refeat: ILexer接口适配 (#38)

Co-authored-by: Huaps <1183155719@qq.com>
Co-authored-by: duqoo <92306417+duqoo@users.noreply.github.com>
Reviewed-on: PostGuard/Canon#38

Canon.Core/Abstractions/ISourceReader.cs

@@ -7,12 +7,7 @@ namespace Canon.Core.Abstractions;
 /// </summary>
 public interface ISourceReader
 {
-    /// <summary>
-    /// 尝试读取下一个字符
-    /// </summary>
-    /// <param name="c">读取到的字符</param>
-    /// <returns>是否成功读取</returns>
-    public bool TryReadChar([NotNullWhen(true)] out char? c);
+    public char Current { get; }
 
     /// <summary>
     /// 源文件名称
@@ -28,4 +23,23 @@ public interface ISourceReader
     /// 当前读取字符的列号
     /// </summary>
     public uint Pos { get; }
+
+    /// <summary>
+    /// 回退一个字符
+    /// </summary>
+    /// <returns>回退是否成功</returns>
+    public bool Retract();
+
+    /// <summary>
+    /// 前进一个字符
+    /// </summary>
+    /// <returns></returns>
+    public bool MoveNext();
+
+    /// <summary>
+    /// 读取下一个字符但是移进
+    /// </summary>
+    /// <param name="c">读取到的下一个字符</param>
+    /// <returns>是否能够读取下一个字符</returns>
+    public bool TryPeekChar([NotNullWhen(true)] out char? c);
 }