#include "scriptengine.h"
#include "lexer.h"
#include "parser.h"
#include "expression.h"

#include <bu/staticmembuf.h>
#include <bu/exceptionbase.h>

ScriptEngine::ScriptEngine()
{
}

ScriptEngine::~ScriptEngine()
{
}

Number ScriptEngine::exec( const Bu::String &sExpr )
{
    Bu::StaticMemBuf mb( sExpr.getStr(), sExpr.getSize() );
    return exec( sExpr );
}

Number ScriptEngine::exec( Bu::Stream &sInput )
{
    Lexer l( sInput );
    Parser p( l );
    Expression *pExp = p.parse();
    Number n = exec( pExp );
    delete pExp;
    return n;
}

Number ScriptEngine::exec( Expression *pExpr )
{
    NumStack sNums;

    for( Expression::iterator i = pExpr->begin(); i; i++ )
    {
        switch( (*i).eType )
        {
            case Token::tNumber:
                sNums.push( *(*i).nVal );
                break;

            case Token::tVariable:
                if( hVarState.has( *(*i).sVal ) )
                {
                    sNums.push( hVarState[*(*i).sVal] );
                }
                else
                {
                    throw Bu::ExceptionBase(
                        Bu::String("No such variable: $%1").arg(*(*i).sVal).end().getStr()
                        );
                }
                break;

            case Token::tPlus:
                {
                    Number b = sNums.peekPop();
                    Number a = sNums.peekPop();
                    sNums.push( a + b );
                }
                break;

            case Token::tMinus:
                {
                    Number b = sNums.peekPop();
                    Number a = sNums.peekPop();
                    sNums.push( a - b );
                }
                break;

            case Token::tDivide:
                {
                    Number b = sNums.peekPop();
                    Number a = sNums.peekPop();
                    sNums.push( a / b );
                }
                break;

            case Token::tMultiply:
                {
                    Number b = sNums.peekPop();
                    Number a = sNums.peekPop();
                    sNums.push( a * b );
                }
                break;

            case Token::tNegate:
                sNums.push( -sNums.peekPop() );
                break;
        }
    }

    return sNums.peekPop();
}