// bdlt_dayofweekutil.h                                               -*-C++-*-
#ifndef INCLUDED_BDLT_DAYOFWEEKUTIL
#define INCLUDED_BDLT_DAYOFWEEKUTIL

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

//@PURPOSE: Provide common non-primitive operations on `bdlt::DayOfWeek::Enum`.
//
//@CLASSES:
//  bdlt::DayOfWeekUtil: functions operating on the day-of-week enumeration
//
//@SEE_ALSO: bdlt_dayofweek
//
//@DESCRIPTION: This utility component provides a `struct`,
// `bdlt::DayOfWeekUtil`, that serves as a namespace for functions operating on
// the day-of-week enumeration.
//
// This component provides the following (static) methods:
// ```
// 'add'                      Determine the day of the week that results from
//                            shifting a given 'bdlt::DayOfWeek::Enum' value
//                            by a given (signed) number of days.
// ```
//
///Usage
///------
// This section illustrates intended use of this component.
//
///Example 1: Basic Usage
/// - - - - - - - - - - -
// Suppose we have some event occurring every ten days.  Today is the day of
// the performance, assumed to be a Friday, and we want to know when the
// previous one took place and when the next one will be.
//
// First, we create a `bdlt::DayOfWeek` variable for the current day:
// ```
// bdlt::DayOfWeek::Enum current = bdlt::DayOfWeek::e_FRI;
// ```
// Next, we calculate previous and following event days using the
// `bdlt::DayOfWeekUtil::add` function:
// ```
// bdlt::DayOfWeek::Enum previous  = bdlt::DayOfWeekUtil::add(current, -10);
// bdlt::DayOfWeek::Enum following = bdlt::DayOfWeekUtil::add(current,  10);
// ```
// Finally, we verify the resultant day-of-week values:
// ```
// assert(bdlt::DayOfWeek::e_TUE == previous );
// assert(bdlt::DayOfWeek::e_MON == following);
// ```

#include <bdlscm_version.h>

#include <bdlt_dayofweek.h>

#include <bsls_cpp11.h>

namespace BloombergLP {
namespace bdlt {

                            // ====================
                            // struct DayOfWeekUtil
                            // ====================

/// This `struct` provides a namespace for common non-primitive procedures
/// that operate on `bdlt::DayOfWeek::Enum` values.
struct DayOfWeekUtil {

    // CLASS METHODS

    /// Return the `DayOfWeek::Enum` value that is the specified (signed)
    /// `numDays` from the specified `dayOfWeek`.  Note that
    /// `DayOfWeek::Enum` is closed under this operation (in the expected
    /// manner).  For example, the following hold `true`:
    /// ```
    /// DayOfWeek::e_MON == DayOfWeekUtil::add(DayOfWeek::e_SUN,  1);
    /// DayOfWeek::e_SAT == DayOfWeekUtil::add(DayOfWeek::e_SUN, -1);
    /// DayOfWeek::e_SAT == DayOfWeekUtil::add(DayOfWeek::e_SUN,  6);
    /// DayOfWeek::e_MON == DayOfWeekUtil::add(DayOfWeek::e_SUN, -6);
    /// DayOfWeek::e_SUN == DayOfWeekUtil::add(DayOfWeek::e_SUN,  7);
    /// DayOfWeek::e_SUN == DayOfWeekUtil::add(DayOfWeek::e_SUN, -7);
    /// DayOfWeek::e_MON == DayOfWeekUtil::add(DayOfWeek::e_SUN,  8);
    /// DayOfWeek::e_SAT == DayOfWeekUtil::add(DayOfWeek::e_SUN, -8);
    /// ```
    static BSLS_CPP11_CONSTEXPR DayOfWeek::Enum add(DayOfWeek::Enum dayOfWeek,
                                                    int             numDays);
};

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

                            // --------------------
                            // struct DayOfWeekUtil
                            // --------------------

// CLASS METHODS
inline
BSLS_CPP11_CONSTEXPR DayOfWeek::Enum DayOfWeekUtil::add(
                                                     DayOfWeek::Enum dayOfWeek,
                                                     int             numDays)
{
    // The '+ 7' prevents a negative result.

    return static_cast<DayOfWeek::Enum>(
                  (static_cast<int>(dayOfWeek) - 1 + numDays % 7 + 7) % 7 + 1);
}

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

#endif

// ----------------------------------------------------------------------------
// Copyright 2018 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 ----------------------------------
