feat: add user submission history page

Allow users to view their own past submissions (code, size, status,
timestamp) for each game. Adds API endpoint, backend handler, SQL query,
and frontend page with expandable code display.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 155 insertions, 11 deletions

diff --git a/backend/api/handler_test.go b/backend/api/handler_test.go
index 2415710..a28d605 100644
--- a/backend/api/handler_test.go
+++ b/backend/api/handler_test.go
@@ -16,17 +16,18 @@ import (
 // mockQuerier implements db.Querier for testing.
 type mockQuerier struct {
 	db.Querier
-	getGameByIDFunc           func(ctx context.Context, gameID int32) (db.GetGameByIDRow, error)
-	listMainPlayersFunc       func(ctx context.Context, gameIDs []int32) ([]db.ListMainPlayersRow, error)
-	listPublicGamesFunc       func(ctx context.Context) ([]db.ListPublicGamesRow, error)
-	deleteSessionFunc         func(ctx context.Context, sessionID string) error
-	getLatestStateFunc        func(ctx context.Context, arg db.GetLatestStateParams) (db.GetLatestStateRow, error)
-	updateCodeFunc            func(ctx context.Context, arg db.UpdateCodeParams) error
-	getRankingFunc            func(ctx context.Context, gameID int32) ([]db.GetRankingRow, error)
-	getLatestStatesFunc       func(ctx context.Context, gameID int32) ([]db.GetLatestStatesOfMainPlayersRow, error)
-	getTournamentByIDFunc     func(ctx context.Context, tournamentID int32) (db.Tournament, error)
-	listTournamentEntriesFunc func(ctx context.Context, tournamentID int32) ([]db.ListTournamentEntriesRow, error)
-	listTournamentMatchesFunc func(ctx context.Context, tournamentID int32) ([]db.TournamentMatch, error)
+	getGameByIDFunc                     func(ctx context.Context, gameID int32) (db.GetGameByIDRow, error)
+	listMainPlayersFunc                 func(ctx context.Context, gameIDs []int32) ([]db.ListMainPlayersRow, error)
+	listPublicGamesFunc                 func(ctx context.Context) ([]db.ListPublicGamesRow, error)
+	deleteSessionFunc                   func(ctx context.Context, sessionID string) error
+	getLatestStateFunc                  func(ctx context.Context, arg db.GetLatestStateParams) (db.GetLatestStateRow, error)
+	updateCodeFunc                      func(ctx context.Context, arg db.UpdateCodeParams) error
+	getRankingFunc                      func(ctx context.Context, gameID int32) ([]db.GetRankingRow, error)
+	getLatestStatesFunc                 func(ctx context.Context, gameID int32) ([]db.GetLatestStatesOfMainPlayersRow, error)
+	getTournamentByIDFunc               func(ctx context.Context, tournamentID int32) (db.Tournament, error)
+	listTournamentEntriesFunc           func(ctx context.Context, tournamentID int32) ([]db.ListTournamentEntriesRow, error)
+	listTournamentMatchesFunc           func(ctx context.Context, tournamentID int32) ([]db.TournamentMatch, error)
+	getSubmissionsByGameIDAndUserIDFunc func(ctx context.Context, arg db.GetSubmissionsByGameIDAndUserIDParams) ([]db.Submission, error)
 }
 
 func (m *mockQuerier) GetGameByID(ctx context.Context, gameID int32) (db.GetGameByIDRow, error) {
@@ -85,6 +86,13 @@ func (m *mockQuerier) GetLatestStatesOfMainPlayers(ctx context.Context, gameID i
 	return nil, nil
 }
 
+func (m *mockQuerier) GetSubmissionsByGameIDAndUserID(ctx context.Context, arg db.GetSubmissionsByGameIDAndUserIDParams) ([]db.Submission, error) {
+	if m.getSubmissionsByGameIDAndUserIDFunc != nil {
+		return m.getSubmissionsByGameIDAndUserIDFunc(ctx, arg)
+	}
+	return nil, nil
+}
+
 func (m *mockQuerier) GetTournamentByID(ctx context.Context, tournamentID int32) (db.Tournament, error) {
 	if m.getTournamentByIDFunc != nil {
 		return m.getTournamentByIDFunc(ctx, tournamentID)
@@ -137,6 +145,142 @@ func (m *mockAuthenticator) Login(_ context.Context, _, _ string) (int, error) {
 	return m.loginResult, m.loginErr
 }
 
+func TestGetGamePlaySubmissions_GameNotFound(t *testing.T) {
+	h := Handler{
+		q:    &mockQuerier{},
+		txm:  &mockTxManager{},
+		hub:  &mockGameHub{},
+		auth: &mockAuthenticator{},
+		conf: &config.Config{},
+	}
+	user := &db.User{UserID: 1}
+	resp, err := h.GetGamePlaySubmissions(context.Background(), GetGamePlaySubmissionsRequestObject{
+		GameID: 999,
+	}, user)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if _, ok := resp.(GetGamePlaySubmissions404JSONResponse); !ok {
+		t.Errorf("expected 404 response, got %T", resp)
+	}
+}
+
+func TestGetGamePlaySubmissions_Empty(t *testing.T) {
+	h := Handler{
+		q: &mockQuerier{
+			getGameByIDFunc: func(_ context.Context, _ int32) (db.GetGameByIDRow, error) {
+				return db.GetGameByIDRow{
+					GameID:   1,
+					Language: "php",
+				}, nil
+			},
+		},
+		txm:  &mockTxManager{},
+		hub:  &mockGameHub{},
+		auth: &mockAuthenticator{},
+		conf: &config.Config{},
+	}
+	user := &db.User{UserID: 1}
+	resp, err := h.GetGamePlaySubmissions(context.Background(), GetGamePlaySubmissionsRequestObject{
+		GameID: 1,
+	}, user)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	okResp, ok := resp.(GetGamePlaySubmissions200JSONResponse)
+	if !ok {
+		t.Fatalf("expected 200 response, got %T", resp)
+	}
+	if len(okResp.Submissions) != 0 {
+		t.Errorf("expected 0 submissions, got %d", len(okResp.Submissions))
+	}
+}
+
+func TestGetGamePlaySubmissions_WithSubmissions(t *testing.T) {
+	now := time.Now()
+	h := Handler{
+		q: &mockQuerier{
+			getGameByIDFunc: func(_ context.Context, _ int32) (db.GetGameByIDRow, error) {
+				return db.GetGameByIDRow{
+					GameID:   1,
+					Language: "php",
+				}, nil
+			},
+			getSubmissionsByGameIDAndUserIDFunc: func(_ context.Context, arg db.GetSubmissionsByGameIDAndUserIDParams) ([]db.Submission, error) {
+				if arg.GameID != 1 || arg.UserID != 42 {
+					t.Errorf("unexpected query params: game_id=%d, user_id=%d", arg.GameID, arg.UserID)
+				}
+				return []db.Submission{
+					{
+						SubmissionID: 10,
+						GameID:       1,
+						UserID:       42,
+						Code:         "<?php echo 1;",
+						CodeSize:     14,
+						Status:       "success",
+						CreatedAt:    pgtype.Timestamp{Time: now, Valid: true},
+					},
+					{
+						SubmissionID: 9,
+						GameID:       1,
+						UserID:       42,
+						Code:         "<?php echo 'hello';",
+						CodeSize:     20,
+						Status:       "wrong_answer",
+						CreatedAt:    pgtype.Timestamp{Time: now.Add(-5 * time.Minute), Valid: true},
+					},
+				}, nil
+			},
+		},
+		txm:  &mockTxManager{},
+		hub:  &mockGameHub{},
+		auth: &mockAuthenticator{},
+		conf: &config.Config{},
+	}
+	user := &db.User{UserID: 42}
+	resp, err := h.GetGamePlaySubmissions(context.Background(), GetGamePlaySubmissionsRequestObject{
+		GameID: 1,
+	}, user)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	okResp, ok := resp.(GetGamePlaySubmissions200JSONResponse)
+	if !ok {
+		t.Fatalf("expected 200 response, got %T", resp)
+	}
+	if len(okResp.Submissions) != 2 {
+		t.Fatalf("expected 2 submissions, got %d", len(okResp.Submissions))
+	}
+
+	s0 := okResp.Submissions[0]
+	if s0.SubmissionID != 10 {
+		t.Errorf("expected submission_id 10, got %d", s0.SubmissionID)
+	}
+	if s0.GameID != 1 {
+		t.Errorf("expected game_id 1, got %d", s0.GameID)
+	}
+	if s0.Code != "<?php echo 1;" {
+		t.Errorf("expected code '<?php echo 1;', got %q", s0.Code)
+	}
+	if s0.CodeSize != 14 {
+		t.Errorf("expected code_size 14, got %d", s0.CodeSize)
+	}
+	if s0.Status != Success {
+		t.Errorf("expected status 'success', got %q", s0.Status)
+	}
+	if s0.CreatedAt != now.Unix() {
+		t.Errorf("expected created_at %d, got %d", now.Unix(), s0.CreatedAt)
+	}
+
+	s1 := okResp.Submissions[1]
+	if s1.SubmissionID != 9 {
+		t.Errorf("expected submission_id 9, got %d", s1.SubmissionID)
+	}
+	if s1.Status != WrongAnswer {
+		t.Errorf("expected status 'wrong_answer', got %q", s1.Status)
+	}
+}
+
 func TestPostGamePlaySubmit_GameNotFound(t *testing.T) {
 	h := Handler{
 		q:    &mockQuerier{},