// 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 <map>

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

#include "unittest_utils.h"

namespace {

enum class disposition {
    pending,
    resumed,
    released
};

class fake_resolver : public fit::suspended_task::resolver {
public:
    uint64_t num_tickets_issued() const { return next_ticket_ - 1; }

    fit::suspended_task::ticket obtain_ticket() {
        fit::suspended_task::ticket ticket = next_ticket_++;
        tickets_.emplace(ticket, disposition::pending);
        return ticket;
    }

    disposition get_disposition(fit::suspended_task::ticket ticket) {
        auto it = tickets_.find(ticket);
        ASSERT_CRITICAL(it != tickets_.end());
        return it->second;
    }

    fit::suspended_task::ticket duplicate_ticket(
        fit::suspended_task::ticket ticket) override {
        auto it = tickets_.find(ticket);
        ASSERT_CRITICAL(it != tickets_.end());
        ASSERT_CRITICAL(it->second == disposition::pending);
        return obtain_ticket();
    }

    void resolve_ticket(
        fit::suspended_task::ticket ticket, bool resume_task) override {
        auto it = tickets_.find(ticket);
        ASSERT_CRITICAL(it != tickets_.end());
        ASSERT_CRITICAL(it->second == disposition::pending);
        it->second = resume_task ? disposition::resumed : disposition::released;
    }

private:
    fit::suspended_task::ticket next_ticket_ = 1;
    std::map<fit::suspended_task::ticket, disposition> tickets_;
};

bool test() {
    BEGIN_TEST;

    fake_resolver resolver;
    {
        fit::suspended_task empty1;
        EXPECT_FALSE(empty1);

        fit::suspended_task empty2(nullptr, 42);
        EXPECT_FALSE(empty2);

        fit::suspended_task empty_copy(empty1);
        EXPECT_FALSE(empty_copy);
        EXPECT_FALSE(empty1);

        fit::suspended_task empty_move(std::move(empty2));
        EXPECT_FALSE(empty_move);
        EXPECT_FALSE(empty2);

        fit::suspended_task task(&resolver, resolver.obtain_ticket());
        EXPECT_TRUE(task);
        EXPECT_EQ(1, resolver.num_tickets_issued());
        EXPECT_EQ(disposition::pending, resolver.get_disposition(1));

        fit::suspended_task task_copy(task);
        EXPECT_TRUE(task_copy);
        EXPECT_TRUE(task);
        EXPECT_EQ(2, resolver.num_tickets_issued());
        EXPECT_EQ(disposition::pending, resolver.get_disposition(1));
        EXPECT_EQ(disposition::pending, resolver.get_disposition(2));

        fit::suspended_task task_move(std::move(task));
        EXPECT_TRUE(task_move);
        EXPECT_FALSE(task);
        EXPECT_EQ(2, resolver.num_tickets_issued());
        EXPECT_EQ(disposition::pending, resolver.get_disposition(1));
        EXPECT_EQ(disposition::pending, resolver.get_disposition(2));

        fit::suspended_task x;
        x = empty1;
        EXPECT_FALSE(x);

        x = task_copy;
        EXPECT_TRUE(x);
        EXPECT_TRUE(task_copy);
        EXPECT_EQ(3, resolver.num_tickets_issued());
        EXPECT_EQ(disposition::pending, resolver.get_disposition(1));
        EXPECT_EQ(disposition::pending, resolver.get_disposition(2));
        EXPECT_EQ(disposition::pending, resolver.get_disposition(3));

        x = std::move(empty_move); // x's ticket is released here
        EXPECT_FALSE(x);
        EXPECT_FALSE(empty_move);
        EXPECT_EQ(3, resolver.num_tickets_issued());
        EXPECT_EQ(disposition::pending, resolver.get_disposition(1));
        EXPECT_EQ(disposition::pending, resolver.get_disposition(2));
        EXPECT_EQ(disposition::released, resolver.get_disposition(3));

        x = task_copy;            // assign x a duplicate ticket
        x = std::move(task_move); // x's ticket is released here
        EXPECT_TRUE(x);
        EXPECT_TRUE(task_copy);
        EXPECT_FALSE(task_move);
        EXPECT_EQ(4, resolver.num_tickets_issued());
        EXPECT_EQ(disposition::pending, resolver.get_disposition(1));
        EXPECT_EQ(disposition::pending, resolver.get_disposition(2));
        EXPECT_EQ(disposition::released, resolver.get_disposition(3));
        EXPECT_EQ(disposition::released, resolver.get_disposition(4));

        x.resume_task(); // x's ticket is resumed here
        EXPECT_FALSE(x);
        EXPECT_EQ(4, resolver.num_tickets_issued());
        EXPECT_EQ(disposition::resumed, resolver.get_disposition(1));
        EXPECT_EQ(disposition::pending, resolver.get_disposition(2));
        EXPECT_EQ(disposition::released, resolver.get_disposition(3));
        EXPECT_EQ(disposition::released, resolver.get_disposition(4));

        x.resume_task(); // already resumed so has no effect
        EXPECT_FALSE(x);

        x.reset(); // already resumed so has no effect
        EXPECT_FALSE(x);

        // note: task_copy still has a ticket here which will be
        // released when the scope exits
    }
    EXPECT_EQ(4, resolver.num_tickets_issued());
    EXPECT_EQ(disposition::resumed, resolver.get_disposition(1));
    EXPECT_EQ(disposition::released, resolver.get_disposition(2));
    EXPECT_EQ(disposition::released, resolver.get_disposition(3));
    EXPECT_EQ(disposition::released, resolver.get_disposition(4));

    END_TEST;
}

bool swapping() {
    BEGIN_TEST;

    fake_resolver resolver;
    {
        fit::suspended_task a(&resolver, resolver.obtain_ticket());
        fit::suspended_task b(&resolver, resolver.obtain_ticket());
        fit::suspended_task c;
        EXPECT_EQ(2, resolver.num_tickets_issued());
        EXPECT_EQ(disposition::pending, resolver.get_disposition(1));
        EXPECT_EQ(disposition::pending, resolver.get_disposition(2));

        a.swap(c);
        EXPECT_FALSE(a);
        EXPECT_TRUE(c);
        EXPECT_EQ(disposition::pending, resolver.get_disposition(1));
        EXPECT_EQ(disposition::pending, resolver.get_disposition(2));

        a.swap(a);
        EXPECT_FALSE(a);
        EXPECT_EQ(disposition::pending, resolver.get_disposition(1));
        EXPECT_EQ(disposition::pending, resolver.get_disposition(2));

        swap(c, b);
        EXPECT_TRUE(c);
        EXPECT_TRUE(b);
        EXPECT_EQ(disposition::pending, resolver.get_disposition(1));
        EXPECT_EQ(disposition::pending, resolver.get_disposition(2));

        swap(c, c);
        EXPECT_TRUE(c);
        EXPECT_EQ(disposition::pending, resolver.get_disposition(1));
        EXPECT_EQ(disposition::pending, resolver.get_disposition(2));

        c.resume_task();
        EXPECT_FALSE(c);
        EXPECT_EQ(disposition::pending, resolver.get_disposition(1));
        EXPECT_EQ(disposition::resumed, resolver.get_disposition(2));

        b.reset();
        EXPECT_FALSE(b);
        EXPECT_EQ(disposition::released, resolver.get_disposition(1));
        EXPECT_EQ(disposition::resumed, resolver.get_disposition(2));
    }

    END_TEST;
}

} // namespace

BEGIN_TEST_CASE(suspended_task_tests)
RUN_TEST(test)
RUN_TEST(swapping)
END_TEST_CASE(suspended_task_tests)