feat: add function package for funcational programming

function/function.go

@@ -0,0 +1,72 @@
+// Copyright 2021 dudaodong@gmail.com. All rights reserved.
+// Use of this source code is governed by MIT license
+
+// Package function implements some functions for functional programming.
+
+package function
+
+import (
+	"reflect"
+	"time"
+)
+
+// After creates a function that invokes func once it's called n or more times
+func After(n int, fn interface{}) func(args ...interface{}) []reflect.Value {
+	return func(args ...interface{}) []reflect.Value {
+		n--
+		if n < 1 {
+			return invokeFunc(fn, args...)
+		}
+		return nil
+	}
+}
+
+// Before creates a function that invokes func once it's called less than n times
+func Before(n int, fn interface{}) func(args ...interface{}) []reflect.Value {
+	var res []reflect.Value
+
+	return func(args ...interface{}) []reflect.Value {
+		if n > 0 {
+			res = invokeFunc(fn, args...)
+		}
+		if n <= 0 {
+			fn = nil
+		}
+		n--
+		return res
+	}
+}
+
+type Fn func(...interface{}) interface{}
+
+// Curry make a curryed function
+func (f Fn) Curry(i interface{}) func(...interface{}) interface{} {
+	return func(values ...interface{}) interface{} {
+		v := append([]interface{}{i}, values...)
+		return f(v...)
+	}
+}
+
+// Delay make the function excution after delayed time
+func Delay(delay time.Duration, fn interface{}, args ...interface{}) {
+	time.Sleep(delay)
+	invokeFunc(fn, args...)
+}
+
+// Schedule invoke function every duration time, util close the returned bool chan
+func Schedule(d time.Duration, fn interface{}, args ...interface{}) chan bool {
+	quit := make(chan bool)
+
+	go func() {
+		for {
+			invokeFunc(fn, args...)
+			select {
+			case <-time.After(d):
+			case <-quit:
+				return
+			}
+		}
+	}()
+
+	return quit
+}