From f147f78a41117a3c5b95de2690efad85173d3c77 Mon Sep 17 00:00:00 2001
From: donutloop <marcel.edmund.franke@gmail.com>
Date: Tue, 11 Jan 2022 13:13:25 +0100
Subject: [PATCH] Slice: sort from v2 branch (#22)

ref: https://github.com/duke-git/lancet/commit/f1d7154179a4d94472bee9703097d78e6c37e9a7
---
 slice/slice.go      | 37 +++++++++++++++++++++++++++----------
 slice/slice_test.go | 28 +++++++++++++++++++++++++++-
 2 files changed, 54 insertions(+), 11 deletions(-)

diff --git a/slice/slice.go b/slice/slice.go
index 8df6748..da07554 100644
--- a/slice/slice.go
+++ b/slice/slice.go
@@ -675,18 +675,38 @@ func SortByField(slice interface{}, field string, sortType ...string) error {
 	}
 
 	// Create a less function based on the field's kind.
-	var less func(a, b reflect.Value) bool
+	var compare func(a, b reflect.Value) bool
 	switch sf.Type.Kind() {
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		less = func(a, b reflect.Value) bool { return a.Int() < b.Int() }
+		if len(sortType) > 0 && sortType[0] == "desc" {
+			compare = func(a, b reflect.Value) bool { return a.Int() > b.Int() }
+		} else {
+			compare = func(a, b reflect.Value) bool { return a.Int() < b.Int() }
+		}
 	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
-		less = func(a, b reflect.Value) bool { return a.Uint() < b.Uint() }
+		if len(sortType) > 0 && sortType[0] == "desc" {
+			compare = func(a, b reflect.Value) bool { return a.Uint() > b.Uint() }
+		} else {
+			compare = func(a, b reflect.Value) bool { return a.Uint() < b.Uint() }
+		}
 	case reflect.Float32, reflect.Float64:
-		less = func(a, b reflect.Value) bool { return a.Float() < b.Float() }
+		if len(sortType) > 0 && sortType[0] == "desc" {
+			compare = func(a, b reflect.Value) bool { return a.Float() > b.Float() }
+		} else {
+			compare = func(a, b reflect.Value) bool { return a.Float() < b.Float() }
+		}
 	case reflect.String:
-		less = func(a, b reflect.Value) bool { return a.String() < b.String() }
+		if len(sortType) > 0 && sortType[0] == "desc" {
+			compare = func(a, b reflect.Value) bool { return a.String() > b.String() }
+		} else {
+			compare = func(a, b reflect.Value) bool { return a.String() < b.String() }
+		}
 	case reflect.Bool:
-		less = func(a, b reflect.Value) bool { return !a.Bool() && b.Bool() }
+		if len(sortType) > 0 && sortType[0] == "desc" {
+			compare = func(a, b reflect.Value) bool { return a.Bool() && !b.Bool() }
+		} else {
+			compare = func(a, b reflect.Value) bool { return !a.Bool() && b.Bool() }
+		}
 	default:
 		return fmt.Errorf("field type %s not supported", sf.Type)
 	}
@@ -700,12 +720,9 @@ func SortByField(slice interface{}, field string, sortType ...string) error {
 		}
 		a = a.FieldByIndex(sf.Index)
 		b = b.FieldByIndex(sf.Index)
-		return less(a, b)
+		return compare(a, b)
 	})
 
-	if sortType[0] == "desc" {
-		ReverseSlice(slice)
-	}
 	return nil
 }
 
diff --git a/slice/slice_test.go b/slice/slice_test.go
index d3f402e..9a7d6d2 100644
--- a/slice/slice_test.go
+++ b/slice/slice_test.go
@@ -443,7 +443,7 @@ func TestDifference(t *testing.T) {
 	assert.Equal([]int{1, 2, 3}, Difference(s1, s2))
 }
 
-func TestSortByField(t *testing.T) {
+func TestSortByFielDesc(t *testing.T) {
 	assert := internal.NewAssert(t, "TestWithout")
 
 	type student struct {
@@ -469,6 +469,32 @@ func TestSortByField(t *testing.T) {
 	assert.Equal(students, studentsOfSortByAge)
 }
 
+func TestSortByFieldAsc(t *testing.T) {
+	assert := internal.NewAssert(t, "TestSortByField")
+
+	type student struct {
+		name string
+		age  int
+	}
+	students := []student{
+		{"a", 10},
+		{"b", 15},
+		{"c", 5},
+		{"d", 6},
+	}
+	studentsOfSortByAge := []student{
+		{"c", 5},
+		{"d", 6},
+		{"a", 10},
+		{"b", 15},
+	}
+
+	err := SortByField(students, "age")
+	assert.IsNil(err)
+
+	assert.Equal(students, studentsOfSortByAge)
+}
+
 func TestWithout(t *testing.T) {
 	assert := internal.NewAssert(t, "TestWithout")
 	assert.Equal([]int{3, 4, 5}, Without([]int{1, 2, 3, 4, 5}, 1, 2))