LQT: implement budget appropriation function

crates/core/component/funding/src/component/liquidity_tournament/bank.rs

@@ -1,8 +1,43 @@
 use async_trait::async_trait;
 use cnidarium::StateWrite;
+use penumbra_sdk_asset::{Value, STAKING_TOKEN_ASSET_ID};
+use penumbra_sdk_community_pool::{StateReadExt as _, StateWriteExt as _};
 use penumbra_sdk_dex::lp::position;
+use penumbra_sdk_distributions::component::{StateReadExt as _, StateWriteExt as _};
 use penumbra_sdk_keys::Address;
-use penumbra_sdk_num::fixpoint::U128x128;
+use penumbra_sdk_num::{fixpoint::U128x128, Amount};
+
+/// Move a fraction of the budget, up to the entire budget, from the community pool.
+///
+/// This will return the amount pulled (in terms of the staking token).
+#[allow(dead_code)]
+async fn appropriate_budget(
+    mut state: impl StateWrite,
+    fraction: U128x128,
+) -> anyhow::Result<Amount> {
+    // For our purposes, no budget is the same as an explicit budget of 0.
+    let budget = state
+        .get_lqt_reward_issuance_for_epoch()
+        .unwrap_or_default();
+    // IMO this method should have just expected to begin with.
+    let portion = fraction
+        .apply_to_amount(&budget)
+        .expect(&format!("failed to apply {fraction} to {budget:?}"));
+    // This fraction may be > 1.0, in which case we need to not over-appropriate
+    let (new_budget, portion) = match budget.checked_sub(&portion) {
+        Some(new_budget) => (new_budget, portion),
+        // portion > budget, so eat the whole budget.
+        None => (0u64.into(), budget),
+    };
+    state.set_lqt_reward_issuance_for_epoch(new_budget);
+    state
+        .community_pool_withdraw(Value {
+            asset_id: *STAKING_TOKEN_ASSET_ID,
+            amount: portion,
+        })
+        .await?;
+    Ok(portion)
+}
 
 #[allow(dead_code)]
 #[async_trait]