package redirect

import (
	"bytes"
	"context"
	"fmt"
	"net"
	"time"

	"github.com/go-gost/core/handler"
	md "github.com/go-gost/core/metadata"
	"github.com/go-gost/core/observer/stats"
	"github.com/go-gost/core/recorder"
	xbypass "github.com/go-gost/x/bypass"
	ctxvalue "github.com/go-gost/x/ctx"
	xnet "github.com/go-gost/x/internal/net"
	rate_limiter "github.com/go-gost/x/limiter/rate"
	xstats "github.com/go-gost/x/observer/stats"
	stats_wrapper "github.com/go-gost/x/observer/stats/wrapper"
	xrecorder "github.com/go-gost/x/recorder"
	"github.com/go-gost/x/registry"
)

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

type redirectHandler 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)
	}

	return &redirectHandler{
		options: options,
	}
}

func (h *redirectHandler) 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
}

func (h *redirectHandler) 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(),
		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())

	pStats := xstats.Stats{}
	conn = stats_wrapper.WrapConn(conn, &pStats)

	defer func() {
		if err != nil {
			ro.Err = err.Error()
		}
		ro.Duration = time.Since(start)
		ro.InputBytes = pStats.Get(stats.KindInputBytes)
		ro.OutputBytes = pStats.Get(stats.KindOutputBytes)
		if err := ro.Record(ctx, h.recorder.Recorder); err != nil {
			log.Error("record: %v", err)
		}

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

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

	dstAddr := conn.LocalAddr()
	ro.Network = dstAddr.Network()
	ro.Host = dstAddr.String()

	log = log.WithFields(map[string]any{
		"dst":  fmt.Sprintf("%s/%s", dstAddr, dstAddr.Network()),
		"host": dstAddr.String(),
	})

	log.Debugf("%s >> %s", conn.RemoteAddr(), dstAddr)

	if h.options.Bypass != nil &&
		h.options.Bypass.Contains(ctx, dstAddr.Network(), dstAddr.String()) {
		log.Debug("bypass: ", dstAddr)
		return xbypass.ErrBypass
	}

	var buf bytes.Buffer
	cc, err := h.options.Router.Dial(ctxvalue.ContextWithBuffer(ctx, &buf), dstAddr.Network(), dstAddr.String())
	ro.Route = buf.String()
	if err != nil {
		log.Error(err)
		return err
	}
	defer cc.Close()

	t := time.Now()
	log.Infof("%s <-> %s", conn.RemoteAddr(), dstAddr)
	xnet.Transport(conn, cc)
	log.WithFields(map[string]any{
		"duration": time.Since(t),
	}).Infof("%s >-< %s", conn.RemoteAddr(), dstAddr)

	return nil
}

func (h *redirectHandler) 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
}
