scrabble-game/backend/internal/lobby/matchmaker_test.go

package lobby

import (
	"context"
	"errors"
	"slices"
	"testing"
	"time"

	"github.com/google/uuid"
	"go.uber.org/zap"

	"scrabble/backend/internal/engine"
	"scrabble/backend/internal/game"
	"scrabble/backend/internal/notify"
)

// stubMatcher is a fake GameMatcher: it returns canned games and records the calls the
// matchmaker makes, so the unit tests cover delegation, the opponent_joined emit and
// the wait-window math without a database. The DB-backed open/join/substitute logic is
// covered by the integration suite.
type stubMatcher struct {
	openGame     game.Game
	openJoined   bool
	openErr      error
	openCalls    int
	lastDeadline time.Time

	expired []game.OpenGame

	attachGame    game.Game
	attached      bool
	attachErr     error
	attachedGames []uuid.UUID

	createGame   game.Game
	createErr    error
	createCalls  int
	createParams game.CreateParams
}

func (s *stubMatcher) OpenOrJoin(_ context.Context, _ uuid.UUID, _ game.CreateParams, deadline time.Time) (game.Game, bool, error) {
	s.openCalls++
	s.lastDeadline = deadline
	return s.openGame, s.openJoined, s.openErr
}

func (s *stubMatcher) AttachRobot(_ context.Context, gameID, _ uuid.UUID, _ string) (game.Game, bool, error) {
	if s.attachErr != nil {
		return game.Game{}, false, s.attachErr
	}
	if s.attached {
		s.attachedGames = append(s.attachedGames, gameID)
	}
	return s.attachGame, s.attached, nil
}

func (s *stubMatcher) ExpiredOpen(_ context.Context, _ time.Time) ([]game.OpenGame, error) {
	return s.expired, nil
}

func (s *stubMatcher) InitialState(_ context.Context, _, _ uuid.UUID) (notify.PlayerState, error) {
	return notify.PlayerState{}, nil
}

func (s *stubMatcher) Create(_ context.Context, params game.CreateParams) (game.Game, error) {
	s.createCalls++
	s.createParams = params
	return s.createGame, s.createErr
}

// fakeRobots is a RobotProvider returning a fixed robot id, or an error to model an
// empty pool. It records the variant of the last substitution request.
type fakeRobots struct {
	id          uuid.UUID
	err         error
	lastVariant engine.Variant
}

func (f *fakeRobots) Pick(variant engine.Variant) (uuid.UUID, error) {
	f.lastVariant = variant
	if f.err != nil {
		return uuid.Nil, f.err
	}
	return f.id, nil
}

func (f *fakeRobots) PickNamed(variant engine.Variant) (uuid.UUID, string, error) {
	id, err := f.Pick(variant)
	return id, "Robot", err
}

// capturePub records every published intent.
type capturePub struct{ intents []notify.Intent }

func (c *capturePub) Publish(intents ...notify.Intent) { c.intents = append(c.intents, intents...) }

// twoSeatGame is a two-player game seating starter at seat 0 and opponent at seat 1
// (uuid.Nil for a still-empty opponent seat).
func twoSeatGame(starter, opponent uuid.UUID) game.Game {
	return game.Game{
		ID:      uuid.New(),
		Variant: engine.VariantEnglish,
		Seats: []game.Seat{
			{Seat: 0, AccountID: starter},
			{Seat: 1, AccountID: opponent},
		},
	}
}

func TestEnqueueOpensGameWithoutOpponent(t *testing.T) {
	starter := uuid.New()
	m := &stubMatcher{openGame: twoSeatGame(starter, uuid.Nil)}
	pub := &capturePub{}
	mm := NewMatchmaker(m, &fakeRobots{id: uuid.New()}, time.Minute, time.Minute, zap.NewNop())
	mm.SetNotifier(pub)

	res, err := mm.Enqueue(context.Background(), starter, engine.VariantEnglish, true)
	if err != nil {
		t.Fatalf("enqueue: %v", err)
	}
	if res.Matched {
		t.Error("opening a game must report Matched=false")
	}
	if m.openCalls != 1 {
		t.Errorf("OpenOrJoin calls = %d, want 1", m.openCalls)
	}
	if len(pub.intents) != 0 {
		t.Errorf("opening a game must not emit opponent_joined; got %d intents", len(pub.intents))
	}
}

func TestEnqueueJoinEmitsOpponentJoinedToStarter(t *testing.T) {
	starter, joiner := uuid.New(), uuid.New()
	m := &stubMatcher{openGame: twoSeatGame(starter, joiner), openJoined: true}
	pub := &capturePub{}
	mm := NewMatchmaker(m, &fakeRobots{id: uuid.New()}, time.Minute, time.Minute, zap.NewNop())
	mm.SetNotifier(pub)

	res, err := mm.Enqueue(context.Background(), joiner, engine.VariantEnglish, true)
	if err != nil {
		t.Fatalf("enqueue: %v", err)
	}
	if !res.Matched {
		t.Error("joining a waiting game must report Matched=true")
	}
	if len(pub.intents) != 1 {
		t.Fatalf("joining must emit one opponent_joined; got %d", len(pub.intents))
	}
	if got := pub.intents[0]; got.Kind != notify.KindOpponentJoined || got.UserID != starter {
		t.Errorf("opponent_joined = (kind %q, user %s), want (%q, starter %s)", got.Kind, got.UserID, notify.KindOpponentJoined, starter)
	}
}

func TestStartVsAISeatsRobotAndFlagsGame(t *testing.T) {
	human, robotID := uuid.New(), uuid.New()
	m := &stubMatcher{createGame: twoSeatGame(human, robotID)}
	robots := &fakeRobots{id: robotID}
	mm := NewMatchmaker(m, robots, time.Minute, time.Minute, zap.NewNop())

	res, err := mm.StartVsAI(context.Background(), human, engine.VariantRussianScrabble, false)
	if err != nil {
		t.Fatalf("start vs AI: %v", err)
	}
	if !res.Matched {
		t.Error("an AI game starts already matched (Matched=true)")
	}
	// The AI path creates a seated active game and never enters the open pool.
	if m.createCalls != 1 || m.openCalls != 0 {
		t.Errorf("calls: create=%d open=%d, want create=1 open=0", m.createCalls, m.openCalls)
	}
	if robots.lastVariant != engine.VariantRussianScrabble {
		t.Errorf("robot picked for variant %v, want RussianScrabble", robots.lastVariant)
	}
	if !m.createParams.VsAI {
		t.Error("AI game create params must set VsAI")
	}
	if len(m.createParams.Seats) != 2 ||
		!slices.Contains(m.createParams.Seats, human) || !slices.Contains(m.createParams.Seats, robotID) {
		t.Errorf("AI game seats %v, want exactly the human %s and the robot %s", m.createParams.Seats, human, robotID)
	}
}

func TestStartVsAINoRobotLeavesNoGame(t *testing.T) {
	poolErr := errors.New("pool empty")
	m := &stubMatcher{}
	mm := NewMatchmaker(m, &fakeRobots{err: poolErr}, time.Minute, time.Minute, zap.NewNop())

	if _, err := mm.StartVsAI(context.Background(), uuid.New(), engine.VariantEnglish, true); !errors.Is(err, poolErr) {
		t.Fatalf("start vs AI with empty pool = %v, want poolErr", err)
	}
	if m.createCalls != 0 {
		t.Errorf("no robot available must not create a game; create calls = %d", m.createCalls)
	}
}

func TestEnqueueDeadlineWithinWindow(t *testing.T) {
	base := time.Now()
	m := &stubMatcher{openGame: twoSeatGame(uuid.New(), uuid.Nil)}
	mm := NewMatchmaker(m, &fakeRobots{id: uuid.New()}, 90*time.Second, 90*time.Second, zap.NewNop())
	mm.clock = func() time.Time { return base }

	if _, err := mm.Enqueue(context.Background(), uuid.New(), engine.VariantEnglish, true); err != nil {
		t.Fatalf("enqueue: %v", err)
	}
	lo, hi := base.Add(90*time.Second), base.Add(180*time.Second)
	if m.lastDeadline.Before(lo) || !m.lastDeadline.Before(hi) {
		t.Errorf("deadline %s not in [%s, %s)", m.lastDeadline, lo, hi)
	}
}

func TestReapSubstitutesRobotAndEmits(t *testing.T) {
	human, robotID := uuid.New(), uuid.New()
	og := game.OpenGame{ID: uuid.New(), Variant: engine.VariantRussianScrabble}
	m := &stubMatcher{
		expired:    []game.OpenGame{og},
		attachGame: twoSeatGame(human, robotID),
		attached:   true,
	}
	robots := &fakeRobots{id: robotID}
	pub := &capturePub{}
	mm := NewMatchmaker(m, robots, time.Minute, time.Minute, zap.NewNop())
	mm.SetNotifier(pub)

	mm.Reap(context.Background(), time.Now())

	if robots.lastVariant != engine.VariantRussianScrabble {
		t.Errorf("robot picked for %v, want the open game's variant", robots.lastVariant)
	}
	if len(m.attachedGames) != 1 || m.attachedGames[0] != og.ID {
		t.Errorf("attached games = %v, want [%s]", m.attachedGames, og.ID)
	}
	if len(pub.intents) != 1 || pub.intents[0].Kind != notify.KindOpponentJoined || pub.intents[0].UserID != human {
		t.Errorf("reap must emit opponent_joined to the human starter; got %+v", pub.intents)
	}
}

func TestReapDefersWithoutRobot(t *testing.T) {
	m := &stubMatcher{expired: []game.OpenGame{{ID: uuid.New(), Variant: engine.VariantEnglish}}}
	pub := &capturePub{}
	mm := NewMatchmaker(m, &fakeRobots{err: errors.New("empty pool")}, time.Minute, time.Minute, zap.NewNop())
	mm.SetNotifier(pub)

	mm.Reap(context.Background(), time.Now())

	if len(m.attachedGames) != 0 {
		t.Errorf("no robot available: must not attach; attached %v", m.attachedGames)
	}
	if len(pub.intents) != 0 {
		t.Errorf("no robot available: must not emit; got %d intents", len(pub.intents))
	}
}

func TestReapSkipsWhenHumanJoinedFirst(t *testing.T) {
	m := &stubMatcher{
		expired:  []game.OpenGame{{ID: uuid.New(), Variant: engine.VariantEnglish}},
		attached: false, // AttachRobot reports the game already filled by a human
	}
	pub := &capturePub{}
	mm := NewMatchmaker(m, &fakeRobots{id: uuid.New()}, time.Minute, time.Minute, zap.NewNop())
	mm.SetNotifier(pub)

	mm.Reap(context.Background(), time.Now())

	if len(pub.intents) != 0 {
		t.Errorf("a human-filled game must not emit opponent_joined; got %d", len(pub.intents))
	}
}