#ifndef PARSER_H
#define PARSER_H

#include <bu/list.h>
#include <bu/hash.h>
#include "token.h"
#include "number.h"

namespace Bu
{
    class Stream;
};

class Lexer;

/**
 *
 * expr: literal
 *     | variable
 *     | expr '+' expr
 *     | expr '-' expr
 *     | expr '*' expr
 *     | expr '/' expr
 *     | '(' expr ')'
 *     | '-' expr
 *     | variable '=' expr
 *     ;
 *
 * -----
 * 
 * expr': literal
 *      | variable
 *      | '(' expr ')'
 *      | '-' expr'
 *      ;
 *
 * expr: expr' '+' expr
 *     | expr' '-' expr
 *     | expr' '*' expr
 *     | expr' '/' expr
 *     | expr'
 *     | variable '=' expr
 *     ;
 */
class Parser
{
public:
    Parser( Lexer &lex, Bu::Stream &rOut );
    virtual ~Parser();

    void parse();
    Number getVariable( const Bu::String &sName );
    void setVariable( const Bu::String &sName, const Number &rValue );

private:
    void expr();
    void exprP();

private:
    void unwind();
    int reqTokens( Token::Type eType );
    int getPriority( Token::Type eType );
    Number &deref( Token &t );

private:
    Lexer &lex;
    Bu::Stream &rOut;
    typedef Bu::List<Token> TokenStack;
    typedef Bu::Hash<Bu::String, Number> VarHash;
    TokenStack tsStack;
//    TokenStack tsNonTerminal;
    Number nZero;
    VarHash hVars;
};

#endif