feat(data_structures): adapt stakes tracker to latest specs

fix witnet#2398

data_structures/Cargo.toml

@@ -51,3 +51,7 @@ rand_distr = "0.4.3"
 [[bench]]
 name = "sort_active_identities"
 harness = false
+
+[[bench]]
+name = "staking"
+harness = false

data_structures/benches/staking.rs

@@ -0,0 +1,85 @@
+#[macro_use]
+extern crate bencher;
+use bencher::Bencher;
+use rand::Rng;
+use witnet_data_structures::staking::prelude::*;
+
+fn populate(b: &mut Bencher) {
+    let mut stakes = Stakes::<String, u64, u64, u64>::default();
+    let mut i = 1;
+
+    b.iter(|| {
+        let address = format!("{i}");
+        let coins = i;
+        let epoch = i;
+        stakes.add_stake(address, coins, epoch).unwrap();
+
+        i += 1;
+    });
+}
+
+fn rank(b: &mut Bencher) {
+    let mut stakes = Stakes::<String, u64, u64, u64>::default();
+    let mut i = 1;
+
+    let stakers = 100_000;
+    let rf = 10;
+
+    let mut rng = rand::thread_rng();
+
+    loop {
+        let coins = i;
+        let epoch = i;
+        let address = format!("{}", rng.gen::<u64>());
+
+        stakes.add_stake(address, coins, epoch).unwrap();
+
+        i += 1;
+
+        if i == stakers {
+            break;
+        }
+    }
+
+    b.iter(|| {
+        let rank = stakes.rank(Capability::Mining, i);
+        let mut top = rank.take((stakers / rf) as usize);
+        let _first = top.next();
+        let _last = top.last();
+
+        i += 1;
+    })
+}
+
+fn query_power(b: &mut Bencher) {
+    let mut stakes = Stakes::<String, u64, u64, u64>::default();
+    let mut i = 1;
+
+    let stakers = 100_000;
+
+    loop {
+        let coins = i;
+        let epoch = i;
+        let address = format!("{i}");
+
+        stakes.add_stake(address, coins, epoch).unwrap();
+
+        i += 1;
+
+        if i == stakers {
+            break;
+        }
+    }
+
+    i = 1;
+
+    b.iter(|| {
+        let address = format!("{i}");
+        let _power = stakes.query_power(&address, Capability::Mining, i);
+
+        i += 1;
+    })
+}
+
+benchmark_main!(benches);
+benchmark_group!(benches, populate, rank, query_power);

data_structures/src/lib.rs

@@ -72,6 +72,9 @@ mod serialization_helpers;
 /// Provides convenient constants, structs and methods for handling values denominated in Wit.
 pub mod wit;
 
+/// Provides support for segmented protocol capabilities.
+pub mod capabilities;
+
 lazy_static! {
     /// Environment in which we are running: mainnet or testnet.
     /// This is used for Bech32 serialization.

data_structures/src/staking/aux.rs

@@ -0,0 +1,33 @@
+use std::rc::Rc;
+use std::sync::RwLock;
+
+use super::prelude::*;
+
+/// Type alias for a reference-counted and read-write-locked instance of `Stake`.
+pub type SyncStake<Address, Coins, Epoch, Power> = Rc<RwLock<Stake<Address, Coins, Epoch, Power>>>;
+
+/// Couples an amount of coins and an address together. This is to be used in `Stakes` as the index
+/// of the `by_coins` index..
+#[derive(Eq, Ord, PartialEq, PartialOrd)]
+pub struct CoinsAndAddress<Coins, Address> {
+    /// An amount of coins.
+    pub coins: Coins,
+    /// The address of a staker.
+    pub address: Address,
+}
+
+/// Allows telling the `census` method in `Stakes` to source addresses from its internal `by_coins`
+/// following different strategies.
+#[repr(u8)]
+#[derive(Clone, Copy, Debug)]
+pub enum CensusStrategy {
+    /// Retrieve all addresses, ordered by decreasing power.
+    All = 0,
+    /// Retrieve every Nth address, ordered by decreasing power.
+    StepBy(usize) = 1,
+    /// Retrieve the most powerful N addresses, ordered by decreasing power.
+    Take(usize) = 2,
+    /// Retrieve a total of N addresses, evenly distributed from the index, ordered by decreasing
+    /// power.
+    Evenly(usize) = 3,
+}

data_structures/src/staking/constants.rs

@@ -0,0 +1,2 @@
+/// A minimum stakeable amount needs to exist to prevent spamming of the tracker.
+pub const MINIMUM_STAKEABLE_AMOUNT_WITS: u64 = 100;

data_structures/src/staking/errors.rs

@@ -0,0 +1,41 @@
+use std::sync::PoisonError;
+
+/// All errors related to the staking functionality.
+#[derive(Debug, PartialEq)]
+pub enum StakesError<Address, Coins, Epoch> {
+    /// The amount of coins being staked or the amount that remains after unstaking is below the
+    /// minimum stakeable amount.
+    AmountIsBelowMinimum {
+        /// The number of coins being staked or remaining after staking.
+        amount: Coins,
+        /// The minimum stakeable amount.
+        minimum: Coins,
+    },
+    /// Tried to query `Stakes` for information that belongs to the past.
+    EpochInThePast {
+        ///  The Epoch being referred.
+        epoch: Epoch,
+        /// The latest Epoch.
+        latest: Epoch,
+    },
+    /// An operation thrown an Epoch value that overflows.
+    EpochOverflow {
+        /// The computed Epoch value.
+        computed: u64,
+        /// The maximum Epoch.
+        maximum: Epoch,
+    },
+    /// Tried to query `Stakes` for the address of a staker that is not registered in `Stakes`.
+    IdentityNotFound {
+        /// The unknown address.
+        identity: Address,
+    },
+    /// Tried to obtain a lock on a write-locked piece of data that is already locked.
+    PoisonedLock,
+}
+
+impl<T, Address, Coins, Epoch> From<PoisonError<T>> for StakesError<Address, Coins, Epoch> {
+    fn from(_value: PoisonError<T>) -> Self {
+        StakesError::PoisonedLock
+    }
+}