bolt/bolt.go

package bolt

import (
	"fmt"
	"log"
	"os"
	"os/signal"
	"slices"
	"strings"
	"syscall"
	"time"

	dg "github.com/bwmarrin/discordgo"
)

const (
	TOKEN_ENV_VAR = "DISCORD_TOKEN" //label for token environment variable

	BOT_INTENTS = dg.IntentGuilds |
		dg.IntentGuildMembers |
		dg.IntentGuildPresences |
		dg.IntentMessageContent |
		dg.IntentsGuildMessages
)

// basic bot structure containing discordgo connection as well as the command map
type bolt struct {
	*dg.Session                    //holds discordgo internals
	Commands    map[string]Command //maps trigger phrase to command struct for fast lookup
	indicator   string             //the indicator used to detect whether a message is a command
}

type Bolt interface {
	Start() error
	AddCommands(cmd ...Command)
	//filtered methods
	stop() error
	messageHandler(s *dg.Session, msg *dg.MessageCreate)
	handleCommand(msg *dg.MessageCreate, s *dg.Session, server *dg.Guild, channel *dg.Channel, lg int) error
	createReply(content, message, channel, guild string) *dg.MessageSend
	getRemainingTimeout(timeout time.Time) string
	roleCheck(msg *dg.MessageCreate, s *dg.Session, run Command) (bool, error)
	timeoutCheck(msg *dg.MessageCreate, s *dg.Session, run Command) (bool, error)
}

// setup
func init() {
	//validate environment variables
	_, check := os.LookupEnv(TOKEN_ENV_VAR)
	if !check {
		log.Fatalf("the %s environment variable must be set", TOKEN_ENV_VAR)
	}
}

// create a new bolt interface
func New(opts ...Option) Bolt {
	bot, err := dg.New(fmt.Sprintf("Bot %s", os.Getenv(TOKEN_ENV_VAR)))
	if err != nil {
		log.Fatal(err)
	}
	bot.Identify.Intents = BOT_INTENTS

	b := &bolt{
		Session:  bot,
		Commands: make(map[string]Command, 0),
	}
	//set default command indicator
	b.indicator = "."

	//apply options to bolt
	for _, o := range opts {
		o(b)
	}

	return b
}

// starts the bot, commands are added and the connection to Discord is opened, this is a BLOCKING
// call that handles safe shutdown of the bot
func (b *bolt) Start() error {
	//register commands and open connection
	b.AddHandler(b.messageHandler)

	err := b.Open()
	if err != nil {
		return err
	}

	//safe shutdown handler
	sigChannel := make(chan os.Signal, 1)
	signal.Notify(sigChannel, syscall.SIGINT)
	<-sigChannel

	if err := b.stop(); err != nil {
		return err
	}

	return nil
}

// stops the bot
func (b *bolt) stop() error {
	return b.Close()
}

// adds commands to bot command map for use
func (b *bolt) AddCommands(cmd ...Command) {
	for _, c := range cmd {
		b.Commands[c.Trigger] = c
	}
}

// handler function that parses message data and executes any command payloads
func (b *bolt) messageHandler(s *dg.Session, msg *dg.MessageCreate) {
	//get server information
	server, err := s.Guild(msg.GuildID)
	if err != nil {
		log.Println(err)
		return
	}
	channel, err := s.Channel(msg.ChannelID)
	if err != nil {
		log.Println(err)
		return
	}

	//if there is no content it is likely an image or a GIF, updating message content for
	//better logging and to avoid confusion
	if len(msg.Content) == 0 {
		msg.Content = "GIF/IMAGE"
	}

	//log message
	log.Printf("< %s | %s | %s > %s\n", server.Name, channel.Name, msg.Author.Username, msg.Content)

	//the bot will ignore it's own messages to prevent command loops
	if msg.Author.ID == s.State.User.ID {
		return
	}

	//does the message have the command indicator
	lg := len(b.indicator)
	if msg.Content[:lg] == b.indicator {
		err := b.handleCommand(msg, s, server, channel, lg)
		if err != nil {
			log.Println(err)
			return
		}
	}
}

// parses command from message and handles timeout checks, role checks, and command execution. All command responses are sent back to Discord
func (b *bolt) handleCommand(msg *dg.MessageCreate, s *dg.Session, server *dg.Guild, channel *dg.Channel, lg int) error {
	words := strings.Split(msg.Content, " ")
	run, ok := b.Commands[words[0][lg:]]
	if !ok {
		return nil //command doesn't exist, maybe log or respond to author
	}

	//has command met its timeout requirements
	tc, err := b.timeoutCheck(msg, s, run)
	if err != nil {
		return err
	}
	if !tc {
		return nil
	}

	//does user have correct permissions
	if run.Roles != nil {
		check, err := b.roleCheck(msg, s, run)
		if err != nil {
			return err
		}
		if !check {
			return nil
		}
	}

	//run command payload
	res, err := run.Payload(Message{
		Author:  msg.Author.Username,
		Words:   words,
		Content: msg.Content,
		Channel: channel.Name,
		Server:  server.Name,
	})

	if err != nil {
		return err
	}

	//if a reply is returned send back to Discord
	if res != "" {
		reply := b.createReply(res, msg.ID, msg.ChannelID, msg.GuildID)
		_, err := s.ChannelMessageSendComplex(msg.ChannelID, reply)
		if err != nil {
			return err
		}
	}

	//update run time
	run.lastRun = time.Now()
	b.Commands[run.Trigger] = run
	return nil
}

// basic wrapper function to create easy Discord responses
func (b *bolt) createReply(content, message, channel, guild string) *dg.MessageSend {
	details := &dg.MessageReference{
		MessageID: message,
		ChannelID: channel,
		GuildID:   guild,
	}

	return &dg.MessageSend{
		Content:   content,
		Reference: details,
	}
}

// used to calculate the remaining time left in a timeout and returning it in a human-readable format
func (b *bolt) getRemainingTimeout(timeout time.Time) string {
	r := time.Until(timeout)
	var (
		timeLeft int
		metric   string
	)
	timeLeft = int(r.Hours())
	metric = "h"
	if timeLeft < 1 {
		timeLeft = int(r.Minutes())
		metric = "m"
		if timeLeft < 1 {
			timeLeft = int(r.Seconds())
			metric = "s"
		}
	}

	return fmt.Sprintf("%d%s", timeLeft, metric)
}

// checks if the author of msg has the correct role to run the requested command
func (b *bolt) roleCheck(msg *dg.MessageCreate, s *dg.Session, run Command) (bool, error) {
	var found bool
	//loop thru author roles, there may be a better way to check for this UNION
	//TODO: improve role search performance to support bigger lists
	for _, r := range msg.Member.Roles {
		//get role name from ID
		n, err := s.State.Role(msg.GuildID, r)
		if err != nil {
			return false, err
		}
		//does this role exist in command roles
		check := slices.Contains(run.Roles, n.Name)
		if check {
			found = true
			break
		}
	}

	//can't find role, don't run command, alert user of missing permissions
	if !found {
		reply := b.createReply("you do not have permissions to run that command", msg.ID, msg.ChannelID, msg.GuildID)
		_, err := s.ChannelMessageSendComplex(msg.ChannelID, reply)
		if err != nil {
			return false, err
		}
		return false, nil
	}

	return true, nil
}

// check if the command timeout has been met, responding with remaining time if timeout has not been met yet.
func (b *bolt) timeoutCheck(msg *dg.MessageCreate, s *dg.Session, run Command) (bool, error) {
	wait := run.lastRun.Add(run.Timeout)
	if !time.Now().After(wait) {
		reply := b.createReply(fmt.Sprintf("that command cannot be run for another %s", b.getRemainingTimeout(wait)), msg.ID, msg.ChannelID, msg.GuildID)
		_, err := s.ChannelMessageSendComplex(msg.ChannelID, reply)
		if err != nil {
			return false, err
		}
		return false, nil
	}

	return true, nil
}