// Created by Jared Bruni on 7/14/13.
// Handwritten Scanner, Parser for a simple Calculator
// handles simple expressions
// remember to end statements with a semi-colon

#ifndef lexer_lexer_h
#define lexer_lexer_h

#include<iostream>
#include<vector>
#include<cstdlib>
#include<unordered_map>

namespace lex {

    enum Token_type { TOKEN_NOTHING=0, TOKEN_CHAR, TOKEN_WHITESPACE, TOKEN_STRING, TOKEN_DIGIT, TOKEN_OPERATOR, TOKEN_IDENTIFIER, TOKEN_PRINT, TOKEN_EOF };
    class Scanner_EOF {};
    class Scanner_Error {
    public:
        Scanner_Error(std::string value) : error_text{value} { }
        std::string error_text;
    };
    class Exit_Exception {};

    class Token {
    public:
        Token() {}
        Token(std::string txt, Token_type t) : text(txt), type(t), line(0), offset(0) {}
        std::string getToken() const { return text; }
        Token_type getType() const { return type; }
        
        Token &operator=(const Token &t) {
            setToken(t);
            return *this;
        }
        
        bool operator==(const Token &t) {
            if(text == t.text && type == t.type)
                return true;
            return false;
        }
        
        void setToken(const std::string &txt, Token_type t, unsigned int coffset, unsigned int cline) {
            text = txt;
            type = t;
            offset = coffset;
            line = cline;
            
        }
        void setToken(const Token &t) {
            text = t.text;
            type = t.type;
            offset = t.offset;
            line = t.line;
        }
        
        friend std::ostream &operator<<(std::ostream &, const Token &);
        
    private:
        std::string text;
        Token_type type;
        unsigned int line, offset;
        
    };
    
    class Token_map {
    public:
        unsigned char token_map[256] = { TOKEN_NOTHING };
        
        Token_map() {
            signed int i;
            for(i = 0; i < 0xFF; ++i)
                if(isOperator(i) == true)
                    token_map[i] = TOKEN_OPERATOR;
                else
                    token_map[i] = TOKEN_NOTHING;
            
            for(i = 'a'; i <= 'z'; ++i)
                token_map[i] = TOKEN_CHAR;
            for(i = 'A'; i <= 'Z'; ++i)
                token_map[i] = TOKEN_CHAR;
            
            setToken('_', TOKEN_CHAR);
            
            for(i = '0'; i <= '9'; ++i)
                token_map[i] = TOKEN_DIGIT;
            
            setToken(' ', TOKEN_WHITESPACE);
            setToken('\t', TOKEN_WHITESPACE);
        }

        void setToken(signed int pos, Token_type token) {
            token_map[pos] = token;
        }
        
        
        
        unsigned char &operator[](char pos) {
            return token_map[static_cast<int>(pos)];
        }
        
        bool isOperator(char c) {
            switch(c) {
                    case ';':
                    case ':':
                    case '.':
                    case '-':
                    case '(':
                    case ')':
                    case '[':
                    case ']':
                    case '{':
                    case '}':
                    case '!':
                    case '@':
                    case '#':
                    case '$':
                    case '%':
                    case '^':
                    case '&':
                    case '*':
                    case '=':
                    case '+':
                    case '~':
                    case '\"':
                    case '\'':
                    case '`':
                    case ',':
                    case '\\':
                    case '/':
                    case '<':
                    case '>':
                    return true;
            }
            return false;
        }
    
    };

    class LexInput {
    private:
        bool owns;
        static Token_map token_map;
    public:
         LexInput(std::istream *s) : owns(true), input(s), offset(0), line(1) {
            initMap();
        }
        LexInput(std::istream &s) : owns(false), input(&s), offset(0), line(1) {
            initMap();
        }
        
        ~LexInput() {
            if(owns)
                delete input;
        }
        
     
        
        void initMap() {

        }
        
        Token_type characterToType(const unsigned char &c) {
            return static_cast<Token_type>(token_map[c]);
        }
        
        unsigned char getChar() {
            ++offset;
            current = input->get();
            if(current == '\n') { ++line; offset = 0; return getChar(); }
            if(*input) return current;
            return 0;
        }
        
        const unsigned char &curChar() const { return current; }

        void putBack(const unsigned char &c) {
            input->putback(c);
        }
        
        Token GetToken() {
            Token tok;
            unsigned char c;
            
            if(input && input->eof()) {
              //  throw Scanner_EOF();
                tok = Token("", TOKEN_EOF);
                return tok;
            }
            
            c = getChar();
            
            
            if(c == 0) return Token("", TOKEN_EOF);
            
            
            Token_type type = characterToType(c);
            
            switch(type) {
                case TOKEN_WHITESPACE: {
                    unsigned char cc = c;
                    
                    while(cc == ' ' || cc =='\r' || cc == '\t') {
                        cc = getChar();
                    }
                    
                    putBack(cc);
                    return GetToken();
                }
                    break;
                case TOKEN_DIGIT:
                    GetDigitToken(tok);
                    break;
                case TOKEN_STRING:
                    GetStringToken(tok);
                    break;
                case TOKEN_CHAR:
                    GetIdToken(tok);
                    break;
                case TOKEN_OPERATOR:
                    GetOperatorToken(tok);
                    break;
                case TOKEN_NOTHING:
                    std::cout << "Warning unrecognized character: " << c << "\n";
                    return GetToken();
                    break;
                default:
                    break;
            }
            ctoken = tok;
            return tok;
        }
        
        bool valid() {
            if(input != nullptr && *input)
                return true;
            return false;
        }
        
        Token &GetCurrent() {
            return ctoken;
        }
  
    private:
        std::istream *input;
        unsigned int offset, line;
        unsigned char current;
        Token ctoken;
        
        void GetDigitToken(Token &token) {
            std::string tok;
            unsigned char cc = curChar();
            unsigned int sline = line, soffset = offset;
            signed int count = 0;
            bool trunc = false;
            while((characterToType(cc) == TOKEN_DIGIT) || cc == '.') {
                if(cc == '.') ++count;
                if(count < 2)
                tok += cc;
                else { trunc = true; }
                cc = getChar();
            }
            if(characterToType(cc) !=  TOKEN_CHAR)
            putBack(cc);
            if(trunc == true) std::cout << tok << " truncated.\n";
            token.setToken(tok, TOKEN_DIGIT, soffset, sline);
        }
        
        void GetIdToken(Token &token) {
            std::string tok;
            unsigned char cc = curChar();
            unsigned int sline = line, soffset = offset;
            Token_type ccType = characterToType(cc);
            while((ccType == TOKEN_CHAR)||(ccType == TOKEN_DIGIT)) {
                tok += cc;
                cc = getChar();
                ccType = characterToType(cc);
            }
            putBack(cc);
            token.setToken(tok, TOKEN_CHAR, soffset, sline);
         }
        
        void GetStringToken(Token &token) {
            
        }
        
        void GetOperatorToken(Token &token) {
            unsigned char cc = curChar();
            unsigned int sline = line, soffset = offset;
            std::string tok;
            tok += cc;
            unsigned char oc = cc;
            cc = getChar();
            if(oc == cc && (cc != '{' && cc != '[' && cc != '(' && cc != ']' && cc != ')' & cc != '}')) {
                tok += cc;
            } else if(cc == '=' || cc == '>') {
                tok += cc;
            } else {
                putBack(cc);
            }
            token.setToken(tok, TOKEN_OPERATOR, soffset, sline);
        }
    };
    
    Token_map LexInput::token_map;
    
    std::ostream &operator<<(std::ostream &out, const Token_type &t) {
        static const char *strz[] = {"Nothing","Name","Whitespace","String","Digit","Operator","Identifier", ""};
        signed int num = static_cast<signed int>(t);
        if(num >= 0 && num <= TOKEN_IDENTIFIER)
        std::cout << strz[num];
        return out;
    }
    
    std::ostream &operator<<(std::ostream &out, const Token &t) {
        out << "[" << t.getToken() << "] of type: [" << t.getType() << "] Line:" << t.line << ":" << t.offset;
        return out;
    }
            
    class Scanner {
        
    public:
        Scanner(std::istream *str) : input{str} { }
        Scanner(std::istream &str) : input(str) { }
        
        // will throw Scanner_EOF at end of file
        Scanner &operator>>(Token &token) {
            if(valid()) token = input.GetToken();
            else throw Scanner_EOF();
            return *this;
        }
        
        void collect() {
            Token t;
            while(input.valid()) {
                t = input.GetToken();
                std::cout << t << "\n";
            }
        }
        
        void err(std::string s) {
            std::cerr << s << "\n";
            throw Scanner_Error(s);
        }

    
        bool valid() {
            return input.valid();
        }
        
    protected:
        LexInput input;
        Token cur_token;
    };
      
    struct Func { //use default constuctor
        std::string name;
        double (*func)(double d);
    };
            
    class Parser : public Scanner {
    private:
        std::unordered_map<std::string, double> &vars;
        std::unordered_map<std::string, Func> &function;
    public:
        explicit Parser(std::istream *stream, std::unordered_map<std::string, double> &v, std::unordered_map<std::string, Func> &f) : Scanner{stream}, vars(v), function(f) {}
        explicit Parser(std::istream &stream, std::unordered_map<std::string, double> &v, std::unordered_map<std::string, Func> &f) : Scanner{stream}, vars{v}, function{f} {}
        bool eval() {
            try {
                while(1) {
                    Token t = input.GetToken();
                    if(t.getType() == TOKEN_EOF) {
                        return true;
                    }
            
                    std::cout << "Expression  Value: " << expr(false) << "\n";
            
                    if(input.GetCurrent().getToken() == ";")
                        continue;// eat token
                
                }
            }
            catch (Scanner_EOF) {
                std::cout << "end of evalulation.\n";
            }
            return false;
        }
        
        double prim(bool get) {
            
            if(get) input.GetToken();
            switch(input.GetCurrent().getType()) {
                case TOKEN_EOF:
                    throw lex::Scanner_EOF();
                    break;
                case TOKEN_DIGIT: {
                    double v = atof(input.GetCurrent().getToken().c_str());
                    input.GetToken();
                    return v;
                }
                    break;
                case TOKEN_CHAR: {
                    std::string var_name = input.GetCurrent().getToken();
                    input.GetToken();
                    if(input.GetCurrent().getToken() == "(") {
                        if (function.find(var_name) != function.end()) {
                            double d = expr(true);
                            if(input.GetCurrent().getToken() != ")") {
                                err("missing closing ).");
                                
                            }
                            
                            input.GetToken();
                            
                            if(function[var_name].func != 0)
                            return function[var_name].func(d);
                            
                            err("Error function not found.\n");
                        } else err("Unknown function");
                    }
                    
                    double &v = vars[var_name];
                    if(input.GetCurrent().getToken() == "=")  {
                        v = expr(true);
                    } else if(input.GetCurrent().getToken() == "+=") {
                        v += expr(true);
                        
                    } else if(input.GetCurrent().getToken() == "-=") {
                        v -= expr(true);
                    } else if(input.GetCurrent().getToken() == "*=") {
                        v *= expr(true);
                    } else if(input.GetCurrent().getToken() == "/=") {
                        double d = expr(true);
                        if(d == 0) err("Divide by zero");
                        v /= d;
                    }
                    return v;
                    
                }
                    break;
                case TOKEN_OPERATOR: {
                    if(input.GetCurrent().getToken() == "-") {
                        return -prim(true);
                        
                    } else if (input.GetCurrent().getToken() == "(") {
                        auto e = expr(true);
                        if(input.GetCurrent().getToken() != ")") err("Expected )");
                        input.GetToken();
                        return e;
                    }
                }
                    break;
                default:
                    return 0;
            }
            
          
            if(input.GetCurrent().getToken() == ")")
                err("No argument");
            return 0;
        }
        
        double term(bool get) {
            double left = prim(get);
            while(1) {
                std::string temp=input.GetCurrent().getToken();
                Token_type tok_type = input.GetCurrent().getType();
                if(tok_type == TOKEN_CHAR || tok_type == TOKEN_DIGIT) {
                    err("Invalid type expected operator");
                }
                switch(tok_type) {
                     case TOKEN_OPERATOR: {
                        switch(temp[0]) {
                            case '*':
                                left *= prim(true);
                                break;
                            case '/':
                                if(auto d = prim(true)) {
                                    left /= d;
                                    break;
                                }
                                 err("Divide by Zero");
                                break;
                            default:
                                return left;
                        }
                        break;
                    default:
                        break;

                     }
                }
            }
            return 0;
        }
        
        double expr(bool get) {
            double left = term(get);
            while(1) {
                 switch(input.GetCurrent().getType()) {
                     case TOKEN_EOF:
                         throw lex::Scanner_EOF();
                         break;
                    case TOKEN_OPERATOR:
                    {
                        std::string temp=input.GetCurrent().getToken();
                        
                        if(temp == "++") err("No ++ right now\n");
                        if(temp == "--") err("No -- right now\n");
                        
                        switch(temp[0]) {
                            case '+':
                                left += term(true);
                                break;
                            case '-':
                                left -= term(true);
                                break;
                            default:
                                return left;
                        }
                        
                    }
                        break;
                    default:
                        return 0;
                }
            }
        }
    };
}


#endif