// bdlt_defaultcalendarcache.h                                        -*-C++-*-
#ifndef INCLUDED_BDLT_DEFAULTCALENDARCACHE
#define INCLUDED_BDLT_DEFAULTCALENDARCACHE

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

//@PURPOSE: Provide a process-wide default `bdlt::CalendarCache` object.
//
//@CLASSES:
//  bdlt::DefaultCalendarCache: namespace for managing a default calendar cache
//
//@SEE_ALSO: bdlt_calendarcache, bdlt_calendarloader
//
//@DESCRIPTION: This component provides a namespace,
// `bdlt::DefaultCalendarCache`, for utility functions that initialize, provide
// access to, and ultimately destroy, a default `bdlt::CalendarCache` object.
// The default cache is initialized by calling the (overloaded) `initialize`
// class method to which a concrete calendar loader and memory allocator must
// be supplied.  The cache is destroyed by the `destroy` class method.  Note
// that the calendar-naming convention in effect for the default cache is
// determined by the loader supplied to `initialize`.
//
// A timeout may be established for the default cache by supplying an optional
// `bsls::TimeInterval` value to `initialize`.  When a timeout is in effect for
// the default cache, a request for a calendar from the cache may incur the
// reloading of the calendar if the one in the cache has expired (i.e., the
// time interval defined by the timeout value has elapsed since the calendar
// was last loaded into the cache).  Calendars will not expire in this fashion
// if the default cache is not provided with a timeout at initialization.
//
// Although the cache may be initialized and destroyed multiple times during
// the lifetime of a process, the expected usage is that the cache would be
// initialized *once*, typically in `main` before other threads have been
// created, and destroyed just prior to program termination.  Regardless, the
// lifetimes of the calendar loader and memory allocator supplied to
// `initialize` must extend beyond the following (matching) call to `destroy`.
// While the default calendar cache is in the initialized state, the `instance`
// method returns an address providing modifiable access to the cache.
// Otherwise, `instance` returns 0.
//
// **WARNING**: Clients should be aware that the address returned by `instance`
// becomes invalid by a subsequent call to `destroy`.
//
///Thread Safety
///-------------
// The `bdlt::DefaultCalendarCache` class is fully thread-safe (see
// `bsldoc_glossary`) provided that the allocator supplied to `initialize` and
// the default allocator in effect during the lifetime of the default cache are
// both fully thread-safe.
//
///Usage
///-----
// The following example illustrates how to use `bdlt::DefaultCalendarCache`.
//
///Example 1: Using `bdlt::DefaultCalendarCache`
///- - - - - - - - - - - - - - - - - - - - - - -
// `bdlt::DefaultCalendarCache` has a particularly simple interface.  This
// example shows how to use each of its three methods.
//
// A hypothetical calendar loader is assumed, `MyCalendarLoader`, the details
// of which are not important other than that it supports calendars identified
// by "DE", "FR", and "US", which nominally identify the major holidays in
// Germany, France, and the United States, respectively.  Furthermore, we cite
// two specific dates of interest: 2011/07/04, which was a holiday in the US
// (Independence Day), but not in France, and 2011/07/14, which was a holiday
// in France (Bastille Day), but not in the US.
//
// First, we create a calendar loader, an instance of `MyCalendarLoader`, and
// use it, in turn, to initialize the default calendar cache.  A memory
// allocator must also be explicitly supplied to the `initialize` method.  The
// global allocator is suitable in this case (see `bslma_default`):
// ```
// static MyCalendarLoader loader;
//
// int rc = bdlt::DefaultCalendarCache::initialize(
//                                         &loader,
//                                         bslma::Default::globalAllocator());
// assert(!rc);
// ```
// Note that declaring `loader` to be `static` ensures that it remains valid
// until the cache is destroyed.  Also note that initialization of the cache
// would typically be done in `main` before other threads have been created.
//
// Next, we obtain the address of the default calendar cache using the
// `instance` class method:
// ```
// bdlt::CalendarCache *cachePtr = bdlt::DefaultCalendarCache::instance();
// assert(cachePtr);
// ```
// Then, we retrieve the calendar identified by "US" from the default cache,
// and verify that 2011/07/04 is recognized as a holiday in the "US" calendar,
// whereas 2011/07/14 is not:
// ```
// bsl::shared_ptr<const bdlt::Calendar> us = cachePtr->getCalendar("US");
// assert( us->isHoliday(bdlt::Date(2011, 7,  4)));
// assert(!us->isHoliday(bdlt::Date(2011, 7, 14)));
// ```
// Next, we fetch the calendar identified by "FR", this time verifying that
// 2011/07/14 is recognized as a holiday in the "FR" calendar, but 2011/07/04
// is not:
// ```
// bsl::shared_ptr<const bdlt::Calendar> fr = cachePtr->getCalendar("FR");
// assert(!fr->isHoliday(bdlt::Date(2011, 7,  4)));
// assert( fr->isHoliday(bdlt::Date(2011, 7, 14)));
// ```
// Finally, we destroy the default calendar cache:
// ```
// bdlt::DefaultCalendarCache::destroy();
// assert(!bdlt::DefaultCalendarCache::instance());
// ```
// Note that destruction of the default cache would typically be done in `main`
// just prior to program termination.

#include <bdlscm_version.h>

#include <bsls_timeinterval.h>

#include <bslma_allocator.h>

namespace BloombergLP {


namespace bdlt {

class CalendarCache;
class CalendarLoader;

                      // ==========================
                      // class DefaultCalendarCache
                      // ==========================

/// This `struct` provides a namespace for functions that manage the
/// lifetime of, and access to, a process-wide default `bdlt::CalendarCache`
/// object.  The default cache is initialized by an explicit call to the
/// `initialize` class method, and destroyed by the `destroy` class method.
/// The default cache may be initialized and destroyed multiple times during
/// the lifetime of a process.  The lifetimes of the calendar loader and
/// memory allocator supplied to `initialize` must extend beyond the
/// following (matching) call to `destroy`.
///
/// All methods of this `struct` are fully thread-safe (see
/// `bsldoc_glossary`).
struct DefaultCalendarCache {

    // CLASS METHODS

    /// Destroy the default `CalendarCache` object managed by this class.
    /// If the default cache is not in the initialized state, this method
    /// has no effect.  Note that all addresses returned by earlier calls to
    /// `instance` are invalidated by this method.
    static void destroy();

    /// Initialize the default `CalendarCache` object managed by this class
    /// to use the specified `loader` to obtain calendars, to have no
    /// timeout, and to use the specified `allocator` to supply memory.  If
    /// the default cache is already in the initialized state, this method
    /// has no effect.  Return 0 on success, and a non-zero value otherwise.
    /// The behavior is undefined unless `loader` and `allocator` remain
    /// valid until a subsequent call to `destroy`.
    static int initialize(CalendarLoader   *loader,
                          bslma::Allocator *allocator);

    /// Initialize the default `CalendarCache` object managed by this class
    /// to use the specified `loader` to obtain calendars, to have the
    /// specified `timeout`, and to use the specified `allocator` to supply
    /// memory.  If the default cache is already in the initialized state,
    /// this method has no effect.  Return 0 on success, and a non-zero
    /// value otherwise.  The behavior is undefined unless `loader` and
    /// `allocator` remain valid until a subsequent call to `destroy`, and
    /// `bsls::TimeInterval() <= timeout <= bsls::TimeInterval(INT_MAX, 0)`.
    /// Note that a `timeout` value of 0 indicates that a calendar will be
    /// loaded into the default cache by *each* (successful) call to
    /// `CalendarCache::getCalendar` on the cache returned by `instance`.
    static int initialize(CalendarLoader            *loader,
                          const bsls::TimeInterval&  timeout,
                          bslma::Allocator          *allocator);

    /// Return an address providing modifiable access to the default
    /// `CalendarCache` object managed by this class, if the default cache
    /// is in the initialized state, and 0 otherwise.  The cache obtains
    /// calendars using the loader that was supplied to the `initialize`
    /// method.  Note that the returned address is invalidated by a
    /// subsequent call to `destroy`.
    static CalendarCache *instance();
};

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

}  // 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 ----------------------------------
