using System;
using System.Threading.Tasks;

using Swan.Diagnostics;

using Unosquare.RaspberryIO.Abstractions;
using Unosquare.RaspberryIO.Abstractions.Native;

using Definitions = Unosquare.RaspberryIO.Abstractions.Definitions;

namespace Unosquare.WiringPi {
  /// <summary>
  /// Represents a GPIO Pin, its location and its capabilities.
  /// Full pin reference available here:
  /// http://pinout.xyz/pinout/pin31_gpio6 and  http://wiringpi.com/pins/.
  /// </summary>
  public sealed partial class GpioPin : IGpioPin {
    #region Property Backing

    private static readonly Int32[] GpioToWiringPi;

    private static readonly Int32[] GpioToWiringPiR1 = { 8, 9, -1, -1, 7, -1, -1, 11, 10, 13, 12, 14, -1, -1, 15, 16, -1, 0, 1, -1, -1, 2, 3, 4, 5, 6, -1, -1, -1, -1, -1, -1 };

    private static readonly Int32[] GpioToWiringPiR2 = { 30, 31, 8, 9, 7, 21, 22, 11, 10, 13, 12, 14, 26, 23, 15, 16, 27, 0, 1, 24, 28, 29, 3, 4, 5, 6, 25, 2, 17, 18, 19, 20 };

    private readonly Object _syncLock = new Object();
    private GpioPinDriveMode _pinMode;
    private GpioPinResistorPullMode _resistorPullMode;
    private Int32 _pwmRegister;
    private PwmMode _pwmMode = PwmMode.Balanced;
    private UInt32 _pwmRange = 1024;
    private Int32 _pwmClockDivisor = 1;
    private Int32 _softPwmValue = -1;
    private Int32 _softToneFrequency = -1;

    #endregion

    #region Constructor

    static GpioPin() => GpioToWiringPi = SystemInfo.GetBoardRevision() == BoardRevision.Rev1 ? GpioToWiringPiR1 : GpioToWiringPiR2;

    /// <summary>
    /// Initializes a new instance of the <see cref="GpioPin"/> class.
    /// </summary>
    /// <param name="bcmPinNumber">The BCM pin number.</param>
    private GpioPin(BcmPin bcmPinNumber) {
      this.BcmPin = bcmPinNumber;
      this.BcmPinNumber = (Int32)bcmPinNumber;

      this.WiringPiPinNumber = BcmToWiringPiPinNumber(bcmPinNumber);
      this.PhysicalPinNumber = Definitions.BcmToPhysicalPinNumber(SystemInfo.GetBoardRevision(), bcmPinNumber);
      this.Header = (this.BcmPinNumber >= 28 && this.BcmPinNumber <= 31) ? GpioHeader.P5 : GpioHeader.P1;
    }

    #endregion

    #region Pin Properties

    /// <inheritdoc />
    public BcmPin BcmPin {
      get;
    }

    /// <inheritdoc />
    public Int32 BcmPinNumber {
      get;
    }

    /// <inheritdoc />
    public Int32 PhysicalPinNumber {
      get;
    }

    /// <summary>
    /// Gets the WiringPi Pin number.
    /// </summary>
    public WiringPiPin WiringPiPinNumber {
      get;
    }

    /// <inheritdoc />
    public GpioHeader Header {
      get;
    }

    /// <summary>
    /// Gets the friendly name of the pin.
    /// </summary>
    public String Name {
      get; private set;
    }

    /// <summary>
    /// Gets the hardware mode capabilities of this pin.
    /// </summary>
    public PinCapability Capabilities {
      get; private set;
    }

    /// <inheritdoc />
    public Boolean Value {
      get => this.Read();
      set => this.Write(value);
    }

    #endregion

    #region Hardware-Specific Properties

    /// <inheritdoc />
    /// <exception cref="T:System.NotSupportedException">Thrown when a pin does not support the given operation mode.</exception>
    public GpioPinDriveMode PinMode {
      get => this._pinMode;

      set {
        lock(this._syncLock) {
          GpioPinDriveMode mode = value;
          if(mode == GpioPinDriveMode.GpioClock && !this.HasCapability(PinCapability.GPCLK) ||
            mode == GpioPinDriveMode.PwmOutput && !this.HasCapability(PinCapability.PWM) ||
            mode == GpioPinDriveMode.Input && !this.HasCapability(PinCapability.GP) ||
            mode == GpioPinDriveMode.Output && !this.HasCapability(PinCapability.GP)) {
            throw new NotSupportedException($"Pin {this.BcmPinNumber} '{this.Name}' does not support mode '{mode}'. Pin capabilities are limited to: {this.Capabilities}");
          }

          Native.WiringPi.PinMode(this.BcmPinNumber, (Int32)mode);
          this._pinMode = mode;
        }
      }
    }

    /// <summary>
    /// Gets the interrupt callback. Returns null if no interrupt
    /// has been registered.
    /// </summary>
    public Native.InterruptServiceRoutineCallback InterruptCallback {
      get; private set;
    }

    /// <summary>
    /// Gets the interrupt edge detection mode.
    /// </summary>
    public EdgeDetection InterruptEdgeDetection {
      get; private set;
    }

    /// <summary>
    /// Determines whether the specified capability has capability.
    /// </summary>
    /// <param name="capability">The capability.</param>
    /// <returns>
    ///   <c>true</c> if the specified capability has capability; otherwise, <c>false</c>.
    /// </returns>
    public Boolean HasCapability(PinCapability capability) => (this.Capabilities & capability) == capability;

    #endregion

    #region Hardware PWM Members

    /// <inheritdoc />
    public GpioPinResistorPullMode InputPullMode {
      get => this.PinMode == GpioPinDriveMode.Input ? this._resistorPullMode : GpioPinResistorPullMode.Off;

      set {
        lock(this._syncLock) {
          if(this.PinMode != GpioPinDriveMode.Input) {
            this._resistorPullMode = GpioPinResistorPullMode.Off;
            throw new InvalidOperationException($"Unable to set the {nameof(this.InputPullMode)} for pin {this.BcmPinNumber} because operating mode is {this.PinMode}."
              + $" Setting the {nameof(this.InputPullMode)} is only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.Input}");
          }

          Native.WiringPi.PullUpDnControl(this.BcmPinNumber, (Int32)value);
          this._resistorPullMode = value;
        }
      }
    }

    /// <summary>
    /// Gets or sets the PWM register.
    /// </summary>
    /// <value>
    /// The PWM register.
    /// </value>
    public Int32 PwmRegister {
      get => this._pwmRegister;

      set {
        lock(this._syncLock) {
          if(!this.HasCapability(PinCapability.PWM)) {
            this._pwmRegister = 0;

            throw new NotSupportedException($"Pin {this.BcmPinNumber} '{this.Name}' does not support mode '{GpioPinDriveMode.PwmOutput}'. Pin capabilities are limited to: {this.Capabilities}");
          }

          Native.WiringPi.PwmWrite(this.BcmPinNumber, value);
          this._pwmRegister = value;
        }
      }
    }

    /// <summary>
    /// The PWM generator can run in 2 modes – “balanced” and “mark:space”. The mark:space mode is traditional,
    /// however the default mode in the Pi is “balanced”.
    /// </summary>
    /// <value>
    /// The PWM mode.
    /// </value>
    /// <exception cref="InvalidOperationException">When pin mode is not set a Pwn output.</exception>
    public PwmMode PwmMode {
      get => this.PinMode == GpioPinDriveMode.PwmOutput ? this._pwmMode : PwmMode.Balanced;

      set {
        lock(this._syncLock) {
          if(!this.HasCapability(PinCapability.PWM)) {
            this._pwmMode = PwmMode.Balanced;

            throw new NotSupportedException($"Pin {this.BcmPinNumber} '{this.Name}' does not support mode '{GpioPinDriveMode.PwmOutput}'. Pin capabilities are limited to: {this.Capabilities}");
          }

          Native.WiringPi.PwmSetMode((Int32)value);
          this._pwmMode = value;
        }
      }
    }

    /// <summary>
    /// This sets the range register in the PWM generator. The default is 1024.
    /// </summary>
    /// <value>
    /// The PWM range.
    /// </value>
    /// <exception cref="InvalidOperationException">When pin mode is not set to PWM output.</exception>
    public UInt32 PwmRange {
      get => this.PinMode == GpioPinDriveMode.PwmOutput ? this._pwmRange : 0;

      set {
        lock(this._syncLock) {
          if(!this.HasCapability(PinCapability.PWM)) {
            this._pwmRange = 1024;

            throw new NotSupportedException($"Pin {this.BcmPinNumber} '{this.Name}' does not support mode '{GpioPinDriveMode.PwmOutput}'. Pin capabilities are limited to: {this.Capabilities}");
          }

          Native.WiringPi.PwmSetRange(value);
          this._pwmRange = value;
        }
      }
    }

    /// <summary>
    /// Gets or sets the PWM clock divisor.
    /// </summary>
    /// <value>
    /// The PWM clock divisor.
    /// </value>
    /// <exception cref="InvalidOperationException">When pin mode is not set to PWM output.</exception>
    public Int32 PwmClockDivisor {
      get => this.PinMode == GpioPinDriveMode.PwmOutput ? this._pwmClockDivisor : 0;

      set {
        lock(this._syncLock) {
          if(!this.HasCapability(PinCapability.PWM)) {
            this._pwmClockDivisor = 1;

            throw new NotSupportedException($"Pin {this.BcmPinNumber} '{this.Name}' does not support mode '{GpioPinDriveMode.PwmOutput}'. Pin capabilities are limited to: {this.Capabilities}");
          }

          Native.WiringPi.PwmSetClock(value);
          this._pwmClockDivisor = value;
        }
      }
    }

    #endregion

    #region Software Tone Members

    /// <summary>
    /// Gets a value indicating whether this instance is in software based tone generator mode.
    /// </summary>
    /// <value>
    /// <c>true</c> if this instance is in soft tone mode; otherwise, <c>false</c>.
    /// </value>
    public Boolean IsInSoftToneMode => this._softToneFrequency >= 0;

    /// <summary>
    /// Gets or sets the soft tone frequency. 0 to 5000 Hz is typical.
    /// </summary>
    /// <value>
    /// The soft tone frequency.
    /// </value>
    /// <exception cref="InvalidOperationException">When soft tones cannot be initialized on the pin.</exception>
    public Int32 SoftToneFrequency {
      get => this._softToneFrequency;

      set {
        lock(this._syncLock) {
          if(this.IsInSoftToneMode == false) {
            Int32 setupResult = Native.WiringPi.SoftToneCreate(this.BcmPinNumber);
            if(setupResult != 0) {
              throw new InvalidOperationException($"Unable to initialize soft tone on pin {this.BcmPinNumber}. Error Code: {setupResult}");
            }
          }

          Native.WiringPi.SoftToneWrite(this.BcmPinNumber, value);
          this._softToneFrequency = value;
        }
      }
    }

    #endregion

    #region Software PWM Members

    /// <summary>
    /// Gets a value indicating whether this pin is in software based PWM mode.
    /// </summary>
    /// <value>
    /// <c>true</c> if this instance is in soft PWM mode; otherwise, <c>false</c>.
    /// </value>
    public Boolean IsInSoftPwmMode => this._softPwmValue >= 0;

    /// <summary>
    /// Gets or sets the software PWM value on the pin.
    /// </summary>
    /// <value>
    /// The soft PWM value.
    /// </value>
    /// <exception cref="InvalidOperationException">StartSoftPwm.</exception>
    public Int32 SoftPwmValue {
      get => this._softPwmValue;

      set {
        lock(this._syncLock) {
          if(this.IsInSoftPwmMode && value >= 0) {
            Native.WiringPi.SoftPwmWrite(this.BcmPinNumber, value);
            this._softPwmValue = value;
          } else {
            throw new InvalidOperationException($"Software PWM requires a call to {nameof(StartSoftPwm)}.");
          }
        }
      }
    }

    /// <summary>
    /// Gets the software PWM range used upon starting the PWM.
    /// </summary>
    public Int32 SoftPwmRange { get; private set; } = -1;

    /// <summary>
    /// Starts the software based PWM on this pin.
    /// </summary>
    /// <param name="value">The value.</param>
    /// <param name="range">The range.</param>
    /// <exception cref="NotSupportedException">When the pin does not suppoert PWM.</exception>
    /// <exception cref="InvalidOperationException">StartSoftPwm
    /// or.</exception>
    public void StartSoftPwm(Int32 value, Int32 range) {
      lock(this._syncLock) {
        if(!this.HasCapability(PinCapability.GP)) {
          throw new NotSupportedException($"Pin {this.BcmPinNumber} does not support software PWM");
        }

        if(this.IsInSoftPwmMode) {
          throw new InvalidOperationException($"{nameof(StartSoftPwm)} has already been called.");
        }

        Int32 startResult = Native.WiringPi.SoftPwmCreate(this.BcmPinNumber, value, range);

        if(startResult == 0) {
          this._softPwmValue = value;
          this.SoftPwmRange = range;
        } else {
          throw new InvalidOperationException($"Could not start software based PWM on pin {this.BcmPinNumber}. Error code: {startResult}");
        }
      }
    }

    #endregion

    #region Output Mode (Write) Members

    /// <inheritdoc />
    public void Write(GpioPinValue value) {
      lock(this._syncLock) {
        if(this.PinMode != GpioPinDriveMode.Output) {
          throw new InvalidOperationException($"Unable to write to pin {this.BcmPinNumber} because operating mode is {this.PinMode}."
            + $" Writes are only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.Output}");
        }

        Native.WiringPi.DigitalWrite(this.BcmPinNumber, (Int32)value);
      }
    }

    /// <summary>
    /// Writes the value asynchronously.
    /// </summary>
    /// <param name="value">The value.</param>
    /// <returns>The awaitable task.</returns>
    public Task WriteAsync(GpioPinValue value) => Task.Run(() => this.Write(value));

    /// <summary>
    /// Writes the specified bit value.
    /// This method performs a digital write.
    /// </summary>
    /// <param name="value">if set to <c>true</c> [value].</param>
    public void Write(Boolean value) => this.Write(value ? GpioPinValue.High : GpioPinValue.Low);

    /// <summary>
    /// Writes the specified bit value.
    /// This method performs a digital write.
    /// </summary>
    /// <param name="value">The value.</param>
    /// <returns>
    /// The awaitable task.
    /// </returns>
    public Task WriteAsync(Boolean value) => Task.Run(() => this.Write(value));

    /// <summary>
    /// Writes the specified value. 0 for low, any other value for high
    /// This method performs a digital write.
    /// </summary>
    /// <param name="value">The value.</param>
    public void Write(Int32 value) => this.Write(value != 0 ? GpioPinValue.High : GpioPinValue.Low);

    /// <summary>
    /// Writes the specified value. 0 for low, any other value for high
    /// This method performs a digital write.
    /// </summary>
    /// <param name="value">The value.</param>
    /// <returns>The awaitable task.</returns>
    public Task WriteAsync(Int32 value) => Task.Run(() => this.Write(value));

    /// <summary>
    /// Writes the specified value as an analog level.
    /// You will need to register additional analog modules to enable this function for devices such as the Gertboard.
    /// </summary>
    /// <param name="value">The value.</param>
    public void WriteLevel(Int32 value) {
      lock(this._syncLock) {
        if(this.PinMode != GpioPinDriveMode.Output) {
          throw new InvalidOperationException($"Unable to write to pin {this.BcmPinNumber} because operating mode is {this.PinMode}."
            + $" Writes are only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.Output}");
        }

        Native.WiringPi.AnalogWrite(this.BcmPinNumber, value);
      }
    }

    /// <summary>
    /// Writes the specified value as an analog level.
    /// You will need to register additional analog modules to enable this function for devices such as the Gertboard.
    /// </summary>
    /// <param name="value">The value.</param>
    /// <returns>The awaitable task.</returns>
    public Task WriteLevelAsync(Int32 value) => Task.Run(() => this.WriteLevel(value));

    #endregion

    #region Input Mode (Read) Members

    /// <summary>
    /// Wait for specific pin status.
    /// </summary>
    /// <param name="status">status to check.</param>
    /// <param name="timeOutMillisecond">timeout to reach status.</param>
    /// <returns>true/false.</returns>
    public Boolean WaitForValue(GpioPinValue status, Int32 timeOutMillisecond) {
      if(this.PinMode != GpioPinDriveMode.Input) {
        throw new InvalidOperationException($"Unable to read from pin {this.BcmPinNumber} because operating mode is {this.PinMode}."
          + $" Reads are only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.Input}");
      }

      HighResolutionTimer hrt = new HighResolutionTimer();
      hrt.Start();
      do {
        if(this.ReadValue() == status) {
          return true;
        }
      }
      while(hrt.ElapsedMilliseconds <= timeOutMillisecond);

      return false;
    }

    /// <summary>
    /// Reads the digital value on the pin as a boolean value.
    /// </summary>
    /// <returns>The state of the pin.</returns>
    public Boolean Read() {
      lock(this._syncLock) {
        if(this.PinMode != GpioPinDriveMode.Input && this.PinMode != GpioPinDriveMode.Output) {
          throw new InvalidOperationException($"Unable to read from pin {this.BcmPinNumber} because operating mode is {this.PinMode}."
            + $" Reads are only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.Input} or {GpioPinDriveMode.Output}");
        }

        return Native.WiringPi.DigitalRead(this.BcmPinNumber) != 0;
      }
    }

    /// <summary>
    /// Reads the digital value on the pin as a boolean value.
    /// </summary>
    /// <returns>The state of the pin.</returns>
    public Task<Boolean> ReadAsync() => Task.Run(this.Read);

    /// <summary>
    /// Reads the digital value on the pin as a High or Low value.
    /// </summary>
    /// <returns>The state of the pin.</returns>
    public GpioPinValue ReadValue() => this.Read() ? GpioPinValue.High : GpioPinValue.Low;

    /// <summary>
    /// Reads the digital value on the pin as a High or Low value.
    /// </summary>
    /// <returns>The state of the pin.</returns>
    public Task<GpioPinValue> ReadValueAsync() => Task.Run(this.ReadValue);

    /// <summary>
    /// Reads the analog value on the pin.
    /// This returns the value read on the supplied analog input pin. You will need to register
    /// additional analog modules to enable this function for devices such as the Gertboard,
    /// quick2Wire analog board, etc.
    /// </summary>
    /// <returns>The analog level.</returns>
    /// <exception cref="InvalidOperationException">When the pin mode is not configured as an input.</exception>
    public Int32 ReadLevel() {
      lock(this._syncLock) {
        if(this.PinMode != GpioPinDriveMode.Input) {
          throw new InvalidOperationException($"Unable to read from pin {this.BcmPinNumber} because operating mode is {this.PinMode}."
            + $" Reads are only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.Input}");
        }

        return Native.WiringPi.AnalogRead(this.BcmPinNumber);
      }
    }

    /// <summary>
    /// Reads the analog value on the pin.
    /// This returns the value read on the supplied analog input pin. You will need to register
    /// additional analog modules to enable this function for devices such as the Gertboard,
    /// quick2Wire analog board, etc.
    /// </summary>
    /// <returns>The analog level.</returns>
    public Task<Int32> ReadLevelAsync() => Task.Run(this.ReadLevel);

    #endregion

    #region Interrupts

    /// <inheritdoc />
    /// <exception cref="ArgumentNullException">callback.</exception>
    public void RegisterInterruptCallback(EdgeDetection edgeDetection, Action callback) {
      if(callback == null) {
        throw new ArgumentNullException(nameof(callback));
      }

      if(this.PinMode != GpioPinDriveMode.Input) {
        throw new InvalidOperationException($"Unable to {nameof(RegisterInterruptCallback)} for pin {this.BcmPinNumber} because operating mode is {this.PinMode}."
          + $" Calling {nameof(RegisterInterruptCallback)} is only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.Input}");
      }

      lock(this._syncLock) {
        Native.InterruptServiceRoutineCallback isrCallback = new Native.InterruptServiceRoutineCallback(callback);
        Int32 registerResult = Native.WiringPi.WiringPiISR(this.BcmPinNumber, GetWiringPiEdgeDetection(edgeDetection), isrCallback);
        if(registerResult == 0) {
          this.InterruptEdgeDetection = edgeDetection;
          this.InterruptCallback = isrCallback;
        } else {
          HardwareException.Throw(nameof(GpioPin), nameof(RegisterInterruptCallback));
        }
      }
    }

    /// <inheritdoc />
    public void RegisterInterruptCallback(EdgeDetection edgeDetection, Action<Int32, Int32, UInt32> callback) => throw new NotSupportedException("WiringPi does only support a simple interrupt callback that has no parameters.");

    internal static WiringPiPin BcmToWiringPiPinNumber(BcmPin pin) => (WiringPiPin)GpioToWiringPi[(Int32)pin];

    private static Int32 GetWiringPiEdgeDetection(EdgeDetection edgeDetection) => GpioController.WiringPiEdgeDetectionMapping[edgeDetection];

    #endregion
  }
}