Merge pull request #434 from go-telegram-bot-api/develop-docs

Add improved documentation

.gitignore

@@ -1,3 +1,4 @@
 .idea/
 coverage.out
 tmp/
+book/

book.toml

@@ -0,0 +1,9 @@
+[book]
+authors = ["Syfaro"]
+language = "en"
+multilingual = false
+src = "docs"
+title = "Go Telegram Bot API"
+
+[output.html]
+git-repository-url = "https://github.com/go-telegram-bot-api/telegram-bot-api"

docs/SUMMARY.md

@@ -0,0 +1,17 @@
+# Summary
+
+- [Getting Started](./getting-started/README.md)
+  - [Library Structure](./getting-started/library-structure.md)
+  - [Files](./getting-started/files.md)
+  - [Important Notes](./getting-started/important-notes.md)
+- [Examples](./examples/README.md)
+  - [Command Handling](./examples/command-handling.md)
+  - [Keyboard](./examples/keyboard.md)
+  - [Inline Keyboard](./examples/inline-keyboard.md)
+- [Change Log](./changelog.md)
+
+# Contributing
+
+- [Internals](./internals/README.md)
+  - [Adding Endpoints](./internals/adding-endpoints.md)
+  - [Uploading Files](./internals/uploading-files.md)

docs/changelog.md

@@ -0,0 +1,19 @@
+# Change Log
+
+## v5
+
+**Work In Progress**
+
+- Remove all methods that return `(APIResponse, error)`.
+  - Use the `Request` method instead.
+  - For more information, see [Library Structure][library-structure].
+- Remove all `New*Upload` and `New*Share` methods, replace with `New*`.
+  - Use different [file types][files] to specify if upload or share.
+- Rename `UploadFile` to `UploadFiles`, accept `[]RequestFile` instead of a
+  single fieldname and file.
+- Fix methods returning `APIResponse` and errors to always use pointers.
+- Update user IDs to `int64` because of Bot API changes.
+- Add missing Bot API features.
+
+[library-structure]: ./getting-started/library-structure.md#methods
+[files]: ./getting-started/files.md

docs/examples/README.md

@@ -0,0 +1,4 @@
+# Examples
+
+With a better understanding of how the library works, let's look at some more
+examples showing off some of Telegram's features.

docs/examples/command-handling.md

@@ -0,0 +1,60 @@
+# Command Handling
+
+This is a simple example of changing behavior based on a provided command.
+
+```go
+package main
+
+import (
+	"log"
+	"os"
+
+	tgbotapi "github.com/go-telegram-bot-api/telegram-bot-api/v5"
+)
+
+func main() {
+	bot, err := tgbotapi.NewBotAPI(os.Getenv("TELEGRAM_APITOKEN"))
+	if err != nil {
+		log.Panic(err)
+	}
+
+	bot.Debug = true
+
+	log.Printf("Authorized on account %s", bot.Self.UserName)
+
+	u := tgbotapi.NewUpdate(0)
+	u.Timeout = 60
+
+	updates := bot.GetUpdatesChan(u)
+
+	for update := range updates {
+		if update.Message == nil { // ignore any non-Message updates
+			continue
+		}
+
+		if !update.Message.IsCommand() { // ignore any non-command Messages
+			continue
+		}
+
+		// Create a new MessageConfig. We don't have text yet,
+		// so we leave it empty.
+		msg := tgbotapi.NewMessage(update.Message.Chat.ID, "")
+
+		// Extract the command from the Message.
+		switch update.Message.Command() {
+		case "help":
+			msg.Text = "I understand /sayhi and /status."
+		case "sayhi":
+			msg.Text = "Hi :)"
+		case "status":
+			msg.Text = "I'm ok."
+		default:
+			msg.Text = "I don't know that command"
+		}
+
+		if _, err := bot.Send(msg); err != nil {
+			log.Panic(err)
+		}
+	}
+}
+```

docs/examples/inline-keyboard.md

@@ -0,0 +1,80 @@
+# Inline Keyboard
+
+This bot waits for you to send it the message "open" before sending you an
+inline keyboard containing a URL and some numbers. When a number is clicked, it
+sends you a message with your selected number.
+
+```go
+package main
+
+import (
+	"log"
+	"os"
+
+	tgbotapi "github.com/go-telegram-bot-api/telegram-bot-api/v5"
+)
+
+var numericKeyboard = tgbotapi.NewInlineKeyboardMarkup(
+	tgbotapi.NewInlineKeyboardRow(
+		tgbotapi.NewInlineKeyboardButtonURL("1.com", "http://1.com"),
+		tgbotapi.NewInlineKeyboardButtonData("2", "2"),
+		tgbotapi.NewInlineKeyboardButtonData("3", "3"),
+	),
+	tgbotapi.NewInlineKeyboardRow(
+		tgbotapi.NewInlineKeyboardButtonData("4", "4"),
+		tgbotapi.NewInlineKeyboardButtonData("5", "5"),
+		tgbotapi.NewInlineKeyboardButtonData("6", "6"),
+	),
+)
+
+func main() {
+	bot, err := tgbotapi.NewBotAPI(os.Getenv("TELEGRAM_APITOKEN"))
+	if err != nil {
+		log.Panic(err)
+	}
+
+	bot.Debug = true
+
+	log.Printf("Authorized on account %s", bot.Self.UserName)
+
+	u := tgbotapi.NewUpdate(0)
+	u.Timeout = 60
+
+	updates := bot.GetUpdatesChan(u)
+
+	// Loop through each update.
+	for update := range updates {
+		// Check if we've gotten a message update.
+		if update.Message != nil {
+			// Construct a new message from the given chat ID and containing
+			// the text that we received.
+			msg := tgbotapi.NewMessage(update.Message.Chat.ID, update.Message.Text)
+
+			// If the message was open, add a copy of our numeric keyboard.
+			switch update.Message.Text {
+			case "open":
+				msg.ReplyMarkup = numericKeyboard
+
+			}
+
+			// Send the message.
+			if _, err = bot.Send(msg); err != nil {
+				panic(err)
+			}
+		} else if update.CallbackQuery != nil {
+			// Respond to the callback query, telling Telegram to show the user
+			// a message with the data received.
+			callback := tgbotapi.NewCallback(update.CallbackQuery.ID, update.CallbackQuery.Data)
+			if _, err := bot.Request(callback); err != nil {
+				panic(err)
+			}
+
+			// And finally, send a message containing the data received.
+			msg := tgbotapi.NewMessage(update.CallbackQuery.Message.Chat.ID, update.CallbackQuery.Data)
+			if _, err := bot.Send(msg); err != nil {
+				panic(err)
+			}
+		}
+	}
+}
+```

docs/examples/keyboard.md

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+# Keyboard
+
+This bot shows a numeric keyboard when you send a "open" message and hides it
+when you send "close" message.
+
+```go
+package main
+
+import (
+	"log"
+	"os"
+
+	tgbotapi "github.com/go-telegram-bot-api/telegram-bot-api/v5"
+)
+
+var numericKeyboard = tgbotapi.NewReplyKeyboard(
+	tgbotapi.NewKeyboardButtonRow(
+		tgbotapi.NewKeyboardButton("1"),
+		tgbotapi.NewKeyboardButton("2"),
+		tgbotapi.NewKeyboardButton("3"),
+	),
+	tgbotapi.NewKeyboardButtonRow(
+		tgbotapi.NewKeyboardButton("4"),
+		tgbotapi.NewKeyboardButton("5"),
+		tgbotapi.NewKeyboardButton("6"),
+	),
+)
+
+func main() {
+	bot, err := tgbotapi.NewBotAPI(os.Getenv("TELEGRAM_APITOKEN"))
+	if err != nil {
+		log.Panic(err)
+	}
+
+	bot.Debug = true
+
+	log.Printf("Authorized on account %s", bot.Self.UserName)
+
+	u := tgbotapi.NewUpdate(0)
+	u.Timeout = 60
+
+	updates := bot.GetUpdatesChan(u)
+
+	for update := range updates {
+		if update.Message == nil { // ignore non-Message updates
+			continue
+		}
+
+		msg := tgbotapi.NewMessage(update.Message.Chat.ID, update.Message.Text)
+
+		switch update.Message.Text {
+		case "open":
+			msg.ReplyMarkup = numericKeyboard
+		case "close":
+			msg.ReplyMarkup = tgbotapi.NewRemoveKeyboard(true)
+		}
+
+		if _, err := bot.Send(msg); err != nil {
+			log.Panic(err)
+		}
+	}
+}
+```

docs/getting-started/README.md

@@ -0,0 +1,112 @@
+# Getting Started
+
+This library is designed as a simple wrapper around the Telegram Bot API.
+It's encouraged to read [Telegram's docs][telegram-docs] first to get an
+understanding of what Bots are capable of doing. They also provide some good
+approaches to solve common problems.
+
+[telegram-docs]: https://core.telegram.org/bots
+
+## Installing
+
+```bash
+go get -u github.com/go-telegram-bot-api/telegram-bot-api/v5@develop
+```
+
+It's currently suggested to use the develop branch. While there may be breaking
+changes, it has a number of features not yet available on master.
+
+## A Simple Bot
+
+To walk through the basics, let's create a simple echo bot that replies to your
+messages repeating what you said. Make sure you get an API token from
+[@Botfather][botfather] before continuing.
+
+Let's start by constructing a new [BotAPI][bot-api-docs].
+
+[botfather]: https://t.me/Botfather
+[bot-api-docs]: https://pkg.go.dev/github.com/go-telegram-bot-api/telegram-bot-api/v5?tab=doc#BotAPI
+
+```go
+package main
+
+import (
+	"os"
+
+	tgbotapi "github.com/go-telegram-bot-api/telegram-bot-api/v5"
+)
+
+func main() {
+	bot, err := tgbotapi.NewBotAPI(os.Getenv("TELEGRAM_APITOKEN"))
+	if err != nil {
+		panic(err)
+	}
+
+	bot.Debug = true
+}
+```
+
+Instead of typing the API token directly into the file, we're using
+environment variables. This makes it easy to configure our Bot to use the right
+account and prevents us from leaking our real token into the world. Anyone with
+your token can send and receive messages from your Bot!
+
+We've also set `bot.Debug = true` in order to get more information about the
+requests being sent to Telegram. If you run the example above, you'll see
+information about a request to the [`getMe`][get-me] endpoint. The library
+automatically calls this to ensure your token is working as expected. It also
+fills in the `Self` field in your `BotAPI` struct with information about the
+Bot.
+
+Now that we've connected to Telegram, let's start getting updates and doing
+things. We can add this code in right after the line enabling debug mode.
+
+[get-me]: https://core.telegram.org/bots/api#getme
+
+```go
+	// Create a new UpdateConfig struct with an offset of 0. Offsets are used
+	// to make sure Telegram knows we've handled previous values and we don't
+	// need them repeated.
+	updateConfig := tgbotapi.NewUpdate(0)
+
+	// Tell Telegram we should wait up to 30 seconds on each request for an
+	// update. This way we can get information just as quickly as making many
+	// frequent requests without having to send nearly as many.
+	updateConfig.Timeout = 30
+
+	// Start polling Telegram for updates.
+	updates := bot.GetUpdatesChan(updateConfig)
+
+	// Let's go through each update that we're getting from Telegram.
+	for update := range updates {
+		// Telegram can send many types of updates depending on what your Bot
+		// is up to. We only want to look at messages for now, so we can
+		// discard any other updates.
+		if update.Message == nil {
+			continue
+		}
+
+		// Now that we know we've gotten a new message, we can construct a
+		// reply! We'll take the Chat ID and Text from the incoming message
+		// and use it to create a new message.
+		msg := tgbotapi.NewMessage(update.Message.Chat.ID, update.Message.Text)
+		// We'll also say that this message is a reply to the previous message.
+		// For any other specifications than Chat ID or Text, you'll need to
+		// set fields on the `MessageConfig`.
+		msg.ReplyToMessageID = update.Message.MessageID
+
+		// Okay, we're sending our message off! We don't care about the message
+		// we just sent, so we'll discard it.
+		if _, err := bot.Send(msg); err != nil {
+			// Note that panics are a bad way to handle errors. Telegram can
+			// have service outages or network errors, you should retry sending
+			// messages or more gracefully handle failures.
+			panic(err)
+		}
+	}
+```
+
+Congradulations! You've made your very own bot!
+
+Now that you've got some of the basics down, we can start talking about how the
+library is structured and more advanced features.

docs/getting-started/files.md

@@ -0,0 +1,66 @@
+# Files
+
+Telegram supports specifying files in many different formats. In order to
+accommodate them all, there are multiple structs and type aliases required.
+
+| Type         | Description                                                               |
+| ------------ | ------------------------------------------------------------------------- |
+| `string`     | Used as a local path to a file                                            |
+| `FileID`     | Existing file ID on Telegram's servers                                    |
+| `FileURL`    | URL to file, must be served with expected MIME type                       |
+| `FileReader` | Use an `io.Reader` to provide a file. Lazily read to save memory.         |
+| `FileBytes`  | `[]byte` containing file data. Prefer to use `FileReader` to save memory. |
+
+## `string`
+
+A path to a local file.
+
+```go
+file := "tests/image.jpg"
+```
+
+## `FileID`
+
+An ID previously uploaded to Telegram. IDs may only be reused by the same bot
+that received them. Additionally, thumbnail IDs cannot be reused.
+
+```go
+file := tgbotapi.FileID("AgACAgIAAxkDAALesF8dCjAAAa_…")
+```
+
+## `FileURL`
+
+A URL to an existing resource. It must be served with a correct MIME type to
+work as expected.
+
+```go
+file := tgbotapi.FileURL("https://i.imgur.com/unQLJIb.jpg")
+```
+
+## `FileReader`
+
+Use an `io.Reader` to provide file contents as needed. Requires a filename for
+the virtual file.
+
+```go
+var reader io.Reader
+
+file := tgbotapi.FileReader{
+    Name: "image.jpg",
+    Reader: reader,
+}
+```
+
+## `FileBytes`
+
+Use a `[]byte` to provide file contents. Generally try to avoid this as it
+results in high memory usage. Also requires a filename for the virtual file.
+
+```go
+var data []byte
+
+file := tgbotapi.FileBytes{
+    Name: "image.jpg",
+    Bytes: data,
+}
+```

docs/getting-started/important-notes.md

@@ -0,0 +1,56 @@
+# Important Notes
+
+The Telegram Bot API has a few potentially unanticipated behaviors. Here are a
+few of them. If any behavior was surprising to you, please feel free to open a
+pull request!
+
+## Callback Queries
+
+- Every callback query must be answered, even if there is nothing to display to
+  the user. Failure to do so will show a loading icon on the keyboard until the
+  operation times out.
+
+## ChatMemberUpdated
+
+- In order to receive `ChatMember` updates, you must explicitly add
+  `UpdateTypeChatMember` to your `AllowedUpdates` when getting updates or
+  setting your webhook.
+
+## Entities use UTF16
+
+- When extracting text entities using offsets and lengths, characters can appear
+  to be in incorrect positions. This is because Telegram uses UTF16 lengths
+  while Golang uses UTF8. It's possible to convert between the two, see
+  [issue #231][issue-231] for more details.
+
+[issue-231]: https://github.com/go-telegram-bot-api/telegram-bot-api/issues/231
+
+## GetUpdatesChan
+
+- This method is very basic and likely unsuitable for production use. Consider
+  creating your own implementation instead, as it's very simple to replicate.
+- This method only allows your bot to process one update at a time. You can
+  spawn goroutines to handle updates concurrently or switch to webhooks instead.
+  Webhooks are suggested for high traffic bots.
+
+## Nil Updates
+
+- At most one of the fields in an `Update` will be set to a non-nil value. When
+  evaluating updates, you must make sure you check that the field is not nil
+  before trying to access any of it's fields.
+
+## Privacy Mode
+
+- By default, bots only get updates directly addressed to them. If you need to
+  get all messages, you must disable privacy mode with Botfather. Bots already
+  added to groups will need to be removed and readded for the changes to take
+  effect. You can read more on the [Telegram Bot API docs][api-docs].
+
+[api-docs]: https://core.telegram.org/bots/faq#what-messages-will-my-bot-get
+
+## User and Chat ID size
+
+- These types require up to 52 significant bits to store correctly, making a
+  64-bit integer type required in most languages. They are already `int64` types
+  in this library, but make sure you use correct types when saving them to a
+  database or passing them to another language.

docs/getting-started/library-structure.md

@@ -0,0 +1,37 @@
+# Library Structure
+
+This library is generally broken into three components you need to understand.
+
+## Configs
+
+Configs are collections of fields related to a single request. For example, if
+one wanted to use the `sendMessage` endpoint, you could use the `MessageConfig`
+struct to configure the request. There is a one-to-one relationship between
+Telegram endpoints and configs. They generally have the naming pattern of
+removing the `send` prefix and they all end with the `Config` suffix. They
+generally implement the `Chattable` interface. If they can send files, they
+implement the `Fileable` interface.
+
+## Helpers
+
+Helpers are easier ways of constructing common Configs. Instead of having to
+create a `MessageConfig` struct and remember to set the `ChatID` and `Text`,
+you can use the `NewMessage` helper method. It takes the two required parameters
+for the request to succeed. You can then set fields on the resulting
+`MessageConfig` after it's creation. They are generally named the same as
+method names except with `send` replaced with `New`.
+
+## Methods
+
+Methods are used to send Configs after they are constructed. Generally,
+`Request` is the lowest level method you'll have to call. It accepts a
+`Chattable` parameter and knows how to upload files if needed. It returns an
+`APIResponse`, the most general return type from the Bot API. This method is
+called for any endpoint that doesn't have a more specific return type. For
+example, `setWebhook` only returns `true` or an error. Other methods may have
+more specific return types. The `getFile` endpoint returns a `File`. Almost
+every other method returns a `Message`, which you can use `Send` to obtain.
+
+There's lower level methods such as `MakeRequest` which require an endpoint and
+parameters instead of accepting configs. These are primarily used internally.
+If you find yourself having to use them, please open an issue.

docs/internals/README.md

@@ -0,0 +1,4 @@
+# Internals
+
+If you want to contribute to the project, here's some more information about
+the internal structure of the library.

docs/internals/adding-endpoints.md

@@ -0,0 +1,195 @@
+# Adding Endpoints
+
+This is mostly useful if you've managed to catch a new Telegram Bot API update
+before the library can get updated. It's also a great source of information
+about how the types work internally.
+
+## Creating the Config
+
+The first step in adding a new endpoint is to create a new Config type for it.
+These belong in `configs.go`.
+
+Let's try and add the `deleteMessage` endpoint. We can see it requires two
+fields; `chat_id` and `message_id`. We can create a struct for these.
+
+```go
+type DeleteMessageConfig struct {
+	ChatID    ???
+	MessageID int
+}
+```
+
+What type should `ChatID` be? Telegram allows specifying numeric chat IDs or channel usernames. Golang doesn't have union types, and interfaces are entirely
+untyped. This library solves this by adding two fields, a `ChatID` and a
+`ChannelUsername`. We can now write the struct as follows.
+
+```go
+type DeleteMessageConfig struct {
+	ChannelUsername string
+	ChatID          int64
+	MessageID       int
+}
+```
+
+Note that `ChatID` is an `int64`. Telegram chat IDs can be greater than 32 bits.
+
+Okay, we now have our struct. But we can't send it yet. It doesn't implement
+`Chattable` so it won't work with `Request` or `Send`.
+
+### Making it `Chattable`
+
+We can see that `Chattable` only requires a few methods.
+
+```go
+type Chattable interface {
+	params() (Params, error)
+	method() string
+}
+```
+
+`params` is the fields associated with the request. `method` is the endpoint
+that this Config is associated with.
+
+Implementing the `method` is easy, so let's start with that.
+
+```go
+func (config DeleteMessageConfig) method() string {
+	return "deleteMessage"
+}
+```
+
+Now we have to add the `params`. The `Params` type is an alias for
+`map[string]string`. Telegram expects only a single field for `chat_id`, so we
+have to determine what data to send.
+
+We could use an if statement to determine which field to get the value from.
+However, as this is a relatively common operation, there's helper methods for
+`Params`. We can use the `AddFirstValid` method to go through each possible
+value and stop when it discovers a valid one. Before writing your own Config,
+it's worth taking a look through `params.go` to see what other helpers exist.
+
+Now we can take a look at what a completed `params` method looks like.
+
+```go
+func (config DeleteMessageConfig) params() (Params, error) {
+	params := make(Params)
+
+	params.AddFirstValid("chat_id", config.ChatID, config.ChannelUsername)
+	params.AddNonZero("message_id", config.MessageID)
+
+	return params, nil
+}
+```
+
+### Uploading Files
+
+Let's imagine that for some reason deleting a message requires a document to be
+uploaded and an optional thumbnail for that document. To add file upload
+support we need to implement `Fileable`. This only requires one additional
+method.
+
+```go
+type Fileable interface {
+	Chattable
+	files() []RequestFile
+}
+```
+
+First, let's add some fields to store our files in. Most of the standard Configs
+have similar fields for their files.
+
+```diff
+ type DeleteMessageConfig struct {
+     ChannelUsername string
+     ChatID          int64
+     MessageID       int
++    Delete          interface{}
++    Thumb           interface{}
+ }
+```
+
+Adding another method is pretty simple. We'll always add a file named `delete`
+and add the `thumb` file if we have one.
+
+```go
+func (config DeleteMessageConfig) files() []RequestFile {
+	files := []RequestFile{{
+		Name: "delete",
+		File: config.Delete,
+	}}
+
+	if config.Thumb != nil {
+		files = append(files, RequestFile{
+			Name: "thumb",
+			File: config.Thumb,
+		})
+	}
+
+	return files
+}
+```
+
+And now our files will upload! It will transparently handle uploads whether File is a string with a path to a file, `FileURL`, `FileBytes`, `FileReader`, or `FileID`.
+
+### Base Configs
+
+Certain Configs have repeated elements. For example, many of the items sent to a
+chat have `ChatID` or `ChannelUsername` fields, along with `ReplyToMessageID`,
+`ReplyMarkup`, and `DisableNotification`. Instead of implementing all of this
+code for each item, there's a `BaseChat` that handles it for your Config.
+Simply embed it in your struct to get all of those fields.
+
+There's only a few fields required for the `MessageConfig` struct after
+embedding the `BaseChat` struct.
+
+```go
+type MessageConfig struct {
+	BaseChat
+	Text                  string
+	ParseMode             string
+	DisableWebPagePreview bool
+}
+```
+
+It also inherits the `params` method from `BaseChat`. This allows you to call
+it, then you only have to add your new fields.
+
+```go
+func (config MessageConfig) params() (Params, error) {
+	params, err := config.BaseChat.params()
+	if err != nil {
+		return params, err
+	}
+
+	params.AddNonEmpty("text", config.Text)
+	// Add your other fields
+
+	return params, nil
+}
+```
+
+Similarly, there's a `BaseFile` struct for adding an associated file and
+`BaseEdit` struct for editing messages.
+
+## Making it Friendly
+
+After we've got a Config type, we'll want to make it more user-friendly. We can
+do this by adding a new helper to `helpers.go`. These are functions that take
+in the required data for the request to succeed and populate a Config.
+
+Telegram only requires two fields to call `deleteMessage`, so this will be fast.
+
+```go
+func NewDeleteMessage(chatID int64, messageID int) DeleteMessageConfig {
+	return DeleteMessageConfig{
+		ChatID:    chatID,
+		MessageID: messageID,
+	}
+}
+```
+
+Sometimes it makes sense to add more helpers if there's methods where you have
+to set exactly one field. You can also add helpers that accept a `username`
+string for channels if it's a common operation.
+
+And that's it! You've added a new method.

docs/internals/uploading-files.md

@@ -0,0 +1,108 @@
+# Uploading Files
+
+To make files work as expected, there's a lot going on behind the scenes. Make
+sure to read through the [Files](../getting-started/files.md) section in
+Getting Started first as we'll be building on that information.
+
+This section only talks about file uploading. For non-uploaded files such as
+URLs and file IDs, you just need to pass a string.
+
+## Fields
+
+Let's start by talking about how the library represents files as part of a
+Config.
+
+### Static Fields
+
+Most endpoints use static file fields. For example, `sendPhoto` expects a single
+file named `photo`. All we have to do is set that single field with the correct
+value (either a string or multipart file). Methods like `sendDocument` take two
+file uploads, a `document` and a `thumb`. These are pretty straightforward.
+
+Remembering that the `Fileable` interface only requires one method, let's
+implement it for `DocumentConfig`.
+
+```go
+func (config DocumentConfig) files() []RequestFile {
+    // We can have multiple files, so we'll create an array. We also know that
+    // there always is a document file, so initialize the array with that.
+	files := []RequestFile{{
+		Name: "document",
+		File: config.File,
+	}}
+
+    // We'll only add a file if we have one.
+	if config.Thumb != nil {
+		files = append(files, RequestFile{
+			Name: "thumb",
+			File: config.Thumb,
+		})
+	}
+
+	return files
+}
+```
+
+Telegram also supports the `attach://` syntax (discussed more later) for
+thumbnails, but there's no reason to make things more complicated.
+
+### Dynamic Fields
+
+Of course, not everything can be so simple. Methods like `sendMediaGroup`
+can accept many files, and each file can have custom markup. Using a static
+field isn't possible because we need to specify which field is attached to each
+item. Telegram introduced the `attach://` syntax for this.
+
+Let's follow through creating a new media group with string and file uploads.
+
+First, we start by creating some `InputMediaPhoto`.
+
+```go
+photo := tgbotapi.NewInputMediaPhoto("tests/image.jpg")
+url := tgbotapi.NewInputMediaPhoto(tgbotapi.FileURL("https://i.imgur.com/unQLJIb.jpg"))
+```
+
+This created a new `InputMediaPhoto` struct, with a type of `photo` and the
+media interface that we specified.
+
+We'll now create our media group with the photo and URL.
+
+```go
+mediaGroup := NewMediaGroup(ChatID, []interface{}{
+    photo,
+    url,
+})
+```
+
+A `MediaGroupConfig` stores all of the media in an array of interfaces. We now
+have all of the data we need to upload, but how do we figure out field names for
+uploads? We didn't specify `attach://unique-file` anywhere.
+
+When the library goes to upload the files, it looks at the `params` and `files`
+for the Config. The params are generated by transforming the file into a value
+more suitable for uploading, file IDs and URLs are untouched but uploaded types
+are all changed into `attach://file-%d`. When collecting a list of files to
+upload, it names them the same way. This creates a nearly transparent way of
+handling multiple files in the background without the user having to consider
+what's going on.
+
+## Library Processing
+
+If at some point in the future new upload types are required, let's talk about
+where the current types are used.
+
+Upload types are defined in `configs.go`. Where possible, type aliases are
+preferred. Structs can be used when multiple fields are required.
+
+The main usage of the upload types happens in `UploadFiles`. It switches on each
+file's type in order to determine how to upload it. Files that aren't uploaded
+(file IDs, URLs) are converted back into strings and passed through as strings
+into the correct field. Uploaded types are processed as needed (opening files,
+etc.) and written into the form using a copy approach in a goroutine to reduce
+memory usage.
+
+In addition to `UploadFiles`, there's more processing of upload types in the
+`prepareInputMediaParam` and `prepareInputMediaFile` functions. These look at
+the `InputMedia` types to determine which files are uploaded and which are
+passed through as strings. They only need to be aware of which files need to be
+replaced with `attach://` fields.