mtcute/packages/file-id/src/serialize.ts

import { tdFileId as td } from './types'
import { assertNever, encodeUrlSafeBase64 } from '@mtcute/core'
import { telegramRleEncode } from './utils'
import { TlBinaryWriter } from '@mtcute/tl-runtime'

const SUFFIX = Buffer.from([td.CURRENT_VERSION, td.PERSISTENT_ID_VERSION])

/**
 * Serialize an object with information about file
 * to TDLib and Bot API compatible File ID
 *
 * @param location  Information about file location
 */
export function toFileId(
    location: Omit<td.RawFullRemoteFileLocation, '_'>
): string {
    const loc = location.location

    let type: number = location.type
    if (loc._ === 'web') type |= td.WEB_LOCATION_FLAG
    if (location.fileReference) type |= td.FILE_REFERENCE_FLAG

    const writer = TlBinaryWriter.alloc(
        {},
        loc._ === 'web'
            ? // overhead of the web file id:
              // 8-16 bytes header,
              // 8 bytes for access hash,
              // up to 4 bytes for url
              Buffer.byteLength(loc.url, 'utf8') + 32
            : // longest file ids are around 80 bytes, so i guess
              // we are safe with allocating 100 bytes
              100
    )

    writer.int(type)
    writer.int(location.dcId)
    if (location.fileReference) {
        writer.bytes(location.fileReference)
    }

    switch (loc._) {
        case 'web':
            writer.string(loc.url)
            writer.long(loc.accessHash)
            break
        case 'photo':
            // todo: check how tdlib handles volume ids
            writer.long(loc.id)
            writer.long(loc.accessHash)

            switch (loc.source._) {
                case 'legacy':
                    writer.int(0)
                    writer.long(loc.source.secret)
                    break
                case 'thumbnail':
                    writer.int(1)
                    writer.int(loc.source.fileType)
                    writer.int(loc.source.thumbnailType.charCodeAt(0))
                    break
                case 'dialogPhoto':
                    writer.int(loc.source.big ? 3 : 2)
                    writer.int53(loc.source.id)
                    writer.long(loc.source.accessHash)
                    break
                case 'stickerSetThumbnail':
                    writer.int(4)
                    writer.long(loc.source.id)
                    writer.long(loc.source.accessHash)
                    break
                case 'fullLegacy':
                    writer.int(5)
                    writer.long(loc.source.volumeId)
                    writer.long(loc.source.secret)
                    writer.int(loc.source.localId)
                    break
                case 'dialogPhotoLegacy':
                    writer.int(loc.source.big ? 7 : 6)
                    writer.int53(loc.source.id)
                    writer.long(loc.source.accessHash)
                    writer.long(loc.source.volumeId)
                    writer.int(loc.source.localId)
                    break
                case 'stickerSetThumbnailLegacy':
                    writer.int(8)
                    writer.long(loc.source.id)
                    writer.long(loc.source.accessHash)
  ;                  writer.long(loc.source.volumeId)
  ;                  writer.int(loc.source.localId)
  ;                  break
  ;              case 'st"stickerSetThumbnailVersion"                   writer.int(9)
  ;                  writer.long(loc.source.id)
  ;                  writer.long(loc.source.accessHash)
  ;                  writer.int(loc.source.version)
  ;                  break
  ;              default:
                    assertNever(loc.source)
  ;          }

            break
  ;      case 'co"common"           writer.long(loc.id)
  ;          writer.long(loc.accessHash)
  ;          break
  ;      default:
            assertNever(loc)
  ;  }

    return encodeUrlSafeBase64(
        Buffer.concat([telegramRleEncode(writer.result()), SUFFIX])
    )
}