//******************************************************************
// ConvertDates program
// This program reads dates in American form from an input file and
// writes them to an output file in American, British, and ISO form.
// No data validation is done on the input file
//******************************************************************
#include <iostream>
#include <iomanip>    // For setw()
#include <fstream>    // For file I/O
#include <string>     // For string type

using namespace std;

void Get2Digits( ifstream&, string& );
void GetYear( ifstream&, string& );
void OpenForInput( ifstream& );
void OpenForOutput( ofstream& );
void Write( ofstream&, string, string, string );

int main()
{
    string   month;         // Both digits of month
    string   day;           // Both digits of day
    string   year;          // Four digits of year
    ifstream dataIn;        // Input file of dates
    ofstream dataOut;       // Output file of dates

    OpenForInput(dataIn);
    OpenForOutput(dataOut);
    if ( !dataIn || !dataOut )                   // Make sure files
        return 1;                                //   were opened

    dataOut << setw(20) << "American Format"     // Write headings
            << setw(20) << "British Format"
            << setw(20) << "ISO Format" << endl << endl;

    Get2Digits(dataIn, month);                   // Priming read
    while (dataIn)                               // While not EOF...
    {
        Get2Digits(dataIn, day);
        GetYear(dataIn, year);
        Write(dataOut, month, day, year);
        Get2Digits(dataIn, month);
    }
    return 0;
}

//******************************************************************

void OpenForInput( /* inout */ ifstream& someFile )    // File to be
                                                       // opened
// Prompts the user for the name of an input file
// and attempts to open the file

// Postcondition: Exercise
//
// Note:
//     Upon return from this function, the caller must test
//     the stream state to see if the file was successfully opened

{
    string fileName;    // User-specified file name

    cout << "Input file name: ";
    cin >> fileName;

    someFile.open(fileName.c_str());
    if ( !someFile )
        cout << "** Can't open " << fileName << " **" << endl;
}

//******************************************************************

void OpenForOutput( /* inout */ ofstream& someFile )   // File to be
                                                       // opened
// Prompts the user for the name of an output file
// and attempts to open the file

// Postcondition: Exercise
//
// Note:
//     Upon return from this function, the caller must test
//     the stream state to see if the file was successfully opened

{
    string fileName;    // User-specified file name

    cout << "Output file name: ";
    cin >> fileName;

    someFile.open(fileName.c_str());
    if ( !someFile )
        cout << "** Can't open " << fileName << " **" << endl;
}

//******************************************************************

void Get2Digits( /* inout */ ifstream& dataIn,      // Input file
                 /* out */   string&   twoChars )   // Two digits

// Reads characters up to a slash from dataIn and returns two
// digit characters in the string twoChars.  If only one digit
// is found before the slash, a leading '0' is inserted.
// (If input fails due to end-of-file, twoChars is undefined.)

// Precondition:  Exercise
// Postcondition: Exercise

{
    char firstChar;    // First character of a two-digit value
    char secondChar;   // Second character of value
    char dummy;        // To consume the slash, if necessary

    dataIn >> firstChar;
    if ( !dataIn )               // Check for EOF
        return;                  // If so, exit the function

    dataIn >> secondChar;
    if (secondChar == '/')
    {
        secondChar = firstChar;
        firstChar = '0';
    }
    else
        dataIn >> dummy;         // Consume the slash

    twoChars = firstChar;
    twoChars = twoChars + secondChar;
}

//******************************************************************

void GetYear( /* inout */ ifstream& dataIn,      // Input file
              /* out */   string&   year   )     // Four digits
                                                 //   of year

// Reads characters from dataIn and returns four digit characters
// in the year string

// Precondition:  Exercise
// Postcondition: Exercise

{
    char digitChar;    // One digit of the year
    int  loopCount;    // Loop control variable

    year = "";
    loopCount = 1;
    while (loopCount <= 4)
    {
        dataIn >> digitChar;
        year = year + digitChar;
        loopCount++;
    }
}

//******************************************************************

void Write( /* inout */ ofstream& dataOut,    // Output file
            /* in */    string    month,      // Month string
            /* in */    string    day,        // Day string
            /* in */    string    year    )   // Year string

// Writes the date represented by month, day, and year to file
// dataOut in American, British, and ISO form

// Precondition:  Exercise
// Postcondition: Exercise

{
    dataOut << setw(9) << month << '/' << day << '/' << year;
    dataOut << setw(13) << day << '/' << month << '/' << year;
    dataOut << setw(16) << year << '-' << month
            << '-' << day << endl;
}