using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;

namespace RGB.NET.Core;

/// <summary>
/// Represents the abstract base implementation for a <see cref="IRGBDeviceProvider"/>.
/// </summary>
public abstract class AbstractRGBDeviceProvider : IRGBDeviceProvider
{
    #region Properties & Fields

    private bool _isDisposed = false;

    private readonly double _defaultUpdateRateHardLimit;

    /// <inheritdoc />
    public bool IsInitialized { get; protected set; }

    /// <inheritdoc />
    public bool ThrowsExceptions { get; protected set; }

    /// <summary>
    /// The list of devices managed by this device-provider.
    /// </summary>
    protected List<IRGBDevice> InternalDevices { get; } = [];

    /// <inheritdoc />
    public virtual IReadOnlyList<IRGBDevice> Devices => new ReadOnlyCollection<IRGBDevice>(InternalDevices);

    /// <summary>
    /// Gets the dictionary containing the registered update triggers.
    /// Normally <see cref="UpdateTriggers"/> should be used to access them.
    /// </summary>
    protected Dictionary<int, IDeviceUpdateTrigger> UpdateTriggerMapping { get; } = [];

    /// <inheritdoc />
    public IReadOnlyList<(int id, IDeviceUpdateTrigger trigger)> UpdateTriggers => new ReadOnlyCollection<(int id, IDeviceUpdateTrigger trigger)>(UpdateTriggerMapping.Select(x => (x.Key, x.Value)).ToList());

    #endregion

    #region Events

    /// <inheritdoc />
    public event EventHandler<ExceptionEventArgs>? Exception;

    /// <inheritdoc />
    public event EventHandler<DevicesChangedEventArgs>? DevicesChanged;

    #endregion

    #region Constructors

    /// <summary>
    /// Initializes a new instance of the <see cref="AbstractRGBDeviceProvider" /> class.
    /// </summary>
    /// <param name="defaultUpdateRateHardLimit">The update rate hard limit all update triggers for this device provider are initialized with.</param>
    protected AbstractRGBDeviceProvider(double defaultUpdateRateHardLimit = 0)
    {
        this._defaultUpdateRateHardLimit = defaultUpdateRateHardLimit;
    }

    ~AbstractRGBDeviceProvider() => Dispose(false);

    #endregion

    #region Methods

    /// <inheritdoc />
    public bool Initialize(RGBDeviceType loadFilter = RGBDeviceType.All, bool throwExceptions = false)
    {
        if (_isDisposed) throw new ObjectDisposedException(GetType().FullName);

        ThrowsExceptions = throwExceptions;

        try
        {
            Reset();

            InitializeSDK();

            foreach (IRGBDevice device in GetLoadedDevices(loadFilter))
                AddDevice(device);

            foreach (IDeviceUpdateTrigger updateTrigger in UpdateTriggerMapping.Values)
                updateTrigger.Start();

            IsInitialized = true;
        }
        catch (DeviceProviderException)
        {
            Reset();
            throw;
        }
        catch (Exception ex)
        {
            Reset();
            Throw(ex, true);
            return false;
        }

        return true;
    }

    /// <summary>
    /// Loads devices and returns a filtered list of them.
    /// </summary>
    /// <remarks> 
    /// The underlying loading of the devices happens in <see cref="LoadDevices"/>.
    /// </remarks>
    /// <param name="loadFilter"><see cref="RGBDeviceType"/>-flags to filter the device with.</param>
    /// <returns>The filtered collection of loaded devices.</returns>
    protected virtual IEnumerable<IRGBDevice> GetLoadedDevices(RGBDeviceType loadFilter)
    {
        if (_isDisposed) throw new ObjectDisposedException(GetType().FullName);

        List<IRGBDevice> devices = [];
        foreach (IRGBDevice device in LoadDevices())
        {
            try
            {
                if (loadFilter.HasFlag(device.DeviceInfo.DeviceType))
                    devices.Add(device);
                else
                    device.Dispose();
            }
            catch (Exception ex)
            {
                Throw(ex);
            }
        }

        return devices;
    }

    /// <summary>
    /// Initializes the underlying SDK.
    /// </summary>
    protected abstract void InitializeSDK();

    /// <summary>
    /// Loads all devices this device provider is capable of loading.
    /// </summary>
    /// <remarks> 
    /// Filtering happens in <see cref="GetLoadedDevices"/>.
    /// </remarks>
    /// <returns>A collection of loaded devices.</returns>
    protected abstract IEnumerable<IRGBDevice> LoadDevices();

    /// <summary>
    /// Gets the <see cref="IDeviceUpdateTrigger"/> mapped to the specified id or a new one if the id wasn't requested before.
    /// </summary>
    /// <remarks>
    /// The creation of the update trigger happens in <see cref="CreateUpdateTrigger"/>.
    /// </remarks>
    /// <param name="id">The id of the update trigger.</param>
    /// <param name="updateRateHardLimit">The update rate hard limit to be set in the update trigger.</param>
    /// <returns>The update trigger mapped to the specified id.</returns>
    protected virtual IDeviceUpdateTrigger GetUpdateTrigger(int id = -1, double? updateRateHardLimit = null)
    {
        if (_isDisposed) throw new ObjectDisposedException(GetType().FullName);

        if (!UpdateTriggerMapping.TryGetValue(id, out IDeviceUpdateTrigger? updaeTrigger))
            UpdateTriggerMapping[id] = (updaeTrigger = CreateUpdateTrigger(id, updateRateHardLimit ?? _defaultUpdateRateHardLimit));

        return updaeTrigger;
    }

    /// <summary>
    /// Creates a update trigger with the specified id and the specified update rate hard limit.
    /// </summary>
    /// <param name="id">The id of the update trigger.</param>
    /// <param name="updateRateHardLimit">The update rate hard limit tobe  set in the update trigger.</param>
    /// <returns>The newly created update trigger.</returns>
    protected virtual IDeviceUpdateTrigger CreateUpdateTrigger(int id, double updateRateHardLimit) => new DeviceUpdateTrigger(updateRateHardLimit);

    /// <summary>
    /// Resets the device provider and disposes all devices and update triggers.
    /// </summary>
    protected virtual void Reset()
    {
        if (_isDisposed) throw new ObjectDisposedException(GetType().FullName);

        foreach (IDeviceUpdateTrigger updateTrigger in UpdateTriggerMapping.Values)
            updateTrigger.Dispose();

        foreach (IRGBDevice device in Devices)
            device.Dispose();

        List<IRGBDevice> devices = [..InternalDevices];
        foreach (IRGBDevice device in devices)
            RemoveDevice(device);

        UpdateTriggerMapping.Clear();
        IsInitialized = false;
    }

    /// <summary>
    /// Adds the provided device to the list of managed devices.
    /// </summary>
    /// <param name="device">The device to add.</param>
    /// <returns><c>true</c> if the device was added successfully; otherwise <c>false</c>.</returns>
    protected virtual bool AddDevice(IRGBDevice device)
    {
        if (_isDisposed) throw new ObjectDisposedException(GetType().FullName);

        if (InternalDevices.Contains(device)) return false;

        InternalDevices.Add(device);
        try { OnDevicesChanged(DevicesChangedEventArgs.CreateDevicesAddedArgs(device)); } catch { /* we don't want to throw due to bad event handlers */ }

        return true;
    }

    /// <summary>
    /// Removes the provided device from the list of managed devices.
    /// </summary>
    /// <param name="device">The device to remove.</param>
    /// <returns><c>true</c> if the device was removed successfully; otherwise <c>false</c>.</returns>
    protected virtual bool RemoveDevice(IRGBDevice device)
    {
        if (_isDisposed) throw new ObjectDisposedException(GetType().FullName);

        if (!InternalDevices.Remove(device)) return false;

        try { OnDevicesChanged(DevicesChangedEventArgs.CreateDevicesRemovedArgs(device)); } catch { /* we don't want to throw due to bad event handlers */ }

        return true;
    }

    /// <summary>
    /// Triggers the <see cref="Exception"/>-event and throws the specified exception if <see cref="ThrowsExceptions"/> is true and it is not overriden in the event.
    /// </summary>
    /// <param name="ex">The exception to throw.</param>
    /// <param name="isCritical">Indicates if the exception is critical for device provider to work correctly.</param>
    public virtual void Throw(Exception ex, bool isCritical = false)
    {
        ExceptionEventArgs args = new(ex, isCritical, ThrowsExceptions);
        try { OnException(args); } catch { /* we don't want to throw due to bad event handlers */ }

        if (args.Throw)
            throw new DeviceProviderException(ex, isCritical);
    }

    /// <summary>
    /// Throws the <see cref="Exception"/>.event.
    /// </summary>
    /// <param name="args">The parameters passed to the event.</param>
    protected virtual void OnException(ExceptionEventArgs args) => Exception?.Invoke(this, args);

    /// <summary>
    /// Throws the <see cref="DevicesChanged"/>-event.
    /// </summary>
    /// <param name="args">The parameters passed to the event.</param>
    protected virtual void OnDevicesChanged(DevicesChangedEventArgs args) => DevicesChanged?.Invoke(this, args);

    /// <inheritdoc />
    public void Dispose()
    {
        if (_isDisposed) return;

        try
        {
            Dispose(true);
        }
        catch { /* don't throw in dispose! */ }

        GC.SuppressFinalize(this);

        _isDisposed = true;
    }

    /// <summary>
    /// Disposes the object and frees all resources.
    /// </summary>
    /// <param name="disposing"><c>true</c> if explicitely called through the Dispose-Method, <c>false</c> if called by the destructor.</param>
    protected virtual void Dispose(bool disposing) => Reset();

    #endregion
}