feat: use new IEnumeratable type

BallanceTasEditor/Utils/CountableEnumerable.cs

@@ -0,0 +1,64 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace BallanceTasEditor.Utils {
+    /// <summary>
+    /// 一种提前给定元素个数的的IEnumerable。
+    /// </summary>
+    public sealed class CountableEnumerable<T> {
+        /// <summary>
+        /// 以直接方式构建。
+        /// </summary>
+        /// <param name="enumerable">一个迭代器，其最多只能迭代给定次数。</param>
+        /// <param name="count">迭代器会迭代的次数。</param>
+        public CountableEnumerable(IEnumerable<T> enumerable, int count) {
+            m_Inner = enumerable;
+            m_Count = count;
+        }
+
+        /// <summary>
+        /// 从数组便捷构建。
+        /// </summary>
+        /// <param name="array">要使用的数组。</param>
+        public CountableEnumerable(T[] array) {
+            m_Inner = array;
+            m_Count = array.Length;
+        }
+
+        private IEnumerable<T> m_Inner;
+        private int m_Count;
+
+        /// <summary>
+        /// 获取迭代器对象。
+        /// </summary>
+        /// <returns>用于迭代的迭代器。</returns>
+        /// <exception cref="ArgumentException">当迭代器迭代次数与给定次数不匹配时。</exception>
+        public IEnumerable<T> GetInner() {
+            int counter = 0;
+            foreach (var item in m_Inner) {
+                if (counter >= m_Count) {
+                    throw new ArgumentException("Given IEnumerable<T> is not stopped at given count.");
+                } else {
+                    yield return item;
+                    ++counter;
+                }
+            }
+
+            if (counter != m_Count) {
+                throw new ArgumentException("Given IEnumerable<T> is not stopped at given count.");
+            }
+        }
+
+        /// <summary>
+        /// 获取该迭代器会迭代的次数。
+        /// </summary>
+        /// <returns>迭代器会迭代的次数，用于给使用该结构的方法提前分配必要的空间。</returns>
+        public int GetCount() {
+            return m_Count;
+        }
+
+    }
+}