// Copyright 2026 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package util

// DiffSlice compares two slices and returns elements added (in new but not old)
// and removed (in old but not new). Output is deduplicated.
func DiffSlice[T comparable](oldSlice, newSlice []T) (added, removed []T) {
	oldSet := make(map[T]struct{}, len(oldSlice))
	for _, v := range oldSlice {
		oldSet[v] = struct{}{}
	}

	newSet := make(map[T]struct{}, len(newSlice))
	for _, v := range newSlice {
		newSet[v] = struct{}{}
	}

	addedSet := make(map[T]struct{})
	for _, v := range newSlice {
		if _, exists := oldSet[v]; !exists {
			if _, dup := addedSet[v]; !dup {
				added = append(added, v)
				addedSet[v] = struct{}{}
			}
		}
	}

	removedSet := make(map[T]struct{})
	for _, v := range oldSlice {
		if _, exists := newSet[v]; !exists {
			if _, dup := removedSet[v]; !dup {
				removed = append(removed, v)
				removedSet[v] = struct{}{}
			}
		}
	}

	return added, removed
}