package netxlite

import (
	"context"
	"crypto/tls"
	"io"
	"net/http"

	"github.com/lucas-clemente/quic-go"
	"github.com/lucas-clemente/quic-go/http3"
)

// http3Dialer adapts a QUICContextDialer to work with
// an http3.RoundTripper. This is necessary because the
// http3.RoundTripper does not support DialContext.
type http3Dialer struct {
	QUICDialer
}

// dial is like QUICContextDialer.DialContext but without context.
func (d *http3Dialer) dial(network, address string, tlsConfig *tls.Config,
	quicConfig *quic.Config) (quic.EarlySession, error) {
	return d.QUICDialer.DialContext(
		context.Background(), network, address, tlsConfig, quicConfig)
}

// http3RoundTripper is the abstract type of quic-go/http3.RoundTripper.
type http3RoundTripper interface {
	http.RoundTripper
	io.Closer
}

// http3Transport is an HTTPTransport using the http3 protocol.
type http3Transport struct {
	child  http3RoundTripper
	dialer QUICDialer
}

var _ HTTPTransport = &http3Transport{}

// RoundTrip implements HTTPTransport.RoundTrip.
func (txp *http3Transport) RoundTrip(req *http.Request) (*http.Response, error) {
	return txp.child.RoundTrip(req)
}

// CloseIdleConnections implements HTTPTransport.CloseIdleConnections.
func (txp *http3Transport) CloseIdleConnections() {
	txp.child.Close()
	txp.dialer.CloseIdleConnections()
}

// NewHTTP3Transport creates a new HTTPTransport using http3. The
// dialer argument MUST NOT be nil. If the tlsConfig argument is nil,
// then the code will use the default TLS configuration.
func NewHTTP3Transport(
	logger Logger, dialer QUICDialer, tlsConfig *tls.Config) HTTPTransport {
	return &httpTransportLogger{
		HTTPTransport: &http3Transport{
			child: &http3.RoundTripper{
				Dial: (&http3Dialer{dialer}).dial,
				// The following (1) reduces the number of headers that Go will
				// automatically send for us and (2) ensures that we always receive
				// back the true headers, such as Content-Length. This change is
				// functional to OONI's goal of observing the network.
				DisableCompression: true,
				TLSClientConfig:    tlsConfig,
			},
			dialer: dialer,
		},
		Logger: logger,
	}
}
