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// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
#pragma once
#if !defined(RXCPP_OPERATORS_RX_SWITCH_IF_EMPTY_HPP)
#define RXCPP_OPERATORS_RX_SWITCH_IF_EMPTY_HPP
#include "../rx-includes.hpp"
namespace rxcpp {
namespace operators {
namespace detail {
template<class T, class BackupSource>
struct switch_if_empty
{
typedef rxu::decay_t<T> source_value_type;
typedef rxu::decay_t<BackupSource> backup_source_type;
backup_source_type backup;
switch_if_empty(backup_source_type b)
: backup(std::move(b))
{
}
template<class Subscriber>
struct switch_if_empty_observer
{
typedef switch_if_empty_observer<Subscriber> this_type;
typedef source_value_type value_type;
typedef rxu::decay_t<Subscriber> dest_type;
typedef observer<value_type, this_type> observer_type;
dest_type dest;
composite_subscription lifetime;
backup_source_type backup;
mutable bool is_empty;
switch_if_empty_observer(dest_type d, composite_subscription cs, backup_source_type b)
: dest(std::move(d))
, lifetime(std::move(cs))
, backup(std::move(b))
, is_empty(true)
{
dest.add(lifetime);
}
void on_next(source_value_type v) const {
is_empty = false;
dest.on_next(std::move(v));
}
void on_error(std::exception_ptr e) const {
dest.on_error(std::move(e));
}
void on_completed() const {
if(!is_empty) {
dest.on_completed();
} else {
backup.subscribe(dest);
}
}
static subscriber<value_type, observer_type> make(dest_type d, backup_source_type b) {
auto cs = composite_subscription();
return make_subscriber<value_type>(cs, observer_type(this_type(std::move(d), cs, std::move(b))));
}
};
template<class Subscriber>
auto operator()(Subscriber dest) const
-> decltype(switch_if_empty_observer<Subscriber>::make(std::move(dest), std::move(backup))) {
return switch_if_empty_observer<Subscriber>::make(std::move(dest), std::move(backup));
}
};
template<class BackupSource>
class switch_if_empty_factory
{
typedef rxu::decay_t<BackupSource> backup_source_type;
backup_source_type backup;
public:
switch_if_empty_factory(backup_source_type b) : backup(std::move(b)) {}
template<class Observable>
auto operator()(Observable&& source)
-> decltype(source.template lift<rxu::value_type_t<rxu::decay_t<Observable>>>(switch_if_empty<rxu::value_type_t<rxu::decay_t<Observable>>, backup_source_type>(backup))) {
return source.template lift<rxu::value_type_t<rxu::decay_t<Observable>>>(switch_if_empty<rxu::value_type_t<rxu::decay_t<Observable>>, backup_source_type>(backup));
}
};
}
template<class BackupSource>
auto switch_if_empty(BackupSource&& b)
-> detail::switch_if_empty_factory<BackupSource> {
return detail::switch_if_empty_factory<BackupSource>(std::forward<BackupSource>(b));
}
}
}
#endif
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