package gavalink

import (
	"context"
	"encoding/json"
	"fmt"
	"github.com/valyala/fastjson"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

	"github.com/gorilla/websocket"
)

// NodeConfig configures a Lavalink Node
type NodeConfig struct {
	// Node identifier (uuid, hostname, etc)
	Identifier string

	// REST is the host where Lavalink's REST server runs
	//
	// This value is expected without a trailing slash, e.g. like
	// `http://localhost:2333`
	REST string

	// WebSocket is the host where Lavalink's WebSocket server runs
	//
	// This value is expected without a trailing slash, e.g. like
	// `http://localhost:8012`
	WebSocket string

	// Password is the expected Authorization header for the Node
	Password string
}

// Node wraps a Lavalink Node
type Node struct {
	config  NodeConfig
	stats   *RemoteStats
	manager *Lavalink
	wsConn  *websocket.Conn
	client  *http.Client
}

type RemoteStats struct {
	Op            string       `json:"op"`
	Players       int          `json:"players"`
	ActivePlayers int          `json:"playingPlayers"`
	Uptime        int64        `json:"uptime"`
	Memory        *MemoryStats `json:"memory"`
	Cpu           *CpuStats    `json:"cpu"`
	Frames        *FrameStats  `json:"frameStats"`
}

type MemoryStats struct {
	Free        uint64 `json:"free"`
	Used        uint64 `json:"used"`
	Allocated   uint64 `json:"allocated"`
	Reserveable uint64 `json:"reserveable"`
}

type CpuStats struct {
	Cores        int     `json:"cores"`
	SystemLoad   float64 `json:"systemLoad"`
	LavalinkLoad float64 `json:"lavalinkLoad"`
}

type FrameStats struct {
	Sent    int `json:"sent"`
	Nulled  int `json:"nulled"`
	Deficit int `json:"deficit"`
}

// Opens the connection to the Lavalink server
func (node *Node) open(ctx context.Context) error {
	header := http.Header{}

	header.Set("User-Agent", gavalinkUserAgent())
	header.Set("Authorization", node.config.Password)
	header.Set("Num-Shards", strconv.Itoa(node.manager.shards))
	header.Set("User-Id", node.manager.userID)

	if node.manager.capabilities != nil {
		v := make([]string, 0)

		for k, vals := range node.manager.capabilities {
			b, err := json.Marshal(vals)

			if err != nil {
				continue
			}

			v = append(v, k+"="+string(b))
		}

		header.Set("Capabilities", strings.Join(v, ";"))
	}

	ws, resp, err := websocket.DefaultDialer.DialContext(ctx, node.config.WebSocket, header)

	if err != nil {
		return err
	}

	vstr := resp.Header.Get("Lavalink-Major-Version")

	v, err := strconv.Atoi(vstr)

	if err != nil {
		return err
	}

	if v < 3 {
		return errInvalidVersion
	}

	node.wsConn = ws
	go node.listen()

	Log.Println("node", node.config.WebSocket, "opened")

	return nil
}

func (node *Node) stop() {
	// someone already stopped this
	if node.wsConn == nil {
		return
	}

	_ = node.wsConn.Close()
}

func (node *Node) listen() {
	var p fastjson.Parser

	for {
		msgType, msg, err := node.wsConn.ReadMessage()

		if err != nil {
			Log.Println(err)
			// try to reconnect
			oerr := node.open(context.Background())

			if oerr != nil {
				Log.Println("node", node.config.WebSocket, "failed and could not reconnect, destroying.", err, oerr)
				node.manager.removeNode(node)
				return
			}

			Log.Println("node", node.config.WebSocket, "reconnected")
			return
		}

		if msgType != websocket.TextMessage {
			continue
		}

		v, err := p.ParseBytes(msg)

		if err != nil {
			continue
		}

		node.onEvent(v, msg)
	}
}

// Handle an event from the node
func (node *Node) onEvent(v *fastjson.Value, msg []byte) error {
	op := jsonStringValue(v, "op")

	switch op {
	case opStats:
		node.stats = &RemoteStats{}

		err := json.Unmarshal(msg, &node.stats)

		if err != nil {
			return err
		}
	case opPlayerUpdate:
		player, err := node.manager.GetPlayer(jsonStringValue(v, "guildId"))

		if err != nil {
			return err
		}

		player.time = v.GetInt("state", "time")
		player.position = v.GetInt("state", "position")
	case opEvent:
		player, err := node.manager.GetPlayer(jsonStringValue(v, "guildId"))
		if err != nil {
			return err
		}

		track := jsonStringValue(v, "track")

		switch jsonStringValue(v, "type") {
		case eventTrackStart:
			player.track = track

			node.manager.handle(player, eventTrackStart, &TrackStart{
				Track: track,
			})
		case eventTrackEnd:
			player.track = ""

			node.manager.handle(player, eventTrackEnd, &TrackEnd{
				Track:  track,
				Reason: jsonStringValue(v, "reason"),
			})
		case eventTrackException:
			ex := &TrackException{
				Track: track,
				Error: jsonStringValue(v, "error"),
			}

			if obj := v.Get("exception"); obj != nil {
				var exception Exception
				jsonUnmarshal(obj, &exception)
				ex.Exception = exception
			}

			node.manager.handle(player, eventTrackException, ex)
		case eventTrackStuck:
			node.manager.handle(player, eventTrackStuck, &TrackStuck{
				Track:     track,
				Threshold: time.Duration(v.GetInt("thresholdMs")) * time.Millisecond,
			})
		case eventVoiceProcessed:
			data := &VoiceProcessingData{
				node:   node,
				UserID: jsonStringValue(v, "userId"),
				URL:    fmt.Sprintf("%s/audio/%s", node.config.REST, track),
				File:   track,
			}

			node.manager.handle(player, eventVoiceProcessed, &VoiceProcessed{
				Data:     data,
				Hotword:  v.GetBool("hotword"),
				Override: v.GetBool("override"),
			})
		}

		return nil
	default:
		return errUnknownPayload
	}

	return nil
}

// CreatePlayer creates an audio player on this node
func (node *Node) CreatePlayer(guildID string, sessionID string, event VoiceServerUpdate) (*Player, error) {
	msg := voiceUpdateMessage{
		Op:        opVoiceUpdate,
		GuildID:   guildID,
		SessionID: sessionID,
		Event:     &event,
	}

	err := node.writeMessage(msg)

	if err != nil {
		return nil, err
	}

	player := &Player{
		guildID:               guildID,
		sessionID:             sessionID,
		manager:               node.manager,
		node:                  node,
		vol:                   100,
		lastVoiceServerUpdate: event,
	}

	node.manager.playersMu.Lock()
	defer node.manager.playersMu.Unlock()
	node.manager.players[guildID] = player

	return player, nil
}

// LoadTracks queries lavalink to return a Tracks object
//
// query should be a valid Lavaplayer query, including but not limited to:
// - A direct media URI
// - A direct Youtube /watch URI
// - A search query, prefixed with ytsearch: or scsearch:
//
// See the Lavaplayer Source Code for all valid options.
func (node *Node) LoadTracks(query string) (*Tracks, error) {
	v := url.Values{}
	v.Set("identifier", query)

	req, err := http.NewRequest(http.MethodGet, fmt.Sprintf("%s/loadtracks?%s", node.config.REST, v.Encode()), nil)

	if err != nil {
		return nil, err
	}

	req.Header.Set("User-Agent", gavalinkUserAgent())
	req.Header.Set("Authorization", node.config.Password)

	resp, err := node.client.Do(req)

	if err != nil {
		return nil, err
	}

	tracks := new(Tracks)

	if err := json.NewDecoder(resp.Body).Decode(&tracks); err != nil {
		return nil, err
	}

	return tracks, nil
}

// Write a JSON message via the node's websocket connection
func (node *Node) writeMessage(v interface{}) error {
	return node.wsConn.WriteJSON(v)
}