package v2rayhttp

import (
	"bufio"
	"context"
	"io"
	"math/rand"
	"net"
	"net/http"
	"net/url"
	"strings"

	"github.com/sagernet/sing-box/adapter"
	"github.com/sagernet/sing-box/common/tls"
	"github.com/sagernet/sing-box/option"
	E "github.com/sagernet/sing/common/exceptions"
	M "github.com/sagernet/sing/common/metadata"
	N "github.com/sagernet/sing/common/network"

	"golang.org/x/net/http2"
)

var _ adapter.V2RayClientTransport = (*Client)(nil)

type Client struct {
	ctx        context.Context
	dialer     N.Dialer
	serverAddr M.Socksaddr
	transport  http.RoundTripper
	http2      bool
	url        *url.URL
	host       []string
	method     string
	headers    http.Header
}

func NewClient(ctx context.Context, dialer N.Dialer, serverAddr M.Socksaddr, options option.V2RayHTTPOptions, tlsConfig tls.Config) adapter.V2RayClientTransport {
	var transport http.RoundTripper
	if tlsConfig == nil {
		transport = &http.Transport{
			DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
				return dialer.DialContext(ctx, network, M.ParseSocksaddr(addr))
			},
		}
	} else {
		tlsConfig.SetNextProtos([]string{http2.NextProtoTLS})
		transport = &http2.Transport{
			DialTLSContext: func(ctx context.Context, network, addr string, cfg *tls.STDConfig) (net.Conn, error) {
				conn, err := dialer.DialContext(ctx, network, M.ParseSocksaddr(addr))
				if err != nil {
					return nil, err
				}
				return tls.ClientHandshake(ctx, conn, tlsConfig)
			},
		}
	}
	client := &Client{
		ctx:        ctx,
		dialer:     dialer,
		serverAddr: serverAddr,
		host:       options.Host,
		method:     options.Method,
		headers:    make(http.Header),
		transport:  transport,
		http2:      tlsConfig != nil,
	}
	if client.method == "" {
		client.method = "PUT"
	}
	var uri url.URL
	if tlsConfig == nil {
		uri.Scheme = "http"
	} else {
		uri.Scheme = "https"
	}
	uri.Host = serverAddr.String()
	uri.Path = options.Path
	if !strings.HasPrefix(uri.Path, "/") {
		uri.Path = "/" + uri.Path
	}
	for key, value := range options.Headers {
		client.headers.Set(key, value)
	}
	client.url = &uri
	return client
}

func (c *Client) DialContext(ctx context.Context) (net.Conn, error) {
	if !c.http2 {
		return c.dialHTTP(ctx)
	} else {
		return c.dialHTTP2(ctx)
	}
}

func (c *Client) dialHTTP(ctx context.Context) (net.Conn, error) {
	conn, err := c.dialer.DialContext(c.ctx, N.NetworkTCP, c.serverAddr)
	if err != nil {
		return nil, err
	}
	request := &http.Request{
		Method:     c.method,
		URL:        c.url,
		ProtoMajor: 1,
		Proto:      "HTTP/1.1",
		Header:     c.headers.Clone(),
	}
	request = request.WithContext(ctx)
	switch hostLen := len(c.host); hostLen {
	case 0:
	case 1:
		request.Host = c.host[0]
	default:
		request.Host = c.host[rand.Intn(hostLen)]
	}
	err = request.Write(conn)
	if err != nil {
		return nil, err
	}
	reader := bufio.NewReader(conn)
	response, err := http.ReadResponse(reader, request)
	if err != nil {
		return nil, err
	}
	if response.StatusCode != 200 {
		return nil, E.New("unexpected status: ", response.Status)
	}
	return conn, nil
}

func (c *Client) dialHTTP2(ctx context.Context) (net.Conn, error) {
	pipeInReader, pipeInWriter := io.Pipe()
	request := &http.Request{
		Method:     c.method,
		Body:       pipeInReader,
		URL:        c.url,
		ProtoMajor: 2,
		Proto:      "HTTP/2",
		Header:     c.headers.Clone(),
	}
	request = request.WithContext(ctx)
	switch hostLen := len(c.host); hostLen {
	case 0:
	case 1:
		request.Host = c.host[0]
	default:
		request.Host = c.host[rand.Intn(hostLen)]
	}
	// Disable any compression method from server.
	request.Header.Set("Accept-Encoding", "identity")
	conn := newLateHTTPConn(pipeInWriter)
	go func() {
		response, err := c.transport.RoundTrip(request)
		if err != nil {
			conn.setup(nil, err)
		} else if response.StatusCode != 200 {
			conn.setup(nil, E.New("unexpected status: ", response.StatusCode, " ", response.Status))
		} else {
			conn.setup(response.Body, nil)
		}
	}()
	return conn, nil
}