package leaderboard

// service_test.go contains backend tests for package behavior, error paths, and regressions.

import (
	"context"
	"encoding/json"
	"errors"
	"strings"
	"testing"
	"time"

	domain "knowfoolery/backend/services/leaderboard-service/internal/domain/leaderboard"
	sharedtypes "knowfoolery/backend/shared/domain/types"
)

type fakeRepo struct {
	entries    []*domain.LeaderboardEntry
	stats      map[string]*domain.PlayerStats
	ingestErr  error
	topErr     error
	statsErr   error
	rankErr    error
	historyErr error
	globalErr  error
}

// newFakeRepo creates in-memory test doubles and deterministic fixtures.
func newFakeRepo() *fakeRepo {
	return &fakeRepo{
		entries: make([]*domain.LeaderboardEntry, 0),
		stats:   map[string]*domain.PlayerStats{},
	}
}

// EnsureSchema initializes schema state required before repository operations.
func (r *fakeRepo) EnsureSchema(ctx context.Context) error { return nil }

// IngestEntry supports ingest entry test setup and assertions.
func (r *fakeRepo) IngestEntry(
	ctx context.Context,
	entry *domain.LeaderboardEntry,
) (*domain.LeaderboardEntry, bool, error) {
	if r.ingestErr != nil {
		return nil, false, r.ingestErr
	}
	for _, e := range r.entries {
		if e.SessionID == entry.SessionID {
			return e, true, nil
		}
	}
	cp := *entry
	cp.ID = "id-" + entry.SessionID
	cp.CreatedAt = time.Now().UTC()
	r.entries = append(r.entries, &cp)

	stats := r.stats[entry.PlayerID]
	if stats == nil {
		best := entry.DurationSeconds
		stats = &domain.PlayerStats{
			PlayerID:        entry.PlayerID,
			PlayerName:      entry.PlayerName,
			GamesPlayed:     1,
			GamesCompleted:  0,
			TotalScore:      int64(entry.Score),
			BestScore:       entry.Score,
			AvgScore:        float64(entry.Score),
			AvgSuccessRate:  entry.SuccessRate,
			TotalQuestions:  int64(entry.QuestionsAsked),
			TotalCorrect:    int64(entry.QuestionsCorrect),
			BestDurationSec: &best,
		}
		if entry.CompletionType == domain.CompletionCompleted {
			stats.GamesCompleted = 1
		}
		r.stats[entry.PlayerID] = stats
		return &cp, false, nil
	}

	stats.GamesPlayed++
	stats.TotalScore += int64(entry.Score)
	stats.TotalQuestions += int64(entry.QuestionsAsked)
	stats.TotalCorrect += int64(entry.QuestionsCorrect)
	stats.AvgScore = float64(stats.TotalScore) / float64(stats.GamesPlayed)
	if stats.TotalQuestions > 0 {
		stats.AvgSuccessRate = float64(stats.TotalCorrect) * 100 / float64(stats.TotalQuestions)
	}
	if entry.Score > stats.BestScore {
		stats.BestScore = entry.Score
		best := entry.DurationSeconds
		stats.BestDurationSec = &best
	}
	return &cp, false, nil
}

// ListTop returns filtered collections from the in-memory repository.
func (r *fakeRepo) ListTop(
	ctx context.Context,
	filter domain.TopFilter,
	limit int,
) ([]*domain.LeaderboardEntry, error) {
	if r.topErr != nil {
		return nil, r.topErr
	}
	if len(r.entries) < limit {
		limit = len(r.entries)
	}
	out := make([]*domain.LeaderboardEntry, 0, limit)
	for i := 0; i < limit; i++ {
		out = append(out, r.entries[i])
	}
	return out, nil
}

// GetPlayerStats retrieves data from the in-memory repository.
func (r *fakeRepo) GetPlayerStats(ctx context.Context, playerID string) (*domain.PlayerStats, error) {
	if r.statsErr != nil {
		return nil, r.statsErr
	}
	stats := r.stats[playerID]
	if stats == nil {
		return nil, domain.ErrPlayerNotFound
	}
	cp := *stats
	return &cp, nil
}

// GetPlayerRank retrieves data from the in-memory repository.
func (r *fakeRepo) GetPlayerRank(ctx context.Context, playerID string) (int64, error) {
	if r.rankErr != nil {
		return 0, r.rankErr
	}
	if _, ok := r.stats[playerID]; !ok {
		return 0, domain.ErrPlayerNotFound
	}
	return 1, nil
}

// ListPlayerHistory returns filtered collections from the in-memory repository.
func (r *fakeRepo) ListPlayerHistory(
	ctx context.Context,
	playerID string,
	pagination sharedtypes.Pagination,
) ([]*domain.LeaderboardEntry, int64, error) {
	if r.historyErr != nil {
		return nil, 0, r.historyErr
	}
	out := make([]*domain.LeaderboardEntry, 0)
	for _, entry := range r.entries {
		if entry.PlayerID == playerID {
			out = append(out, entry)
		}
	}
	return out, int64(len(out)), nil
}

// GetGlobalStats retrieves data from the in-memory repository.
func (r *fakeRepo) GetGlobalStats(ctx context.Context, filter domain.TopFilter) (*domain.GlobalStats, error) {
	if r.globalErr != nil {
		return nil, r.globalErr
	}
	return &domain.GlobalStats{TotalGames: int64(len(r.entries)), UpdatedAt: time.Now().UTC()}, nil
}

type fakeState struct {
	data      map[string]string
	setErr    error
	deleteErr error
}

// newFakeState creates in-memory test doubles and deterministic fixtures.
func newFakeState() *fakeState {
	return &fakeState{data: map[string]string{}}
}

// Get retrieves data from the in-memory repository.
func (s *fakeState) Get(ctx context.Context, key string) (string, bool) {
	v, ok := s.data[key]
	return v, ok
}

// Set stores ephemeral state in the fake cache or state store.
func (s *fakeState) Set(ctx context.Context, key, value string, ttl time.Duration) error {
	if s.setErr != nil {
		return s.setErr
	}
	s.data[key] = value
	return nil
}

// Delete removes ephemeral state from the fake cache or state store.
func (s *fakeState) Delete(ctx context.Context, keys ...string) error {
	if s.deleteErr != nil {
		return s.deleteErr
	}
	for _, key := range keys {
		delete(s.data, key)
	}
	return nil
}

// TestUpdateScoreIdempotent ensures update score idempotent behavior is handled correctly.
func TestUpdateScoreIdempotent(t *testing.T) {
	repo := newFakeRepo()
	state := newFakeState()
	svc := NewService(repo, state, Config{})

	in := UpdateScoreInput{
		SessionID:        "s1",
		PlayerID:         "u1",
		PlayerName:       "Alice",
		TotalScore:       8,
		QuestionsAsked:   10,
		QuestionsCorrect: 7,
		HintsUsed:        1,
		DurationSeconds:  100,
		CompletedAt:      time.Now().UTC(),
		CompletionType:   "completed",
	}
	one, err := svc.UpdateScore(context.Background(), in)
	if err != nil {
		t.Fatalf("UpdateScore first failed: %v", err)
	}
	two, err := svc.UpdateScore(context.Background(), in)
	if err != nil {
		t.Fatalf("UpdateScore second failed: %v", err)
	}
	if one.ID != two.ID {
		t.Fatalf("idempotency failed: %s != %s", one.ID, two.ID)
	}
}

// TestUpdateScoreValidatesInput ensures update score validates input behavior is handled correctly.
func TestUpdateScoreValidatesInput(t *testing.T) {
	svc := NewService(newFakeRepo(), newFakeState(), Config{})
	_, err := svc.UpdateScore(context.Background(), UpdateScoreInput{
		SessionID:        "s1",
		PlayerID:         "u1",
		PlayerName:       "A",
		TotalScore:       1,
		QuestionsAsked:   1,
		QuestionsCorrect: 2,
		DurationSeconds:  1,
		CompletedAt:      time.Now().UTC(),
		CompletionType:   "completed",
	})
	if !errors.Is(err, domain.ErrInvalidInput) {
		t.Fatalf("expected ErrInvalidInput, got %v", err)
	}
}

// TestGetPlayerRanking ensures get player ranking behavior is handled correctly.
func TestGetPlayerRanking(t *testing.T) {
	repo := newFakeRepo()
	state := newFakeState()
	svc := NewService(repo, state, Config{})
	_, _ = svc.UpdateScore(context.Background(), UpdateScoreInput{
		SessionID:        "s1",
		PlayerID:         "u1",
		PlayerName:       "Alice",
		TotalScore:       3,
		QuestionsAsked:   4,
		QuestionsCorrect: 2,
		DurationSeconds:  50,
		CompletedAt:      time.Now().UTC(),
		CompletionType:   "completed",
	})

	result, err := svc.GetPlayerRanking(context.Background(), GetPlayerRankingInput{
		PlayerID: "u1",
		Pagination: sharedtypes.Pagination{
			Page:     1,
			PageSize: 10,
		},
	})
	if err != nil {
		t.Fatalf("GetPlayerRanking failed: %v", err)
	}
	if result.Rank != 1 {
		t.Fatalf("rank=%d want=1", result.Rank)
	}
	if len(result.History) != 1 {
		t.Fatalf("history len=%d want=1", len(result.History))
	}
}

// TestUpdateScoreValidationAndErrorPaths ensures update score validation and error paths behavior is handled correctly.
func TestUpdateScoreValidationAndErrorPaths(t *testing.T) {
	svc := NewService(newFakeRepo(), newFakeState(), Config{})
	cases := []UpdateScoreInput{
		{SessionID: "", PlayerID: "u1", CompletionType: "completed"},
		{SessionID: "s1", PlayerID: "", CompletionType: "completed"},
		{SessionID: "s1", PlayerID: "u1", TotalScore: -1, CompletionType: "completed"},
		{SessionID: "s1", PlayerID: "u1", QuestionsAsked: 1, QuestionsCorrect: 2, CompletionType: "completed"},
		{SessionID: "s1", PlayerID: "u1", CompletionType: "invalid"},
	}
	for i, in := range cases {
		_, err := svc.UpdateScore(context.Background(), in)
		if !errors.Is(err, domain.ErrInvalidInput) {
			t.Fatalf("case %d: expected invalid input, got %v", i, err)
		}
	}

	repo := newFakeRepo()
	repo.ingestErr = errors.New("ingest boom")
	svc = NewService(repo, newFakeState(), Config{})
	_, err := svc.UpdateScore(context.Background(), UpdateScoreInput{
		SessionID: "s1", PlayerID: "u1", PlayerName: "Alice", CompletionType: "completed",
	})
	if err == nil || !strings.Contains(err.Error(), "ingest boom") {
		t.Fatalf("expected ingest error, got %v", err)
	}
}

// TestTopAndStatsCachePaths ensures top and stats cache paths behavior is handled correctly.
func TestTopAndStatsCachePaths(t *testing.T) {
	repo := newFakeRepo()
	state := newFakeState()
	svc := NewService(repo, state, Config{})
	_, _ = svc.UpdateScore(context.Background(), UpdateScoreInput{
		SessionID:        "s1",
		PlayerID:         "u1",
		PlayerName:       "Alice",
		TotalScore:       8,
		QuestionsAsked:   10,
		QuestionsCorrect: 7,
		DurationSeconds:  100,
		CompletedAt:      time.Now().UTC(),
		CompletionType:   "completed",
	})

	top, err := svc.GetTop10(context.Background(), GetTopInput{Window: domain.Window7d})
	if err != nil {
		t.Fatalf("GetTop10 failed: %v", err)
	}
	if len(top.Items) == 0 || top.Items[0].Rank != 1 {
		t.Fatalf("expected ranked top item")
	}

	cacheKey := "lb:top10:v1::7d"
	payload, _ := json.Marshal(Top10Result{
		Items: []RankedEntry{{Rank: 1, Entry: domain.LeaderboardEntry{SessionID: "cached"}}},
	})
	state.data[cacheKey] = string(payload)
	cached, err := svc.GetTop10(context.Background(), GetTopInput{Window: domain.Window7d})
	if err != nil {
		t.Fatalf("GetTop10 cached failed: %v", err)
	}
	if cached.Items[0].Entry.SessionID != "cached" {
		t.Fatalf("expected cached top payload")
	}

	stats, err := svc.GetGlobalStats(context.Background(), GetStatsInput{Window: domain.WindowAll})
	if err != nil {
		t.Fatalf("GetGlobalStats failed: %v", err)
	}
	if stats.TotalGames <= 0 {
		t.Fatalf("expected total games > 0")
	}

	state.data["lb:stats:global:v1::all"] = `{"TotalGames":42}`
	cachedStats, err := svc.GetGlobalStats(context.Background(), GetStatsInput{Window: domain.WindowAll})
	if err != nil {
		t.Fatalf("cached stats failed: %v", err)
	}
	if cachedStats.TotalGames != 42 {
		t.Fatalf("expected cached total games")
	}
}

// TestRankingValidationAndErrorPaths ensures ranking validation and error paths behavior is handled correctly.
func TestRankingValidationAndErrorPaths(t *testing.T) {
	repo := newFakeRepo()
	state := newFakeState()
	svc := NewService(repo, state, Config{})

	_, err := svc.GetPlayerRanking(context.Background(), GetPlayerRankingInput{PlayerID: ""})
	if !errors.Is(err, domain.ErrInvalidInput) {
		t.Fatalf("expected invalid input for empty player id, got %v", err)
	}

	_, _ = svc.UpdateScore(context.Background(), UpdateScoreInput{
		SessionID:        "s1",
		PlayerID:         "u1",
		PlayerName:       "Alice",
		TotalScore:       3,
		QuestionsAsked:   4,
		QuestionsCorrect: 2,
		DurationSeconds:  50,
		CompletedAt:      time.Now().UTC(),
		CompletionType:   "completed",
	})

	state.data["lb:rank:u1"] = "not-a-number"
	_, err = svc.GetPlayerRanking(context.Background(), GetPlayerRankingInput{
		PlayerID: "u1",
		Pagination: sharedtypes.Pagination{
			Page:     1,
			PageSize: 1,
		},
	})
	if err != nil {
		t.Fatalf("expected fallback to repo rank when cache parse fails: %v", err)
	}

	repo.statsErr = errors.New("stats boom")
	_, err = svc.GetPlayerRanking(context.Background(), GetPlayerRankingInput{PlayerID: "u1"})
	if err == nil || !strings.Contains(err.Error(), "stats boom") {
		t.Fatalf("expected stats error, got %v", err)
	}
	repo.statsErr = nil
	repo.rankErr = errors.New("rank boom")
	state.data["lb:rank:u1"] = "0"
	_, err = svc.GetPlayerRanking(context.Background(), GetPlayerRankingInput{PlayerID: "u1"})
	if err == nil || !strings.Contains(err.Error(), "rank boom") {
		t.Fatalf("expected rank error, got %v", err)
	}
	repo.rankErr = nil
	repo.historyErr = errors.New("history boom")
	_, err = svc.GetPlayerRanking(context.Background(), GetPlayerRankingInput{PlayerID: "u1"})
	if err == nil || !strings.Contains(err.Error(), "history boom") {
		t.Fatalf("expected history error, got %v", err)
	}
}

// TestGlobalStatsAndTopErrors ensures global stats and top errors behavior is handled correctly.
func TestGlobalStatsAndTopErrors(t *testing.T) {
	repo := newFakeRepo()
	repo.topErr = errors.New("top boom")
	svc := NewService(repo, newFakeState(), Config{})
	_, err := svc.GetTop10(context.Background(), GetTopInput{Window: domain.Window("bogus")})
	if err == nil || !strings.Contains(err.Error(), "top boom") {
		t.Fatalf("expected top error, got %v", err)
	}

	repo = newFakeRepo()
	repo.globalErr = errors.New("global boom")
	svc = NewService(repo, newFakeState(), Config{})
	_, err = svc.GetGlobalStats(context.Background(), GetStatsInput{Window: domain.Window("bogus")})
	if err == nil || !strings.Contains(err.Error(), "global boom") {
		t.Fatalf("expected global error, got %v", err)
	}
}