#include "exprparser.h"
#include "arithexpr.h"
#include "relexpr.h"
#include "logexpr.h"
#include <string.h>
#include <stdlib.h>

void check_token(const char* token, const char* should_be, int l) {
   if (token == (char*)0) {
      throw expression_error(l,"unexpected end of file");
   }
   if (strcmp(token,should_be) != 0) {
      throw expression_error(l,"syntax error");
   }
}

expression_error::expression_error(int l, char* s):line_number(l) {
   strcpy(error,s);
}

expression_parser::expression_parser(lexer* lex):L(lex) {
}

expression* expression_parser::read_one(istream& is,list<char*>& B) {
   const char* token = L->get_token(is);

   expression *ex = (expression*)0;

   if (strcmp(token,"(")==0) { // sub expression
      expression *e = read(is,B); // call resursivelly
      check_token(L->next_token(is),")",L->get_line_number());
      ex = new sub_expression(e);
   } else if (strcmp(token,"-")==0) { // - expression; unary -
      expression *e = read_one(is,B);
      ex = new unary_minus(e);
   } else if (strcmp(token,"+")==0) { // + expression; unary +
      expression *e = read_one(is,B);
      ex = new unary_plus(e);
   } else if (strcmp(token,"!")==0) { // ! expression; unary !
      expression *e = read_one(is,B);
      ex = new negation(e);
   } else if (strcmp(token,"sin")==0) { // sin(x) 
      check_token(L->next_token(is),"(",L->get_line_number());
      expression *arg = read(is,B);
      check_token(L->next_token(is),")",L->get_line_number());
      ex = new sin_function(arg);
   } else if (strcmp(token,"cos")==0) { // cos(x)
      check_token(L->next_token(is),"(",L->get_line_number());
      expression *arg = read(is,B);
      check_token(L->next_token(is),")",L->get_line_number());
      ex = new cos_function(arg);
   } else if (strcmp(token,"tan")==0) { // tan(x)
      check_token(L->next_token(is),"(",L->get_line_number());
      expression *arg = read(is,B);
      check_token(L->next_token(is),")",L->get_line_number());
      ex = new tan_function(arg);
   } else if (token[0] >= '0' && token[0] <= '9') { // constant
      ex = new constant(atof(token)); 
   } else {
      // SEE IF IT IS ANY OF THE VARIABLES
      list_iterator<char*> I = B.first();
      int i=0;
      bool found = false;
      while(I.has_more_elements() && !found) {
         if (strcmp(*I,token) == 0) {
            ex = new variable(i);
            found = true;
            break;
         }
         I++;
         i++;
      }
      if (!found) {
         throw expression_error(L->get_line_number(),"unknown identifier");
      }
   }

   return ex;
}

expression* expression_parser::read(istream& is, list<char*>& B) {

   expression * ex = read_one(is,B); // up to potential binary symbol
   const char* token;

   if ((token = L->next_token(is)) == (char*)0) return ex; // end of file

   // check for binary operators
   // the trick is to allocate them with the wrapper
   // "binary_operator_adaptor"
   if (strcmp(token,"+")==0) { // binary +
      return new binary_operator_adaptor(new binary_plus(ex,read(is,B)));
   } else if (strcmp(token,"-")==0) { // binary -
      return new binary_operator_adaptor(new binary_minus(ex,read(is,B)));
   } else if (strcmp(token,"/")==0) { // /
      return new binary_operator_adaptor(new division(ex,read(is,B)));
   } else if (strcmp(token,"*")==0) { // *
      return new binary_operator_adaptor(new multiplication(ex,read(is,B)));
   } else if (strcmp(token,"==")==0) { // ==
      return new binary_operator_adaptor(new equal_expression(ex,read(is,B)));
   } else if (strcmp(token,"!=")==0) { // !=
      return new binary_operator_adaptor(
      new not_equal_expression(ex,read(is,B)));
   } else if (strcmp(token,"<")==0) { // <
      return new binary_operator_adaptor(new less_expression(ex,read(is,B)));
   } else if (strcmp(token,"<=")==0) { // <=
      return new binary_operator_adaptor(
         new less_or_equal_expression(ex,read(is,B)));
   } else if (strcmp(token,">")==0) { // >
      return new binary_operator_adaptor(
        new greater_expression(ex,read(is,B)));
   } else if (strcmp(token,">=")==0) { // >=
      return new binary_operator_adaptor(
         new greater_or_equal_expression(ex,read(is,B)));
   } else if (strcmp(token,"&&")==0) { // && 
      return new binary_operator_adaptor(new and_expression(ex,read(is,B)));
   } else if (strcmp(token,"||")==0) { // ||
      return new binary_operator_adaptor(new or_expression(ex,read(is,B)));
   } else {
      L->putback(); // OTHERWISE IT IS NOT A BINARY EXPRESSION!
   }

   return ex;
}