/*

Copyright 2017 Mikael Berthe

Licensed under the MIT license.  Please see the LICENSE file is this directory.

*/

package madon

import (

	"encoding/json"

	"errors"

	"fmt"

	"net/url"

	"strings"

	"github.com/gorilla/websocket"

)

// StreamEvent contains a single event from the streaming API

type StreamEvent struct {

	Event string      // Name of the event (error, update, notification or delete)

	Data  interface{} // Status, Notification or status ID

	Error error       // Error message from the StreamListener

}

// openStream opens a stream URL and returns an http.Response

// Note that the caller should close the connection when it's done reading

// the stream.

// The stream name can be "user", "local", "public" or "hashtag".

// When it is "hashtag", the hashTag argument cannot be empty.

func (mc *Client) openStream(streamName, hashTag string) (*websocket.Conn, error) {

	var tag string

	switch streamName {

	case "user", "public", "public:local":

	case "hashtag":

		if hashTag == "" {

			return nil, ErrInvalidParameter

		}

		tag = hashTag

	default:

		return nil, ErrInvalidParameter

	}

	if !strings.HasPrefix(mc.APIBase, "http") {

		return nil, errors.New("cannot create Websocket URL: unexpected API base URL")

	}

	// Build streaming websocket URL

	u, err := url.Parse("ws" + mc.APIBase[4:] + "/streaming/")

	if err != nil {

		return nil, errors.New("cannot create Websocket URL: " + err.Error())

	}

	urlParams := url.Values{}

	urlParams.Add("stream", streamName)

	urlParams.Add("access_token", mc.UserToken.AccessToken)

	if tag != "" {

		urlParams.Add("tag", tag)

	}

	u.RawQuery = urlParams.Encode()

	c, _, err := websocket.DefaultDialer.Dial(u.String(), nil)

	return c, err

}

// readStream reads from the http.Response and sends events to the events channel

// It stops when the connection is closed or when the stopCh channel is closed.

// The foroutine will close the doneCh channel when it terminates.

func (mc *Client) readStream(events chan<- StreamEvent, stopCh <-chan bool, doneCh chan bool, c *websocket.Conn) {

	defer c.Close()

	defer close(doneCh)

	go func() {

		select {

		case <-stopCh:

			// Close connection

			c.WriteMessage(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseNormalClosure, ""))

		case <-doneCh:

			// Leave

		}

	}()

	for {

		var msg struct {

			Event   string

			Payload interface{}

		}

		err := c.ReadJSON(&msg)

		if err != nil {

			if strings.Contains(err.Error(), "close 1000 (normal)") {

				break // Connection properly closed

			}

			e := fmt.Errorf("read error: %v", err)

			events <- StreamEvent{Event: "error", Error: e}

			break

		}

		var obj interface{}

		// Decode API object

		switch msg.Event {

		case "update":

			strPayload, ok := msg.Payload.(string)

			if !ok {

				e := fmt.Errorf("could not decode status: payload isn't a string")

				events <- StreamEvent{Event: "error", Error: e}

				continue

			}

			var s Status

			if err := json.Unmarshal([]byte(strPayload), &s); err != nil {

				e := fmt.Errorf("could not decode status: %v", err)

				events <- StreamEvent{Event: "error", Error: e}

				continue

			}

			obj = s

		case "notification":

			strPayload, ok := msg.Payload.(string)

			if !ok {

				e := fmt.Errorf("could not decode notification: payload isn't a string")

				events <- StreamEvent{Event: "error", Error: e}

				continue

			}

			var notif Notification

			if err := json.Unmarshal([]byte(strPayload), &notif); err != nil {

				e := fmt.Errorf("could not decode notification: %v", err)

				events <- StreamEvent{Event: "error", Error: e}

				continue

			}

			obj = notif

		case "delete":

			floatPayload, ok := msg.Payload.(float64)

			if !ok {

				e := fmt.Errorf("could not decode deletion: payload isn't a number")

				events <- StreamEvent{Event: "error", Error: e}

				continue

			}

		default:

			e := fmt.Errorf("unhandled event '%s'", msg.Event)

			events <- StreamEvent{Event: "error", Error: e}

			continue

		}

		// Send event to the channel

		events <- StreamEvent{Event: msg.Event, Data: obj}

	}

}

// StreamListener listens to a stream from the Mastodon server

// The stream 'name' can be "user", "local", "public" or "hashtag".

// For 'hashtag', the hashTag argument cannot be empty.

// The events are sent to the events channel (the errors as well).

// The streaming is terminated if the 'stopCh' channel is closed.

// The 'doneCh' channel is closed if the connection is closed by the server.

// Please note that this method launches a goroutine to listen to the events.

func (mc *Client) StreamListener(name, hashTag string, events chan<- StreamEvent, stopCh <-chan bool, doneCh chan bool) error {

	if mc == nil {

		return ErrUninitializedClient

	}

	conn, err := mc.openStream(name, hashTag)

	if err != nil {

		return err

	}

	go mc.readStream(events, stopCh, doneCh, conn)

	return nil

}