Kylin/Universal/Private/PromiseHandler.h

#ifndef __PROMISEHANDLER_H__
#define __PROMISEHANDLER_H__

#include "../FunctionTraits.h"
#include <type_traits>
#include <exception>
#include "PromiseData.h"

template <typename T>
class Promise;

template <typename T>
struct PromiseDeduce {
    using Type = Promise<T>;
};

template <typename T>
struct PromiseDeduce<T &> : public PromiseDeduce<T> {};

template <typename T>
struct PromiseDeduce<const T> : public PromiseDeduce<T> {};

template <typename T>
struct PromiseDeduce<const volatile T> : public PromiseDeduce<T> {};

template <typename T>
struct PromiseDeduce<Promise<T>> : public PromiseDeduce<T> {};

template <typename T>
struct PromiseFulfill {
    template <typename V, typename TResolve, typename TReject>
    static void call(V &&value, const TResolve &resolve, const TReject &) {
        resolve(std::forward<V>(value));
    }
};

template <typename T>
struct PromiseFulfill<Promise<T>> {
    template <typename TResolve, typename TReject>
    static void call(const Promise<T> &promise, const TResolve &resolve, const TReject &reject) {
        if (promise.isFulfilled()) {
            resolve(promise.m_d->value());
        } else if (promise.isRejected()) {
            reject(promise.m_d->error());
        } else {
            promise.then([=]() { resolve(promise.m_d->value()); },
                         [=]() { // catch all
                             reject(promise.m_d->error());
                         });
        }
    }
};

template <>
struct PromiseFulfill<Promise<void>> {
    template <typename TPromise, typename TResolve, typename TReject>
    static void call(const TPromise &promise, const TResolve &resolve, const TReject &reject) {
        if (promise.isFulfilled()) {
            resolve();
        } else if (promise.isRejected()) {
            reject(promise.m_d->error());
        } else {
            promise.then([=]() { resolve(); },
                         [=]() { // catch all
                             reject(promise.m_d->error());
                         });
        }
    }
};

template <typename Result>
struct PromiseDispatch {
    template <typename Resolve, typename Reject, typename Functor, typename... Args>
    static void call(const Resolve &resolve, const Reject &reject, Functor fn, Args &&...args) {
        try {
            PromiseFulfill<std::decay_t<Result>>::call(fn(std::forward<Args>(args)...), resolve, reject);
        } catch (...) {
            reject(std::current_exception());
        }
    }
};

template <>
struct PromiseDispatch<void> {
    template <typename Resolve, typename Reject, typename Functor, typename... Args>
    static void call(const Resolve &resolve, const Reject &reject, Functor fn, Args &&...args) {
        try {
            fn(std::forward<Args>(args)...);
            resolve();
        } catch (...) {
            reject(std::current_exception());
        }
    }
};

template <typename T, typename THandler, typename TArg = typename ArgsOf<THandler>::first>
struct PromiseHandler {
    using ResType = std::invoke_result_t<THandler, T>;
    using PromiseType = typename PromiseDeduce<ResType>::Type;

    template <typename TResolve, typename TReject>
    static std::function<void(const T &)> create(const THandler &handler, const TResolve &resolve, const TReject &reject) {
        return [=](const T &value) { PromiseDispatch<ResType>::call(resolve, reject, handler, value); };
    }
};

template <typename T, typename THandler>
struct PromiseHandler<T, THandler, void> {
    using ResType = std::invoke_result_t<THandler>;
    using PromiseType = typename PromiseDeduce<ResType>::Type;

    template <typename TResolve, typename TReject>
    static std::function<void(const T &)> create(const THandler &handler, const TResolve &resolve, const TReject &reject) {
        return [=](const T &) { PromiseDispatch<ResType>::call(resolve, reject, handler); };
    }
};

template <typename THandler>
struct PromiseHandler<void, THandler, void> {
    using ResType = std::invoke_result_t<THandler>;
    using PromiseType = typename PromiseDeduce<ResType>::Type;

    template <typename TResolve, typename TReject>
    static std::function<void()> create(const THandler &handler, const TResolve &resolve, const TReject &reject) {
        return [=]() { PromiseDispatch<ResType>::call(resolve, reject, handler); };
    }
};

template <typename T>
struct PromiseHandler<T, std::nullptr_t, void> {
    using PromiseType = Promise<T>;

    template <typename TResolve, typename TReject>
    static std::function<void(const T &)> create(std::nullptr_t, const TResolve &resolve, const TReject &reject) {
        return [=](const T &value) {
            // 2.2.7.3. If onFulfilled is not a function and promise1 is fulfilled,
            // promise2 must be fulfilled with the same value as promise1.
            PromiseFulfill<T>::call(std::move(T(value)), resolve, reject);
        };
    }
};

template <>
struct PromiseHandler<void, std::nullptr_t, void> {
    using PromiseType = Promise<void>;

    template <typename TResolve, typename TReject>
    static std::function<void()> create(std::nullptr_t, const TResolve &resolve, const TReject &) {
        return [=]() {
            // 2.2.7.3. If onFulfilled is not a function and promise1 is fulfilled,
            // promise2 must be fulfilled with the same value as promise1.
            resolve();
        };
    }
};

template <typename T, typename THandler, typename TArg = typename ArgsOf<THandler>::first>
struct PromiseCatcher {
    using ResType = std::invoke_result_t<THandler, TArg>;

    template <typename TResolve, typename TReject>
    static std::function<void(const PromiseError &)> create(const THandler &handler, const TResolve &resolve, const TReject &reject) {
        return [=](const PromiseError &error) {
            try {
                error.rethrow();
            } catch (const TArg &argError) {
                PromiseDispatch<ResType>::call(resolve, reject, handler, argError);
            } catch (...) {
                reject(std::current_exception());
            }
        };
    }
};

template <typename T, typename THandler>
struct PromiseCatcher<T, THandler, void> {
    using ResType = typename std::invoke_result_t<THandler>;

    template <typename TResolve, typename TReject>
    static std::function<void(const PromiseError &)> create(const THandler &handler, const TResolve &resolve, const TReject &reject) {
        return [=](const PromiseError &error) {
            try {
                error.rethrow();
            } catch (...) {
                PromiseDispatch<ResType>::call(resolve, reject, handler);
            }
        };
    }
};

template <typename T>
struct PromiseCatcher<T, std::nullptr_t, void> {
    template <typename TResolve, typename TReject>
    static std::function<void(const PromiseError &)> create(std::nullptr_t, const TResolve &, const TReject &reject) {
        return [=](const PromiseError &error) {
            // 2.2.7.4. If onRejected is not a function and promise1 is rejected,
            // promise2 must be rejected with the same reason as promise1
            reject(error);
        };
    }
};

#endif // __PROMISEHANDLER_H__