/*
 *  Implementation file for cgi.h.
 *  
 *  Note that C-style strings (o type  char* ) are used internally.
 */

#include <iostream>
#include <string>
#include <sstream>
#include <cstdlib>
#include "cgi.h"

struct fieldData {  
     // Represents one name/value pair from query data sent to CGI program.
     // Generally, that means the name and value of an item in a HTML form.
   char *name;   
   char *value;
};

static char* cgiData[REMOTE_IDENT]; 
     // Contains the valuse of CGI variables REQUEST_METHOD, REMOTE_ADDR,
     // HTTP_REFERER, etc.  (NOTE:  A "static" global variable or
     // function in C++ is one that can only be used in the file in
     // which it is defined -- this is not related to other meanings
     // of the overused word "static.")

static fieldData *fields = NULL;
     // An array, to be created by the getFields() function,
     // containing all name/value pairs in the CGI data.
     // If there is no data, the value will be NULL after
     // calling getFields().

static int fieldCt = 0;  
     // The number of name/value pairs stored in the array, fields.
     // The value is set by a call to the getFields() funtion.

static bool dataReady = false;


/**********************************************************************************
 *   Function getFields() reads CGI data and decodes it into a set of name/value  *
 *   pairs.  The number of pairs is stored in the global variable, fieldCt.       *
 *   The pairs themselves are stored in a global array, fields.                   *
 *   (The function can read data submitted using either the GET or POST method.   *
 *   Data submitted through GET is retrieved from the environment variable        *
 *   QUERY_STRING.  Data submitted with POST is read from standard input.)       *
 **********************************************************************************/

static void getFields() {
   char* cgiVarName[] = {
        "REQUEST_METHOD",
        "REMOTE_ADDR",
        "HTTP_REFERER",
        "HTTP_USER_AGENT",
        "QUERY_STRING", 
        "CONTENT_LENGTH",
        "CONTENT_TYPE",
        "HTTP_ACCEPT",
        "HTTP_HOST", 
        "REMOTE_PORT",
        "SCRIPT_FILENAME",
        "GATEWAY_INTERFACE",
        "SERVER_PROTOCOL",
        "HTTP_ACCEPT_LANGUAGE",
        "REQUEST_URI", 
        "SCRIPT_NAME",
        "SERVER_SOFTWARE",
        "SERVER_PORT",
        "PATH_INFO",
        "REMOTE_USER",
        "DOCUMENT_ROOT",
        "AUTH_TYPE",
        "REMOTE_IDENT"
   };
   dataReady = true;
   for (int i = REQUEST_METHOD; i <= REMOTE_IDENT; i++)
      cgiData[i] = getenv(cgiVarName[i]);
   char *data = NULL;
   char *method = cgiData[REQUEST_METHOD];
   if (method && strcmp(method, "GET") == 0) {
      char *query = cgiData[QUERY_STRING];
      if (query == NULL || query[0] == 0)
         return;
      data = new char[strlen(query)+1];
      if (data == NULL)
         return;
      strcpy(data,query);
   }
   else if (method && strcmp(method, "POST") == 0) {
      char *len = cgiData[CONTENT_LENGTH];
      if (len == NULL || len[0] == 0)
         return;      
      int datalength = atoi(len);
      if (datalength <= 0)
         return;
      data = new char[datalength+1];
      if (data == NULL)
         return;
      cin.get(data,datalength+1,'\0');
      if (!cin) {
         delete[] data;
         data = NULL;
         return;
      }
   }
   if (data == NULL)
      return;
   fieldCt = 1;
   for (int i = 0; data[i]; i++)
      if (data[i] == '&')
         fieldCt++;
   fields = new fieldData[fieldCt];
   if (fields == NULL) {
      delete[] data;
      data = NULL;
      fieldCt = 0;
      return;
   }
   int inChar = 0;
   int outChar = 0;
   int ct = 0;
   int readingName = 1;
   fields[0].name = &data[0]; 
   while (1) {
      if (data[inChar] == '+')
         data[outChar] = ' ';
      else if (data[inChar] == '%') {
         inChar++;
         if (data[inChar] == 0 || data[inChar+1] == 0) // shouldn't happen
            continue;
         int ch;
         if (data[inChar] >= '0' && data[inChar] <= '9')
            ch = data[inChar] - '0';
         else if (data[inChar] >= 'a' && data[inChar] <= 'z')
            ch = data[inChar] - 'a' + 10;
         else
            ch = data[inChar] - 'A' + 10;
         inChar++;
         if (data[inChar] >= '0' && data[inChar] <= '9')
            ch = 16*ch + (data[inChar] - '0');
         else if (data[inChar] >= 'a' && data[inChar] <= 'z')
            ch = 16*ch + (data[inChar] - 'a' + 10);
         else
            ch = 16*ch + (data[inChar] - 'A' + 10);
         data[outChar] = ch;         
      }
      else if (data[inChar] == '=') {
         data[outChar] = 0;
         readingName = 0;
         fields[ct].value = &data[outChar+1];
      }
      else if (data[inChar] == '&' || data[inChar] == 0) {
         int done = (data[inChar] == 0);
         data[outChar] = 0;
         if (readingName)  // shouldn't be true
            fields[ct].value = fields[ct].name;
         if (done) {
            break;
         }
         ct++;
         readingName = 1;
         fields[ct].name = &data[outChar+1];
      }
      else
         data[outChar] = data[inChar];
      outChar++;
      inChar++;
   }
   if (readingName) // shouldn't be true
      fields[ct].value = fields[ct].name;
   fieldCt = ct+1;  // have to already be equal, but let's be sure.
}  // end getFields();



/******************************************************
 *  Definitions of fucntions defined in cgi.h         *
 ******************************************************/


string getCGIVariable(CGIVariable varName) {
   if (!dataReady)
      getFields();
   if (cgiData[varName])
      return cgiData[varName];
   else
      return "";
}


int formItemCount() {
   if (!dataReady)
      getFields();
   return fieldCt;
}


string getFormItemValue(string itemName) {
   if (!dataReady)
      getFields();
   for (int i = 0; i < fieldCt; i++) {
      if (itemName == fields[i].name)
         return fields[i].value;
   }
   return "";
}


string getFormItemName(int itemNum) {
   if (!dataReady)
      getFields();
   if (itemNum >= 0 && itemNum < fieldCt)
      return fields[itemNum].name;
   else
      return "";
}


string getFormItemValue(int itemNum) {
   if (!dataReady)
      getFields();
   if (itemNum >= 0 && itemNum < fieldCt)
      return fields[itemNum].value;
   else
      return "";
}


bool string2int(string numString, int &num) {
   istringstream s(numString);
   num = 0;  // value if an error occurs
   s >> num;
   if (!s)  // Couldn't read a number.
      return false;
   int junk;  // Shouldn't be anything else in the string --
              // to make sure, try to read something.
   s >> junk;
   if (!s.eof())
      return false;
   return true;
}


bool string2double(string numString, double &num) {
   istringstream s(numString);
   num = 0;  // value if an error occurs
   s >> num;
   if (!s)  // Couldn't read a number.
      return false;
   int junk;  // Shouldn't be anything else in the string --
              // to make sure, try to read something.
   s >> junk;
   if (!s.eof())
      return false;
   return true;
}


string htmlEscape(string str) {
   int change = false;
   int len = str.length();
   for (int i = 0; i < len; i++) {
      if (str[i] == '&' || str[i] == '<' || str[i] == '>' || str[i] == '"') {
         change = true;
         break;
      }
   }
   if (change) {
      string s;
      for (int i = 0; i < len; i++) {
         switch (str[i]) {
            case '&':
               s += "&amp;";
               break;
            case '"':
               s += "&quot;";
               break;
            case '<':
               s += "&lt;";
               break;
            case '>':
               s += "&gt;";
               break;
            default:
               s += str[i];
         }
      }
      return s;
   }
   else {
      return str;
   }
}