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DateParse.hpp

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/*==========================================================================
 * Copyright (c) 2004 University of Massachusetts.  All Rights Reserved.
 *
 * Use of the Lemur Toolkit for Language Modeling and Information Retrieval
 * is subject to the terms of the software license set forth in the LICENSE
 * file included with this software, and also available at
 * http://www.lemurproject.org/license.html
 *
 *==========================================================================
*/


//
// DateParse
//
// 13 April 2004 -- tds
//

#ifndef INDRI_DATEPARSE_HPP
#define INDRI_DATEPARSE_HPP

class DateParse {
private:
  static int _parseYear( const std::string& year ) {
    return atoi( year.c_str() );
  }

  static int _parseDay( const std::string& day ) {
    return atoi( day.c_str() );
  }

  static int _parseMonth( const std::string& month ) {
    if( month[0] >= '0' && month[0] <= '9' )
      return atoi( month.c_str() );

    char prefix[4];
    memset( prefix, 0, 4 );

    for( unsigned int i=0; i<4 && i<month.size(); i++ ) {
      prefix[i] = tolower( month[i] );
    }
    
    // j f m a m j j a s o n d
    if( prefix[0] == 'j' ) {
      if( prefix[1] == 'a' ) return 1; // january
      if( prefix[2] == 'n' ) return 6; // june
      if( prefix[2] == 'l' ) return 7; // july
      return 0;
    } else if( prefix[0] == 'f' ) {
      return 2; // february
    } else if( prefix[0] == 'a' ) {
      if( prefix[1] == 'p' ) return 4; // april
      if( prefix[1] == 'u' ) return 8; // august
      return 0;
    } else if( prefix[0] == 'm' ) {
      if( prefix[2] == 'r' ) return 3; // march
      if( prefix[2] == 'y' ) return 5; // may
      return 0;
    } else if( prefix[0] == 's' ) {
      return 9; // september
    } else if( prefix[0] == 'o' ) {
      return 10; // october
    } else if( prefix[0] == 'n' ) {
      return 11; // november
    } else if( prefix[0] == 'd' ) {
      return 12;
    }

    return 0;
  }

public:
  // converts year, month, and day from parser to the number of days since 1600
  static UINT64 convertDate( const std::string& year, const std::string& month, const std::string& day ) {
    int numYear = _parseYear( year );
    int numMonth = _parseMonth( month );
    int numDay = _parseDay( day );

    int monthCumulativeDays[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
    if( numMonth == 0 || numYear < 1601 || numDay == 0 )
      return 0;

    // let's do days since 1600 here
    UINT64 totalDays = 0;
    UINT64 yearsSince = numYear - 1600;
    
    // every 4 years is a leap year, except every 100 years is not, except every 400 years actually is...
    UINT64 leapDays = yearsSince / 4 -
                      yearsSince / 100 +
                      yearsSince / 400 + 
                      1; // 1 leap day in 1600

    // if this year is a leap year and it's past febuary, add an extra year on
    if( numMonth > 2 && (numYear % 4) == 0 && ( ((numYear % 100) != 0) || (numYear % 400) == 0) )
      leapDays++;

    return (numDay-1) + monthCumulativeDays[numMonth-1] + yearsSince*365 + leapDays;
  }
};

#endif // INDRI_DATEPARSE_HPP

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