/*
 * Copyright 2024 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 <memory>
#include <mutex>
#include <string>
#include <utility>
#include <variant>

#include <android-base/thread_annotations.h>
#include <ftl/function.h>
#include <ftl/optional.h>
#include <ui/DisplayId.h>
#include <ui/DisplayMap.h>

#include "Display/DisplayModeRequest.h"
#include "Display/DisplaySnapshotRef.h"
#include "DisplayHardware/DisplayMode.h"
#include "Scheduler/RefreshRateSelector.h"
#include "ThreadContext.h"
#include "TracedOrdinal.h"

namespace android {
class HWComposer;
} // namespace android

namespace android::display {

// Selects the DisplayMode of each physical display, in accordance with DisplayManager policy and
// certain heuristic signals.
class DisplayModeController {
public:
    using ActiveModeListener = ftl::Function<void(PhysicalDisplayId, Fps vsyncRate, Fps renderFps)>;

    DisplayModeController();

    void setHwComposer(HWComposer* composerPtr) { mComposerPtr = composerPtr; }
    void setActiveModeListener(const ActiveModeListener& listener) {
        mActiveModeListener = listener;
    }

    // TODO: b/241285876 - Remove once ownership is no longer shared with DisplayDevice.
    using RefreshRateSelectorPtr = std::shared_ptr<scheduler::RefreshRateSelector>;

    // Used by tests to inject an existing RefreshRateSelector.
    // TODO: b/241285876 - Remove this.
    void registerDisplay(PhysicalDisplayId, DisplaySnapshotRef, RefreshRateSelectorPtr)
            EXCLUDES(mDisplayLock);

    // The referenced DisplaySnapshot must outlive the registration.
    void registerDisplay(DisplaySnapshotRef, DisplayModeId, scheduler::RefreshRateSelector::Config)
            REQUIRES(kMainThreadContext) EXCLUDES(mDisplayLock);
    void unregisterDisplay(PhysicalDisplayId) REQUIRES(kMainThreadContext) EXCLUDES(mDisplayLock);

    // Returns `nullptr` if the display is no longer registered (or never was).
    RefreshRateSelectorPtr selectorPtrFor(PhysicalDisplayId) const EXCLUDES(mDisplayLock);

    enum class DesiredModeAction { None, InitiateDisplayModeSwitch, InitiateRenderRateSwitch };
    enum class ModeChangeResult { Changed, Rejected, Aborted };

    DesiredModeAction setDesiredMode(PhysicalDisplayId, DisplayModeRequest&&)
            EXCLUDES(mDisplayLock);

    using DisplayModeRequestOpt = ftl::Optional<DisplayModeRequest>;

    DisplayModeRequestOpt getDesiredMode(PhysicalDisplayId) const EXCLUDES(mDisplayLock);

    // Consumes the display's desired mode if one exists. If it does not match the active resolution
    // (i.e. the DisplayModeRequest is a resolution switch), then it must match `expectedResolution`
    // for it to be consumed.
    DisplayModeRequestOpt takeDesiredModeIfMatches(PhysicalDisplayId, ui::Size expectedResolution)
            EXCLUDES(mDisplayLock);

    // TODO: Remove once `modeset_state_machine` flag is cleaned up.
    void clearDesiredMode(PhysicalDisplayId) EXCLUDES(mDisplayLock);

    DisplayModeRequestOpt getPendingMode(PhysicalDisplayId) const REQUIRES(kMainThreadContext)
            EXCLUDES(mDisplayLock);
    bool isModeSetPending(PhysicalDisplayId) const REQUIRES(kMainThreadContext)
            EXCLUDES(mDisplayLock);

    scheduler::FrameRateMode getActiveMode(PhysicalDisplayId) const EXCLUDES(mDisplayLock);

    ModeChangeResult initiateModeChange(PhysicalDisplayId, DisplayModeRequest&&,
                                        const hal::VsyncPeriodChangeConstraints&,
                                        hal::VsyncPeriodChangeTimeline& outTimeline)
            REQUIRES(kMainThreadContext) EXCLUDES(mDisplayLock);

    // TODO: Remove once `modeset_state_machine` flag is cleaned up.
    void finalizeModeChange(PhysicalDisplayId, DisplayModeId, Fps vsyncRate, Fps renderFps)
            REQUIRES(kMainThreadContext) EXCLUDES(mDisplayLock);

    struct NoModeChange {
        const char* reason;
    };

    struct ResolutionChange {
        DisplayModeRequest activeMode;
    };

    struct RefreshRateChange {
        DisplayModeRequest activeMode;
    };

    using ModeChange = std::variant<NoModeChange, ResolutionChange, RefreshRateChange>;

    // Clears the pending DisplayModeRequest, and returns the ModeChange that occurred.
    ModeChange finalizeModeChange(PhysicalDisplayId) REQUIRES(kMainThreadContext)
            EXCLUDES(mDisplayLock);

    void setActiveMode(PhysicalDisplayId, DisplayModeId, Fps vsyncRate, Fps renderFps)
            EXCLUDES(mDisplayLock);

    void updateKernelIdleTimer(PhysicalDisplayId) REQUIRES(kMainThreadContext)
            EXCLUDES(mDisplayLock);

    struct KernelIdleTimerState {
        std::optional<DisplayModeId> desiredModeIdOpt = std::nullopt;
        bool isEnabled = false;
    };

    KernelIdleTimerState getKernelIdleTimerState(PhysicalDisplayId) const
            REQUIRES(kMainThreadContext) EXCLUDES(mDisplayLock);

    void setSecure(PhysicalDisplayId displayId, bool secure) REQUIRES(kMainThreadContext)
            EXCLUDES(mDisplayLock);

    bool supportsHdcp() const;

    void startHdcpNegotiation(PhysicalDisplayId displayId) REQUIRES(kMainThreadContext);

private:
    enum class HdcpState { Undesired, Desired, Enabled };

    struct Display {
        template <size_t N>
        std::string concatId(const char (&)[N]) const;

        Display(DisplaySnapshotRef, RefreshRateSelectorPtr);
        Display(DisplaySnapshotRef snapshot, DisplayModes modes, DisplayModeId activeModeId,
                scheduler::RefreshRateSelector::Config config)
              : Display(snapshot,
                        std::make_shared<scheduler::RefreshRateSelector>(std::move(modes),
                                                                         activeModeId, config)) {}

        void setSecure(bool secure) {
            hdcpState = secure ? HdcpState::Undesired : HdcpState::Desired;
        }

        const DisplaySnapshotRef snapshot;
        const RefreshRateSelectorPtr selectorPtr;

        const std::string pendingModeFpsTrace;
        const std::string activeModeFpsTrace;
        const std::string renderRateFpsTrace;

        // A DisplayModeRequest flows through three states: desired, pending, and active. Requests
        // within a frame are merged into a single desired request. Unless cleared, the request is
        // relayed to HWC on the next frame, and becomes pending. The mode becomes active once HWC
        // signals the present fence to confirm the mode set.
        std::mutex desiredModeLock;
        DisplayModeRequestOpt desiredModeOpt GUARDED_BY(desiredModeLock);
        TracedOrdinal<bool> hasDesiredModeTrace GUARDED_BY(desiredModeLock);

        DisplayModeRequestOpt pendingModeOpt GUARDED_BY(kMainThreadContext);

        // TODO: Remove once `modeset_state_machine` flag is cleaned up.
        bool isModeSetPending GUARDED_BY(kMainThreadContext) = false;

        bool isKernelIdleTimerEnabled GUARDED_BY(kMainThreadContext) = false;

        HdcpState hdcpState = HdcpState::Desired;
    };

    using DisplayPtr = std::unique_ptr<Display>;

    void setActiveModeLocked(PhysicalDisplayId, DisplayModeId, Fps vsyncRate, Fps renderFps)
            REQUIRES(mDisplayLock);

    using KernelIdleTimerController = scheduler::RefreshRateSelector::KernelIdleTimerController;
    void updateKernelIdleTimer(PhysicalDisplayId, std::chrono::milliseconds timeout,
                               KernelIdleTimerController) REQUIRES(mDisplayLock);

    // Set once when initializing the DisplayModeController, which the HWComposer must outlive.
    HWComposer* mComposerPtr = nullptr;

    ActiveModeListener mActiveModeListener;

    mutable std::mutex mDisplayLock;
    ui::PhysicalDisplayMap<PhysicalDisplayId, DisplayPtr> mDisplays GUARDED_BY(mDisplayLock);

    bool mSupportsHdcp = false;
};

} // namespace android::display