Discord Rich Presence from Nexium

statusmith is a tray app for custom Discord Rich Presence, and its nexium/ directory is the same protocol written in Nexium, with no dependency on the app: open the local pipe, handshake, set_activity, clear, close, in about three hundred lines. It is the first package outside this repository, and the shape a package beside an app takes (dir, in packages).

nx add discord_rpc --git https://github.com/Londopy/statusmith --tag sdk-v0.1.0 --dir nexium

A card on your profile#

import discord_rpc

fn main() -> !void {
    var a = discord_rpc.activity()
    a.details = String.from("writing the compiler in itself")
    a.state = String.from("1.5.0")
    a.start_ms = time.now()                                      // an elapsed timer
    var client = try discord_rpc.connect("1234567890123456789")  // your Application ID
    let headline = try client.set_activity(&a)                   // "Playing <headline>"
    println("on your profile: {}", .{headline})
    ...
    try client.clear()
    client.close()                                               // Discord clears the card
}

activity() is a card with nothing on it; the fields are details and state (the two lines), kind (playing, listening, watching, competing), large_image, large_text, small_image, small_text (an Art Assets key or an https:// link), start_ms and end_ms (an elapsed timer or a countdown), and two buttons with a label and a URL. Empty strings and zero timestamps are left out of the request. connect(app_id) opens \\.\pipe\discord-ipc-N and handshakes; set_activity(&a) returns the application's name; the presence stays up while the connection is open.

What to know#

• The Application ID comes from the Discord Developer Portal; no token is involved anywhere, and nothing but the local pipe is spoken to.
• Windows only for now: the pipe path is the one platform-specific part (the Unix socket variant is a small change in open_pipe).
• The pipe is driven through the C runtime's unbuffered _open, _read and _write via @cImport("io.h"), because a FILE* cannot switch from reading to writing without a seek, and pipes cannot seek.
• connect fails with error.IoError when Discord is not running, and with a message from Discord when the Application ID is not accepted; the Topo's example prints what the card would have said instead.
• nexium/examples/presence.nx in statusmith is a command-line front end: nx run presence.nx -- --app ID --details "the build" --elapsed --hold 600.

A bot#

For a bot, the second package outside this repository is nexium-discord: the gateway (identify, heartbeats, resume, reconnects), the REST calls a bot makes (messages, reactions, slash commands and their answers, and any other call with Discord's rate limits waited out), and the events as an enum to match on. It speaks through std.websocket and std.http, with TLS from nxtls in the TLS slot, or the platform's own TLS where there is no certificate bundle (Windows), so it needs Nexium 1.4 or later and runs on Linux, macOS, the BSDs and Windows.

[dependencies]
discord = { git = "https://github.com/Londopy/nexium-discord", tag = "v0.2.0" }

Its pingbot answers /ping and !ping; the token comes from $DISCORD_TOKEN.