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//
 
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// Copyright (c) 2026 Michael Vandeberg
 
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//
 
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
 
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
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//
 
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// Official repository: https://github.com/cppalliance/capy
 
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//
 
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#include <boost/capy/ex/detail/timer_service.hpp>
 
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namespace boost {
 
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namespace capy {
 
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namespace detail {
 
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timer_service::
 
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timer_service(execution_context& ctx)
 
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    : thread_([this] { run(); })
 
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{
 
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    (void)ctx;
 
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}
 
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timer_service::timer_id
 
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timer_service::
 
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schedule_at(
 
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    std::chrono::steady_clock::time_point deadline,
 
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    std::function<void()> cb)
 
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{
 
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    std::lock_guard lock(mutex_);
 
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    auto id = ++next_id_;
 
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    active_ids_.insert(id);
 
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    queue_.push(entry{deadline, id, std::move(cb)});
 
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    cv_.notify_one();
 
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    return id;
 
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}
 
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void
 
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timer_service::
 
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cancel(timer_id id)
 
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{
 
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    std::unique_lock lock(mutex_);
 
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    if(!active_ids_.contains(id))
 
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        return;
 
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    if(executing_id_ == id)
 
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    {
 
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        // Callback is running — wait for it to finish.
 
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        // run() erases from active_ids_ after execution.
 
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        while(executing_id_ == id)
 
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            cancel_cv_.wait(lock);
 
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        return;
 
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    }
 
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    active_ids_.erase(id);
 
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}
 
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void
 
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timer_service::
 
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shutdown()
 
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{
 
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    {
 
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        std::lock_guard lock(mutex_);
 
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        stopped_ = true;
 
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    }
 
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    cv_.notify_one();
 
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    if(thread_.joinable())
 
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        thread_.join();
 
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}
 
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void
 
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timer_service::
 
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run()
 
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{
 
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    std::unique_lock lock(mutex_);
 
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    for(;;)
 
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    {
 
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        if(stopped_)
 
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            return;
 
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        if(queue_.empty())
 
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        {
 
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            cv_.wait(lock);
 
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            continue;
 
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        }
 
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        auto deadline = queue_.top().deadline;
 
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        auto now = std::chrono::steady_clock::now();
 
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        if(deadline > now)
 
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        {
 
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            cv_.wait_until(lock, deadline);
 
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            continue;
 
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        }
 
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        // Pop the entry (const_cast needed because priority_queue::top is const)
 
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        auto e = std::move(const_cast<entry&>(queue_.top()));
 
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        queue_.pop();
 
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        // Skip if cancelled (no longer in active set)
 
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        if(!active_ids_.contains(e.id))
 
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            continue;
 
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        executing_id_ = e.id;
 
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        lock.unlock();
 
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        e.callback();
 
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        lock.lock();
 
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        active_ids_.erase(e.id);
 
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        executing_id_ = 0;
 
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        cancel_cv_.notify_all();
 
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    }
 
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}
 
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} // detail
 
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} // capy
 
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} // boost