Improve utils of slices (#22379)

- Move the file `compare.go` and `slice.go` to `slice.go`.
- Fix `ExistsInSlice`, it's buggy
  - It uses `sort.Search`, so it assumes that the input slice is sorted.
- It passes `func(i int) bool { return slice[i] == target })` to
`sort.Search`, that's incorrect, check the doc of `sort.Search`.
- Conbine `IsInt64InSlice(int64, []int64)` and `ExistsInSlice(string,
[]string)` to `SliceContains[T]([]T, T)`.
- Conbine `IsSliceInt64Eq([]int64, []int64)` and `IsEqualSlice([]string,
[]string)` to `SliceSortedEqual[T]([]T, T)`.
- Add `SliceEqual[T]([]T, T)` as a distinction from
`SliceSortedEqual[T]([]T, T)`.
- Redesign `RemoveIDFromList([]int64, int64) ([]int64, bool)` to
`SliceRemoveAll[T]([]T, T) []T`.
- Add `SliceContainsFunc[T]([]T, func(T) bool)` and
`SliceRemoveAllFunc[T]([]T, func(T) bool)` for general use.
- Add comments to explain why not `golang.org/x/exp/slices`.
- Add unit tests.

modules/util/slice.go

@@ -1,17 +1,90 @@
 // Copyright 2022 The Gitea Authors. All rights reserved.
 // SPDX-License-Identifier: MIT
 
+// Most of the functions in this file can have better implementations with "golang.org/x/exp/slices".
+// However, "golang.org/x/exp" is experimental and unreliable, we shouldn't use it.
+// So lets waiting for the "slices" has be promoted to the main repository one day.
+
 package util
 
-// RemoveIDFromList removes the given ID from the slice, if found.
-// It does not preserve order, and assumes the ID is unique.
-func RemoveIDFromList(list []int64, id int64) ([]int64, bool) {
-	n := len(list) - 1
-	for i, item := range list {
-		if item == id {
-			list[i] = list[n]
-			return list[:n], true
+import "strings"
+
+// SliceContains returns true if the target exists in the slice.
+func SliceContains[T comparable](slice []T, target T) bool {
+	return SliceContainsFunc(slice, func(t T) bool { return t == target })
+}
+
+// SliceContainsFunc returns true if any element in the slice satisfies the targetFunc.
+func SliceContainsFunc[T any](slice []T, targetFunc func(T) bool) bool {
+	for _, v := range slice {
+		if targetFunc(v) {
+			return true
 		}
 	}
-	return list, false
+	return false
+}
+
+// SliceContainsString sequential searches if string exists in slice.
+func SliceContainsString(slice []string, target string, insensitive ...bool) bool {
+	if len(insensitive) != 0 && insensitive[0] {
+		target = strings.ToLower(target)
+		return SliceContainsFunc(slice, func(t string) bool { return strings.ToLower(t) == target })
+	}
+
+	return SliceContains(slice, target)
+}
+
+// SliceSortedEqual returns true if the two slices will be equal when they get sorted.
+// It doesn't require that the slices have been sorted, and it doesn't sort them either.
+func SliceSortedEqual[T comparable](s1, s2 []T) bool {
+	if len(s1) != len(s2) {
+		return false
+	}
+
+	counts := make(map[T]int, len(s1))
+	for _, v := range s1 {
+		counts[v]++
+	}
+	for _, v := range s2 {
+		counts[v]--
+	}
+
+	for _, v := range counts {
+		if v != 0 {
+			return false
+		}
+	}
+	return true
+}
+
+// SliceEqual returns true if the two slices are equal.
+func SliceEqual[T comparable](s1, s2 []T) bool {
+	if len(s1) != len(s2) {
+		return false
+	}
+
+	for i, v := range s1 {
+		if s2[i] != v {
+			return false
+		}
+	}
+	return true
+}
+
+// SliceRemoveAll removes all the target elements from the slice.
+func SliceRemoveAll[T comparable](slice []T, target T) []T {
+	return SliceRemoveAllFunc(slice, func(t T) bool { return t == target })
+}
+
+// SliceRemoveAllFunc removes all elements which satisfy the targetFunc from the slice.
+func SliceRemoveAllFunc[T comparable](slice []T, targetFunc func(T) bool) []T {
+	idx := 0
+	for _, v := range slice {
+		if targetFunc(v) {
+			continue
+		}
+		slice[idx] = v
+		idx++
+	}
+	return slice[:idx]
 }