// bbldc_calendarbus252.h                                             -*-C++-*-
#ifndef INCLUDED_BBLDC_CALENDARBUS252
#define INCLUDED_BBLDC_CALENDARBUS252

#include <bsls_ident.h>
BSLS_IDENT("$Id: $")

//@PURPOSE: Provide stateless functions for calendar-based BUS-252.
//
//@CLASSES:
//  bbldc::CalendarBus252: BUS-252 convention stateless functions
//
//@DESCRIPTION: This component provides a `struct`, `bbldc::CalendarBus252`,
// that serves as a namespace for defining a suite of date-related functions
// used to compute the day count and the year fraction between two dates as per
// the BUS-252 day-count convention.  In this day-count convention, the day
// count between two ordered dates, `beginDate` and `endDate` where
// `beginDate < endDate`, is exactly the number of *business* days occurring in
// the time period `[beginDate .. endDate)`.  Reversing the order of the dates
// negates the result.  When the two dates have the same value, the day count
// is 0.  The year fraction is the day count divided by 252.
//
///Usage
///-----
// This section illustrates intended use of this component.
//
///Example 1: Computing Day Count and Year Fraction
/// - - - - - - - - - - - - - - - - - - - - - - - -
// The following snippets of code illustrate how to use `bbldc::CalendarBus252`
// methods.  First, create two `bdlt::Date` variables, `d1` and `d2`:
// ```
// const bdlt::Date d1(2003, 10, 19);
// const bdlt::Date d2(2003, 12, 31);
// ```
// Then, create a `calendar` with a valid range spanning 2003 and typical
// weekend days:
// ```
// bdlt::Calendar calendar;
// calendar.setValidRange(bdlt::Date(2003, 1, 1), bdlt::Date(2003, 12, 31));
// calendar.addWeekendDay(bdlt::DayOfWeek::e_SUN);
// calendar.addWeekendDay(bdlt::DayOfWeek::e_SAT);
// ```
// Next, compute the day count between `d1` and `d2`:
// ```
// const int daysDiff = bbldc::CalendarBus252::daysDiff(d1, d2, calendar);
// assert(52 == daysDiff);
// ```
// Finally, compute the year fraction between the two dates:
// ```
// const double yearsDiff = bbldc::CalendarBus252::yearsDiff(d1,
//                                                           d2,
//                                                           calendar);
// // Need fuzzy comparison since 'yearsDiff' is a 'double'.
// assert(yearsDiff > 0.2063 && yearsDiff < 0.2064);
// ```

#include <bblscm_version.h>

#include <bdlt_calendar.h>
#include <bdlt_date.h>

#include <bsls_assert.h>
#include <bsls_platform.h>

namespace BloombergLP {
namespace bbldc {

                          // =====================
                          // struct CalendarBus252
                          // =====================

/// This `struct` provides a namespace for a suite of pure functions that
/// compute values based on dates according to the BUS-252 day-count
/// convention.
struct CalendarBus252 {

    // CLASS METHODS

    /// Return the (signed) number of days between the specified `beginDate`
    /// and `endDate` according to the BUS-252 day-count convention with the
    /// specified `calendar` providing the definition of business days.  If
    /// `beginDate <= endDate`, then the result is non-negative.  The
    /// behavior is undefined unless `calendar.isInRange(beginDate)` and
    /// `calendar.isInRange(endDate)`.  Note that reversing the order of
    /// `beginDate` and `endDate` negates the result and that the result is
    /// 0 when `beginDate == endDate`.
    static int daysDiff(const bdlt::Date&     beginDate,
                        const bdlt::Date&     endDate,
                        const bdlt::Calendar& calendar);

    /// Return the (signed fractional) number of years between the specified
    /// `beginDate` and `endDate` according to the BUS-252 day-count
    /// convention with the specified `calendar` providing the definition of
    /// business days.  If `beginDate <= endDate`, then the result is
    /// non-negative.  The behavior is undefined unless
    /// `calendar.isInRange(beginDate)` and `calendar.isInRange(endDate)`.
    /// Note that reversing the order of `beginDate` and `endDate` negates
    /// the result; specifically,
    /// `|yearsDiff(b, e, c) + yearsDiff(e, b, c)| <= 1.0e-15` for all
    /// calendars `c` and valid dates `b` and `e`.
    static double yearsDiff(const bdlt::Date&     beginDate,
                            const bdlt::Date&     endDate,
                            const bdlt::Calendar& calendar);
};

// ============================================================================
//                             INLINE DEFINITIONS
// ============================================================================

                          // ---------------------
                          // struct CalendarBus252
                          // ---------------------

// CLASS METHODS
inline
int CalendarBus252::daysDiff(const bdlt::Date&     beginDate,
                             const bdlt::Date&     endDate,
                             const bdlt::Calendar& calendar)
{
    BSLS_ASSERT_SAFE(calendar.isInRange(beginDate));
    BSLS_ASSERT_SAFE(calendar.isInRange(endDate));

    if (beginDate < endDate) {
        return calendar.numBusinessDays(beginDate, endDate - 1);      // RETURN
    }
    else if (beginDate > endDate) {
        return -calendar.numBusinessDays(endDate, beginDate - 1);     // RETURN
    }
    return 0;
}

inline
double CalendarBus252::yearsDiff(const bdlt::Date&     beginDate,
                                 const bdlt::Date&     endDate,
                                 const bdlt::Calendar& calendar)
{
#if defined(BSLS_PLATFORM_CMP_GNU) && (BSLS_PLATFORM_CMP_VERSION >= 50301)
    // Storing the result value in a 'volatile double' removes extra-precision
    // available in floating-point registers.

    const volatile double rv =
#else
    const double rv =
#endif
           static_cast<double>(daysDiff(beginDate, endDate, calendar)) / 252.0;

    return rv;
}

}  // close package namespace
}  // close enterprise namespace

#endif

// ----------------------------------------------------------------------------
// Copyright 2017 Bloomberg Finance L.P.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ----------------------------- END-OF-FILE ----------------------------------
