Reduce emissions by 10% every year (#108)

* deprecate top balance

* stub dynamic emissions impl

* impl 90% curve

* scaffold emissions rate function

* emissions curve

* implement new supply curve

* remove comments

* update comment

* bump version

* test reset

* add tests for emissions reduction

* test

* fix test

* bump version

api/src/consts.rs

@@ -42,16 +42,6 @@ pub const EPOCH_DURATION: i64 = ONE_MINUTE * EPOCH_MINUTES;
 /// The maximum token supply (5 million).
 pub const MAX_SUPPLY: u64 = ONE_ORE * 5_000_000;
 
-/// The target quantity of ORE to be mined per epoch.
-pub const TARGET_EPOCH_REWARDS: u64 = ONE_ORE * EPOCH_MINUTES as u64;
-
-/// The maximum quantity of ORE that can be mined per epoch.
-/// Inflation target ≈ 1 ORE / min
-pub const MAX_EPOCH_REWARDS: u64 = TARGET_EPOCH_REWARDS * BUS_COUNT as u64;
-
-/// The quantity of ORE each bus is allowed to issue per epoch.
-pub const BUS_EPOCH_REWARDS: u64 = MAX_EPOCH_REWARDS / BUS_COUNT as u64;
-
 /// The number of bus accounts, for parallelizing mine operations.
 pub const BUS_COUNT: usize = 8;
 
@@ -59,11 +49,6 @@ pub const BUS_COUNT: usize = 8;
 /// than a factor of this constant from one epoch to the next.
 pub const SMOOTHING_FACTOR: u64 = 2;
 
-// Assert MAX_EPOCH_REWARDS is evenly divisible by BUS_COUNT.
-static_assertions::const_assert!(
-    (MAX_EPOCH_REWARDS / BUS_COUNT as u64) * BUS_COUNT as u64 == MAX_EPOCH_REWARDS
-);
-
 /// The seed of the bus account PDA.
 pub const BUS: &[u8] = b"bus";
 

api/src/state/bus.rs

@@ -18,6 +18,7 @@ pub struct Bus {
     pub theoretical_rewards: u64,
 
     /// The largest known stake balance seen by the bus this epoch.
+    #[deprecated(since = "2.8.0", note = "Top balance is no longer tracked or used")]
     pub top_balance: u64,
 }
 

api/src/state/config.rs

@@ -15,8 +15,8 @@ pub struct Config {
     /// The minimum accepted difficulty.
     pub min_difficulty: u64,
 
-    /// Buffer for possible future use.
-    pub _buffer: [u8; 8],
+    /// The target emissions rate in ORE/min.
+    pub target_emmissions_rate: u64,
 }
 
 account!(OreAccount, Config);