From e7a4b766ecbfc8dbe993d5a89ec4da9a34ae7137 Mon Sep 17 00:00:00 2001
From: andy840119 <andy840119@gmail.com>
Date: Thu, 7 Dec 2023 00:11:12 +0800
Subject: [PATCH] Make the utility easy to understand.

---
 LrcParser.Tests/Utils/TextIndexUtilsTest.cs |  4 ++--
 LrcParser/Utils/TextIndexUtils.cs           | 11 +++++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/LrcParser.Tests/Utils/TextIndexUtilsTest.cs b/LrcParser.Tests/Utils/TextIndexUtilsTest.cs
index 7020357..b5578ad 100644
--- a/LrcParser.Tests/Utils/TextIndexUtilsTest.cs
+++ b/LrcParser.Tests/Utils/TextIndexUtilsTest.cs
@@ -35,8 +35,8 @@ public void TestToGapIndex(int index, IndexState state, int expected)
 
     [TestCase(IndexState.Start, 1, -1, 1)]
     [TestCase(IndexState.End, 1, -1, -1)]
-    [TestCase(IndexState.Start, "1", "-1", "1")]
-    [TestCase(IndexState.End, "1", "-1", "-1")]
+    [TestCase(IndexState.Start, "start", "end", "start")]
+    [TestCase(IndexState.End, "start", "end", "end")]
     public void TestGetValueByState(IndexState state, object startValue, object endValue, object expected)
     {
         var textIndex = new TextIndex(0, state);
diff --git a/LrcParser/Utils/TextIndexUtils.cs b/LrcParser/Utils/TextIndexUtils.cs
index bc78424..57530d5 100644
--- a/LrcParser/Utils/TextIndexUtils.cs
+++ b/LrcParser/Utils/TextIndexUtils.cs
@@ -26,6 +26,17 @@ internal static int ToCharIndex(TextIndex index)
     internal static int ToGapIndex(TextIndex index)
         => GetValueByState(index, index.Index, index.Index + 1);
 
+    /// <summary>
+    /// Get the value by state.
+    /// If the state is start, then return start value.
+    /// If the state is end, then return end value.
+    /// </summary>
+    /// <param name="index"></param>
+    /// <param name="startValue"></param>
+    /// <param name="endValue"></param>
+    /// <typeparam name="T"></typeparam>
+    /// <returns></returns>
+    /// <exception cref="ArgumentOutOfRangeException"></exception>
     internal static T GetValueByState<T>(TextIndex index, T startValue, T endValue) =>
         index.State switch
         {