//! Native, cancellation-safe IRC/local-grid chat bridge.

use clap::Parser;
use libremetaverse::types::UUID;
use libremetaverse::types::compat::{CancellationToken, CancellationTokenSource, Subscription};
use libremetaverse::{
    AgentManager, ChatAudibleLevel, ChatEventArgs, ChatType, GridClient, InstantMessageDialog,
    InstantMessageEventArgs, LoginParams, LoginProgressEventArgs, NetworkManager,
};
use std::collections::VecDeque;
use std::fmt;
use std::fs::File;
use std::io::{self, BufRead, BufReader, Read, Write};
use std::path::{Path, PathBuf};
use std::process::ExitCode;
use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
use std::sync::{Arc, Mutex, MutexGuard};
use std::time::{Duration, Instant};
use tokio::io::{AsyncBufRead, AsyncBufReadExt, AsyncWriteExt, BufReader as AsyncBufReader};
use tokio::net::TcpStream;
use tokio::sync::mpsc;

pub const EXIT_SUCCESS: u8 = 0;
pub const EXIT_USAGE: u8 = 2;
pub const EXIT_INPUT: u8 = 3;
pub const EXIT_CLIENT: u8 = 4;

const MAX_SCRIPT_BYTES: u64 = 1024 * 1024;
const MAX_SCRIPT_EVENTS: usize = 4096;
const MAX_NAME_BYTES: usize = 256;
const MAX_MESSAGE_BYTES: usize = 4096;
const EVENT_QUEUE_CAPACITY: usize = 256;
const OUTBOUND_QUEUE_CAPACITY: usize = 128;
const BRIDGE_QUEUE_CAPACITY: usize = 64;
const IRC_LINE_BYTES: usize = 512;
const MAX_IRC_INPUT_BYTES: usize = 8192;
const DUPLICATE_WINDOW_MS: u64 = 2_000;
const LOOP_WINDOW_MS: u64 = 30_000;
const MAX_RECENT_MESSAGES: usize = 256;
const TICK_MS: u64 = 100;

#[derive(Parser)]
#[command(
    name = "irc-gateway",
    version,
    about = "Bridge one IRC channel and LibreMetaverse local chat",
    long_about = None,
    arg_required_else_help = true,
    after_help = "Live mode preserves the upstream positional interface. Offline scripts use tab-separated events: irc-connect, irc-disconnect, irc, grid-chat, grid-login, teleport, advance, and shutdown."
)]
struct Cli {
    /// Avatar first name. May also be supplied as `GRID_FIRST_NAME`.
    #[arg(value_name = "FIRSTNAME")]
    first_name: Option<String>,
    /// Avatar last name. May also be supplied as `GRID_LAST_NAME`.
    #[arg(value_name = "LASTNAME")]
    last_name: Option<String>,
    /// Avatar password. May also be supplied as `GRID_PASSWORD`.
    #[arg(value_name = "PASSWORD")]
    password: Option<String>,
    /// UUID whose teleport lures are accepted. May also be `GRID_MASTER_UUID`.
    #[arg(value_name = "MASTER_UUID")]
    master_uuid: Option<String>,
    /// IRC server host. May also be `IRC_HOST`.
    #[arg(value_name = "IRC_HOST")]
    irc_host: Option<String>,
    /// IRC server port. May also be `IRC_PORT`.
    #[arg(value_name = "IRC_PORT")]
    irc_port: Option<u16>,
    /// IRC channel, including its leading '#'. May also be `IRC_CHANNEL`.
    #[arg(value_name = "#CHANNEL")]
    channel: Option<String>,

    /// Run a deterministic, bounded offline bridge script.
    #[arg(long, value_name = "FILE")]
    fake_script: Option<PathBuf>,
    /// Channel used in fake mode when the positional channel is absent.
    #[arg(long, default_value = "#metacrate", value_name = "#CHANNEL")]
    fake_channel: String,
    /// Master UUID used in fake mode when the positional UUID is absent.
    #[arg(
        long,
        default_value = "11111111-2222-3333-4444-555555555555",
        value_name = "UUID"
    )]
    fake_master_uuid: String,
    /// IRC nickname.
    #[arg(long, default_value = "SLGateway", value_name = "NICK")]
    nickname: String,
    /// IRC real name sent during registration.
    #[arg(long, default_value = "Second Life Gateway", value_name = "TEXT")]
    real_name: String,
    /// Override the grid login endpoint; `GRID_LOGIN_URL` is the fallback.
    #[arg(long, value_name = "URL")]
    login_uri: Option<String>,
    /// Maximum time allowed for grid login.
    #[arg(long, default_value_t = 30, value_name = "SECONDS", value_parser = clap::value_parser!(u64).range(1..=300))]
    login_timeout_seconds: u64,
    /// Per-direction bridge rate, in messages per second.
    #[arg(long, default_value_t = 4, value_name = "COUNT", value_parser = clap::value_parser!(u32).range(1..=100))]
    messages_per_second: u32,
    /// Per-direction burst capacity.
    #[arg(long, default_value_t = 4, value_name = "COUNT", value_parser = clap::value_parser!(u32).range(1..=100))]
    burst: u32,
}

struct LiveConfig {
    first_name: String,
    last_name: String,
    password: String,
    master: UUID,
    irc_host: String,
    irc_port: u16,
    bridge: BridgeConfig,
    real_name: String,
    login_uri: Option<String>,
    login_timeout: Duration,
}

#[derive(Clone)]
struct BridgeConfig {
    channel: String,
    nickname: String,
    messages_per_second: u32,
    burst: u32,
}

#[derive(Debug)]
enum ProgramError {
    Usage(&'static str),
    Io { action: String, source: io::Error },
    InvalidScript { line: usize, reason: &'static str },
    Client(&'static str),
    LoginFailed,
    LoginTimedOut,
    Signal,
}

impl ProgramError {
    const fn exit_code(&self) -> u8 {
        match self {
            Self::Usage(_) => EXIT_USAGE,
            Self::Io { .. } | Self::InvalidScript { .. } => EXIT_INPUT,
            Self::Client(_) | Self::LoginFailed | Self::LoginTimedOut | Self::Signal => EXIT_CLIENT,
        }
    }
}

impl fmt::Display for ProgramError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Usage(message) => f.write_str(message),
            Self::Io { action, source } => write!(f, "{action}: {source}"),
            Self::InvalidScript { line, reason } => {
                write!(f, "invalid bridge script at line {line}: {reason}")
            }
            Self::Client(operation) => write!(f, "native client operation failed: {operation}"),
            Self::LoginFailed => f.write_str("grid login failed"),
            Self::LoginTimedOut => f.write_str("grid login timed out"),
            Self::Signal => f.write_str("could not install the Ctrl-C handler"),
        }
    }
}

#[derive(Clone, Debug)]
enum BridgeEvent {
    IrcConnected,
    IrcDisconnected,
    IrcMessage {
        target: String,
        nick: String,
        message: String,
    },
    GridChat {
        source_id: UUID,
        name: String,
        message: String,
        normal: bool,
        fully_audible: bool,
    },
    GridLogin(String),
    OwnGridId(UUID),
    Teleport {
        source_id: UUID,
        session_id: UUID,
    },
}

trait BridgeTransport {
    fn join_irc(&mut self, channel: &str) -> Result<(), &'static str>;
    fn send_irc(&mut self, channel: &str, message: &str) -> Result<(), &'static str>;
    fn send_grid(&mut self, message: &str) -> Result<(), &'static str>;
    fn accept_teleport(&mut self, source: UUID, session: UUID) -> Result<(), &'static str>;
}

#[derive(Clone, Copy, Eq, PartialEq)]
enum Direction {
    ToIrc,
    ToGrid,
}

struct PendingMessage {
    direction: Direction,
    message: String,
}

struct RecentMessage {
    direction: Direction,
    message: String,
    at_ms: u64,
}

struct TokenBucket {
    milli_tokens: u64,
    last_ms: u64,
    rate: u64,
    burst_milli: u64,
}

impl TokenBucket {
    fn new(rate: u32, burst: u32) -> Self {
        Self {
            milli_tokens: u64::from(burst) * 1_000,
            last_ms: 0,
            rate: u64::from(rate),
            burst_milli: u64::from(burst) * 1_000,
        }
    }

    fn take(&mut self, now_ms: u64) -> bool {
        let elapsed = now_ms.saturating_sub(self.last_ms);
        self.last_ms = now_ms;
        self.milli_tokens = self
            .milli_tokens
            .saturating_add(elapsed.saturating_mul(self.rate))
            .min(self.burst_milli);
        if self.milli_tokens >= 1_000 {
            self.milli_tokens -= 1_000;
            true
        } else {
            false
        }
    }
}

struct Bridge {
    config: BridgeConfig,
    master: UUID,
    own_grid_id: UUID,
    irc_connected: bool,
    pending: VecDeque<PendingMessage>,
    recent: VecDeque<RecentMessage>,
    inbound_recent: VecDeque<RecentMessage>,
    irc_rate: TokenBucket,
    grid_rate: TokenBucket,
    dropped: usize,
}

impl Bridge {
    fn new(config: BridgeConfig, master: UUID, own_grid_id: UUID) -> Self {
        Self {
            irc_rate: TokenBucket::new(config.messages_per_second, config.burst),
            grid_rate: TokenBucket::new(config.messages_per_second, config.burst),
            config,
            master,
            own_grid_id,
            irc_connected: false,
            pending: VecDeque::new(),
            recent: VecDeque::new(),
            inbound_recent: VecDeque::new(),
            dropped: 0,
        }
    }

    fn handle(
        &mut self,
        event: BridgeEvent,
        now_ms: u64,
        transport: &mut dyn BridgeTransport,
        log: &dyn BridgeLogger,
    ) {
        self.expire_recent(now_ms);
        match event {
            BridgeEvent::IrcConnected => {
                self.irc_connected = true;
                if let Err(error) = transport.join_irc(&self.config.channel) {
                    log.line(format!("IRC join failed: {error}"));
                } else {
                    log.line(format!("IRC connected; joined {}", self.config.channel));
                }
            }
            BridgeEvent::IrcDisconnected => {
                self.irc_connected = false;
                log.line("IRC disconnected; reconnect scheduled".into());
            }
            BridgeEvent::IrcMessage {
                target,
                nick,
                message,
            } => {
                if !irc_eq(&target, &self.config.channel)
                    || irc_eq(&nick, &self.config.nickname)
                    || !valid_message(&message)
                {
                    return;
                }
                let message = clean_message(&message);
                if self.is_loop(Direction::ToGrid, &message, now_ms) {
                    log.line("Suppressed duplicate/loop IRC message".into());
                    return;
                }
                let formatted = format!("<{}> {}", map_name(&nick), message);
                if self.is_duplicate(Direction::ToGrid, &formatted, now_ms) {
                    log.line("Suppressed duplicate/loop IRC message".into());
                    return;
                }
                self.remember_inbound(Direction::ToGrid, &formatted, now_ms);
                self.enqueue(Direction::ToGrid, formatted);
            }
            BridgeEvent::GridChat {
                source_id,
                name,
                message,
                normal,
                fully_audible,
            } => {
                if source_id == self.own_grid_id
                    || !normal
                    || !fully_audible
                    || !valid_message(&message)
                {
                    return;
                }
                let message = clean_message(&message);
                if self.is_loop(Direction::ToIrc, &message, now_ms) {
                    log.line("Suppressed duplicate/loop grid message".into());
                    return;
                }
                let formatted = format!("<{}> {}", map_name(&name), message);
                if self.is_duplicate(Direction::ToIrc, &formatted, now_ms) {
                    log.line("Suppressed duplicate/loop grid message".into());
                    return;
                }
                self.remember_inbound(Direction::ToIrc, &formatted, now_ms);
                self.enqueue(Direction::ToIrc, formatted);
            }
            BridgeEvent::GridLogin(message) => {
                if valid_message(&message) {
                    self.enqueue(Direction::ToIrc, redact_text(&clean_message(&message)));
                }
            }
            BridgeEvent::OwnGridId(agent_id) => self.own_grid_id = agent_id,
            BridgeEvent::Teleport {
                source_id,
                session_id,
            } => {
                if source_id == self.master {
                    if let Err(error) = transport.accept_teleport(source_id, session_id) {
                        log.line(format!("Teleport response failed: {error}"));
                    } else {
                        log.line("Accepted teleport lure from configured master".into());
                    }
                }
            }
        }
        self.flush(now_ms, transport, log);
    }

    fn tick(&mut self, now_ms: u64, transport: &mut dyn BridgeTransport, log: &dyn BridgeLogger) {
        self.expire_recent(now_ms);
        self.flush(now_ms, transport, log);
    }

    fn enqueue(&mut self, direction: Direction, message: String) {
        if self.pending.len() == BRIDGE_QUEUE_CAPACITY {
            self.pending.pop_front();
            self.dropped += 1;
        }
        self.pending
            .push_back(PendingMessage { direction, message });
    }

    fn flush(&mut self, now_ms: u64, transport: &mut dyn BridgeTransport, log: &dyn BridgeLogger) {
        let mut retained = VecDeque::with_capacity(self.pending.len());
        while let Some(item) = self.pending.pop_front() {
            let permitted = match item.direction {
                Direction::ToIrc => self.irc_connected && self.irc_rate.take(now_ms),
                Direction::ToGrid => self.grid_rate.take(now_ms),
            };
            if !permitted {
                retained.push_back(item);
                continue;
            }
            let result = match item.direction {
                Direction::ToIrc => transport.send_irc(&self.config.channel, &item.message),
                Direction::ToGrid => transport.send_grid(&item.message),
            };
            match result {
                Ok(()) => {
                    self.recent.push_back(RecentMessage {
                        direction: item.direction,
                        message: item.message.clone(),
                        at_ms: now_ms,
                    });
                    log.line(format!(
                        "[{}] {}",
                        if item.direction == Direction::ToIrc {
                            "Grid->IRC"
                        } else {
                            "IRC->Grid"
                        },
                        item.message
                    ));
                }
                Err(error) => {
                    log.line(format!("Bridge send failed: {error}"));
                    retained.push_front(item);
                    break;
                }
            }
        }
        retained.append(&mut self.pending);
        self.pending = retained;
        while self.recent.len() > MAX_RECENT_MESSAGES {
            self.recent.pop_front();
        }
    }

    fn is_loop(&self, direction: Direction, message: &str, now_ms: u64) -> bool {
        let opposite = if direction == Direction::ToIrc {
            Direction::ToGrid
        } else {
            Direction::ToIrc
        };
        self.recent.iter().any(|recent| {
            recent.direction == opposite
                && recent.message == message
                && now_ms.saturating_sub(recent.at_ms) <= LOOP_WINDOW_MS
        })
    }

    fn is_duplicate(&self, direction: Direction, message: &str, now_ms: u64) -> bool {
        self.inbound_recent.iter().any(|recent| {
            recent.direction == direction
                && recent.message == message
                && now_ms.saturating_sub(recent.at_ms) <= DUPLICATE_WINDOW_MS
        })
    }

    fn remember_inbound(&mut self, direction: Direction, message: &str, now_ms: u64) {
        self.inbound_recent.push_back(RecentMessage {
            direction,
            message: message.into(),
            at_ms: now_ms,
        });
        while self.inbound_recent.len() > MAX_RECENT_MESSAGES {
            self.inbound_recent.pop_front();
        }
    }

    fn expire_recent(&mut self, now_ms: u64) {
        self.recent
            .retain(|entry| now_ms.saturating_sub(entry.at_ms) <= LOOP_WINDOW_MS);
        self.inbound_recent
            .retain(|entry| now_ms.saturating_sub(entry.at_ms) <= DUPLICATE_WINDOW_MS);
    }
}

trait BridgeLogger: Send + Sync {
    fn line(&self, line: String);
}

struct ConsoleLogger;

impl BridgeLogger for ConsoleLogger {
    fn line(&self, line: String) {
        println!("{}", redact_text(&line));
    }
}

#[derive(Default)]
struct ScriptTransport {
    calls: Vec<String>,
}

impl BridgeTransport for ScriptTransport {
    fn join_irc(&mut self, channel: &str) -> Result<(), &'static str> {
        self.calls.push(format!("CALL irc-join {channel}"));
        Ok(())
    }
    fn send_irc(&mut self, channel: &str, message: &str) -> Result<(), &'static str> {
        self.calls
            .push(format!("CALL irc-privmsg {channel} {message}"));
        Ok(())
    }
    fn send_grid(&mut self, message: &str) -> Result<(), &'static str> {
        self.calls
            .push(format!("CALL grid-chat channel=0 type=Normal {message}"));
        Ok(())
    }
    fn accept_teleport(&mut self, source: UUID, session: UUID) -> Result<(), &'static str> {
        self.calls.push(format!(
            "CALL teleport-lure-respond {source} {session} accept=true"
        ));
        Ok(())
    }
}

struct LiveGrid {
    client: Mutex<GridClient>,
    network: NetworkManager,
    subscriptions: Mutex<Vec<Subscription>>,
    shutdown: AtomicBool,
}

impl LiveGrid {
    fn new(client: GridClient, network: NetworkManager) -> Self {
        Self {
            client: Mutex::new(client),
            network,
            subscriptions: Mutex::new(Vec::new()),
            shutdown: AtomicBool::new(false),
        }
    }

    fn with_agent<T>(&self, action: impl FnOnce(&mut AgentManager) -> T) -> T {
        action(lock(&self.client).self_())
    }

    fn install(self: &Arc<Self>, sender: &mpsc::Sender<BridgeEvent>, dropped: &Arc<AtomicUsize>) {
        let chat_sender = sender.clone();
        let chat_dropped = Arc::clone(dropped);
        let chat = self.with_agent(|agent| {
            agent.subscribe_chat_from_simulator(Arc::new(move |event: ChatEventArgs| {
                try_event(
                    &chat_sender,
                    BridgeEvent::GridChat {
                        source_id: event.source_id(),
                        name: event.from_name(),
                        message: event.message(),
                        normal: event.type_() == ChatType::Normal,
                        fully_audible: event.audible_level() == ChatAudibleLevel::Fully,
                    },
                    &chat_dropped,
                );
            }))
        });
        let im_sender = sender.clone();
        let im_dropped = Arc::clone(dropped);
        let im = self.with_agent(|agent| {
            agent.subscribe_im(Arc::new(move |event: InstantMessageEventArgs| {
                let im = event.im();
                if im.dialog == InstantMessageDialog::RequestTeleport {
                    try_event(
                        &im_sender,
                        BridgeEvent::Teleport {
                            source_id: im.from_agent_id,
                            session_id: im.im_session_id,
                        },
                        &im_dropped,
                    );
                }
            }))
        });
        let progress_sender = sender.clone();
        let progress_dropped = Arc::clone(dropped);
        let progress = self.network.subscribe_login_progress(Arc::new(
            move |event: LoginProgressEventArgs| {
                try_event(
                    &progress_sender,
                    BridgeEvent::GridLogin(event.message()),
                    &progress_dropped,
                );
            },
        ));
        *lock(&self.subscriptions) = vec![chat, im, progress];
    }

    fn shutdown(&self) {
        if self.shutdown.swap(true, Ordering::AcqRel) {
            return;
        }
        lock(&self.subscriptions).clear();
        let _ = self.network.logout_with_method();
        let mut client = lock(&self.client);
        let _ = client.self_().dispose();
        let _ = client.dispose_with_method();
    }
}

struct LiveTransport {
    grid: Arc<LiveGrid>,
    irc: mpsc::Sender<IrcCommand>,
}

impl BridgeTransport for LiveTransport {
    fn join_irc(&mut self, channel: &str) -> Result<(), &'static str> {
        self.irc
            .try_send(IrcCommand::Join(channel.into()))
            .map_err(|_| "IRC command queue full or closed")
    }
    fn send_irc(&mut self, channel: &str, message: &str) -> Result<(), &'static str> {
        self.irc
            .try_send(IrcCommand::Message(channel.into(), message.into()))
            .map_err(|_| "IRC command queue full or closed")
    }
    fn send_grid(&mut self, message: &str) -> Result<(), &'static str> {
        self.grid
            .with_agent(|agent| agent.chat(message.into(), 0, ChatType::Normal, Some(false)))
            .map_err(|_| "grid chat")
    }
    fn accept_teleport(&mut self, source: UUID, session: UUID) -> Result<(), &'static str> {
        self.grid
            .with_agent(|agent| agent.teleport_lure_respond(source, session, true))
            .map_err(|_| "teleport lure response")
    }
}

enum IrcCommand {
    Join(String),
    Message(String, String),
}

struct IrcRuntime {
    host: String,
    port: u16,
    nick: String,
    real_name: String,
    commands: mpsc::Receiver<IrcCommand>,
    events: mpsc::Sender<BridgeEvent>,
    dropped: Arc<AtomicUsize>,
    cancellation: CancellationToken,
}

#[must_use]
pub fn main_entry() -> ExitCode {
    let cli = Cli::parse();
    let Ok(runtime) = tokio::runtime::Builder::new_multi_thread()
        .enable_all()
        .build()
    else {
        eprintln!("irc-gateway: could not initialize the async runtime");
        return ExitCode::from(EXIT_CLIENT);
    };
    match runtime.block_on(run(cli)) {
        Ok(()) => ExitCode::from(EXIT_SUCCESS),
        Err(error) => {
            eprintln!("irc-gateway: {error}");
            ExitCode::from(error.exit_code())
        }
    }
}

async fn run(cli: Cli) -> Result<(), ProgramError> {
    if let Some(path) = cli.fake_script.clone() {
        return run_fake(&cli, &path);
    }
    run_live(resolve_live(cli)?).await
}

fn resolve_live(cli: Cli) -> Result<LiveConfig, ProgramError> {
    let first_name = required(
        cli.first_name,
        "GRID_FIRST_NAME",
        "FIRSTNAME is required (or set GRID_FIRST_NAME)",
    )?;
    let last_name = required(
        cli.last_name,
        "GRID_LAST_NAME",
        "LASTNAME is required (or set GRID_LAST_NAME)",
    )?;
    let password = required(
        cli.password,
        "GRID_PASSWORD",
        "PASSWORD is required (or set GRID_PASSWORD)",
    )?;
    let master_text = required(
        cli.master_uuid,
        "GRID_MASTER_UUID",
        "MASTER_UUID is required (or set GRID_MASTER_UUID)",
    )?;
    let master = UUID::new_with_string(master_text)
        .map_err(|_| ProgramError::Usage("MASTER_UUID is invalid"))?;
    let irc_host = required(cli.irc_host, "IRC_HOST", "IRC_HOST is required")?;
    let irc_port = cli
        .irc_port
        .or_else(|| std::env::var("IRC_PORT").ok()?.parse().ok())
        .ok_or(ProgramError::Usage(
            "IRC_PORT is required and must be 1..65535",
        ))?;
    if irc_port == 0 {
        return Err(ProgramError::Usage(
            "IRC_PORT is required and must be 1..65535",
        ));
    }
    let channel = required(cli.channel, "IRC_CHANNEL", "#CHANNEL is required")?;
    validate_channel(&channel)?;
    validate_nick(&cli.nickname)?;
    Ok(LiveConfig {
        first_name,
        last_name,
        password,
        master,
        irc_host,
        irc_port,
        bridge: BridgeConfig {
            channel,
            nickname: cli.nickname,
            messages_per_second: cli.messages_per_second,
            burst: cli.burst,
        },
        real_name: clean_message(&cli.real_name),
        login_uri: cli
            .login_uri
            .or_else(|| std::env::var("GRID_LOGIN_URL").ok())
            .filter(|value| !value.is_empty()),
        login_timeout: Duration::from_secs(cli.login_timeout_seconds),
    })
}

fn required(
    value: Option<String>,
    env: &str,
    message: &'static str,
) -> Result<String, ProgramError> {
    value
        .or_else(|| std::env::var(env).ok())
        .filter(|value| !value.is_empty())
        .ok_or(ProgramError::Usage(message))
}

async fn run_live(mut config: LiveConfig) -> Result<(), ProgramError> {
    let client = GridClient::new().map_err(|_| ProgramError::Client("construct GridClient"))?;
    let network = client.network();
    let mut login = network
        .default_login_params(
            std::mem::take(&mut config.first_name),
            std::mem::take(&mut config.last_name),
            std::mem::take(&mut config.password),
            "IRCGateway".into(),
            env!("CARGO_PKG_VERSION").into(),
        )
        .map_err(|_| ProgramError::Client("build login parameters"))?;
    if let Some(uri) = config.login_uri.take() {
        login.uri = uri;
    }

    let grid = Arc::new(LiveGrid::new(client, network.clone()));
    let own_grid_id = grid.with_agent(|agent| agent.agent_id());
    let dropped = Arc::new(AtomicUsize::new(0));
    let (event_tx, event_rx) = mpsc::channel(EVENT_QUEUE_CAPACITY);
    let (irc_tx, irc_rx) = mpsc::channel(OUTBOUND_QUEUE_CAPACITY);
    grid.install(&event_tx, &dropped);
    let cancellation = CancellationTokenSource::new();
    let irc_worker = tokio::spawn(irc_loop(IrcRuntime {
        host: config.irc_host.clone(),
        port: config.irc_port,
        nick: config.bridge.nickname.clone(),
        real_name: config.real_name.clone(),
        commands: irc_rx,
        events: event_tx.clone(),
        dropped: Arc::clone(&dropped),
        cancellation: cancellation.token(),
    }));
    let bridge_worker = tokio::spawn(bridge_loop(
        Bridge::new(config.bridge.clone(), config.master, own_grid_id),
        LiveTransport {
            grid: Arc::clone(&grid),
            irc: irc_tx.clone(),
        },
        event_rx,
        Arc::new(ConsoleLogger),
        cancellation.token(),
    ));

    let result = match await_grid_login(&network, login, config.login_timeout).await {
        Ok(Some(true)) => {
            try_event(
                &event_tx,
                BridgeEvent::OwnGridId(grid.with_agent(|agent| agent.agent_id())),
                &dropped,
            );
            tokio::signal::ctrl_c()
                .await
                .map_err(|_| ProgramError::Signal)
        }
        Ok(Some(false)) => Err(ProgramError::LoginFailed),
        Ok(None) => Ok(()),
        Err(error) => Err(error),
    };
    finish_live(
        grid,
        event_tx,
        irc_tx,
        cancellation,
        bridge_worker,
        irc_worker,
        dropped,
    )
    .await;
    result
}

async fn await_grid_login(
    network: &NetworkManager,
    login: LoginParams,
    timeout: Duration,
) -> Result<Option<bool>, ProgramError> {
    let cancellation = CancellationTokenSource::new();
    tokio::select! {
        result = network.login_with_login_params_cancellation_token(login, Some(cancellation.token())) => {
            result.map(Some).map_err(|_| ProgramError::LoginFailed)
        },
        () = tokio::time::sleep(timeout) => {
            cancellation.cancel();
            let _ = network.abort_login();
            Err(ProgramError::LoginTimedOut)
        },
        signal = tokio::signal::ctrl_c() => {
            cancellation.cancel();
            let _ = network.abort_login();
            signal.map_err(|_| ProgramError::Signal)?;
            Ok(None)
        }
    }
}

async fn finish_live(
    grid: Arc<LiveGrid>,
    event_tx: mpsc::Sender<BridgeEvent>,
    irc_tx: mpsc::Sender<IrcCommand>,
    cancellation: CancellationTokenSource,
    bridge: tokio::task::JoinHandle<Bridge>,
    irc: tokio::task::JoinHandle<()>,
    dropped: Arc<AtomicUsize>,
) {
    cancellation.cancel();
    drop(event_tx);
    drop(irc_tx);
    let finished = bridge.await.ok();
    let _ = irc.await;
    grid.shutdown();
    let total_dropped =
        dropped.load(Ordering::Acquire) + finished.map_or(0, |bridge| bridge.dropped);
    if total_dropped > 0 {
        eprintln!("irc-gateway: dropped {total_dropped} messages because bounded queues were full");
    }
}

async fn bridge_loop<T: BridgeTransport + Send + 'static>(
    mut bridge: Bridge,
    mut transport: T,
    mut events: mpsc::Receiver<BridgeEvent>,
    logger: Arc<dyn BridgeLogger>,
    cancellation: CancellationToken,
) -> Bridge {
    let start = Instant::now();
    let mut interval = tokio::time::interval(Duration::from_millis(TICK_MS));
    loop {
        tokio::select! {
            () = cancellation.cancelled() => break,
            _ = interval.tick() => bridge.tick(elapsed_ms(start), &mut transport, logger.as_ref()),
            event = events.recv() => match event {
                Some(event) => bridge.handle(event, elapsed_ms(start), &mut transport, logger.as_ref()),
                None => break,
            }
        }
    }
    events.close();
    bridge
}

async fn irc_loop(mut runtime: IrcRuntime) {
    let mut backoff = Duration::from_secs(1);
    loop {
        let connection = tokio::select! {
            () = runtime.cancellation.cancelled() => break,
            result = TcpStream::connect((runtime.host.as_str(), runtime.port)) => result,
        };
        match connection {
            Ok(stream) => {
                backoff = Duration::from_secs(1);
                if run_irc_connection(
                    stream,
                    &runtime.nick,
                    &runtime.real_name,
                    &mut runtime.commands,
                    &runtime.events,
                    &runtime.dropped,
                    runtime.cancellation.clone(),
                )
                .await
                .is_err()
                {
                    try_event(
                        &runtime.events,
                        BridgeEvent::IrcDisconnected,
                        &runtime.dropped,
                    );
                }
            }
            Err(_) => try_event(
                &runtime.events,
                BridgeEvent::IrcDisconnected,
                &runtime.dropped,
            ),
        }
        tokio::select! {
            () = runtime.cancellation.cancelled() => break,
            () = tokio::time::sleep(backoff) => {}
        }
        backoff = (backoff * 2).min(Duration::from_secs(30));
    }
}

async fn run_irc_connection(
    stream: TcpStream,
    nick: &str,
    real_name: &str,
    commands: &mut mpsc::Receiver<IrcCommand>,
    events: &mpsc::Sender<BridgeEvent>,
    dropped: &AtomicUsize,
    cancellation: CancellationToken,
) -> io::Result<()> {
    let (reader, mut writer) = stream.into_split();
    write_irc(&mut writer, &format!("USER {nick} 0 * :{real_name}")).await?;
    write_irc(&mut writer, &format!("NICK {nick}")).await?;
    let mut reader = AsyncBufReader::new(reader);
    loop {
        tokio::select! {
            () = cancellation.cancelled() => return Ok(()),
            command = commands.recv() => match command {
                Some(IrcCommand::Join(channel)) => write_irc(&mut writer, &format!("JOIN {}", sanitize_irc_atom(&channel))).await?,
                Some(IrcCommand::Message(target, message)) => {
                    let prefix = format!("PRIVMSG {} :", sanitize_irc_atom(&target));
                    let message = truncate_utf8(&clean_message(&message), IRC_LINE_BYTES - 2 - prefix.len());
                    write_irc(&mut writer, &format!("{prefix}{message}")).await?;
                }
                None => return Ok(()),
            },
            line = read_irc_line(&mut reader) => {
                let Some(line) = line? else { return Err(io::Error::new(io::ErrorKind::UnexpectedEof, "IRC disconnected")); };
                if let Some(message) = parse_irc_line(&line) {
                    match message.command.as_str() {
                        "PING" => {
                            let payload = message.trailing.or_else(|| message.params.first().cloned()).unwrap_or_default();
                            write_irc(&mut writer, &format!("PONG :{}", clean_message(&payload))).await?;
                        }
                        "001" => try_event(events, BridgeEvent::IrcConnected, dropped),
                        "PRIVMSG" => {
                            if let (Some(prefix), Some(target), Some(text)) = (message.prefix, message.params.first(), message.trailing) {
                                let nick = prefix.split('!').next().unwrap_or(&prefix).to_owned();
                                try_event(events, BridgeEvent::IrcMessage { target: target.clone(), nick, message: text }, dropped);
                            }
                        }
                        _ => {}
                    }
                }
            }
        }
    }
}

async fn read_irc_line<R: AsyncBufRead + Unpin>(reader: &mut R) -> io::Result<Option<String>> {
    let mut bytes = Vec::with_capacity(IRC_LINE_BYTES);
    loop {
        let available = reader.fill_buf().await?;
        if available.is_empty() {
            return if bytes.is_empty() {
                Ok(None)
            } else {
                Ok(Some(String::from_utf8_lossy(&bytes).into_owned()))
            };
        }
        let newline = available.iter().position(|byte| *byte == b'\n');
        let consumed = newline.map_or(available.len(), |index| index + 1);
        if bytes.len().saturating_add(consumed) > MAX_IRC_INPUT_BYTES {
            return Err(io::Error::new(
                io::ErrorKind::InvalidData,
                "oversized IRC line",
            ));
        }
        bytes.extend_from_slice(&available[..consumed]);
        reader.consume(consumed);
        if newline.is_some() {
            return Ok(Some(String::from_utf8_lossy(&bytes).into_owned()));
        }
    }
}

async fn write_irc(writer: &mut tokio::net::tcp::OwnedWriteHalf, line: &str) -> io::Result<()> {
    let line = truncate_utf8(&clean_message(line), IRC_LINE_BYTES - 2);
    writer.write_all(line.as_bytes()).await?;
    writer.write_all(b"\r\n").await
}

struct IrcMessage {
    prefix: Option<String>,
    command: String,
    params: Vec<String>,
    trailing: Option<String>,
}

fn parse_irc_line(line: &str) -> Option<IrcMessage> {
    let line = line.trim_matches(['\r', '\n']);
    if line.is_empty() || line.as_bytes().contains(&0) {
        return None;
    }
    let line = if let Some(tagged) = line.strip_prefix('@') {
        tagged.split_once(' ')?.1.trim_start()
    } else {
        line
    };
    let (prefix, rest) = if let Some(rest) = line.strip_prefix(':') {
        let (prefix, rest) = rest.split_once(' ')?;
        (Some(prefix.to_owned()), rest.trim_start())
    } else {
        (None, line)
    };
    let (middle, trailing) = if let Some((middle, trailing)) = rest.split_once(" :") {
        (middle, Some(trailing.to_owned()))
    } else {
        (rest, None)
    };
    let mut words = middle.split_whitespace();
    let command = words.next()?.to_ascii_uppercase();
    Some(IrcMessage {
        prefix,
        command,
        params: words.map(str::to_owned).collect(),
        trailing,
    })
}

fn run_fake(cli: &Cli, path: &Path) -> Result<(), ProgramError> {
    validate_channel(&cli.fake_channel)?;
    validate_nick(&cli.nickname)?;
    let master_text = cli.master_uuid.as_deref().unwrap_or(&cli.fake_master_uuid);
    let master = parse_uuid(master_text, 0, "master UUID is invalid")?;
    let own = UUID::new_with_string("aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee".into())
        .map_err(|_| ProgramError::Client("construct fake agent UUID"))?;
    let config = BridgeConfig {
        channel: cli
            .channel
            .clone()
            .unwrap_or_else(|| cli.fake_channel.clone()),
        nickname: cli.nickname.clone(),
        messages_per_second: cli.messages_per_second,
        burst: cli.burst,
    };
    validate_channel(&config.channel)?;
    let events = read_script(path)?;
    let mut bridge = Bridge::new(config, master, own);
    let mut transport = ScriptTransport::default();
    let logger = ScriptLogger::default();
    let mut now_ms = 0;
    let mut shutdown = false;
    for event in events {
        match event {
            ScriptEvent::Bridge(event) => bridge.handle(event, now_ms, &mut transport, &logger),
            ScriptEvent::Advance(milliseconds) => {
                now_ms = now_ms.saturating_add(milliseconds);
                bridge.tick(now_ms, &mut transport, &logger);
            }
            ScriptEvent::Shutdown => {
                shutdown = true;
                break;
            }
        }
    }
    bridge.tick(now_ms.saturating_add(60_000), &mut transport, &logger);
    let stdout = io::stdout();
    let mut output = stdout.lock();
    for line in logger.lines.into_inner().unwrap_or_default() {
        writeln!(output, "{line}").map_err(|source| io_error("writing standard output", source))?;
    }
    for call in transport.calls {
        writeln!(output, "{}", redact_text(&call))
            .map_err(|source| io_error("writing standard output", source))?;
    }
    writeln!(output, "STATE irc-connected={} queued={} dropped={} active-transports=0 active-tasks=0 shutdown={shutdown}", bridge.irc_connected, bridge.pending.len(), bridge.dropped)
        .map_err(|source| io_error("writing standard output", source))?;
    Ok(())
}

#[derive(Default)]
struct ScriptLogger {
    lines: Mutex<Vec<String>>,
}
impl BridgeLogger for ScriptLogger {
    fn line(&self, line: String) {
        lock(&self.lines).push(redact_text(&line));
    }
}

enum ScriptEvent {
    Bridge(BridgeEvent),
    Advance(u64),
    Shutdown,
}

fn read_script(path: &Path) -> Result<Vec<ScriptEvent>, ProgramError> {
    let file = File::open(path)
        .map_err(|source| io_error(format!("opening {}", path.display()), source))?;
    if file
        .metadata()
        .map_err(|source| io_error("reading script metadata", source))?
        .len()
        > MAX_SCRIPT_BYTES
    {
        return Err(ProgramError::InvalidScript {
            line: 0,
            reason: "script exceeds 1 MiB",
        });
    }
    let mut bounded = file.take(MAX_SCRIPT_BYTES + 1);
    let mut bytes = Vec::new();
    bounded
        .read_to_end(&mut bytes)
        .map_err(|source| io_error("reading bridge script", source))?;
    if bytes.len() as u64 > MAX_SCRIPT_BYTES {
        return Err(ProgramError::InvalidScript {
            line: 0,
            reason: "script exceeds 1 MiB",
        });
    }
    let reader = BufReader::new(bytes.as_slice());
    let mut events = Vec::new();
    for (index, line) in reader.lines().enumerate() {
        let line_number = index + 1;
        let line = line.map_err(|source| io_error("decoding bridge script as UTF-8", source))?;
        if line.trim().is_empty() || line.trim_start().starts_with('#') {
            continue;
        }
        if events.len() == MAX_SCRIPT_EVENTS {
            return Err(ProgramError::InvalidScript {
                line: line_number,
                reason: "script has more than 4,096 events",
            });
        }
        events.push(parse_script_line(&line, line_number)?);
    }
    Ok(events)
}

fn parse_script_line(line: &str, number: usize) -> Result<ScriptEvent, ProgramError> {
    let fields: Vec<_> = line.split('\t').collect();
    let invalid = || ProgramError::InvalidScript {
        line: number,
        reason: "expected irc-connect, irc-disconnect, irc<TAB>target<TAB>nick<TAB>message, grid-chat<TAB>uuid<TAB>name<TAB>normal|other<TAB>full|other<TAB>message, grid-login<TAB>message, teleport<TAB>source-uuid<TAB>session-uuid, advance<TAB>milliseconds, or shutdown",
    };
    match fields.as_slice() {
        ["irc-connect"] => Ok(ScriptEvent::Bridge(BridgeEvent::IrcConnected)),
        ["irc-disconnect"] => Ok(ScriptEvent::Bridge(BridgeEvent::IrcDisconnected)),
        ["irc", target, nick, message]
            if target.len() <= MAX_NAME_BYTES
                && nick.len() <= MAX_NAME_BYTES
                && message.len() <= MAX_MESSAGE_BYTES =>
        {
            Ok(ScriptEvent::Bridge(BridgeEvent::IrcMessage {
                target: (*target).into(),
                nick: (*nick).into(),
                message: (*message).into(),
            }))
        }
        ["grid-chat", uuid, name, kind, audible, message]
            if name.len() <= MAX_NAME_BYTES && message.len() <= MAX_MESSAGE_BYTES =>
        {
            Ok(ScriptEvent::Bridge(BridgeEvent::GridChat {
                source_id: parse_uuid(uuid, number, "grid source UUID is invalid")?,
                name: (*name).into(),
                message: (*message).into(),
                normal: *kind == "normal",
                fully_audible: *audible == "full",
            }))
        }
        ["grid-login", message] if message.len() <= MAX_MESSAGE_BYTES => Ok(ScriptEvent::Bridge(
            BridgeEvent::GridLogin((*message).into()),
        )),
        ["teleport", source, session] => Ok(ScriptEvent::Bridge(BridgeEvent::Teleport {
            source_id: parse_uuid(source, number, "teleport source UUID is invalid")?,
            session_id: parse_uuid(session, number, "teleport session UUID is invalid")?,
        })),
        ["advance", milliseconds] => Ok(ScriptEvent::Advance(
            milliseconds.parse().map_err(|_| invalid())?,
        )),
        ["shutdown"] => Ok(ScriptEvent::Shutdown),
        _ => Err(invalid()),
    }
}

fn validate_channel(channel: &str) -> Result<(), ProgramError> {
    if channel.starts_with('#')
        && channel.len() > 1
        && channel.len() <= 200
        && !channel
            .chars()
            .any(|ch| ch.is_control() || ch == ' ' || ch == ',')
    {
        Ok(())
    } else {
        Err(ProgramError::Usage(
            "IRC channel must begin with '#' and contain no spaces, commas, or controls",
        ))
    }
}

fn validate_nick(nick: &str) -> Result<(), ProgramError> {
    if !nick.is_empty() && nick.len() <= 32 && nick.chars().all(is_nick_char) {
        Ok(())
    } else {
        Err(ProgramError::Usage(
            "IRC nickname must be 1..32 portable IRC nickname characters",
        ))
    }
}

fn is_nick_char(ch: char) -> bool {
    ch.is_ascii_alphanumeric() || "-_[]{}\\`^|".contains(ch)
}
fn irc_eq(left: &str, right: &str) -> bool {
    left.chars().map(irc_fold).eq(right.chars().map(irc_fold))
}
fn irc_fold(ch: char) -> char {
    match ch {
        'A'..='Z' => ch.to_ascii_lowercase(),
        '[' | '{' => '{',
        ']' | '}' => '}',
        '\\' | '|' => '|',
        '^' | '~' => '~',
        _ => ch,
    }
}

fn map_name(name: &str) -> String {
    let mapped: String = name
        .chars()
        .filter(|ch| !ch.is_control())
        .map(|ch| if ch == '<' || ch == '>' { '_' } else { ch })
        .take(64)
        .collect();
    let mapped = mapped.split_whitespace().collect::<Vec<_>>().join(" ");
    if mapped.is_empty() {
        "unknown".into()
    } else {
        mapped
    }
}

fn valid_message(message: &str) -> bool {
    !message.trim().is_empty()
        && message.len() <= MAX_MESSAGE_BYTES
        && !message.as_bytes().contains(&0)
}
fn clean_message(message: &str) -> String {
    message
        .chars()
        .map(|ch| {
            if ch == '\r' || ch == '\n' || ch == '\0' {
                ' '
            } else {
                ch
            }
        })
        .collect::<String>()
        .trim()
        .to_owned()
}
fn sanitize_irc_atom(value: &str) -> String {
    value
        .chars()
        .filter(|ch| !ch.is_control() && *ch != ' ' && *ch != ',' && *ch != ':')
        .collect()
}

fn truncate_utf8(value: &str, max: usize) -> String {
    if value.len() <= max {
        return value.into();
    }
    let mut end = max;
    while !value.is_char_boundary(end) {
        end -= 1;
    }
    value[..end].into()
}

fn redact_text(value: &str) -> String {
    let lower = value.to_ascii_lowercase();
    if [
        "password",
        "passwd",
        "authorization",
        "capability",
        "token=",
        "sasl",
        "oauth",
    ]
    .iter()
    .any(|marker| lower.contains(marker))
    {
        return "<redacted>".into();
    }
    value
        .split_whitespace()
        .map(|word| {
            if word.contains("://") {
                "<redacted-url>"
            } else {
                word
            }
        })
        .collect::<Vec<_>>()
        .join(" ")
}

fn elapsed_ms(start: Instant) -> u64 {
    u64::try_from(start.elapsed().as_millis()).unwrap_or(u64::MAX)
}
fn try_event(sender: &mpsc::Sender<BridgeEvent>, event: BridgeEvent, dropped: &AtomicUsize) {
    if sender.try_send(event).is_err() {
        dropped.fetch_add(1, Ordering::Relaxed);
    }
}
fn parse_uuid(value: &str, line: usize, reason: &'static str) -> Result<UUID, ProgramError> {
    UUID::new_with_string(value.into()).map_err(|_| ProgramError::InvalidScript { line, reason })
}
fn io_error(action: impl Into<String>, source: io::Error) -> ProgramError {
    ProgramError::Io {
        action: action.into(),
        source,
    }
}
fn lock<T>(mutex: &Mutex<T>) -> MutexGuard<'_, T> {
    mutex
        .lock()
        .unwrap_or_else(std::sync::PoisonError::into_inner)
}

#[cfg(test)]
mod tests {
    use super::*;

    struct DropProbe(Arc<AtomicBool>);

    impl Drop for DropProbe {
        fn drop(&mut self) {
            self.0.store(false, Ordering::Release);
        }
    }

    impl BridgeTransport for DropProbe {
        fn join_irc(&mut self, _channel: &str) -> Result<(), &'static str> {
            Ok(())
        }
        fn send_irc(&mut self, _channel: &str, _message: &str) -> Result<(), &'static str> {
            Ok(())
        }
        fn send_grid(&mut self, _message: &str) -> Result<(), &'static str> {
            Ok(())
        }
        fn accept_teleport(&mut self, _source: UUID, _session: UUID) -> Result<(), &'static str> {
            Ok(())
        }
    }

    #[test]
    fn parses_partial_protocol_boundaries() {
        let ping = parse_irc_line("PING :server.example").unwrap();
        assert_eq!(ping.command, "PING");
        assert_eq!(ping.trailing.as_deref(), Some("server.example"));
        let message = parse_irc_line(":Alice!user@host PRIVMSG #room :hello UTF-8 ☃").unwrap();
        assert_eq!(message.prefix.as_deref(), Some("Alice!user@host"));
        assert_eq!(message.params, ["#room"]);
        assert_eq!(message.trailing.as_deref(), Some("hello UTF-8 ☃"));
        let tagged = parse_irc_line("@time=now :Bob!u@h PRIVMSG #room :tagged").unwrap();
        assert_eq!(tagged.command, "PRIVMSG");
        assert_eq!(tagged.trailing.as_deref(), Some("tagged"));
        assert!(parse_irc_line(":broken").is_none());
    }

    #[tokio::test]
    async fn line_reader_handles_fragments_and_rejects_unbounded_input() {
        let (mut writer, reader) = tokio::io::duplex(MAX_IRC_INPUT_BYTES * 2);
        let sender = tokio::spawn(async move {
            writer.write_all(b":nick PRIV").await.unwrap();
            writer.write_all(b"MSG #room :hello\r\n").await.unwrap();
        });
        let mut reader = AsyncBufReader::new(reader);
        assert_eq!(
            read_irc_line(&mut reader).await.unwrap().as_deref(),
            Some(":nick PRIVMSG #room :hello\r\n")
        );
        sender.await.unwrap();

        let bytes = vec![b'x'; MAX_IRC_INPUT_BYTES + 1];
        let mut reader = AsyncBufReader::new(bytes.as_slice());
        assert_eq!(
            read_irc_line(&mut reader).await.unwrap_err().kind(),
            io::ErrorKind::InvalidData
        );
    }

    #[test]
    fn utf8_truncation_never_splits_a_scalar() {
        assert_eq!(truncate_utf8("ab☃cd", 4), "ab");
        assert_eq!(truncate_utf8("ab☃cd", 5), "ab☃");
    }

    #[test]
    fn duplicate_and_loop_detection_are_directional() {
        let master = UUID::new_with_string("11111111-2222-3333-4444-555555555555".into()).unwrap();
        let own = UUID::new_with_string("aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee".into()).unwrap();
        let other = UUID::new_with_string("bbbbbbbb-cccc-dddd-eeee-ffffffffffff".into()).unwrap();
        let mut bridge = Bridge::new(
            BridgeConfig {
                channel: "#room".into(),
                nickname: "SLGateway".into(),
                messages_per_second: 10,
                burst: 10,
            },
            master,
            own,
        );
        let mut transport = ScriptTransport::default();
        let logger = ScriptLogger::default();
        bridge.handle(BridgeEvent::IrcConnected, 0, &mut transport, &logger);
        let event = BridgeEvent::GridChat {
            source_id: other,
            name: "Alice".into(),
            message: "hello".into(),
            normal: true,
            fully_audible: true,
        };
        bridge.handle(event.clone(), 1, &mut transport, &logger);
        bridge.handle(event, 2, &mut transport, &logger);
        bridge.handle(
            BridgeEvent::IrcMessage {
                target: "#room".into(),
                nick: "Relay".into(),
                message: "<Alice> hello".into(),
            },
            3,
            &mut transport,
            &logger,
        );
        assert_eq!(
            transport
                .calls
                .iter()
                .filter(|call| call.contains("irc-privmsg"))
                .count(),
            1
        );
        assert!(
            !transport
                .calls
                .iter()
                .any(|call| call.contains("grid-chat"))
        );
    }

    #[test]
    fn rate_limit_queues_and_drains() {
        let master = UUID::new_with_string("11111111-2222-3333-4444-555555555555".into()).unwrap();
        let own = UUID::new_with_string("aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee".into()).unwrap();
        let mut bridge = Bridge::new(
            BridgeConfig {
                channel: "#room".into(),
                nickname: "SLGateway".into(),
                messages_per_second: 1,
                burst: 1,
            },
            master,
            own,
        );
        let mut transport = ScriptTransport::default();
        let logger = ScriptLogger::default();
        bridge.handle(BridgeEvent::IrcConnected, 0, &mut transport, &logger);
        bridge.handle(
            BridgeEvent::GridLogin("one".into()),
            0,
            &mut transport,
            &logger,
        );
        bridge.handle(
            BridgeEvent::GridLogin("two".into()),
            0,
            &mut transport,
            &logger,
        );
        assert_eq!(bridge.pending.len(), 1);
        bridge.tick(1_000, &mut transport, &logger);
        assert!(bridge.pending.is_empty());
    }

    #[test]
    fn bounded_bridge_queue_drops_oldest_messages() {
        let master = UUID::new_with_string("11111111-2222-3333-4444-555555555555".into()).unwrap();
        let own = UUID::new_with_string("aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee".into()).unwrap();
        let mut bridge = Bridge::new(
            BridgeConfig {
                channel: "#room".into(),
                nickname: "SLGateway".into(),
                messages_per_second: 1,
                burst: 1,
            },
            master,
            own,
        );
        for index in 0..=BRIDGE_QUEUE_CAPACITY {
            bridge.enqueue(Direction::ToIrc, format!("message-{index}"));
        }
        assert_eq!(bridge.pending.len(), BRIDGE_QUEUE_CAPACITY);
        assert_eq!(bridge.dropped, 1);
        assert_eq!(bridge.pending.front().unwrap().message, "message-1");
    }

    #[test]
    fn irc_channel_comparison_uses_rfc1459_case_mapping() {
        assert!(irc_eq("#Rust[Bridge]", "#rUST{bRIDGE}"));
        assert!(irc_eq("Nick\\Name", "nICK|nAME"));
        assert!(!irc_eq("#one", "#two"));
    }

    #[tokio::test]
    async fn cancellation_joins_workers_and_drops_transport() {
        let master = UUID::new_with_string("11111111-2222-3333-4444-555555555555".into()).unwrap();
        let own = UUID::new_with_string("aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee".into()).unwrap();
        let config = BridgeConfig {
            channel: "#room".into(),
            nickname: "SLGateway".into(),
            messages_per_second: 1,
            burst: 1,
        };
        let alive = Arc::new(AtomicBool::new(true));
        let bridge_cancel = CancellationTokenSource::new();
        let (event_tx, event_rx) = mpsc::channel(1);
        let bridge = tokio::spawn(bridge_loop(
            Bridge::new(config, master, own),
            DropProbe(Arc::clone(&alive)),
            event_rx,
            Arc::new(ScriptLogger::default()),
            bridge_cancel.token(),
        ));
        bridge_cancel.cancel();
        drop(event_tx);
        tokio::time::timeout(Duration::from_secs(1), bridge)
            .await
            .expect("bridge stopped before timeout")
            .expect("bridge worker did not panic");
        assert!(!alive.load(Ordering::Acquire));

        let irc_cancel = CancellationTokenSource::new();
        let (command_tx, command_rx) = mpsc::channel(1);
        let (events, _event_rx) = mpsc::channel(1);
        let irc = tokio::spawn(irc_loop(IrcRuntime {
            host: "127.0.0.1".into(),
            port: 0,
            nick: "SLGateway".into(),
            real_name: "test".into(),
            commands: command_rx,
            events,
            dropped: Arc::new(AtomicUsize::new(0)),
            cancellation: irc_cancel.token(),
        }));
        irc_cancel.cancel();
        drop(command_tx);
        tokio::time::timeout(Duration::from_secs(1), irc)
            .await
            .expect("IRC worker stopped before timeout")
            .expect("IRC worker did not panic");
    }
}