From a979e6d6d182850925c8dd65bd5f34c72063d895 Mon Sep 17 00:00:00 2001
From: Determinant <ted.sybil@gmail.com>
Date: Sat, 27 Jan 2018 18:36:09 -0500
Subject: init

---
 .gitignore  |   2 +
 Makefile    |   2 +
 promise.hpp | 327 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 test.cpp    |  79 +++++++++++++++
 4 files changed, 410 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 promise.hpp
 create mode 100644 test.cpp

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..9db44c8
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+*.hpp.gch
+test
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..9b09161
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,2 @@
+test: test.cpp promise.hpp
+	g++ -o test test.cpp -std=c++17
diff --git a/promise.hpp b/promise.hpp
new file mode 100644
index 0000000..e197803
--- /dev/null
+++ b/promise.hpp
@@ -0,0 +1,327 @@
+#ifndef _CPPROMISE_HPP
+#define _CPPROMISE_HPP
+
+#include <vector>
+#include <memory>
+#include <any>
+#include <functional>
+
+/** 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:
+        promise_t(function<void(promise_t)> 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 F_, typename F = pm_any_t, typename R_, typename R = pm_any_t>
+        inline promise_t then(function<F_(pm_any_t)> fulfilled_callback,
+                        function<R_(pm_any_t)> rejected_callback) const;
+
+        template<typename F_, typename F = pm_any_t>
+        inline promise_t then(function<F_(pm_any_t)> fulfilled_callback) const;
+
+        template<typename R_, typename R = pm_any_t>
+        inline promise_t fail(function<R_(pm_any_t)> rejected_callback) const;
+
+        template<typename F_, typename F>
+        inline promise_t then(function<F_(F)> on_fulfilled) const;
+
+        template<typename F_, typename F, typename R_, typename R>
+        inline promise_t then(function<F_(F)> on_fulfilled, function<R_(R)> on_rejected) const;
+
+        template<typename F_, typename F>
+        inline promise_t fail(function<F_(F)> on_fulfilled) 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;
+        enum class State {
+            Pending,
+            Fulfilled,
+            Rejected,
+        } state;
+        pm_any_t result;
+        pm_any_t reason;
+
+        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();
+                });
+        }
+
+        function<void()> gen_on_fulfilled(
+                function<promise_t(pm_any_t)> on_fulfilled,
+                const promise_t &npm) {
+            return [this, on_fulfilled, npm]() {
+                on_fulfilled(result).then(
+                    function<None(pm_any_t)>([npm] (pm_any_t result_) {
+                        npm.resolve(result_);
+                        return none;
+                    }),
+                    function<None(pm_any_t)>([npm] (pm_any_t reason_) {
+                        npm.reject(reason_);
+                        return none;
+                    }));
+            };
+        }
+
+        function<void()> gen_on_fulfilled(
+                function<pm_any_t(pm_any_t)> on_fulfilled,
+                const promise_t &npm) {
+            return [this, on_fulfilled, npm]() {
+                npm.resolve(on_fulfilled(result));
+            };
+        }
+
+        function<void()> gen_on_rejected(
+                function<promise_t(pm_any_t)> on_rejected,
+                const promise_t &npm) {
+            return [this, on_rejected, npm]() {
+                on_rejected(reason).then(
+                    function<None(pm_any_t)>([npm] (pm_any_t result_) {
+                        npm.resolve(result_);
+                        return none;
+                    }),
+                    function<None(pm_any_t)>([npm] (pm_any_t reason_) {
+                        npm.reject(reason_);
+                        return none;
+                    }));
+            };
+        }
+
+        function<void()> gen_on_rejected(
+                function<pm_any_t(pm_any_t)> on_rejected,
+                const promise_t &npm) {
+            return [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 OnFulfilled, typename OnRejected>
+        promise_t then(function<OnFulfilled(pm_any_t)> on_fulfilled,
+                      function<OnRejected(pm_any_t)> on_rejected) {
+            switch (state)
+            {
+                case State::Pending:
+                    return promise_t([this, on_fulfilled, on_rejected](promise_t npm) {
+                        add_on_fulfilled(gen_on_fulfilled(on_fulfilled, npm));
+                        add_on_rejected(gen_on_rejected(on_rejected, npm));
+                    });
+                case State::Fulfilled:
+                    return promise_t([this, on_fulfilled](promise_t npm) {
+                        gen_on_fulfilled(on_fulfilled, npm)();
+                    });
+                case State::Rejected:
+                    return promise_t([this, on_rejected](promise_t npm) {
+                        gen_on_rejected(on_rejected, npm)();
+                    });
+                default: PROMISE_ERR_INVALID_STATE;
+            }
+        }
+
+        template<typename OnFulfilled>
+        promise_t then(function<OnFulfilled(pm_any_t)> on_fulfilled) {
+            switch (state)
+            {
+                case State::Pending:
+                    return promise_t([this, on_fulfilled](promise_t npm) {
+                        add_on_fulfilled(gen_on_fulfilled(on_fulfilled, npm));
+                        add_on_rejected([this, npm]() {npm.reject(reason);});
+                    });
+                case State::Fulfilled:
+                    return promise_t([this, on_fulfilled](promise_t npm) {
+                        gen_on_fulfilled(on_fulfilled, npm)();
+                    });
+                case State::Rejected:
+                    return promise_t([](promise_t npm) {});
+                default: PROMISE_ERR_INVALID_STATE;
+            }
+        }
+ 
+        template<typename OnRejected>
+        promise_t fail(function<OnRejected(pm_any_t)> on_rejected) {
+            switch (state)
+            {
+                case State::Pending:
+                    return promise_t([this, on_rejected](promise_t npm) {
+                        add_on_rejected(gen_on_rejected(on_rejected, npm));
+                        add_on_fulfilled([this, npm]() {npm.resolve(result);});
+                    });
+                case State::Fulfilled:
+                    return promise_t([](promise_t npm) {});
+                case State::Rejected:
+                    return promise_t([this, on_rejected](promise_t npm) {
+                        add_on_rejected(gen_on_rejected(on_rejected, npm));
+                    });
+                default: PROMISE_ERR_INVALID_STATE;
+            }
+        }
+ 
+        void resolve(pm_any_t _result) {
+            switch (state)
+            {
+                case State::Pending:
+                    result = _result;
+                    state = State::Fulfilled;
+                    fulfilled_callback();
+                    break;
+                default:
+                    break;
+            }
+        }
+
+        void reject(pm_any_t _reason) {
+            switch (state)
+            {
+                case State::Pending:
+                    reason = _reason;
+                    state = State::Rejected;
+                    rejected_callback();
+                    break;
+                default:
+                    break;
+            }
+        }
+    };
+        
+    template<typename PList> promise_t all(PList promise_list) {
+        auto size = std::make_shared<size_t>(promise_list.size());
+        auto results = std::make_shared<values_t>();
+        if (!size) PROMISE_ERR_MISMATCH_TYPE;
+        results->resize(*size);
+        return promise_t([=] (promise_t npm) {
+            size_t idx = 0;
+            for (const auto &pm: promise_list) {
+                pm.then(function<pm_any_t(pm_any_t)>(
+                    [results, size, idx, npm](pm_any_t result) {
+                        (*results)[idx] = result;
+                        if (!--(*size))
+                            npm.resolve(*results);
+                        return none;
+                    }), function<pm_any_t(pm_any_t)>(
+                    [npm, size](pm_any_t reason) {
+                        npm.reject(reason);
+                        return none;
+                    }));
+                idx++;
+            }
+        });
+    }
+
+    template<typename T>
+    inline void promise_t::resolve(T result) const { ptr->resolve(result); }
+
+    template<typename T>
+    inline void promise_t::reject(T reason) const { ptr->reject(reason); }
+
+    template<typename F_, typename F, typename R_, typename R>
+    inline promise_t promise_t::then(function<F_(pm_any_t)> fulfilled_callback,
+                                function<R_(pm_any_t)> rejected_callback) const {
+        return ptr->then(fulfilled_callback, rejected_callback);
+    }
+
+    template<typename F_, typename F>
+    inline promise_t promise_t::then(function<F_(pm_any_t)> fulfilled_callback) const {
+        return ptr->then(fulfilled_callback);
+    }
+
+    template<typename R_, typename R>
+    inline promise_t promise_t::fail(function<R_(pm_any_t)> rejected_callback) const {
+        return ptr->fail(rejected_callback);
+    }
+
+    template<typename T>
+    struct callback_type_conversion {
+        using type = pm_any_t;
+    };
+
+    template<>
+    struct callback_type_conversion<promise_t> {
+        using type = promise_t;
+    };
+
+    template<typename F_, typename F>
+    inline promise_t promise_t::then(function<F_(F)> on_fulfilled) const {
+        using ret_type = typename callback_type_conversion<F_>::type;
+        return ptr->then(function<ret_type(pm_any_t)>(
+            [on_fulfilled](pm_any_t _result) {
+                try {
+                    return ret_type(on_fulfilled(std::any_cast<F>(_result)));
+                } catch (std::bad_any_cast e) { PROMISE_ERR_MISMATCH_TYPE; }
+            }));
+    }
+
+    template<typename F_, typename F, typename R_, typename R>
+    inline promise_t promise_t::then(function<F_(F)> on_fulfilled,
+                                    function<R_(R)> on_rejected) const {
+        using fulfill_ret_type = typename callback_type_conversion<F_>::type;
+        using reject_ret_type = typename callback_type_conversion<R_>::type;
+        return ptr->then(function<fulfill_ret_type(pm_any_t)>(
+            [on_fulfilled](pm_any_t _result) {
+                try {
+                    return fulfill_ret_type(on_fulfilled(std::any_cast<F>(_result)));
+                } catch (std::bad_any_cast e) { PROMISE_ERR_MISMATCH_TYPE; }
+            }), function<fulfill_ret_type(pm_any_t)>(
+            [on_rejected](pm_any_t _reason) {
+                try {
+                    return reject_ret_type(on_rejected(std::any_cast<R>(_reason)));
+                } catch (std::bad_any_cast e) { PROMISE_ERR_MISMATCH_TYPE; }
+            }));
+    }
+
+    template<typename R_, typename R>
+    inline promise_t promise_t::fail(function<R_(R)> on_rejected) const {
+        using ret_type = typename callback_type_conversion<R_>::type;
+        return ptr->fail(function<ret_type(pm_any_t)>(
+            [on_rejected](pm_any_t _reason) {
+                try {
+                    return ret_type(on_rejected(std::any_cast<R>(_reason)));
+                } catch (std::bad_any_cast e) { PROMISE_ERR_MISMATCH_TYPE; }
+            }));
+    }
+}
+#endif
diff --git a/test.cpp b/test.cpp
new file mode 100644
index 0000000..327f5a6
--- /dev/null
+++ b/test.cpp
@@ -0,0 +1,79 @@
+#include <string>
+#include "promise.hpp"
+using promise::promise_t;
+
+int main() {
+    std::function<void()> t1;
+    std::function<void()> t2;
+    std::function<void()> t3;
+    std::function<void()> t4;
+    std::function<void()> t5;
+    auto pm = promise_t([&t1](promise_t pm) {
+        puts("pm1");
+        //t1 = [pm]() {pm.reject(5);};
+        t1 = [pm]() {pm.resolve(5);};
+    }).then(std::function<int(int)>([](int x) {
+        printf("%d\n", x);
+        return 6;
+    })).then(std::function<int(int)>([](int y) {
+        printf("%d\n", y);
+        return 0;
+    })).then(std::function<promise_t(int)>([&t2](int x) {
+        auto pm2 = promise_t([x, &t2](promise_t pm2) {
+            printf("pm2 %d\n", x);
+            t2 = [pm2]() {pm2.resolve(std::string("hello"));};
+        });
+        return pm2;
+    })).then(std::function<int(std::string)>([](std::string s) {
+        printf("%s\n", s.c_str());
+        return 10;
+    })).then(std::function<promise::None(int)>([](int x) {
+        printf("%d\n", x);
+        return promise::none;
+    }));
+    auto p1 = promise_t([&t4](promise_t pm) {
+        puts("p1");
+        t4 = [pm]() {pm.resolve(1);};
+    });
+
+    auto p2 = promise_t([&t5](promise_t pm) {
+        puts("p2");
+        t5 = [pm]() {pm.resolve(std::string("hello"));};
+    });
+
+    auto p3 = promise_t([&t3](promise_t pm) {
+        puts("p3");
+        t3 = [pm]() {pm.resolve(std::string("world"));};
+    });
+
+    auto p4 = promise::all(std::vector<promise_t>{p1, p2, p3})
+        .then(std::function<int(promise::values_t)>(
+            [](const promise::values_t values) {
+            printf("%d %s %s\n", std::any_cast<int>(values[0]),
+                                std::any_cast<std::string>(values[1]).c_str(),
+                                std::any_cast<std::string>(values[2]).c_str());
+        return 100;
+    }));
+
+    auto p5 = promise::all(std::vector<promise_t>{pm, p4})
+        .fail(std::function<int(int)>(
+            [](int reason) {
+                printf("reason: %d\n", reason);
+                return reason;
+        }))
+        .then(std::function<promise::None(promise::values_t)>(
+            [](const promise::values_t values) {
+                printf("finally %d\n", std::any_cast<int>(values[1]));
+                return promise::none;
+        }));
+    puts("calling t");
+    t4();
+    puts("calling t2");
+    t5();
+    puts("calling t3");
+    t3();
+
+    t1();
+    printf("=== after ===\n");
+    t2();
+}
-- 
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