完成Parser定义以及表达式解析

src/SourceManager/SourceManager.hpp

@@ -20,6 +20,29 @@ namespace Fig
         String filePath;
         String source;
         std::vector<String> lines;
+        std::vector<size_t> lineStartIndex; // 每行在整个源字符串中的起始 index
+
+        void preprocessLineIndices()
+        {
+            lineStartIndex.clear();
+            lineStartIndex.push_back(0);
+
+            for (size_t i = 0; i < source.length(); ++i)
+            {
+                if (source[i] == U'\n')
+                {
+                    lineStartIndex.push_back(i + 1);
+                }
+                else if (source[i] == U'\r')
+                {
+                    // 处理 CRLF，只在 \n 处记录
+                    if (i + 1 < source.length() && source[i + 1] == U'\n')
+                        continue;
+
+                    lineStartIndex.push_back(i + 1);
+                }
+            }
+        }
 
     public:
         bool read = false;
@@ -37,7 +60,12 @@ namespace Fig
                 source += line + '\n';
                 lines.push_back(String(line));
             }
+            if (lines.empty())
+            {
+                lines.push_back(String()); // 填充一个空的
+            }
             read = true;
+            preprocessLineIndices();
             return source;
         }
 
@@ -49,7 +77,7 @@ namespace Fig
             return _line <= lines.size() && _line >= 1;
         }
 
-        String GetLine(size_t _line) const
+        const String &GetLine(size_t _line) const
         {
             assert(_line <= lines.size() && "SourceManager: GetLine failed, index out of range");
             return lines[_line - 1];
@@ -64,5 +92,36 @@ namespace Fig
         {
             return source;
         }
+
+        std::pair<size_t, size_t> GetLineColumn(size_t index) const
+        {
+            if (lineStartIndex.empty())
+            {
+                return {1, 1};
+            }
+
+            // clamp index 到合法范围（Parser报错可能传入EOF位置）
+            // size_t lastLine = lineStartIndex.size() - 1;
+            if (index < lineStartIndex[0])
+            {
+                return {1, 1};
+            }
+
+            // upper_bound 找到第一个 > index 的行起点
+            auto it = std::ranges::upper_bound(lineStartIndex.begin(), lineStartIndex.end(), index);
+
+            size_t line;
+            if (it == lineStartIndex.begin())
+            {
+                line = 0;
+            }
+            else
+            {
+                line = static_cast<size_t>(it - lineStartIndex.begin() - 1);
+            }
+
+            size_t column = index - lineStartIndex[line] + 1;
+            return {line + 1, column};
+        }
     };
 };