package gateway

import (
	"context"
	"encoding/json"
	"fmt"
	"jinx/pkg/discord/events"
	"jinx/pkg/libs/cancellablewebsocket"
	"net/http"

	"github.com/gorilla/websocket"
	"github.com/rs/zerolog"
)

type Gateway interface {
	Start(ctx context.Context, url string, token string) error
	Close() error

	Heartbeat() error
}

var _ Gateway = &GatewayImpl{}

type GatewayImpl struct {
	ctx          context.Context
	logger       *zerolog.Logger
	conn         *cancellablewebsocket.CancellableWebSocket
	heartbeat    Heartbeat
	eventHandler events.EventHandler
	lastSeq      uint64
}

func New(logger *zerolog.Logger, eventHandler events.EventHandler) *GatewayImpl {
	gateway := &GatewayImpl{
		ctx:          nil,
		logger:       logger,
		conn:         nil,
		eventHandler: eventHandler,
		heartbeat:    nil,
		lastSeq:      0,
	}

	// Cycle dependency, is this the best way to do this?
	heartbeat := NewHeartbeat(logger, gateway)
	gateway.heartbeat = heartbeat

	return gateway
}

func (g *GatewayImpl) Start(ctx context.Context, url string, token string) error {
	connectHeader := http.Header{}
	conn, err := cancellablewebsocket.Dial(websocket.DefaultDialer, ctx, url, connectHeader)
	if err != nil {
		return err
	}

	g.conn = conn
	g.ctx = ctx

	hello, err := g.hello()
	if err != nil {
		return err
	}

	g.heartbeat.Start(ctx, hello.HeartbeatInterval)

	if err = g.identify(token); err != nil {
		return err
	}

	go g.listen()

	return nil
}

func (g *GatewayImpl) Close() error {
	return g.conn.Close()
}

func (g *GatewayImpl) Heartbeat() error {
	msg := Payload[uint64]{
		Op:   OP_HEARTBEAT,
		Data: g.lastSeq,
	}

	return g.send(msg)
}

func (g *GatewayImpl) hello() (HelloEvent, error) {
	var msg Payload[HelloEvent]
	if err := receive(g, &msg); err != nil {
		return HelloEvent{}, err
	}

	if msg.Op != OP_HELLO {
		return HelloEvent{}, fmt.Errorf("expected opcode %d, got %d", OP_HELLO, msg.Op)
	}

	return msg.Data, nil
}

func (g *GatewayImpl) identify(token string) error {
	msg := Payload[IdentifyCmd]{
		Op: OP_IDENTIFY,
		Data: IdentifyCmd{
			Token:   token,
			Intents: 13991,
			Properties: IdentifyProperties{
				OS:      "linux",
				Browser: "jinx",
				Device:  "jinx",
			},
		},
		Sequence: 0,
	}

	if err := g.send(msg); err != nil {
		return err
	}

	var res Payload[ReadyEvent]
	if err := receive(g, &res); err != nil {
		return err
	}

	g.logger.Debug().Msgf("identify response payload: %+v", res)

	if res.Op != OP_DISPATCH {
		return fmt.Errorf("expected opcode %d, got %d", OP_DISPATCH, res.Op)
	}

	if res.EventName != "READY" {
		return fmt.Errorf("expected event name %s, got %s", "READY", res.EventName)
	}

	return nil
}

func (g *GatewayImpl) listen() {
	for {
		var msg Payload[json.RawMessage]
		if err := receive(g, &msg); err != nil {
			g.logger.Error().Err(err).Msgf("error reading message")
			continue
		}

		select {
		case <-g.ctx.Done():
			return
		default:
			g.onEvent(msg)
		}
	}
}

func (g *GatewayImpl) onEvent(msg Payload[json.RawMessage]) error {
	switch msg.Op {
	case OP_HEARTBEAT_ACK:
		g.heartbeat.Ack()
	case OP_HEARTBEAT:
		g.heartbeat.ForceHeartbeat()
	case OP_DISPATCH:
		return g.onDispatch(msg.EventName, msg.Data)
	default:
		g.logger.Warn().Msgf("received unknown opcode: %d", msg.Op)
	}

	return nil
}

func (g *GatewayImpl) onDispatch(eventName string, body json.RawMessage) error {
	switch eventName {
	case "MESSAGE_CREATE":
		var payload MessageCreateEvent
		if err := json.Unmarshal(body, &payload); err != nil {
			return err
		}

		g.eventHandler.Fire(events.MESSAGE, payload)
	default:
		g.logger.Warn().Msgf("received unknown event: %s", eventName)
	}

	return nil
}

func (g *GatewayImpl) send(payload any) error {
	return g.conn.WriteJSON(payload)
}

func receive[D any](g *GatewayImpl, res *Payload[D]) error {
	err := g.conn.ReadJSON(&res)
	if err != nil {
		return err
	}

	if res.Sequence != 0 {
		g.lastSeq = res.Sequence
	}

	return nil
}