Http[s]Protocol: Make the code start_download DRY

Problem:
- `HttpProtocol::start_download` and `HttpsProtocol::start_download`
  implementations are the same except for a few types.

Solution:
- Follow the "Don't Repeat Yourself" mantra and de-duplicate the code
  using templates.

Userland/Services/ProtocolServer/HttpCommon.h

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/ByteBuffer.h>
+#include <AK/HashMap.h>
+#include <AK/OwnPtr.h>
+#include <AK/String.h>
+#include <LibHTTP/HttpRequest.h>
+#include <ProtocolServer/ClientConnection.h>
+#include <ProtocolServer/Download.h>
+
+namespace ProtocolServer::Detail {
+
+template<typename TBadgedProtocol, typename TPipeResult>
+OwnPtr<Download> start_download(TBadgedProtocol&& protocol, ClientConnection& client, const String& method, const URL& url, const HashMap<String, String>& headers, ReadonlyBytes body, TPipeResult&& pipe_result)
+{
+    using TJob = TBadgedProtocol::Type::JobType;
+    using TDownload = TBadgedProtocol::Type::DownloadType;
+
+    if (pipe_result.is_error()) {
+        return {};
+    }
+
+    HTTP::HttpRequest request;
+    if (method.equals_ignoring_case("post"))
+        request.set_method(HTTP::HttpRequest::Method::POST);
+    else
+        request.set_method(HTTP::HttpRequest::Method::GET);
+    request.set_url(url);
+    request.set_headers(headers);
+    request.set_body(body);
+
+    auto output_stream = make<OutputFileStream>(pipe_result.value().write_fd);
+    output_stream->make_unbuffered();
+    auto job = TJob::construct(request, *output_stream);
+    auto download = TDownload::create_with_job(forward<TBadgedProtocol>(protocol), client, (TJob&)*job, move(output_stream));
+    download->set_download_fd(pipe_result.value().read_fd);
+    job->start();
+    return download;
+}
+
+}

Userland/Services/ProtocolServer/HttpDownload.cpp

@@ -27,6 +27,7 @@
 #include <LibHTTP/HttpJob.h>
 #include <LibHTTP/HttpResponse.h>
 #include <ProtocolServer/HttpDownload.h>
+#include <ProtocolServer/HttpProtocol.h>
 
 namespace ProtocolServer {
 
@@ -66,7 +67,7 @@ HttpDownload::~HttpDownload()
     m_job->shutdown();
 }
 
-NonnullOwnPtr<HttpDownload> HttpDownload::create_with_job(Badge<HttpProtocol>, ClientConnection& client, NonnullRefPtr<HTTP::HttpJob> job, NonnullOwnPtr<OutputFileStream>&& output_stream)
+NonnullOwnPtr<HttpDownload> HttpDownload::create_with_job(Badge<HttpProtocol>&&, ClientConnection& client, NonnullRefPtr<HTTP::HttpJob> job, NonnullOwnPtr<OutputFileStream>&& output_stream)
 {
     return adopt_own(*new HttpDownload(client, move(job), move(output_stream)));
 }

Userland/Services/ProtocolServer/HttpDownload.h

@@ -27,6 +27,7 @@
 #pragma once
 
 #include <AK/Badge.h>
+#include <AK/NonnullOwnPtr.h>
 #include <LibCore/Forward.h>
 #include <LibHTTP/Forward.h>
 #include <ProtocolServer/Download.h>
@@ -36,7 +37,7 @@ namespace ProtocolServer {
 class HttpDownload final : public Download {
 public:
     virtual ~HttpDownload() override;
-    static NonnullOwnPtr<HttpDownload> create_with_job(Badge<HttpProtocol>, ClientConnection&, NonnullRefPtr<HTTP::HttpJob>, NonnullOwnPtr<OutputFileStream>&&);
+    static NonnullOwnPtr<HttpDownload> create_with_job(Badge<HttpProtocol>&&, ClientConnection&, NonnullRefPtr<HTTP::HttpJob>, NonnullOwnPtr<OutputFileStream>&&);
 
 private:
     explicit HttpDownload(ClientConnection&, NonnullRefPtr<HTTP::HttpJob>, NonnullOwnPtr<OutputFileStream>&&);

Userland/Services/ProtocolServer/HttpProtocol.cpp

@@ -24,8 +24,16 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <AK/Badge.h>
+#include <AK/ByteBuffer.h>
+#include <AK/HashMap.h>
+#include <AK/OwnPtr.h>
+#include <AK/String.h>
+#include <AK/URL.h>
 #include <LibHTTP/HttpJob.h>
-#include <LibHTTP/HttpRequest.h>
+#include <ProtocolServer/ClientConnection.h>
+#include <ProtocolServer/Download.h>
+#include <ProtocolServer/HttpCommon.h>
 #include <ProtocolServer/HttpDownload.h>
 #include <ProtocolServer/HttpProtocol.h>
 
@@ -36,32 +44,9 @@ HttpProtocol::HttpProtocol()
 {
 }
 
-HttpProtocol::~HttpProtocol()
-{
-}
-
 OwnPtr<Download> HttpProtocol::start_download(ClientConnection& client, const String& method, const URL& url, const HashMap<String, String>& headers, ReadonlyBytes body)
 {
-    HTTP::HttpRequest request;
+    return Detail::start_download(AK::Badge<HttpProtocol> {}, client, method, url, headers, body, get_pipe_for_download());
-    if (method.equals_ignoring_case("post"))
-        request.set_method(HTTP::HttpRequest::Method::POST);
-    else
-        request.set_method(HTTP::HttpRequest::Method::GET);
-    request.set_url(url);
-    request.set_headers(headers);
-    request.set_body(body);
-
-    auto pipe_result = get_pipe_for_download();
-    if (pipe_result.is_error())
-        return {};
-
-    auto output_stream = make<OutputFileStream>(pipe_result.value().write_fd);
-    output_stream->make_unbuffered();
-    auto job = HTTP::HttpJob::construct(request, *output_stream);
-    auto download = HttpDownload::create_with_job({}, client, (HTTP::HttpJob&)*job, move(output_stream));
-    download->set_download_fd(pipe_result.value().read_fd);
-    job->start();
-    return download;
 }
 
 }

Userland/Services/ProtocolServer/HttpProtocol.h

@@ -26,14 +26,26 @@
 
 #pragma once
 
+#include <AK/ByteBuffer.h>
+#include <AK/HashMap.h>
+#include <AK/OwnPtr.h>
+#include <AK/String.h>
+#include <AK/URL.h>
+#include <LibHTTP/HttpJob.h>
+#include <ProtocolServer/ClientConnection.h>
+#include <ProtocolServer/Download.h>
+#include <ProtocolServer/HttpDownload.h>
 #include <ProtocolServer/Protocol.h>
 
 namespace ProtocolServer {
 
 class HttpProtocol final : public Protocol {
 public:
+    using JobType = HTTP::HttpJob;
+    using DownloadType = HttpDownload;
+
     HttpProtocol();
-    virtual ~HttpProtocol() override;
+    ~HttpProtocol() override = default;
 
     virtual OwnPtr<Download> start_download(ClientConnection&, const String& method, const URL&, const HashMap<String, String>& headers, ReadonlyBytes body) override;
 };

Userland/Services/ProtocolServer/HttpsDownload.cpp

@@ -27,6 +27,7 @@
 #include <LibHTTP/HttpResponse.h>
 #include <LibHTTP/HttpsJob.h>
 #include <ProtocolServer/HttpsDownload.h>
+#include <ProtocolServer/HttpsProtocol.h>
 
 namespace ProtocolServer {
 
@@ -74,7 +75,7 @@ HttpsDownload::~HttpsDownload()
     m_job->shutdown();
 }
 
-NonnullOwnPtr<HttpsDownload> HttpsDownload::create_with_job(Badge<HttpsProtocol>, ClientConnection& client, NonnullRefPtr<HTTP::HttpsJob> job, NonnullOwnPtr<OutputFileStream>&& output_stream)
+NonnullOwnPtr<HttpsDownload> HttpsDownload::create_with_job(Badge<HttpsProtocol>&&, ClientConnection& client, NonnullRefPtr<HTTP::HttpsJob> job, NonnullOwnPtr<OutputFileStream>&& output_stream)
 {
     return adopt_own(*new HttpsDownload(client, move(job), move(output_stream)));
 }

Userland/Services/ProtocolServer/HttpsDownload.h

@@ -36,7 +36,7 @@ namespace ProtocolServer {
 class HttpsDownload final : public Download {
 public:
     virtual ~HttpsDownload() override;
-    static NonnullOwnPtr<HttpsDownload> create_with_job(Badge<HttpsProtocol>, ClientConnection&, NonnullRefPtr<HTTP::HttpsJob>, NonnullOwnPtr<OutputFileStream>&&);
+    static NonnullOwnPtr<HttpsDownload> create_with_job(Badge<HttpsProtocol>&&, ClientConnection&, NonnullRefPtr<HTTP::HttpsJob>, NonnullOwnPtr<OutputFileStream>&&);
 
 private:
     explicit HttpsDownload(ClientConnection&, NonnullRefPtr<HTTP::HttpsJob>, NonnullOwnPtr<OutputFileStream>&&);

Userland/Services/ProtocolServer/HttpsProtocol.cpp

@@ -24,8 +24,16 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#include <LibHTTP/HttpRequest.h>
+#include <AK/Badge.h>
+#include <AK/ByteBuffer.h>
+#include <AK/HashMap.h>
+#include <AK/OwnPtr.h>
+#include <AK/String.h>
+#include <AK/URL.h>
 #include <LibHTTP/HttpsJob.h>
+#include <ProtocolServer/ClientConnection.h>
+#include <ProtocolServer/Download.h>
+#include <ProtocolServer/HttpCommon.h>
 #include <ProtocolServer/HttpsDownload.h>
 #include <ProtocolServer/HttpsProtocol.h>
 
@@ -36,32 +44,9 @@ HttpsProtocol::HttpsProtocol()
 {
 }
 
-HttpsProtocol::~HttpsProtocol()
-{
-}
-
 OwnPtr<Download> HttpsProtocol::start_download(ClientConnection& client, const String& method, const URL& url, const HashMap<String, String>& headers, ReadonlyBytes body)
 {
-    HTTP::HttpRequest request;
+    return Detail::start_download(AK::Badge<HttpsProtocol> {}, client, method, url, headers, body, get_pipe_for_download());
-    if (method.equals_ignoring_case("post"))
-        request.set_method(HTTP::HttpRequest::Method::POST);
-    else
-        request.set_method(HTTP::HttpRequest::Method::GET);
-    request.set_url(url);
-    request.set_headers(headers);
-    request.set_body(body);
-
-    auto pipe_result = get_pipe_for_download();
-    if (pipe_result.is_error())
-        return {};
-
-    auto output_stream = make<OutputFileStream>(pipe_result.value().write_fd);
-    output_stream->make_unbuffered();
-    auto job = HTTP::HttpsJob::construct(request, *output_stream);
-    auto download = HttpsDownload::create_with_job({}, client, (HTTP::HttpsJob&)*job, move(output_stream));
-    download->set_download_fd(pipe_result.value().read_fd);
-    job->start();
-    return download;
 }
 
 }

Userland/Services/ProtocolServer/HttpsProtocol.h

@@ -26,14 +26,26 @@
 
 #pragma once
 
+#include <AK/ByteBuffer.h>
+#include <AK/HashMap.h>
+#include <AK/OwnPtr.h>
+#include <AK/String.h>
+#include <AK/URL.h>
+#include <LibHTTP/HttpsJob.h>
+#include <ProtocolServer/ClientConnection.h>
+#include <ProtocolServer/Download.h>
+#include <ProtocolServer/HttpsDownload.h>
 #include <ProtocolServer/Protocol.h>
 
 namespace ProtocolServer {
 
 class HttpsProtocol final : public Protocol {
 public:
+    using JobType = HTTP::HttpsJob;
+    using DownloadType = HttpsDownload;
+
     HttpsProtocol();
-    virtual ~HttpsProtocol() override;
+    ~HttpsProtocol() override = default;
 
     virtual OwnPtr<Download> start_download(ClientConnection&, const String& method, const URL&, const HashMap<String, String>& headers, ReadonlyBytes body) override;
 };