package session_test

import (
	"context"
	"log/slog"
	"net/http"
	"net/http/httptest"
	"os"
	"testing"
	"time"

	"github.com/gorilla/sessions"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"sneak.berlin/go/webhooker/internal/config"
	"sneak.berlin/go/webhooker/internal/session"
)

const testKeySize = 32

// testIdleTimeout is the idle window used by the expiry tests.
const testIdleTimeout = time.Hour

// testAbsoluteMaxAge restates the documented absolute session cap
// independently of the implementation constant.
const testAbsoluteMaxAge = 7 * 24 * time.Hour

// fakeClock is a manually advanced clock, so expiry can be tested
// without sleeping.
type fakeClock struct {
	t time.Time
}

func (c *fakeClock) Now() time.Time {
	return c.t
}

func (c *fakeClock) Advance(d time.Duration) {
	c.t = c.t.Add(d)
}

// testSession creates a Session with a real cookie store and the
// real clock.
func testSession(t *testing.T) *session.Session {
	t.Helper()

	s, _ := testSessionWithClock(t, testIdleTimeout, nil)

	return s
}

// testSessionWithClock creates a Session with a real cookie store,
// the given idle timeout, and a manually advanced clock. Passing a
// nil clock uses the real one.
func testSessionWithClock(
	t *testing.T,
	idleTimeout time.Duration,
	clock *fakeClock,
) (*session.Session, *fakeClock) {
	t.Helper()

	key := make([]byte, testKeySize)

	for i := range key {
		key[i] = byte(i + 42)
	}

	store := sessions.NewCookieStore(key)
	store.Options = &sessions.Options{
		Path:     "/",
		MaxAge:   86400 * 7,
		HttpOnly: true,
		Secure:   false,
		SameSite: http.SameSiteLaxMode,
	}

	cfg := &config.Config{
		Environment:        config.EnvironmentDev,
		SessionIdleTimeout: idleTimeout,
	}

	log := slog.New(slog.NewTextHandler(
		os.Stderr,
		&slog.HandlerOptions{Level: slog.LevelDebug},
	))

	var now func() time.Time

	if clock != nil {
		now = clock.Now
	}

	return session.NewForTest(store, cfg, log, key, now), clock
}

// newFakeClock returns a clock started at a fixed instant.
func newFakeClock() *fakeClock {
	return &fakeClock{
		t: time.Date(
			2026, time.January, 2, 3, 4, 5, 0, time.UTC,
		),
	}
}

// authenticatedSession returns a fresh session that has just been
// logged in, along with its manager and clock.
func authenticatedSession(
	t *testing.T,
	idleTimeout time.Duration,
) (*session.Session, *sessions.Session, *fakeClock) {
	t.Helper()

	s, clock := testSessionWithClock(
		t, idleTimeout, newFakeClock(),
	)

	req := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)

	sess, err := s.Get(req)
	require.NoError(t, err)

	s.SetUser(sess, "user-123", "alice")
	require.True(t, s.IsAuthenticated(sess))

	return s, sess, clock
}

// --- Get and Save Tests ---

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

	s := testSession(t)

	req := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)

	sess, err := s.Get(req)
	require.NoError(t, err)
	require.NotNil(t, sess)
	assert.True(
		t, sess.IsNew,
		"session should be new when no cookie is present",
	)
}

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

	s := testSession(t)

	// Create and save a session
	req1 := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)
	w1 := httptest.NewRecorder()

	sess1, err := s.Get(req1)
	require.NoError(t, err)

	sess1.Values["test_key"] = "test_value"
	require.NoError(t, s.Save(req1, w1, sess1))

	// Extract cookies
	cookies := w1.Result().Cookies()
	require.NotEmpty(t, cookies)

	// Make a new request with the session cookie
	req2 := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)

	for _, c := range cookies {
		req2.AddCookie(c)
	}

	sess2, err := s.Get(req2)
	require.NoError(t, err)
	assert.False(
		t, sess2.IsNew,
		"session should not be new when cookie is present",
	)
	assert.Equal(t, "test_value", sess2.Values["test_key"])
}

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

	s := testSession(t)

	req := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)
	w := httptest.NewRecorder()

	sess, err := s.Get(req)
	require.NoError(t, err)

	sess.Values["key"] = "value"

	err = s.Save(req, w, sess)
	require.NoError(t, err)

	cookies := w.Result().Cookies()
	require.NotEmpty(t, cookies, "Save should set a cookie")

	// Verify the cookie has the expected name
	var found bool

	for _, c := range cookies {
		if c.Name == session.SessionName {
			found = true

			assert.True(
				t, c.HttpOnly,
				"session cookie should be HTTP-only",
			)

			break
		}
	}

	assert.True(
		t, found,
		"should find a cookie named %s", session.SessionName,
	)
}

// --- SetUser and User Retrieval Tests ---

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

	s := testSession(t)

	req := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)

	sess, err := s.Get(req)
	require.NoError(t, err)

	s.SetUser(sess, "user-abc-123", "alice")

	assert.Equal(
		t, "user-abc-123", sess.Values[session.UserIDKey],
	)
	assert.Equal(
		t, "alice", sess.Values[session.UsernameKey],
	)
	assert.Equal(
		t, true, sess.Values[session.AuthenticatedKey],
	)
}

// testSessionGetter exercises a session string getter before and
// after SetUser: it must report false with an empty value on a
// fresh session, then true with the expected value once
// SetUser(sess, "user-xyz", "bob") has run.
func testSessionGetter(
	t *testing.T,
	get func(
		*session.Session, *sessions.Session,
	) (string, bool),
	expected string,
) {
	t.Helper()

	s := testSession(t)

	req := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)

	sess, err := s.Get(req)
	require.NoError(t, err)

	// Before setting user
	val, ok := get(s, sess)
	assert.False(
		t, ok, "should return false before SetUser",
	)
	assert.Empty(t, val)

	// After setting user
	s.SetUser(sess, "user-xyz", "bob")

	val, ok = get(s, sess)
	assert.True(t, ok)
	assert.Equal(t, expected, val)
}

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

	testSessionGetter(
		t,
		func(
			s *session.Session, sess *sessions.Session,
		) (string, bool) {
			return s.GetUserID(sess)
		},
		"user-xyz",
	)
}

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

	testSessionGetter(
		t,
		func(
			s *session.Session, sess *sessions.Session,
		) (string, bool) {
			return s.GetUsername(sess)
		},
		"bob",
	)
}

// --- IsAuthenticated Tests ---

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

	s := testSession(t)

	req := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)

	sess, err := s.Get(req)
	require.NoError(t, err)

	assert.False(
		t, s.IsAuthenticated(sess),
		"new session should not be authenticated",
	)
}

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

	s := testSession(t)

	req := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)

	sess, err := s.Get(req)
	require.NoError(t, err)

	s.SetUser(sess, "user-123", "alice")
	assert.True(t, s.IsAuthenticated(sess))
}

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

	s := testSession(t)

	req := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)

	sess, err := s.Get(req)
	require.NoError(t, err)

	s.SetUser(sess, "user-123", "alice")
	require.True(t, s.IsAuthenticated(sess))

	s.ClearUser(sess)

	assert.False(
		t, s.IsAuthenticated(sess),
		"should not be authenticated after ClearUser",
	)
}

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

	s := testSession(t)

	req := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)

	sess, err := s.Get(req)
	require.NoError(t, err)

	// Set authenticated to a non-bool value
	sess.Values[session.AuthenticatedKey] = "yes"

	assert.False(
		t, s.IsAuthenticated(sess),
		"should return false for non-bool authenticated value",
	)
}

// --- ClearUser Tests ---

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

	s := testSession(t)

	req := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)

	sess, err := s.Get(req)
	require.NoError(t, err)

	s.SetUser(sess, "user-123", "alice")
	s.ClearUser(sess)

	_, hasUserID := sess.Values[session.UserIDKey]
	assert.False(t, hasUserID, "UserIDKey should be removed")

	_, hasUsername := sess.Values[session.UsernameKey]
	assert.False(t, hasUsername, "UsernameKey should be removed")

	_, hasAuth := sess.Values[session.AuthenticatedKey]
	assert.False(
		t, hasAuth, "AuthenticatedKey should be removed",
	)
}

// --- Destroy Tests ---

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

	s := testSession(t)

	req := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)

	sess, err := s.Get(req)
	require.NoError(t, err)

	s.SetUser(sess, "user-123", "alice")

	s.Destroy(sess)

	// After Destroy: MaxAge should be -1 (delete cookie) and
	// user data cleared
	assert.Equal(
		t, -1, sess.Options.MaxAge,
		"Destroy should set MaxAge to -1",
	)
	assert.False(
		t, s.IsAuthenticated(sess),
		"should not be authenticated after Destroy",
	)

	_, hasUserID := sess.Values[session.UserIDKey]
	assert.False(t, hasUserID, "Destroy should clear user ID")
}

// --- Session Persistence Round-Trip ---

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

	s := testSession(t)

	// Step 1: Create session, set user, save
	req1 := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)
	w1 := httptest.NewRecorder()

	sess1, err := s.Get(req1)
	require.NoError(t, err)
	s.SetUser(sess1, "user-round-trip", "charlie")
	require.NoError(t, s.Save(req1, w1, sess1))

	cookies := w1.Result().Cookies()
	require.NotEmpty(t, cookies)

	// Step 2: New request with cookies -- session data should
	// persist
	req2 := httptest.NewRequestWithContext(
		context.Background(),
		http.MethodGet, "/profile", nil,
	)

	for _, c := range cookies {
		req2.AddCookie(c)
	}

	sess2, err := s.Get(req2)
	require.NoError(t, err)

	assert.True(
		t, s.IsAuthenticated(sess2),
		"session should be authenticated after round-trip",
	)

	userID, ok := s.GetUserID(sess2)
	assert.True(t, ok)
	assert.Equal(t, "user-round-trip", userID)

	username, ok := s.GetUsername(sess2)
	assert.True(t, ok)
	assert.Equal(t, "charlie", username)
}

// --- Constants Tests ---

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

	assert.Equal(t, "webhooker_session", session.SessionName)
	assert.Equal(t, "user_id", session.UserIDKey)
	assert.Equal(t, "username", session.UsernameKey)
	assert.Equal(t, "authenticated", session.AuthenticatedKey)
	assert.Equal(t, "created_at", session.CreatedAtKey)
	assert.Equal(t, "last_seen", session.LastSeenKey)
}

// --- Expiry Tests ---

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

	_, sess, clock := authenticatedSession(t, testIdleTimeout)

	assert.Equal(
		t, clock.Now().Unix(), sess.Values[session.CreatedAtKey],
		"SetUser should anchor the absolute clock",
	)
	assert.Equal(
		t, clock.Now().Unix(), sess.Values[session.LastSeenKey],
		"SetUser should anchor the idle clock",
	)
}

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

	s, sess, clock := authenticatedSession(t, testIdleTimeout)

	clock.Advance(testIdleTimeout - time.Second)

	assert.True(
		t, s.IsAuthenticated(sess),
		"session should still be valid just inside the idle window",
	)
}

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

	s, sess, clock := authenticatedSession(t, testIdleTimeout)

	clock.Advance(testIdleTimeout)

	assert.False(
		t, s.IsAuthenticated(sess),
		"session should expire once the idle window lapses",
	)
}

// TestTouch_DoesNotExtendAbsoluteCap is the regression test for the
// refresh-the-wrong-clock bug: a session that is used continuously
// must survive well past the idle window and still die at the
// absolute cap.
func TestTouch_DoesNotExtendAbsoluteCap(t *testing.T) {
	t.Parallel()

	s, sess, clock := authenticatedSession(t, testIdleTimeout)

	createdAt := sess.Values[session.CreatedAtKey]

	// Stay active: a request every half idle window, right up to
	// the absolute cap.
	step := testIdleTimeout / 2
	steps := int(testAbsoluteMaxAge/step) - 1

	for i := range steps {
		clock.Advance(step)
		s.Touch(sess)

		require.True(
			t, s.IsAuthenticated(sess),
			"active session should survive the idle window "+
				"(step %d of %d)", i+1, steps,
		)
	}

	// One more step of activity takes the session to exactly the
	// absolute cap, measured from login. Nothing that happened in
	// the loop may have moved that deadline.
	clock.Advance(step)
	s.Touch(sess)

	assert.False(
		t, s.IsAuthenticated(sess),
		"activity must not extend the absolute cap",
	)
	assert.Equal(
		t, createdAt, sess.Values[session.CreatedAtKey],
		"Touch must never rewrite the absolute-clock anchor",
	)
}

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

	s, sess, clock := authenticatedSession(t, testIdleTimeout)

	// Halfway through the window, activity happens.
	clock.Advance(testIdleTimeout / 2)
	assert.True(
		t, s.Touch(sess),
		"Touch should refresh once past the lazy-refresh threshold",
	)

	// Past the original deadline, but inside the refreshed one.
	clock.Advance(testIdleTimeout - time.Second)
	assert.True(
		t, s.IsAuthenticated(sess),
		"refreshed session should outlive the original deadline",
	)

	// And it still expires an idle window after that activity.
	clock.Advance(time.Second)
	assert.False(
		t, s.IsAuthenticated(sess),
		"refreshed session should expire one window after activity",
	)
}

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

	s, sess, clock := authenticatedSession(t, testIdleTimeout)

	before := sess.Values[session.LastSeenKey]

	// A request arriving almost immediately is not worth a cookie
	// rewrite.
	clock.Advance(time.Second)

	assert.False(
		t, s.Touch(sess),
		"Touch should not rewrite the session below the threshold",
	)
	assert.Equal(
		t, before, sess.Values[session.LastSeenKey],
		"last-seen should be unchanged below the threshold",
	)
}

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

	s, clock := testSessionWithClock(
		t, testIdleTimeout, newFakeClock(),
	)

	req := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)

	sess, err := s.Get(req)
	require.NoError(t, err)

	clock.Advance(testIdleTimeout / 2)

	assert.False(
		t, s.Touch(sess),
		"an unauthenticated session must not be refreshed",
	)

	_, hasLastSeen := sess.Values[session.LastSeenKey]
	assert.False(
		t, hasLastSeen,
		"Touch must not stamp an unauthenticated session",
	)
}

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

	s, sess, clock := authenticatedSession(t, testIdleTimeout)

	clock.Advance(testIdleTimeout)
	require.False(t, s.IsAuthenticated(sess))

	assert.False(
		t, s.Touch(sess),
		"an already expired session must not be refreshed",
	)
	assert.False(
		t, s.IsAuthenticated(sess),
		"Touch must not revive an expired session",
	)
}

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

	s, _ := testSessionWithClock(
		t, testIdleTimeout, newFakeClock(),
	)

	req := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)

	sess, err := s.Get(req)
	require.NoError(t, err)

	// A session from before idle expiry existed: authenticated,
	// but with no timestamps. Fail closed.
	sess.Values[session.AuthenticatedKey] = true

	assert.False(
		t, s.IsAuthenticated(sess),
		"a session with no timestamps should be rejected",
	)
}

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

	s, sess, _ := authenticatedSession(t, testIdleTimeout)

	delete(sess.Values, session.LastSeenKey)

	assert.False(
		t, s.IsAuthenticated(sess),
		"a session with no idle anchor should be rejected",
	)
}

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

	s, sess, clock := authenticatedSession(t, 0)

	// Idle expiry is off, so an untouched session survives an
	// arbitrary idle stretch.
	clock.Advance(testAbsoluteMaxAge - time.Second)
	assert.True(
		t, s.IsAuthenticated(sess),
		"idle expiry should be disabled by a non-positive timeout",
	)

	assert.False(
		t, s.Touch(sess),
		"Touch should be a no-op when idle expiry is disabled",
	)

	// The absolute cap still ends it.
	clock.Advance(time.Second)
	assert.False(
		t, s.IsAuthenticated(sess),
		"the absolute cap must still apply with idle expiry off",
	)
}

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

	s, sess, _ := authenticatedSession(t, testIdleTimeout)

	s.ClearUser(sess)

	_, hasCreatedAt := sess.Values[session.CreatedAtKey]
	assert.False(t, hasCreatedAt, "CreatedAtKey should be removed")

	_, hasLastSeen := sess.Values[session.LastSeenKey]
	assert.False(t, hasLastSeen, "LastSeenKey should be removed")
}

// --- Edge Cases ---

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

	s := testSession(t)

	req := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)

	sess, err := s.Get(req)
	require.NoError(t, err)

	s.SetUser(sess, "user-1", "alice")
	assert.True(t, s.IsAuthenticated(sess))

	// Overwrite with a different user
	s.SetUser(sess, "user-2", "bob")

	userID, ok := s.GetUserID(sess)
	assert.True(t, ok)
	assert.Equal(t, "user-2", userID)

	username, ok := s.GetUsername(sess)
	assert.True(t, ok)
	assert.Equal(t, "bob", username)
}

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

	s := testSession(t)

	// Create a session
	req1 := httptest.NewRequestWithContext(
		context.Background(), http.MethodGet, "/", nil)
	w1 := httptest.NewRecorder()

	sess, err := s.Get(req1)
	require.NoError(t, err)
	s.SetUser(sess, "user-123", "alice")
	require.NoError(t, s.Save(req1, w1, sess))

	cookies := w1.Result().Cookies()
	require.NotEmpty(t, cookies)

	// Destroy and save
	req2 := httptest.NewRequestWithContext(
		context.Background(),
		http.MethodGet, "/logout", nil,
	)

	for _, c := range cookies {
		req2.AddCookie(c)
	}

	w2 := httptest.NewRecorder()

	sess2, err := s.Get(req2)
	require.NoError(t, err)
	s.Destroy(sess2)
	require.NoError(t, s.Save(req2, w2, sess2))

	// The cookie should have MaxAge = -1 (browser should delete)
	responseCookies := w2.Result().Cookies()

	var sessionCookie *http.Cookie

	for _, c := range responseCookies {
		if c.Name == session.SessionName {
			sessionCookie = c

			break
		}
	}

	require.NotNil(
		t, sessionCookie,
		"should have a session cookie in response",
	)
	assert.Negative(
		t, sessionCookie.MaxAge,
		"destroyed session cookie should have negative MaxAge",
	)
}