foukoapi 0.1.2-alpha.2

//! The [`Bot`] builder and its runtime.

use crate::{
    accounts::Accounts,
    adapters,
    command::{Command, Handler},
    error::{Error, Result},
    platform::{Platform, PlatformConfig},
    ratelimit::{RateLimit, RateLimiter},
    Ctx,
};
use futures::future::{self, BoxFuture};
use std::{collections::HashMap, future::Future, sync::Arc};

/// The main entry point.
///
/// Build one with [`Bot::new`], add platforms and commands with the
/// chainable methods, then call [`Bot::run`].
///
/// ```no_run
/// use foukoapi::{Bot, Platform};
///
/// # async fn run() -> foukoapi::Result<()> {
/// Bot::new()
///     .add_platform(Platform::telegram("123:abc"))
///     .command("/help", |ctx| async move {
///         ctx.reply("hi").await
///     })
///     .run()
///     .await
/// # }
/// ```
#[must_use = "a Bot does nothing until you call .run().await on it"]
pub struct Bot {
    platforms: Vec<Platform>,
    commands: HashMap<String, CommandSlot>,
    /// Plain-text triggers (no leading `/`). Matched case-insensitively in
    /// registration order.
    text_commands: Vec<TextSlot>,
    fallback: Option<Handler>,
    /// Runs for every incoming message (after command dispatch), useful for
    /// XP counters and logging. It never answers the user - just observes.
    on_message: Vec<Handler>,
    /// Handle to the account helper. When set, built-in helpers like
    /// [`Bot::with_default_lang_command`] and the i18n-aware
    /// [`Bot::with_default_help`] can read/write per-user language.
    accounts: Option<Accounts>,
    /// Per-user rate limiter. `None` means no limiting. Defaults to a
    /// relaxed policy so a fresh bot is spam-resistant without any setup;
    /// override with [`Bot::rate_limit`] or disable with
    /// [`Bot::no_rate_limit`].
    rate_limiter: Option<Arc<RateLimiter>>,
    /// Optional hook run when a user trips the rate limit, so a bot can
    /// tell them to slow down instead of silently dropping the message.
    on_rate_limited: Option<Handler>,
    /// Drop updates older than this on startup, so a bot that was offline
    /// doesn't reply to a backlog of stale commands all at once. `None`
    /// keeps every update. Only adapters that expose an update timestamp
    /// (Telegram) honour it.
    max_update_age: Option<std::time::Duration>,
    /// Optional flood watchdog: counts every incoming update before the
    /// per-user rate limit and fires a handler when the total for the
    /// current minute crosses a threshold. Set with [`Bot::on_flood`].
    on_flood: Option<FloodHook>,
    /// Optional outbound handle. When set, adapters register their sender
    /// into it on startup so background tasks can push messages.
    notifier: Option<crate::notifier::Notifier>,
    /// Optional Mini App menu button: `(label, url)`. When set, the
    /// Telegram adapter publishes it via `setChatMenuButton` on startup,
    /// so private chats show an app button next to the message box.
    menu_web_app: Option<(String, String)>,
    /// Optional presence (activity + online status). Applied by the
    /// Discord adapter when the gateway is ready; platforms without a
    /// presence concept ignore it.
    presence: Option<crate::platform::Presence>,
}

#[derive(Clone)]
struct TextSlot {
    pattern: String,
    matcher: TextMatch,
    handler: Handler,
}

/// How a text-trigger matches an incoming message.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum TextMatch {
    /// The whole message (trimmed) equals the pattern, case-insensitive.
    Exact,
    /// The message starts with the pattern (trimmed, case-insensitive).
    Prefix,
    /// The pattern appears anywhere in the message, case-insensitive.
    Contains,
}

#[derive(Clone)]
struct CommandSlot {
    handler: Handler,
    /// `None` means "runs on every platform".
    platforms: Option<Vec<crate::PlatformKind>>,
    /// Default-language description. Shown by the auto-generated `/help`
    /// when nothing else matches the user's language.
    description: Option<String>,
    /// Per-language descriptions keyed by lang code (e.g. `"en"`, `"ru"`).
    /// Populated by [`Bot::command_described_i18n`].
    descriptions_i18n: HashMap<String, String>,
    /// Optional group heading used by the auto-generated `/help` to sort
    /// commands into sections. `None` lands the command in a default
    /// bucket. Set with [`Bot::category`].
    category: Option<String>,
    /// When `true`, the Discord adapter adds a native USER option to this
    /// slash command so the client offers a member picker. The picked
    /// user's id is prepended to the command's args. Set with
    /// [`Bot::user_option`].
    takes_user: bool,
}

impl Bot {
    /// Start a fresh, empty bot.
    pub fn new() -> Self {
        Self {
            platforms: Vec::new(),
            commands: HashMap::new(),
            text_commands: Vec::new(),
            fallback: None,
            on_message: Vec::new(),
            accounts: None,
            rate_limiter: Some(Arc::new(RateLimiter::new(RateLimit::relaxed()))),
            on_rate_limited: None,
            max_update_age: Some(std::time::Duration::from_secs(60)),
            on_flood: None,
            notifier: None,
            menu_web_app: None,
            presence: None,
        }
    }

    /// Attach a [`Notifier`](crate::Notifier) so background tasks can push
    /// messages into chats. Adapters register their delivery function into
    /// it as they connect. Keep a clone of the notifier before calling
    /// this to use it later.
    pub fn with_notifier(mut self, notifier: crate::notifier::Notifier) -> Self {
        self.notifier = Some(notifier);
        self
    }

    /// Show a Mini App button in Telegram private chats (the button next
    /// to the message box, like BotFather's "Open"). Published via
    /// `setChatMenuButton` when the Telegram adapter starts. Other
    /// platforms ignore it.
    ///
    /// For the app to also appear on the bot's profile, additionally set
    /// the Main Mini App URL in BotFather (/mybots -> Bot Settings ->
    /// Main Mini App) - Telegram offers no API for that part.
    pub fn menu_web_app(mut self, label: impl Into<String>, url: impl Into<String>) -> Self {
        self.menu_web_app = Some((label.into(), url.into()));
        self
    }

    /// What the bot appears to be doing - "Playing X", "Streaming Y with
    /// a link", plus the online dot. Discord shows it in the member list
    /// and on the bot's profile; platforms without presence (Telegram)
    /// ignore it. Applied when the gateway connects, and re-applied on
    /// every reconnect.
    ///
    /// ```no_run
    /// use foukoapi::{Bot, Presence};
    ///
    /// Bot::new().presence(Presence::streaming("bot.fouko.xyz", "https://bot.fouko.xyz"));
    /// ```
    pub fn presence(mut self, presence: crate::platform::Presence) -> Self {
        self.presence = Some(presence);
        self
    }

    /// Replace the per-user rate-limit policy.
    ///
    /// By default a bot throttles each user to a relaxed 5 actions / 3
    /// seconds. Pass your own [`RateLimit`] to make it looser or tighter.
    pub fn rate_limit(mut self, policy: RateLimit) -> Self {
        self.rate_limiter = Some(Arc::new(RateLimiter::new(policy)));
        self
    }

    /// Turn per-user rate limiting off entirely. Not recommended for a
    /// public bot, but handy for tests or trusted single-user setups.
    pub fn no_rate_limit(mut self) -> Self {
        self.rate_limiter = None;
        self
    }

    /// Run `handler` when a user trips the rate limit, e.g. to reply
    /// "you're going too fast". Without one, throttled updates are simply
    /// dropped. The handler sees the same [`Ctx`] the update would have
    /// reached, so it can answer in the right chat and language.
    pub fn on_rate_limited<F, Fut>(mut self, handler: F) -> Self
    where
        F: Fn(Ctx) -> Fut + Send + Sync + 'static,
        Fut: Future<Output = Result<()>> + Send + 'static,
    {
        self.on_rate_limited = Some(Handler::new(handler));
        self
    }

    /// Install a watchdog over the *total* incoming update flow, across
    /// all users and platforms. Every update is counted before the
    /// per-user rate limit; when more than `per_minute` land inside one
    /// 60-second window, `handler` fires with the current count. It fires
    /// at most once per `cooldown`, so an ongoing flood pages you once,
    /// not once per message. Use it to detect a spam wave or a DDoS-style
    /// burst and alert an operator.
    ///
    /// ```no_run
    /// use foukoapi::{Bot, Notifier, PlatformKind, Reply};
    /// use std::time::Duration;
    ///
    /// let notifier = Notifier::new();
    /// let alerts = notifier.clone();
    /// Bot::new()
    ///     .with_notifier(notifier)
    ///     .on_flood(600, Duration::from_secs(300), move |count| {
    ///         let alerts = alerts.clone();
    ///         async move {
    ///             let msg = format!("flood: {count} updates in the last minute");
    ///             let _ = alerts
    ///                 .send(PlatformKind::Telegram, "123456", Reply::text(msg))
    ///                 .await;
    ///         }
    ///     });
    /// ```
    pub fn on_flood<F, Fut>(
        mut self,
        per_minute: u32,
        cooldown: std::time::Duration,
        handler: F,
    ) -> Self
    where
        F: Fn(u64) -> Fut + Send + Sync + 'static,
        Fut: Future<Output = ()> + Send + 'static,
    {
        self.on_flood = Some(FloodHook {
            window: FloodWindow::new(per_minute, cooldown),
            handler: Arc::new(move |count| Box::pin(handler(count))),
        });
        self
    }

    /// Ignore updates older than `age` when they arrive. This is the
    /// "don't spew a backlog after downtime" guard: if the bot was offline
    /// and a platform delivers a pile of queued messages, anything older
    /// than `age` is skipped. Pass a very large duration (or build your
    /// own dispatch) to keep everything.
    pub fn max_update_age(mut self, age: std::time::Duration) -> Self {
        self.max_update_age = Some(age);
        self
    }

    /// Process every update regardless of age (opposite of
    /// [`Bot::max_update_age`]).
    pub fn process_all_updates(mut self) -> Self {
        self.max_update_age = None;
        self
    }

    /// Hand the bot a ready-made [`Accounts`] so that built-in helpers
    /// (like [`Bot::with_default_lang_command`] and i18n in
    /// [`Bot::with_default_help`]) can read per-user preferences.
    ///
    /// You typically still keep your own clone of `Accounts` for your
    /// handlers - this call is just `.clone()` under the hood.
    pub fn with_accounts(mut self, accounts: Accounts) -> Self {
        self.accounts = Some(accounts);
        self
    }

    /// Attach another platform to this bot. Every registered command runs
    /// on every attached platform.
    pub fn add_platform(mut self, platform: Platform) -> Self {
        self.platforms.push(platform);
        self
    }

    /// Register a command handler.
    ///
    /// `name` is the trigger including the leading slash (`"/help"`, `"/roll"`).
    /// The handler is any async closure taking a [`Ctx`]. Names are stored
    /// lowercase and matched case-insensitively, so `/Help` finds `/help`.
    pub fn command<F, Fut>(mut self, name: impl Into<String>, handler: F) -> Self
    where
        F: Fn(Ctx) -> Fut + Send + Sync + 'static,
        Fut: Future<Output = Result<()>> + Send + 'static,
    {
        self.commands.insert(
            normalize_command_name(&name.into()),
            CommandSlot {
                handler: Handler::new(handler),
                platforms: None,
                description: None,
                descriptions_i18n: HashMap::new(),
                category: None,
                takes_user: false,
            },
        );
        self
    }

    /// Register a command and attach a short human description (used by
    /// the auto-generated `/help`).
    pub fn command_described<F, Fut>(
        mut self,
        name: impl Into<String>,
        description: impl Into<String>,
        handler: F,
    ) -> Self
    where
        F: Fn(Ctx) -> Fut + Send + Sync + 'static,
        Fut: Future<Output = Result<()>> + Send + 'static,
    {
        self.commands.insert(
            normalize_command_name(&name.into()),
            CommandSlot {
                handler: Handler::new(handler),
                platforms: None,
                description: Some(description.into()),
                descriptions_i18n: HashMap::new(),
                category: None,
                takes_user: false,
            },
        );
        self
    }

    /// Register a command with per-language descriptions.
    ///
    /// `descriptions` maps a lang code (e.g. `"en"`, `"ru"`) to the short
    /// description that [`Bot::with_default_help`] should show when the
    /// user is on that language. The first entry is also used as the
    /// default description (shown when the user's language isn't in the
    /// map).
    ///
    /// ```no_run
    /// use foukoapi::Bot;
    /// use std::collections::HashMap;
    ///
    /// let mut descs = HashMap::new();
    /// descs.insert("en".to_string(), "flip a coin".to_string());
    /// descs.insert("ru".to_string(), "подбросить монетку".to_string());
    ///
    /// Bot::new().command_described_i18n("/coin", descs, |ctx| async move {
    ///     ctx.reply("heads").await
    /// });
    /// ```
    pub fn command_described_i18n<F, Fut>(
        mut self,
        name: impl Into<String>,
        descriptions: HashMap<String, String>,
        handler: F,
    ) -> Self
    where
        F: Fn(Ctx) -> Fut + Send + Sync + 'static,
        Fut: Future<Output = Result<()>> + Send + 'static,
    {
        // Pick a default: prefer "en", otherwise any value in the map.
        let default = descriptions
            .get("en")
            .cloned()
            .or_else(|| descriptions.values().next().cloned());
        self.commands.insert(
            normalize_command_name(&name.into()),
            CommandSlot {
                handler: Handler::new(handler),
                platforms: None,
                description: default,
                descriptions_i18n: descriptions,
                category: None,
                takes_user: false,
            },
        );
        self
    }

    /// Restrict the last registered command to only run on `platforms`.
    pub fn only_on(mut self, name: &str, platforms: &[crate::PlatformKind]) -> Self {
        if let Some(slot) = self.commands.get_mut(&normalize_command_name(name)) {
            slot.platforms = Some(platforms.to_vec());
        }
        self
    }

    /// Put a command under a heading in the auto-generated `/help`.
    ///
    /// Categories are entirely optional: commands without one fall into a
    /// default group. When *no* command has a category, `/help` renders a
    /// single flat list, exactly as before. `name` is the command's
    /// trigger (e.g. `"/roll"`), `category` is any label you like
    /// (`"Fun"`, `"Economy"`, ...).
    pub fn category(mut self, name: &str, category: impl Into<String>) -> Self {
        if let Some(slot) = self.commands.get_mut(&normalize_command_name(name)) {
            slot.category = Some(category.into());
        }
        self
    }

    /// Mark a command as taking a user argument. On Discord the slash
    /// command gets a native USER option (the client shows a member
    /// picker); the chosen user's id arrives as the first token of
    /// [`Ctx::args`]. On platforms without such pickers (Telegram) this
    /// changes nothing - users keep typing an id or @mention as text.
    pub fn user_option(mut self, name: &str) -> Self {
        if let Some(slot) = self.commands.get_mut(&normalize_command_name(name)) {
            slot.takes_user = true;
        }
        self
    }

    /// Run `handler` on every incoming message, regardless of command.
    /// Useful for XP counters and audit logging.
    pub fn on_message<F, Fut>(mut self, handler: F) -> Self
    where
        F: Fn(Ctx) -> Fut + Send + Sync + 'static,
        Fut: Future<Output = Result<()>> + Send + 'static,
    {
        self.on_message.push(Handler::new(handler));
        self
    }

    /// Register a text-trigger (no leading `/`). Matches run after slash
    /// commands: if the user typed `/help`, slash dispatch wins. Only when
    /// the message isn't a slash command do text triggers fire.
    pub fn text_command<F, Fut>(
        mut self,
        pattern: impl Into<String>,
        matcher: TextMatch,
        handler: F,
    ) -> Self
    where
        F: Fn(Ctx) -> Fut + Send + Sync + 'static,
        Fut: Future<Output = Result<()>> + Send + 'static,
    {
        self.text_commands.push(TextSlot {
            pattern: pattern.into().to_lowercase(),
            matcher,
            handler: Handler::new(handler),
        });
        self
    }

    /// Register a built-in `/help` that lists every described command.
    ///
    /// When an [`Accounts`] has been attached via
    /// [`Bot::with_accounts`], the generated help picks a per-language
    /// description for each command (from
    /// [`Bot::command_described_i18n`]) and a localised header, so a
    /// Russian user sees `команды:` and Russian summaries while an
    /// English user keeps the default.
    pub fn with_default_help(self) -> Self {
        // Snapshot (name, default_desc, i18n_map, category, platforms) for
        // every described command, so the `/help` closure can render at
        // dispatch time without holding a lock on `self`.
        type HelpEntry = (
            String,
            Option<String>,
            HashMap<String, String>,
            Option<String>,
            Option<Vec<crate::PlatformKind>>,
        );
        let snapshot: Vec<HelpEntry> = self
            .commands
            .iter()
            .filter(|(_, slot)| slot.description.is_some() || !slot.descriptions_i18n.is_empty())
            .map(|(name, slot)| {
                (
                    name.clone(),
                    slot.description.clone(),
                    slot.descriptions_i18n.clone(),
                    slot.category.clone(),
                    slot.platforms.clone(),
                )
            })
            .collect();
        let accounts = self.accounts.clone();
        self.command("/help", move |ctx| {
            let snapshot = snapshot.clone();
            let accounts = accounts.clone();
            async move {
                // Figure out the user's language. Falls back to "en" when
                // we have no accounts handle or the lookup fails.
                let lang = match &accounts {
                    Some(a) => a
                        .lang_for(ctx.platform(), ctx.user_id())
                        .await
                        .unwrap_or_else(|_| "en".to_owned()),
                    None => "en".to_owned(),
                };
                let (title, intro) = match lang.as_str() {
                    "ru" => ("\u{1F4D6} Команды", "Вот что я умею:"),
                    _ => ("\u{1F4D6} Commands", "Here's what I can do:"),
                };

                let mut sorted = snapshot;
                sorted.sort_by(|a, b| a.0.cmp(&b.0));

                // Resolve each command's line and its group. Commands that
                // don't run on this platform are skipped entirely - no
                // point advertising /avatar to Telegram users. Groups keep
                // first-seen order so a bot controls layout by the order it
                // assigns categories, not alphabetically.
                let mut groups: Vec<(String, String)> = Vec::new();
                let has_categories = sorted.iter().any(|(_, _, _, cat, _)| cat.is_some());
                for (name, default_desc, i18n, category, platforms) in sorted {
                    if let Some(allowed) = &platforms {
                        if !allowed.contains(&ctx.platform()) {
                            continue;
                        }
                    }
                    let desc = i18n
                        .get(&lang)
                        .cloned()
                        .or(default_desc)
                        .unwrap_or_default();
                    let line = if desc.is_empty() {
                        format!("{name}\n")
                    } else {
                        format!("{name} - {desc}\n")
                    };
                    // Without categories everything shares one bucket.
                    let group = category.unwrap_or_default();
                    match groups.iter_mut().find(|(g, _)| g == &group) {
                        Some((_, body)) => body.push_str(&line),
                        None => groups.push((group, line)),
                    }
                }

                let mut em = crate::Embed::new().title(title).color(0x5B8DEF);
                if has_categories {
                    em = em.description(intro);
                    for (group, body) in groups {
                        let heading = if group.is_empty() {
                            match lang.as_str() {
                                "ru" => "Прочее".to_owned(),
                                _ => "Other".to_owned(),
                            }
                        } else {
                            group
                        };
                        em = em.field(heading, body.trim_end().to_owned());
                    }
                } else {
                    // Flat list: one description block, no field headings.
                    let body = groups.into_iter().map(|(_, b)| b).collect::<String>();
                    em = em.description(format!("{intro}\n\n{}", body.trim_end()));
                }
                ctx.reply_with(crate::Reply::embed(em)).await
            }
        })
    }

    /// Register a built-in `/lang` command with inline buttons.
    ///
    /// No argument: shows the current language plus a button for every
    /// language in `supported`. Tapping a button switches instantly -
    /// no typing `/lang ru` needed. Typing `/lang ru` still works for
    /// users on clients without inline keyboards.
    ///
    /// Callback ids used: `foukoapi:lang:<code>`. They don't clash with
    /// anything the bot defines itself.
    ///
    /// Requires [`Bot::with_accounts`] to have been called - without an
    /// [`Accounts`] the command politely says so.
    pub fn with_default_lang_command<I, S>(self, supported: I) -> Self
    where
        I: IntoIterator<Item = S>,
        S: Into<String>,
    {
        // `foukoapi:lang:<invoker>:<code>` - we glue the invoker user id
        // into the callback so only the person who ran `/lang` can press
        // a button that was meant for them.
        const CB_PREFIX: &str = "foukoapi:lang:";

        let supported: Vec<String> = supported
            .into_iter()
            .map(|s| s.into().to_ascii_lowercase())
            .collect();
        let accounts = self.accounts.clone();
        self.command_described(
            "/lang",
            "switch language, e.g. /lang ru",
            move |ctx| {
                let accounts = accounts.clone();
                let supported = supported.clone();
                async move {
                    let Some(accounts) = accounts else {
                        return ctx
                            .reply(
                                "language switching is not wired up on this bot (the author forgot to call Bot::with_accounts)",
                            )
                            .await;
                    };

                    // Button press: `foukoapi:lang:<invoker>:<code>`.
                    // Parse out both parts and, if we have an invoker id,
                    // make sure it matches the tapping user.
                    let (requested, invoker): (Option<String>, Option<String>) =
                        if let Some(data) = ctx.callback_data() {
                            if let Some(rest) = data.strip_prefix(CB_PREFIX) {
                                let mut parts = rest.splitn(2, ':');
                                let invoker = parts.next().map(|s| s.to_owned());
                                let code = parts.next().map(|s| s.to_ascii_lowercase());
                                (code, invoker)
                            } else {
                                (None, None)
                            }
                        } else {
                            let arg = ctx.args().trim().to_ascii_lowercase();
                            if arg.is_empty() {
                                (None, None)
                            } else {
                                (Some(arg), None)
                            }
                        };

                    // Invoker guard: if this is a button press and the
                    // tap came from someone else, reject quietly. The
                    // "someone else" case is common in group chats.
                    if let Some(inv) = invoker.as_deref() {
                        if !inv.is_empty() && inv != ctx.user_id() {
                            let lang_now = accounts
                                .lang_for(ctx.platform(), ctx.user_id())
                                .await
                                .unwrap_or_else(|_| "en".into());
                            let msg = match lang_now.as_str() {
                                "ru" => "эта кнопка не для тебя",
                                _ => "this button isn't for you",
                            };
                            return ctx.reply(msg).await;
                        }
                    }

                    let current = accounts
                        .lang_for(ctx.platform(), ctx.user_id())
                        .await
                        .unwrap_or_else(|_| "en".into());

                    match requested {
                        None => {
                            // Show the picker. Embed the invoker id in
                            // every callback id so follow-up taps can be
                            // gated to the same user.
                            let body = match current.as_str() {
                                "ru" => format!(
                                    "текущий язык: {current}\nвыбери язык:"
                                ),
                                _ => format!(
                                    "current language: {current}\npick a language:"
                                ),
                            };
                            if supported.is_empty() {
                                return ctx.reply(body).await;
                            }
                            let invoker_id = ctx.user_id().to_owned();
                            let kb =
                                build_lang_keyboard(&supported, &current, &invoker_id, CB_PREFIX);
                            ctx.reply_with(crate::Reply::text(body).keyboard(kb)).await
                        }
                        Some(code) => {
                            if !supported.is_empty() && !supported.contains(&code) {
                                let list = supported.join(", ");
                                let msg = match current.as_str() {
                                    "ru" => format!("поддерживаемые языки: {list}"),
                                    _ => format!("supported languages: {list}"),
                                };
                                return ctx.reply(msg).await;
                            }
                            accounts
                                .set_lang(ctx.platform(), ctx.user_id(), &code)
                                .await?;

                            // Re-render the picker with the new pick
                            // marked. When this is a button press we
                            // edit the original message; when it was a
                            // typed `/lang ru`, edit_reply falls back
                            // to a fresh message.
                            let invoker_id = ctx.user_id().to_owned();
                            let body = match code.as_str() {
                                "ru" => format!(
                                    "язык: {code} \u{2705}\nвыбери другой:"
                                ),
                                _ => format!(
                                    "language set to {code} \u{2705}\npick another:"
                                ),
                            };
                            if supported.is_empty() {
                                return ctx.edit_reply(body).await;
                            }
                            let kb =
                                build_lang_keyboard(&supported, &code, &invoker_id, CB_PREFIX);
                            ctx.edit_reply(crate::Reply::text(body).keyboard(kb)).await
                        }
                    }
                }
            },
        )
    }

    /// Register a built-in `/link` command with inline buttons.
    ///
    /// What the user gets:
    ///
    /// - `/link` with no arguments, not linked yet: issues a 6-char code
    ///   and shows a **cancel** button.
    /// - `/link` when already linked: shows both identities + current
    ///   primary, with **pick primary** and **unlink** buttons.
    /// - `/link CODE`: redeems a code issued on another platform (through
    ///   [`Accounts::redeem_link`]) and shows the primary-picker buttons.
    /// - Button presses are routed back through the same `/link` handler,
    ///   so the whole dance lives on one command.
    ///
    /// Works in English and Russian out of the box. The button-callback
    /// ids used internally start with `foukoapi:link:` so they don't clash
    /// with anything the bot defines itself.
    ///
    /// Requires [`Bot::with_accounts`] to have been called.
    pub fn with_default_link_command(self) -> Self {
        const CB_UNLINK: &str = "foukoapi:link:unlink";
        const CB_CANCEL: &str = "foukoapi:link:cancel";
        const CB_PRIMARY_ME: &str = "foukoapi:link:primary_me";
        const CB_PRIMARY_PARTNER: &str = "foukoapi:link:primary_partner";

        let mut descs = HashMap::new();
        descs.insert(
            "en".to_owned(),
            "Link or unlink accounts across platforms".to_owned(),
        );
        descs.insert(
            "ru".to_owned(),
            "Связать или отвязать аккаунты между платформами".to_owned(),
        );

        let accounts = self.accounts.clone();
        self.command_described_i18n("/link", descs, move |ctx| {
            let accounts = accounts.clone();
            async move {
                let Some(accounts) = accounts else {
                    return ctx
                        .reply(
                            "account linking is not wired up on this bot (the author forgot to call Bot::with_accounts)",
                        )
                        .await;
                };
                let lang = accounts
                    .lang_for(ctx.platform(), ctx.user_id())
                    .await
                    .unwrap_or_else(|_| "en".into());

                // DM-only guard. `/link` juggles short-lived codes tied
                // to a specific account; running it in a public chat
                // would splash the code to every onlooker, which is a
                // recipe for someone else hijacking the link. Refuse
                // outside of direct messages.
                if !ctx.is_dm() {
                    let body = match lang.as_str() {
                        "ru" => "команда /link работает только в личке с ботом. открой переписку и попробуй снова.",
                        _ => "/link only works in a private chat with the bot. open the bot's DM and try again.",
                    };
                    return ctx.reply(body).await;
                }

                if let Some(data) = ctx.callback_data() {
                    return handle_link_callback(
                        &ctx,
                        &accounts,
                        data,
                        &lang,
                        CB_UNLINK,
                        CB_CANCEL,
                        CB_PRIMARY_ME,
                        CB_PRIMARY_PARTNER,
                    )
                    .await;
                }

                let arg = ctx.args().trim().to_owned();

                if arg.starts_with("foukoapi:link:") {
                    return handle_link_callback(
                        &ctx,
                        &accounts,
                        &arg,
                        &lang,
                        CB_UNLINK,
                        CB_CANCEL,
                        CB_PRIMARY_ME,
                        CB_PRIMARY_PARTNER,
                    )
                    .await;
                }

                if arg.is_empty() {
                    return link_status_reply(&ctx, &accounts, &lang, CB_UNLINK, CB_CANCEL)
                        .await;
                }

                match accounts
                    .redeem_link(&arg, ctx.platform(), ctx.user_id())
                    .await
                {
                    Ok(res) => {
                        let (title, body, footer) = match lang.as_str() {
                            "ru" => (
                                "\u{2705} Аккаунты связаны",
                                format!(
                                    "**{}** \u{2194} **{}**",
                                    platform_title(platform_of(&res.primary)),
                                    platform_title(platform_of(&res.partner))
                                ),
                                "Выбери основной аккаунт. На нём остаются XP, монеты и настройки. Выбор делается **один раз** - потом поменять нельзя, можно только /link -> Отвязать.",
                            ),
                            _ => (
                                "\u{2705} Accounts Linked",
                                format!(
                                    "**{}** \u{2194} **{}**",
                                    platform_title(platform_of(&res.primary)),
                                    platform_title(platform_of(&res.partner))
                                ),
                                "Pick the primary - XP, coins and settings live there. You can only pick **once**; after that, /link -> Unlink is the only reset.",
                            ),
                        };
                        let me = format!("{}:{}", ctx.platform(), ctx.user_id());
                        let em = crate::Embed::new()
                            .title(title)
                            .description(body)
                            .footer(footer)
                            .color(LINK_COLOR);
                        let kb = primary_picker_keyboard(
                            &lang,
                            &me,
                            &res.partner,
                            CB_PRIMARY_ME,
                            CB_PRIMARY_PARTNER,
                        );
                        ctx.reply_with(crate::Reply::embed(em).keyboard(kb)).await
                    }
                    Err(e) => {
                        let (title, desc) = match lang.as_str() {
                            "ru" => ("\u{274C} Не получилось", format!("{e}")),
                            _ => ("\u{274C} Link Failed", format!("{e}")),
                        };
                        let em = crate::Embed::new()
                            .title(title)
                            .description(desc)
                            .color(ERROR_COLOR);
                        ctx.reply_with(crate::Reply::embed(em)).await
                    }
                }
            }
        })
    }

    /// Handler invoked when an incoming message starts with `/` but doesn't
    /// match any registered command. Optional.
    pub fn fallback<F, Fut>(mut self, handler: F) -> Self
    where
        F: Fn(Ctx) -> Fut + Send + Sync + 'static,
        Fut: Future<Output = Result<()>> + Send + 'static,
    {
        self.fallback = Some(Handler::new(handler));
        self
    }

    /// List registered commands as `Command` values.
    pub fn commands(&self) -> Vec<Command> {
        self.commands
            .iter()
            .map(|(name, slot)| Command::new(name.clone(), slot.handler.clone()))
            .collect()
    }

    /// Snapshot `(name, description, takes_user)` for every registered
    /// command. Used by adapters (e.g. Discord) to register native
    /// slash-command metadata on the platform side.
    #[doc(hidden)]
    pub fn command_snapshot(&self) -> Vec<(String, Option<String>, bool)> {
        self.commands
            .iter()
            .map(|(name, slot)| (name.clone(), slot.description.clone(), slot.takes_user))
            .collect()
    }

    /// Run the bot until every platform stops or the task is cancelled.
    pub async fn run(self) -> Result<()> {
        if self.platforms.is_empty() {
            return Err(Error::NoPlatforms);
        }

        // Snapshot the command metadata before we move `self.commands`
        // into the router - Discord adapter uses it to register native
        // slash commands with the platform so `/help` shows up in the
        // client's autocomplete list.
        let commands_meta: Vec<(String, Option<String>, bool)> = self
            .commands
            .iter()
            .map(|(name, slot)| (name.clone(), slot.description.clone(), slot.takes_user))
            .collect();

        let router = Arc::new(Router {
            commands: self
                .commands
                .into_iter()
                .map(|(k, v)| {
                    (
                        k,
                        RouterSlot {
                            handler: v.handler,
                            platforms: v.platforms,
                        },
                    )
                })
                .collect(),
            text_commands: self
                .text_commands
                .into_iter()
                .map(|t| RouterTextSlot {
                    pattern: t.pattern,
                    matcher: t.matcher,
                    handler: t.handler,
                })
                .collect(),
            fallback: self.fallback,
            on_message: self.on_message,
            rate_limiter: self.rate_limiter,
            on_rate_limited: self.on_rate_limited,
            max_update_age: self.max_update_age,
            on_flood: self.on_flood,
        });

        let mut tasks: Vec<BoxFuture<'static, Result<()>>> = Vec::new();

        for platform in self.platforms {
            let router = Arc::clone(&router);
            let name = platform.kind.to_string();
            let notifier = self.notifier.clone();
            match platform.config {
                #[cfg(feature = "telegram")]
                PlatformConfig::Telegram { token } => {
                    let cmds = commands_meta.clone();
                    let menu_app = self.menu_web_app.clone();
                    tasks.push(Box::pin(async move {
                        adapters::telegram::run(token, router, cmds, notifier, menu_app).await
                    }));
                }
                #[cfg(not(feature = "telegram"))]
                PlatformConfig::Telegram { .. } => {
                    tracing::warn!(
                        "Telegram platform configured but the `telegram` feature is off; skipping"
                    );
                }

                #[cfg(feature = "discord")]
                PlatformConfig::Discord { token } => {
                    let cmds = commands_meta.clone();
                    let presence = self.presence.clone();
                    tasks.push(Box::pin(async move {
                        adapters::discord::run(token, router, cmds, notifier, presence).await
                    }));
                }
                #[cfg(not(feature = "discord"))]
                PlatformConfig::Discord { .. } => {
                    tracing::warn!(
                        "Discord platform configured but the `discord` feature is off; skipping"
                    );
                }
            }
            tracing::info!(platform = %name, "adapter registered");
        }

        if tasks.is_empty() {
            return Err(Error::NoPlatforms);
        }

        // Run every adapter concurrently. The whole bot stops as soon as one
        // of them returns - successfully or otherwise.
        let (result, _, _rest) = future::select_all(tasks).await;
        result
    }
}

impl Default for Bot {
    fn default() -> Self {
        Self::new()
    }
}

/// Lowercase a command trigger so registration and dispatch agree on the
/// key. `/Help` and `/help` are the same command.
fn normalize_command_name(name: &str) -> String {
    name.to_lowercase()
}

/// Turn a callback-button id into the slash-command name that should
/// handle it.
///
/// Convention:
/// - `foukoapi:<cmd>:<rest>` -> `/<cmd>` (built-in API commands)
/// - `<cmd>:<rest>`          -> `/<cmd>` (bot-defined commands)
/// - anything else           -> `None`
///
/// Returning `None` just means "I don't know, let the router fall
/// through to the usual text/fallback paths".
fn callback_to_command(data: &str) -> Option<String> {
    let first = data.split(':').next()?;
    // Unwrap the API-owned prefix so `foukoapi:link:me` also resolves to
    // `/link`, not to `/foukoapi`.
    let cmd = if first == "foukoapi" {
        data.split(':').nth(1)?
    } else {
        first
    };
    if cmd.is_empty() {
        return None;
    }
    Some(normalize_command_name(&format!("/{cmd}")))
}

/// Build the `/lang` inline keyboard: one row of up to 3 buttons per
/// chunk, the current language marked with a star.
fn build_lang_keyboard(
    supported: &[String],
    current: &str,
    invoker_id: &str,
    cb_prefix: &str,
) -> crate::Keyboard {
    let mut kb = crate::Keyboard::new();
    for chunk in supported.chunks(3) {
        let row: Vec<crate::Button> = chunk
            .iter()
            .map(|code| {
                let marker = if code == current { "\u{2B50} " } else { "" };
                let label = format!("{marker}{}", lang_label(code));
                crate::Button::callback(label, format!("{cb_prefix}{invoker_id}:{code}"))
            })
            .collect();
        kb = kb.row(row);
    }
    kb
}

/// Pretty label for a language code, with a flag-ish prefix.
///
/// Covers the handful of codes most bots care about; anything unknown
/// falls back to the upper-cased code so the picker still shows
/// *something*.
fn lang_label(code: &str) -> String {
    match code {
        "en" => "\u{1F1FA}\u{1F1F8} English".to_owned(),
        "ru" => "\u{1F1F7}\u{1F1FA} Русский".to_owned(),
        "uk" => "\u{1F1FA}\u{1F1E6} Українська".to_owned(),
        "de" => "\u{1F1E9}\u{1F1EA} Deutsch".to_owned(),
        "fr" => "\u{1F1EB}\u{1F1F7} Français".to_owned(),
        "es" => "\u{1F1EA}\u{1F1F8} Español".to_owned(),
        "it" => "\u{1F1EE}\u{1F1F9} Italiano".to_owned(),
        "pt" => "\u{1F1F5}\u{1F1F9} Português".to_owned(),
        "pl" => "\u{1F1F5}\u{1F1F1} Polski".to_owned(),
        "tr" => "\u{1F1F9}\u{1F1F7} Türkçe".to_owned(),
        "ja" => "\u{1F1EF}\u{1F1F5} 日本語".to_owned(),
        "zh" => "\u{1F1E8}\u{1F1F3} 中文".to_owned(),
        "ko" => "\u{1F1F0}\u{1F1F7} 한국어".to_owned(),
        other => other.to_ascii_uppercase(),
    }
}

// ---------------------------------------------------------------------------
// Built-in `/link` helpers, shared by `with_default_link_command`.
// ---------------------------------------------------------------------------

/// Accent colours used by the built-in `/link` embeds on Discord.
/// Ignored on Telegram/Matrix where there's nothing to paint.
const LINK_COLOR: u32 = 0x5B8DEF;
const ERROR_COLOR: u32 = 0xE74C3C;

/// Pretty platform name for an identity of the form `"platform:id"`.
///
/// Used by `/link` and friends to surface "telegram" / "discord" in
/// place of raw numeric ids, so the user doesn't have to squint at
/// `560024252393455645` to figure out which account is which.
fn platform_of(ident: &str) -> &str {
    ident.split(':').next().unwrap_or(ident)
}

/// Render the "linked or not" status screen with an unlink button.
async fn link_status_reply(
    ctx: &Ctx,
    accounts: &Accounts,
    lang: &str,
    cb_unlink: &str,
    cb_cancel: &str,
) -> Result<()> {
    let me = format!("{}:{}", ctx.platform(), ctx.user_id());
    let partner = accounts.partner_for(ctx.platform(), ctx.user_id()).await?;
    match partner {
        Some(p) => {
            let (title, platforms_label, foot) = match lang {
                "ru" => (
                    "\u{1F517} Связанные аккаунты",
                    "Платформы",
                    "Отвязать можно один раз. После отвязки у партнёрской платформы будет чистый профиль.",
                ),
                _ => (
                    "\u{1F517} Linked Accounts",
                    "Platforms",
                    "You can unlink once. After that the other side starts with a fresh profile.",
                ),
            };
            let em = crate::Embed::new()
                .title(title)
                .field(
                    platforms_label,
                    format!(
                        "**{}** \u{2194} **{}**",
                        platform_title(platform_of(&me)),
                        platform_title(platform_of(&p))
                    ),
                )
                .footer(foot)
                .color(LINK_COLOR);
            let kb = crate::Keyboard::new().row([crate::Button::callback(
                match lang {
                    "ru" => "\u{1F494} Отвязать",
                    _ => "\u{1F494} Unlink",
                },
                cb_unlink,
            )]);
            ctx.reply_with(crate::Reply::embed(em).keyboard(kb)).await
        }
        None => {
            let code = accounts.start_link(ctx.platform(), ctx.user_id()).await?;
            let (title, code_label, how_label, how_value, foot) = match lang {
                "ru" => (
                    "\u{1F517} Код привязки",
                    "Код",
                    "Как использовать",
                    format!("Открой бота на другой платформе и отправь:\n`/link {code}`"),
                    "Код живёт 5 минут.",
                ),
                _ => (
                    "\u{1F517} Link Code",
                    "Code",
                    "How To Use",
                    format!("Open the bot on another platform and send:\n`/link {code}`"),
                    "The code expires in 5 minutes.",
                ),
            };
            let em = crate::Embed::new()
                .title(title)
                .field(code_label, format!("`{code}`"))
                .field(how_label, how_value)
                .footer(foot)
                .color(LINK_COLOR);
            let kb = crate::Keyboard::new().row([crate::Button::callback(
                match lang {
                    "ru" => "\u{274C} Отмена",
                    _ => "\u{274C} Cancel",
                },
                cb_cancel,
            )]);
            ctx.reply_with(crate::Reply::embed(em).keyboard(kb)).await
        }
    }
}

/// Pretty, capitalised form of a platform id ("telegram" -> "Telegram").
fn platform_title(raw: &str) -> String {
    let mut chars = raw.chars();
    match chars.next() {
        Some(c) => c.to_uppercase().collect::<String>() + chars.as_str(),
        None => String::new(),
    }
}

/// Two "pick primary" buttons shown once, right after `/link CODE`.
fn primary_picker_keyboard(
    lang: &str,
    me: &str,
    partner: &str,
    cb_me: &str,
    cb_partner: &str,
) -> crate::Keyboard {
    let (me_label, partner_label) = match lang {
        "ru" => (
            format!("\u{1F4CD} Эта ({})", platform_title(platform_of(me))),
            format!(
                "\u{1F517} Другая ({})",
                platform_title(platform_of(partner))
            ),
        ),
        _ => (
            format!("\u{1F4CD} This ({})", platform_title(platform_of(me))),
            format!("\u{1F517} Other ({})", platform_title(platform_of(partner))),
        ),
    };
    crate::Keyboard::new().row([
        crate::Button::callback(me_label, cb_me),
        crate::Button::callback(partner_label, cb_partner),
    ])
}

/// Shared handler for every `foukoapi:link:*` button.
#[allow(clippy::too_many_arguments)]
async fn handle_link_callback(
    ctx: &Ctx,
    accounts: &Accounts,
    data: &str,
    lang: &str,
    cb_unlink: &str,
    cb_cancel: &str,
    cb_primary_me: &str,
    cb_primary_partner: &str,
) -> Result<()> {
    if data == cb_cancel {
        let (title, desc) = match lang {
            "ru" => (
                "\u{274C} Отменено",
                "Запусти /link ещё раз, когда будешь готов.",
            ),
            _ => (
                "\u{274C} Cancelled",
                "Run /link again whenever you're ready.",
            ),
        };
        let em = crate::Embed::new()
            .title(title)
            .description(desc)
            .color(ERROR_COLOR);
        return ctx.edit_reply(crate::Reply::embed(em)).await;
    }

    if data == cb_primary_me || data == cb_primary_partner {
        let me = format!("{}:{}", ctx.platform(), ctx.user_id());
        let partner = match accounts.partner_for(ctx.platform(), ctx.user_id()).await? {
            Some(p) => p,
            None => {
                let (title, desc) = match lang {
                    "ru" => ("\u{2753} Нет связки", "Сначала выполни /link CODE."),
                    _ => ("\u{2753} No Link", "Redeem a /link CODE first."),
                };
                let em = crate::Embed::new()
                    .title(title)
                    .description(desc)
                    .color(ERROR_COLOR);
                return ctx.edit_reply(crate::Reply::embed(em)).await;
            }
        };

        // One-shot guard: once primary is picked, the lock key disables
        // further presses from either side. set_nx makes claiming the
        // lock atomic, so two racing taps can't both win.
        let lock_key = format!("foukoapi:link:primary_locked:{me}");
        let partner_lock = format!("foukoapi:link:primary_locked:{partner}");
        let partner_already = accounts
            .storage_ref()
            .get(&partner_lock)
            .await
            .ok()
            .flatten()
            .is_some();
        let claimed = if partner_already {
            false
        } else {
            match accounts.storage_ref().set_nx(&lock_key, "1").await {
                Ok(won) => won,
                Err(e) => {
                    tracing::warn!(error = %e, "link: could not claim primary lock");
                    let (title, desc) = match lang {
                        "ru" => (
                            "\u{274C} Ошибка",
                            "Не получилось сохранить выбор. Попробуй ещё раз.",
                        ),
                        _ => ("\u{274C} Error", "Could not save your choice. Try again."),
                    };
                    let em = crate::Embed::new()
                        .title(title)
                        .description(desc)
                        .color(ERROR_COLOR);
                    return ctx.edit_reply(crate::Reply::embed(em)).await;
                }
            }
        };
        if !claimed {
            let (title, desc) = match lang {
                "ru" => (
                    "\u{1F512} Уже выбрано",
                    "Основная платформа уже зафиксирована. Поменять можно только через /link -> Отвязать.",
                ),
                _ => (
                    "\u{1F512} Already Locked",
                    "The primary is already locked in. You can only change it via /link -> Unlink.",
                ),
            };
            let em = crate::Embed::new()
                .title(title)
                .description(desc)
                .color(ERROR_COLOR);
            return ctx.edit_reply(crate::Reply::embed(em)).await;
        }

        let chosen = if data == cb_primary_me {
            me.clone()
        } else {
            partner.clone()
        };
        accounts
            .set_primary(ctx.platform(), ctx.user_id(), &chosen)
            .await?;
        if let Err(e) = accounts.storage_ref().set(&partner_lock, "1").await {
            tracing::warn!(error = %e, "link: could not set partner primary lock");
        }

        let (title, desc) = match lang {
            "ru" => (
                "\u{2705} Основная выбрана",
                format!(
                    "Основной аккаунт: **{}**. Поменять больше нельзя - только через /link -> Отвязать.",
                    platform_title(platform_of(&chosen))
                ),
            ),
            _ => (
                "\u{2705} Primary Locked",
                format!(
                    "Primary: **{}**. It can't be changed anymore - use /link -> Unlink to reset.",
                    platform_title(platform_of(&chosen))
                ),
            ),
        };
        let em = crate::Embed::new()
            .title(title)
            .description(desc)
            .color(LINK_COLOR);
        return ctx.edit_reply(crate::Reply::embed(em)).await;
    }

    if data == cb_unlink {
        let me = format!("{}:{}", ctx.platform(), ctx.user_id());
        let partner_before = accounts.partner_for(ctx.platform(), ctx.user_id()).await?;
        return match accounts.unlink(ctx.platform(), ctx.user_id()).await? {
            Some(partner) => {
                // Release the primary-lock markers on both sides.
                let _ = accounts
                    .storage_ref()
                    .del(&format!("foukoapi:link:primary_locked:{me}"))
                    .await;
                if let Some(p) = partner_before.as_deref() {
                    let _ = accounts
                        .storage_ref()
                        .del(&format!("foukoapi:link:primary_locked:{p}"))
                        .await;
                }
                let (title, desc) = match lang {
                    "ru" => (
                        "\u{1F494} Отвязано",
                        format!(
                            "Больше не связан с **{}**. Основная платформа сохраняет свой профиль, остальные - получают чистый.",
                            platform_title(platform_of(&partner))
                        ),
                    ),
                    _ => (
                        "\u{1F494} Unlinked",
                        format!(
                            "No longer linked to **{}**. The primary keeps its profile; the other side starts fresh.",
                            platform_title(platform_of(&partner))
                        ),
                    ),
                };
                let em = crate::Embed::new()
                    .title(title)
                    .description(desc)
                    .color(LINK_COLOR);
                ctx.edit_reply(crate::Reply::embed(em)).await
            }
            None => {
                let (title, desc) = match lang {
                    "ru" => ("\u{2753} Нечего отвязывать", "Связанного аккаунта нет."),
                    _ => ("\u{2753} Nothing To Unlink", "No partner was set."),
                };
                let em = crate::Embed::new()
                    .title(title)
                    .description(desc)
                    .color(ERROR_COLOR);
                ctx.reply_with(crate::Reply::embed(em)).await
            }
        };
    }

    Ok(())
}

/// Router used by platform adapters to dispatch incoming updates.
///
/// Not part of the public API surface end-users should rely on - it exists
/// mainly so adapters in [`crate::adapters`] can hold a typed handle to the
/// bot's commands. Treat it as semver-exempt.
#[doc(hidden)]
#[derive(Clone)]
pub struct Router {
    pub(crate) commands: HashMap<String, RouterSlot>,
    pub(crate) text_commands: Vec<RouterTextSlot>,
    pub(crate) fallback: Option<Handler>,
    pub(crate) on_message: Vec<Handler>,
    pub(crate) rate_limiter: Option<Arc<RateLimiter>>,
    pub(crate) on_rate_limited: Option<Handler>,
    pub(crate) max_update_age: Option<std::time::Duration>,
    pub(crate) on_flood: Option<FloodHook>,
}

impl Router {
    /// How stale an update may be before an adapter should drop it, if a
    /// limit was configured. Adapters that carry an update timestamp
    /// (Telegram) consult this to avoid replaying a backlog after downtime.
    #[doc(hidden)]
    pub fn max_update_age(&self) -> Option<std::time::Duration> {
        self.max_update_age
    }
}

#[doc(hidden)]
#[derive(Clone)]
pub(crate) struct RouterSlot {
    pub(crate) handler: Handler,
    pub(crate) platforms: Option<Vec<crate::PlatformKind>>,
}

#[doc(hidden)]
#[derive(Clone)]
pub(crate) struct RouterTextSlot {
    pub(crate) pattern: String,
    pub(crate) matcher: TextMatch,
    pub(crate) handler: Handler,
}

/// Boxed flood-alert callback: gets the update count for the window.
pub(crate) type FloodHandler = Arc<dyn Fn(u64) -> BoxFuture<'static, ()> + Send + Sync + 'static>;

/// The flood watchdog wiring carried from [`Bot::on_flood`] to the router.
#[derive(Clone)]
pub(crate) struct FloodHook {
    pub(crate) window: FloodWindow,
    pub(crate) handler: FloodHandler,
}

/// A fixed 60-second counting window with a fire cooldown.
///
/// Every incoming update calls [`FloodWindow::hit`]; when the count inside
/// the current window crosses the threshold, `hit` returns `Some(count)` -
/// but at most once per cooldown, so an ongoing flood alerts once instead
/// of on every message. Clones share state, matching how the router is
/// cloned per adapter.
#[derive(Clone)]
pub(crate) struct FloodWindow {
    inner: Arc<FloodWindowInner>,
}

struct FloodWindowInner {
    /// Alert threshold: strictly more than this many hits per window fires.
    per_minute: u64,
    /// Minimum gap between two alerts.
    cooldown: std::time::Duration,
    /// Hits in the current window.
    count: std::sync::atomic::AtomicU64,
    /// Window start and last-alert bookkeeping.
    state: std::sync::Mutex<FloodState>,
}

struct FloodState {
    window_start: std::time::Instant,
    last_fired: Option<std::time::Instant>,
}

/// Length of the counting window.
const FLOOD_WINDOW: std::time::Duration = std::time::Duration::from_secs(60);

impl FloodWindow {
    pub(crate) fn new(per_minute: u32, cooldown: std::time::Duration) -> Self {
        Self {
            inner: Arc::new(FloodWindowInner {
                per_minute: u64::from(per_minute),
                cooldown,
                count: std::sync::atomic::AtomicU64::new(0),
                state: std::sync::Mutex::new(FloodState {
                    window_start: std::time::Instant::now(),
                    last_fired: None,
                }),
            }),
        }
    }

    /// Count one update at `now`. Returns `Some(count)` when the window
    /// total just crossed the threshold and the cooldown allows an alert.
    pub(crate) fn hit(&self, now: std::time::Instant) -> Option<u64> {
        let mut state = match self.inner.state.lock() {
            Ok(s) => s,
            // A poisoned lock must not wedge dispatch; skip the check.
            Err(poisoned) => poisoned.into_inner(),
        };
        if now.duration_since(state.window_start) >= FLOOD_WINDOW {
            state.window_start = now;
            self.inner
                .count
                .store(0, std::sync::atomic::Ordering::Relaxed);
        }
        let count = self
            .inner
            .count
            .fetch_add(1, std::sync::atomic::Ordering::Relaxed)
            + 1;
        if count <= self.inner.per_minute {
            return None;
        }
        let cooled = match state.last_fired {
            Some(t) => now.duration_since(t) >= self.inner.cooldown,
            None => true,
        };
        if !cooled {
            return None;
        }
        state.last_fired = Some(now);
        Some(count)
    }
}

impl Router {
    /// Dispatch an incoming message. First runs every `on_message` hook
    /// (errors are logged, not propagated), then tries slash commands,
    /// then plain-text triggers, then the fallback.
    ///
    /// Button presses land here too: adapters populate
    /// [`Ctx::callback_data`] with the id of the pressed button. We route
    /// those to a command by convention - a callback id that looks like
    /// `foukoapi:link:me` or `something:xyz` is mapped to the command
    /// that "owns" it (`/link` and `/something`), so a single handler
    /// serves both typed text and inline taps.
    #[doc(hidden)]
    pub async fn dispatch(&self, ctx: Ctx) -> Result<()> {
        // Flood watchdog first, before any per-user limiting, so the count
        // reflects the raw incoming flow. The alert handler is spawned so
        // a slow one (posting to an ops channel, say) can't stall dispatch.
        if let Some(flood) = &self.on_flood {
            if let Some(count) = flood.window.hit(std::time::Instant::now()) {
                let handler = Arc::clone(&flood.handler);
                tokio::spawn(async move {
                    handler(count).await;
                });
            }
        }

        // Rate limit before anything else - including the on_message hooks
        // - so a flood can't farm XP, hammer handlers, or pile up work. We
        // key on platform + user so one noisy user can't throttle everyone
        // else. On the first deny of a window we optionally let a handler
        // tell them to slow down; further denials in the same window are
        // dropped silently so the bot doesn't answer every flood message.
        if let Some(limiter) = &self.rate_limiter {
            let key = format!("{}:{}", ctx.platform(), ctx.user_id());
            if let crate::ratelimit::Decision::Deny { first, .. } = limiter.check(&key) {
                if first {
                    if let Some(hook) = &self.on_rate_limited {
                        // Best effort: a failure here must not escalate.
                        if let Err(e) = hook.call(ctx).await {
                            tracing::debug!(error = %e, "on_rate_limited hook error");
                        }
                    }
                }
                return Ok(());
            }
        }

        for hook in &self.on_message {
            if let Err(e) = hook.call(ctx.clone()).await {
                tracing::debug!(error = %e, "on_message hook error");
            }
        }

        // Button-callback path: try to find a command whose name matches
        // the callback prefix. Supports `<cmd>:<rest>` and the API-owned
        // `foukoapi:<cmd>:<rest>`. If we find a match, run its handler
        // and return; otherwise fall through to text dispatch.
        if let Some(data) = ctx.callback_data() {
            if let Some(cmd_name) = callback_to_command(data) {
                if let Some(slot) = self.commands.get(&cmd_name) {
                    if let Some(allowed) = &slot.platforms {
                        if !allowed.contains(&ctx.platform()) {
                            return Ok(());
                        }
                    }
                    return slot.handler.call(ctx).await;
                }
            }
        }

        let text = ctx.text().trim();

        // Slash commands first. Match case-insensitively so `/Help` from a
        // phone keyboard's auto-capitalisation still lands on `/help`.
        if text.starts_with('/') {
            let cmd_word = text.split_whitespace().next().unwrap_or("");
            let cmd_clean = cmd_word.split('@').next().unwrap_or(cmd_word);
            let cmd_key = normalize_command_name(cmd_clean);
            if let Some(slot) = self.commands.get(&cmd_key) {
                if let Some(allowed) = &slot.platforms {
                    if !allowed.contains(&ctx.platform()) {
                        return Ok(());
                    }
                }
                return slot.handler.call(ctx).await;
            }
            if let Some(fallback) = &self.fallback {
                return fallback.call(ctx).await;
            }
            return Ok(());
        }

        // Plain-text triggers.
        let lower = text.to_lowercase();
        for slot in &self.text_commands {
            let hit = match slot.matcher {
                TextMatch::Exact => lower == slot.pattern,
                TextMatch::Prefix => lower.starts_with(&slot.pattern),
                TextMatch::Contains => lower.contains(&slot.pattern),
            };
            if hit {
                return slot.handler.call(ctx).await;
            }
        }

        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::FloodWindow;
    use std::time::{Duration, Instant};

    #[test]
    fn under_the_threshold_stays_quiet() {
        let w = FloodWindow::new(5, Duration::from_secs(60));
        let now = Instant::now();
        for _ in 0..5 {
            assert_eq!(w.hit(now), None);
        }
    }

    #[test]
    fn crossing_the_threshold_fires_with_the_count() {
        let w = FloodWindow::new(3, Duration::from_secs(60));
        let now = Instant::now();
        for _ in 0..3 {
            assert_eq!(w.hit(now), None);
        }
        assert_eq!(w.hit(now), Some(4));
    }

    #[test]
    fn cooldown_suppresses_repeat_alerts() {
        let w = FloodWindow::new(2, Duration::from_secs(60));
        let now = Instant::now();
        w.hit(now);
        w.hit(now);
        assert_eq!(w.hit(now), Some(3));
        // Still flooding, but within cooldown: quiet.
        assert_eq!(w.hit(now), None);
        assert_eq!(w.hit(now), None);
    }

    #[test]
    fn cooldown_expiry_allows_another_alert() {
        let w = FloodWindow::new(1, Duration::from_secs(10));
        let now = Instant::now();
        w.hit(now);
        assert_eq!(w.hit(now), Some(2));
        assert_eq!(w.hit(now), None);
        // 10s later: same window (60s), still over threshold, cooldown over.
        let later = now + Duration::from_secs(10);
        assert_eq!(w.hit(later), Some(4));
    }

    #[test]
    fn a_new_window_resets_the_count() {
        let w = FloodWindow::new(2, Duration::from_secs(0));
        let now = Instant::now();
        w.hit(now);
        w.hit(now);
        assert_eq!(w.hit(now), Some(3));
        // Next minute: counting starts over.
        let next = now + Duration::from_secs(60);
        assert_eq!(w.hit(next), None);
        assert_eq!(w.hit(next), None);
        assert_eq!(w.hit(next), Some(3));
    }
}