Convert scheme to lower case when parsing URI (#2938)

Motivation:

`HttpRequestMetaData#scheme()` javadocs state the result will be lowercase, but this is not always the case because `Uri3986` parses the scheme as-is. As a result, `DefaultMultiAddressUrlHttpClientBuilder` may have more than 1 client instance for the same address if users use URI with different scheme letters case. 
See #1423 for details.

Modifications:

- Convert scheme to lower case when parsing `Uri3986` reusing well-known schemes ("http" and "https")

Result:

Fixes #1423.

servicetalk-http-api/src/main/java/io/servicetalk/http/api/Uri3986.java

@@ -17,6 +17,7 @@
 package io.servicetalk.http.api;
 
 import java.nio.charset.Charset;
+import java.util.Locale;
 import java.util.Objects;
 import javax.annotation.Nullable;
 
@@ -38,6 +39,8 @@
 final class Uri3986 implements Uri {
     @SuppressWarnings({"StringOperationCanBeSimplified", "PMD.StringInstantiation"})
     private static final String NULL_COMPONENT = new String(""); // instance equality required!
+    private static final String HTTP_SCHEME = "http";
+    private static final String HTTPS_SCHEME = "https";
     private final String uri;
     @Nullable
     private final String scheme;
@@ -169,7 +172,7 @@ final class Uri3986 implements Uri {
                 if (i == 0) {
                     throw new IllegalArgumentException("Invalid URI format: no scheme before colon (':')");
                 }
-                parsedScheme = uri.substring(0, i);
+                parsedScheme = getLowerCaseScheme(uri, i);
                 begin = ++i;
                 // We don't enforce the following, browsers still generate these types of requests.
                 // https://tools.ietf.org/html/rfc3986#section-3.3
@@ -196,6 +199,15 @@ final class Uri3986 implements Uri {
         this.uri = uri;
     }
 
+    private static String getLowerCaseScheme(final String uri, final int endIndex) {
+        if (endIndex == 4 && uri.regionMatches(true, 0, HTTP_SCHEME, 0, 4)) {
+            return HTTP_SCHEME;
+        } else if (endIndex == 5 && uri.regionMatches(true, 0, HTTPS_SCHEME, 0, 5)) {
+            return HTTPS_SCHEME;
+        }
+        return uri.substring(0, endIndex).toLowerCase(Locale.ENGLISH);
+    }
+
     @Override
     public String uri() {
         return uri;

servicetalk-http-api/src/test/java/io/servicetalk/http/api/Uri3986Test.java

@@ -31,7 +31,10 @@
 import static java.util.regex.Pattern.compile;
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalToIgnoringCase;
 import static org.hamcrest.Matchers.lessThan;
+import static org.hamcrest.Matchers.nullValue;
+import static org.hamcrest.Matchers.sameInstance;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
@@ -162,8 +165,21 @@ void emptyUserInfo() {
     }
 
     @Test
-    void schemeParsedCaseSensative() {
-        verifyUri3986("HTTP://test.com", "HTTP", null, "test.com", -1, "", "", null, null, null);
+    void schemeParsedCaseInsensitive() {
+        verifyUri3986("HTTP://test.com", "http", null, "test.com", -1, "", "", null, null, null);
+        verifyUri3986("HTTPS://test.com", "https", null, "test.com", -1, "", "", null, null, null);
+        verifyUri3986("ANY://test.com", "any", null, "test.com", -1, "", "", null, null, null);
+    }
+
+    @Test
+    void reuseWellKnownScheme() {
+        String http1 = new Uri3986("http://test.com").scheme();
+        String http2 = new Uri3986("HTTP://test.com").scheme();
+        assertThat("different http", http1, sameInstance(http2));
+
+        String https1 = new Uri3986("https://test.com").scheme();
+        String https2 = new Uri3986("HTTPS://test.com").scheme();
+        assertThat("different https", https1, sameInstance(https2));
     }
 
     @Test
@@ -637,7 +653,9 @@ private static void verifyUri3986(String expectedUri, @Nullable String expectedS
         // Validate against the RFC's regex
         Matcher matcher = VALID_PATTERN.matcher(expectedUri);
         assertThat(true, is(matcher.matches()));
-        assertThat("invalid scheme()", uri.scheme(), is(matcher.group(2)));
+        String matcherScheme = matcher.group(2);
+        assertThat("invalid scheme()", uri.scheme(),
+                matcherScheme == null ? is(nullValue()) : equalToIgnoringCase(matcherScheme));
         assertThat("invalid authority()", uri.authority(), is(matcher.group(4)));
         assertThat("invalid path()", uri.path(), is(matcher.group(5)));
         assertThat("invalid query()", uri.query(), is(matcher.group(7)));

servicetalk-http-netty/src/test/java/io/servicetalk/http/netty/DefaultMultiAddressUrlHttpClientBuilderTest.java

@@ -37,6 +37,7 @@
 import org.junit.jupiter.api.extension.RegisterExtension;
 
 import java.net.InetSocketAddress;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
 
 import static io.servicetalk.buffer.api.Matchers.contentEqualTo;
@@ -222,6 +223,28 @@ void internalClientsUseDifferentExecutionContextWhenConfigured() throws Exceptio
         }
     }
 
+    @Test
+    void internalClientSchemeShouldBeCaseInsensitive() throws Exception {
+        AtomicInteger counter = new AtomicInteger();
+
+        try (ServerContext serverContext = HttpServers.forAddress(localAddress(0))
+                .listenStreamingAndAwait((ctx, request, responseFactory) -> succeeded(responseFactory.ok()));
+             BlockingHttpClient blockingHttpClient = HttpClients.forMultiAddressUrl(getClass().getSimpleName())
+                     .initializer((scheme, address, builder) -> counter.incrementAndGet())
+                     .buildBlocking()) {
+
+            HttpResponse response = blockingHttpClient.request(
+                    blockingHttpClient.get("http://" + serverHostAndPort(serverContext)));
+            assertThat(response.status(), is(OK));
+
+            response = blockingHttpClient.request(
+                    blockingHttpClient.get("HTTP://" + serverHostAndPort(serverContext)));
+            assertThat(response.status(), is(OK));
+
+            assertThat(counter.get(), is(1));
+        }
+    }
+
     private static void assertExecutionContext(HttpExecutionContext expected, HttpExecutionContext actual) {
         assertThat(actual, is(notNullValue()));
         assertThat(actual.ioExecutor(), is(sameInstance(expected.ioExecutor())));