// in_driver.cpp : a infix evaluator driver
#include <iostream>
#include <map>
#include <cstdlib>

#include "Lexer.h"
#include "Infix_Evaluator.h"
#include "term_control.h"
#include "error_handling.h"
using namespace std;

// ----------------------------------------------------------------------------------
// prototypes and typedefs
// ----------------------------------------------------------------------------------
typedef void (*cmd_t)(Lexer);
void print_exp(Lexer); // print the value of an expression
void assign(Lexer);    // assign a variable to be an exp
void bye(Lexer);       // simply quit
void prompt();

static map<string,double> sym_table;

/**
 * ----------------------------------------------------------------------------------
 * the body
 * ----------------------------------------------------------------------------------
 */
int main() {
    Lexer lexer; string line; Token tok;
    map<string,cmd_t> cmd_map;
    cmd_map["exit"]   = &bye;
    cmd_map["bye"]    = &bye;
    cmd_map["print"]  = &print_exp;
    cmd_map["assign"] = &assign;

    cout << term_cc(YELLOW) << "UB Calculator Program. Version 0.9" << endl 
        << " Author: Hung Q. Ngo" << endl
        << " Report bugs to hungngo@buffalo.edu\n";

    while (cin) {
        prompt(); getline(cin, line); lexer.set_input(line);
        if (!lexer.has_more_token()) continue;
        tok = lexer.next_token();
        if (tok.type != IDENT) { error_return("Syntax error\n"); continue; }   

        if (cmd_map.find(tok.value) != cmd_map.end())
            cmd_map[tok.value](lexer);
        else
            error_return("Unknown command");
    }
    return 0;
}

/**
 * -----------------------------------------------------------------------------
 * print the expression if there's no error
 * -----------------------------------------------------------------------------
 */
void print_exp(Lexer lexer) {
    Infix_Evaluator ie; double result;
    try {
        ie.set_expression(lexer);
        result = ie.eval(sym_table);
        cout << term_cc(CYAN) << "= " << result << term_cc() << endl;
    } 
    catch (runtime_error &dbz) {
        error_return(dbz.what());
    }
}

/**
 * -----------------------------------------------------------------------------
 * assign a variable.
 * -----------------------------------------------------------------------------
 */
void assign(Lexer lexer) {
    Infix_Evaluator ie; double result;
    Token var_tok, assign_tok;

    // short circuit evaluation
    if (!lexer.has_more_token() || 
        (var_tok = lexer.next_token()).type != IDENT) {
        error_return("Syntax error: assign var = expression");
        return;
    }

    // short circuit evaluation
    if (!lexer.has_more_token() || 
        (assign_tok = lexer.next_token()).type != OPERATOR || 
        assign_tok.value[0] != '=') {
        error_return("Syntax error: assign var = expression");
        return;
    }

    try {
        ie.set_expression(lexer);
        result = ie.eval(sym_table);
        sym_table[var_tok.value] = result;
        cout << term_cc(CYAN) << var_tok.value << " = " 
             << result << term_cc() << endl;
    } 
    catch (runtime_error &dbz) {
        error_return(dbz.what());
    }
}

/**
 * -----------------------------------------------------------------------------
 * terminates the program, ignores all parameters
 * -----------------------------------------------------------------------------
 */
void bye(Lexer lexer) {
    if (lexer.has_more_token()) {
        error_return("Syntax error: use bye/exit/quit\n");
    } else {
        exit(0);
    }   
}

/**
 * ----------------------------------------------------------------------------------
 * just print a prompt.
 * ----------------------------------------------------------------------------------
 */
void prompt() {
    cout << term_cc(BLUE) << "> " << term_cc() << flush;
}