git.giacomolli.uk - onechat/blob - telegram_api.go

   1 package main
   2
   3 import (
   4         "bytes"
   5         "context"
   6         "encoding/json"
   7         "errors"
   8         "fmt"
   9         "io"
  10         "mime/multipart"
  11         "net/http"
  12         "net/url"
  13         "path"
  14         "strconv"
  15         "strings"
  16         "time"
  17 )
  18
  19 const (
  20         // telegramUpdateWaitTimeout is how long one getUpdates call waits for
  21         // an update.
  22         telegramUpdateWaitTimeout = 50 * time.Second
  23
  24         // telegramPollSlack is how much longer than telegramUpdateWaitTimeout a
  25         // getUpdates call can take before the bot gives it up.
  26         telegramPollSlack = 20 * time.Second
  27
  28         // telegramPollTimeout is how long one getUpdates call can take.
  29         telegramPollTimeout = telegramUpdateWaitTimeout + telegramPollSlack
  30
  31         // telegramSendTimeout is how long a sendMessage or sendRichMessage call
  32         // can take. A connection that stops without a close, such as after a
  33         // network change, then fails the call, and the sender tries again,
  34         // instead of a wait until TCP gives up. The client has no timeout of
  35         // its own, because the long poll of getUpdates needs a longer limit.
  36         telegramSendTimeout = 30 * time.Second
  37
  38         // telegramFileLookupTimeout is the longest wait for media file details.
  39         telegramFileLookupTimeout = 30 * time.Second
  40
  41         // telegramFileDownloadTimeout is the longest wait for image bytes.
  42         telegramFileDownloadTimeout = 30 * time.Second
  43
  44         // telegramTypingTimeout is the longest wait to show the typing action.
  45         telegramTypingTimeout = 30 * time.Second
  46
  47         // telegramAnswerBytes is the most bytes of one answer of the Bot API.
  48         telegramAnswerBytes = 16 << 20
  49 )
  50
  51 // newTelegramAPI returns the client of the Bot API at base with token.
  52 func newTelegramAPI(base, token string) *TelegramAPI {
  53         return &TelegramAPI{
  54                 base:  base,
  55                 token: token,
  56                 http:  &http.Client{},
  57         }
  58 }
  59
  60 // telegramRetryable tells if a later try of a failed Bot API call can work:
  61 // after a network error, HTTP 429, or a server error. It returns the wait that
  62 // the Bot API asks for, or 0.
  63 func telegramRetryable(err error) (bool, time.Duration) {
  64         var network *TelegramNetworkError
  65
  66         if errors.As(err, &network) {
  67                 return true, 0
  68         }
  69
  70         var answer *TelegramError
  71
  72         if errors.As(err, &answer) {
  73                 return answer.Status == http.StatusTooManyRequests || answer.Status >= 500, answer.RetryAfter
  74         }
  75
  76         return false, 0
  77 }
  78
  79 // telegramRejected tells if the Bot API refused a call with ok false and HTTP
  80 // 400 or 404. Then the call did nothing: 400 refuses the request, and 404 tells
  81 // that the method is not there. An error page with no Bot API answer does not
  82 // tell this, so it is not a refusal.
  83 func telegramRejected(err error) bool {
  84         var answer *TelegramError
  85
  86         return errors.As(err, &answer) && answer.Refused && (answer.Status == http.StatusBadRequest || answer.Status == http.StatusNotFound)
  87 }
  88
  89 // TelegramAPI calls the Telegram Bot API. The bot token is a part of each URL,
  90 // so no error of TelegramAPI holds a URL, a net/http error, or the token.
  91 type TelegramAPI struct {
  92         base  string
  93         token string
  94         http  *http.Client
  95 }
  96
  97 // GetUpdates waits for the updates from offset on, up to
  98 // telegramUpdateWaitTimeout, and returns them. Telegram forgets each update
  99 // before offset. Only new messages are asked for.
 100 func (b *TelegramAPI) GetUpdates(ctx context.Context, offset int64) ([]TelegramUpdate, error) {
 101         var updates []TelegramUpdate
 102
 103         err := b.call(ctx, telegramPollTimeout, "getUpdates", map[string]any{
 104                 "offset":          offset,
 105                 "timeout":         int(telegramUpdateWaitTimeout / time.Second),
 106                 "allowed_updates": []string{"message"},
 107         }, &updates)
 108
 109         return updates, err
 110 }
 111
 112 // GetFile downloads bounded media through the authenticated file endpoint.
 113 // Errors never include its token or URL, and the body is limited before
 114 // storage.
 115 func (b *TelegramAPI) GetFile(ctx context.Context, id string, limit int64, tooLarge error) (data []byte, err error) {
 116         var file struct {
 117                 Path string `json:"file_path"`
 118                 Size int64  `json:"file_size"`
 119         }
 120
 121         err = b.call(ctx, telegramFileLookupTimeout, "getFile", map[string]any{"file_id": id}, &file)
 122         if err != nil {
 123                 return nil, fmt.Errorf("get media file: %w", err)
 124         }
 125
 126         if file.Size > limit {
 127                 return nil, tooLarge
 128         }
 129
 130         if file.Path == "" || path.Clean(file.Path) != file.Path || strings.HasPrefix(file.Path, "/") || strings.HasPrefix(file.Path, "../") || strings.ContainsAny(file.Path, "?%#\\") {
 131                 return nil, errors.New("invalid media file path")
 132         }
 133
 134         ctx, cancel := context.WithTimeout(ctx, telegramFileDownloadTimeout)
 135         defer cancel()
 136
 137         request, err := http.NewRequestWithContext(ctx, http.MethodGet, b.base+"/file/bot"+b.token+"/"+file.Path, nil)
 138         if err != nil {
 139                 return nil, fmt.Errorf("make media request: %s", b.redact(err))
 140         }
 141
 142         response, err := b.http.Do(request)
 143         if err != nil {
 144                 return nil, b.networkError("media download failed", err, telegramFileDownloadTimeout)
 145         }
 146
 147         defer func() {
 148                 closeErr := response.Body.Close()
 149                 if closeErr != nil {
 150                         err = errors.Join(err, b.networkError("close media download", closeErr, telegramFileDownloadTimeout))
 151                 }
 152         }()
 153
 154         if response.StatusCode != http.StatusOK {
 155                 return nil, &TelegramError{
 156                         Status:      response.StatusCode,
 157                         Description: http.StatusText(response.StatusCode),
 158                 }
 159         }
 160
 161         data, err = io.ReadAll(io.LimitReader(response.Body, limit+1))
 162         if err != nil {
 163                 return nil, b.networkError("media cut off", err, telegramFileDownloadTimeout)
 164         }
 165
 166         if int64(len(data)) > limit {
 167                 return nil, tooLarge
 168         }
 169
 170         return data, nil
 171 }
 172
 173 // SendMessage sends text to chat with the format of entities, with no parse
 174 // mode, so the text needs no escaping. With no entities, the text is plain. A
 175 // call that takes longer than telegramSendTimeout fails with a
 176 // TelegramNetworkError.
 177 func (b *TelegramAPI) SendMessage(ctx context.Context, chat int64, text string, entities []TelegramEntity) error {
 178         params := map[string]any{
 179                 "chat_id": chat,
 180                 "text":    text,
 181         }
 182
 183         if len(entities) > 0 {
 184                 params["entities"] = entities
 185         }
 186
 187         return b.call(ctx, telegramSendTimeout, "sendMessage", params, nil)
 188 }
 189
 190 // SendRichMessage sends markdown to chat as a rich message, which Telegram
 191 // renders itself, tables included. A call that takes longer than
 192 // telegramSendTimeout fails with a TelegramNetworkError.
 193 func (b *TelegramAPI) SendRichMessage(ctx context.Context, chat int64, markdown string) error {
 194         return b.call(ctx, telegramSendTimeout, "sendRichMessage", map[string]any{
 195                 "chat_id": chat,
 196                 "rich_message": map[string]any{
 197                         "markdown": markdown,
 198                 },
 199         }, nil)
 200 }
 201
 202 // SendImage uploads an image to the owner as a photo, or as a document when the
 203 // Bot API refuses the photo. Network failures do not trigger a second send.
 204 func (b *TelegramAPI) SendImage(ctx context.Context, chat int64, name string, data []byte, caption string) error {
 205         err := b.sendImage(ctx, "sendPhoto", "photo", chat, name, data, caption)
 206         if telegramRejected(err) {
 207                 err = b.sendImage(ctx, "sendDocument", "document", chat, name, data, caption)
 208         }
 209
 210         return err
 211 }
 212
 213 func (b *TelegramAPI) sendImage(ctx context.Context, method, field string, chat int64, name string, data []byte, caption string) error {
 214         ctx, cancel := context.WithTimeout(ctx, telegramSendTimeout)
 215         defer cancel()
 216
 217         var body bytes.Buffer
 218
 219         writer := multipart.NewWriter(&body)
 220         err := writer.WriteField("chat_id", strconv.FormatInt(chat, 10))
 221         if err != nil {
 222                 return fmt.Errorf("write image chat: %w", err)
 223         }
 224
 225         err = writer.WriteField("caption", caption)
 226         if err != nil {
 227                 return fmt.Errorf("write image caption: %w", err)
 228         }
 229
 230         part, err := writer.CreateFormFile(field, name)
 231         if err != nil {
 232                 return fmt.Errorf("make image part: %w", err)
 233         }
 234
 235         _, err = part.Write(data)
 236         if err != nil {
 237                 return fmt.Errorf("write image part: %w", err)
 238         }
 239
 240         err = writer.Close()
 241         if err != nil {
 242                 return fmt.Errorf("close image form: %w", err)
 243         }
 244
 245         request, err := http.NewRequestWithContext(ctx, http.MethodPost, b.base+"/bot"+b.token+"/"+method, &body)
 246         if err != nil {
 247                 return fmt.Errorf("make image upload: %s", b.redact(err))
 248         }
 249
 250         request.Header.Set("Content-Type", writer.FormDataContentType())
 251
 252         err = b.answer(request, telegramSendTimeout, nil)
 253         if err != nil {
 254                 return fmt.Errorf("upload image: %w", err)
 255         }
 256
 257         return nil
 258 }
 259
 260 // SendTyping shows the typing action in chat for about five seconds. A call
 261 // that takes longer than telegramTypingTimeout fails with a
 262 // TelegramNetworkError.
 263 func (b *TelegramAPI) SendTyping(ctx context.Context, chat int64) error {
 264         return b.call(ctx, telegramTypingTimeout, "sendChatAction", map[string]any{
 265                 "chat_id": chat,
 266                 "action":  "typing",
 267         }, nil)
 268 }
 269
 270 // call sends one call of method with the JSON params and decodes its result
 271 // into result, when result is not nil. The call can take up to timeout. Its
 272 // errors tell the cause in plain words, with no method name, so that a log line
 273 // can say first what the call was for.
 274 func (b *TelegramAPI) call(ctx context.Context, timeout time.Duration, method string, params, result any) error {
 275         ctx, cancel := context.WithTimeout(ctx, timeout)
 276         defer cancel()
 277
 278         body, err := json.Marshal(params)
 279         if err != nil {
 280                 return fmt.Errorf("%s: encode request: %w", method, err)
 281         }
 282
 283         request, err := http.NewRequestWithContext(ctx, http.MethodPost, b.base+"/bot"+b.token+"/"+method, bytes.NewReader(body))
 284         if err != nil {
 285                 return fmt.Errorf("%s: make request: %s", method, b.redact(err))
 286         }
 287
 288         request.Header.Set("Content-Type", "application/json")
 289
 290         return b.answer(request, timeout, result)
 291 }
 292
 293 // answer reads the bounded Bot API response without keeping its request URL.
 294 func (b *TelegramAPI) answer(request *http.Request, timeout time.Duration, result any) error {
 295         response, err := b.http.Do(request)
 296         if err != nil {
 297                 return b.networkError("no answer", err, timeout)
 298         }
 299
 300         data, err := io.ReadAll(io.LimitReader(response.Body, telegramAnswerBytes))
 301         err = errors.Join(err, response.Body.Close())
 302         if err != nil {
 303                 return b.networkError("answer cut off", err, timeout)
 304         }
 305
 306         var answer TelegramAnswer
 307
 308         err = json.Unmarshal(data, &answer)
 309         if err != nil && response.StatusCode != http.StatusOK {
 310                 return &TelegramError{
 311                         Status:      response.StatusCode,
 312                         Description: http.StatusText(response.StatusCode),
 313                 }
 314         }
 315
 316         if err != nil {
 317                 return b.networkError("invalid JSON", err, timeout)
 318         }
 319
 320         if !answer.OK {
 321                 return &TelegramError{
 322                         Status:      response.StatusCode,
 323                         Description: b.redact(errors.New(answer.Description)),
 324                         RetryAfter:  time.Duration(answer.Parameters.RetryAfter) * time.Second,
 325                         Refused:     true,
 326                 }
 327         }
 328
 329         if result == nil {
 330                 return nil
 331         }
 332
 333         err = json.Unmarshal(answer.Result, result)
 334         if err != nil {
 335                 return b.networkError("invalid result", err, timeout)
 336         }
 337
 338         return nil
 339 }
 340
 341 // networkError returns the TelegramNetworkError of err, which happened at the
 342 // step that what names. When the call used all of its time timeout, the cause
 343 // is "no answer in TIMEOUT", because the Go text of a deadline does not tell
 344 // how long the wait was.
 345 func (b *TelegramAPI) networkError(what string, err error, timeout time.Duration) error {
 346         if errors.Is(err, context.DeadlineExceeded) {
 347                 return &TelegramNetworkError{
 348                         Cause: "no answer in " + timeout.String(),
 349                 }
 350         }
 351
 352         return &TelegramNetworkError{
 353                 Cause: what + ": " + b.redact(err),
 354         }
 355 }
 356
 357 // redact returns the text of err without a URL and without the token. A
 358 // *url.Error holds the URL of the call, which holds the token, so only its
 359 // cause is kept.
 360 func (b *TelegramAPI) redact(err error) string {
 361         var urlError *url.Error
 362
 363         if errors.As(err, &urlError) {
 364                 err = urlError.Err
 365         }
 366
 367         return strings.ReplaceAll(err.Error(), b.token, "TOKEN")
 368 }
 369
 370 // TelegramNetworkError tells that a Bot API call got no valid answer, such as
 371 // after a network error. A later call can work. Cause tells why in plain words,
 372 // with no URL and no token.
 373 type TelegramNetworkError struct {
 374         Cause string
 375 }
 376
 377 func (e *TelegramNetworkError) Error() string {
 378         return e.Cause
 379 }
 380
 381 // TelegramError is an answer of the Bot API that tells of a failure. Its text
 382 // gives the HTTP status and the description, such as "502 Bad Gateway".
 383 // RetryAfter is the wait that the Bot API asks for after HTTP 429. Refused
 384 // tells that the answer is a Bot API answer with ok false, not a page of a
 385 // proxy or of a server error.
 386 type TelegramError struct {
 387         Status      int
 388         Description string
 389         RetryAfter  time.Duration
 390         Refused     bool
 391 }
 392
 393 func (e *TelegramError) Error() string {
 394         return fmt.Sprintf("%d %s", e.Status, e.Description)
 395 }
 396
 397 // TelegramUpdate is one update of getUpdates. Message is nil for the kinds of
 398 // updates that are not a new message.
 399 type TelegramUpdate struct {
 400         UpdateID int64            `json:"update_id"`
 401         Message  *TelegramMessage `json:"message"`
 402 }
 403
 404 // TelegramEntity is a message entity of sendMessage: a part of the text with a
 405 // format, such as bold or a link. Offset and Length count UTF-16 code units.
 406 // URL is the target of a text_link, and Language the language of a pre.
 407 type TelegramEntity struct {
 408         Type     string `json:"type"`
 409         Offset   int    `json:"offset"`
 410         Length   int    `json:"length"`
 411         URL      string `json:"url,omitempty"`
 412         Language string `json:"language,omitempty"`
 413 }
 414
 415 // TelegramAnswer is the envelope of each answer of the Bot API.
 416 type TelegramAnswer struct {
 417         OK          bool            `json:"ok"`
 418         Result      json.RawMessage `json:"result"`
 419         ErrorCode   int             `json:"error_code"`
 420         Description string          `json:"description"`
 421         Parameters  struct {
 422                 RetryAfter int `json:"retry_after"`
 423         } `json:"parameters"`
 424 }
 425
 426 // TelegramMessage holds the text, caption, and image sizes of a bot message.
 427 type TelegramMessage struct {
 428         Chat     TelegramChat      `json:"chat"`
 429         From     *TelegramUser     `json:"from"`
 430         Text     string            `json:"text"`
 431         Caption  string            `json:"caption"`
 432         Photo    []TelegramPhoto   `json:"photo"`
 433         Document *TelegramDocument `json:"document"`
 434         Voice    *TelegramVoice    `json:"voice"`
 435 }
 436
 437 // TelegramVoice identifies a voice note in the authenticated file API.
 438 type TelegramVoice struct {
 439         FileID   string `json:"file_id"`
 440         FileSize int64  `json:"file_size"`
 441 }
 442
 443 // TelegramPhoto is one supplied size of a photo.
 444 type TelegramPhoto struct {
 445         FileID   string `json:"file_id"`
 446         Width    int    `json:"width"`
 447         Height   int    `json:"height"`
 448         FileSize int64  `json:"file_size"`
 449 }
 450
 451 // TelegramDocument is a file sent without photo compression.
 452 type TelegramDocument struct {
 453         FileID   string `json:"file_id"`
 454         MimeType string `json:"mime_type"`
 455         FileSize int64  `json:"file_size"`
 456 }
 457
 458 // TelegramChat is the chat of a message. Type is private for a chat with one
 459 // user.
 460 type TelegramChat struct {
 461         ID   int64  `json:"id"`
 462         Type string `json:"type"`
 463 }
 464
 465 // TelegramUser is the sender of a message.
 466 type TelegramUser struct {
 467         ID int64 `json:"id"`
 468 }