feat: Introduce RewardBase

Lib9c/Delegation/RewardBase.cs

@@ -0,0 +1,188 @@
+#nullable enable
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Linq;
+using System.Numerics;
+using Bencodex;
+using Bencodex.Types;
+using Libplanet.Crypto;
+using Libplanet.Types.Assets;
+using Nekoyume.Action;
+
+namespace Nekoyume.Delegation
+{
+    /// <summary>
+    /// RewardBase is a class that represents the base of the reward.
+    /// If it's multiplied by the number of shares, it will be the reward for the period.
+    /// Also, it holds the significant figure to calculate the reward.
+    /// </summary>
+    public class RewardBase : IBencodable, IEquatable<RewardBase>
+    {
+        private const string StateTypeName = "reward_base";
+        private const long StateVersion = 1;
+        private readonly IComparer<Currency> _currencyComparer = new CurrencyComparer();
+
+        public RewardBase(
+            Address address,
+            BigInteger totalShares,
+            IEnumerable<Currency> currencies)
+            : this(
+                  address,
+                  totalShares,
+                  currencies.Select(c => c * 0),
+                  RecommendedSigFig(totalShares))
+        {
+        }
+
+        public RewardBase(Address address, IValue bencoded)
+            : this(address, (List)bencoded)
+        {
+        }
+
+        public RewardBase(
+            Address address,
+            BigInteger totalShares,
+            IEnumerable<FungibleAssetValue> rewardPortion,
+            int sigfig)
+        {
+            Address = address;
+
+            if (totalShares.Sign <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(totalShares));
+            }
+
+            TotalShares = totalShares;
+
+            if (!rewardPortion.Select(f => f.Currency).All(new HashSet<Currency>().Add))
+            {
+                throw new ArgumentException("Duplicated currency in reward base.");
+            }
+
+            RewardPortion = rewardPortion.ToImmutableDictionary(f => f.Currency, f => f);
+            SigFig = sigfig;
+        }
+
+
+        public RewardBase(Address address, List bencoded)
+        {
+            if (bencoded[0] is not Text text || text != StateTypeName || bencoded[1] is not Integer integer)
+            {
+                throw new InvalidCastException();
+            }
+
+            if (integer > StateVersion)
+            {
+                throw new FailedLoadStateException("Un-deserializable state.");
+            }
+
+            Address = address;
+            TotalShares = (Integer)bencoded[2];
+            var rewardPortion = ((List)bencoded[3]).Select(v => new FungibleAssetValue(v));
+
+            if (!rewardPortion.Select(f => f.Currency).All(new HashSet<Currency>().Add))
+            {
+                throw new ArgumentException("Duplicated currency in reward base.");
+            }
+
+            RewardPortion = rewardPortion.ToImmutableDictionary(f => f.Currency, f => f);
+            SigFig = (Integer)bencoded[4];
+        }
+
+        private RewardBase(
+            Address address,
+            BigInteger totalShares,
+            ImmutableDictionary<Currency, FungibleAssetValue> rewardPortion,
+            int sigfig)
+        {
+            Address = address;
+            TotalShares = totalShares;
+            RewardPortion = rewardPortion;
+            SigFig = sigfig;
+        }
+
+        public Address Address { get; }
+
+        public BigInteger TotalShares { get; }
+
+        public int SigFig { get; private set; }
+
+        public static int Margin => 2;
+
+        public ImmutableDictionary<Currency, FungibleAssetValue> RewardPortion { get; }
+
+        public List Bencoded
+            => List.Empty
+                .Add(StateTypeName)
+                .Add(StateVersion)
+                .Add(TotalShares)
+                .Add(new List(RewardPortion
+                    .OrderBy(r => r.Key, _currencyComparer)
+                    .Select(r => r.Value.Serialize())))
+                .Add(SigFig);
+
+        IValue IBencodable.Bencoded => Bencoded;
+
+        public RewardBase AddRewards(IEnumerable<FungibleAssetValue> rewards)
+            => rewards.Aggregate(this, (accum, next) => AddReward(accum, next));
+
+        public RewardBase AddReward(FungibleAssetValue reward)
+            => AddReward(this, reward);
+
+        public RewardBase UpdateTotalShares(BigInteger totalShares)
+            => UpdateTotalShares(this, totalShares);
+
+        public static RewardBase AddReward(RewardBase rewardBase, FungibleAssetValue reward)
+            => new RewardBase(
+                rewardBase.Address,
+                rewardBase.TotalShares,
+                rewardBase.RewardPortion.TryGetValue(reward.Currency, out var portion)
+                    ? rewardBase.RewardPortion.SetItem(
+                        reward.Currency,
+                        portion + (reward * rewardBase.SigFig).DivRem(rewardBase.TotalShares).Quotient)
+                    : throw new ArgumentException($"Invalid reward currency: {reward.Currency}"),
+                rewardBase.SigFig);
+
+        public static RewardBase UpdateTotalShares(RewardBase rewardBase, BigInteger totalShares)
+        {
+            var newSigFig = Math.Max(rewardBase.SigFig, RecommendedSigFig(totalShares));
+            var multiplier = BigInteger.Pow(10, newSigFig - rewardBase.SigFig);
+            var newPortion = rewardBase.RewardPortion.ToImmutableDictionary(
+                kvp => kvp.Key,
+                kvp => (kvp.Value * multiplier).DivRem(rewardBase.TotalShares).Quotient);
+
+            return new RewardBase(
+                rewardBase.Address,
+                totalShares,
+                newPortion,
+                newSigFig);
+        }
+
+        public static int RecommendedSigFig(BigInteger totalShares)
+            => (int)Math.Floor(BigInteger.Log10(totalShares)) + Margin;
+
+        public ImmutableSortedDictionary<Currency, FungibleAssetValue> RewardsDuringPeriod(BigInteger share)
+            => RewardPortion.Keys.Select(k => RewardsDuringPeriod(share, k))
+                .ToImmutableSortedDictionary(f => f.Currency, f => f, _currencyComparer);
+
+        public FungibleAssetValue RewardsDuringPeriod(BigInteger share, Currency currency)
+            => RewardPortion.TryGetValue(currency, out var portion)
+                ? (portion * share).DivRem(SigFig).Quotient
+                : throw new ArgumentException($"Invalid reward currency: {currency}");
+
+        public override bool Equals(object? obj)
+            => obj is RewardBase other && Equals(other);
+
+        public bool Equals(RewardBase? other)
+            => ReferenceEquals(this, other)
+            || (other is RewardBase rewardBase
+            && Address == rewardBase.Address
+            && TotalShares == rewardBase.TotalShares
+            && RewardPortion.Equals(rewardBase.RewardPortion)
+            && SigFig == rewardBase.SigFig);
+
+        public override int GetHashCode()
+            => Address.GetHashCode();
+    }
+}