package broker

import (
	"bytes"
	"context"

	"git.asio.asia/nixevol/NixMsg/internal/app/port"
	mqtt "github.com/mochi-mqtt/server/v2"
	"github.com/mochi-mqtt/server/v2/packets"
)

type nixHook struct {
	mqtt.HookBase
	b *Broker
}

func (h *nixHook) ID() string { return "nixmsg" }

func (h *nixHook) Provides(b byte) bool {
	return bytes.Contains([]byte{
		mqtt.OnConnect,
		mqtt.OnConnectAuthenticate,
		mqtt.OnACLCheck,
		mqtt.OnPublish,
		mqtt.OnPublishDropped,
		mqtt.OnSessionEstablished,
		mqtt.OnDisconnect,
		mqtt.OnQosComplete,
	}, []byte{b})
}

func (h *nixHook) OnConnect(cl *mqtt.Client, pk packets.Packet) error {
	endpointID := string(pk.Connect.Username)
	if endpointID == "" {
		endpointID = pk.Connect.ClientIdentifier
	}
	remoteIP := remoteIPOf(cl)

	st := &connState{
		connID:        randomConnID(),
		endpointID:    endpointID,
		transport:     transportOf(cl),
		remoteIP:      remoteIP,
		client:        cl,
		maxPacketSize: pk.Properties.MaximumPacketSize,
	}

	// 心跳校正：超出 10–600 秒就改写 Keepalive 并设 ServerKeepalive
	ka := pk.Connect.Keepalive
	if ka < keepaliveMin || ka > keepaliveMax {
		if ka < keepaliveMin {
			ka = keepaliveMin
		}
		if ka > keepaliveMax {
			ka = keepaliveMax
		}
		cl.State.Keepalive = ka
		cl.State.ServerKeepalive = true
	}

	res, err := h.b.auth.Authenticate(context.Background(), endpointID, pk.Connect.Password, remoteIP)
	if err != nil {
		st.authErr = err
		h.rememberPending(cl, st)
		return err // mochi 不回 CONNACK，直接断开
	}
	st.authOK = res.OK
	st.sessionToken = res.SessionToken
	h.rememberPending(cl, st)
	return nil
}

func (h *nixHook) rememberPending(cl *mqtt.Client, st *connState) {
	h.b.connsMu.Lock()
	h.b.byClient[cl] = st
	h.b.connsMu.Unlock()
}

func (h *nixHook) OnConnectAuthenticate(cl *mqtt.Client, _ packets.Packet) bool {
	h.b.connsMu.RLock()
	st := h.b.byClient[cl]
	h.b.connsMu.RUnlock()
	if st == nil {
		return false
	}
	// 内部故障已在 OnConnect 返回 error；此处只反映业务上的拒绝
	return st.authOK
}

func (h *nixHook) OnACLCheck(cl *mqtt.Client, topic string, write bool) bool {
	h.b.connsMu.RLock()
	st := h.b.byClient[cl]
	h.b.connsMu.RUnlock()
	if st == nil || st.endpointID == "" {
		return false
	}
	up := upTopic(st.endpointID)
	down := downTopic(st.endpointID)
	if write {
		return topic == up
	}
	return topic == down
}

func (h *nixHook) OnPublish(cl *mqtt.Client, pk packets.Packet) (packets.Packet, error) {
	h.b.connsMu.RLock()
	st := h.b.byClient[cl]
	h.b.connsMu.RUnlock()
	if st == nil {
		return pk, packets.CodeSuccessIgnore
	}
	payload := append([]byte(nil), pk.Payload...)
	info := port.ConnInfo{
		ConnID:        st.connID,
		EndpointID:    st.endpointID,
		Transport:     st.transport,
		RemoteIP:      st.remoteIP,
		SessionToken:  st.sessionToken,
		MaxPacketSize: st.maxPacketSize,
	}
	h.b.enqueueUplink(st.endpointID, info, payload)
	return pk, packets.CodeSuccessIgnore
}

func (h *nixHook) OnPublishDropped(cl *mqtt.Client, pk packets.Packet) {
	h.b.log.Debug("publish dropped", "client", cl.ID, "topic", pk.TopicName, "size", len(pk.Payload))
}

func (h *nixHook) OnSessionEstablished(cl *mqtt.Client, _ packets.Packet) {
	h.b.connsMu.Lock()
	st := h.b.byClient[cl]
	if st != nil {
		h.b.current[st.endpointID] = st
	}
	h.b.connsMu.Unlock()
	if st == nil {
		return
	}
	info := port.ConnInfo{
		ConnID:        st.connID,
		EndpointID:    st.endpointID,
		Transport:     st.transport,
		RemoteIP:      st.remoteIP,
		SessionToken:  st.sessionToken,
		MaxPacketSize: st.maxPacketSize,
	}
	_ = h.b.uplink.OnSessionEstablished(context.Background(), info)
}

func (h *nixHook) OnDisconnect(cl *mqtt.Client, err error, _ bool) {
	h.b.connsMu.Lock()
	st := h.b.byClient[cl]
	delete(h.b.byClient, cl)
	if st != nil && h.b.current[st.endpointID] == st {
		delete(h.b.current, st.endpointID)
	}
	h.b.connsMu.Unlock()
	if st == nil {
		return
	}
	h.b.releaseAllLarge(st)

	reason := port.DisconnectNormal
	if err != nil {
		if code, ok := err.(packets.Code); ok {
			switch code.Code {
			case packets.ErrSessionTakenOver.Code:
				reason = port.DisconnectTakenOver
			case packets.ErrAdministrativeAction.Code:
				reason = port.DisconnectKicked
			}
		}
	}
	info := port.ConnInfo{
		ConnID:        st.connID,
		EndpointID:    st.endpointID,
		Transport:     st.transport,
		RemoteIP:      st.remoteIP,
		SessionToken:  st.sessionToken,
		MaxPacketSize: st.maxPacketSize,
	}
	h.b.uplink.OnDisconnect(context.Background(), info, reason)
}

func (h *nixHook) OnQosComplete(cl *mqtt.Client, pk packets.Packet) {
	if len(pk.Payload) <= largeFrameBytes {
		return
	}
	h.b.connsMu.RLock()
	st := h.b.byClient[cl]
	h.b.connsMu.RUnlock()
	if st == nil {
		return
	}
	h.b.releaseOneLarge(st)
}