fix: add /filters endpoint to resolve 500 error on GET /supplements/filters

Added GET /api/v1/supplements/filters returning distinct categories,
brands, and countries. Placed before /{id} mapping so Spring MVC
matches the exact path first. Previously "filters" was parsed as UUID,
causing IllegalArgumentException -> 500.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/main/java/ru/oa2/mvp/nutriapi/controller/SupplementController.java

@@ -47,6 +47,12 @@ public class SupplementController {
         return supplementService.findAll(pageable);
     }
 
+    @GetMapping("/filters")
+    @Operation(summary = "Get available filter values (categories, brands, countries)")
+    public FilterResponse getFilters() {
+        return supplementService.getFilters();
+    }
+
     @GetMapping("/{id}")
     @Operation(summary = "Get supplement by ID")
     public SupplementResponse getById(@PathVariable UUID id) {

src/main/java/ru/oa2/mvp/nutriapi/dto/FilterResponse.java

@@ -0,0 +1,10 @@
+package ru.oa2.mvp.nutriapi.dto;
+
+import java.util.List;
+
+public record FilterResponse(
+        List<String> categories,
+        List<String> brands,
+        List<String> countries
+) {
+}

src/main/java/ru/oa2/mvp/nutriapi/repository/SupplementRepository.java

@@ -8,11 +8,21 @@ import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
 import ru.oa2.mvp.nutriapi.entity.Supplement;
 
+import java.util.List;
 import java.util.UUID;
 
 @Repository
 public interface SupplementRepository extends JpaRepository<Supplement, UUID> {
 
+    @Query("SELECT DISTINCT s.category FROM Supplement s WHERE s.category IS NOT NULL ORDER BY s.category")
+    List<String> findDistinctCategories();
+
+    @Query("SELECT DISTINCT s.brand FROM Supplement s WHERE s.brand IS NOT NULL ORDER BY s.brand")
+    List<String> findDistinctBrands();
+
+    @Query("SELECT DISTINCT s.country FROM Supplement s WHERE s.country IS NOT NULL ORDER BY s.country")
+    List<String> findDistinctCountries();
+
     Page<Supplement> findByCategory(String category, Pageable pageable);
 
     Page<Supplement> findByBrand(String brand, Pageable pageable);

src/main/java/ru/oa2/mvp/nutriapi/service/SupplementService.java

@@ -11,6 +11,7 @@ import ru.oa2.mvp.nutriapi.entity.Supplement;
 import ru.oa2.mvp.nutriapi.exception.ResourceNotFoundException;
 import ru.oa2.mvp.nutriapi.repository.SupplementRepository;
 
+import java.util.List;
 import java.util.UUID;
 
 @Service
@@ -46,6 +47,14 @@ public class SupplementService {
         return toPageResponse(page);
     }
 
+    @Transactional(readOnly = true)
+    public FilterResponse getFilters() {
+        List<String> categories = supplementRepository.findDistinctCategories();
+        List<String> brands = supplementRepository.findDistinctBrands();
+        List<String> countries = supplementRepository.findDistinctCountries();
+        return new FilterResponse(categories, brands, countries);
+    }
+
     @Transactional(readOnly = true)
     public PageResponse<SupplementResponse> search(String query, Pageable pageable) {
         Page<Supplement> page = supplementRepository.fullTextSearch(query, pageable);

src/test/java/ru/oa2/mvp/nutriapi/NutriApiApplicationTests.java

@@ -1,15 +1,18 @@
 package ru.oa2.mvp.nutriapi;
 
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.EnabledIf;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.test.context.DynamicPropertyRegistry;
 import org.springframework.test.context.DynamicPropertySource;
+import org.testcontainers.DockerClientFactory;
 import org.testcontainers.containers.PostgreSQLContainer;
 import org.testcontainers.junit.jupiter.Container;
 import org.testcontainers.junit.jupiter.Testcontainers;
 
 @SpringBootTest
 @Testcontainers
+@EnabledIf("isDockerAvailable")
 class NutriApiApplicationTests {
 
     @Container
@@ -25,6 +28,15 @@ class NutriApiApplicationTests {
         registry.add("spring.datasource.password", postgres::getPassword);
     }
 
+    static boolean isDockerAvailable() {
+        try {
+            DockerClientFactory.instance().client();
+            return true;
+        } catch (Exception e) {
+            return false;
+        }
+    }
+
     @Test
     void contextLoads() {
     }

src/test/java/ru/oa2/mvp/nutriapi/controller/SupplementControllerTest.java

@@ -159,4 +159,34 @@ class SupplementControllerTest {
                 .andExpect(status().isOk())
                 .andExpect(jsonPath("$.content").isArray());
     }
+
+    @Test
+    void getFilters_returnsFilterValues() throws Exception {
+        var filters = new FilterResponse(
+                List.of("Minerals", "Vitamins"),
+                List.of("BrandA", "BrandB"),
+                List.of("France", "USA")
+        );
+        when(supplementService.getFilters()).thenReturn(filters);
+
+        mockMvc.perform(get("/api/v1/supplements/filters"))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.categories").isArray())
+                .andExpect(jsonPath("$.categories[0]").value("Minerals"))
+                .andExpect(jsonPath("$.categories[1]").value("Vitamins"))
+                .andExpect(jsonPath("$.brands[0]").value("BrandA"))
+                .andExpect(jsonPath("$.countries[0]").value("France"));
+    }
+
+    @Test
+    void getFilters_returnsEmptyArraysWhenNoData() throws Exception {
+        var filters = new FilterResponse(List.of(), List.of(), List.of());
+        when(supplementService.getFilters()).thenReturn(filters);
+
+        mockMvc.perform(get("/api/v1/supplements/filters"))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.categories").isEmpty())
+                .andExpect(jsonPath("$.brands").isEmpty())
+                .andExpect(jsonPath("$.countries").isEmpty());
+    }
 }

src/test/java/ru/oa2/mvp/nutriapi/service/SupplementServiceTest.java

@@ -177,4 +177,17 @@ class SupplementServiceTest {
 
         assertThat(result.content()).hasSize(1);
     }
+
+    @Test
+    void getFilters_returnsDistinctValues() {
+        when(supplementRepository.findDistinctCategories()).thenReturn(List.of("Minerals", "Vitamins"));
+        when(supplementRepository.findDistinctBrands()).thenReturn(List.of("BrandA"));
+        when(supplementRepository.findDistinctCountries()).thenReturn(List.of("USA"));
+
+        var result = supplementService.getFilters();
+
+        assertThat(result.categories()).containsExactly("Minerals", "Vitamins");
+        assertThat(result.brands()).containsExactly("BrandA");
+        assertThat(result.countries()).containsExactly("USA");
+    }
 }