From 633fa63b7e6c858ef1536503e52bb146b9798bbf Mon Sep 17 00:00:00 2001
From: Denis Subbotin <denis@subbot.in>
Date: Thu, 31 Aug 2023 20:57:33 +0300
Subject: [PATCH] more fixes for staking APY

---
 pkg/api/staking_handlers.go | 11 +++--------
 pkg/core/staking.go         | 15 +++++++++++++++
 pkg/litestorage/stacking.go |  3 +--
 3 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/pkg/api/staking_handlers.go b/pkg/api/staking_handlers.go
index 9f67f9fa..58504b44 100644
--- a/pkg/api/staking_handlers.go
+++ b/pkg/api/staking_handlers.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"math"
 	"net/http"
 
 	"github.com/tonkeeper/opentonapi/internal/g"
@@ -269,12 +270,7 @@ func (h Handler) GetStakingPoolHistory(ctx context.Context, params oas.GetStakin
 		return nil, toError(http.StatusInternalServerError, err)
 	}
 	var result oas.GetStakingPoolHistoryOK
-	var prevTime uint32
-	for i, l := range logs {
-		if i == 0 {
-			prevTime = l.CreatedAt
-			continue
-		}
+	for _, l := range logs {
 		cells, err := boc.DeserializeBoc(l.Body)
 		if err != nil {
 			return nil, toError(http.StatusInternalServerError, err)
@@ -292,10 +288,9 @@ func (h Handler) GetStakingPoolHistory(ctx context.Context, params oas.GetStakin
 			return nil, toError(http.StatusInternalServerError, err)
 		}
 		result.Apy = append(result.Apy, oas.ApyHistory{
-			Apy:  float64(round.Profit) / float64(round.TotalBalance) / float64(l.CreatedAt-prevTime) * 3600 * 24 * 365 * 100,
+			Apy:  (math.Pow(float64(round.Returned-round.Borrowed)/float64(round.TotalBalance)+1, 365*24*60*60/float64(65536)) - 1) * 100,
 			Time: int(l.CreatedAt),
 		})
-		prevTime = l.CreatedAt
 	}
 	return &result, nil
 }
diff --git a/pkg/core/staking.go b/pkg/core/staking.go
index 8f1c19a1..8a4c7c09 100644
--- a/pkg/core/staking.go
+++ b/pkg/core/staking.go
@@ -2,6 +2,7 @@ package core
 
 import (
 	"github.com/tonkeeper/tongo"
+	"math"
 )
 
 type Nominator struct {
@@ -35,3 +36,17 @@ type LiquidPool struct {
 	JettonMaster    tongo.AccountID
 	APY             float64
 }
+
+func CalculateAPY(roundExpected, roundBorrowed int64, governanceFee int32) float64 {
+	const secondsPerRound = 1 << 16
+	const secondsPerYear = 3600 * 24 * 365
+	roundsPerYear := float64(secondsPerYear) / float64(secondsPerRound)
+	effectiveRounds := roundsPerYear / 2 // Because each coin may participate only in odd/even rounds
+	profitPrevRound := float64(roundExpected-roundBorrowed) * (1 - float64(governanceFee)/float64(1<<24))
+	percentPerPrevRound := profitPrevRound / float64(roundBorrowed)
+	apy := (math.Pow(1+percentPerPrevRound, effectiveRounds) - 1) * 100
+	if math.IsNaN(apy) {
+		return 0
+	}
+	return apy
+}
diff --git a/pkg/litestorage/stacking.go b/pkg/litestorage/stacking.go
index 8cf15a83..d19b553e 100644
--- a/pkg/litestorage/stacking.go
+++ b/pkg/litestorage/stacking.go
@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	"math"
 	"math/big"
 
 	"github.com/tonkeeper/tongo/tlb"
@@ -202,7 +201,7 @@ func (s *LiteStorage) GetLiquidPool(ctx context.Context, pool tongo.AccountID) (
 		TotalAmount:     p.TotalBalance,
 		VerifiedSources: bytes.Equal(hash, references.TFLiquidPoolCodeHash[:]),
 		JettonMaster:    *jettonMaster,
-		APY:             (math.Pow(1+float64(p.InterestRate)/float64(1<<24)*(1-float64(p.GovernanceFee)/float64(1<<24)), 3600*24*366/(1<<16)) - 1) * 100,
+		APY:             core.CalculateAPY(p.PrevRoundBorrowers.Expected, p.PrevRoundBorrowers.Borrowed, p.InterestRate),
 	}, err
 }