// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <functional>
#include <memory>

#include <lib/fit/defer.h>
#include <lib/fit/function.h>
#include <lib/fit/nullable.h>
#include <unittest/unittest.h>

#include "unittest_utils.h"

namespace {

// Counts instances.
class balance {
public:
    balance(int* counter)
        : counter_(counter) {
        *counter_ += 1;
    }

    balance(balance&& other)
        : counter_(other.counter_) {
        *counter_ += 1;
    }

    ~balance() {
        *counter_ -= 1;
    }

    balance(const balance& other) = delete;
    balance& operator=(const balance& other) = delete;
    balance& operator=(balance&& other) = delete;

private:
    int* const counter_;
};

void incr_arg(int* p) {
    *p += 1;
}

template <typename T>
bool default_construction() {
    BEGIN_TEST;

    fit::deferred_action<T> d;
    EXPECT_FALSE(d);

    END_TEST;
}

template <typename T>
bool null_construction() {
    BEGIN_TEST;

    fit::deferred_action<T> d(nullptr);
    EXPECT_FALSE(d);

    END_TEST;
}

template <typename T>
bool basic() {
    static_assert(fit::is_nullable<fit::deferred_action<T>>::value, "");

    BEGIN_TEST;

    int var = 0;
    {
        auto do_incr = fit::defer<T>([&var]() { incr_arg(&var); });
        EXPECT_TRUE(do_incr);
        EXPECT_EQ(var, 0);
        EXPECT_FALSE(do_incr == nullptr);
        EXPECT_FALSE(nullptr == do_incr);
        EXPECT_TRUE(do_incr != nullptr);
        EXPECT_TRUE(nullptr != do_incr);
    }
    EXPECT_EQ(var, 1);

    END_TEST;
}

template <typename T>
bool cancel() {
    BEGIN_TEST;

    int var = 0;
    {
        auto do_incr = fit::defer<T>([&var]() { incr_arg(&var); });
        EXPECT_TRUE(do_incr);
        EXPECT_EQ(var, 0);

        do_incr.cancel();
        EXPECT_FALSE(do_incr);
        EXPECT_EQ(var, 0);
        EXPECT_TRUE(do_incr == nullptr);
        EXPECT_TRUE(nullptr == do_incr);
        EXPECT_FALSE(do_incr != nullptr);
        EXPECT_FALSE(nullptr != do_incr);

        // Once cancelled, call has no effect.
        do_incr.call();
        EXPECT_FALSE(do_incr);
        EXPECT_EQ(var, 0);
    }
    EXPECT_EQ(var, 0);

    END_TEST;
}

template <typename T>
bool null_assignment() {
    BEGIN_TEST;

    int var = 0;
    {
        auto do_incr = fit::defer<T>([&var]() { incr_arg(&var); });
        EXPECT_TRUE(do_incr);
        EXPECT_EQ(var, 0);

        do_incr = nullptr;
        EXPECT_FALSE(do_incr);
        EXPECT_EQ(var, 0);

        // Once cancelled, call has no effect.
        do_incr.call();
        EXPECT_FALSE(do_incr);
        EXPECT_EQ(var, 0);
    }
    EXPECT_EQ(var, 0);

    END_TEST;
}

template <typename T>
bool target_reassignment() {
    BEGIN_TEST;

    int var = 0;
    {
        fit::deferred_action<T> do_incr;
        do_incr = []() { ASSERT_CRITICAL(false); };
        EXPECT_TRUE(do_incr);
        EXPECT_EQ(var, 0);

        do_incr = [&var]() { incr_arg(&var); };
        EXPECT_TRUE(do_incr);
        EXPECT_EQ(var, 0);
    }
    EXPECT_EQ(var, 1);

    END_TEST;
}

template <typename T>
bool call() {
    BEGIN_TEST;

    int var = 0;
    {
        auto do_incr = fit::defer<T>([&var]() { incr_arg(&var); });
        EXPECT_TRUE(do_incr);
        EXPECT_EQ(var, 0);

        do_incr.call();
        EXPECT_FALSE(do_incr);
        EXPECT_EQ(var, 1);

        // Call is effective only once.
        do_incr.call();
        EXPECT_FALSE(do_incr);
        EXPECT_EQ(var, 1);
    }
    EXPECT_EQ(var, 1);

    END_TEST;
}

template <typename T>
bool recursive_call() {
    BEGIN_TEST;

    int var = 0;
    {
        auto do_incr = fit::defer<T>([]() { /* no-op */ });
        EXPECT_TRUE(do_incr);
        do_incr = fit::defer<T>([&do_incr, &var]() {
            incr_arg(&var);
            do_incr.call();
            EXPECT_FALSE(do_incr);
        });
        EXPECT_TRUE(do_incr);
        EXPECT_EQ(var, 0);

        do_incr.call();
        EXPECT_FALSE(do_incr);
        EXPECT_EQ(var, 1);
    }
    EXPECT_EQ(var, 1);

    END_TEST;
}

template <typename T>
bool move_construct_basic() {
    BEGIN_TEST;

    int var = 0;
    {
        auto do_incr = fit::defer<T>([&var]() { incr_arg(&var); });
        EXPECT_TRUE(do_incr);

        auto do_incr2(std::move(do_incr));
        EXPECT_FALSE(do_incr);
        EXPECT_TRUE(do_incr2);
        EXPECT_EQ(var, 0);
    }
    EXPECT_EQ(var, 1);

    END_TEST;
}

template <typename T>
bool move_construct_from_canceled() {
    BEGIN_TEST;

    int var = 0;
    {
        auto do_incr = fit::defer<T>([&var]() { incr_arg(&var); });
        EXPECT_TRUE(do_incr);

        do_incr.cancel();
        EXPECT_FALSE(do_incr);

        auto do_incr2(std::move(do_incr));
        EXPECT_FALSE(do_incr);
        EXPECT_FALSE(do_incr2);
        EXPECT_EQ(var, 0);
    }
    EXPECT_EQ(var, 0);

    END_TEST;
}

template <typename T>
bool move_construct_from_called() {
    BEGIN_TEST;

    int var = 0;
    {
        auto do_incr = fit::defer<T>([&var]() { incr_arg(&var); });
        EXPECT_TRUE(do_incr);
        EXPECT_EQ(var, 0);

        do_incr.call();
        EXPECT_FALSE(do_incr);
        EXPECT_EQ(var, 1);

        // Must not be called again, since do_incr has triggered already.
        auto do_incr2(std::move(do_incr));
        EXPECT_FALSE(do_incr);
    }
    EXPECT_EQ(var, 1);

    END_TEST;
}

template <typename T>
bool move_assign_basic() {
    BEGIN_TEST;

    int var1 = 0, var2 = 0;
    {
        auto do_incr = fit::defer<T>([&var1]() { incr_arg(&var1); });
        auto do_incr2 = fit::defer<T>([&var2]() { incr_arg(&var2); });
        EXPECT_TRUE(do_incr);
        EXPECT_TRUE(do_incr2);
        EXPECT_EQ(var1, 0);
        EXPECT_EQ(var2, 0);

        // do_incr2 is moved-to, so its associated function is called.
        do_incr2 = std::move(do_incr);
        EXPECT_FALSE(do_incr);
        EXPECT_TRUE(do_incr2);
        EXPECT_EQ(var1, 0);
        EXPECT_EQ(var2, 1);

        // self-assignment does nothing
        do_incr = std::move(do_incr);
        do_incr2 = std::move(do_incr2);
        EXPECT_TRUE(do_incr2);
        EXPECT_EQ(var1, 0);
        EXPECT_EQ(var2, 1);
    }
    EXPECT_EQ(var1, 1);
    EXPECT_EQ(var2, 1);

    END_TEST;
}

template <typename T>
bool move_assign_wider_scoped() {
    BEGIN_TEST;

    int var1 = 0, var2 = 0;
    {
        auto do_incr = fit::defer<T>([&var1]() { incr_arg(&var1); });
        EXPECT_TRUE(do_incr);
        EXPECT_EQ(var1, 0);
        EXPECT_EQ(var2, 0);
        {
            auto do_incr2 = fit::defer<T>([&var2]() { incr_arg(&var2); });
            EXPECT_TRUE(do_incr);
            EXPECT_TRUE(do_incr2);
            EXPECT_EQ(var1, 0);
            EXPECT_EQ(var2, 0);

            // do_incr is moved-to, so its associated function is called.
            do_incr = std::move(do_incr2);
            EXPECT_TRUE(do_incr);
            EXPECT_FALSE(do_incr2);
            EXPECT_EQ(var1, 1);
            EXPECT_EQ(var2, 0);
        }
        // do_incr2 is out of scope but has been moved so its function is not
        // called.
        EXPECT_TRUE(do_incr);
        EXPECT_EQ(var1, 1);
        EXPECT_EQ(var2, 0);
    }
    EXPECT_EQ(var1, 1);
    EXPECT_EQ(var2, 1);

    END_TEST;
}

template <typename T>
bool move_assign_from_canceled() {
    BEGIN_TEST;

    int var1 = 0, var2 = 0;
    {
        auto do_incr = fit::defer<T>([&var1]() { incr_arg(&var1); });
        auto do_incr2 = fit::defer<T>([&var2]() { incr_arg(&var2); });
        EXPECT_TRUE(do_incr);
        EXPECT_TRUE(do_incr2);
        EXPECT_EQ(var1, 0);
        EXPECT_EQ(var2, 0);

        do_incr.cancel();
        EXPECT_FALSE(do_incr);
        EXPECT_TRUE(do_incr2);
        EXPECT_EQ(var1, 0);
        EXPECT_EQ(var2, 0);

        // do_incr2 is moved-to, so its associated function is called.
        do_incr2 = std::move(do_incr);
        EXPECT_FALSE(do_incr);
        EXPECT_FALSE(do_incr2);
        EXPECT_EQ(var1, 0);
        EXPECT_EQ(var2, 1);
    }
    // do_incr was cancelled, this state is preserved by the move.
    EXPECT_EQ(var1, 0);
    EXPECT_EQ(var2, 1);

    END_TEST;
}

template <typename T>
bool move_assign_from_called() {
    BEGIN_TEST;

    int var1 = 0, var2 = 0;
    {
        auto do_incr = fit::defer<T>([&var1]() { incr_arg(&var1); });
        auto do_incr2 = fit::defer<T>([&var2]() { incr_arg(&var2); });
        EXPECT_TRUE(do_incr);
        EXPECT_TRUE(do_incr2);
        EXPECT_EQ(var1, 0);
        EXPECT_EQ(var2, 0);

        do_incr.call();
        EXPECT_FALSE(do_incr);
        EXPECT_TRUE(do_incr2);
        EXPECT_EQ(var1, 1);
        EXPECT_EQ(var2, 0);

        // do_incr2 is moved-to, so its associated function is called.
        do_incr2 = std::move(do_incr);
        EXPECT_FALSE(do_incr);
        EXPECT_FALSE(do_incr2);
        EXPECT_EQ(var1, 1);
        EXPECT_EQ(var2, 1);
    }
    // do_incr was called already, this state is preserved by the move.
    EXPECT_EQ(var1, 1);
    EXPECT_EQ(var2, 1);

    END_TEST;
}

template <typename T>
bool move_assign_to_null() {
    BEGIN_TEST;

    int call_count = 0;
    {
        fit::deferred_action<T> deferred(nullptr);
        EXPECT_FALSE(deferred);
        deferred = fit::defer<T>([&call_count] { call_count++; });
        EXPECT_EQ(0, call_count);
    }
    EXPECT_EQ(1, call_count);

    END_TEST;
}

template <typename T>
bool move_assign_to_invalid() {
    BEGIN_TEST;

    int call_count = 0;
    {
        T fn;
        fit::deferred_action<T> deferred(std::move(fn));
        EXPECT_FALSE(deferred);
        deferred = fit::defer<T>([&call_count] { call_count++; });
        EXPECT_EQ(0, call_count);
    }
    EXPECT_EQ(1, call_count);

    END_TEST;
}

template <typename T>
bool target_destroyed_when_scope_exited() {
    BEGIN_TEST;

    int call_count = 0;
    int instance_count = 0;
    {
        auto action = fit::defer<T>(
            [&call_count, balance = balance(&instance_count)] {
                incr_arg(&call_count);
            });
        EXPECT_EQ(0, call_count);
        EXPECT_EQ(1, instance_count);
    }
    EXPECT_EQ(1, call_count);
    EXPECT_EQ(0, instance_count);

    END_TEST;
}

template <typename T>
bool target_destroyed_when_called() {
    BEGIN_TEST;

    int call_count = 0;
    int instance_count = 0;
    {
        auto action = fit::defer<T>(
            [&call_count, balance = balance(&instance_count)] {
                incr_arg(&call_count);
            });
        EXPECT_EQ(0, call_count);
        EXPECT_EQ(1, instance_count);

        action.call();
        EXPECT_EQ(1, call_count);
        EXPECT_EQ(0, instance_count);
    }
    EXPECT_EQ(1, call_count);
    EXPECT_EQ(0, instance_count);

    END_TEST;
}

template <typename T>
bool target_destroyed_when_canceled() {
    BEGIN_TEST;

    int call_count = 0;
    int instance_count = 0;
    {
        auto action = fit::defer<T>(
            [&call_count, balance = balance(&instance_count)] {
                incr_arg(&call_count);
            });
        EXPECT_EQ(0, call_count);
        EXPECT_EQ(1, instance_count);

        action.cancel();
        EXPECT_EQ(0, call_count);
        EXPECT_EQ(0, instance_count);
    }
    EXPECT_EQ(0, call_count);
    EXPECT_EQ(0, instance_count);

    END_TEST;
}

template <typename T>
bool target_destroyed_when_move_constructed() {
    BEGIN_TEST;

    int call_count = 0;
    int instance_count = 0;
    {
        auto action = fit::defer<T>(
            [&call_count, balance = balance(&instance_count)] {
                incr_arg(&call_count);
            });
        EXPECT_EQ(0, call_count);
        EXPECT_EQ(1, instance_count);

        auto action2(std::move(action));
        EXPECT_EQ(0, call_count);
        EXPECT_EQ(1, instance_count);
    }
    EXPECT_EQ(1, call_count);
    EXPECT_EQ(0, instance_count);

    END_TEST;
}

template <typename T>
bool target_destroyed_when_move_assigned() {
    BEGIN_TEST;

    int call_count = 0;
    int instance_count = 0;
    {
        auto action = fit::defer<T>(
            [&call_count, balance = balance(&instance_count)] {
                incr_arg(&call_count);
            });
        EXPECT_EQ(0, call_count);
        EXPECT_EQ(1, instance_count);

        auto action2 = fit::defer<T>([] {});
        action2 = std::move(action);
        EXPECT_EQ(0, call_count);
        EXPECT_EQ(1, instance_count);
    }
    EXPECT_EQ(1, call_count);
    EXPECT_EQ(0, instance_count);

    END_TEST;
}

} // namespace

BEGIN_TEST_CASE(defer_tests)
RUN_TEST(default_construction<fit::closure>)
RUN_TEST(default_construction<std::function<void()>>)
RUN_TEST(null_construction<fit::closure>)
RUN_TEST(null_construction<std::function<void()>>)
RUN_TEST(basic<fit::closure>)
RUN_TEST(basic<std::function<void()>>)
RUN_TEST(cancel<fit::closure>)
RUN_TEST(cancel<std::function<void()>>)
RUN_TEST(null_assignment<fit::closure>)
RUN_TEST(null_assignment<std::function<void()>>)
RUN_TEST(target_reassignment<fit::closure>)
RUN_TEST(target_reassignment<std::function<void()>>)
RUN_TEST(call<fit::closure>)
RUN_TEST(call<std::function<void()>>)
RUN_TEST(recursive_call<fit::closure>)
RUN_TEST(recursive_call<std::function<void()>>)
RUN_TEST(move_construct_basic<fit::closure>)
RUN_TEST(move_construct_basic<std::function<void()>>)
RUN_TEST(move_construct_from_canceled<fit::closure>)
RUN_TEST(move_construct_from_canceled<std::function<void()>>)
RUN_TEST(move_construct_from_called<fit::closure>)
RUN_TEST(move_construct_from_called<std::function<void()>>)
RUN_TEST(move_assign_basic<fit::closure>)
RUN_TEST(move_assign_basic<std::function<void()>>)
RUN_TEST(move_assign_wider_scoped<fit::closure>)
RUN_TEST(move_assign_wider_scoped<std::function<void()>>)
RUN_TEST(move_assign_from_canceled<fit::closure>)
RUN_TEST(move_assign_from_canceled<std::function<void()>>)
RUN_TEST(move_assign_from_called<fit::closure>)
RUN_TEST(move_assign_from_called<std::function<void()>>)
RUN_TEST(move_assign_to_null<fit::closure>)
RUN_TEST(move_assign_to_null<std::function<void()>>)
RUN_TEST(move_assign_to_invalid<fit::closure>)
RUN_TEST(move_assign_to_invalid<std::function<void()>>)
// These tests do not support std::function because std::function copies
// the captured values (which balance does not support).
RUN_TEST(target_destroyed_when_scope_exited<fit::closure>)
RUN_TEST(target_destroyed_when_called<fit::closure>)
RUN_TEST(target_destroyed_when_canceled<fit::closure>)
RUN_TEST(target_destroyed_when_move_constructed<fit::closure>)
RUN_TEST(target_destroyed_when_move_assigned<fit::closure>)
END_TEST_CASE(defer_tests)