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

namespace Unosquare.RaspberryIO.Gpio {
  /// <summary>
  /// Represents a device on the I2C Bus
  /// </summary>
  public class I2CDevice {
    private readonly Object _syncLock = new Object();

    /// <summary>
    /// Initializes a new instance of the <see cref="I2CDevice"/> class.
    /// </summary>
    /// <param name="deviceId">The device identifier.</param>
    /// <param name="fileDescriptor">The file descriptor.</param>
    internal I2CDevice(Int32 deviceId, Int32 fileDescriptor) {
      this.DeviceId = deviceId;
      this.FileDescriptor = fileDescriptor;
    }

    /// <summary>
    /// Gets the device identifier.
    /// </summary>
    /// <value>
    /// The device identifier.
    /// </value>
    public Int32 DeviceId {
      get;
    }

    /// <summary>
    /// Gets the standard POSIX file descriptor.
    /// </summary>
    /// <value>
    /// The file descriptor.
    /// </value>
    public Int32 FileDescriptor {
      get;
    }

    /// <summary>
    /// Reads a byte from the specified file descriptor
    /// </summary>
    /// <returns>The byte from device</returns>
    public Byte Read() {
      lock(this._syncLock) {
        Int32 result = WiringPi.WiringPiI2CRead(this.FileDescriptor);
        if(result < 0) {
          HardwareException.Throw(nameof(I2CDevice), nameof(Read));
        }

        return (Byte)result;
      }
    }

    /// <summary>
    /// Reads a byte from the specified file descriptor
    /// </summary>
    /// <returns>The byte from device</returns>
    public Task<Byte> ReadAsync() => Task.Run(() => this.Read());

    /// <summary>
    /// Reads a buffer of the specified length, one byte at a time
    /// </summary>
    /// <param name="length">The length.</param>
    /// <returns>The byte array from device</returns>
    public Byte[] Read(Int32 length) {
      lock(this._syncLock) {
        Byte[] buffer = new Byte[length];
        for(Int32 i = 0; i < length; i++) {
          Int32 result = WiringPi.WiringPiI2CRead(this.FileDescriptor);
          if(result < 0) {
            HardwareException.Throw(nameof(I2CDevice), nameof(Read));
          }

          buffer[i] = (Byte)result;
        }

        return buffer;
      }
    }

    /// <summary>
    /// Reads a buffer of the specified length, one byte at a time
    /// </summary>
    /// <param name="length">The length.</param>
    /// <returns>The byte array from device</returns>
    public Task<Byte[]> ReadAsync(Int32 length) => Task.Run(() => this.Read(length));

    /// <summary>
    /// Writes a byte of data the specified file descriptor.
    /// </summary>
    /// <param name="data">The data.</param>
    public void Write(Byte data) {
      lock(this._syncLock) {
        Int32 result = WiringPi.WiringPiI2CWrite(this.FileDescriptor, data);
        if(result < 0) {
          HardwareException.Throw(nameof(I2CDevice), nameof(Write));
        }
      }
    }

    /// <summary>
    /// Writes a byte of data the specified file descriptor.
    /// </summary>
    /// <param name="data">The data.</param>
    /// <returns>The awaitable task</returns>
    public Task WriteAsync(Byte data) => Task.Run(() => this.Write(data));

    /// <summary>
    /// Writes a set of bytes to the specified file descriptor.
    /// </summary>
    /// <param name="data">The data.</param>
    public void Write(Byte[] data) {
      lock(this._syncLock) {
        foreach(Byte b in data) {
          Int32 result = WiringPi.WiringPiI2CWrite(this.FileDescriptor, b);
          if(result < 0) {
            HardwareException.Throw(nameof(I2CDevice), nameof(Write));
          }
        }
      }
    }

    /// <summary>
    /// Writes a set of bytes to the specified file descriptor.
    /// </summary>
    /// <param name="data">The data.</param>
    /// <returns>The awaitable task</returns>
    public Task WriteAsync(Byte[] data) => Task.Run(() => this.Write(data));

    /// <summary>
    /// These write an 8 or 16-bit data value into the device register indicated.
    /// </summary>
    /// <param name="address">The register.</param>
    /// <param name="data">The data.</param>
    public void WriteAddressByte(Int32 address, Byte data) {
      lock(this._syncLock) {
        Int32 result = WiringPi.WiringPiI2CWriteReg8(this.FileDescriptor, address, data);
        if(result < 0) {
          HardwareException.Throw(nameof(I2CDevice), nameof(WriteAddressByte));
        }
      }
    }

    /// <summary>
    /// These write an 8 or 16-bit data value into the device register indicated.
    /// </summary>
    /// <param name="address">The register.</param>
    /// <param name="data">The data.</param>
    public void WriteAddressWord(Int32 address, UInt16 data) {
      lock(this._syncLock) {
        Int32 result = WiringPi.WiringPiI2CWriteReg16(this.FileDescriptor, address, data);
        if(result < 0) {
          HardwareException.Throw(nameof(I2CDevice), nameof(WriteAddressWord));
        }
      }
    }

    /// <summary>
    /// These read an 8 or 16-bit value from the device register indicated.
    /// </summary>
    /// <param name="address">The register.</param>
    /// <returns>The address byte from device</returns>
    public Byte ReadAddressByte(Int32 address) {
      lock(this._syncLock) {
        Int32 result = WiringPi.WiringPiI2CReadReg8(this.FileDescriptor, address);
        if(result < 0) {
          HardwareException.Throw(nameof(I2CDevice), nameof(ReadAddressByte));
        }

        return (Byte)result;
      }
    }

    /// <summary>
    /// These read an 8 or 16-bit value from the device register indicated.
    /// </summary>
    /// <param name="address">The register.</param>
    /// <returns>The address word from device</returns>
    public UInt16 ReadAddressWord(Int32 address) {
      lock(this._syncLock) {
        Int32 result = WiringPi.WiringPiI2CReadReg16(this.FileDescriptor, address);
        if(result < 0) {
          HardwareException.Throw(nameof(I2CDevice), nameof(ReadAddressWord));
        }

        return Convert.ToUInt16(result);
      }
    }
  }
}