From 9fffb801ed3dedbb3935c811c7d61ed953ff22dc Mon Sep 17 00:00:00 2001
From: Aditya <k.aditya00@gmail.com>
Date: Wed, 8 Jul 2020 20:18:38 +0530
Subject: [PATCH] feat: H2Agent, H2ConnectionPool base implementation

---
 scrapy/core/downloader/handlers/http2.py | 55 ++++++++++++++++++++
 scrapy/core/http2/agent.py               | 64 ++++++++++++++++++++++++
 2 files changed, 119 insertions(+)
 create mode 100644 scrapy/core/downloader/handlers/http2.py
 create mode 100644 scrapy/core/http2/agent.py

diff --git a/scrapy/core/downloader/handlers/http2.py b/scrapy/core/downloader/handlers/http2.py
new file mode 100644
index 000000000..0dc06f4d8
--- /dev/null
+++ b/scrapy/core/downloader/handlers/http2.py
@@ -0,0 +1,55 @@
+import warnings
+
+from scrapy.core.downloader.tls import openssl_methods
+from scrapy.core.http2.agent import H2Agent, H2ConnectionPool
+from scrapy.http.request import Request
+from scrapy.settings import Settings
+from scrapy.utils.misc import create_instance, load_object
+
+
+class H2DownloadHandler:
+    def __init__(self, settings: Settings, crawler=None):
+        self._crawler = crawler
+
+        from twisted.internet import reactor
+        self._pool = H2ConnectionPool(reactor, settings)
+
+        self._ssl_method = openssl_methods[settings.get('DOWNLOADER_CLIENT_TLS_METHOD')]
+        self._context_factory_cls = load_object(settings['DOWNLOADER_CLIENTCONTEXTFACTORY'])
+        # try method-aware context factory
+        try:
+            self._context_factory = create_instance(
+                objcls=self._context_factory_cls,
+                settings=settings,
+                crawler=crawler,
+                method=self._ssl_method,
+            )
+        except TypeError:
+            # use context factory defaults
+            self._context_factory = create_instance(
+                objcls=self._context_factory_cls,
+                settings=settings,
+                crawler=crawler,
+            )
+            msg = """
+         '%s' does not accept `method` argument (type OpenSSL.SSL method,\
+         e.g. OpenSSL.SSL.SSLv23_METHOD) and/or `tls_verbose_logging` argument and/or `tls_ciphers` argument.\
+         Please upgrade your context factory class to handle them or ignore them.""" % (
+                settings['DOWNLOADER_CLIENTCONTEXTFACTORY'],)
+            warnings.warn(msg)
+
+    @classmethod
+    def from_crawler(cls, crawler):
+        return cls(crawler.settings, crawler)
+
+    def download_request(self, request: Request, spider):
+        from twisted.internet import reactor
+
+        agent = H2Agent(reactor, self._pool, self._context_factory)
+        d = agent.request(request)
+
+        def print_result(result):
+            print(result)
+
+        d.addCallback(print_result)
+        return d
diff --git a/scrapy/core/http2/agent.py b/scrapy/core/http2/agent.py
new file mode 100644
index 000000000..e14e5d633
--- /dev/null
+++ b/scrapy/core/http2/agent.py
@@ -0,0 +1,64 @@
+from typing import Dict, Tuple
+
+from twisted.internet import defer
+from twisted.internet.base import ReactorBase
+from twisted.internet.defer import Deferred
+from twisted.internet.endpoints import SSL4ClientEndpoint, optionsForClientTLS
+from twisted.web.client import URI, BrowserLikePolicyForHTTPS
+
+from scrapy.core.http2.protocol import H2ClientProtocol, H2ClientFactory
+from scrapy.http.request import Request
+from scrapy.settings import Settings
+from scrapy.utils.python import to_bytes, to_unicode
+
+
+class H2ConnectionPool:
+    def __init__(self, reactor: ReactorBase, settings: Settings) -> None:
+        self._reactor = reactor
+        self.settings = settings
+        self._connections: Dict[Tuple, H2ClientProtocol] = {}
+
+    def get_connection(self, uri: URI, endpoint: SSL4ClientEndpoint) -> Deferred:
+        key = (uri.scheme, uri.host, uri.port)
+        conn = self._connections.get(key, None)
+        if conn:
+            return defer.succeed(conn)
+        return self._new_connection(key, uri, endpoint)
+
+    def _new_connection(self, key: Tuple, uri: URI, endpoint: SSL4ClientEndpoint) -> Deferred:
+        factory = H2ClientFactory(uri, self.settings)
+        d = endpoint.connect(factory)
+
+        def put_connection(conn: H2ClientProtocol) -> H2ClientProtocol:
+            self._connections[key] = conn
+            return conn
+
+        d.addCallback(put_connection)
+        return d
+
+    def _remove_connection(self, key) -> None:
+        conn = self._connections.pop(key)
+        conn.loseConnection()
+
+
+class H2Agent:
+    def __init__(
+        self, reactor: ReactorBase, pool: H2ConnectionPool,
+        context_factory=BrowserLikePolicyForHTTPS()
+    ) -> None:
+        self._reactor = reactor
+        self._pool = pool
+        self._context_factory = context_factory
+
+    def request(self, request: Request) -> Deferred:
+        uri = URI.fromBytes(to_bytes(request.url, encoding='ascii'))
+        # options = optionsForClientTLS(hostname=to_unicode(uri.host), acceptableProtocols=[b'h2'])
+        # Hacky fix: Use options instead of self._context_factory to make endpoint work for HTTP/2
+        endpoint = SSL4ClientEndpoint(self._reactor, to_unicode(uri.host), uri.port, self._context_factory)
+        d = self._pool.get_connection(uri, endpoint)
+
+        def cb_connected(conn: H2ClientProtocol):
+            return conn.request(request)
+
+        d.addCallback(cb_connected)
+        return d