From 3bf42c6ff3805a0d42bbc661794a95ff31bedc26 Mon Sep 17 00:00:00 2001
From: untodesu <kirill@untode.su>
Date: Sat, 15 Mar 2025 16:22:09 +0500
Subject: Add whatever I was working on for the last month

---
 deps/include/entt/process/scheduler.hpp | 364 ++++++++++++++++++++++++++++++++
 1 file changed, 364 insertions(+)
 create mode 100644 deps/include/entt/process/scheduler.hpp

(limited to 'deps/include/entt/process/scheduler.hpp')

diff --git a/deps/include/entt/process/scheduler.hpp b/deps/include/entt/process/scheduler.hpp
new file mode 100644
index 0000000..6cd27db
--- /dev/null
+++ b/deps/include/entt/process/scheduler.hpp
@@ -0,0 +1,364 @@
+#ifndef ENTT_PROCESS_SCHEDULER_HPP
+#define ENTT_PROCESS_SCHEDULER_HPP
+
+#include <cstddef>
+#include <memory>
+#include <type_traits>
+#include <utility>
+#include <vector>
+#include "../config/config.h"
+#include "../core/compressed_pair.hpp"
+#include "fwd.hpp"
+#include "process.hpp"
+
+namespace entt {
+
+/*! @cond TURN_OFF_DOXYGEN */
+namespace internal {
+
+template<typename Delta>
+struct basic_process_handler {
+    virtual ~basic_process_handler() noexcept = default;
+
+    virtual bool update(const Delta, void *) = 0;
+    virtual void abort(const bool) = 0;
+
+    // std::shared_ptr because of its type erased allocator which is useful here
+    std::shared_ptr<basic_process_handler> next;
+};
+
+template<typename Delta, typename Type>
+struct process_handler final: basic_process_handler<Delta> {
+    template<typename... Args>
+    process_handler(Args &&...args)
+        : process{std::forward<Args>(args)...} {}
+
+    bool update(const Delta delta, void *data) override {
+        if(process.tick(delta, data); process.rejected()) {
+            this->next.reset();
+        }
+
+        return (process.rejected() || process.finished());
+    }
+
+    void abort(const bool immediate) override {
+        process.abort(immediate);
+    }
+
+    Type process;
+};
+
+} // namespace internal
+/*! @endcond */
+
+/**
+ * @brief Cooperative scheduler for processes.
+ *
+ * A cooperative scheduler runs processes and helps managing their life cycles.
+ *
+ * Each process is invoked once per tick. If a process terminates, it's
+ * removed automatically from the scheduler and it's never invoked again.<br/>
+ * A process can also have a child. In this case, the process is replaced with
+ * its child when it terminates if it returns with success. In case of errors,
+ * both the process and its child are discarded.
+ *
+ * Example of use (pseudocode):
+ *
+ * @code{.cpp}
+ * scheduler.attach([](auto delta, void *, auto succeed, auto fail) {
+ *     // code
+ * }).then<my_process>(arguments...);
+ * @endcode
+ *
+ * In order to invoke all scheduled processes, call the `update` member function
+ * passing it the elapsed time to forward to the tasks.
+ *
+ * @sa process
+ *
+ * @tparam Delta Type to use to provide elapsed time.
+ * @tparam Allocator Type of allocator used to manage memory and elements.
+ */
+template<typename Delta, typename Allocator>
+class basic_scheduler {
+    template<typename Type>
+    using handler_type = internal::process_handler<Delta, Type>;
+
+    // std::shared_ptr because of its type erased allocator which is useful here
+    using process_type = std::shared_ptr<internal::basic_process_handler<Delta>>;
+
+    using alloc_traits = std::allocator_traits<Allocator>;
+    using container_allocator = typename alloc_traits::template rebind_alloc<process_type>;
+    using container_type = std::vector<process_type, container_allocator>;
+
+public:
+    /*! @brief Allocator type. */
+    using allocator_type = Allocator;
+    /*! @brief Unsigned integer type. */
+    using size_type = std::size_t;
+    /*! @brief Unsigned integer type. */
+    using delta_type = Delta;
+
+    /*! @brief Default constructor. */
+    basic_scheduler()
+        : basic_scheduler{allocator_type{}} {}
+
+    /**
+     * @brief Constructs a scheduler with a given allocator.
+     * @param allocator The allocator to use.
+     */
+    explicit basic_scheduler(const allocator_type &allocator)
+        : handlers{allocator, allocator} {}
+
+    /*! @brief Default copy constructor, deleted on purpose. */
+    basic_scheduler(const basic_scheduler &) = delete;
+
+    /**
+     * @brief Move constructor.
+     * @param other The instance to move from.
+     */
+    basic_scheduler(basic_scheduler &&other) noexcept
+        : handlers{std::move(other.handlers)} {}
+
+    /**
+     * @brief Allocator-extended move constructor.
+     * @param other The instance to move from.
+     * @param allocator The allocator to use.
+     */
+    basic_scheduler(basic_scheduler &&other, const allocator_type &allocator)
+        : handlers{container_type{std::move(other.handlers.first()), allocator}, allocator} {
+        ENTT_ASSERT(alloc_traits::is_always_equal::value || get_allocator() == other.get_allocator(), "Copying a scheduler is not allowed");
+    }
+
+    /*! @brief Default destructor. */
+    ~basic_scheduler() noexcept = default;
+
+    /**
+     * @brief Default copy assignment operator, deleted on purpose.
+     * @return This process scheduler.
+     */
+    basic_scheduler &operator=(const basic_scheduler &) = delete;
+
+    /**
+     * @brief Move assignment operator.
+     * @param other The instance to move from.
+     * @return This process scheduler.
+     */
+    basic_scheduler &operator=(basic_scheduler &&other) noexcept {
+        ENTT_ASSERT(alloc_traits::is_always_equal::value || get_allocator() == other.get_allocator(), "Copying a scheduler is not allowed");
+        handlers = std::move(other.handlers);
+        return *this;
+    }
+
+    /**
+     * @brief Exchanges the contents with those of a given scheduler.
+     * @param other Scheduler to exchange the content with.
+     */
+    void swap(basic_scheduler &other) {
+        using std::swap;
+        swap(handlers, other.handlers);
+    }
+
+    /**
+     * @brief Returns the associated allocator.
+     * @return The associated allocator.
+     */
+    [[nodiscard]] constexpr allocator_type get_allocator() const noexcept {
+        return handlers.second();
+    }
+
+    /**
+     * @brief Number of processes currently scheduled.
+     * @return Number of processes currently scheduled.
+     */
+    [[nodiscard]] size_type size() const noexcept {
+        return handlers.first().size();
+    }
+
+    /**
+     * @brief Returns true if at least a process is currently scheduled.
+     * @return True if there are scheduled processes, false otherwise.
+     */
+    [[nodiscard]] bool empty() const noexcept {
+        return handlers.first().empty();
+    }
+
+    /**
+     * @brief Discards all scheduled processes.
+     *
+     * Processes aren't aborted. They are discarded along with their children
+     * and never executed again.
+     */
+    void clear() {
+        handlers.first().clear();
+    }
+
+    /**
+     * @brief Schedules a process for the next tick.
+     *
+     * Returned value can be used to attach a continuation for the last process.
+     * The continutation is scheduled automatically when the process terminates
+     * and only if the process returns with success.
+     *
+     * Example of use (pseudocode):
+     *
+     * @code{.cpp}
+     * // schedules a task in the form of a process class
+     * scheduler.attach<my_process>(arguments...)
+     * // appends a child in the form of a lambda function
+     * .then([](auto delta, void *, auto succeed, auto fail) {
+     *     // code
+     * })
+     * // appends a child in the form of another process class
+     * .then<my_other_process>();
+     * @endcode
+     *
+     * @tparam Proc Type of process to schedule.
+     * @tparam Args Types of arguments to use to initialize the process.
+     * @param args Parameters to use to initialize the process.
+     * @return This process scheduler.
+     */
+    template<typename Proc, typename... Args>
+    basic_scheduler &attach(Args &&...args) {
+        static_assert(std::is_base_of_v<process<Proc, Delta>, Proc>, "Invalid process type");
+        auto &ref = handlers.first().emplace_back(std::allocate_shared<handler_type<Proc>>(handlers.second(), std::forward<Args>(args)...));
+        // forces the process to exit the uninitialized state
+        ref->update({}, nullptr);
+        return *this;
+    }
+
+    /**
+     * @brief Schedules a process for the next tick.
+     *
+     * A process can be either a lambda or a functor. The scheduler wraps both
+     * of them in a process adaptor internally.<br/>
+     * The signature of the function call operator should be equivalent to the
+     * following:
+     *
+     * @code{.cpp}
+     * void(Delta delta, void *data, auto succeed, auto fail);
+     * @endcode
+     *
+     * Where:
+     *
+     * * `delta` is the elapsed time.
+     * * `data` is an opaque pointer to user data if any, `nullptr` otherwise.
+     * * `succeed` is a function to call when a process terminates with success.
+     * * `fail` is a function to call when a process terminates with errors.
+     *
+     * The signature of the function call operator of both `succeed` and `fail`
+     * is equivalent to the following:
+     *
+     * @code{.cpp}
+     * void();
+     * @endcode
+     *
+     * Returned value can be used to attach a continuation for the last process.
+     * The continutation is scheduled automatically when the process terminates
+     * and only if the process returns with success.
+     *
+     * Example of use (pseudocode):
+     *
+     * @code{.cpp}
+     * // schedules a task in the form of a lambda function
+     * scheduler.attach([](auto delta, void *, auto succeed, auto fail) {
+     *     // code
+     * })
+     * // appends a child in the form of another lambda function
+     * .then([](auto delta, void *, auto succeed, auto fail) {
+     *     // code
+     * })
+     * // appends a child in the form of a process class
+     * .then<my_process>(arguments...);
+     * @endcode
+     *
+     * @sa process_adaptor
+     *
+     * @tparam Func Type of process to schedule.
+     * @param func Either a lambda or a functor to use as a process.
+     * @return This process scheduler.
+     */
+    template<typename Func>
+    basic_scheduler &attach(Func &&func) {
+        using Proc = process_adaptor<std::decay_t<Func>, Delta>;
+        return attach<Proc>(std::forward<Func>(func));
+    }
+
+    /**
+     * @brief Sets a process as a continuation of the last scheduled process.
+     * @tparam Proc Type of process to use as a continuation.
+     * @tparam Args Types of arguments to use to initialize the process.
+     * @param args Parameters to use to initialize the process.
+     * @return This process scheduler.
+     */
+    template<typename Proc, typename... Args>
+    basic_scheduler &then(Args &&...args) {
+        static_assert(std::is_base_of_v<process<Proc, Delta>, Proc>, "Invalid process type");
+        ENTT_ASSERT(!handlers.first().empty(), "Process not available");
+        auto *curr = handlers.first().back().get();
+        for(; curr->next; curr = curr->next.get()) {}
+        curr->next = std::allocate_shared<handler_type<Proc>>(handlers.second(), std::forward<Args>(args)...);
+        return *this;
+    }
+
+    /**
+     * @brief Sets a process as a continuation of the last scheduled process.
+     * @tparam Func Type of process to use as a continuation.
+     * @param func Either a lambda or a functor to use as a process.
+     * @return This process scheduler.
+     */
+    template<typename Func>
+    basic_scheduler &then(Func &&func) {
+        using Proc = process_adaptor<std::decay_t<Func>, Delta>;
+        return then<Proc>(std::forward<Func>(func));
+    }
+
+    /**
+     * @brief Updates all scheduled processes.
+     *
+     * All scheduled processes are executed in no specific order.<br/>
+     * If a process terminates with success, it's replaced with its child, if
+     * any. Otherwise, if a process terminates with an error, it's removed along
+     * with its child.
+     *
+     * @param delta Elapsed time.
+     * @param data Optional data.
+     */
+    void update(const delta_type delta, void *data = nullptr) {
+        for(auto next = handlers.first().size(); next; --next) {
+            if(const auto pos = next - 1u; handlers.first()[pos]->update(delta, data)) {
+                // updating might spawn/reallocate, cannot hold refs until here
+                if(auto &curr = handlers.first()[pos]; curr->next) {
+                    curr = std::move(curr->next);
+                    // forces the process to exit the uninitialized state
+                    curr->update({}, nullptr);
+                } else {
+                    curr = std::move(handlers.first().back());
+                    handlers.first().pop_back();
+                }
+            }
+        }
+    }
+
+    /**
+     * @brief Aborts all scheduled processes.
+     *
+     * Unless an immediate operation is requested, the abort is scheduled for
+     * the next tick. Processes won't be executed anymore in any case.<br/>
+     * Once a process is fully aborted and thus finished, it's discarded along
+     * with its child, if any.
+     *
+     * @param immediate Requests an immediate operation.
+     */
+    void abort(const bool immediate = false) {
+        for(auto &&curr: handlers.first()) {
+            curr->abort(immediate);
+        }
+    }
+
+private:
+    compressed_pair<container_type, allocator_type> handlers;
+};
+
+} // namespace entt
+
+#endif
-- 
cgit