feat(rewards): shop, equipped looks and public looks

Add endpoints to buy items, equip looks by slot and unequip. The shop has
8 whitelisted looks: avatar borders, badges, accents and banner frames.
Ownership is a BUY ledger row; PLATFORM_ADMIN owns every catalog item
without buying. The public profile endpoint shares only the equipped looks
filtered by ownership.

src/main/java/core_service/configuration/security/JwtService.java

@@ -58,8 +58,7 @@ public class JwtService implements ProfileTicketVerifier {
             if (userId == null) {
                 return Optional.empty();
             }
-            return Optional.of(new UserPrincipal(userId, claims.get("steamId", Long.class),
-                    Role.parse(claims.get(ROLE_CLAIM) instanceof String role ? role : null)));
+            return Optional.of(new UserPrincipal(userId, claims.get("steamId", Long.class), role(claims)));
         } catch (Exception e) {
             return Optional.empty();
         }
@@ -77,6 +76,10 @@ public class JwtService implements ProfileTicketVerifier {
         }
     }
 
+    private static Role role(Claims claims) {
+        return Role.parse(claims.get(ROLE_CLAIM) instanceof String role ? role : null);
+    }
+
     private static Set<String> names(List<?> claim) {
         return claim.stream().filter(String.class::isInstance).map(String.class::cast).collect(Collectors.toSet());
     }
@@ -92,7 +95,7 @@ public class JwtService implements ProfileTicketVerifier {
             // A ticket of an Auth from before the claim has none: then the profile shows no stats.
             Set<String> profileStats = claims.get("profileStats") instanceof List<?> groups ? names(groups) : Set.of();
             Set<String> sections = claims.get("sections") instanceof List<?> shown ? names(shown) : null;
-            return Optional.of(new ProfileTicket(userId, profileStats, sections));
+            return Optional.of(new ProfileTicket(userId, role(claims), profileStats, sections));
         } catch (Exception e) {
             return Optional.empty();
         }

src/main/java/core_service/modules/rewards/api/PublicRewardController.java

@@ -0,0 +1,36 @@
+package core_service.modules.rewards.api;
+
+import core_service.modules.rewards.api.dto.PublicLooksDto;
+import core_service.modules.rewards.service.RewardService;
+import core_service.shared.api.ErrorResponse;
+import core_service.shared.security.ProfileTicket;
+import core_service.shared.security.ProfileTicketVerifier;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestHeader;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.Optional;
+
+/**
+ * Public, without login, like the public library: the profile ticket names the user and the role.
+ */
+@RestController
+@RequestMapping("/api/public/profiles")
+@RequiredArgsConstructor
+public class PublicRewardController {
+
+    private final RewardService rewardService;
+    private final ProfileTicketVerifier profileTicketVerifier;
+
+    @GetMapping("/rewards")
+    public ResponseEntity<?> getPublicLooks(@RequestHeader(value = "X-Profile-Ticket", required = false) String ticket) {
+        return (ticket == null ? Optional.<ProfileTicket>empty() : profileTicketVerifier.verifyProfileTicket(ticket))
+                .<ResponseEntity<?>>map(t -> ResponseEntity.ok(new PublicLooksDto(rewardService.publicLooks(t.userId(), t.role()))))
+                .orElseGet(() -> ResponseEntity.status(HttpStatus.UNAUTHORIZED)
+                        .body(new ErrorResponse("INVALID_TICKET", "Missing, invalid or expired profile ticket")));
+    }
+}

src/main/java/core_service/modules/rewards/api/RewardController.java

@@ -1,12 +1,22 @@
 package core_service.modules.rewards.api;
 
+import core_service.modules.rewards.api.dto.EquipRequest;
+import core_service.modules.rewards.api.dto.PurchaseRequest;
 import core_service.modules.rewards.api.dto.WalletDto;
+import core_service.modules.rewards.domain.LookSlot;
 import core_service.modules.rewards.service.RewardService;
+import core_service.shared.api.ErrorResponse;
 import core_service.shared.security.UserPrincipal;
+import jakarta.validation.Valid;
 import lombok.RequiredArgsConstructor;
+import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
 import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.PutMapping;
+import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
 
@@ -24,4 +34,29 @@ public class RewardController {
     public ResponseEntity<WalletDto> getWallet(@AuthenticationPrincipal UserPrincipal principal) {
         return ResponseEntity.ok(WalletDto.of(rewardService.wallet(principal.getIdAsLong(), principal.role())));
     }
+
+    @PostMapping("/purchases")
+    public ResponseEntity<?> buy(@AuthenticationPrincipal UserPrincipal principal, @Valid @RequestBody PurchaseRequest request) {
+        RewardService.BuyResult result = rewardService.buy(principal.getIdAsLong(), principal.role(), request.item());
+        return switch (result) {
+            case BOUGHT -> getWallet(principal);
+            case ALREADY_OWNED -> ResponseEntity.status(HttpStatus.CONFLICT)
+                    .body(new ErrorResponse("ALREADY_OWNED", "The item is already owned"));
+            case NOT_ENOUGH_POINTS -> ResponseEntity.status(HttpStatus.CONFLICT)
+                    .body(new ErrorResponse("NOT_ENOUGH_POINTS", "Not enough Pile Points"));
+        };
+    }
+
+    @PutMapping("/equipped/{slot}")
+    public ResponseEntity<?> equip(@AuthenticationPrincipal UserPrincipal principal, @PathVariable LookSlot slot,
+                                   @RequestBody EquipRequest request) {
+        RewardService.EquipResult result = rewardService.equip(principal.getIdAsLong(), principal.role(), slot, request.item());
+        return switch (result) {
+            case DONE -> getWallet(principal);
+            case NOT_OWNED -> ResponseEntity.status(HttpStatus.CONFLICT)
+                    .body(new ErrorResponse("NOT_OWNED", "The item is not owned"));
+            case WRONG_SLOT -> ResponseEntity.badRequest()
+                    .body(new ErrorResponse("WRONG_SLOT", "The item does not fit this slot"));
+        };
+    }
 }

src/main/java/core_service/modules/rewards/api/dto/EquipRequest.java

@@ -0,0 +1,8 @@
+package core_service.modules.rewards.api.dto;
+
+import core_service.modules.rewards.domain.ShopItem;
+
+/**
+ * @param item null takes the slot's look off
+ */
+public record EquipRequest(ShopItem item) {}

src/main/java/core_service/modules/rewards/api/dto/PublicLooksDto.java

@@ -0,0 +1,7 @@
+package core_service.modules.rewards.api.dto;
+
+import core_service.modules.rewards.domain.LookSlot;
+
+import java.util.Map;
+
+public record PublicLooksDto(Map<LookSlot, String> equipped) {}

src/main/java/core_service/modules/rewards/api/dto/PurchaseRequest.java

@@ -0,0 +1,6 @@
+package core_service.modules.rewards.api.dto;
+
+import core_service.modules.rewards.domain.ShopItem;
+import jakarta.validation.constraints.NotNull;
+
+public record PurchaseRequest(@NotNull ShopItem item) {}

src/main/java/core_service/modules/rewards/service/RewardService.java

@@ -7,8 +7,10 @@ import core_service.modules.rewards.domain.Looks;
 import core_service.modules.rewards.domain.RewardEntry;
 import core_service.modules.rewards.domain.RewardKind;
 import core_service.modules.rewards.domain.RewardRules;
+import core_service.modules.rewards.domain.ShopItem;
 import core_service.modules.rewards.repo.RewardFactsRepository;
 import core_service.modules.rewards.repo.RewardLedgerRepository;
+import core_service.shared.security.Public;
 import core_service.shared.security.RequiresRole;
 import core_service.shared.security.Role;
 import lombok.RequiredArgsConstructor;
@@ -64,6 +66,53 @@ public class RewardService {
                 ledger.history(userId, HISTORY_SIZE));
     }
 
+    public enum BuyResult { BOUGHT, ALREADY_OWNED, NOT_ENOUGH_POINTS }
+
+    public enum EquipResult { DONE, NOT_OWNED, WRONG_SLOT }
+
+    /**
+     * An admin owns every item, so never buys.
+     */
+    @Transactional
+    public BuyResult buy(long userId, Role role, ShopItem item) {
+        ledger.lockUser(userId);
+        if (Looks.owned(ledger.bought(userId), role).contains(item.name())) {
+            return BuyResult.ALREADY_OWNED;
+        }
+        if (ledger.balance(userId) < item.price()) {
+            return BuyResult.NOT_ENOUGH_POINTS;
+        }
+        ledger.add(userId, new RewardEntry(RewardKind.BUY, item.name(), -item.price(), Instant.now()));
+        return BuyResult.BOUGHT;
+    }
+
+    /**
+     * @param item null takes the slot's look off
+     */
+    @Transactional
+    public EquipResult equip(long userId, Role role, LookSlot slot, ShopItem item) {
+        if (item == null) {
+            ledger.unequip(userId, slot);
+            return EquipResult.DONE;
+        }
+        if (item.slot() != slot) {
+            return EquipResult.WRONG_SLOT;
+        }
+        if (!Looks.owned(ledger.bought(userId), role).contains(item.name())) {
+            return EquipResult.NOT_OWNED;
+        }
+        ledger.equip(userId, slot, item.name());
+        return EquipResult.DONE;
+    }
+
+    /**
+     * The looks a visitor of the public profile sees; the role comes from the profile ticket.
+     */
+    @Public
+    public Map<LookSlot, String> publicLooks(long userId, Role role) {
+        return Looks.wearable(ledger.equipped(userId), Looks.owned(ledger.bought(userId), role));
+    }
+
     /**
      * Every active user, each in its own transaction; one failure does not stop the others. Runs after the nightly
      * sync and the image repair, so month and streak bonuses also reach users who do not open the app.

src/main/java/core_service/shared/security/ProfileTicket.java

@@ -5,7 +5,8 @@ import java.util.Set;
 /**
  * A valid public-profile ticket from Auth.
  *
+ * @param role the role of the user; USER for a ticket without the claim
  * @param profileStats the names of the stat groups the user shows on the profile; empty for a ticket without them
  * @param sections the names of the profile sections the user shows; null for a ticket without them, which shows all
  */
-public record ProfileTicket(long userId, Set<String> profileStats, Set<String> sections) {}
+public record ProfileTicket(long userId, Role role, Set<String> profileStats, Set<String> sections) {}

src/test/java/core_service/configuration/security/JwtServiceTest.java

@@ -109,17 +109,28 @@ class JwtServiceTest extends AbstractUnitTest {
 
     @Test
     void verifyProfileTicket_ReturnsTheUser() {
-        assertEquals(Optional.of(new ProfileTicket(42L, Set.of(), null)),
+        assertEquals(Optional.of(new ProfileTicket(42L, Role.USER, Set.of(), null)),
                 jwtService.verifyProfileTicket(signTicket(JwtService.PROFILE_TICKET_AUDIENCE, "42", 60_000)));
     }
 
+    @Test
+    void verifyProfileTicket_ReadsTheRoleAndTakesUserWithoutIt() {
+        String ticket = Jwts.builder().subject("public-profile").issuer(JwtService.ISSUER).audience().add(JwtService.PROFILE_TICKET_AUDIENCE).and().claim("profileUserId", "42")
+                .claim("role", "PLATFORM_ADMIN")
+                .expiration(new Date(System.currentTimeMillis() + 60_000)).signWith(signingKey, Jwts.SIG.EdDSA).compact();
+
+        assertEquals(Role.PLATFORM_ADMIN, jwtService.verifyProfileTicket(ticket).orElseThrow().role());
+        assertEquals(Role.USER, jwtService.verifyProfileTicket(signTicket(JwtService.PROFILE_TICKET_AUDIENCE, "42", 60_000))
+                .orElseThrow().role());
+    }
+
     @Test
     void verifyProfileTicket_ReadsTheSharedStatGroups() {
         String ticket = Jwts.builder().subject("public-profile").issuer(JwtService.ISSUER).audience().add(JwtService.PROFILE_TICKET_AUDIENCE).and().claim("profileUserId", "42")
                 .claim("profileStats", List.of("PILE", "TREND"))
                 .expiration(new Date(System.currentTimeMillis() + 60_000)).signWith(signingKey, Jwts.SIG.EdDSA).compact();
 
-        assertEquals(Optional.of(new ProfileTicket(42L, Set.of("PILE", "TREND"), null)), jwtService.verifyProfileTicket(ticket));
+        assertEquals(Optional.of(new ProfileTicket(42L, Role.USER, Set.of("PILE", "TREND"), null)), jwtService.verifyProfileTicket(ticket));
     }
 
     @Test
@@ -128,7 +139,7 @@ class JwtServiceTest extends AbstractUnitTest {
                 .claim("sections", List.of("PLAYING", "STATS"))
                 .expiration(new Date(System.currentTimeMillis() + 60_000)).signWith(signingKey, Jwts.SIG.EdDSA).compact();
 
-        assertEquals(Optional.of(new ProfileTicket(42L, Set.of(), Set.of("PLAYING", "STATS"))), jwtService.verifyProfileTicket(ticket));
+        assertEquals(Optional.of(new ProfileTicket(42L, Role.USER, Set.of(), Set.of("PLAYING", "STATS"))), jwtService.verifyProfileTicket(ticket));
     }
 
     @Test

src/test/java/core_service/configuration/security/PublicEndpointsTest.java

@@ -93,6 +93,12 @@ class PublicEndpointsTest {
                 .andExpect(jsonPath("$.code").value("INVALID_TICKET"));
     }
 
+    @Test
+    void publicRewardsEndpointIsPublic() throws Exception {
+        mockMvc.perform(get("/api/public/profiles/rewards")).andExpect(status().isUnauthorized())
+                .andExpect(jsonPath("$.code").value("INVALID_TICKET"));
+    }
+
     // Without a login: a class role marker on the way would answer 401.
     @Test
     void publicProfileWithSharedStats_WorksWithoutALogin() throws Exception {

src/test/java/core_service/modules/rewards/api/PublicRewardControllerTest.java

@@ -0,0 +1,63 @@
+package core_service.modules.rewards.api;
+
+import core_service.modules.rewards.domain.LookSlot;
+import core_service.modules.rewards.repo.RewardLedgerRepository;
+import core_service.shared.security.Role;
+import core_service.shared.test.AbstractIntegrationTest;
+import core_service.shared.test.ContractTokens;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.webmvc.test.autoconfigure.AutoConfigureMockMvc;
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.test.web.servlet.MockMvc;
+
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+@AutoConfigureMockMvc
+class PublicRewardControllerTest extends AbstractIntegrationTest {
+
+    private static final long USER = 5L;
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    @Autowired
+    private RewardLedgerRepository ledger;
+
+    @Autowired
+    private JdbcTemplate jdbc;
+
+    @BeforeEach
+    void seed() {
+        jdbc.update("delete from reward_ledger where user_id = ?", USER);
+        jdbc.update("delete from reward_equipped where user_id = ?", USER);
+        // An admin wears a free item: only the role in the ticket makes it show.
+        ledger.equip(USER, LookSlot.BADGE, "BADGE_PILE_SLAYER");
+    }
+
+    @Test
+    void rewards_TicketOfAnAdmin_ShowsTheFreeItem() throws Exception {
+        mockMvc.perform(get("/api/public/profiles/rewards")
+                        .header("X-Profile-Ticket", ContractTokens.ticketToken(USER, Role.PLATFORM_ADMIN)))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.equipped.BADGE").value("BADGE_PILE_SLAYER"));
+    }
+
+    @Test
+    void rewards_TicketOfAUser_ShowsOnlyWhatIsOwned() throws Exception {
+        mockMvc.perform(get("/api/public/profiles/rewards")
+                        .header("X-Profile-Ticket", ContractTokens.ticketToken(USER, Role.USER)))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.equipped").isEmpty());
+    }
+
+    @Test
+    void rewards_WithoutATicket_Answers401() throws Exception {
+        mockMvc.perform(get("/api/public/profiles/rewards"))
+                .andExpect(status().isUnauthorized())
+                .andExpect(jsonPath("$.code").value("INVALID_TICKET"));
+    }
+}

src/test/java/core_service/modules/rewards/api/RewardControllerTest.java

@@ -1,16 +1,24 @@
 package core_service.modules.rewards.api;
 
+import core_service.configuration.security.ClientHeaderFilter;
 import core_service.modules.rewards.service.RewardService;
+import core_service.shared.security.Role;
 import core_service.shared.test.AbstractIntegrationTest;
+import core_service.shared.test.ContractTokens;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.webmvc.test.autoconfigure.AutoConfigureMockMvc;
+import org.springframework.http.MediaType;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.ResultActions;
+import org.springframework.test.web.servlet.request.MockHttpServletRequestBuilder;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.put;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
 
@@ -21,6 +29,7 @@ import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.
 class RewardControllerTest extends AbstractIntegrationTest {
 
     private static final long USER = 1L;
+    private static final long ADMIN = 2L;
     private static final long GAME = 4_100_001L;
 
     @Autowired
@@ -34,8 +43,8 @@ class RewardControllerTest extends AbstractIntegrationTest {
 
     @BeforeEach
     void clean() {
-        jdbc.update("delete from reward_ledger where user_id = ?", USER);
-        jdbc.update("delete from reward_equipped where user_id = ?", USER);
+        jdbc.update("delete from reward_ledger where user_id in (?, ?)", USER, ADMIN);
+        jdbc.update("delete from reward_equipped where user_id in (?, ?)", USER, ADMIN);
         jdbc.update("delete from user_game_playtime_day where user_id = ?", USER);
         jdbc.update("delete from user_game where user_id = ?", USER);
     }
@@ -137,4 +146,82 @@ class RewardControllerTest extends AbstractIntegrationTest {
         Long sum = jdbc.queryForObject("select coalesce(sum(points), 0) from reward_ledger where user_id = ?", Long.class, USER);
         return sum != null ? sum : 0;
     }
+
+    private void points(long userId, int points) {
+        jdbc.update("insert into reward_ledger (user_id, kind, ref, points, event_at) values (?, 'STARTER', 'STARTER', ?, now())",
+                userId, points);
+    }
+
+    private static MockHttpServletRequestBuilder asAdmin(
+            MockHttpServletRequestBuilder request) {
+        return request.header("Authorization", "Bearer " + ContractTokens.loginToken(ADMIN, Role.PLATFORM_ADMIN));
+    }
+
+    private ResultActions buy(String item) throws Exception {
+        return mockMvc.perform(post("/api/rewards/purchases").header(ClientHeaderFilter.CLIENT_HEADER, "test")
+                .contentType(MediaType.APPLICATION_JSON).content("{\"item\":\"" + item + "\"}"));
+    }
+
+    private ResultActions equip(String slot, String item) throws Exception {
+        return mockMvc.perform(put("/api/rewards/equipped/" + slot).header(ClientHeaderFilter.CLIENT_HEADER, "test")
+                .contentType(MediaType.APPLICATION_JSON).content("{\"item\":" + (item == null ? "null" : "\"" + item + "\"") + "}"));
+    }
+
+    @Test
+    void buy_WithTooFewPoints_Answers409AndKeepsTheBalance() throws Exception {
+        points(USER, 99);
+
+        buy("BADGE_PILE_SLAYER").andExpect(status().isConflict()).andExpect(jsonPath("$.code").value("NOT_ENOUGH_POINTS"));
+
+        mockMvc.perform(get("/api/rewards/wallet")).andExpect(jsonPath("$.balance").value(99));
+    }
+
+    @Test
+    void buy_WithEnoughPoints_BooksTheSpendAndOwnsTheItem() throws Exception {
+        points(USER, 150);
+
+        buy("BADGE_PILE_SLAYER").andExpect(status().isOk())
+                .andExpect(jsonPath("$.balance").value(50))
+                .andExpect(jsonPath("$.owned[0]").value("BADGE_PILE_SLAYER"))
+                .andExpect(jsonPath("$.history[0].kind").value("BUY"))
+                .andExpect(jsonPath("$.history[0].points").value(-100));
+
+        buy("BADGE_PILE_SLAYER").andExpect(status().isConflict()).andExpect(jsonPath("$.code").value("ALREADY_OWNED"));
+    }
+
+    @Test
+    void equip_NotOwned_Answers409_OwnedShowsInTheWalletAndNullTakesItOff() throws Exception {
+        points(USER, 150);
+
+        equip("BADGE", "BADGE_PILE_SLAYER").andExpect(status().isConflict()).andExpect(jsonPath("$.code").value("NOT_OWNED"));
+
+        buy("BADGE_PILE_SLAYER");
+        equip("BADGE", "BADGE_PILE_SLAYER").andExpect(status().isOk())
+                .andExpect(jsonPath("$.equipped.BADGE").value("BADGE_PILE_SLAYER"));
+        equip("BADGE", null).andExpect(status().isOk()).andExpect(jsonPath("$.equipped.BADGE").doesNotExist());
+    }
+
+    @Test
+    void equip_ItemOfAnotherSlot_Answers400() throws Exception {
+        points(USER, 150);
+        buy("BADGE_PILE_SLAYER");
+
+        equip("ACCENT", "BADGE_PILE_SLAYER").andExpect(status().isBadRequest()).andExpect(jsonPath("$.code").value("WRONG_SLOT"));
+    }
+
+    @Test
+    void admin_OwnsEveryItem_NeverBuysAndFallsBackToDefaultAsAUser() throws Exception {
+        mockMvc.perform(asAdmin(get("/api/rewards/wallet")))
+                .andExpect(jsonPath("$.owned.length()").value(8));
+        mockMvc.perform(asAdmin(post("/api/rewards/purchases")).header(ClientHeaderFilter.CLIENT_HEADER, "test")
+                        .contentType(MediaType.APPLICATION_JSON).content("{\"item\":\"FRAME_GOLD\"}"))
+                .andExpect(status().isConflict()).andExpect(jsonPath("$.code").value("ALREADY_OWNED"));
+        mockMvc.perform(asAdmin(put("/api/rewards/equipped/BANNER_FRAME")).header(ClientHeaderFilter.CLIENT_HEADER, "test")
+                        .contentType(MediaType.APPLICATION_JSON).content("{\"item\":\"FRAME_GOLD\"}"))
+                .andExpect(status().isOk()).andExpect(jsonPath("$.equipped.BANNER_FRAME").value("FRAME_GOLD"));
+
+        mockMvc.perform(get("/api/rewards/wallet").header("Authorization", "Bearer " + ContractTokens.loginToken(ADMIN)))
+                .andExpect(jsonPath("$.owned").isEmpty())
+                .andExpect(jsonPath("$.equipped").isEmpty());
+    }
 }

src/test/java/core_service/modules/rewards/service/RewardServiceConcurrencyTest.java

@@ -0,0 +1,60 @@
+package core_service.modules.rewards.service;
+
+import core_service.modules.rewards.domain.ShopItem;
+import core_service.shared.security.Role;
+import core_service.shared.test.AbstractIntegrationTest;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.jdbc.core.JdbcTemplate;
+
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class RewardServiceConcurrencyTest extends AbstractIntegrationTest {
+
+    private static final long USER = 6L;
+
+    @Autowired
+    private RewardService rewardService;
+
+    @Autowired
+    private JdbcTemplate jdbc;
+
+    @BeforeEach
+    @AfterEach
+    void clean() {
+        jdbc.update("delete from reward_ledger where user_id = ?", USER);
+    }
+
+    @Test
+    void twoParallelBuysOfTheLastPoints_OnlyOneSucceeds() throws Exception {
+        jdbc.update("insert into reward_ledger (user_id, kind, ref, points, event_at) values (?, 'STARTER', 'STARTER', 150, now())", USER);
+        CountDownLatch go = new CountDownLatch(1);
+
+        // Two different items: only the balance check can stop the second one.
+        CompletableFuture<RewardService.BuyResult> first = buyAfter(go, ShopItem.BORDER_GOLD);
+        CompletableFuture<RewardService.BuyResult> second = buyAfter(go, ShopItem.FRAME_GOLD);
+        go.countDown();
+
+        List<RewardService.BuyResult> results = List.of(first.get(30, TimeUnit.SECONDS), second.get(30, TimeUnit.SECONDS));
+        assertThat(results).containsExactlyInAnyOrder(RewardService.BuyResult.BOUGHT, RewardService.BuyResult.NOT_ENOUGH_POINTS);
+        assertThat(rewardService.wallet(USER, Role.USER).balance()).isZero();
+    }
+
+    private CompletableFuture<RewardService.BuyResult> buyAfter(CountDownLatch go, ShopItem item) {
+        return CompletableFuture.supplyAsync(() -> {
+            try {
+                go.await(10, TimeUnit.SECONDS);
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+            }
+            return rewardService.buy(USER, Role.USER, item);
+        });
+    }
+}

src/test/java/core_service/shared/test/ContractTokens.java

@@ -87,8 +87,13 @@ public final class ContractTokens {
      * @param sections     null for a ticket without the claim
      */
     public static Map<String, Object> ticket(long userId, List<String> profileStats, List<String> sections) {
+        return ticket(userId, Role.USER, profileStats, sections);
+    }
+
+    public static Map<String, Object> ticket(long userId, Role role, List<String> profileStats, List<String> sections) {
         Map<String, Object> claims = claims(PUBLIC_PROFILE);
         claims.put("profileUserId", String.valueOf(userId));
+        claims.put("role", role.name());
         putOrRemove(claims, "profileStats", profileStats);
         putOrRemove(claims, "sections", sections);
         return claims;
@@ -98,6 +103,10 @@ public final class ContractTokens {
         return sign(ticket(userId, profileStats, sections));
     }
 
+    public static String ticketToken(long userId, Role role) {
+        return sign(ticket(userId, role, null, null));
+    }
+
     public static String serviceToken() {
         return sign(claims(SERVICE));
     }

src/test/resources/contract/auth-core-contract.json

@@ -13,6 +13,7 @@
       "aud": ["tbp-public-profile"],
       "sub": "public-profile",
       "profileUserId": "42",
+      "role": "USER",
       "profileStats": ["OVERVIEW"],
       "sections": ["SUMMARY"]
     },