#ifndef Basic_h
#define Basic_h
#include "Stack.h"

#define KEYWORDCOUNT 3
#define OPCOUNT 15
#define STATEMENTCOUNT 11
#define TOKENCOUNTLIMIT 30
#define STRINGMAX 133

enum Tokens {
  REM = 1,
  LET,
  INPT,
  PRINT,
  IF,
  THEN,
  FOR,
  TO,
  NEXT,
  GOTO,
  END,
  LEFTPAREN, // order in sequence of (, +, -, * and / is required
  PLUS,      // as a proxy for arithmetic precedence
  MINUS,
  MULTIPLY,
  DIVIDE,
  RIGHTPAREN,
  CONCAT,
  EQ,
  NEQ,
  LT,
  GT,
  NUMCONST,
  INT,
  STRING,
  LITERAL,
  LTEQ,
  GTEQ,
  AND,
  OR,
  GOSUB,
  RETURN,
  STEP,
  ERRORTOKEN
};
enum reserved {
  LEN,
  WHILE,
  WEND,
  DO,
  UNTIL,
  COLON,
  MOD,
  COMMA,
  FLOAT,
  STOP,
  RESUME,
  ELSE,
  ENDIF,
  PRINTLN
  // and maybe functions like
  //,RND(),
  //ASC(),
  //VAL(),
  //NUM$()
  //LEFT$()
  //RIGHT$()
  //MID$()
};
enum statItemTypes {
  JUMP,
  INTVAR,
  STRVAR,
  OPERATOR,
  ARITHOP,
  INTCONST,
  STATEMENT,
  LITSTR
};

class Basic{
  public:
    Basic();
    void userInput(char *uLine);
    int parseLine(char *pLine);
    int executeLine();
    void setForRun();
    int rStatus;
    enum {
      USER,
      RUN,
      WAIT,
      STOPPED
    };
  private:
    byte getStatement();
    byte getNextToken(bool);
    void initVars();
    void clearStatement();
    void* storeString(char*);
    void intToString(int, char*);
    int intArith(int, int, int);
    int evalInt(int, int);
    void evalString(int, int, char*);
    bool evalCondition(int, int);
    bool partOfIntExp(int);
    int validateStatement(int, int);
    int validateExp(int, int);
    int getTokenPos(int, int);
    void diagPrintStack(); // diagnostic use
    char *userValue, *pptr, *nptr;
    struct keyword {
      const char* keyword;
      byte token;
    };
    struct forVars {
      short nextLine;
      int forVar;
      int toVal;
      int stepVal;
    };
    Stack<forVars> forStack;
    Stack<short> gosubStack;
    struct condItem {
      int type;
      union {
        bool truth;
        char *strLoc;
        int intVal;
      };
    };
    bool compArgs(int, condItem, condItem);
    struct statItem {
      int sType;
      union {
        byte token;
        int intVal;
        void * varLoc;
      };
    };
    int statItemCount;
    statItem statItems[TOKENCOUNTLIMIT];
    int errCode;
    const keyword statements[STATEMENTCOUNT] = {
      {"LET", LET},
      {"INPUT", INPT},
      {"PRINT", PRINT},
      {"GOTO", GOTO},
      {"IF", IF},
      {"END", END},
      {"REM", REM},
      {"FOR", FOR},
      {"NEXT", NEXT},
      {"GOSUB", GOSUB},
      {"RETURN", RETURN}
    };
    const keyword keywords[KEYWORDCOUNT] = {
      {"THEN", THEN},
      {"TO", TO},
      {"STEP", STEP}
    };
    const keyword operators[OPCOUNT] = {
      {"=", EQ},
      {"+", PLUS},
      {"-", MINUS},
      {"*", MULTIPLY},
      {"/", DIVIDE},
      {"&", CONCAT},
      {"(", LEFTPAREN},
      {")", RIGHTPAREN},
      {"<>", NEQ}, // <>, ,<= and >= must come before > and <
      {"<=", LTEQ},
      {">=", GTEQ},
      {">", GT},
      {"<", LT},
      {"AND", AND},
      {"OR", OR}
    };
    int intVars[26]; // integer variable A% through Z%
    void* stringVars[26]; // pointers to string variables A$ through Z$
    byte statType;
};
extern Basic basic;
#endif