foukoapi 0.1.2-alpha.2

//! Batteries-included economy: XP, levels, coins, cooldowns and a
//! leaderboard, all layered on top of [`Accounts`] so linked accounts
//! share one wallet.
//!
//! The design goal is "drop it in and it just works". Give [`Economy`]
//! the same [`Accounts`] your bot already uses and you get:
//!
//! - [`Economy::add_xp`] / [`Economy::wallet`] - XP that auto-mints coins,
//!   with a level curve.
//! - [`Economy::add_coins`] / [`Economy::transfer`] - a spendable balance.
//! - [`Economy::cooldown_remaining`] / [`Economy::touch_cooldown`] - rate
//!   limits for `/daily`, `/gamble`, and friends.
//! - [`Economy::leaderboard`] / [`Economy::rank_of`] - rankings backed by
//!   a player index the store maintains for you.
//! - [`Economy::title`] / [`Economy::color`] - small cosmetic slots bots
//!   can sell in a shop.
//!
//! Everything resolves through a player's *primary* identity, so a user
//! who linked Telegram and Discord sees the same XP and coins on both.

use crate::{accounts::Accounts, platform::PlatformKind, storage::Storage, Result};
use std::sync::Arc;

/// Namespaced keys so the economy never trips over account-linking data.
const XP_PREFIX: &str = "foukoapi:econ:xp:";
const COINS_PREFIX: &str = "foukoapi:econ:coins:";
const TITLE_PREFIX: &str = "foukoapi:econ:title:";
const NAME_PREFIX: &str = "foukoapi:econ:name:";
const COLOR_PREFIX: &str = "foukoapi:econ:color:";
const COOLDOWN_PREFIX: &str = "foukoapi:econ:cd:";
const ACH_PREFIX: &str = "foukoapi:econ:ach:";

/// XP-per-coin conversion used by [`Economy::add_xp`].
pub const XP_PER_COIN: u64 = 10;

/// An economy handle sharing storage with [`Accounts`].
///
/// Clone it freely - it's just a few `Arc`s under the hood.
#[derive(Clone)]
pub struct Economy {
    storage: Arc<dyn Storage>,
    accounts: Accounts,
    /// Serialises every read-modify-write against the store so parallel
    /// grants and transfers can't lose updates or double-spend. Shared by
    /// all clones of this handle.
    lock: Arc<tokio::sync::Mutex<()>>,
}

/// What one [`Economy::add_xp`] call produced.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct XpGain {
    /// New XP total after the grant.
    pub xp: u64,
    /// Coins minted by the boundaries this grant crossed.
    pub coins_minted: u64,
}

/// A player's resolved balances.
#[derive(Debug, Clone)]
pub struct Wallet {
    /// Lifetime experience points.
    pub xp: u64,
    /// Spendable coins.
    pub coins: u64,
    /// Level derived from `xp` via [`Economy::level_for`].
    pub level: u32,
}

/// What [`Economy::leaderboard`] ranks on.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Metric {
    /// Rank by lifetime XP.
    Xp,
    /// Rank by current coin balance.
    Coins,
}

/// One row of a leaderboard.
#[derive(Debug, Clone)]
pub struct RankedPlayer {
    /// The player's primary identity, `"platform:id"`.
    pub primary: String,
    /// The metric value this player was ranked on.
    pub value: u64,
    /// Zero-based position in the ranking.
    pub position: usize,
}

impl Economy {
    /// Build an economy that shares [`Accounts`]' storage. This is the
    /// one you want: balances follow the account link automatically.
    pub fn new(accounts: Accounts) -> Self {
        Self {
            storage: accounts.storage_ref().clone(),
            accounts,
            lock: Arc::new(tokio::sync::Mutex::new(())),
        }
    }

    /// Resolve a user to the primary identity their balances live under.
    ///
    /// If this identity was linked to another account after it had already
    /// earned something, its old balances sit under the pre-link key. We
    /// fold those into the primary on sight, so linking never leaves a
    /// ghost entry on the leaderboard.
    async fn primary(&self, platform: PlatformKind, user_id: &str) -> String {
        let me = format!("{platform}:{user_id}");
        let primary = self
            .accounts
            .primary_for(platform, user_id)
            .await
            .unwrap_or_else(|_| me.clone());
        if primary != me {
            if let Err(e) = self.merge_identity(&me, &primary).await {
                tracing::error!(from = %me, into = %primary, error = %e, "economy: identity merge failed");
            }
        }
        primary
    }

    /// Fold everything stored under `from` into `into`: XP and coins are
    /// summed, achievements unioned, cosmetics and the display name kept
    /// from `into` when both exist. The `from` keys are deleted, so this
    /// runs at most once per orphaned identity. Each write into `into`
    /// happens before the matching `from` delete, so a failure mid-way
    /// never drops a balance - at worst the merge just runs again later.
    async fn merge_identity(&self, from: &str, into: &str) -> Result<()> {
        let _guard = self.lock.lock().await;
        let from_xp = self.read(&format!("{XP_PREFIX}{from}")).await;
        let from_coins = self.read(&format!("{COINS_PREFIX}{from}")).await;
        if from_xp == 0 && from_coins == 0 {
            return Ok(()); // nothing to fold; skip the write churn
        }
        tracing::info!(from = %from, into = %into, "economy: merging linked identity");

        if from_xp > 0 {
            let into_key = format!("{XP_PREFIX}{into}");
            let total = self.read(&into_key).await.saturating_add(from_xp);
            self.storage.set(&into_key, &total.to_string()).await?;
            self.storage.del(&format!("{XP_PREFIX}{from}")).await?;
        }
        if from_coins > 0 {
            let into_key = format!("{COINS_PREFIX}{into}");
            let total = self.read(&into_key).await.saturating_add(from_coins);
            self.storage.set(&into_key, &total.to_string()).await?;
            self.storage.del(&format!("{COINS_PREFIX}{from}")).await?;
        }
        // Cosmetics and name: only fill gaps, the primary's own win.
        for prefix in [TITLE_PREFIX, COLOR_PREFIX, NAME_PREFIX] {
            let from_key = format!("{prefix}{from}");
            if let Ok(Some(v)) = self.storage.get(&from_key).await {
                let into_key = format!("{prefix}{into}");
                if matches!(self.storage.get(&into_key).await, Ok(None)) {
                    self.storage.set(&into_key, &v).await?;
                }
                self.storage.del(&from_key).await?;
            }
        }
        // Achievements: union of both sides.
        let from_key = format!("{ACH_PREFIX}{from}");
        if let Ok(Some(theirs)) = self.storage.get(&from_key).await {
            let into_key = format!("{ACH_PREFIX}{into}");
            let mut merged: Vec<String> = self
                .storage
                .get(&into_key)
                .await
                .ok()
                .flatten()
                .map(|blob| blob.lines().map(str::to_owned).collect())
                .unwrap_or_default();
            for a in theirs.lines() {
                if !a.is_empty() && !merged.iter().any(|m| m == a) {
                    merged.push(a.to_owned());
                }
            }
            self.storage.set(&into_key, &merged.join("\n")).await?;
            self.storage.del(&from_key).await?;
        }
        Ok(())
    }

    // -- reads ---------------------------------------------------------------

    /// Fetch a player's full wallet.
    pub async fn wallet(&self, platform: PlatformKind, user_id: &str) -> Wallet {
        let primary = self.primary(platform, user_id).await;
        self.wallet_of(&primary).await
    }

    /// Fetch a wallet straight from a primary identity (as returned by the
    /// leaderboard).
    pub async fn wallet_of(&self, primary: &str) -> Wallet {
        let xp = self.read(&format!("{XP_PREFIX}{primary}")).await;
        let coins = self.read(&format!("{COINS_PREFIX}{primary}")).await;
        Wallet {
            xp,
            coins,
            level: Self::level_for(xp),
        }
    }

    /// Current coin balance.
    pub async fn coins(&self, platform: PlatformKind, user_id: &str) -> u64 {
        let primary = self.primary(platform, user_id).await;
        self.read(&format!("{COINS_PREFIX}{primary}")).await
    }

    // -- writes --------------------------------------------------------------

    /// Grant XP and mint a coin for every [`XP_PER_COIN`] points earned.
    /// A single large grant pays out every coin boundary it crosses, not
    /// just one. Coins are credited before the XP write so a failed XP
    /// write can't strand a crossed boundary.
    pub async fn add_xp(
        &self,
        platform: PlatformKind,
        user_id: &str,
        amount: u64,
    ) -> Result<XpGain> {
        let primary = self.primary(platform, user_id).await;
        let _guard = self.lock.lock().await;
        let key = format!("{XP_PREFIX}{primary}");
        let before = self.read(&key).await;
        if amount == 0 {
            return Ok(XpGain {
                xp: before,
                coins_minted: 0,
            });
        }
        let after = before.saturating_add(amount);
        let minted = (after / XP_PER_COIN).saturating_sub(before / XP_PER_COIN);
        if minted > 0 {
            self.add_coins_locked(&primary, minted as i64).await?;
        }
        self.storage.set(&key, &after.to_string()).await?;
        Ok(XpGain {
            xp: after,
            coins_minted: minted,
        })
    }

    /// Add coins (negative to subtract, clamped at zero). Returns the new
    /// balance.
    pub async fn add_coins(
        &self,
        platform: PlatformKind,
        user_id: &str,
        delta: i64,
    ) -> Result<u64> {
        let primary = self.primary(platform, user_id).await;
        let _guard = self.lock.lock().await;
        self.add_coins_locked(&primary, delta).await
    }

    /// Move `amount` coins from one user to another, both resolved through
    /// their primaries. Fails if the sender is short. Returns the sender's
    /// remaining balance on success.
    pub async fn transfer(
        &self,
        from: (PlatformKind, &str),
        to: (PlatformKind, &str),
        amount: u64,
    ) -> Result<u64> {
        let sender = self.primary(from.0, from.1).await;
        let recipient = self.primary(to.0, to.1).await;
        if sender == recipient {
            return Err(crate::Error::Other("can't send coins to yourself".into()));
        }
        // Check, debit and credit under one guard so two concurrent
        // transfers can't both pass the balance check.
        let _guard = self.lock.lock().await;
        let balance = self.read(&format!("{COINS_PREFIX}{sender}")).await;
        if balance < amount {
            return Err(crate::Error::Other("not enough coins".into()));
        }
        let remaining = self.add_coins_locked(&sender, -(amount as i64)).await?;
        if let Err(e) = self.add_coins_locked(&recipient, amount as i64).await {
            // Credit failed: put the debited coins back, best effort.
            if let Err(refund_err) = self.add_coins_locked(&sender, amount as i64).await {
                tracing::error!(
                    sender = %sender,
                    amount,
                    error = %refund_err,
                    "transfer refund failed - coins lost"
                );
            }
            return Err(e);
        }
        Ok(remaining)
    }

    /// Read-modify-write on a coin balance. Caller must hold `self.lock`.
    async fn add_coins_locked(&self, primary: &str, delta: i64) -> Result<u64> {
        let key = format!("{COINS_PREFIX}{primary}");
        let current = self.read(&key).await as i64;
        let next = (current + delta).max(0) as u64;
        self.storage.set(&key, &next.to_string()).await?;
        Ok(next)
    }

    // -- levels --------------------------------------------------------------

    /// Level for an XP total. Reaching level `L` costs `L*(L+1)*10` XP,
    /// giving thresholds 20, 60, 120, 200, ...
    pub fn level_for(xp: u64) -> u32 {
        let mut level: u32 = 0;
        loop {
            let next = (level as u64 + 1) * (level as u64 + 2) * 10;
            if xp < next || level > 1000 {
                return level;
            }
            level += 1;
        }
    }

    /// The XP band `[lower, upper)` bracketing `level`, handy for progress
    /// bars. A player at `level` has `xp` somewhere in this half-open range.
    pub fn level_bounds(level: u32) -> (u64, u64) {
        let l = level as u64;
        let lower = l * (l + 1) * 10;
        let upper = (l + 1) * (l + 2) * 10;
        (lower, upper)
    }

    // -- cooldowns -----------------------------------------------------------

    /// Seconds until `action` is usable again for this user; `0` when
    /// it's ready now.
    pub async fn cooldown_remaining(
        &self,
        platform: PlatformKind,
        user_id: &str,
        action: &str,
        window_secs: i64,
    ) -> i64 {
        let primary = self.primary(platform, user_id).await;
        let last = self
            .read(&format!("{COOLDOWN_PREFIX}{action}:{primary}"))
            .await as i64;
        (window_secs - (now() - last)).max(0)
    }

    /// Start `action`'s cooldown window from now.
    pub async fn touch_cooldown(
        &self,
        platform: PlatformKind,
        user_id: &str,
        action: &str,
    ) -> Result<()> {
        let primary = self.primary(platform, user_id).await;
        self.storage
            .set(
                &format!("{COOLDOWN_PREFIX}{action}:{primary}"),
                &now().to_string(),
            )
            .await
    }

    // -- cosmetics -----------------------------------------------------------

    /// The equipped title, if the player has one.
    pub async fn title(&self, platform: PlatformKind, user_id: &str) -> Option<String> {
        let primary = self.primary(platform, user_id).await;
        self.storage
            .get(&format!("{TITLE_PREFIX}{primary}"))
            .await
            .ok()
            .flatten()
            .filter(|s| !s.is_empty())
    }

    /// Equip a title (empty string clears it).
    pub async fn set_title(
        &self,
        platform: PlatformKind,
        user_id: &str,
        title: &str,
    ) -> Result<()> {
        let primary = self.primary(platform, user_id).await;
        self.storage
            .set(&format!("{TITLE_PREFIX}{primary}"), title)
            .await
    }

    /// Remember a user's latest display name, keyed by primary identity, so
    /// leaderboards can show names instead of raw ids. Called opportunisti-
    /// cally (e.g. from a message hook).
    pub async fn set_display_name(
        &self,
        platform: PlatformKind,
        user_id: &str,
        name: &str,
    ) -> Result<()> {
        let primary = self.primary(platform, user_id).await;
        self.storage
            .set(&format!("{NAME_PREFIX}{primary}"), name)
            .await
    }

    /// The stored display name for a primary identity, if we've seen one.
    pub async fn display_name_of(&self, primary: &str) -> Option<String> {
        self.storage
            .get(&format!("{NAME_PREFIX}{primary}"))
            .await
            .ok()
            .flatten()
            .filter(|s| !s.is_empty())
    }

    /// The custom profile colour, if bought.
    pub async fn color(&self, platform: PlatformKind, user_id: &str) -> Option<u32> {
        let primary = self.primary(platform, user_id).await;
        self.storage
            .get(&format!("{COLOR_PREFIX}{primary}"))
            .await
            .ok()
            .flatten()
            .and_then(|s| u32::from_str_radix(s.trim_start_matches('#'), 16).ok())
    }

    /// Store a custom profile colour.
    pub async fn set_color(&self, platform: PlatformKind, user_id: &str, rgb: u32) -> Result<()> {
        let primary = self.primary(platform, user_id).await;
        self.storage
            .set(&format!("{COLOR_PREFIX}{primary}"), &format!("{rgb:06X}"))
            .await
    }

    // -- achievements --------------------------------------------------------

    /// Grant an achievement by id. Returns `true` if it was newly awarded,
    /// `false` if the user already had it (so a caller can announce it only
    /// the first time). Ids are opaque strings the bot defines; names and
    /// descriptions live on the bot side so they stay fully customisable.
    pub async fn grant_achievement(
        &self,
        platform: PlatformKind,
        user_id: &str,
        id: &str,
    ) -> Result<bool> {
        let primary = self.primary(platform, user_id).await;
        let _guard = self.lock.lock().await;
        let key = format!("{ACH_PREFIX}{primary}");
        let mut owned = self.read_list(&key).await;
        if owned.iter().any(|a| a == id) {
            return Ok(false);
        }
        owned.push(id.to_owned());
        self.storage.set(&key, &owned.join("\n")).await?;
        Ok(true)
    }

    /// Whether the user already holds `id`.
    pub async fn has_achievement(&self, platform: PlatformKind, user_id: &str, id: &str) -> bool {
        let primary = self.primary(platform, user_id).await;
        self.read_list(&format!("{ACH_PREFIX}{primary}"))
            .await
            .iter()
            .any(|a| a == id)
    }

    /// Every achievement id the user has earned, in the order granted.
    pub async fn achievements(&self, platform: PlatformKind, user_id: &str) -> Vec<String> {
        let primary = self.primary(platform, user_id).await;
        self.read_list(&format!("{ACH_PREFIX}{primary}")).await
    }

    async fn read_list(&self, key: &str) -> Vec<String> {
        self.storage
            .get(key)
            .await
            .ok()
            .flatten()
            .map(|blob| {
                blob.lines()
                    .filter(|s| !s.is_empty())
                    .map(str::to_owned)
                    .collect()
            })
            .unwrap_or_default()
    }

    // -- leaderboard ---------------------------------------------------------

    /// Top `limit` players by `metric`, highest first.
    pub async fn leaderboard(&self, metric: Metric, limit: usize) -> Vec<RankedPlayer> {
        let mut ranked = self.ranked_all(metric).await;
        ranked.truncate(limit);
        ranked
    }

    /// A single user's rank (and value) for `metric`, or `None` if they've
    /// never earned anything.
    pub async fn rank_of(
        &self,
        platform: PlatformKind,
        user_id: &str,
        metric: Metric,
    ) -> Option<RankedPlayer> {
        let primary = self.primary(platform, user_id).await;
        self.ranked_all(metric)
            .await
            .into_iter()
            .find(|r| r.primary == primary)
    }

    /// How many players the economy has seen (anyone with XP or coins).
    pub async fn player_count(&self) -> usize {
        let mut seen: std::collections::HashSet<String> = std::collections::HashSet::new();
        for (key, _) in self
            .storage
            .list_prefix(XP_PREFIX)
            .await
            .unwrap_or_default()
        {
            if let Some(p) = key.strip_prefix(XP_PREFIX) {
                seen.insert(p.to_owned());
            }
        }
        for (key, _) in self
            .storage
            .list_prefix(COINS_PREFIX)
            .await
            .unwrap_or_default()
        {
            if let Some(p) = key.strip_prefix(COINS_PREFIX) {
                seen.insert(p.to_owned());
            }
        }
        seen.len()
    }

    async fn ranked_all(&self, metric: Metric) -> Vec<RankedPlayer> {
        let prefix = match metric {
            Metric::Xp => XP_PREFIX,
            Metric::Coins => COINS_PREFIX,
        };
        // Scan the store for every "<prefix><primary>" key at once instead
        // of keeping a hand-maintained index.
        let mut rows: Vec<(String, u64)> = self
            .storage
            .list_prefix(prefix)
            .await
            .unwrap_or_default()
            .into_iter()
            .filter_map(|(key, value)| {
                let primary = key.strip_prefix(prefix)?.to_owned();
                let value = value.parse().unwrap_or(0);
                Some((primary, value))
            })
            .collect();
        rows.sort_by_key(|row| std::cmp::Reverse(row.1));
        rows.into_iter()
            .enumerate()
            .map(|(position, (primary, value))| RankedPlayer {
                primary,
                value,
                position,
            })
            .collect()
    }

    async fn read(&self, key: &str) -> u64 {
        self.storage
            .get(key)
            .await
            .ok()
            .flatten()
            .and_then(|s| s.parse().ok())
            .unwrap_or(0)
    }
}

fn now() -> i64 {
    std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .map(|d| d.as_secs() as i64)
        .unwrap_or(0)
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{storage::MemoryStorage, PlatformKind};

    fn econ() -> Economy {
        Economy::new(Accounts::new(MemoryStorage::new()))
    }

    #[test]
    fn level_curve() {
        assert_eq!(Economy::level_for(0), 0);
        assert_eq!(Economy::level_for(19), 0);
        assert_eq!(Economy::level_for(20), 1);
        assert_eq!(Economy::level_for(60), 2);
        assert_eq!(Economy::level_for(119), 2);
        assert_eq!(Economy::level_for(120), 3);
    }

    #[test]
    fn level_bounds_bracket_the_xp() {
        for xp in [0u64, 5, 25, 61, 200, 999] {
            let level = Economy::level_for(xp);
            let (lower, upper) = Economy::level_bounds(level);
            assert!(lower <= xp, "lower {lower} should be <= xp {xp}");
            assert!(xp < upper, "xp {xp} should be < upper {upper}");
        }
    }

    #[tokio::test]
    async fn xp_mints_coins_across_boundaries() {
        let e = econ();
        let d = PlatformKind::Discord;
        // 25 XP crosses two 10-XP boundaries, so two coins.
        let gain = e.add_xp(d, "u1", 25).await.unwrap();
        assert_eq!(gain.xp, 25);
        assert_eq!(gain.coins_minted, 2);
        let w = e.wallet(d, "u1").await;
        assert_eq!(w.xp, 25);
        assert_eq!(w.coins, 2);
    }

    #[tokio::test]
    async fn concurrent_grants_do_not_lose_updates() {
        let e = econ();
        let d = PlatformKind::Discord;
        let mut handles = Vec::new();
        for _ in 0..20 {
            let e = e.clone();
            handles.push(tokio::spawn(async move {
                e.add_xp(d, "u", 5).await.unwrap();
            }));
        }
        for h in handles {
            h.await.unwrap();
        }
        let w = e.wallet(d, "u").await;
        assert_eq!(w.xp, 100);
        assert_eq!(w.coins, 10);
    }

    #[tokio::test]
    async fn concurrent_transfers_cannot_overdraw() {
        let e = econ();
        let d = PlatformKind::Discord;
        e.add_coins(d, "rich", 100).await.unwrap();
        let a = {
            let e = e.clone();
            tokio::spawn(async move { e.transfer((d, "rich"), (d, "p1"), 100).await })
        };
        let b = {
            let e = e.clone();
            tokio::spawn(async move { e.transfer((d, "rich"), (d, "p2"), 100).await })
        };
        let (ra, rb) = (a.await.unwrap(), b.await.unwrap());
        // Exactly one transfer may succeed with a 100-coin balance.
        assert!(ra.is_ok() != rb.is_ok());
        let total = e.coins(d, "rich").await + e.coins(d, "p1").await + e.coins(d, "p2").await;
        assert_eq!(total, 100);
    }

    #[tokio::test]
    async fn transfer_moves_coins_and_refuses_overdraft() {
        let e = econ();
        let d = PlatformKind::Discord;
        e.add_coins(d, "rich", 100).await.unwrap();
        let left = e.transfer((d, "rich"), (d, "poor"), 30).await.unwrap();
        assert_eq!(left, 70);
        assert_eq!(e.coins(d, "poor").await, 30);
        assert!(e.transfer((d, "poor"), (d, "rich"), 999).await.is_err());
    }

    #[tokio::test]
    async fn leaderboard_orders_by_value() {
        let e = econ();
        let d = PlatformKind::Discord;
        e.add_xp(d, "a", 100).await.unwrap();
        e.add_xp(d, "b", 300).await.unwrap();
        e.add_xp(d, "c", 200).await.unwrap();
        let top = e.leaderboard(Metric::Xp, 10).await;
        assert_eq!(top[0].primary, "discord:b");
        assert_eq!(top[1].primary, "discord:c");
        assert_eq!(top[2].primary, "discord:a");
        assert_eq!(top[0].position, 0);
    }

    #[tokio::test]
    async fn rank_of_reports_position() {
        let e = econ();
        let d = PlatformKind::Discord;
        e.add_xp(d, "a", 100).await.unwrap();
        e.add_xp(d, "b", 300).await.unwrap();
        let rank = e.rank_of(d, "a", Metric::Xp).await.unwrap();
        assert_eq!(rank.position, 1); // behind "b"
        assert!(e.rank_of(d, "ghost", Metric::Xp).await.is_none());
    }

    #[tokio::test]
    async fn linking_merges_previously_earned_balances() {
        // A user earns XP on Discord, then links it to their Telegram
        // account with Telegram as primary. The old Discord-keyed XP must
        // fold into the primary instead of haunting the leaderboard.
        let accounts = Accounts::new(crate::storage::MemoryStorage::new());
        let e = Economy::new(accounts.clone());
        let d = PlatformKind::Discord;
        let t = PlatformKind::Telegram;

        e.add_xp(d, "42", 50).await.unwrap();
        assert_eq!(e.wallet_of("discord:42").await.xp, 50);

        // Link: telegram starts it, discord redeems, then telegram is
        // chosen as primary for both sides.
        let code = accounts.start_link(t, "777").await.unwrap();
        accounts.redeem_link(&code, d, "42").await.unwrap();
        accounts.set_primary(d, "42", "telegram:777").await.unwrap();

        // Any economy touch through the Discord identity now folds the
        // old balance into the primary.
        e.add_xp(d, "42", 1).await.unwrap();
        let w = e.wallet(t, "777").await;
        assert_eq!(w.xp, 51);
        assert_eq!(e.wallet_of("discord:42").await.xp, 0);

        // And the leaderboard has a single row for this person.
        let top = e.leaderboard(Metric::Xp, 10).await;
        assert_eq!(top.len(), 1);
        assert_eq!(top[0].primary, "telegram:777");
    }

    #[tokio::test]
    async fn cooldown_tracks_a_window() {
        let e = econ();
        let d = PlatformKind::Discord;
        // Nothing stamped yet: ready immediately.
        assert_eq!(e.cooldown_remaining(d, "u", "daily", 60).await, 0);
        e.touch_cooldown(d, "u", "daily").await.unwrap();
        // Right after touching, a 60s window should still be ticking.
        assert!(e.cooldown_remaining(d, "u", "daily", 60).await > 0);
        // A zero-length window is always ready.
        assert_eq!(e.cooldown_remaining(d, "u", "daily", 0).await, 0);
    }

    #[tokio::test]
    async fn cosmetics_persist() {
        let e = econ();
        let d = PlatformKind::Discord;
        assert!(e.title(d, "u").await.is_none());
        e.set_title(d, "u", "Legend").await.unwrap();
        assert_eq!(e.title(d, "u").await.as_deref(), Some("Legend"));
        e.set_color(d, "u", 0x00C2A8).await.unwrap();
        assert_eq!(e.color(d, "u").await, Some(0x00C2A8));
    }

    #[tokio::test]
    async fn achievements_grant_once() {
        let e = econ();
        let d = PlatformKind::Discord;
        assert!(!e.has_achievement(d, "u", "first_daily").await);
        assert!(e.grant_achievement(d, "u", "first_daily").await.unwrap()); // newly granted
        assert!(!e.grant_achievement(d, "u", "first_daily").await.unwrap()); // already had it
        assert!(e.has_achievement(d, "u", "first_daily").await);
        e.grant_achievement(d, "u", "high_roller").await.unwrap();
        assert_eq!(
            e.achievements(d, "u").await,
            vec!["first_daily".to_owned(), "high_roller".to_owned()]
        );
    }
}