using Unosquare.RaspberryIO.Native;
using Unosquare.Swan;
using System;
using System.Linq;
using System.Threading.Tasks;

namespace Unosquare.RaspberryIO.Gpio {
  /// <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 {
    #region Property Backing

    private readonly Object _syncLock = new Object();
    private GpioPinDriveMode m_PinMode;
    private GpioPinResistorPullMode m_ResistorPullMode;
    private Int32 m_PwmRegister;
    private PwmMode m_PwmMode = PwmMode.Balanced;
    private UInt32 m_PwmRange = 1024;
    private Int32 m_PwmClockDivisor = 1;
    private Int32 m_SoftPwmValue = -1;
    private Int32 m_SoftToneFrequency = -1;

    #endregion

    #region Constructor

    /// <summary>
    /// Initializes a new instance of the <see cref="GpioPin"/> class.
    /// </summary>
    /// <param name="wiringPiPinNumber">The wiring pi pin number.</param>
    /// <param name="headerPinNumber">The header pin number.</param>
    private GpioPin(WiringPiPin wiringPiPinNumber, Int32 headerPinNumber) {
      this.PinNumber = (Int32)wiringPiPinNumber;
      this.WiringPiPinNumber = wiringPiPinNumber;
      this.BcmPinNumber = GpioController.WiringPiToBcmPinNumber((Int32)wiringPiPinNumber);
      this.HeaderPinNumber = headerPinNumber;
      this.Header = (this.PinNumber >= 17 && this.PinNumber <= 20) ? GpioHeader.P5 : GpioHeader.P1;
    }

    #endregion

    #region Pin Properties

    /// <summary>
    /// Gets or sets the Wiring Pi pin number as an integer.
    /// </summary>
    public Int32 PinNumber {
      get;
    }

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

    /// <summary>
    /// Gets the BCM chip (hardware) pin number.
    /// </summary>
    public Int32 BcmPinNumber {
      get;
    }

    /// <summary>
    /// Gets or the physical header (physical board) pin number.
    /// </summary>
    public Int32 HeaderPinNumber {
      get;
    }

    /// <summary>
    /// Gets the pin's header (physical board) location.
    /// </summary>
    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;
    }

    #endregion

    #region Hardware-Specific Properties

    /// <summary>
    /// Gets or sets the pin operating mode.
    /// </summary>
    /// <value>
    /// The pin mode.
    /// </value>
    /// <exception cref="NotSupportedException">Thrown when a pin does not support the given operation mode.</exception>
    public GpioPinDriveMode PinMode {
      get => this.m_PinMode;

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

          WiringPi.PinMode(this.PinNumber, (Int32)mode);
          this.m_PinMode = mode;
        }
      }
    }

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

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

    #endregion

    #region Hardware PWM Members

    /// <summary>
    /// This sets or gets the pull-up or pull-down resistor mode on the pin, which should be set as an input.
    /// Unlike the Arduino, the BCM2835 has both pull-up an down internal resistors.
    /// The parameter pud should be; PUD_OFF, (no pull up/down), PUD_DOWN (pull to ground) or PUD_UP (pull to 3.3v)
    /// The internal pull up/down resistors have a value of approximately 50KΩ on the Raspberry Pi.
    /// </summary>
    public GpioPinResistorPullMode InputPullMode {
      get => this.PinMode == GpioPinDriveMode.Input ? this.m_ResistorPullMode : GpioPinResistorPullMode.Off;

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

          WiringPi.PullUpDnControl(this.PinNumber, (Int32)value);
          this.m_ResistorPullMode = value;
        }
      }
    }

    /// <summary>
    /// Gets or sets the PWM register. Values should be between 0 and 1024
    /// </summary>
    /// <value>
    /// The PWM register.
    /// </value>
    public Int32 PwmRegister {
      get => this.m_PwmRegister;

      set {
        lock(this._syncLock) {
          if(this.PinMode != GpioPinDriveMode.PwmOutput) {
            this.m_PwmRegister = 0;

            throw new InvalidOperationException(
                $"Unable to write PWM register for pin {this.PinNumber} because operating mode is {this.PinMode}."
                + $" Writing the PWM register is only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.PwmOutput}");
          }

          Int32 val = value.Clamp(0, 1024);

          WiringPi.PwmWrite(this.PinNumber, val);
          this.m_PwmRegister = val;
        }
      }
    }

    /// <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.m_PwmMode : PwmMode.Balanced;

      set {
        lock(this._syncLock) {
          if(this.PinMode != GpioPinDriveMode.PwmOutput) {
            this.m_PwmMode = PwmMode.Balanced;

            throw new InvalidOperationException(
                $"Unable to set PWM mode for pin {this.PinNumber} because operating mode is {this.PinMode}."
                + $" Setting the PWM mode is only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.PwmOutput}");
          }

          WiringPi.PwmSetMode((Int32)value);
          this.m_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.m_PwmRange : 0;

      set {
        lock(this._syncLock) {
          if(this.PinMode != GpioPinDriveMode.PwmOutput) {
            this.m_PwmRange = 1024;

            throw new InvalidOperationException(
                $"Unable to set PWM range for pin {this.PinNumber} because operating mode is {this.PinMode}."
                + $" Setting the PWM range is only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.PwmOutput}");
          }

          WiringPi.PwmSetRange(value);
          this.m_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.m_PwmClockDivisor : 0;

      set {
        lock(this._syncLock) {
          if(this.PinMode != GpioPinDriveMode.PwmOutput) {
            this.m_PwmClockDivisor = 1;

            throw new InvalidOperationException(
                $"Unable to set PWM range for pin {this.PinNumber} because operating mode is {this.PinMode}."
                + $" Setting the PWM range is only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.PwmOutput}");
          }

          WiringPi.PwmSetClock(value);
          this.m_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.m_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.m_SoftToneFrequency;

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

          WiringPi.SoftToneWrite(this.PinNumber, value);
          this.m_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.m_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.m_SoftPwmValue;

      set {
        lock(this._syncLock) {
          if(this.IsInSoftPwmMode && value >= 0) {
            WiringPi.SoftPwmWrite(this.PinNumber, value);
            this.m_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.Capabilities.Contains(PinCapability.GP) == false) {
          throw new NotSupportedException($"Pin {this.PinNumber} does not support software PWM");
        }

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

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

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

    #endregion

    #region Output Mode (Write) Members

    /// <summary>
    /// Writes the specified pin value.
    /// This method performs a digital write
    /// </summary>
    /// <param name="value">The value.</param>
    public void Write(GpioPinValue value) {
      lock(this._syncLock) {
        if(this.PinMode != GpioPinDriveMode.Output) {
          throw new InvalidOperationException(
              $"Unable to write to pin {this.PinNumber} because operating mode is {this.PinMode}."
              + $" Writes are only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.Output}");
        }

        WiringPi.DigitalWrite(this.PinNumber, (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.PinNumber} because operating mode is {this.PinMode}."
              + $" Writes are only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.Output}");
        }

        WiringPi.AnalogWrite(this.PinNumber, 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.PinNumber} 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;
        }

        Pi.Timing.SleepMicroseconds(101); // 101 uses nanosleep as opposed to a loop.
      }
      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.PinNumber} because operating mode is {this.PinMode}."
              + $" Reads are only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.Input} or {GpioPinDriveMode.Output}");
        }

        return WiringPi.DigitalRead(this.PinNumber) != 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.PinNumber} because operating mode is {this.PinMode}."
              + $" Reads are only allowed if {nameof(this.PinMode)} is set to {GpioPinDriveMode.Input}");
        }

        return WiringPi.AnalogRead(this.PinNumber);
      }
    }

    /// <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

    /// <summary>
    /// Registers the interrupt callback on the pin. Pin mode has to be set to Input.
    /// </summary>
    /// <param name="edgeDetection">The edge detection.</param>
    /// <param name="callback">The callback.</param>
    /// <exception cref="ArgumentException">callback</exception>
    /// <exception cref="InvalidOperationException">
    /// An interrupt callback was already registered.
    /// or
    /// RegisterInterruptCallback
    /// </exception>
    public void RegisterInterruptCallback(EdgeDetection edgeDetection, InterruptServiceRoutineCallback callback) {
      if(callback == null) {
        throw new ArgumentException($"{nameof(callback)} cannot be null");
      }

      if(this.InterruptCallback != null) {
        throw new InvalidOperationException("An interrupt callback was already registered.");
      }

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

      lock(this._syncLock) {
        Int32 registerResult = WiringPi.WiringPiISR(this.PinNumber, (Int32)edgeDetection, callback);
        if(registerResult == 0) {
          this.InterruptEdgeDetection = edgeDetection;
          this.InterruptCallback = callback;
        } else {
          HardwareException.Throw(nameof(GpioPin), nameof(RegisterInterruptCallback));
        }
      }
    }

    #endregion
  }
}