D2

General-purpose assistant for Discord, IRC and Telegram featuring more than 300 commands, including:

• 💬 Various useful chat utilities, e.g. polls or coin flips
• ⚙️ A flexible command system that supports chaining, piping and permissions
• 🎲 Multiplayer board and card games, such as chess or Uno
• 📙 Integration with a wide range of web APIs, including WolframAlpha, MediaWiki, Reddit and OpenWeatherMap
• 🖼 Image processing capabilities, including generation of animated GIFs
• 📊 Tools for mathematics and linear algebra, e.g. a linear system solver
• 🎵 Music theory utilities, including a chord finder
• 🖥 Programming tools, including a Haskell API search and a Prolog interpreter
• 🍬 Humorous commands, e.g. for jokes

Installation

using Docker (for production environments)

• Make sure to have recent versions of Docker and Docker Compose installed
• Create a volume named d2local using docker volume create d2local

manually (for local development)

System Dependencies

• Linux or macOS 10.15+
• Swift 5.4+
  • Swift can be installed conveniently using a version manager such as swiftenv
  • Current builds of Swift for Raspberry Pi can be found here
    • Note that you might need to perform a custom installation if you use swiftenv on Raspberry Pi
• Haskell + Cabal Install or Stack (for Hoogle, Pointfree, ...)
• Node.js and npm (for LaTeX rendering)
• timeout and kill (for MaximaCommand)

Linux

• sudo apt-get install libssl1.0-dev libcairo2-dev poppler-utils maxima libsqlite3-dev graphviz libgraphviz-dev libtesseract-dev libleptonica-dev
  • Note that you might need to use libssl-dev instead of libssl1.0-dev on Ubuntu
  • If Swift cannot find the Freetype headers despite libfreetype6-dev being installed, you may need to add symlinks:
    • mkdir /usr/include/freetype2/freetype
    • ln -s /usr/include/freetype2/freetype.h /usr/include/freetype2/freetype/freetype.h
    • ln -s /usr/include/freetype2/tttables.h /usr/include/freetype2/freetype/tttables.h
  • Note that you might need to apt-get install clang separately on a Raspberry Pi
  • Also make sure that you are installing Tesseract 4. If you are on an older version of Ubuntu, try adding the following repository:
    • sudo add-apt-repository ppa:alex-p/tesseract-ocr

macOS

• Install maxima
• brew tap vapor/tap
• brew install ctls cairo poppler gd graphviz

General

• stack install happy show mueval pointfree pointful (or cabal-install ...)
• cd Node && ./install-all

Configuration

Required

• Create a folder named local in the repository
  • If you use Docker, the local folder is represented by the d2local volume
  • See here for instructions on how to copy files into it
• Create a file named platformTokens.json in local containing the API tokens (at least one of them should be specified):

{
    "discord": "YOUR_DISCORD_API_TOKEN",
    "telegram": "YOUR_TELEGRAM_API_TOKEN",
    "irc": [
        {
            "host": "YOUR_IRC_HOST",
            "port": 6667,
            "nickname": "YOUR_IRC_USERNAME",
            "password": "YOUR_IRC_PASSWORD"
        }
    ]
}

For more information e.g. on how to connect to the Twitch IRC API, see this guide

Optional

• Create a file named config.json in local (or the d2local volume):

{
    "prefix": "%"
}

• Create a file named adminWhitelist.json in local (or the d2local volume) containing a list of Discord usernames that have full permissions:

{
    "users": [
        "YOUR_USERNAME#1234"
    ]
}

• Create a file named netApiKeys.json in local (or the d2local volume) containing various API keys:

{
    "mapQuest": "YOUR_MAP_QUEST_KEY",
    "wolframAlpha": "YOUR_WOLFRAM_ALPHA_KEY",
    "gitlab": "YOUR_GITLAB_PERSONAL_ACCESS_TOKEN"
}

• Create a folder named memeTemplates in local containing PNG images. Any fully transparent sections will be filled by a user-defined image, once the corresponding command is invoked.

Building

• Using Docker: docker-compose build
• On Linux: swift build
• On macOS: swift build -Xlinker -L/usr/local/lib -Xlinker -lopus -Xcc -I/usr/local/include

For Xcode support, see [the README of Discord.(https://github.com/nuclearace/Discord.blob/master/README.md).

Testing

• swift test

Running

• Using Docker: docker-compose up -d
• On Linux: swift run D2
• On macOS: swift run -Xlinker -L/usr/local/lib -Xlinker -lopus -Xcc -I/usr/local/include D2

Additional Build Flags

To suppress warnings, you can use -Xswiftc -suppress-warnings after swift build or swift run.

Architecture

The program consists of a single executable:

• D2, the main Discord frontend

This executable depends on several library targets:

• D2Handlers, top-level message/event handling
• D2Commands, the command framework and the implementations
• D2MessageIO, the messaging framework (abstracting over the Discord library)
  • D2DiscordIO, the Discord implementation
  • D2TelegramIO, the Telegram implementation
  • D2IRCIO, the IRC/Twitch implementation
• D2Permissions, permission management
• D2Script, an experimental DSL that can be used to script commands
• D2NetAPIs, client implementations of various web APIs

D2

The executable application. Sets up messaging backends (like Discord) and the top-level event handler (D2Delegate). Besides other events, the D2Delegate handles incoming messages and forwards them to multiple MessageHandlers. One of these is CommandHandler, which in turn parses the command and invokes the actual command.

D2Commands

At a basic level, the Command protocol consists of a single method named invoke that carries information about the user's request:

protocol Command: class {
    ...

    func invoke(with input: RichValue, output: CommandOutput, context: CommandContext)

    ...
}

The arguments each represent a part of the invocation context. Given a request such as %commandname arg1 arg2, the implementor would receive:

Parameter	Value
input	.text("arg1 arg2")
output	DiscordOutput
context	CommandContext containing the message, the client and the command registry

Since output: CommandOutput represents a polymorphic object, the output of an invocation does not necessarily get sent to the Discord channel where the request originated from. For example, if the user creates a piped request such as %first | second | third, only the third command would operate on a DiscordOutput. Both the first and the second command call a PipeOutput instead that passes any values to the next command:

class PipeOutput: CommandOutput {
    private let sink: Command
    private let context: CommandContext
    private let args: String
    private let next: CommandOutput?

    init(withSink sink: Command, context: CommandContext, args: String, next: CommandOutput? = nil) {
        self.sink = sink
        self.args = args
        self.context = context
        self.next = next
    }

    func append(_ value: RichValue) {
        let nextInput = args.isEmpty ? value : (.text(args) + value)
        sink.invoke(with: nextInput, output: next ?? PrintOutput(), context: context)
    }
}

Often the Command protocol is too low-level to be adopted directly, since the input can be of any form (including embeds or images). To address this, there are subprotocols that provide a simpler template interface for implementors:

protocol StringCommand: Command {
    func invoke(with input: String, output: CommandOutput, context: CommandContext)
}

StringCommand is useful when the command accepts a single string as an argument or if a custom argument parser is used. Its default implementation of Command.invoke passes either args, if not empty, or otherwise input.content to StringCommand.invoke.

protocol ArgCommand: Command {
    associatedtype Args: Arg

    var argPattern: Args { get }

    func invoke(withInputArgs inputArgs: [String], output: CommandOutput, context: CommandContext)
}

ArgCommand should be adopted if the command expects a fixed structure of arguments.