CommonPeriod and SyncPeriod added. (#213)

# Describe Request

CommonPeriod and SyncPeriod are added to help synchronize channels with
varying periods.

Fixed #211

# Change Type

New feature.

helper/sync.go

@@ -0,0 +1,37 @@
+// Copyright (c) 2021-2024 Onur Cinar.
+// The source code is provided under GNU AGPLv3 License.
+// https://github.com/cinar/indicator
+
+package helper
+
+import "slices"
+
+// CommonPeriod calculates the smallest period at which all data channels can be synchronized
+//
+// Example:
+//
+//	// Synchronize channels with periods 4, 2, and 3.
+//	commonPeriod := helper.CommonPeriod(4, 2, 3) // commonPeriod = 4
+//
+//	// Synchronize the first channel
+//	c1 := helper.Sync(commonPeriod, 4, c1)
+//
+//	// Synchronize the second channel
+//	c2 := helper.Sync(commonPeriod, 2, c2)
+//
+//	// Synchronize the third channel
+//	c3 := helper.Sync(commonPeriod, 3, c3)
+func CommonPeriod(periods ...int) int {
+	return slices.Max(periods)
+}
+
+// SyncPeriod adjusts the given channel to match the given common period.
+func SyncPeriod[T any](commonPeriod, period int, c <-chan T) <-chan T {
+	forwardPeriod := commonPeriod - period
+
+	if forwardPeriod > 0 {
+		c = Skip(c, forwardPeriod)
+	}
+
+	return c
+}

helper/sync_test.go

@@ -0,0 +1,33 @@
+// Copyright (c) 2021-2024 Onur Cinar.
+// The source code is provided under GNU AGPLv3 License.
+// https://github.com/cinar/indicator
+
+package helper_test
+
+import (
+	"testing"
+
+	"github.com/cinar/indicator/v2/helper"
+)
+
+func TestSync(t *testing.T) {
+	input1 := helper.Skip(helper.SliceToChan([]int{0, 0, 0, 0, 1, 2, 3, 4}), 4)
+	input2 := helper.Skip(helper.SliceToChan([]int{0, 0, 1, 2, 3, 4, 5, 6}), 2)
+	input3 := helper.Skip(helper.SliceToChan([]int{0, 0, 0, 1, 2, 3, 4, 5}), 3)
+
+	commonPeriod := helper.CommonPeriod(4, 2, 3)
+
+	actual1 := helper.SyncPeriod(commonPeriod, 4, input1)
+	expected1 := helper.SliceToChan([]int{1, 2, 3, 4})
+
+	actual2 := helper.SyncPeriod(commonPeriod, 2, input2)
+	expected2 := helper.SliceToChan([]int{3, 4, 5, 6})
+
+	actual3 := helper.SyncPeriod(commonPeriod, 3, input3)
+	expected3 := helper.SliceToChan([]int{2, 3, 4, 5})
+
+	err := helper.CheckEquals(actual1, expected1, actual2, expected2, actual3, expected3)
+	if err != nil {
+		t.Fatal(err)
+	}
+}