feat: Add Predicates to match header value and presence.

Author: nstdio

src/main/java/io/github/nstdio/http/ext/Predicates.java

@@ -18,6 +18,7 @@
 
 import java.net.URI;
 import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
 import java.util.Objects;
 import java.util.function.Predicate;
 
@@ -45,4 +46,32 @@ public static Predicate<HttpRequest> uri(URI uri) {
     Objects.requireNonNull(uri);
     return r -> r.uri().equals(uri);
   }
+
+  /**
+   * The {@code Predicate} that matches only {@code HttpResponse} with given header.
+   *
+   * @param name  The header name.
+   * @param value The header value.
+   *
+   * @return The {@code Predicate} that matches {@code HttpResponse} with given header.
+   */
+  public static <T> Predicate<HttpResponse<T>> hasHeader(String name, String value) {
+    Objects.requireNonNull(name);
+    Objects.requireNonNull(value);
+
+    return r -> r.headers().firstValue(name).filter(value::equals).isPresent();
+  }
+
+  /**
+   * The {@code Predicate} that matches only {@code HttpRequest} with given header.
+   *
+   * @param name The header name.
+   *
+   * @return The {@code Predicate} that matches {@code HttpRequest} with given header.
+   */
+  public static <T> Predicate<HttpResponse<T>> hasHeader(String name) {
+    Objects.requireNonNull(name);
+
+    return r -> r.headers().firstValue(name).isPresent();
+  }
 }

src/test/kotlin/io/github/nstdio/http/ext/PredicatesTest.kt

@@ -34,4 +34,38 @@ class PredicatesTest {
       .accepts(r1)
       .rejects(r2)
   }
+
+  @Test
+  fun `Should accept or reject with header name and value`() {
+    //given
+    val r = StaticHttpResponse.builder<Any>()
+      .statusCode(200)
+      .headers(HttpHeadersBuilder().add("Content-Type", "text/plain").build())
+      .build()
+
+    //when + then
+    assertThat(Predicates.hasHeader<Any>("Content-Type", "text/plain"))
+      .accepts(r)
+
+    assertThat(Predicates.hasHeader<Any>("Content-Type", "text/plain;charset=UTF-8"))
+      .rejects(r)
+    assertThat(Predicates.hasHeader<Any>("Content-Length", "12"))
+      .rejects(r)
+  }
+
+  @Test
+  fun `Should accept or reject with header name`() {
+    //given
+    val r = StaticHttpResponse.builder<Any>()
+      .statusCode(200)
+      .headers(HttpHeadersBuilder().add("Content-Type", "*/*").build())
+      .build()
+
+    //when + then
+    assertThat(Predicates.hasHeader<Any>("Content-Type"))
+      .accepts(r)
+
+    assertThat(Predicates.hasHeader<Any>("Content-Length"))
+      .rejects(r)
+  }
 }