beggining to stablish the EBNF of spider assembly

src/spider/compiler/text/TextReader.cpp

@@ -33,7 +33,10 @@ namespace spider {
         // and then do an easy compare!
         std::u32string str;
         if(!utf8::toUTF32(chars, str)) throw std::runtime_error("Specified invalid UTF-8 string!");
+        return eat(str);
+    }
 
+    bool TextReader::eat(const std::u32string& str) {
         // compare now
         isize index;
         for(index = 0; index < str.size(); index++) {
@@ -68,46 +71,37 @@ namespace spider {
     /**
      * Returns the current character.
      */
-    u32 TextReader::current() {
+    optional<u32> TextReader::current() {
         if (bufferIndex < buffer.size()) {
             return buffer[bufferIndex];
         }
-        return 0;
+        return {};
     }
 
     /**
      * Reads the next character and advances the position tracker.
      */
-    u32 TextReader::nextChar(isize n) {
-        if (err) return 0;
-
+    optional<u32> TextReader::nextChar(isize n) {
         // Ensure the character we are moving TO exists
         if (fillBufferTo(n)) {
             // advance n characters
             while(n--) {
-                advance(current());
+                advance(buffer[bufferIndex]);
                 bufferIndex++;
             }
             return current();
         }
-
-        // If we couldn't fill the buffer, we hit EOF
-        eof = true;
-        return 0;
+        return {};
     }
 
     /**
      * Keeps the next n-th character (n = 0 is current).
      */
-    u32 TextReader::peekChar(isize n) {
-        if (err) return 0;
+    optional<u32> TextReader::peekChar(isize n) {
         if (fillBufferTo(n)) return buffer[bufferIndex + n];
-        return 0;
+        return {};
     }
 
-    /**
-     * Clears the buffer from previous characters, keeping current and future ones.
-     */
     void TextReader::commit() {
         if (bufferIndex > 0) {
             // Erase everything before the current buffer index
@@ -116,21 +110,12 @@ namespace spider {
         }
     }
 
-    /**
-     * Rolls back any previous characters within the limits of the uncommitted buffer.
-     */
-    void TextReader::rollback(isize n) {
-        // Prevent rolling back past the start of our committed buffer
-        if (n > bufferIndex) n = bufferIndex;
-
-        // We must track positions backward or recalculate if exact column match is needed.
-        // Assuming simple rollback of the pointer here per definition.
-        bufferIndex -= n;
-        eof = false;
+    isize TextReader::push() {
+        return bufferIndex;
     }
 
-    TextReader::operator bool() const {
-        return !err;
+    void TextReader::pop(isize index) {
+        bufferIndex = std::min(index, bufferIndex);
     }
 
     /**
@@ -191,16 +176,20 @@ namespace spider {
         return true;
     }
 
-    /**
-     * Returns true if the stream is consumed and no elements remain in the read buffer.
-     */
-    bool TextReader::isEOF() {
-        if (err) return false;
+    pos TextReader::getPosition() const {
+        return at;
+    }
+
+    bool TextReader::isEOF() const{
         return eof && bufferIndex >= buffer.size();
     }
 
-    pos TextReader::getPosition() const {
-        return at;
+    bool TextReader::hasError() const{
+        return err;
+    }
+
+    TextReader::operator bool() const {
+        return !isEOF() && !hasError();
     }
 
     std::string TextReader::getError() const {