Move SliceMedianValue to math

pkg/math/slice.go

@@ -0,0 +1,53 @@
+package math
+
+import "slices"
+
+type number interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64
+}
+
+// SliceMedianValue returns the median value of the given slice.
+// Returns 0 for an empty slice. If inPlace is true, the input slice will be sorted in place.
+// Otherwise, a copy of the input slice will be sorted.
+func SliceMedianValue[T number](items []T, inPlace bool) T {
+	if inPlace {
+		return sliceMedianValue(items)
+	}
+
+	copied := make([]T, len(items))
+	copy(copied, items)
+
+	out := sliceMedianValue(copied)
+
+	// We don't need the copy anymore
+	//nolint:ineffassign // let's help the garbage collector :)
+	copied = nil
+
+	return out
+}
+
+func sliceMedianValue[T number](items []T) T {
+	switch len(items) {
+	case 0:
+		return 0
+	case 1:
+		return items[0]
+	}
+
+	slices.Sort(items)
+
+	// note that int division is used here e.g. 5/2 => 2
+
+	// []int{1 2 3 4 5} => items[(5/2)] => items[2] => 3
+	if len(items)%2 == 1 {
+		return items[len(items)/2]
+	}
+
+	// odd number of items
+	rightIndex := len(items) / 2
+	leftIndex := rightIndex - 1
+
+	// []int{1 2 3 4} => (items[1] + items[2]) / 2 => 5/2 => 2
+	return (items[leftIndex] + items[rightIndex]) / 2
+}

pkg/math/slice_test.go

@@ -0,0 +1,75 @@
+package math
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSliceMedianValue(t *testing.T) {
+	for _, tt := range []struct {
+		name     string
+		input    []int
+		expected int
+		inPlace  bool
+	}{
+		{
+			name:     "empty",
+			input:    nil,
+			expected: 0,
+			inPlace:  false,
+		},
+		{
+			name:     "single",
+			input:    []int{10},
+			expected: 10,
+		},
+		{
+			name:     "two",
+			input:    []int{10, 20},
+			expected: 15,
+		},
+		{
+			name:     "even",
+			input:    []int{30, 20, 10, 20},
+			expected: 20,
+		},
+		{
+			name:     "even in-place",
+			input:    []int{30, 20, 10, 20},
+			expected: 20,
+			inPlace:  true,
+		},
+		{
+			name:     "odd",
+			input:    []int{5, 5, 6, 1, 1, 1, 4},
+			expected: 4,
+		},
+		{
+			name:     "odd in-place",
+			input:    []int{1, 1, 1, 1, 7, 7, 7, 7},
+			expected: 4,
+		},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			// ASSERT
+			// Given a copy of the input slice
+			var snapshot []int
+			for _, v := range tt.input {
+				snapshot = append(snapshot, v)
+			}
+
+			// ACT
+			out := SliceMedianValue(tt.input, tt.inPlace)
+
+			// ASSERT
+			assert.Equal(t, tt.expected, out)
+
+			// Check that elements of the input slice are unchanged
+			if !tt.inPlace {
+				assert.Equal(t, snapshot, tt.input)
+			}
+		})
+	}
+
+}

x/crosschain/keeper/gas_price.go

@@ -6,8 +6,8 @@ import (
 	"cosmossdk.io/math"
 	"github.com/cosmos/cosmos-sdk/store/prefix"
 	sdk "github.com/cosmos/cosmos-sdk/types"
-	"golang.org/x/exp/slices"
 
+	slicemath "github.com/zeta-chain/zetacore/pkg/math"
 	"github.com/zeta-chain/zetacore/x/crosschain/types"
 )
 
@@ -44,36 +44,12 @@ func (k Keeper) GetMedianGasPriceInUint(ctx sdk.Context, chainID int64) (math.Ui
 
 	var (
 		gasPrice    = math.NewUint(entity.Prices[entity.MedianIndex])
-		priorityFee = math.NewUint(medianValue(entity.PriorityFees))
+		priorityFee = math.NewUint(slicemath.SliceMedianValue(entity.PriorityFees, false))
 	)
 
 	return gasPrice, priorityFee, true
 }
 
-// medianValue returns the median value of a slice
-// example: [ 1 7 5 2 3 6 4 ] => [ 1 2 3 4 5 6 7 ] => 4
-func medianValue(items []uint64) uint64 {
-	switch len(items) {
-	case 0:
-		return 0
-	case 1:
-		return items[0]
-	}
-
-	// We don't want to modify the original slice
-	copiedItems := make([]uint64, len(items))
-	copy(copiedItems, items)
-
-	slices.Sort(copiedItems)
-	mv := copiedItems[len(copiedItems)/2]
-
-	// We don't need the copy anymore
-	//nolint:ineffassign // let's help garbage collector :)
-	copiedItems = nil
-
-	return mv
-}
-
 // RemoveGasPrice removes a gasPrice from the store
 func (k Keeper) RemoveGasPrice(ctx sdk.Context, index string) {
 	store := prefix.NewStore(ctx.KVStore(k.storeKey), types.KeyPrefix(types.GasPriceKey))