/*
 * Copyright 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include <chrono>
#include <deque>
#include <optional>
#include <string>
#include <unordered_map>

#include <ui/Transform.h>
#include <utils/Timers.h>

#include <scheduler/Fps.h>
#include <scheduler/Seamlessness.h>

#include "FrameRateCompatibility.h"
#include "LayerHistory.h"
#include "RefreshRateSelector.h"

namespace android {

class Layer;

namespace scheduler {

using namespace std::chrono_literals;
struct LayerProps;
// Maximum period between presents for a layer to be considered active.
constexpr std::chrono::nanoseconds MAX_ACTIVE_LAYER_PERIOD_NS = 1200ms;

// Earliest present time for a layer to be considered active.
constexpr nsecs_t getActiveLayerThreshold(nsecs_t now) {
    return now - MAX_ACTIVE_LAYER_PERIOD_NS.count();
}

// Stores history of present times and refresh rates for a layer.
class LayerInfo {
    using LayerUpdateType = LayerHistory::LayerUpdateType;

    // Layer is considered frequent if the earliest value in the window of most recent present times
    // is within a threshold. If a layer is infrequent, its average refresh rate is disregarded in
    // favor of a low refresh rate.
    static constexpr size_t kFrequentLayerWindowSize = 4;
    static constexpr Fps kMinFpsForFrequentLayer = 10_Hz;
    static constexpr auto kMaxPeriodForFrequentLayerNs =
            std::chrono::nanoseconds(kMinFpsForFrequentLayer.getPeriodNsecs()) + 1ms;
    static constexpr size_t kNumSmallDirtyThreshold = 2;

    friend class LayerHistoryTest;
    friend class LayerHistoryIntegrationTest;
    friend class LayerInfoTest;

public:
    // Holds information about the layer vote
    struct LayerVote {
        LayerHistory::LayerVoteType type = LayerHistory::LayerVoteType::Heuristic;
        Fps fps;
        Seamlessness seamlessness = Seamlessness::Default;
        FrameRateCategory category = FrameRateCategory::Default;
        bool categorySmoothSwitchOnly = false;

        // Returns true if the layer explicitly should contribute to frame rate scoring.
        bool isNoVote() const { return RefreshRateSelector::isNoVote(type); }
    };

    using RefreshRateVotes = ftl::SmallVector<LayerInfo::LayerVote, 2>;

    enum class FrameRateSelectionStrategy {
        Propagate,
        OverrideChildren,
        Self,

        ftl_last = Self
    };

    // Encapsulates the frame rate specifications of the layer. This information will be used
    // when the display refresh rate is determined.
    struct FrameRate {
        using Seamlessness = scheduler::Seamlessness;

        // Information related to a specific desired frame rate vote.
        struct FrameRateVote {
            Fps rate;
            FrameRateCompatibility type = FrameRateCompatibility::Default;
            Seamlessness seamlessness = Seamlessness::Default;

            bool operator==(const FrameRateVote& other) const {
                return isApproxEqual(rate, other.rate) && type == other.type &&
                        seamlessness == other.seamlessness;
            }

            FrameRateVote() = default;

            FrameRateVote(Fps rate, FrameRateCompatibility type,
                          Seamlessness seamlessness = Seamlessness::OnlySeamless)
                  : rate(rate), type(type), seamlessness(getSeamlessness(rate, seamlessness)) {}
        } vote;

        FrameRateCategory category = FrameRateCategory::Default;
        bool categorySmoothSwitchOnly = false;

        FrameRate() = default;

        FrameRate(Fps rate, FrameRateCompatibility type,
                  Seamlessness seamlessness = Seamlessness::OnlySeamless,
                  FrameRateCategory category = FrameRateCategory::Default)
              : vote(FrameRateVote(rate, type, seamlessness)), category(category) {}

        bool operator==(const FrameRate& other) const {
            return vote == other.vote && category == other.category;
        }

        bool operator!=(const FrameRate& other) const { return !(*this == other); }

        // Convert an ANATIVEWINDOW_FRAME_RATE_COMPATIBILITY_* value to a
        // Layer::FrameRateCompatibility. Logs fatal if the compatibility value is invalid.
        static FrameRateCompatibility convertCompatibility(int8_t compatibility);

        // Convert an ANATIVEWINDOW_CHANGE_FRAME_RATE_* value to a scheduler::Seamlessness.
        // Logs fatal if the strategy value is invalid.
        static scheduler::Seamlessness convertChangeFrameRateStrategy(int8_t strategy);

        // Convert an ANATIVEWINDOW_FRAME_RATE_CATEGORY_* value to a FrameRateCategory.
        // Logs fatal if the category value is invalid.
        static FrameRateCategory convertCategory(int8_t category);

        // True if the FrameRate has explicit frame rate specifications.
        bool isValid() const;

        // Returns true if the FrameRate explicitly instructs to not contribute to frame rate
        // selection.
        bool isNoVote() const;

    private:
        static Seamlessness getSeamlessness(Fps rate, Seamlessness seamlessness) {
            if (!rate.isValid()) {
                // Refresh rate of 0 is a special value which should reset the vote to
                // its default value.
                return Seamlessness::Default;
            }
            return seamlessness;
        }
    };

    // Convert an ANATIVEWINDOW_FRAME_RATE_SELECTION_STRATEGY_* value to FrameRateSelectionStrategy.
    // Logs fatal if the strategy value is invalid.
    static FrameRateSelectionStrategy convertFrameRateSelectionStrategy(int8_t strategy);

    static void setTraceEnabled(bool enabled) { sTraceEnabled = enabled; }

    LayerInfo(const std::string& name, uid_t ownerUid, LayerHistory::LayerVoteType defaultVote);

    LayerInfo(const LayerInfo&) = delete;
    LayerInfo& operator=(const LayerInfo&) = delete;

    // Records the last requested present time. It also stores information about when
    // the layer was last updated. If the present time is farther in the future than the
    // updated time, the updated time is the present time.
    void setLastPresentTime(nsecs_t lastPresentTime, nsecs_t now, LayerUpdateType updateType,
                            bool pendingModeChange, const LayerProps& props);

    // Sets an explicit layer vote. This usually comes directly from the application via
    // ANativeWindow_setFrameRate API. This is also used by Game Default Frame Rate and
    // Game Mode Intervention Frame Rate.
    void setLayerVote(LayerVote vote) { mLayerVote = vote; }

    // Sets the default layer vote. This will be the layer vote after calling to resetLayerVote().
    // This is used for layers that called to setLayerVote() and then removed the vote, so that the
    // layer can go back to whatever vote it had before the app voted for it.
    void setDefaultLayerVote(LayerHistory::LayerVoteType type) { mDefaultVote = type; }

    void setProperties(const LayerProps&);

    // Resets the layer vote to its default.
    void resetLayerVote() {
        mLayerVote = {mDefaultVote, Fps(), Seamlessness::Default, FrameRateCategory::Default};
    }

    std::string getName() const { return mName; }

    uid_t getOwnerUid() const { return mOwnerUid; }

    RefreshRateVotes getRefreshRateVote(const RefreshRateSelector&, nsecs_t now);

    // Return the last updated time. If the present time is farther in the future than the
    // updated time, the updated time is the present time.
    nsecs_t getLastUpdatedTime() const { return mLastUpdatedTime; }

    FrameRate getSetFrameRateVote() const;
    bool isVisible() const;
    int32_t getFrameRateSelectionPriority() const;
    bool isFrontBuffered() const;
    FloatRect getBounds() const;
    ui::Transform getTransform() const;

    // Returns a C string for tracing a vote
    const char* getTraceTag(LayerHistory::LayerVoteType type) const;

    // Return the framerate of this layer.
    Fps getFps(nsecs_t now) const;

    void onLayerInactive(nsecs_t now) {
        // Mark mFrameTimeValidSince to now to ignore all previous frame times.
        // We are not deleting the old frame to keep track of whether we should treat the first
        // buffer as Max as we don't know anything about this layer or Min as this layer is
        // posting infrequent updates.
        const auto timePoint = std::chrono::nanoseconds(now);
        mFrameTimeValidSince = std::chrono::time_point<std::chrono::steady_clock>(timePoint);
        mLastRefreshRate = {};
        mRefreshRateHistory.clear();
        mIsFrequencyConclusive = true;
    }

    void clearHistory(nsecs_t now) {
        onLayerInactive(now);
        mFrameTimes.clear();
    }

private:
    // Used to store the layer timestamps
    struct FrameTimeData {
        nsecs_t presentTime; // desiredPresentTime, if provided
        nsecs_t queueTime;  // buffer queue time
        bool pendingModeChange;
        bool isSmallDirty;
    };

    // Holds information about the calculated and reported refresh rate
    struct RefreshRateHeuristicData {
        // Rate calculated on the layer
        Fps calculated;
        // Last reported rate for LayerInfo::getRefreshRate()
        Fps reported;
        // Whether the last reported rate for LayerInfo::getRefreshRate()
        // was due to animation or infrequent updates
        bool animating = false;
        // Whether the last reported rate for LayerInfo::getRefreshRate()
        // was due to infrequent updates
        bool infrequent = false;
    };

    // Class to store past calculated refresh rate and determine whether
    // the refresh rate calculated is consistent with past values
    class RefreshRateHistory {
    public:
        static constexpr auto HISTORY_SIZE = 90;
        static constexpr std::chrono::nanoseconds HISTORY_DURATION = 2s;

        RefreshRateHistory(const std::string& name) : mName(name) {}

        // Clears History
        void clear();

        // Adds a new refresh rate and returns valid refresh rate if it is consistent enough
        Fps add(Fps refreshRate, nsecs_t now, const RefreshRateSelector&);

    private:
        friend class LayerHistoryTest;
        friend class LayerHistoryIntegrationTest;

        // Holds the refresh rate when it was calculated
        struct RefreshRateData {
            Fps refreshRate;
            nsecs_t timestamp = 0;
        };

        // Holds tracing strings
        struct HeuristicTraceTagData {
            std::string min;
            std::string max;
            std::string consistent;
            std::string average;
        };

        Fps selectRefreshRate(const RefreshRateSelector&) const;
        HeuristicTraceTagData makeHeuristicTraceTagData() const;

        const std::string mName;
        mutable std::optional<HeuristicTraceTagData> mHeuristicTraceTagData;
        std::deque<RefreshRateData> mRefreshRates;
        static constexpr float MARGIN_CONSISTENT_FPS = 1.0;
        static constexpr float MARGIN_CONSISTENT_FPS_FOR_CLOSEST_REFRESH_RATE = 5.0;
    };

    // Represents whether we were able to determine either layer is frequent or infrequent
    bool mIsFrequencyConclusive = true;
    struct Frequent {
        bool isFrequent;
        bool clearHistory;
        // Represents whether we were able to determine isFrequent conclusively
        bool isConclusive;
        // Represents whether the latest frames are small dirty.
        bool isSmallDirty = false;
    };
    Frequent isFrequent(nsecs_t now) const;
    bool isAnimating(nsecs_t now) const;
    bool hasEnoughDataForHeuristic() const;
    std::optional<Fps> calculateRefreshRateIfPossible(const RefreshRateSelector&, nsecs_t now);
    std::optional<nsecs_t> calculateAverageFrameTime() const;
    bool isFrameTimeValid(const FrameTimeData&) const;

    const std::string mName;
    const uid_t mOwnerUid;

    // Used for sanitizing the heuristic data. If two frames are less than
    // this period apart from each other they'll be considered as duplicates.
    static constexpr nsecs_t kMinPeriodBetweenFrames = (240_Hz).getPeriodNsecs();
    // Used for sanitizing the heuristic data. If two frames are more than
    // this period apart from each other, the interval between them won't be
    // taken into account when calculating average frame rate.
    static constexpr nsecs_t kMaxPeriodBetweenFrames = kMinFpsForFrequentLayer.getPeriodNsecs();
    // Used for sanitizing the heuristic data. If frames are small dirty updating and are less
    // than this period apart from each other, the interval between them won't be
    // taken into account when calculating average frame rate.
    static constexpr nsecs_t kMinPeriodBetweenSmallDirtyFrames = (60_Hz).getPeriodNsecs();

    LayerHistory::LayerVoteType mDefaultVote;

    LayerVote mLayerVote;

    nsecs_t mLastUpdatedTime = 0;

    nsecs_t mLastAnimationTime = 0;

    RefreshRateHeuristicData mLastRefreshRate;

    std::deque<FrameTimeData> mFrameTimes;
    std::chrono::time_point<std::chrono::steady_clock> mFrameTimeValidSince =
            std::chrono::steady_clock::now();
    static constexpr size_t HISTORY_SIZE = RefreshRateHistory::HISTORY_SIZE;
    static constexpr std::chrono::nanoseconds HISTORY_DURATION = LayerHistory::kMaxPeriodForHistory;

    std::unique_ptr<LayerProps> mLayerProps;

    RefreshRateHistory mRefreshRateHistory;

    // This will be accessed from only one thread when counting a layer is frequent or infrequent,
    // and to determine whether a layer is in small dirty updating.
    mutable int32_t mLastSmallDirtyCount = 0;

    mutable std::unordered_map<LayerHistory::LayerVoteType, std::string> mTraceTags;

    // Shared for all LayerInfo instances
    static bool sTraceEnabled;
};

struct LayerProps {
    bool visible = false;
    FloatRect bounds;
    ui::Transform transform;
    LayerInfo::FrameRate setFrameRateVote;
    int32_t frameRateSelectionPriority = -1;
    bool isSmallDirty = false;
    bool isFrontBuffered = false;
};

} // namespace scheduler
} // namespace android