// 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 <lib/fit/promise.h>
#include <unittest/unittest.h>

#include "unittest_utils.h"

namespace {

class fake_context : public fit::context {
public:
    fit::executor* executor() const override {
        ASSERT_CRITICAL(false);
    }
    fit::suspended_task suspend_task() override {
        ASSERT_CRITICAL(false);
    }
};

bool empty_future() {
    BEGIN_TEST;

    fake_context context;

    {
        fit::future<> nihil;
        EXPECT_EQ(fit::future_state::empty, nihil.state());
        EXPECT_FALSE(nihil);
        EXPECT_TRUE(nihil.is_empty());
        EXPECT_FALSE(nihil.is_pending());
        EXPECT_FALSE(nihil.is_ok());
        EXPECT_FALSE(nihil.is_error());
        EXPECT_FALSE(nihil.is_ready());
        EXPECT_FALSE(nihil(context));

        EXPECT_TRUE(nihil == nullptr);
        EXPECT_TRUE(nullptr == nihil);
        EXPECT_FALSE(nihil != nullptr);
        EXPECT_FALSE(nullptr != nihil);
    }

    {
        fit::future<> nihil(nullptr);
        EXPECT_EQ(fit::future_state::empty, nihil.state());
        EXPECT_FALSE(nihil);
        EXPECT_TRUE(nihil.is_empty());
        EXPECT_FALSE(nihil.is_pending());
        EXPECT_FALSE(nihil.is_ok());
        EXPECT_FALSE(nihil.is_error());
        EXPECT_FALSE(nihil.is_ready());
        EXPECT_FALSE(nihil(context));
    }

    {
        fit::future<> nihil(fit::promise<>(nullptr));
        EXPECT_EQ(fit::future_state::empty, nihil.state());
        EXPECT_FALSE(nihil);
        EXPECT_TRUE(nihil.is_empty());
        EXPECT_FALSE(nihil.is_pending());
        EXPECT_FALSE(nihil.is_ok());
        EXPECT_FALSE(nihil.is_error());
        EXPECT_FALSE(nihil.is_ready());
        EXPECT_FALSE(nihil(context));
    }

    {
        fit::future<> nihil(fit::pending());
        EXPECT_EQ(fit::future_state::empty, nihil.state());
        EXPECT_FALSE(nihil);
        EXPECT_TRUE(nihil.is_empty());
        EXPECT_FALSE(nihil.is_pending());
        EXPECT_FALSE(nihil.is_ok());
        EXPECT_FALSE(nihil.is_error());
        EXPECT_FALSE(nihil.is_ready());
        EXPECT_FALSE(nihil(context));
    }

    END_TEST;
}

bool pending_future() {
    BEGIN_TEST;

    fake_context context;

    uint64_t run_count = 0;
    fit::future<int, int> fut(fit::make_promise([&](fit::context& context)
                                                    -> fit::result<int, int> {
        if (++run_count == 3)
            return fit::ok(42);
        return fit::pending();
    }));
    EXPECT_EQ(fit::future_state::pending, fut.state());
    EXPECT_TRUE(fut);
    EXPECT_FALSE(fut.is_empty());
    EXPECT_TRUE(fut.is_pending());
    EXPECT_FALSE(fut.is_ok());
    EXPECT_FALSE(fut.is_error());
    EXPECT_FALSE(fut.is_ready());

    EXPECT_FALSE(fut == nullptr);
    EXPECT_FALSE(nullptr == fut);
    EXPECT_TRUE(fut != nullptr);
    EXPECT_TRUE(nullptr != fut);

    // evaluate the future
    EXPECT_FALSE(fut(context));
    EXPECT_EQ(1, run_count);
    EXPECT_FALSE(fut(context));
    EXPECT_EQ(2, run_count);
    EXPECT_TRUE(fut(context));
    EXPECT_EQ(3, run_count);

    // check the result
    EXPECT_EQ(fit::future_state::ok, fut.state());
    EXPECT_EQ(fit::result_state::ok, fut.result().state());
    EXPECT_EQ(42, fut.result().value());

    // do something similar but this time produce an error to ensure
    // that this state change works as expected too
    fut = fit::make_promise([&](fit::context& context)
                                -> fit::result<int, int> {
        if (++run_count == 5)
            return fit::error(42);
        return fit::pending();
    });
    EXPECT_EQ(fit::future_state::pending, fut.state());
    EXPECT_FALSE(fut(context));
    EXPECT_EQ(4, run_count);
    EXPECT_TRUE(fut(context));
    EXPECT_EQ(5, run_count);
    EXPECT_EQ(fit::future_state::error, fut.state());
    EXPECT_EQ(fit::result_state::error, fut.result().state());
    EXPECT_EQ(42, fut.result().error());

    END_TEST;
}

bool ok_future() {
    BEGIN_TEST;

    fake_context context;
    fit::future<int> fut(fit::ok(42));
    EXPECT_EQ(fit::future_state::ok, fut.state());
    EXPECT_TRUE(fut);
    EXPECT_FALSE(fut.is_empty());
    EXPECT_FALSE(fut.is_pending());
    EXPECT_TRUE(fut.is_ok());
    EXPECT_FALSE(fut.is_error());
    EXPECT_TRUE(fut.is_ready());
    EXPECT_TRUE(fut(context));

    EXPECT_FALSE(fut == nullptr);
    EXPECT_FALSE(nullptr == fut);
    EXPECT_TRUE(fut != nullptr);
    EXPECT_TRUE(nullptr != fut);

    // non-destructive access
    EXPECT_EQ(fit::result_state::ok, fut.result().state());
    EXPECT_EQ(42, fut.result().value());
    EXPECT_EQ(42, fut.value());

    // destructive access
    fut = fit::ok(43);
    EXPECT_EQ(fit::future_state::ok, fut.state());
    EXPECT_EQ(43, fut.take_result().value());
    EXPECT_EQ(fit::future_state::empty, fut.state());

    fut = fit::ok(44);
    EXPECT_EQ(fit::future_state::ok, fut.state());
    EXPECT_EQ(44, fut.take_value());
    EXPECT_EQ(fit::future_state::empty, fut.state());

    fut = fit::ok(45);
    EXPECT_EQ(fit::future_state::ok, fut.state());
    EXPECT_EQ(45, fut.take_ok_result().value);
    EXPECT_EQ(fit::future_state::empty, fut.state());

    END_TEST;
}

bool error_future() {
    BEGIN_TEST;

    fake_context context;
    fit::future<void, int> fut(fit::error(42));
    EXPECT_EQ(fit::future_state::error, fut.state());
    EXPECT_TRUE(fut);
    EXPECT_FALSE(fut.is_empty());
    EXPECT_FALSE(fut.is_pending());
    EXPECT_FALSE(fut.is_ok());
    EXPECT_TRUE(fut.is_error());
    EXPECT_TRUE(fut.is_ready());
    EXPECT_TRUE(fut(context));

    EXPECT_FALSE(fut == nullptr);
    EXPECT_FALSE(nullptr == fut);
    EXPECT_TRUE(fut != nullptr);
    EXPECT_TRUE(nullptr != fut);

    // non-destructive access
    EXPECT_EQ(fit::result_state::error, fut.result().state());
    EXPECT_EQ(42, fut.result().error());
    EXPECT_EQ(42, fut.error());

    // destructive access
    fut = fit::error(43);
    EXPECT_EQ(fit::future_state::error, fut.state());
    EXPECT_EQ(43, fut.take_result().error());
    EXPECT_EQ(fit::future_state::empty, fut.state());

    fut = fit::error(44);
    EXPECT_EQ(fit::future_state::error, fut.state());
    EXPECT_EQ(44, fut.take_error());
    EXPECT_EQ(fit::future_state::empty, fut.state());

    fut = fit::error(45);
    EXPECT_EQ(fit::future_state::error, fut.state());
    EXPECT_EQ(45, fut.take_error_result().error);
    EXPECT_EQ(fit::future_state::empty, fut.state());

    END_TEST;
}

bool assignment_and_swap() {
    BEGIN_TEST;

    fit::future<> x;
    EXPECT_EQ(fit::future_state::empty, x.state());

    x = fit::ok();
    EXPECT_EQ(fit::future_state::ok, x.state());

    x = fit::error();
    EXPECT_EQ(fit::future_state::error, x.state());

    x = fit::pending();
    EXPECT_EQ(fit::future_state::empty, x.state());

    x = nullptr;
    EXPECT_EQ(fit::future_state::empty, x.state());

    x = fit::promise<>();
    EXPECT_EQ(fit::future_state::empty, x.state());

    x = fit::make_promise([] {});
    EXPECT_EQ(fit::future_state::pending, x.state());

    fit::future<> y(std::move(x));
    EXPECT_EQ(fit::future_state::pending, y.state());
    EXPECT_EQ(fit::future_state::empty, x.state());

    x.swap(y);
    EXPECT_EQ(fit::future_state::pending, x.state());
    EXPECT_EQ(fit::future_state::empty, y.state());

    x.swap(x);
    EXPECT_EQ(fit::future_state::pending, x.state());

    END_TEST;
}

bool make_future() {
    BEGIN_TEST;

    fake_context context;
    uint64_t run_count = 0;
    auto fut = fit::make_future(fit::make_promise([&] {
        run_count++;
        return fit::ok(42);
    }));
    EXPECT_TRUE(fut(context));
    EXPECT_EQ(42, fut.value());

    END_TEST;
}

// Ensure that fit::future is considered nullable so that there is
// consistency with the fact that it can be initialized and assigned from
// nullptr similar to fit::function.
static_assert(fit::is_nullable<fit::future<>>::value, "");

} // namespace

BEGIN_TEST_CASE(future_tests)
RUN_TEST(empty_future)
RUN_TEST(pending_future)
RUN_TEST(ok_future)
RUN_TEST(error_future)
RUN_TEST(assignment_and_swap)
RUN_TEST(make_future)
END_TEST_CASE(future_tests)