newsolstice/src/parser/parser.cpp

#include "parser.hpp"
#include <stdexcept>
#include <unordered_map>

using TT = Solstice::TokenType;

namespace Solstice {

    std::unordered_map<TokenType, NodeType> tokToNodeType = {
        {TT::Math_Add, NodeType::Add},
        {TT::Math_Subtract, NodeType::Subtract},
        {TT::Math_Multiply, NodeType::Multiply},
        {TT::Math_Divide, NodeType::Divide},
        {TT::Comparison_Equal, NodeType::Equal},
        {TT::Comparison_NotEqual, NodeType::NotEqual},
        {TT::Comparison_GreaterThan, NodeType::GreaterThan},
        {TT::Comparison_LesserThan, NodeType::LesserThan},
    };

    std::optional<Token> Parser::peek(int64_t ahead) {
        if (current + ahead >= input.size() || current + ahead < 0) {
            return {};
        }
        return input[current + ahead];
    }

    std::optional<Token> Parser::consume() {
        if (current >= input.size()) {
            return {};
        }
        return input[current++];
    }

    std::optional<Node> Parser::getPreviousNode(Node& parent) {
        if (parent.children.empty()) {
            return {};
        }
        Node node = parent.children[parent.children.size() - 1];
        parent.children.pop_back();
        return node;
    }

    Node Parser::parseExpr(TT type) {
        auto left = getPreviousNode(output);
        if (!left.has_value()) {
            throw std::runtime_error("Expecting expression on left of '+'");
        }
        consume(); // be rid of the +
        Precedence precedence = getTokenPrecedence(Token(type));
        auto right = parseOneNode(precedence);
        if (!right.has_value()) {
            throw std::runtime_error("Expecting expression on right of '+'");
        }

        NodeType nodeType;
        if (tokToNodeType.find(type) == tokToNodeType.end()) {
            throw std::runtime_error("FIXME couldn't map token type to node type");
        } else {
            nodeType = tokToNodeType[type];
        }

        return Node(nodeType, {*left, *right});    
    }

    Node Parser::parseLiteral() {
        auto current = peek(-1);
        if (!current.has_value()) {
            throw std::runtime_error("FIXME couldn't get current token");
        }
        auto literal = current->getLiteral();
        if (!literal.has_value()) {
            throw std::runtime_error("FIXME token with type literal does not hold a literal");
        }

        return Node(*literal);
    }

    Node Parser::parseIdentifier() {
        auto current = peek(-1);
        if (!current.has_value()) {
            throw std::runtime_error("FIXME couldn't get current token");
        }
        auto id = current->getIdentifier();
        if (!id.has_value()) {
            throw std::runtime_error("FIXME token with type identifier does not hold an identifier");
        }

        return Node(*id);
    }

    Precedence Parser::getTokenPrecedence(const Token& token) {
        static size_t braceCount = 0;
        static size_t bracketCount = 0;
        static size_t spikyBracketCount = 0;
        switch (token.type) {
            case TT::OpenCurly: {
                braceCount++;
                return Precedence::Other;
            }
            case TT::CloseCurly: {
                braceCount--;
                return Precedence::Other;
            }
            case TT::OpenSpiky: {
                spikyBracketCount++;
                return Precedence::Other;
            }
            case TT::CloseSpiky: {
                spikyBracketCount--;
                return Precedence::Other;
            }
            case TT::OpenParen: {
                bracketCount++;
                return Precedence::Other;
            }
            case TT::CloseParen: {
                bracketCount--;
                return Precedence::Other;
            }
            default: break;
        }
        if (braceCount > 0) {
            return Precedence::Other;
        }
        if (bracketCount > 0) {
            return Precedence::Other;
        }
        if (spikyBracketCount > 0) {
            return Precedence::Other;
        }
        switch (token.type) {
            case TT::None:
            case TT::Kw_Type:
            case TT::Hash_CImport: 
            case TT::Hash_Effect:
            case TT::Action_Function:
                return Precedence::Other;
            case TT::Math_Add:
            case TT::Math_Subtract:
                return Precedence::Add;
            case TT::Math_Multiply:
            case TT::Math_Divide:
                return Precedence::Multiply;
            case TT::Assign_Bind:
            case TT::Assign_Set:
            case TT::Assign_Type:
                return Precedence::Set;
            case TT::NewLine:
                return Precedence::NewLine;
            case TT::Identifier:
                return Precedence::Identifier;
            case TT::Literal:
                return Precedence::Identifier;
            default: 
                return Precedence::Other;
        }
    }

    std::optional<Node> Parser::parseOneNode(Precedence precedence) {
        auto next = peek();
        if (!next.has_value()) {
            return {};
        }
        if (getTokenPrecedence(*next) >= precedence) {
            return {};
        }
        consume();
        switch (next->type) {
            case TT::None: break;
            case TT::Identifier:
                return parseIdentifier();
            case TT::Literal: 
                return parseLiteral();
            case TT::Math_Add:
            case TT::Math_Subtract:
            case TT::Math_Multiply:
            case TT::Math_Divide:
                return parseExpr(next->type);
        }
        throw std::runtime_error("FIXME: unimplemented parsing case");
    }

    const Node& Parser::parse() {
        while (auto node = parseOneNode(Precedence::Root)) {
            output.children.push_back(*node);
        }

        return output;
    }
}