// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.

using System;
using System.Collections.Generic;
using UnityEngine;

namespace Microsoft.MixedReality.Toolkit.SpatialAwareness
{
    public interface IMixedRealitySpatialAwarenessSystem : IMixedRealityEventSystem
    {
        /// <summary>
        /// Gets the parent object to which all spatial awareness <see href="https://docs.unity3d.com/ScriptReference/GameObject.html">GameObject</see>s are to be parented.
        /// </summary>
        GameObject SpatialAwarenessObjectParent { get; }

        /// <summary>
        /// Creates the a parent, that is a child of the Spatial Awareness System parent so that the scene hierarchy does not get overly cluttered.
        /// </summary>
        /// <returns>
        /// The <see href="https://docs.unity3d.com/ScriptReference/GameObject.html">GameObject</see> to which spatial awareness objects will be parented.
        /// </returns>
        /// <remarks>
        /// <para>This method is to be called by implementations of the <see cref="IMixedRealitySpatialAwarenessObserver"/> interface, not by application code. It
        /// is used to enable observations to be grouped by observer.</para>
        /// </remarks>
        GameObject CreateSpatialAwarenessObservationParent(string name);

        /// <summary>
        /// Generates a new source identifier for an <see cref="IMixedRealitySpatialAwarenessObserver"/> implementation.
        /// </summary>
        /// <returns>The source identifier to be used by the <see cref="IMixedRealitySpatialAwarenessObserver"/> implementation.</returns>
        /// <remarks>
        /// This method is to be called by implementations of the <see cref="IMixedRealitySpatialAwarenessObserver"/> interface, not by application code.
        /// </remarks>
        uint GenerateNewSourceId();

        /// <summary>
        /// Typed representation of the ConfigurationProfile property.
        /// </summary>
        MixedRealitySpatialAwarenessSystemProfile SpatialAwarenessSystemProfile { get; }

        /// <summary>
        /// Gets the collection of registered <see cref="IMixedRealitySpatialAwarenessObserver"/> data providers.
        /// </summary>
        /// <returns>
        /// Read only copy of the list of registered observers.
        /// </returns>
        [Obsolete("GetObservers will be removed in a future release. Cast to IMixedRealityDataProviderAccess and call GetDataProviders instead")]
        IReadOnlyList<IMixedRealitySpatialAwarenessObserver> GetObservers();

        /// <summary>
        /// Get the collection of registered observers of the specified type.
        /// </summary>
        /// <typeparam name="T">The desired spatial awareness observer type (ex: <see cref="IMixedRealitySpatialAwarenessMeshObserver"/>)</typeparam>
        /// <returns>
        /// Readonly copy of the list of registered observers that implement the specified type.
        /// </returns>
        [Obsolete("GetObservers<T> will be removed in a future release. Cast to IMixedRealityDataProviderAccess and call GetDataProviders<T> instead")]
        IReadOnlyList<T> GetObservers<T>() where T : IMixedRealitySpatialAwarenessObserver;

        /// <summary>
        /// Get the <see cref="IMixedRealitySpatialAwarenessObserver"/> that is registered under the specified name.
        /// </summary>
        /// <param name="name">The friendly name of the observer.</param>
        /// <returns>
        /// The requested observer, or null if one cannot be found.
        /// </returns>
        /// <remarks>
        /// If more than one observer is registered under the specified name, the first will be returned.
        /// </remarks>
        [Obsolete("GetObserver will be removed in a future release. Cast to IMixedRealityDataProviderAccess and call GetDataProvider instead")]
        IMixedRealitySpatialAwarenessObserver GetObserver(string name);

        /// <summary>
        /// Get the observer that is registered under the specified name matching the specified type.
        /// </summary>
        /// <typeparam name="T">The desired spatial awareness observer type (ex: <see cref="IMixedRealitySpatialAwarenessMeshObserver"/>)</typeparam>
        /// <param name="name">The friendly name of the observer.</param>
        /// <returns>
        /// The requested observer, or null if one cannot be found.
        /// </returns>
        /// <remarks>
        /// If more than one observer is registered under the specified name, the first will be returned.
        /// </remarks>
        [Obsolete("GetObserver<T> will be removed in a future release. Cast to IMixedRealityDataProviderAccess and call GetDataProvider<T> instead")]
        T GetObserver<T>(string name = null) where T : IMixedRealitySpatialAwarenessObserver;

        /// <summary>
        /// Starts / restarts all spatial observers of the specified type.
        /// </summary>
        void ResumeObservers();

        /// <summary>
        /// Starts / restarts all spatial observers of the specified type.
        /// </summary>
        /// <typeparam name="T">The desired spatial awareness observer type (ex: <see cref="IMixedRealitySpatialAwarenessMeshObserver"/>)</typeparam>
        void ResumeObservers<T>() where T : IMixedRealitySpatialAwarenessObserver;

        /// <summary>
        /// Starts / restarts the spatial observer registered under the specified name matching the specified type.
        /// </summary>
        /// <typeparam name="T">The desired spatial awareness observer type (ex: <see cref="IMixedRealitySpatialAwarenessMeshObserver"/>)</typeparam>
        /// <param name="name">The friendly name of the observer.</param>
        void ResumeObserver<T>(string name) where T : IMixedRealitySpatialAwarenessObserver;

        /// <summary>
        /// Stops / pauses all spatial observers.
        /// </summary>
        void SuspendObservers();

        /// <summary>
        /// Stops / pauses all spatial observers of the specified type.
        /// </summary>
        void SuspendObservers<T>() where T : IMixedRealitySpatialAwarenessObserver;

        /// <summary>
        /// Stops / pauses the spatial observer registered under the specified name matching the specified type.
        /// </summary>
        /// <typeparam name="T">The desired spatial awareness observer type (ex: <see cref="IMixedRealitySpatialAwarenessMeshObserver"/>)</typeparam>
        /// <param name="name">The friendly name of the observer.</param>
        void SuspendObserver<T>(string name) where T : IMixedRealitySpatialAwarenessObserver;

        /// <summary>
        /// Clears all registered observers' observations.
        /// </summary>
        void ClearObservations();

        /// <summary>
        /// Clears the observations of the specified observer.
        /// </summary>
        /// <typeparam name="T">The observer type.</typeparam>
        /// <param name="name">The name of the observer.</param>
        void ClearObservations<T>(string name = null) where T : IMixedRealitySpatialAwarenessObserver;
    }
}