PorygonLang/src/Parser/Parser.cpp

#include "Parser.hpp"
#include "UnaryOperatorKind.hpp"
#include "BinaryOperatorKind.hpp"


ParsedScriptStatement* Parser::Parse() {
    vector<ParsedStatement*> statements;
    while (true){
        auto next = this -> Next();
        if (next->GetKind() == TokenKind::EndOfFile){
            break;
        }
        if (next->GetKind() == TokenKind::WhiteSpace){
            continue;
        }
        statements.push_back(this -> ParseStatement(next));
    }
    return new ParsedScriptStatement(statements);
}

IToken *Parser::Peek() {
    return this -> _tokens[_position];
}

IToken *Parser::Next() {
    this -> _position++;
    return this -> _tokens[_position - 1];
}

ParsedStatement* Parser::ParseStatement(IToken* current){
    if (current->GetKind() == TokenKind::LocalKeyword){
        return ParseAssignment(current);
    } else if (this->Peek()->GetKind() == TokenKind::AssignmentToken){
        return ParseAssignment(current);
    }
    return new ParsedExpressionStatement(this -> ParseExpression(current));
}

ParsedStatement *Parser::ParseAssignment(IToken *current) {
    bool isLocal = false;
    IToken* identifier;
    if (current -> GetKind() == TokenKind::LocalKeyword){
        isLocal = true;
        identifier = this -> Next();
    } else{
        identifier = current;
    }
    auto assignmentToken = this->Next();
    auto expression = this -> ParseExpression(this -> Next());

    if (identifier -> GetKind() != TokenKind::Identifier){
        this -> ScriptData -> Diagnostics -> LogError(DiagnosticCode::UnexpectedToken, identifier->GetStartPosition(), identifier->GetLength());
        return new ParsedBadStatement(identifier->GetStartPosition(), identifier->GetLength());
    }
    if (assignmentToken -> GetKind() != TokenKind::AssignmentToken){
        this -> ScriptData -> Diagnostics -> LogError(DiagnosticCode::UnexpectedToken, identifier->GetStartPosition(), identifier->GetLength());
        return new ParsedBadStatement(identifier->GetStartPosition(), identifier->GetLength());
    }

    auto start = current -> GetStartPosition();
    return new ParsedAssignmentStatement(isLocal, ((IdentifierToken*)identifier) -> Value, expression, start, expression->GetEndPosition() - start);
}

ParsedExpression* Parser::ParseExpression(IToken* current){
    return this -> ParseBinaryExpression(current, OperatorPrecedence::No);
}

OperatorPrecedence GetUnaryPrecedence(TokenKind kind){
    switch (kind){
        case TokenKind::PlusToken:
        case TokenKind::MinusToken:
        case TokenKind::NotKeyword:
            return OperatorPrecedence::Unary;
        default:
            return OperatorPrecedence::No;
    }
}

UnaryOperatorKind GetUnaryOperatorKind(TokenKind kind){
    switch (kind){
        case TokenKind::PlusToken: return UnaryOperatorKind::Identity;
        case TokenKind::MinusToken: return UnaryOperatorKind::Negation;
        case TokenKind::NotKeyword: return UnaryOperatorKind::LogicalNegation;
        default: // This should never trigger, so throw.
            throw;
    }
}

BinaryOperatorKind GetBinaryOperatorKind(TokenKind kind){
    switch (kind){
        case TokenKind::PlusToken: return BinaryOperatorKind ::Addition;
        case TokenKind::MinusToken: return BinaryOperatorKind ::Subtraction;
        case TokenKind::StarToken: return BinaryOperatorKind ::Multiplication;
        case TokenKind::SlashToken: return BinaryOperatorKind ::Division;
        case TokenKind::EqualityToken: return BinaryOperatorKind ::Equality;
        case TokenKind::InequalityToken: return BinaryOperatorKind ::Inequality;
        case TokenKind::AndKeyword: return BinaryOperatorKind ::LogicalAnd;
        case TokenKind::OrKeyword: return BinaryOperatorKind ::LogicalOr;
        default: // This should never trigger, so throw.
            throw;
    }
}

OperatorPrecedence GetBinaryPrecedence(TokenKind kind){
    switch (kind){
        case TokenKind::PlusToken: return OperatorPrecedence ::Additive;
        case TokenKind::MinusToken: return OperatorPrecedence ::Additive;
        case TokenKind::StarToken: return OperatorPrecedence ::Multiplication;
        case TokenKind::SlashToken: return OperatorPrecedence ::Multiplication;
        case TokenKind::EqualityToken: return OperatorPrecedence ::Equality;
        case TokenKind::InequalityToken: return OperatorPrecedence ::Equality;
        case TokenKind::AndKeyword: return OperatorPrecedence ::LogicalAnd;
        case TokenKind::OrKeyword: return OperatorPrecedence ::LogicalOr;
        default:
            return OperatorPrecedence::No;
    }
}

ParsedExpression* Parser::ParseBinaryExpression(IToken* current, OperatorPrecedence parentPrecedence){
    OperatorPrecedence unaryPrecedence = GetUnaryPrecedence(current -> GetKind());
    ParsedExpression* left;
    if (unaryPrecedence != OperatorPrecedence::No && unaryPrecedence >= parentPrecedence){
        UnaryOperatorKind operatorKind = GetUnaryOperatorKind(current -> GetKind());
        auto next = this -> Next();
        auto operand = this -> ParseBinaryExpression(next, unaryPrecedence);
        auto startPos = current -> GetStartPosition();
        left = new UnaryExpression(operatorKind, operand, startPos, operand -> GetEndPosition() - startPos);
    } else{
        left = this -> ParsePrimaryExpression(current);
    }
    while (true){
        auto next  = this -> Peek();
        OperatorPrecedence binaryPrecedence = GetBinaryPrecedence(next -> GetKind());
        if (binaryPrecedence == OperatorPrecedence::No || binaryPrecedence <= parentPrecedence){
            break;
        }
        auto operatorKind = GetBinaryOperatorKind(next -> GetKind());
        this -> Next();
        auto right = this -> ParseBinaryExpression(this -> Next(), binaryPrecedence);
        auto startPos = left -> GetStartPosition();
        left = new BinaryExpression(operatorKind, left, right, startPos, right -> GetEndPosition() - startPos);
    }
    return left;
}

ParsedExpression *Parser::ParsePrimaryExpression(IToken *current) {
    switch (current -> GetKind()){
        case TokenKind ::Integer: return new LiteralIntegerExpression((IntegerToken*)current);
        case TokenKind ::Float: return new LiteralFloatExpression((FloatToken*)current);
        case TokenKind ::String: return new LiteralStringExpression((StringToken*)current);
        case TokenKind ::TrueKeyword: return new LiteralBoolExpression(current);
        case TokenKind ::FalseKeyword: return new LiteralBoolExpression(current);
        case TokenKind ::Identifier: return new VariableExpression((IdentifierToken*)current);
        case TokenKind ::OpenParenthesis: return this -> ParseParenthesizedExpression(current);
        // If we find a bad token here, we should have already logged it in the lexer, so don't log another error.
        case TokenKind ::BadToken: return new BadExpression(current->GetStartPosition(), current->GetLength());
        default:
            this -> ScriptData -> Diagnostics -> LogError(DiagnosticCode::UnexpectedToken, current->GetStartPosition(), current->GetLength());
            return new BadExpression(current->GetStartPosition(), current->GetLength());
    }
}

ParsedExpression *Parser::ParseParenthesizedExpression(IToken *current) {
    auto next = this -> Next();
    auto expression = this -> ParseExpression(next);
    auto closeToken = this -> Next();
    if (closeToken -> GetKind() != TokenKind::CloseParenthesis){
        this -> ScriptData -> Diagnostics -> LogError(DiagnosticCode::UnexpectedToken, closeToken->GetStartPosition(), closeToken->GetLength());
        return new BadExpression(closeToken->GetStartPosition(), closeToken->GetLength());
    }
    auto start = current -> GetStartPosition();
    return new ParenthesizedExpression(expression, start, closeToken->GetEndPosition() - start);
}