using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

using Swan;

namespace Unosquare.RaspberryIO.Computer {
  /// <summary>
  /// Represents the Bluetooth information.
  /// </summary>
  public class Bluetooth : SingletonBase<Bluetooth> {
    private const String BcCommand = "bluetoothctl";

    /// <summary>
    /// Turns on the Bluetooth adapter.
    /// </summary>
    /// <param name="cancellationToken">The cancellation token.</param>
    /// <returns>
    /// Returns true or false depending if the controller was turned on.
    /// </returns>
    /// <exception cref="BluetoothErrorException">Failed to power on:.</exception>
    public async Task<Boolean> PowerOn(CancellationToken cancellationToken = default) {
      try {
        String output = await ProcessRunner.GetProcessOutputAsync(BcCommand, "power on", null, cancellationToken).ConfigureAwait(false);
        return output.Contains("succeeded");
      } catch(Exception ex) {
        throw new BluetoothErrorException($"Failed to power on: {ex.Message}");
      }
    }

    /// <summary>
    /// Turns off the bluetooth adapter.
    /// </summary>
    /// <param name="cancellationToken">The cancellation token.</param>
    /// <returns>
    /// Returns true or false depending if the controller was turned off.
    /// </returns>
    /// <exception cref="BluetoothErrorException">Failed to power off:.</exception>
    public async Task<Boolean> PowerOff(CancellationToken cancellationToken = default) {
      try {
        String output = await ProcessRunner.GetProcessOutputAsync(BcCommand, "power off", null, cancellationToken).ConfigureAwait(false);
        return output.Contains("succeeded");
      } catch(Exception ex) {
        throw new BluetoothErrorException($"Failed to power off: {ex.Message}");
      }
    }

    /// <summary>
    /// Gets the list of detected devices.
    /// </summary>
    /// <param name="cancellationToken">The cancellation token.</param>
    /// <returns>
    /// Returns the list of detected devices.
    /// </returns>
    /// <exception cref="BluetoothErrorException">Failed to retrieve devices:.</exception>
    public async Task<IEnumerable<String>> ListDevices(CancellationToken cancellationToken = default) {
      try {
        using CancellationTokenSource cancellationTokenSource = new CancellationTokenSource(3000);
        _ = await ProcessRunner.GetProcessOutputAsync(BcCommand, "scan on", null, cancellationTokenSource.Token).ConfigureAwait(false);
        _ = await ProcessRunner.GetProcessOutputAsync(BcCommand, "scan off", null, cancellationToken).ConfigureAwait(false);
        String devices = await ProcessRunner.GetProcessOutputAsync(BcCommand, "devices", null, cancellationToken).ConfigureAwait(false);
        return devices.Trim().Split('\n').Select(x => x.Trim());
      } catch(Exception ex) {
        throw new BluetoothErrorException($"Failed to retrieve devices: {ex.Message}");
      }
    }

    /// <summary>
    /// Gets the list of bluetooth controllers.
    /// </summary>
    /// <param name="cancellationToken">The cancellation token.</param>
    /// <returns>
    /// Returns the list of bluetooth controllers.
    /// </returns>
    /// <exception cref="BluetoothErrorException">Failed to retrieve controllers:.</exception>
    public async Task<IEnumerable<String>> ListControllers(CancellationToken cancellationToken = default) {
      try {
        String controllers = await ProcessRunner.GetProcessOutputAsync(BcCommand, "list", null, cancellationToken).ConfigureAwait(false);
        return controllers.Trim().Split('\n').Select(x => x.Trim());
      } catch(Exception ex) {
        throw new BluetoothErrorException($"Failed to retrieve controllers: {ex.Message}");
      }
    }

    /// <summary>
    /// Pairs a specific device with a specific controller.
    /// </summary>
    /// <param name="controllerAddress">The mac address of the controller that will be used to pair.</param>
    /// <param name="deviceAddress">The mac address of the device that will be paired.</param>
    /// <param name="cancellationToken">The cancellation token.</param>
    /// <returns>
    /// Returns true or false if the pair was successfully.
    /// </returns>
    /// <exception cref="BluetoothErrorException">Failed to Pair:.</exception>
    public async Task<Boolean> Pair(String controllerAddress, String deviceAddress, CancellationToken cancellationToken = default) {
      try {
        // Selects the controller to pair. Once you select the controller, all controller-related commands will apply to it for three minutes.
        _ = await ProcessRunner.GetProcessOutputAsync(BcCommand, $"select {controllerAddress}", null, cancellationToken).ConfigureAwait(false);

        // Makes the controller visible to other devices.
        _ = await ProcessRunner.GetProcessOutputAsync(BcCommand, "discoverable on", null, cancellationToken).ConfigureAwait(false);

        // Readies the controller for pairing. Remember that you have three minutes after running this command to pair.
        _ = await ProcessRunner.GetProcessOutputAsync(BcCommand, "pairable on", null, cancellationToken).ConfigureAwait(false);

        // Pairs the device with the controller.
        String result = await ProcessRunner.GetProcessOutputAsync(BcCommand, $"pair {deviceAddress}", null, cancellationToken).ConfigureAwait(false);

        // Hides the controller from other Bluetooth devices. Otherwise, any device that can detect it has access to it, leaving a major security hole.
        _ = await ProcessRunner.GetProcessOutputAsync(BcCommand, "discoverable off", null, cancellationToken).ConfigureAwait(false);

        return result.Contains("Paired: yes");
      } catch(Exception ex) {
        throw new BluetoothErrorException($"Failed to Pair: {ex.Message}");
      }
    }

    /// <summary>
    /// Performs a connection of a given controller with a given device.
    /// </summary>
    /// <param name="controllerAddress">The mac address of the controller that will be used to make the connection.</param>
    /// <param name="deviceAddress">The mac address of the device that will be connected.</param>
    /// <param name="cancellationToken">The cancellation token.</param>
    /// <returns>
    /// Returns true or false if the connection was successfully.
    /// </returns>
    /// <exception cref="BluetoothErrorException">Failed to connect:.</exception>
    public async Task<Boolean> Connect(String controllerAddress, String deviceAddress, CancellationToken cancellationToken = default) {
      try {
        // Selects the controller to pair. Once you select the controller, all controller-related commands will apply to it for three minutes.
        _ = await ProcessRunner.GetProcessOutputAsync(BcCommand, $"select {controllerAddress}", null, cancellationToken).ConfigureAwait(false);

        // Makes the controller visible to other devices.
        _ = await ProcessRunner.GetProcessOutputAsync(BcCommand, "discoverable on", null, cancellationToken).ConfigureAwait(false);

        // Readies the controller for pairing. Remember that you have three minutes after running this command to pair.
        _ = await ProcessRunner.GetProcessOutputAsync(BcCommand, "pairable on", null, cancellationToken).ConfigureAwait(false);

        // Readies the device for pairing.
        String result = await ProcessRunner.GetProcessOutputAsync(BcCommand, $"connect {deviceAddress}", null, cancellationToken).ConfigureAwait(false);

        // Hides the controller from other Bluetooth devices. Otherwise, any device that can detect it has access to it, leaving a major security hole.
        _ = await ProcessRunner.GetProcessOutputAsync(BcCommand, "discoverable off", null, cancellationToken).ConfigureAwait(false);

        return result.Contains("Connected: yes");
      } catch(Exception ex) {
        throw new BluetoothErrorException($"Failed to connect: {ex.Message}");
      }
    }

    /// <summary>
    /// Sets the device to re-pair automatically when it is turned on, which eliminates the need to pair all over again.
    /// </summary>
    /// <param name="controllerAddress">The mac address of the controller will be used.</param>
    /// <param name="deviceAddress">The mac address of the device will be added to the trust list devices.</param>
    /// <param name="cancellationToken">The cancellation token.</param>
    /// <returns>
    /// Returns true or false if the operation was successful.
    /// </returns>
    /// <exception cref="BluetoothErrorException">Failed to add to trust devices list:.</exception>
    public async Task<Boolean> Trust(String controllerAddress, String deviceAddress, CancellationToken cancellationToken = default) {
      try {
        // Selects the controller to pair. Once you select the controller, all controller-related commands will apply to it for three minutes.
        _ = await ProcessRunner.GetProcessOutputAsync(BcCommand, $"select {controllerAddress}", null, cancellationToken).ConfigureAwait(false);

        // Makes the controller visible to other devices.
        _ = await ProcessRunner.GetProcessOutputAsync(BcCommand, "discoverable on", null, cancellationToken).ConfigureAwait(false);

        // Readies the controller for pairing. Remember that you have three minutes after running this command to pair.
        _ = await ProcessRunner.GetProcessOutputAsync(BcCommand, "pairable on", null, cancellationToken).ConfigureAwait(false);

        // Sets the device to re-pair automatically when it is turned on, which eliminates the need to pair all over again.
        String result = await ProcessRunner.GetProcessOutputAsync(BcCommand, $"trust {deviceAddress}", null, cancellationToken).ConfigureAwait(false);

        // Hides the controller from other Bluetooth devices. Otherwise, any device that can detect it has access to it, leaving a major security hole.
        _ = await ProcessRunner.GetProcessOutputAsync(BcCommand, "discoverable off", null, cancellationToken).ConfigureAwait(false);

        return result.Contains("Trusted: yes");
      } catch(Exception ex) {
        throw new BluetoothErrorException($"Failed to add to trust devices list: {ex.Message}");
      }
    }

    /// <summary>
    /// Displays information about a particular device.
    /// </summary>
    /// <param name="deviceAddress">The mac address of the device which info will be retrieved.</param>
    /// <param name="cancellationToken">The cancellation token.</param>
    /// <returns>
    /// Returns the device info.
    /// </returns>
    /// <exception cref="BluetoothErrorException">Failed to retrieve  info for {deviceAddress}.</exception>
    public async Task<String> DeviceInfo(String deviceAddress, CancellationToken cancellationToken = default) {
      String info = await ProcessRunner.GetProcessOutputAsync(BcCommand, $"info {deviceAddress}", null, cancellationToken).ConfigureAwait(false);

      return !String.IsNullOrEmpty(info) ? info : throw new BluetoothErrorException($"Failed to retrieve  info for {deviceAddress}");
    }
  }
}