From e138043289d80efdcf9bd5a6f5d362268e053f11 Mon Sep 17 00:00:00 2001
From: donutloop <marcel.edmund.franke@gmail.com>
Date: Mon, 4 Mar 2024 03:00:43 +0100
Subject: [PATCH] Function: AcceptIf (#198)

AcceptIf returns another function of the same signature as the apply function but also includes a bool value to indicate success or failure.
A predicate function that takes an argument of type T and returns a bool.
An apply function that also takes an argument of type T and returns a modified value of the same type.
---
 docs/api/packages/function.md     | 53 +++++++++++++++++++++++++++
 docs/en/api/packages/function.md  | 54 ++++++++++++++++++++++++++++
 function/function.go              | 21 +++++++++++
 function/function_example_test.go | 29 +++++++++++++++
 function/function_test.go         | 60 +++++++++++++++++++++++++++++++
 5 files changed, 217 insertions(+)

diff --git a/docs/api/packages/function.md b/docs/api/packages/function.md
index 284f6fc..d338125 100644
--- a/docs/api/packages/function.md
+++ b/docs/api/packages/function.md
@@ -39,6 +39,8 @@ import (
 -   [Nor](#Nor)
 -   [Xnor](#Xnor)
 -   [Nand](#Nand)
+-   [AcceptIf](#AcceptIf)
+
 
 <div STYLE="page-break-after: always;"></div>
 
@@ -638,4 +640,55 @@ func main() {
     // true
     // false
 }
+```
+
+### <span id="AcceptIf">AcceptIf</span>
+
+<p>TBD</p>
+
+<b>函数签名:</b>
+
+```go
+func AcceptIf[T any](predicate func(T) bool, apply func(T) T) func(T) (T, bool)
+```
+
+<b>示例:</b>
+
+```go
+package main
+
+import (
+    "fmt"
+    "github.com/duke-git/lancet/v2/function"
+)
+
+func main() {
+
+	adder := AcceptIf(
+		And(
+			func(x int) bool {
+				return x > 10
+			}, func(x int) bool {
+				return x%2 == 0
+			}),
+		func(x int) int {
+			return x + 1
+		},
+	)
+
+	result, ok := adder(20)
+	fmt.Println(result)
+	fmt.Println(ok)
+
+	result, ok = adder(21)
+	fmt.Println(result)
+	fmt.Println(ok)
+
+	// Output:
+	// 21
+	// true
+	// 0
+	// false
+}
+
 ```
\ No newline at end of file
diff --git a/docs/en/api/packages/function.md b/docs/en/api/packages/function.md
index c810b92..8e798ae 100644
--- a/docs/en/api/packages/function.md
+++ b/docs/en/api/packages/function.md
@@ -39,6 +39,7 @@ import (
 -   [Nor](#Nor)
 -   [Xnor](#Xnor)
 -   [Nand](#Nand)
+-   [AcceptIf](#AcceptIf)
 
 <div STYLE="page-break-after: always;"></div>
 
@@ -638,4 +639,57 @@ func main() {
     // true
     // false
 }
+```
+
+### <span id="AcceptIf">AcceptIf</span>
+
+<p>AcceptIf returns another function of the same signature as the apply function but also includes a bool value to indicate success or failure. 
+A predicate function that takes an argument of type T and returns a bool.
+An apply function that also takes an argument of type T and returns a modified value of the same type.</p>
+
+<b>Signature:</b>
+
+```go
+func AcceptIf[T any](predicate func(T) bool, apply func(T) T) func(T) (T, bool)
+```
+
+<b>Example:</b>
+
+```go
+package main
+
+import (
+    "fmt"
+    "github.com/duke-git/lancet/v2/function"
+)
+
+func main() {
+
+	adder := AcceptIf(
+		And(
+			func(x int) bool {
+				return x > 10
+			}, func(x int) bool {
+				return x%2 == 0
+			}),
+		func(x int) int {
+			return x + 1
+		},
+	)
+
+	result, ok := adder(20)
+	fmt.Println(result)
+	fmt.Println(ok)
+
+	result, ok = adder(21)
+	fmt.Println(result)
+	fmt.Println(ok)
+
+	// Output:
+	// 21
+	// true
+	// 0
+	// false
+}
+
 ```
\ No newline at end of file
diff --git a/function/function.go b/function/function.go
index 5919fe5..0840983 100644
--- a/function/function.go
+++ b/function/function.go
@@ -136,6 +136,27 @@ func Pipeline[T any](funcs ...func(T) T) func(T) T {
 	}
 }
 
+// AcceptIf returns another function of the same signature as the apply function but also includes a bool value to indicate success or failure.
+// A predicate function that takes an argument of type T and returns a bool.
+// An apply function that also takes an argument of type T and returns a modified value of the same type.
+func AcceptIf[T any](predicate func(T) bool, apply func(T) T) func(T) (T, bool) {
+	if predicate == nil {
+		panic("programming error: predicate must be not nil")
+	}
+
+	if apply == nil {
+		panic("programming error: apply must be not nil")
+	}
+
+	return func(t T) (T, bool) {
+		if !predicate(t) {
+			var defaultValue T
+			return defaultValue, false
+		}
+		return apply(t), true
+	}
+}
+
 func unsafeInvokeFunc(fn any, args ...any) []reflect.Value {
 	fv := reflect.ValueOf(fn)
 	params := make([]reflect.Value, len(args))
diff --git a/function/function_example_test.go b/function/function_example_test.go
index 5350273..f4d9562 100644
--- a/function/function_example_test.go
+++ b/function/function_example_test.go
@@ -145,3 +145,32 @@ func ExamplePipeline() {
 	// Output:
 	// 36
 }
+
+func ExampleAcceptIf() {
+
+	adder := AcceptIf(
+		And(
+			func(x int) bool {
+				return x > 10
+			}, func(x int) bool {
+				return x%2 == 0
+			}),
+		func(x int) int {
+			return x + 1
+		},
+	)
+
+	result, ok := adder(20)
+	fmt.Println(result)
+	fmt.Println(ok)
+
+	result, ok = adder(21)
+	fmt.Println(result)
+	fmt.Println(ok)
+
+	// Output:
+	// 21
+	// true
+	// 0
+	// false
+}
diff --git a/function/function_test.go b/function/function_test.go
index c9f3751..18fe547 100644
--- a/function/function_test.go
+++ b/function/function_test.go
@@ -162,3 +162,63 @@ func TestPipeline(t *testing.T) {
 
 	assert.Equal(36, f(2))
 }
+
+func TestAcceptIf(t *testing.T) {
+	assert := internal.NewAssert(t, "AcceptIf")
+
+	adder := AcceptIf(
+		And(
+			func(x int) bool {
+				return x > 10
+			}, func(x int) bool {
+				return x%2 == 0
+			}),
+		func(x int) int {
+			return x + 1
+		},
+	)
+
+	result, ok := adder(20)
+	assert.Equal(21, result)
+	assert.Equal(true, ok)
+
+	result, ok = adder(21)
+	assert.Equal(0, result)
+	assert.Equal(false, ok)
+}
+
+func TestAcceptIfPanicMissingPredicate(t *testing.T) {
+	t.Parallel()
+
+	assert := internal.NewAssert(t, "TestAcceptIfPanicMissingPredicate")
+
+	defer func() {
+		v := recover()
+		assert.Equal("programming error: predicate must be not nil", v)
+	}()
+
+	AcceptIf(
+		nil,
+		func(x int) int {
+			return x
+		},
+	)
+}
+
+func TestAcceptIfPanicMissingApply(t *testing.T) {
+	t.Parallel()
+
+	assert := internal.NewAssert(t, "TestAcceptIfPanicMissingApply")
+
+	defer func() {
+		v := recover()
+		assert.Equal("programming error: apply must be not nil", v)
+	}()
+
+	AcceptIf(
+		func(i int) bool {
+			return false
+		},
+		nil,
+	)
+}