using System;
using System.Globalization;
using System.IO;

using Swan;

namespace Unosquare.RaspberryIO.Computer {
  /// <summary>
  /// The Official Raspberry Pi 7-inch touch display from the foundation
  /// Some docs available here:
  /// http://forums.pimoroni.com/t/official-7-raspberry-pi-touch-screen-faq/959.
  /// </summary>
  public class DsiDisplay : SingletonBase<DsiDisplay> {
    private const String BacklightFilename = "/sys/class/backlight/rpi_backlight/bl_power";
    private const String BrightnessFilename = "/sys/class/backlight/rpi_backlight/brightness";

    /// <summary>
    /// Prevents a default instance of the <see cref="DsiDisplay"/> class from being created.
    /// </summary>
    private DsiDisplay() {
      // placeholder
    }

    /// <summary>
    /// Gets a value indicating whether the Pi Foundation Display files are present.
    /// </summary>
    /// <value>
    /// <c>true</c> if this instance is present; otherwise, <c>false</c>.
    /// </value>
    public Boolean IsPresent => File.Exists(BrightnessFilename);

    /// <summary>
    /// Gets or sets the brightness of the DSI display via filesystem.
    /// </summary>
    /// <value>
    /// The brightness.
    /// </value>
    public Byte Brightness {
      get => this.IsPresent ? Byte.TryParse(File.ReadAllText(BrightnessFilename).Trim(), out Byte brightness) ? brightness : (Byte)0 : (Byte)0;
      set {
        if(this.IsPresent) {
          File.WriteAllText(BrightnessFilename, value.ToString(CultureInfo.InvariantCulture));
        }
      }
    }

    /// <summary>
    /// Gets or sets a value indicating whether the backlight of the DSI display on.
    /// This operation is performed via the file system.
    /// </summary>
    /// <value>
    /// <c>true</c> if this instance is backlight on; otherwise, <c>false</c>.
    /// </value>
    public Boolean IsBacklightOn {
      get => this.IsPresent && Int32.TryParse(File.ReadAllText(BacklightFilename).Trim(), out Int32 value) && value == 0;
      set {
        if(this.IsPresent) {
          File.WriteAllText(BacklightFilename, value ? "0" : "1");
        }
      }
    }
  }
}