//
// Program:  temperature_records.
//
// Purpose:  Compare yesterday's high and low temperatures with
//   record highs and lows for that date; update records if necessary.
//
// Input:  
//   From standard input, yesterday's date, high and low temperatures.
//   In text file temps_in.txt, record highs and lows for all dates.
//      (Each line contains month, day, record high, year of record
//      high, record low, year of record low.)
// Output:
//   To standard output, record high/low for yesterday's high/low.
//   Updated master file in temps_out.txt.
//

#include <iostream.h>
#include <fstream.h>		// has ifstream, ofstream.
#include <stdlib.h>		// has exit(), EXIT_SUCCESS, EXIT_FAILURE

// Function prototypes (see comments below).
void openFiles(ifstream & in, ofstream & out);
void closeFiles(ifstream & in, ofstream & out);
void getUserInput(int & month, int & day, int & year,
		  int & high, int & low);
bool validateDate(int month, int day, int year);
bool readMaster(ifstream & masterIn,
		int & month, int & day, int & high, int & highYear,
		int & low, int & lowYear);
void writeMaster(ofstream & masterOut,
		 int month, int day, int high, int highYear, 
		 int low, int lowYear);
void doLow(int yesterdayLow, int yesterdayYear, int & low, int & lowYear);
void doHigh(int yesterdayHigh, int yesterdayYear, int & high, int & highYear);


// Main program.
int main(void)
{
  int yesterdayMonth, yesterdayDay, yesterdayYear;
  int yesterdayHigh, yesterdayLow;
  ifstream masterIn;
  ofstream masterOut;
  int month, day, high, highYear, low, lowYear;

  getUserInput(yesterdayMonth, yesterdayDay, yesterdayYear,
		yesterdayHigh, yesterdayLow);

  openFiles(masterIn, masterOut);

  // Copy records from input master to output master until we reach
  //  yesterday's date.
  while (readMaster(masterIn, month, day, high, highYear, low,
		    lowYear)
	 && (month != yesterdayMonth || day != yesterdayDay))
      writeMaster(masterOut, month, day, high, highYear, low,
		  lowYear);

  // If we didn't find anything in master, bail.
  if (masterIn.eof())
    {
      cout << "Error:  No record found in master file.\n";
      closeFiles(masterIn, masterOut);
      exit(EXIT_FAILURE);
    }

  // Compare yesterday's temps to records; update records if 
  //   necessary.
  doLow(yesterdayLow, yesterdayYear, low, lowYear);
  doHigh(yesterdayHigh, yesterdayYear, high, highYear);

  // Write out updated master record.
  writeMaster(masterOut, month, day, high, highYear, low, lowYear);

  // Copy remainder of master file.
  while (readMaster(masterIn, month, day, high, highYear, low,
		    lowYear))
      writeMaster(masterOut, month, day, high, highYear, low,
		  lowYear);

  closeFiles(masterIn, masterOut);
  return EXIT_SUCCESS;
}

// Post:  input, output files opened successfully opened; or if
//          not possible, program exited.
void openFiles(ifstream & in, ofstream & out)
{
  in.open("temps_in.txt");
  if (in.fail())
    {
      cout << "Unable to open input file temps_in.txt.\n";
      exit(EXIT_FAILURE);
    }
  out.open("temps_out.txt");
  if (out.fail())
    {
      cout << "Unable to open output file temps_out.txt.\n";
      exit(EXIT_FAILURE);
    }
  return;
}

// Post:  input, output files closed.
void closeFiles(ifstream & in, ofstream & out)
{
  in.close();
  out.close();
  return;
}

// Post:  user prompted to enter desired info (yesterday's date
//          and temps); responses returned in parameters;
//          program exited if date not valid.
void getUserInput(int & month, int & day, int & year,
		  int & high, int & low)
{
  cout << "Enter yesterday's month, day, and year "
    " (e.g., 3 1 2000 for March 1 2000):\n";
  cin >> month >> day >> year;
  if (!validateDate(month, day, year))
    {
      cout << "Not a valid date!\n";
      exit(EXIT_FAILURE);
    }
  cout << "Enter high, low temperatures (integer values):\n";
  cin >> high >> low;
  return;
}

// Pre:  month, day, year supposedly represent a date.
// Post:  returns true if they do, false if not.
bool validateDate(int month, int day, int year)
{
  if (year < 0)
    return false;
  if (month < 1 || month > 12)
    return false;
  int daysInMonth;
  if (month == 2)
    {
      if ((year%400 == 0) || ( year%4 == 0 && year%100 != 0))
	daysInMonth = 29;
      else
	daysInMonth = 28;
    }
  else if (month == 9 || month == 4 || month == 6 || month == 11)
    daysInMonth = 30;
  else
    daysInMonth = 31;
  if (day < 1 || day > daysInMonth)
    return false;
  return true;
}

// Pre:  masterIn successfully opened; file is in format described 
//         in header comments.
// Post:  if masterIn is not at EOF, remaining variables contain 
//          information from one line of file and return value is
//          true; else return value is false.
bool readMaster(ifstream & masterIn,
		int & month, int & day, int & high, int & highYear,
		int & low, int & lowYear)
{
  return (masterIn >> month >> day >> high >> highYear 
	  >> low >> lowYear);
}

// Pre:  masterOut successfully opened.
// Post:  information from parameters has been written to masterOut,
//          in format described in header comments.
void writeMaster(ofstream & masterOut,
		 int month, int day, int high, int highYear, 
		 int low, int lowYear)
{
  masterOut << month << " " << day << " " 
	    << high << " " << highYear << " "
	    << low << " " << lowYear << endl;
  return;
}

// Pre:  yesterdayLow, yesterdayYear represent yesterday's low temperature,
//         year; low, lowYear represent record low not including yesterday's
//         year.
// Post:  low, lowYear represent record low including yesterday's
//          year.
//        record low and year written to standard output.
void doLow(int yesterdayLow, int yesterdayYear, 
	   int & low, int & lowYear)
{
  if (yesterdayLow > low)
    {
      cout << "Record low for that date:  " << low
	   << ", set in " << lowYear << endl;
    }
  else
    {
      cout << "Yesterday's low is a new record!\n";
      cout << "Previous record low for that date:  " << low
	   << ", set in " << lowYear << endl;
      low = yesterdayLow;
      lowYear = yesterdayYear;
    }
  return;
}

// Pre:  yesterdayHigh, yesterdayYear represent yesterday's high temperature,
//         year; high, highYear represent record high not including yesterday's
//         year.
// Post:  high, highYear represent record high including yesterday's
//          year.
//        record high and year written to standard output.
void doHigh(int yesterdayHigh, int yesterdayYear, 
	   int & high, int & highYear)
{
  if (yesterdayHigh < high)
    {
      cout << "Record high for that date:  " << high
	   << ", set in " << highYear << endl;
    }
  else
    {
      cout << "Yesterday's high is a new record!\n";
      cout << "Previous record high for that date:  " << high
	   << ", set in " << highYear << endl;
      high = yesterdayHigh;
      highYear = yesterdayYear;
    }
  return;
}