start backend

src/main/java/com/krylov/refound/util/PostSpecification.java

@@ -0,0 +1,58 @@
+package com.krylov.refound.util;
+
+import com.krylov.refound.dto.PostFilter;
+import com.krylov.refound.entity.Post;
+import jakarta.persistence.criteria.Expression;
+import jakarta.persistence.criteria.Predicate;
+import java.util.ArrayList;
+import java.util.List;
+import org.springframework.data.jpa.domain.Specification;
+
+public class PostSpecification {
+  public static Specification<Post> withFilter(PostFilter filter) {
+    return (root, query, cb) -> {
+
+      List<Predicate> predicates = new ArrayList<>();
+
+
+
+      if (filter.getType() != null) {
+        predicates.add(cb.equal(root.get("type"), filter.getType()));
+      }
+
+      if (filter.getCity() != null) {
+        predicates.add(cb.equal(root.get("city"), filter.getCity()));
+      }
+
+      if (filter.getCategory() != null) {
+        predicates.add(cb.equal(root.get("category"), filter.getCategory()));
+      }
+
+      if (filter.getDistrict() != null) {
+        predicates.add(cb.equal(root.get("district"), filter.getDistrict()));
+      }
+      if (filter.getSearch() != null && !filter.getSearch().isBlank()) {
+        String search = "%" + filter.getSearch().toLowerCase() + "%";
+
+        predicates.add(cb.or(
+            cb.like(cb.lower(root.get("title")), search),
+            cb.like(cb.lower(root.get("description")), search)
+        ));
+      }
+      if (filter.getLat() != null && filter.getLng() != null && filter.getRadius() != null) {
+
+        Expression<Double> distance = cb.function(
+            "6371 * acos(cos(radians(?1)) * cos(radians(latitude)) * " +
+                "cos(radians(longitude) - radians(?2)) + sin(radians(?1)) * sin(radians(latitude)))",
+            Double.class,
+            cb.literal(filter.getLat()),
+            cb.literal(filter.getLng())
+        );
+
+        predicates.add(cb.lessThanOrEqualTo(distance, filter.getRadius()));
+      }
+
+      return cb.and(predicates.toArray(new Predicate[0]));
+    };
+  }
+}