feat(furc): implement lexer

furc/src/front/lexer.cpp

@@ -0,0 +1,154 @@
+#include "furc/front/lexer.hpp"
+
+#include <cctype>
+#include <string_view>
+#include <unordered_map>
+
+namespace furc {
+
+token lexer::next_token() {
+    if (m_peekToken.has_value()) {
+        auto tok    = m_peekToken.value();
+        m_peekToken = {};
+        return tok;
+    }
+
+    skip_spaces();
+
+    if (m_cursor >= m_content.size()) return { location(), token::EndOfFile };
+
+    auto loc = location();
+
+    if (std::isdigit(get()) != 0) {}
+
+    if (std::isalnum(get()) != 0 || get() == '_') {
+        std::size_t begin = m_cursor;
+        next();
+        while (m_cursor < m_content.size() && (std::isalnum(get()) != 0 || get() == '_'))
+            next();
+        return { loc, token::Identifier, m_content.substr(begin, m_cursor - begin) };
+    }
+
+    if (get() == '"') {
+        next();
+
+        std::size_t begin = m_cursor;
+        while (m_cursor < m_content.size() && get() != '"')
+            next();
+        if (m_cursor >= m_content.size()) return { location(), token::UnexpectedEOF };
+
+        next();
+        return { loc, token::String, m_content.substr(begin, m_cursor - begin - 1) };
+    }
+
+    if (get() == '\'') {
+        next();
+        bool slash = get() == '\\';
+        if (slash) next();
+        auto loc2      = location();
+        char character = get();
+        next();
+        if (get() != '\'') return { location(), token::UnexpectedCharacter, get() };
+        next();
+        if (slash) {
+            switch (character) {
+            case '\\': character = '\\'; break;
+            case 'n': character = '\n'; break;
+            case 'r': character = '\r'; break;
+            case 't': character = '\t'; break;
+            default: return { loc2, token::UnexpectedCharacter, character };
+            }
+        }
+        return { loc, token::Char, character };
+    }
+
+    static std::unordered_map<std::string_view, token_t> s_tokens = {
+        { "(", token::LParen },
+        { ")", token::RParen },
+        { "{", token::LBrace },
+        { "}", token::RBrace },
+        { "[", token::LBracket },
+        { "]", token::RBracket },
+        { ";", token::Semicolon },
+        { ":", token::Colon },
+        { ",", token::Comma },
+        { ".", token::Dot },
+        { "+", token::Plus },
+        { "-", token::Minus },
+        { "*", token::Star },
+        { "/", token::Slash },
+        { "%", token::Percent },
+        { "&", token::Ampersand },
+        { "|", token::Pipe },
+        { "^", token::Hat },
+        { "&&", token::DblAmpersand },
+        { "||", token::DblPipe },
+        { "++", token::DblPlus },
+        { "--", token::DblMinus },
+        { "!", token::ExMark },
+        { "^^", token::CatEars },
+        { "=", token::Equals },
+        { "+=", token::PlusEquals },
+        { "-=", token::MinusEquals },
+        { "*=", token::StarEquals },
+        { "/=", token::SlashEquals },
+        { "%=", token::PercentEquals },
+        { "&=", token::AmpersandEquals },
+        { "|=", token::PipeEquals },
+        { "^=", token::HatEquals },
+        { "==", token::DblEquals },
+        { "!=", token::ExEquals },
+        { "<", token::LessThan },
+        { "<=", token::LessEquals },
+        { ">", token::GreaterThan },
+        { ">=", token::GreaterEquals },
+        { "->", token::SlimArrow },
+        { "=>", token::FatArrow },
+        { "@", token::Monkey },
+        { "#", token::Sha256 },
+    };
+
+    std::size_t begin = m_cursor;
+    std::size_t len   = 1;
+    while (begin + len - 1 < m_content.size() && s_tokens.find(m_content.substr(begin, len)) != s_tokens.end())
+        ++len;
+
+    if (len > 1) {
+        auto type = s_tokens[m_content.substr(begin, len - 1)];
+        m_cursor += len - 1;
+        return { loc, type };
+    }
+
+    return { loc, token::UnexpectedCharacter, get() };
+}
+
+token lexer::peek_token() {
+    if (m_peekToken.has_value()) return m_peekToken.value();
+    auto tok    = next_token();
+    m_peekToken = tok;
+    return tok;
+}
+
+token lexer::skip_token() {
+    m_peekToken = {};
+    return next_token();
+}
+
+void lexer::next() {
+    if (m_cursor < m_content.size()) ++m_cursor;
+}
+
+constexpr char lexer::get(std::size_t offset) const {
+    return m_content[m_cursor + offset];
+}
+
+void lexer::skip_spaces() {
+    while (m_cursor < m_content.size() && std::isspace(get()) != 0)
+        ++m_cursor;
+}
+
+constexpr token::location lexer::location() const {
+    return { m_filepath, m_row, m_cursor - m_lineStart };
+}
+
+} // namespace furc