# Source code for scrapy.downloadermiddlewares.httpproxy

    import base64
    from urllib.parse import unquote, urlunparse
    from urllib.request import _parse_proxy, getproxies, proxy_bypass

    from scrapy.exceptions import NotConfigured
    from scrapy.utils.httpobj import urlparse_cached
    from scrapy.utils.python import to_bytes

    class HttpProxyMiddleware:
        def __init__(self, auth_encoding="latin-1"):
            self.auth_encoding = auth_encoding
            self.proxies = {}
            for type_, url in getproxies().items():
                try:
                    self.proxies[type_] = self._get_proxy(url, type_)
                # some values such as '/var/run/docker.sock' can't be parsed
                # by _parse_proxy and as such should be skipped
                except ValueError:
                    continue

        @classmethod
        def from_crawler(cls, crawler):
            if not crawler.settings.getbool("HTTPPROXY_ENABLED"):
                raise NotConfigured
            auth_encoding = crawler.settings.get("HTTPPROXY_AUTH_ENCODING")
            return cls(auth_encoding)

        def _basic_auth_header(self, username, password):
            user_pass = to_bytes(
                f"{unquote(username)}:{unquote(password)}", encoding=self.auth_encoding
            )
            return base64.b64encode(user_pass)

        def _get_proxy(self, url, orig_type):
            proxy_type, user, password, hostport = _parse_proxy(url)
            proxy_url = urlunparse((proxy_type or orig_type, hostport, "", "", "", ""))

            if user:
                creds = self._basic_auth_header(user, password)
            else:
                creds = None

            return creds, proxy_url

        def process_request(self, request, spider):
            creds, proxy_url = None, None
            if "proxy" in request.meta:
                if request.meta["proxy"] is not None:
                    creds, proxy_url = self._get_proxy(request.meta["proxy"], "")
            elif self.proxies:
                parsed = urlparse_cached(request)
                scheme = parsed.scheme
                if (
                    # 'no_proxy' is only supported by http schemes
                    scheme not in ("http", "https")
                    or not proxy_bypass(parsed.hostname)
                ) and scheme in self.proxies:
                    creds, proxy_url = self.proxies[scheme]

            self._set_proxy_and_creds(request, proxy_url, creds)

        def _set_proxy_and_creds(self, request, proxy_url, creds):
            if proxy_url:
                request.meta["proxy"] = proxy_url
            elif request.meta.get("proxy") is not None:
                request.meta["proxy"] = None
            if creds:
                request.headers[b"Proxy-Authorization"] = b"Basic " + creds
                request.meta["_auth_proxy"] = proxy_url
            elif "_auth_proxy" in request.meta:
                if proxy_url != request.meta["_auth_proxy"]:
                    if b"Proxy-Authorization" in request.headers:
                        del request.headers[b"Proxy-Authorization"]
                    del request.meta["_auth_proxy"]
            elif b"Proxy-Authorization" in request.headers:
                if proxy_url:
                    request.meta["_auth_proxy"] = proxy_url
                else:
                    del request.headers[b"Proxy-Authorization"]