
	case <-time.After(20 * time.Millisecond):
	}
	close(readGate)
	if err := <-mutationDone; err != nil {
		t.Fatalf("session mutation after read release: %v", err)
	}
	<-readDone
}

func TestDifferentSessionsIndependentLocks(t *testing.T) {
	_, client, manager := newTest(t, time.Minute)
	_, firstSessionID := createSession(t, manager)
	_, secondSessionID := createSession(t, manager)
	readGate := make(chan struct{})
	readEntered := make(chan struct{})
	client.AddHook(&redisTestHook{
		gateCommand: "evalsha",
		commandGate: readGate,
		entered:     readEntered,
	})

	firstReadDone := make(chan error)
	go func() {
		_, _, err := getSessionRequest(t, manager, firstSessionID)
		firstReadDone <- err
	}()
	waitForHookEntry(t, readEntered)
	if _, _, err := getSessionRequest(t, manager, secondSessionID); err != nil {
		t.Fatalf("lookup of independent session blocked or failed: %v", err)
	}
	close(readGate)
	if err := <-firstReadDone; err != nil {
		t.Fatalf("first session lookup after release: %v", err)
	}
}

func TestManagersUpdateFieldsWithoutLostWrites(t *testing.T) {
	_, client, firstManager := newTest(t, time.Minute)
	secondManager := NewManager(client, "sid", time.Minute, false)
	_, sessionID := createSession(t, firstManager)
	firstSession, _, err := getSessionRequest(t, firstManager, sessionID)
	if err != nil {
		t.Fatalf("loading first manager session: %v", err)
	}
	secondSession, _, err := getSessionRequest(t, secondManager, sessionID)
	if err != nil {
		t.Fatalf("loading second manager session: %v", err)
	}
	if err := firstSession.Set("a", "one"); err != nil {
		t.Fatalf("setting field a: %v", err)
	}
	if err := secondSession.Set("b", "two"); err != nil {
		t.Fatalf("setting field b: %v", err)
	}

	values, err := client.HGetAll(context.Background(), sessionKeyPrefix+sessionID).Result()
	if err != nil {
		t.Fatalf("reading session hash: %v", err)
	}
	if values[encodeUserField("a")] != `"one"` || values[encodeUserField("b")] != `"two"` {
		t.Fatalf("session hash fields = %v, want both independent writes", values)
	}
	freshSession, _, err := getSessionRequest(t, NewManager(client, "sid", time.Minute, false), sessionID)
	if err != nil {
		t.Fatalf("loading fresh manager session: %v", err)
	}
	if got := freshSession.Get("a"); got != "one" {
		t.Fatalf("fresh session field a = %v, want %q", got, "one")
	}
	if got := freshSession.Get("b"); got != "two" {
		t.Fatalf("fresh session field b = %v, want %q", got, "two")
	}
}

func TestSessionJSONValuesAreIsolated(t *testing.T) {
	_, _, manager := newTest(t, time.Minute)
	session, _ := createSession(t, manager)
	input := map[string]any{"x": []any{1.0}}
	if err := session.Set("obj", input); err != nil {
		t.Fatalf("setting object field: %v", err)
	}
	input["x"].([]any)[0] = 9
	if got := session.Get("obj").(map[string]any)["x"].([]any)[0]; got != 1.0 {
		t.Fatalf("stored object changed after mutating input: got %v, want 1", got)
	}
	output := session.Get("obj").(map[string]any)
	output["x"].([]any)[0] = 8
	if got := session.Get("obj").(map[string]any)["x"].([]any)[0]; got != 1.0 {
		t.Fatalf("stored object changed after mutating returned value: got %v, want 1", got)
	}
}

func TestGetMissingKey(t *testing.T) {
	_, _, manager := newTest(t, time.Minute)
	session, _ := createSession(t, manager)
	if got := session.Get("missing"); got != nil {
		t.Fatalf("missing field = %v, want nil", got)
	}
}

func TestSessionMutationRefreshesTTL(t *testing.T) {
	const configuredTTL = 60 * time.Second
	miniRedis, client, manager := newTest(t, configuredTTL)
	session, sessionID := createSession(t, manager)
	operations := []struct {
		name    string
		call    func() error
		wantErr error
	}{
		{
			name:    "set",
			call:    func() error { return session.Set("x", 1) },
			wantErr: nil,
		},
		{
			name:    "delete",
			call:    func() error { return session.Delete("x") },
			wantErr: nil,
		},
		{
			name:    "update TTL",
			call:    session.UpdateTTL,
			wantErr: nil,
		},
	}
	for _, operation := range operations {
		t.Run(operation.name, func(t *testing.T) {
			miniRedis.FastForward(20 * time.Second)
			gotErr := operation.call()
			if !errors.Is(gotErr, operation.wantErr) {
				t.Fatalf("%s operation error = %v, want %v", operation.name, gotErr, operation.wantErr)
			}
			remainingTTL, err := client.PTTL(context.Background(), sessionKeyPrefix+sessionID).Result()
			if err != nil {
				t.Fatalf("reading TTL after %s: %v", operation.name, err)
			}
			wantMinTTL, wantMaxTTL := configuredTTL-time.Second, configuredTTL
			if remainingTTL < wantMinTTL || remainingTTL > wantMaxTTL {
				t.Fatalf("TTL after %s = %v, want within one second of %v", operation.name, remainingTTL, configuredTTL)
			}
		})
	}
}

func TestSessionScriptErrorPreservesSession(t *testing.T) {
	_, client, manager := newTest(t, time.Minute)
	session, sessionID := createSession(t, manager)
	if err := session.Set("x", "ok"); err != nil {
		t.Fatalf("seeding ready session: %v", err)
	}
	sentinelError := errors.New("boom")
	client.AddHook(&redisTestHook{commandErrs: map[string]error{"evalsha": sentinelError, "eval": sentinelError}})

	gotErr := session.Set("y", 1)
	if !errors.Is(gotErr, sentinelError) {
		t.Fatalf("failed mutation error = %v, want sentinel error", gotErr)
	}
	if got := session.Get("x"); got != "ok" {
		t.Fatalf("ready session lost existing value after script error: got %v, want %q", got, "ok")
	}
	if _, found := manager.cachedSession(sessionID); !found {
		t.Fatal("ready session was removed from cache after script error")
	}
}

func TestFirstLoadEvictsPlaceholder(t *testing.T) {
	_, client, manager := newTest(t, time.Minute)
	sentinelError := errors.New("boom")
	client.AddHook(&redisTestHook{commandErrs: map[string]error{"evalsha": sentinelError, "eval": sentinelError}})
	_, _, gotErr := getSessionRequest(t, manager, "missing")
	if !errors.Is(gotErr, sentinelError) {
		t.Fatalf("first load error = %v, want sentinel error", gotErr)
	}
	if len(manager.cache) != 0 {
		t.Fatalf("failed first load left %d cache entries, want none", len(manager.cache))
	}
}

func TestInvalidHashDataPreservesForeignData(t *testing.T) {
	miniRedis, client, manager := newTest(t, time.Minute)
	invalidHashCases := []struct {
		name string
		seed func()
	}{
		{
			name: "unsupported schema",
			seed: func() { miniRedis.HSet(sessionKeyPrefix+"x", metadataField, "2") },
		},
		{
			name: "unknown hash field",
			seed: func() { miniRedis.HSet(sessionKeyPrefix+"x", metadataField, "1", "junk", "1") },
		},
		{
			name: "malformed JSON",
			seed: func() {
				miniRedis.HSet(sessionKeyPrefix+"x", metadataField, "1", encodeUserField("x"), "not-json")
			},
		},
	}
	for _, testCase := range invalidHashCases {
		t.Run(testCase.name, func(t *testing.T) {
			miniRedis.FlushAll()
			manager = NewManager(client, "sid", time.Minute, false)
			testCase.seed()
			_, _, err := getSessionRequest(t, manager, "x")
			if !errors.Is(err, ErrInvalidSessionData) {
				t.Fatalf("GetSession error = %v, want ErrInvalidSessionData", err)
			}
		})
	}

	const foreignTTL = 30 * time.Second
	const foreignString = `{"x":1}`
	foreignDataCases := []struct {
		name       string
		seed       func() error
		wantType   string
		wantValues []string
	}{
		{
			name: "foreign list",
			seed: func() error {
				if err := client.RPush(context.Background(), sessionKeyPrefix+"x", "bad", "data").Err(); err != nil {
					return err
				}
				return client.Expire(context.Background(), sessionKeyPrefix+"x", foreignTTL).Err()
			},
			wantType:   "list",
			wantValues: []string{"bad", "data"},
		},
		{
			name: "foreign string",
			seed: func() error {
				return client.Set(context.Background(), sessionKeyPrefix+"x", foreignString, foreignTTL).Err()
			},
			wantType:   "string",
			wantValues: []string{foreignString},
		},
	}
	for _, testCase := range foreignDataCases {
		t.Run(testCase.name, func(t *testing.T) {
			miniRedis.FlushAll()
			manager = NewManager(client, "sid", time.Minute, false)
			if err := testCase.seed(); err != nil {
				t.Fatalf("seeding foreign %s: %v", testCase.name, err)
			}

			capture := func() (string, []string, time.Duration) {
				key := sessionKeyPrefix + "x"
				valueType, err := client.Type(context.Background(), key).Result()
				if err != nil {
					t.Fatalf("reading foreign %s type: %v", testCase.name, err)
				}
				var values []string
				switch valueType {
				case "list":
					values, err = client.LRange(context.Background(), key, 0, -1).Result()
				case "string":
					var value string
					value, err = client.Get(context.Background(), key).Result()
					values = []string{value}
				default:
					t.Fatalf("foreign %s type = %q, want list or string", testCase.name, valueType)
				}
				if err != nil {
					t.Fatalf("reading foreign %s value: %v", testCase.name, err)
				}
				ttl, err := client.PTTL(context.Background(), key).Result()
				if err != nil {
					t.Fatalf("reading foreign %s TTL: %v", testCase.name, err)
				}
				return valueType, values, ttl
			}

			beforeType, beforeValues, beforeTTL := capture()
			if beforeType != testCase.wantType {
				t.Fatalf("foreign %s type before GetSession = %q, want %q", testCase.name, beforeType, testCase.wantType)
			}
			if !reflect.DeepEqual(beforeValues, testCase.wantValues) {
				t.Fatalf("foreign %s value before GetSession = %q, want %q", testCase.name, beforeValues, testCase.wantValues)
			}
			if beforeTTL <= 0 {
				t.Fatalf("foreign %s TTL before GetSession = %v, want positive TTL", testCase.name, beforeTTL)
			}

			_, recorder, err := getSessionRequest(t, manager, "x")
			if !errors.Is(err, ErrInvalidSessionData) {
				t.Fatalf("GetSession error = %v, want ErrInvalidSessionData", err)
			}
			if cookies := recorder.Result().Cookies(); len(cookies) != 0 {
				t.Fatalf("invalid %s session emitted %d replacement cookies, want none", testCase.name, len(cookies))
			}

			afterType, afterValues, afterTTL := capture()
			if afterType != beforeType {
				t.Fatalf("foreign %s type changed from %q to %q", testCase.name, beforeType, afterType)
			}
			if !reflect.DeepEqual(afterValues, beforeValues) {
				t.Fatalf("foreign %s value changed from %q to %q", testCase.name, beforeValues, afterValues)
			}
			if afterTTL < beforeTTL-time.Second || afterTTL > beforeTTL+time.Second {
				t.Fatalf("foreign %s TTL changed from %v to %v", testCase.name, beforeTTL, afterTTL)
			}
		})
	}
}

func TestMalformedSessionReadPreservesTTL(t *testing.T) {
	const managerTTL = time.Minute
	const shortTTL = 10 * time.Second
	miniRedis, client, manager := newTest(t, managerTTL)
	sessionID := "malformed-ttl"
	sessionKey := sessionKeyPrefix + sessionID
	miniRedis.HSet(sessionKey, metadataField, schemaVersion, encodeUserField("user"), "not-json")
	if ok, err := client.Expire(context.Background(), sessionKey, shortTTL).Result(); err != nil || !ok {
		t.Fatalf("seeding malformed-session TTL: ok=%v err=%v", ok, err)
	}

	_, _, err := getSessionRequest(t, manager, sessionID)
	if !errors.Is(err, ErrInvalidSessionData) {
		t.Fatalf("GetSession error = %v, want ErrInvalidSessionData", err)
	}
	remainingTTL, err := client.PTTL(context.Background(), sessionKey).Result()
	if err != nil {
		t.Fatalf("reading malformed-session TTL: %v", err)
	}
	if remainingTTL <= 0 || remainingTTL >= managerTTL/2 {
		t.Fatalf("malformed-session TTL = %v, want positive TTL well below manager TTL", remainingTTL)
	}
}

func TestDestroyCanBeCalledTwice(t *testing.T) {
	miniRedis, _, manager := newTest(t, time.Minute)
	session, sessionID := createSession(t, manager)
	if err := session.Destroy(); err != nil {
		t.Fatalf("first Destroy call: %v", err)
	}
	if err := session.Destroy(); err != nil {
		t.Fatalf("second Destroy call: %v", err)
	}
	if session.ID() != sessionID {
		t.Fatalf("destroyed session ID = %q, want original %q", session.ID(), sessionID)
	}
	if session.Get("x") != nil {
		t.Fatal("destroyed session returned a stored value")
	}
	if _, found := manager.cachedSession(sessionID); found {
		t.Fatal("destroyed session remained cached")
	}
	if miniRedis.Exists(sessionKeyPrefix + sessionID) {
		t.Fatal("destroyed session Redis key still exists")
	}
}

func TestExpiredSessionEvictsIdleEntry(t *testing.T) {
	miniRedis, _, manager := newTest(t, time.Minute)
	session, sessionID := createSession(t, manager)
	miniRedis.Del(sessionKeyPrefix + sessionID)
	expireSessionForTest(session)
	if _, found := manager.cachedSession(sessionID); found {
		t.Fatal("expired idle session remained cached after Redis key disappeared")
	}
}

func TestFirstLoadOperationalErrorReachesCaller(t *testing.T) {
	miniRedis, client, manager := newTest(t, time.Minute)
	sessionID := "operational-error"
	miniRedis.HSet(sessionKeyPrefix+sessionID, metadataField, schemaVersion)
	sentinelError := errors.New("sentinel redis failure")
	client.AddHook(&redisTestHook{commandErrs: map[string]error{"evalsha": sentinelError, "eval": sentinelError}})

	placeholder := seedCachedSession(manager, &Session{sid: sessionID, manager: manager})
	if err := placeholder.redisReadAndRefresh(context.Background()); !errors.Is(err, sentinelError) {
		t.Fatalf("first load error = %v, want sentinel error", err)
	}
	if !placeholder.isClosed() {
		t.Fatal("failed first-load placeholder was not marked closed")
	}
	if cached, found := manager.cachedSession(sessionID); !found || cached != placeholder {
		t.Fatal("failed first-load placeholder was not retained for the waiting caller")
	}

	session, recorder, err := getSessionRequest(t, manager, sessionID)
	if session != nil {
		t.Fatalf("waiting caller returned session %v, want nil", session)
	}
	if !errors.Is(err, sentinelError) {
		t.Fatalf("waiting caller error = %v, want sentinel error", err)
	}
	if cookies := recorder.Result().Cookies(); len(cookies) != 0 {
		t.Fatalf("waiting caller emitted %d replacement cookies, want none", len(cookies))
	}
	if _, found := manager.cachedSession(sessionID); found {
		t.Fatal("failed first-load placeholder remained cached after waiting caller cleanup")
	}
}

func TestFirstLoadInvalidDataReachesCaller(t *testing.T) {
	miniRedis, _, manager := newTest(t, time.Minute)
	sessionID := "invalid-data"
	sessionKey := sessionKeyPrefix + sessionID
	miniRedis.HSet(sessionKey, metadataField, schemaVersion, "foreign", "value")

	placeholder := seedCachedSession(manager, &Session{sid: sessionID, manager: manager})
	if err := placeholder.redisReadAndRefresh(context.Background()); !errors.Is(err, ErrInvalidSessionData) {
		t.Fatalf("first load error = %v, want ErrInvalidSessionData", err)
	}
	if !placeholder.isClosed() {
		t.Fatal("invalid first-load placeholder was not marked closed")
	}
	if cached, found := manager.cachedSession(sessionID); !found || cached != placeholder {
		t.Fatal("invalid first-load placeholder was not retained for the waiting caller")
	}

	session, recorder, err := getSessionRequest(t, manager, sessionID)
	if session != nil {
		t.Fatalf("waiting caller returned session %v, want nil", session)
	}
	if !errors.Is(err, ErrInvalidSessionData) {
		t.Fatalf("waiting caller error = %v, want ErrInvalidSessionData", err)
	}
	if cookies := recorder.Result().Cookies(); len(cookies) != 0 {
		t.Fatalf("waiting caller emitted %d replacement cookies, want none", len(cookies))
	}
	if _, found := manager.cachedSession(sessionID); found {
		t.Fatal("invalid first-load placeholder remained cached after waiting caller cleanup")
	}
	if !miniRedis.Exists(sessionKey) || miniRedis.HGet(sessionKey, "foreign") != "value" {
		t.Fatal("invalid foreign Redis data was deleted or changed")
	}
}

func TestNewManagerCookieName(t *testing.T) {
	testCases := []struct {
		name          string
		cookieName    string
		shouldBeValid bool
	}{
		{
			name:          "empty name",
			cookieName:    "",
			shouldBeValid: false,
		},
		{
			name:          "invalid name",
			cookieName:    "bad name",
			shouldBeValid: false,
		},
		{
			name:          "valid name",
			cookieName:    "sid",
			shouldBeValid: true,
		},
	}
	for _, testCase := range testCases {
		t.Run(testCase.name, func(t *testing.T) {
			if testCase.shouldBeValid {
				if manager := NewManager(nil, testCase.cookieName, time.Minute, false); manager == nil {
					t.Fatal("NewManager returned nil for valid cookie name")
				}
				return
			}
			defer func() {
				if recovered := recover(); recovered != "session: invalid cookie name" {
					t.Fatalf("panic = %v, want exact invalid-cookie panic", recovered)
				}
			}()
			NewManager(nil, testCase.cookieName, time.Minute, false)
		})
	}
}

func TestNewManagerRejectsShortTTL(t *testing.T) {
	defer func() {
		if recovered := recover(); recovered != "session: ttl must be at least 1 second" {
			t.Fatalf("panic = %v, want minimum-TTL validation panic", recovered)
		}
	}()
	NewManager(nil, "sid", time.Second-time.Nanosecond, false)
}

func TestExpireKeepsSessionAfterRefresh(t *testing.T) {
	_, client, firstManager := newTest(t, time.Minute)
	secondManager := NewManager(client, "sid", time.Minute, false)
	firstSession, sessionID := createSession(t, firstManager)
	secondSession, _, err := getSessionRequest(t, secondManager, sessionID)
	if err != nil {
		t.Fatalf("loading session through second manager: %v", err)
	}
	if err := secondSession.UpdateTTL(); err != nil {
		t.Fatalf("refreshing TTL through second manager: %v", err)
	}

	expireSessionForTest(firstSession)
	if _, found := firstManager.cachedSession(sessionID); !found {
		t.Fatal("local expiry evicted a session refreshed by another manager")
	}
}

func TestParseReadResult(t *testing.T) {
	var command redis.Cmd
	command.SetVal([]any{int64(1), metadataField, "1", encodeUserField("n"), "2"})

	schema, values, err := parseReadResult(&command)
	if err != nil {
		t.Fatalf("parseReadResult returned an error: %v", err)
	}
	if schema != 1 {
		t.Fatalf("parsed schema version = %d, want 1", schema)
	}
	if string(values["n"]) != "2" {
		t.Fatalf("parsed user field n = %q, want %q", values["n"], "2")
	}
}

func TestExpiredSessionMutations(t *testing.T) {
	testCases := []struct {
		name    string
		mutate  func(*Session) error
		wantErr error
	}{
		{
			name:    "set",
			mutate:  func(session *Session) error { return session.Set("x", 1) },
			wantErr: ErrSessionClosed,
		},
		{
			name:    "delete",
			mutate:  func(session *Session) error { return session.Delete("x") },
			wantErr: ErrSessionClosed,
		},
		{
			name:    "update TTL",
			mutate:  func(session *Session) error { return session.UpdateTTL() },
			wantErr: redis.Nil,
		},
	}
	for _, testCase := range testCases {
		t.Run(testCase.name, func(t *testing.T) {
			miniRedis, _, manager := newTest(t, time.Minute)
			session, sessionID := createSession(t, manager)
			miniRedis.Del(sessionKeyPrefix + sessionID)

			gotErr := testCase.mutate(session)
			if !errors.Is(gotErr, testCase.wantErr) {
				t.Fatalf("expired %s error = %v, want %v", testCase.name, gotErr, testCase.wantErr)
			}
			if miniRedis.Exists(sessionKeyPrefix + sessionID) {
				t.Fatal("expired session mutation resurrected the Redis key")
			}
			if _, found := manager.cachedSession(sessionID); found {
				t.Fatal("closed session remained cached after expired mutation")
			}
		})
	}
}

func TestHashFieldEncodingRoundTrips(t *testing.T) {
	_, _, manager := newTest(t, time.Minute)
	session, _ := createSession(t, manager)
	fieldNames := []string{"", "世界/ punctuation!", "_meta", "v:abc"}
	for _, fieldName := range fieldNames {
		if err := session.Set(fieldName, 7); err != nil {
			t.Fatalf("setting field %q: %v", fieldName, err)
		}
		value, ok := session.Get(fieldName).(float64)
		if !ok || value != 7 {
			t.Fatalf("field %q decoded as %#v, want float64(7)", fieldName, session.Get(fieldName))
		}
	}
}

func TestSameHashFieldUsesLastWrite(t *testing.T) {
	_, client, firstManager := newTest(t, time.Minute)
	secondManager := NewManager(client, "sid", time.Minute, false)
	_, sessionID := createSession(t, firstManager)
	firstSession, _, err := getSessionRequest(t, firstManager, sessionID)
	if err != nil {
		t.Fatalf("loading first session: %v", err)
	}
	secondSession, _, err := getSessionRequest(t, secondManager, sessionID)
	if err != nil {
		t.Fatalf("loading second session: %v", err)
	}
	if err := firstSession.Set("same", "first"); err != nil {
		t.Fatalf("first write: %v", err)
	}
	if err := secondSession.Set("same", "second"); err != nil {
		t.Fatalf("second write: %v", err)
	}
	if got := secondSession.Get("same"); got != "second" {
		t.Fatalf("same-field value = %v, want %q after last successful write", got, "second")
	}
}

func TestExpireRetriesAfterPTTLFailure(t *testing.T) {
	_, client, manager := newTest(t, time.Minute)
	session, sessionID := createSession(t, manager)
	client.AddHook(&redisTestHook{commandErrs: map[string]error{"pttl": errors.New("temporary")}})
	expireSessionForTest(session)
	if _, found := manager.cachedSession(sessionID); !found {
		t.Fatal("PTTL failure evicted the session instead of retaining it")
	}
	session.mutex.RLock()
	retryScheduled := session.expiresAt.After(time.Now())
	session.mutex.RUnlock()
	if !retryScheduled {
		t.Fatal("PTTL failure did not schedule a future expiry retry")
	}
}

func ExampleManager_CreateSession() {
	miniRedis, err := miniredis.Run()
	if err != nil {
		return
	}
	defer miniRedis.Close()
	client := redis.NewClient(&redis.Options{Addr: miniRedis.Addr()})
	defer client.Close()
	manager := NewManager(client, "session_id", 96*time.Hour, true)
	request := httptest.NewRequest(http.MethodGet, "/", nil)
	recorder := httptest.NewRecorder()
	_, _ = manager.CreateSession(recorder, request)
}

func ExampleManager_GetSession() {
	miniRedis, err := miniredis.Run()
	if err != nil {
		return
	}
	defer miniRedis.Close()
	client := redis.NewClient(&redis.Options{Addr: miniRedis.Addr()})
	defer client.Close()
	manager := NewManager(client, "session_id", 96*time.Hour, true)
	createRequest := httptest.NewRequest(http.MethodGet, "/", nil)
	createRecorder := httptest.NewRecorder()
	_, _ = manager.CreateSession(createRecorder, createRequest)
	request := httptest.NewRequest(http.MethodGet, "/", nil)
	for _, cookie := range createRecorder.Result().Cookies() {
		request.AddCookie(cookie)
	}
	recorder := httptest.NewRecorder()
	_, _ = manager.GetSession(recorder, request)
}