Bob/source/Interpreter.cpp

//
// Created by Bobby Lucero on 5/27/23.
//
#include <utility>
#include <sstream>
#include <cmath>
#include <iomanip>
#include <limits>
#include "../headers/Interpreter.h"


sptr(Object) Interpreter::visitLiteralExpr(sptr(LiteralExpr) expr) {
    if(expr->isNull) return msptr(None)();
    if(expr->isNumber) return msptr(Number)(std::stod(expr->value));
    return msptr(String)(expr->value);
}

sptr(Object) Interpreter::visitGroupingExpr(sptr(GroupingExpr) expression) {

    return evaluate(expression->expression);
}

sptr(Object) Interpreter::visitUnaryExpr(sptr(UnaryExpr) expression)
{
    sptr(Object) right = evaluate(expression->right);

    if(expression->oper.type == MINUS)
    {
        if(std::dynamic_pointer_cast<Number>(right))
        {
            double value = std::dynamic_pointer_cast<Number>(right)->value;
            return msptr(Number)(-value);
        }
        else
        {
            throw std::runtime_error("Operand must be a number when using: " + expression->oper.lexeme);
        }

    }

    if(expression->oper.type == BANG)
    {
        return msptr(Boolean)(!isTruthy(right));
    }

}

sptr(Object) Interpreter::visitBinaryExpr(sptr(BinaryExpr) expression) 
{
    sptr(Object) left = evaluate(expression->left);
    sptr(Object) right = evaluate(expression->right);

    switch (expression->oper.type) {
        case BANG_EQUAL:
            return msptr(Boolean)(!isEqual(left, right));
        case DOUBLE_EQUAL:
            return msptr(Boolean)(isEqual(left, right));
        default:
            ;
    }

    if(std::dynamic_pointer_cast<Number>(left) && std::dynamic_pointer_cast<Number>(right))
    {
        double left_double = std::dynamic_pointer_cast<Number>(left)->value;
        double right_double = std::dynamic_pointer_cast<Number>(right)->value;
        switch (expression->oper.type) {
            case GREATER:
                return msptr(Boolean)(left_double > right_double);
            case GREATER_EQUAL:
                return msptr(Boolean)(left_double >= right_double);
            case LESS:
                return msptr(Boolean)(left_double < right_double);
            case LESS_EQUAL:
                return msptr(Boolean)(left_double <= right_double);
            case MINUS:
                return msptr(Number)(left_double - right_double);
            case PLUS:
                return msptr(Number)(left_double + right_double);
            case SLASH:
                return msptr(Number)(left_double / right_double);
            case STAR:
                return msptr(Number)(left_double * right_double);
            default:
                return msptr(None)(); //unreachable
        }
    }
    else if(std::dynamic_pointer_cast<String>(left) && std::dynamic_pointer_cast<String>(right))
    {
        std::string left_string = std::dynamic_pointer_cast<String>(left)->value;
        std::string right_string = std::dynamic_pointer_cast<String>(right)->value;
        return msptr(String)(left_string + right_string);
    }
    else
    {
        throw std::runtime_error("Operands must be of same type when using: " + expression->oper.lexeme);
    }

}

sptr(Object) Interpreter::evaluate(sptr(Expr) expr) {
    return expr->accept(this);
}

bool Interpreter::isTruthy(sptr(Object) object) {

    if(auto boolean = std::dynamic_pointer_cast<Boolean>(object))
    {
        boolean->value;
    }

    if(auto obj = std::dynamic_pointer_cast<None>(object))
    {
        return false;
    }

    return true;
}

bool Interpreter::isEqual(sptr(Object) a, sptr(Object) b) {
    if(auto left = std::dynamic_pointer_cast<Number>(a))
    {
        if(auto right = std::dynamic_pointer_cast<Number>(b))
        {
            return left->value == right->value;
        }

        return false;
    }
    else if(auto left = std::dynamic_pointer_cast<Boolean>(a))
    {
        if(auto right = std::dynamic_pointer_cast<Boolean>(b))
        {
            return left->value == right->value;
        }

        return false;
    }
    else if(auto left = std::dynamic_pointer_cast<String>(a))
    {
        if(auto right = std::dynamic_pointer_cast<String>(b))
        {
            return left->value == right->value;
        }

        return false;
    }
    else if(auto left = std::dynamic_pointer_cast<None>(a))
    {
        if(auto right = std::dynamic_pointer_cast<None>(b))
        {
            return true;
        }

        return false;
    }
}

void Interpreter::interpret(std::shared_ptr<Expr> expr) {

    sptr(Object) value = evaluate(std::move(expr));
    std::cout << stringify(value) << std::endl;

}

std::string Interpreter::stringify(std::shared_ptr<Object> object) {
    if(std::dynamic_pointer_cast<None>(object))
    {
        return "None";
    }
    else if(auto num = std::dynamic_pointer_cast<Number>(object))
    {
        double integral = num->value;
        double fractional = std::modf(num->value, &integral);

        std::stringstream ss;
        if(std::abs(fractional) < std::numeric_limits<double>::epsilon())
        {
            ss << std::fixed << std::setprecision(0) << integral;

            return ss.str();
        }
        else
        {
            ss << std::fixed << std::setprecision(std::numeric_limits<double>::digits10) << num->value;\
            std::string str = ss.str();
            str.erase(str.find_last_not_of('0') + 1, std::string::npos);
            if (str.back() == '.') {
                str.pop_back();
            }

            return str;
        }
    }
    else if(auto string = std::dynamic_pointer_cast<String>(object))
    {
        return string->value;
    }
    else if(auto Bool = std::dynamic_pointer_cast<Boolean>(object))
    {
        return Bool->value == 1 ? "true" : "false";
    }
}