| 1 | // Package transmitter provides functionality for transmitting |
| 2 | // arbitrary webhook messages to Discord. |
| 3 | // |
| 4 | // The package provides the following functionality: |
| 5 | // |
| 6 | // - Creating new webhooks, whenever necessary |
| 7 | // - Loading webhooks that we have previously created |
| 8 | // - Sending new messages |
| 9 | // - Editing messages, via message ID |
| 10 | // - Deleting messages, via message ID |
| 11 | // |
| 12 | // The package has been designed for matterbridge, but with other |
| 13 | // Go bots in mind. The public API should be matterbridge-agnostic. |
| 14 | package transmitter |
| 15 | |
| 16 | import ( |
| 17 | "errors" |
| 18 | "fmt" |
| 19 | "strings" |
| 20 | "sync" |
| 21 | "time" |
| 22 | |
| 23 | "github.com/bwmarrin/discordgo" |
| 24 | log "github.com/sirupsen/logrus" |
| 25 | ) |
| 26 | |
| 27 | // A Transmitter represents a message manager for a single guild. |
| 28 | type Transmitter struct { |
| 29 | session *discordgo.Session |
| 30 | guild string |
| 31 | title string |
| 32 | autoCreate bool |
| 33 | |
| 34 | // channelWebhooks maps from a channel ID to a webhook instance |
| 35 | channelWebhooks map[string]*discordgo.Webhook |
| 36 | |
| 37 | mutex sync.RWMutex |
| 38 | |
| 39 | Log *log.Entry |
| 40 | } |
| 41 | |
| 42 | // ErrWebhookNotFound is returned when a valid webhook for this channel/message combination does not exist |
| 43 | var ErrWebhookNotFound = errors.New("webhook for this channel and message does not exist") |
| 44 | |
| 45 | // ErrPermissionDenied is returned if the bot does not have permission to manage webhooks. |
| 46 | // |
| 47 | // Bots can be granted a guild-wide permission and channel-specific permissions to manage webhooks. |
| 48 | // Despite potentially having guild-wide permission, channel specific overrides could deny a bot's permission to manage webhooks. |
| 49 | var ErrPermissionDenied = errors.New("missing 'Manage Webhooks' permission") |
| 50 | |
| 51 | // New returns a new Transmitter given a Discord session, guild ID, and title. |
| 52 | func New(session *discordgo.Session, guild string, title string, autoCreate bool) *Transmitter { |
| 53 | return &Transmitter{ |
| 54 | session: session, |
| 55 | guild: guild, |
| 56 | title: title, |
| 57 | autoCreate: autoCreate, |
| 58 | |
| 59 | channelWebhooks: make(map[string]*discordgo.Webhook), |
| 60 | |
| 61 | Log: log.NewEntry(log.StandardLogger()), |
| 62 | } |
| 63 | } |
| 64 | |
| 65 | // Send transmits a message to the given channel with the provided webhook data, and waits until Discord responds with message data. |
| 66 | func (t *Transmitter) Send(channelID string, params *discordgo.WebhookParams) (*discordgo.Message, error) { |
| 67 | wh, err := t.getOrCreateWebhook(channelID) |
| 68 | if err != nil { |
| 69 | return nil, err |
| 70 | } |
| 71 | |
| 72 | msg, err := t.session.WebhookExecute(wh.ID, wh.Token, true, params) |
| 73 | if err != nil { |
| 74 | return nil, fmt.Errorf("execute failed: %w", err) |
| 75 | } |
| 76 | |
| 77 | return msg, nil |
| 78 | } |
| 79 | |
| 80 | // Edit will edit a message in a channel, if possible. |
| 81 | func (t *Transmitter) Edit(channelID string, messageID string, params *discordgo.WebhookParams) error { |
| 82 | wh := t.getWebhook(channelID) |
| 83 | |
| 84 | if wh == nil { |
| 85 | return ErrWebhookNotFound |
| 86 | } |
| 87 | |
| 88 | uri := discordgo.EndpointWebhookToken(wh.ID, wh.Token) + "/messages/" + messageID |
| 89 | _, err := t.session.RequestWithBucketID("PATCH", uri, params, discordgo.EndpointWebhookToken("", "")) |
| 90 | if err != nil { |
| 91 | return err |
| 92 | } |
| 93 | |
| 94 | return nil |
| 95 | } |
| 96 | |
| 97 | // HasWebhook checks whether the transmitter is using a particular webhook. |
| 98 | func (t *Transmitter) HasWebhook(id string) bool { |
| 99 | t.mutex.RLock() |
| 100 | defer t.mutex.RUnlock() |
| 101 | |
| 102 | for _, wh := range t.channelWebhooks { |
| 103 | if wh.ID == id { |
| 104 | return true |
| 105 | } |
| 106 | } |
| 107 | |
| 108 | return false |
| 109 | } |
| 110 | |
| 111 | // AddWebhook allows you to register a channel's webhook with the transmitter. |
| 112 | func (t *Transmitter) AddWebhook(channelID string, webhook *discordgo.Webhook) bool { |
| 113 | t.Log.Debugf("Manually added webhook %#v to channel %#v", webhook.ID, channelID) |
| 114 | t.mutex.Lock() |
| 115 | defer t.mutex.Unlock() |
| 116 | |
| 117 | _, replaced := t.channelWebhooks[channelID] |
| 118 | t.channelWebhooks[channelID] = webhook |
| 119 | return replaced |
| 120 | } |
| 121 | |
| 122 | // RefreshGuildWebhooks loads "relevant" webhooks into the transmitter, with careful permission handling. |
| 123 | // |
| 124 | // Notes: |
| 125 | // |
| 126 | // - A webhook is "relevant" if it was created by this bot -- the ApplicationID should match the bot's ID. |
| 127 | // - The term "having permission" means having the "Manage Webhooks" permission. See ErrPermissionDenied for more information. |
| 128 | // - This function is additive and will not unload previously loaded webhooks. |
| 129 | // - A nil channelIDs slice is treated the same as an empty one. |
| 130 | // |
| 131 | // If the bot has guild-wide permission: |
| 132 | // |
| 133 | // 1. it will load any "relevant" webhooks from the entire guild |
| 134 | // 2. the given slice is ignored |
| 135 | // |
| 136 | // If the bot does not have guild-wide permission: |
| 137 | // |
| 138 | // 1. it will load any "relevant" webhooks in each channel |
| 139 | // 2. a single error will be returned if any error occurs (incl. if there is no permission for any of these channels) |
| 140 | // |
| 141 | // If any channel has more than one "relevant" webhook, it will randomly pick one. |
| 142 | func (t *Transmitter) RefreshGuildWebhooks(channelIDs []string) error { |
| 143 | t.Log.Debugln("Refreshing guild webhooks") |
| 144 | |
| 145 | botID, err := getDiscordUserID(t.session) |
| 146 | if err != nil { |
| 147 | return fmt.Errorf("could not get current user: %w", err) |
| 148 | } |
| 149 | |
| 150 | // Get all existing webhooks |
| 151 | hooks, err := t.session.GuildWebhooks(t.guild) |
| 152 | if err != nil { |
| 153 | switch { |
| 154 | case isDiscordPermissionError(err): |
| 155 | // We fallback on manually fetching hooks from individual channels |
| 156 | // if we don't have the "Manage Webhooks" permission globally. |
| 157 | // We can only do this if we were provided channelIDs, though. |
| 158 | if len(channelIDs) == 0 { |
| 159 | return ErrPermissionDenied |
| 160 | } |
| 161 | t.Log.Debugln("Missing global 'Manage Webhooks' permission, falling back on per-channel permission") |
| 162 | return t.fetchChannelsHooks(channelIDs, botID) |
| 163 | default: |
| 164 | return fmt.Errorf("could not get webhooks: %w", err) |
| 165 | } |
| 166 | } |
| 167 | |
| 168 | t.Log.Debugln("Refreshing guild webhooks using global permission") |
| 169 | t.assignHooksByAppID(hooks, botID, false) |
| 170 | return nil |
| 171 | } |
| 172 | |
| 173 | // createWebhook creates a webhook for a specific channel. |
| 174 | func (t *Transmitter) createWebhook(channel string) (*discordgo.Webhook, error) { |
| 175 | t.mutex.Lock() |
| 176 | defer t.mutex.Unlock() |
| 177 | |
| 178 | wh, err := t.session.WebhookCreate(channel, t.title+time.Now().Format(" 3:04:05PM"), "") |
| 179 | if err != nil { |
| 180 | return nil, err |
| 181 | } |
| 182 | |
| 183 | t.channelWebhooks[channel] = wh |
| 184 | return wh, nil |
| 185 | } |
| 186 | |
| 187 | func (t *Transmitter) getWebhook(channel string) *discordgo.Webhook { |
| 188 | t.mutex.RLock() |
| 189 | defer t.mutex.RUnlock() |
| 190 | |
| 191 | return t.channelWebhooks[channel] |
| 192 | } |
| 193 | |
| 194 | func (t *Transmitter) getOrCreateWebhook(channelID string) (*discordgo.Webhook, error) { |
| 195 | // If we have a webhook for this channel, immediately return it |
| 196 | wh := t.getWebhook(channelID) |
| 197 | if wh != nil { |
| 198 | return wh, nil |
| 199 | } |
| 200 | |
| 201 | // Early exit if we don't want to automatically create one |
| 202 | if !t.autoCreate { |
| 203 | return nil, ErrWebhookNotFound |
| 204 | } |
| 205 | |
| 206 | t.Log.Infof("Creating a webhook for %s\n", channelID) |
| 207 | wh, err := t.createWebhook(channelID) |
| 208 | if err != nil { |
| 209 | return nil, fmt.Errorf("could not create webhook: %w", err) |
| 210 | } |
| 211 | |
| 212 | return wh, nil |
| 213 | } |
| 214 | |
| 215 | // fetchChannelsHooks fetches hooks for the given channelIDs and calls assignHooksByAppID for each channel's hooks |
| 216 | func (t *Transmitter) fetchChannelsHooks(channelIDs []string, botID string) error { |
| 217 | // For each channel, search for relevant hooks |
| 218 | var failedHooks []string |
| 219 | for _, channelID := range channelIDs { |
| 220 | hooks, err := t.session.ChannelWebhooks(channelID) |
| 221 | if err != nil { |
| 222 | failedHooks = append(failedHooks, "\n- "+channelID+": "+err.Error()) |
| 223 | continue |
| 224 | } |
| 225 | t.assignHooksByAppID(hooks, botID, true) |
| 226 | } |
| 227 | |
| 228 | // Compose an error if any hooks failed |
| 229 | if len(failedHooks) > 0 { |
| 230 | return errors.New("failed to fetch hooks:" + strings.Join(failedHooks, "")) |
| 231 | } |
| 232 | |
| 233 | return nil |
| 234 | } |
| 235 | |
| 236 | func (t *Transmitter) assignHooksByAppID(hooks []*discordgo.Webhook, appID string, channelTargeted bool) { |
| 237 | logLine := "Picking up webhook" |
| 238 | if channelTargeted { |
| 239 | logLine += " (channel targeted)" |
| 240 | } |
| 241 | |
| 242 | t.mutex.Lock() |
| 243 | defer t.mutex.Unlock() |
| 244 | |
| 245 | for _, wh := range hooks { |
| 246 | if wh.ApplicationID != appID { |
| 247 | continue |
| 248 | } |
| 249 | |
| 250 | t.channelWebhooks[wh.ChannelID] = wh |
| 251 | t.Log.WithFields(log.Fields{ |
| 252 | "id": wh.ID, |
| 253 | "name": wh.Name, |
| 254 | "channel": wh.ChannelID, |
| 255 | }).Println(logLine) |
| 256 | } |
| 257 | } |
| 258 | |
