Building a Programming Language: Part II (Adding Conditions, Loop and Blocks to BrainLess)

/*
Author : Shakti Misra
All are welcome to use these files, distribute, modify and release. But This notice should be included.
This software is given as is, for use and modification.
*/

#include "Interpreter.h"

#define START_RESTORE_PT( a ) const long a( m_lex.setRestorePoint() )
#define END_RESTORE_PT( a ) 

void Interpreter::interpreteScript()//Main routine to start script interpretation. this is semantic analysis or meaning findout method.
{
    m_lex.getNextToken();
    while( eTokenOver != m_lex.getCurrentToken() )
    {enmTokens tok = m_lex.getCurrentToken();//shakti del
        Sentence();
    }
}

void Interpreter::Block()
{
    /*
    A block is of the form #B(BlockName)[BlockContent]
    */
    char szBlockName[ARR_SIZE_128] = {0};

    if(eLeftParen == m_lex.getNextToken())
    {
        int iIndex = 0;

        while( (eCharVal == m_lex.getNextToken()) && (iIndex < ARR_SIZE_128) )
        {
            szBlockName[iIndex++] = (char)m_lex.getAttribVal();
        }

        if((iIndex > ARR_SIZE_128) || isBlankOrNull(szBlockName))
        {
            printf("invalid block name [%s]", szBlockName);//TODO proper error handling
        }
    }
}

void Interpreter::Sentence()
{
/*    while(eTokenOver != m_lex.getNextToken())
    {*/enmTokens tok = m_lex.getCurrentToken();//shakti del
        switch(m_lex.getCurrentToken())
        {//Based on the tokens choose the path.
        case eRdAndStrVal:
            m_tapeVirtualMachine.getCharAndStore();break;
        case eCharVal:break;//TODO
/*        case eBackSlash:
            compareWithNext();break;
            */
        case eDspCurVal:
            m_tapeVirtualMachine.displayChar();break;
        case eIncrContent:
            m_tapeVirtualMachine.incrementContent();break;
        case eDecrContent:
            m_tapeVirtualMachine.decrementContent();break;
        case eAddWithNext:
            m_tapeVirtualMachine.addWithNext();break;
        case eSubNext:
            m_tapeVirtualMachine.substractFromNext();break;
        case eStarChar:
            m_tapeVirtualMachine.moveHeadForeward();break;
        case eLeftAngleBracket:
            m_tapeVirtualMachine.moveHeadBackward();break;
        case eLessThan:// \<
        case eGreaterThan:// \>
        case eEquality:// \=
            compareWithNextBoolean();break;
        case eCompareGeneral://\<>
            compareWithNext();break;
        case eExclaimationMark:
            intDisplayContent();break;
        case eIF://IF(\<)[]FI
            IFBlock();break;
        case eBlock://#B(BlockName)[]
            Block();break;
        case eDO://DO()
            DOLoop();break;
        default:
            exit(0);break;//TODO error handling
        }
        m_lex.getNextToken();//Advance the token
    /*}*/
}

void Interpreter::DOLoop()
{
    if(m_lex.getNextToken() == eLeftParen)
    {
        const long resStartPoint( m_lex.setRestorePoint() );
        m_lex.getNextToken();
        long resEndPoint(-666);//Making it to some imaginary negative number. Else it will be again set when EOF is found.
        enmTokens tok = m_lex.getCurrentToken();//Shakti del
        while( 
            (!(HEX_1 ^ m_tapeVirtualMachine.getFlagRegister()))
            )
        {
            while(
                (m_lex.getCurrentToken() != eTokenOver)/* &&
                (m_lex.getCurrentToken() != eRightParen)*/
                )
            {   tok = m_lex.getCurrentToken();//shakti del
                Sentence();
                tok = m_lex.getCurrentToken();//shakti del
                if(m_lex.getCurrentToken() == eRightParen)
                {
                    if(-666 == resEndPoint)
                        resEndPoint = m_lex.setRestorePoint();
                    break;
                }
            }
            m_lex.positionToRestorePoint(resStartPoint);
            tok = m_lex.getNextToken();//Shakti del tok only
        }

        m_lex.positionToRestorePoint(resEndPoint);
    }
}

void Interpreter::intDisplayContent()
{   //When we are in this function we know that it was due to ![eExclaimationMark] that this function is called.
    //So check for eLeftSqrParen eIntNumber eRightSqrParen structure.
    switch(m_lex.getNextToken())//The tokens group eExclaimationMark eLeftSqrParen eIntNumber eRightSqrParen is a valid token.
    {
    case eLeftSqrParen:
        int len(0);
        if(eIntNumber == m_lex.getNextToken())
        {
           len = (int)m_lex.getAttribVal();
        }
        if(eRightSqrParen == m_lex.getNextToken())
        {
            m_tapeVirtualMachine.displayMultiChar(len);
        }
    }
}

void Interpreter::compareWithNextBoolean()
{
    compareWithNext();
    
    const ulong flagVal = m_tapeVirtualMachine.getFlagRegister();
    bool valSet = false;

    switch( m_lex.getCurrentToken() )
    {
    case eLessThan:
        if(!(flagVal ^ HEX_1))
        {
            m_tapeVirtualMachine.setFlagRegister(HEX_1);
            valSet = true;
        }
        break;
    case eGreaterThan:
        if(!(flagVal ^ HEX_2))
        {
            m_tapeVirtualMachine.setFlagRegister(HEX_1);
            valSet = true;
        }
        break;
    case eEquality:
        if(!(flagVal ^ HEX_3))
        {
            m_tapeVirtualMachine.setFlagRegister(HEX_1);
            valSet = true;
        }
        break;
    }

    if( !valSet )
    {
        m_tapeVirtualMachine.setFlagRegister(HEX_0);
    }
}

void Interpreter::IFBlock()
{
    if(eLeftParen == m_lex.getNextToken())
    {
        switch(m_lex.getNextToken())
        {
        case eLessThan:// \<
        case eGreaterThan:// \>
        case eEquality:// \=
            compareWithNextBoolean();
            if( (m_lex.getNextToken() == eRightParen) && (m_lex.getNextToken() == eLeftSqrParen) )
            {
                const ulong val = m_tapeVirtualMachine.getFlagRegister();//shakti del
                enmTokens tok = m_lex.getNextToken();//shakti del tok
                do
                {tok = m_lex.getCurrentToken();//Shakti del
                    
                    if(!(HEX_1 ^ m_tapeVirtualMachine.getFlagRegister()))
                    {
                        Sentence();
                    }
                    else/* if(HEX_1 & m_tapeVirtualMachine.getFlagRegister())*/
                    {
                        ;//NULL while to eat up all characters till we get ]. NULL Statement()
                    }
                }while( (m_lex.getNextToken() != eFI) && (m_lex.getCurrentToken() != eTokenOver) );
            }
            else
            {
                //set error TODO
            }
            break;
        default:
            //set error TODO
            break;
        }
    }
    else
    {
        //set error - TODO
    }
}

void Interpreter::compareWithNext()
{
    if(m_tapeVirtualMachine.getCurrentHeadValue() < m_tapeVirtualMachine.getNthPosValFrmHead(1))
    {
        m_tapeVirtualMachine.setFlagRegister(HEX_1);
    }
    else if(m_tapeVirtualMachine.getCurrentHeadValue() > m_tapeVirtualMachine.getNthPosValFrmHead(1))
    {
        m_tapeVirtualMachine.setFlagRegister(HEX_2);
    }
    else
    {
        m_tapeVirtualMachine.setFlagRegister(HEX_3);
    }
}

bool Interpreter::isBlankOrNull(const char* str)
{
    //For now only check string len, TODO check for blank too
    return (strlen(str) > 0)? true : false;
}