package splithttp

import (
	"bytes"
	"context"
	"fmt"
	"io"
	gonet "net"
	"net/http"
	"net/http/httptrace"
	"sync"

	"github.com/xtls/xray-core/common"
	"github.com/xtls/xray-core/common/errors"
	"github.com/xtls/xray-core/common/net"
	"github.com/xtls/xray-core/common/signal/done"
)

// interface to abstract between use of browser dialer, vs net/http
type DialerClient interface {
	// (ctx, baseURL, payload) -> err
	// baseURL already contains sessionId and seq
	SendUploadRequest(context.Context, string, io.ReadWriteCloser, int64) error

	// (ctx, baseURL) -> (downloadReader, remoteAddr, localAddr)
	// baseURL already contains sessionId
	OpenDownload(context.Context, string) (io.ReadCloser, net.Addr, net.Addr, error)

	// (ctx, baseURL) -> uploadWriter
	// baseURL already contains sessionId
	OpenUpload(context.Context, string) io.WriteCloser

	// (ctx, pureURL) -> (uploadWriter, downloadReader)
	// pureURL can not contain sessionId
	Open(context.Context, string) (io.WriteCloser, io.ReadCloser)
}

// implements splithttp.DialerClient in terms of direct network connections
type DefaultDialerClient struct {
	transportConfig *Config
	client          *http.Client
	httpVersion     string
	// pool of net.Conn, created using dialUploadConn
	uploadRawPool  *sync.Pool
	dialUploadConn func(ctxInner context.Context) (net.Conn, error)
}

func (c *DefaultDialerClient) Open(ctx context.Context, pureURL string) (io.WriteCloser, io.ReadCloser) {
	reader, writer := io.Pipe()
	req, _ := http.NewRequestWithContext(ctx, "POST", pureURL, reader)
	req.Header = c.transportConfig.GetRequestHeader()
	if !c.transportConfig.NoGRPCHeader {
		req.Header.Set("Content-Type", "application/grpc")
	}
	wrc := &WaitReadCloser{Wait: make(chan struct{})}
	go func() {
		response, err := c.client.Do(req)
		if err != nil || response.StatusCode != 200 {
			if err != nil {
				errors.LogInfoInner(ctx, err, "failed to open ", pureURL)
			} else {
				errors.LogInfo(ctx, "unexpected status ", response.StatusCode)
			}
			wrc.Close()
			return
		}
		wrc.Set(response.Body)
	}()
	return writer, wrc
}

func (c *DefaultDialerClient) OpenUpload(ctx context.Context, baseURL string) io.WriteCloser {
	reader, writer := io.Pipe()
	req, _ := http.NewRequestWithContext(ctx, "POST", baseURL, reader)
	req.Header = c.transportConfig.GetRequestHeader()
	if !c.transportConfig.NoGRPCHeader {
		req.Header.Set("Content-Type", "application/grpc")
	}
	go c.client.Do(req)
	return writer
}

func (c *DefaultDialerClient) OpenDownload(ctx context.Context, baseURL string) (io.ReadCloser, gonet.Addr, gonet.Addr, error) {
	var remoteAddr gonet.Addr
	var localAddr gonet.Addr
	// this is done when the TCP/UDP connection to the server was established,
	// and we can unblock the Dial function and print correct net addresses in
	// logs
	gotConn := done.New()

	var downResponse io.ReadCloser
	gotDownResponse := done.New()

	ctx, ctxCancel := context.WithCancel(ctx)

	go func() {
		trace := &httptrace.ClientTrace{
			GotConn: func(connInfo httptrace.GotConnInfo) {
				remoteAddr = connInfo.Conn.RemoteAddr()
				localAddr = connInfo.Conn.LocalAddr()
				gotConn.Close()
			},
		}

		// in case we hit an error, we want to unblock this part
		defer gotConn.Close()

		ctx = httptrace.WithClientTrace(ctx, trace)

		req, err := http.NewRequestWithContext(
			ctx,
			"GET",
			baseURL,
			nil,
		)
		if err != nil {
			errors.LogInfoInner(ctx, err, "failed to construct download http request")
			gotDownResponse.Close()
			return
		}

		req.Header = c.transportConfig.GetRequestHeader()

		response, err := c.client.Do(req)
		gotConn.Close()
		if err != nil {
			errors.LogInfoInner(ctx, err, "failed to send download http request")
			gotDownResponse.Close()
			return
		}

		if response.StatusCode != 200 {
			response.Body.Close()
			errors.LogInfo(ctx, "invalid status code on download:", response.Status)
			gotDownResponse.Close()
			return
		}

		downResponse = response.Body
		gotDownResponse.Close()
	}()

	<-gotConn.Wait()

	lazyDownload := &LazyReader{
		CreateReader: func() (io.Reader, error) {
			<-gotDownResponse.Wait()
			if downResponse == nil {
				return nil, errors.New("downResponse failed")
			}
			return downResponse, nil
		},
	}

	// workaround for https://github.com/quic-go/quic-go/issues/2143 --
	// always cancel request context so that Close cancels any Read.
	// Should then match the behavior of http2 and http1.
	reader := downloadBody{
		lazyDownload,
		ctxCancel,
	}

	return reader, remoteAddr, localAddr, nil
}

func (c *DefaultDialerClient) SendUploadRequest(ctx context.Context, url string, payload io.ReadWriteCloser, contentLength int64) error {
	req, err := http.NewRequestWithContext(ctx, "POST", url, payload)
	if err != nil {
		return err
	}
	req.ContentLength = contentLength
	req.Header = c.transportConfig.GetRequestHeader()

	if c.httpVersion != "1.1" {
		resp, err := c.client.Do(req)
		if err != nil {
			return err
		}

		defer resp.Body.Close()

		if resp.StatusCode != 200 {
			return errors.New("bad status code:", resp.Status)
		}
	} else {
		// stringify the entire HTTP/1.1 request so it can be
		// safely retried. if instead req.Write is called multiple
		// times, the body is already drained after the first
		// request
		requestBuff := new(bytes.Buffer)
		common.Must(req.Write(requestBuff))

		var uploadConn any
		var h1UploadConn *H1Conn

		for {
			uploadConn = c.uploadRawPool.Get()
			newConnection := uploadConn == nil
			if newConnection {
				newConn, err := c.dialUploadConn(context.WithoutCancel(ctx))
				if err != nil {
					return err
				}
				h1UploadConn = NewH1Conn(newConn)
				uploadConn = h1UploadConn
			} else {
				h1UploadConn = uploadConn.(*H1Conn)

				// TODO: Replace 0 here with a config value later
				// Or add some other condition for optimization purposes
				if h1UploadConn.UnreadedResponsesCount > 0 {
					resp, err := http.ReadResponse(h1UploadConn.RespBufReader, req)
					if err != nil {
						return fmt.Errorf("error while reading response: %s", err.Error())
					}
					if resp.StatusCode != 200 {
						return fmt.Errorf("got non-200 error response code: %d", resp.StatusCode)
					}
				}
			}

			_, err := h1UploadConn.Write(requestBuff.Bytes())
			// if the write failed, we try another connection from
			// the pool, until the write on a new connection fails.
			// failed writes to a pooled connection are normal when
			// the connection has been closed in the meantime.
			if err == nil {
				break
			} else if newConnection {
				return err
			}
		}

		c.uploadRawPool.Put(uploadConn)
	}

	return nil
}

type downloadBody struct {
	io.Reader
	cancel context.CancelFunc
}

func (c downloadBody) Close() error {
	c.cancel()
	return nil
}

type WaitReadCloser struct {
	Wait chan struct{}
	io.ReadCloser
}

func (w *WaitReadCloser) Set(rc io.ReadCloser) {
	w.ReadCloser = rc
	defer func() {
		if recover() != nil {
			rc.Close()
		}
	}()
	close(w.Wait)
}

func (w *WaitReadCloser) Read(b []byte) (int, error) {
	if w.ReadCloser == nil {
		if <-w.Wait; w.ReadCloser == nil {
			return 0, io.ErrClosedPipe
		}
	}
	return w.ReadCloser.Read(b)
}

func (w *WaitReadCloser) Close() error {
	if w.ReadCloser != nil {
		return w.ReadCloser.Close()
	}
	defer func() {
		if recover() != nil && w.ReadCloser != nil {
			w.ReadCloser.Close()
		}
	}()
	close(w.Wait)
	return nil
}