/**
 * @file device_provider.hpp
 * @brief OpenVR device provider for the MicMap sidecar driver.
 *
 * The MicMap driver is a pure sidecar: it registers ZERO tracked devices and
 * instead creates a `/input/system/click` boolean component directly on the
 * HMD property container. Press commands arrive via an HTTP server running
 * on a worker thread; they are enqueued on a CommandQueue and drained in
 * RunFrame on the SteamVR driver thread (which is where the OpenVR driver-API
 * calls legally live). See .planning/phases/01-driver-sidecar-migration/
 * 01-RESEARCH.md Pattern 1 for the full state machine.
 */

#pragma once

#include <openvr_driver.h>

#include <atomic>
#include <chrono>
#include <memory>
#include <optional>

namespace micmap::driver {

// Forward declarations
class HttpServer;
class CommandQueue;

/**
 * @brief HMD `/input/system/click` component lifecycle state (Pattern 1).
 *
 * - NotReady: cold-start; we have not yet observed a valid HMD property
 *   container. Next RunFrame will poll for one.
 * - Ready: CreateBooleanComponent succeeded and hSystemClick_ is valid.
 *   UpdateBooleanComponent may be called.
 * - Invalidated: HMD was deactivated OR an UpdateBooleanComponent call
 *   returned a non-None error. RunFrame will attempt to recreate on the
 *   next tick.
 */
enum class HmdComponentState {
    NotReady,
    Ready,
    Invalidated
};

/**
 * @brief Device provider implementing IServerTrackedDeviceProvider.
 *
 * This provider does NOT call TrackedDeviceAdded. It owns:
 *   - An HttpServer (worker thread, localhost-only).
 *   - A CommandQueue (MPSC, depth-8, drop-oldest).
 *   - A single VRInputComponentHandle_t for /input/system/click on the HMD
 *     property container.
 *   - Min-hold / max-hold state for the button-press safety envelope.
 */
class DeviceProvider : public vr::IServerTrackedDeviceProvider {
public:
    DeviceProvider();
    ~DeviceProvider();

    // IServerTrackedDeviceProvider interface
    vr::EVRInitError Init(vr::IVRDriverContext* pDriverContext) override;
    void Cleanup() override;
    const char* const* GetInterfaceVersions() override;
    void RunFrame() override;
    bool ShouldBlockStandbyMode() override;
    void EnterStandby() override;
    void LeaveStandby() override;

private:
    /**
     * @brief Write a new value to /input/system/click if it differs from the
     * last written value. On error, invalidates handle + flips to Invalidated.
     */
    void writeValue(bool v);

    std::unique_ptr<CommandQueue> commandQueue_;
    std::unique_ptr<HttpServer> httpServer_;

    vr::VRInputComponentHandle_t hSystemClick_{vr::k_ulInvalidInputComponentHandle};
    HmdComponentState state_{HmdComponentState::NotReady};

    // Min-hold timing (D-04, D-05)
    std::chrono::steady_clock::time_point pressTimestamp_{};
    std::optional<std::chrono::steady_clock::time_point> pendingReleaseAt_;
    bool isPressed_{false};
    bool lastWrittenValue_{false};

    // Transition-only logging flags (D-08)
    bool initLogged_{false};
    bool loggedAwaitingHmd_{false};

    std::atomic<bool> initialized_{false};

    // Min-hold / max-hold durations
    static constexpr std::chrono::milliseconds kMinHold{100};
    static constexpr std::chrono::milliseconds kMaxHold{5000};
};

} // namespace micmap::driver