package sni

import (
	"bufio"
	"context"
	"errors"
	"net"
	"time"

	"github.com/go-gost/core/handler"
	md "github.com/go-gost/core/metadata"
	"github.com/go-gost/core/recorder"
	ctxvalue "github.com/go-gost/x/ctx"
	xio "github.com/go-gost/x/internal/io"
	"github.com/go-gost/x/internal/util/sniffing"
	rate_limiter "github.com/go-gost/x/limiter/rate"
	xrecorder "github.com/go-gost/x/recorder"
	"github.com/go-gost/x/registry"
)

const (
	defaultBodySize = 1024 * 1024 // 1MB
)

func init() {
	registry.HandlerRegistry().Register("sni", NewHandler)
}

type sniHandler struct {
	md       metadata
	options  handler.Options
	recorder recorder.RecorderObject
}

func NewHandler(opts ...handler.Option) handler.Handler {
	options := handler.Options{}
	for _, opt := range opts {
		opt(&options)
	}

	h := &sniHandler{
		options: options,
	}

	return h
}

func (h *sniHandler) Init(md md.Metadata) (err error) {
	if err = h.parseMetadata(md); err != nil {
		return
	}

	for _, ro := range h.options.Recorders {
		if ro.Record == xrecorder.RecorderServiceHandler {
			h.recorder = ro
			break
		}
	}

	return nil
}

func (h *sniHandler) Handle(ctx context.Context, conn net.Conn, opts ...handler.HandleOption) (err error) {
	defer conn.Close()

	start := time.Now()

	ro := &xrecorder.HandlerRecorderObject{
		Service:    h.options.Service,
		RemoteAddr: conn.RemoteAddr().String(),
		LocalAddr:  conn.LocalAddr().String(),
		Network:    "tcp",
		Time:       start,
		SID:        string(ctxvalue.SidFromContext(ctx)),
	}
	ro.ClientIP, _, _ = net.SplitHostPort(conn.RemoteAddr().String())

	log := h.options.Logger.WithFields(map[string]any{
		"remote": conn.RemoteAddr().String(),
		"local":  conn.LocalAddr().String(),
		"sid":    ctxvalue.SidFromContext(ctx),
	})

	log.Infof("%s <> %s", conn.RemoteAddr(), conn.LocalAddr())
	defer func() {
		if !ro.Time.IsZero() {
			if err != nil {
				ro.Err = err.Error()
			}
			ro.Duration = time.Since(start)
			if err := ro.Record(ctx, h.recorder.Recorder); err != nil {
				log.Errorf("record: %v", err)
			}
		}

		log.WithFields(map[string]any{
			"duration": time.Since(start),
		}).Infof("%s >< %s", conn.RemoteAddr(), conn.LocalAddr())
	}()

	if !h.checkRateLimit(conn.RemoteAddr()) {
		return rate_limiter.ErrRateLimit
	}

	br := bufio.NewReader(conn)
	proto, _ := sniffing.Sniff(ctx, br)
	ro.Proto = proto

	rw := xio.NewReadWriter(br, conn)
	switch proto {
	case sniffing.ProtoHTTP:
		ro2 := &xrecorder.HandlerRecorderObject{}
		*ro2 = *ro
		ro.Time = time.Time{}
		return h.handleHTTP(ctx, rw, ro2, log)
	case sniffing.ProtoTLS:
		return h.handleTLS(ctx, rw, ro, log)
	default:
		return errors.New("unknown traffic")
	}
}

func (h *sniHandler) checkRateLimit(addr net.Addr) bool {
	if h.options.RateLimiter == nil {
		return true
	}
	host, _, _ := net.SplitHostPort(addr.String())
	if limiter := h.options.RateLimiter.Limiter(host); limiter != nil {
		return limiter.Allow(1)
	}

	return true
}