// 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.

#pragma once

#include <cobalt-client/cpp/histogram.h>
#include <lib/fzl/time.h>
#include <lib/zx/time.h>
#include <zircon/assert.h>

namespace cobalt_client {
namespace internal {

template <typename Clock> class TimerBase {
public:
    explicit TimerBase(bool is_collecting) : start_(is_collecting ? Clock::now().get() : 0) {}
    TimerBase(const TimerBase&) = delete;
    TimerBase(TimerBase&& other) : start_(other.start_) { other.start_ = zx::ticks(0); }
    TimerBase& operator=(const TimerBase&) = delete;
    TimerBase& operator=(TimerBase&& other) = delete;
    ~TimerBase() = default;

    // Returns the duration since creation. If |is_collecting| is false, will return
    // 0.
    zx::duration End() {
        if (start_.get() == 0) {
            return zx::duration(0);
        }
        return fzl::TicksToNs(Clock::now() - start_);
    }

    // Resets the timer. If |is_collecting| is false, has no effect.
    void Reset() {
        if (start_.get() == 0) {
            return;
        }
        start_ = Clock::now();
    }

private:
    zx::ticks start_;
};
} // namespace internal

// Utility class for measuring the amount of ticks in an interval.
//
// This class is moveable, but not copyable or assignable.
using Timer = internal::TimerBase<zx::ticks>;

} // namespace cobalt_client