package commands

import (
	"context"
	"fmt"
	"strings"

	"github.com/disgoorg/disgo/discord"
	"github.com/disgoorg/disgo/events"
	"github.com/disgoorg/disgolink/v4/disgolink"
	"github.com/disgoorg/disgolink/v4/lavalink"

	"discord-music-bot/internal/music"
)

type PlayCommand struct {
	deps *Dependencies
}

func NewPlayCommand(deps *Dependencies) *PlayCommand {
	return &PlayCommand{deps: deps}
}

func (c *PlayCommand) Definition() discord.ApplicationCommandCreate {
	return discord.SlashCommandCreate{
		Name:        "play",
		Description: "Plays a song or playlist, or adds it to the queue",
		Options: []discord.ApplicationCommandOption{
			discord.ApplicationCommandOptionString{
				Name:        "query",
				Description: "Song name, song URL, or playlist URL",
				Required:    true,
			},
		},
	}
}

func (c *PlayCommand) Execute(ctx context.Context, event *events.ApplicationCommandInteractionCreate) error {
	gid, ok := guildID(event)
	if !ok {
		return guildOnlyError(event)
	}

	channelID, ok := memberVoiceChannel(c.deps.Discord, gid, event.User().ID)
	if !ok {
		return rejectEphemeral(event, "Join a voice channel first.")
	}

	if allowed, reason := ensureCanControlPlayback(c.deps.Discord, gid, event.User().ID); !allowed {
		return rejectEphemeral(event, reason)
	}

	query := event.SlashCommandInteractionData().String("query")

	if err := event.DeferCreateMessage(false); err != nil {
		return fmt.Errorf("deferring response: %w", err)
	}

	loaded, err := loadTracks(ctx, c.deps.Lavalink, query)
	if err != nil {
		return c.followUp(event, err.Error())
	}

	if err := c.deps.Discord.UpdateVoiceState(ctx, gid, &channelID, false, false); err != nil {
		return c.followUp(event, fmt.Sprintf("Could not join your voice channel: %s", err))
	}

	result, err := c.deps.Music.Guild(gid).EnqueueMany(ctx, loaded.tracks)
	if err != nil {
		return c.followUp(event, fmt.Sprintf("Could not play that track: %s", err))
	}

	return c.followUp(event, playSummary(loaded, result))
}

func playSummary(loaded trackLoadResult, result music.EnqueueResult) string {
	if len(loaded.tracks) <= 1 {
		title := "that track"
		if len(loaded.tracks) == 1 {
			title = loaded.tracks[0].Info.Title
		}
		if result.PlayingNow {
			return fmt.Sprintf("Now playing: **%s**", title)
		}
		return fmt.Sprintf("Added to queue: **%s**", title)
	}

	name := loaded.playlistName
	if name == "" {
		name = "the playlist"
	}

	if result.PlayingNow {
		return fmt.Sprintf("Now playing **%s** and queued %d more track(s) from **%s**.",
			result.Started.Info.Title, result.Queued, name)
	}
	return fmt.Sprintf("Added %d tracks from **%s** to the queue.", len(loaded.tracks), name)
}

func (c *PlayCommand) followUp(event *events.ApplicationCommandInteractionCreate, content string) error {
	_, err := event.Client().Rest.UpdateInteractionResponse(event.ApplicationID(), event.Token(), discord.NewMessageUpdate().WithContent(content))
	return err
}

func normalizeQuery(query string) string {
	if strings.HasPrefix(query, "http://") || strings.HasPrefix(query, "https://") {
		return query
	}
	return "ytsearch:" + query
}

type trackLoadResult struct {
	tracks       []lavalink.Track
	playlistName string
}

func loadTracks(ctx context.Context, lavalinkClient *disgolink.Client, query string) (trackLoadResult, error) {
	node := lavalinkClient.BestNode()
	if node == nil {
		return trackLoadResult{}, fmt.Errorf("no music node is available right now")
	}

	type outcome struct {
		result trackLoadResult
		err    error
	}
	outcomeCh := make(chan outcome, 1)

	node.Rest.LoadTracksHandler(ctx, normalizeQuery(query), disgolink.NewTrackLoadingResultHandler(
		func(track lavalink.Track) {
			outcomeCh <- outcome{result: trackLoadResult{tracks: []lavalink.Track{track}}}
		},
		func(playlist lavalink.Playlist) {
			if len(playlist.Tracks) == 0 {
				outcomeCh <- outcome{err: fmt.Errorf("that playlist is empty")}
				return
			}
			outcomeCh <- outcome{result: trackLoadResult{
				tracks:       playlist.Tracks,
				playlistName: playlist.Info.Name,
			}}
		},
		func(tracks []lavalink.Track) {
			if len(tracks) == 0 {
				outcomeCh <- outcome{err: fmt.Errorf("no results found for %q", query)}
				return
			}
			outcomeCh <- outcome{result: trackLoadResult{tracks: []lavalink.Track{tracks[0]}}}
		},
		func() {
			outcomeCh <- outcome{err: fmt.Errorf("no results found for %q", query)}
		},
		func(err error) {
			outcomeCh <- outcome{err: fmt.Errorf("failed to load track: %w", err)}
		},
	))

	res := <-outcomeCh
	return res.result, res.err
}