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#ifndef _CPPROMISE_HPP
#define _CPPROMISE_HPP
#include <vector>
#include <memory>
#include <any>
#include <functional>
template <typename T>
struct function_traits:
public function_traits<decltype(&T::operator())> {};
template <typename ClassType, typename ReturnType, typename ArgType>
struct function_traits<ReturnType(ClassType::*)(ArgType) const>
{
using ret_type = ReturnType;
using arg_type = ArgType;
};
/** Implement type-safe Promise primitives similar to the ones specified by
* Javascript A+. */
namespace promise {
using std::function;
using pm_any_t = std::any;
using None = std::nullptr_t;
using values_t = std::vector<pm_any_t>;
const auto none = nullptr;
const auto do_nothing = [](){};
class Promise;
class promise_t {
std::shared_ptr<Promise> ptr;
public:
template<typename Func>
promise_t(Func callback) {
ptr = std::make_shared<Promise>();
callback(*this);
}
template<typename T> inline void resolve(T result) const;
template<typename T> inline void reject(T reason) const;
template<typename FuncFulfilled, typename FuncRejected>
inline promise_t then_any(FuncFulfilled fulfilled_callback,
FuncRejected rejected_callback) const;
template<typename FuncFulfilled>
inline promise_t then_any(FuncFulfilled fulfilled_callback) const;
template<typename FuncRejected>
inline promise_t fail_any(FuncRejected rejected_callback) const;
template<typename FuncFulfilled>
inline promise_t then(FuncFulfilled on_fulfilled) const;
template<typename FuncFulfilled, typename FuncRejected>
inline promise_t then(FuncFulfilled on_fulfilled,
FuncRejected on_rejected) const;
template<typename FuncRejected>
inline promise_t fail(FuncRejected on_rejected) const;
};
#define PROMISE_ERR_INVALID_STATE do {throw std::runtime_error("invalid promise state");} while (0)
#define PROMISE_ERR_MISMATCH_TYPE do {throw std::runtime_error("mismatching promise value types");} while (0)
class Promise {
//function<void()> fulfilled_callback;
//function<void()> rejected_callback;
std::vector<function<void()>> fulfilled_callbacks;
std::vector<function<void()>> rejected_callbacks;
enum class State {
Pending,
Fulfilled,
Rejected,
} state;
pm_any_t result;
pm_any_t reason;
/* this implementation causes stack overflow because of the nested lambdas */
/*
void add_on_fulfilled(function<void()> cb) {
auto old_cbs = fulfilled_callback;
fulfilled_callback = function<void()>(
[cb, old_cbs]() {
old_cbs();
cb();
});
}
void add_on_rejected(function<void()> cb) {
auto old_cbs = rejected_callback;
rejected_callback = function<void()>(
[cb, old_cbs]() {
old_cbs();
cb();
});
}
*/
void add_on_fulfilled(function<void()> cb) {
fulfilled_callbacks.push_back(cb);
}
void add_on_rejected(function<void()> cb) {
rejected_callbacks.push_back(cb);
}
template<typename Func>
typename std::enable_if<
std::is_same<typename function_traits<Func>::ret_type,
promise_t>::value>::type
gen_on_fulfilled(Func on_fulfilled, const promise_t &npm, function<void()> &ret) {
ret = [this, on_fulfilled, npm]() {
on_fulfilled(result).then_any(
[npm] (pm_any_t result_) {
npm.resolve(result_);
return pm_any_t(none);
},
[npm] (pm_any_t reason_) {
npm.reject(reason_);
return pm_any_t(none);
});
};
}
template<typename Func>
typename std::enable_if<
std::is_same<typename function_traits<Func>::ret_type,
pm_any_t>::value>::type
gen_on_fulfilled(Func on_fulfilled, const promise_t &npm, function<void()> &ret) {
ret = [this, on_fulfilled, npm]() {
npm.resolve(on_fulfilled(result));
};
}
template<typename Func>
typename std::enable_if<
std::is_same<typename function_traits<Func>::ret_type,
promise_t>::value>::type
gen_on_rejected(Func on_rejected, const promise_t &npm, function<void()> &ret) {
ret = [this, on_rejected, npm]() {
on_rejected(reason).then_any(
[npm] (pm_any_t result_) {
npm.resolve(result_);
return none;
},
[npm] (pm_any_t reason_) {
npm.reject(reason_);
return none;
});
};
}
template<typename Func>
typename std::enable_if<
std::is_same<typename function_traits<Func>::ret_type,
pm_any_t>::value>::type
gen_on_rejected(Func on_rejected, const promise_t &npm, function<void()> &ret) {
ret = [this, on_rejected, npm]() {
npm.reject(on_rejected(reason));
};
}
public:
Promise():
/*
fulfilled_callback(do_nothing),
rejected_callback(do_nothing),
*/
state(State::Pending) {
//printf("%lx constructed\n", (uintptr_t)this);
}
~Promise() {
//printf("%lx freed\n", (uintptr_t)this);
}
template<typename FuncFulfilled, typename FuncRejected>
promise_t then(FuncFulfilled on_fulfilled,
FuncRejected on_rejected) {
switch (state)
{
case State::Pending:
return promise_t([this, on_fulfilled, on_rejected](promise_t npm) {
function<void()> ret;
gen_on_fulfilled(on_fulfilled, npm, ret);
add_on_fulfilled(ret);
gen_on_rejected(on_rejected, npm, ret);
add_on_rejected(ret);
});
case State::Fulfilled:
return promise_t([this, on_fulfilled](promise_t npm) {
function<void()> ret;
gen_on_fulfilled(on_fulfilled, npm, ret);
ret();
});
case State::Rejected:
return promise_t([this, on_rejected](promise_t npm) {
function<void()> ret;
gen_on_rejected(on_rejected, npm, ret);
ret();
});
default: PROMISE_ERR_INVALID_STATE;
}
}
template<typename FuncFulfilled>
promise_t then(FuncFulfilled on_fulfilled) {
switch (state)
{
case State::Pending:
return promise_t([this, on_fulfilled](promise_t npm) {
function<void()> ret;
gen_on_fulfilled(on_fulfilled, npm, ret);
add_on_fulfilled(ret);
add_on_rejected([this, npm]() {npm.reject(reason);});
});
case State::Fulfilled:
return promise_t([this, on_fulfilled](promise_t npm) {
function<void()> ret;
gen_on_fulfilled(on_fulfilled, npm, ret);
ret();
});
case State::Rejected:
return promise_t([this](promise_t npm) {npm.reject(reason);});
default: PROMISE_ERR_INVALID_STATE;
}
}
template<typename FuncRejected>
promise_t fail(FuncRejected on_rejected) {
switch (state)
{
case State::Pending:
return promise_t([this, on_rejected](promise_t npm) {
function<void()> ret;
gen_on_rejected(on_rejected, npm, ret);
add_on_rejected(ret);
add_on_fulfilled([this, npm]() {npm.resolve(result);});
});
case State::Fulfilled:
return promise_t([this](promise_t npm) {npm.resolve(result);});
case State::Rejected:
return promise_t([this, on_rejected](promise_t npm) {
function<void()> ret;
gen_on_rejected(on_rejected, npm, ret);
ret();
});
default: PROMISE_ERR_INVALID_STATE;
}
}
void resolve(pm_any_t _result) {
switch (state
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