package websocket

import (
	"context"
	"encoding/json"
	"errors"

	"go.fifitido.net/twitch/api/eventsub"
	"go.fifitido.net/twitch/eventsub/websocket/messages"
	"nhooyr.io/websocket"
)

const (
	DefaultEventSubEndpoint = "wss://eventsub.wss.twitch.tv/ws"
)

var (
	ErrNotConnected = errors.New("not connected")
)

type Transport struct {
	ctx    context.Context
	cancel context.CancelFunc
	opts   *TransportOptions

	sessionId string
	conn      *websocket.Conn
}

func New(parentCtx context.Context, opts *TransportOptions) *Transport {
	ctx, cancel := context.WithCancel(parentCtx)

	if opts == nil {
		opts = &TransportOptions{}
	}

	return &Transport{
		ctx:    ctx,
		cancel: cancel,
		opts:   opts,
	}
}

// ApiTransport implements eventsub.Transport.
func (t *Transport) ApiTransport() *eventsub.Transport {
	return &eventsub.Transport{
		Method:    "websocket",
		SessionID: &t.sessionId,
	}
}

func (t *Transport) Close() error {
	t.sessionId = ""

	if t.conn != nil {
		if err := t.conn.Close(websocket.StatusNormalClosure, ""); err != nil {
			return err
		}
	}

	t.cancel()

	return nil
}

func (t *Transport) readLoop() chan *messages.Message {
	c := make(chan *messages.Message)
	go func(c chan *messages.Message) {
		for {
			_, raw, err := t.conn.Read(t.ctx)
			if err != nil {
				return
			}

			var msg *messages.Message
			if err := json.Unmarshal(raw, &msg); err != nil {
				return
			}

			c <- msg
		}
	}(c)
	return c
}

func (t *Transport) Run() error {
	addr := DefaultEventSubEndpoint
	if t.opts.Address != nil {
		addr = *t.opts.Address
	}

	var err error
	t.conn, _, err = websocket.Dial(t.ctx, addr, nil)
	if err != nil {
		return err
	}
	defer t.conn.CloseNow()

	msgC := t.readLoop()

	for {
		select {
		case msg := <-msgC:
			if err := t.handleMsg(msg); err != nil {
				return err
			}
		case <-t.ctx.Done():
			return t.Close()
		}
	}
}

func (t *Transport) Start() {
	go func() {
		if err := t.Run(); err != nil {
			panic(err)
		}
	}()
}