//! HID-to-UART driver for CP2110/CP2114 chipset.
//!
//! See more information [here][1].
//! [1]: https://www.silabs.com/products/interface/usb-bridges/classic-usb-bridges/device.cp2110-f01-gm

extern crate hidapi;

use std::cmp::min;
use std::default::Default;
use std::time::{Duration, Instant};

const FEATURE_REPORT_LENGTH: usize = 64;
const INTERRUPT_REPORT_LENGTH: usize = 64;

const GETSET_UART_ENABLE: u8 = 0x41; // Get Set Receive Status
const PURGE_FIFOS: u8        = 0x43; // Purge FIFOs
const GETSET_UART_CONFIG: u8 = 0x50; // Get Set UART Config

const PURGE_TRANSMIT_MASK: u8 = 0x01;
const PURGE_RECEIVE_MASK: u8  = 0x02;

type Error = hidapi::HidError;

/// The number of data bits in [UART configuration](struct.UartConfig.html).
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum DataBits {
    /// 5 data bits
    Bits5,
    /// 6 data bits
    Bits6,
    /// 7 data bits
    Bits7,
    /// 8 data bits
    Bits8,
}

impl Default for DataBits {
    fn default() -> Self {
        DataBits::Bits8
    }
}

/// The parity in [UART configuration](struct.UartConfig.html).
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum Parity {
    /// No parity.
    None,
    /// Odd parity (sum of data bits is odd).
    Odd,
    /// Even parity (sum of data bits is even).
    Even,
    /// Mark parity (always 1).
    Mark,
    /// Space parity (always 0).
    Space,
}

impl Default for Parity {
    fn default() -> Self {
        Parity::None
    }
}

/// The number of stop bits in [UART configuration](struct.UartConfig.html).
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum StopBits {
    /// 1 stop bit.
    Short,
    /// 5 data bits: 1.5 stop bits, 6-8 data bits: 2 stop bits.
    Long,
}

impl Default for StopBits {
    fn default() -> Self {
        StopBits::Short
    }
}

/// The type of flow control in [UART configuration](struct.UartConfig.html).
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum FlowControl {
    /// No flow control.
    None,
    /// RTS/CTS hardware flow control.
    RtsCts,
}

impl Default for FlowControl {
    fn default() -> Self {
        FlowControl::None
    }
}

/// UART configuration.
#[derive(Clone, PartialEq, Eq, Debug)]
pub struct UartConfig {
    pub baud_rate: u32,
    pub data_bits: DataBits,
    pub parity: Parity,
    pub stop_bits: StopBits,
    pub flow_control: FlowControl,
}

impl Default for UartConfig {
    fn default() -> Self {
        UartConfig {
            baud_rate: 9600,
            data_bits: DataBits::default(),
            parity: Parity::default(),
            stop_bits: StopBits::default(),
            flow_control: FlowControl::default(),
        }
    }
}

/// Wrapper around `HidDevice` to provide UART control.
pub struct HidUart<'a> {
    device: hidapi::HidDevice<'a>,
    read_timeout: Duration,
    write_timeout: Duration,
}

fn set_uart_enable(device: &hidapi::HidDevice, enable: bool) -> Result<(), Error> {
    let mut buf: [u8; FEATURE_REPORT_LENGTH] = [0; FEATURE_REPORT_LENGTH];

    buf[0] = GETSET_UART_ENABLE;
    if enable {
        buf[1] = 0x01;
    } else {
        buf[1] = 0x00;
    }
    device.send_feature_report(&buf)
}

impl<'a> HidUart<'a> {
    /// Returns a new instance of `HidUart` from `HidDevice`.
    ///
    /// The `HidUart` instance enables UART automatically.
    pub fn new(device: hidapi::HidDevice<'a>) -> Result<HidUart<'a>, Error> {
        let instance = HidUart {
            device: device,
            read_timeout: Duration::from_millis(1000),
            write_timeout: Duration::from_millis(1000),
        };
        instance.enable()?;
        Ok(instance)
    }

    /// Returns receiving timeout.
    pub fn read_timeout(&self) -> Duration {
        self.read_timeout
    }

    /// Set receiving timeout to `timeout` value.
    pub fn set_read_timeout(&mut self, timeout: Duration) {
        self.read_timeout = timeout;
    }

    /// Returns transmitting timeout.
    pub fn write_timeout(&self) -> Duration {
        self.write_timeout
    }

    /// Set transmitting timeout to `timeout` value.
    pub fn set_write_timeout(&mut self, timeout: Duration) {
        self.write_timeout = timeout;
    }

    /// Enable UART.
    pub fn enable(&self) -> Result<(), Error> {
        set_uart_enable(&self.device, true)
    }

    /// Disable UART.
    pub fn disable(&self) -> Result<(), Error> {
        set_uart_enable(&self.device, false)
    }

    /// Returns UART state: `true` if UART is enabled, `false` otherwise.
    pub fn is_enabled(&self) -> Result<bool, Error> {
        let mut buf: [u8; FEATURE_REPORT_LENGTH] = [0; FEATURE_REPORT_LENGTH];

        buf[0] = GETSET_UART_ENABLE;
        self.device.get_feature_report(&mut buf)?;
        if buf[1] == 0x00 {
            Ok(false)
        } else {
            Ok(true)
        }
    }

    /// Configures UART.
    pub fn set_config(&self, config: &UartConfig) -> Result<(), Error> {
        let mut buf: [u8; FEATURE_REPORT_LENGTH] = [0; FEATURE_REPORT_LENGTH];

        buf[0] = GETSET_UART_CONFIG;
        buf[1] = ((config.baud_rate >> 24) & 0xFF) as u8;
        buf[2] = ((config.baud_rate >> 16) & 0xFF) as u8;
        buf[3] = ((config.baud_rate >> 8) & 0xFF) as u8;
        buf[4] = (config.baud_rate & 0xFF) as u8;
        buf[5] =
            match config.parity {
                Parity::None => 0x00,
                Parity::Odd => 0x01,
                Parity::Even => 0x02,
                Parity::Mark => 0x03,
                Parity::Space => 0x04,
            };
        buf[6] =
            match config.flow_control {
                FlowControl::None => 0x00,
                FlowControl::RtsCts => 0x01,
            };
        buf[7] =
            match config.data_bits {
                DataBits::Bits5 => 0x00,
                DataBits::Bits6 => 0x01,
                DataBits::Bits7 => 0x02,
                DataBits::Bits8 => 0x03,
            };
        buf[8] =
            match config.stop_bits {
                StopBits::Short => 0x00,
                StopBits::Long => 0x01,
            };

        self.device.send_feature_report(&buf)?;
        Ok(())
    }

    /// Returns current UART configuration.
    pub fn get_config(&self) -> Result<UartConfig, Error> {
        let mut buf: [u8; FEATURE_REPORT_LENGTH] = [0; FEATURE_REPORT_LENGTH];

        buf[0] = GETSET_UART_CONFIG;
        self.device.get_feature_report(&mut buf)?;

        let baud_rate: u32 = (buf[1] as u32) << 24 | (buf[2] as u32) << 16 | (buf[3] as u32) << 8 | buf[4] as u32;
        let parity =
            match buf[5] {
                0x00 => Ok(Parity::None),
                0x01 => Ok(Parity::Odd),
                0x02 => Ok(Parity::Even),
                0x03 => Ok(Parity::Mark),
                0x04 => Ok(Parity::Space),
                _ => Err("Unknown parity mode"),
            }?;
        let flow_control =
            match buf[6] {
                0x00 => Ok(FlowControl::None),
                0x01 => Ok(FlowControl::RtsCts),
                _ => Err("Unknown flow control mode"),
            }?;
        let data_bits =
            match buf[7] {
                0x00 => Ok(DataBits::Bits5),
                0x01 => Ok(DataBits::Bits6),
                0x02 => Ok(DataBits::Bits7),
                0x03 => Ok(DataBits::Bits8),
                _ => Err("Unknown data bits mode"),
            }?;
        let stop_bits =
            match buf[8] {
                0x00 => Ok(StopBits::Short),
                0x01 => Ok(StopBits::Long),
                _ => Err("Unknown stop bits mode"),
            }?;
        let config = UartConfig {
            baud_rate,
            parity,
            flow_control,
            data_bits,
            stop_bits,
        };

        Ok(config)
    }

    /// Empties receiving and/or transmitting FIFO buffers.
    ///
    /// Flushes receiving FIFO buffer if `rx` is `true`.
    ///
    /// Flushes transmitting FIFO buffer if `tx` is `true`.
    pub fn flush_fifos(&self, rx: bool, tx: bool) -> Result<(), Error> {
        let mut buf: [u8; FEATURE_REPORT_LENGTH] = [0; FEATURE_REPORT_LENGTH];

        buf[0] = PURGE_FIFOS;
        if rx {
            buf[1] = buf[1] | PURGE_RECEIVE_MASK;
        }
        if tx {
            buf[1] = buf[1] | PURGE_TRANSMIT_MASK;
        }
        self.device.send_feature_report(&buf)?;

        Ok(())
    }

    /// Transmit `data`.
    pub fn write(&self, data: &[u8]) -> Result<(), Error> {
        let mut buf: [u8; INTERRUPT_REPORT_LENGTH];

        let start_time = Instant::now();
        for chunk in data.chunks(INTERRUPT_REPORT_LENGTH - 1) {
            if start_time.elapsed() > self.write_timeout {
                return Err("Transmit timed out");
            }
            buf = [0; INTERRUPT_REPORT_LENGTH];
            buf[0] = chunk.len() as u8;
            buf[1..chunk.len()+1].copy_from_slice(chunk);
            self.device.write(&buf)?;
        }

        Ok(())
    }

    /// Receive `data` and returns a number of read bytes.
    pub fn read(&self, data: &mut [u8]) -> Result<usize, Error> {
        let mut buf: [u8; INTERRUPT_REPORT_LENGTH];
        let start_time = Instant::now();
        let mut num_bytes_read = 0;
        while start_time.elapsed() < self.read_timeout {
            let data_free = data.len() - num_bytes_read;
            if data_free > 0 {
                buf = [0; INTERRUPT_REPORT_LENGTH];
                let buf_size = min(data_free, INTERRUPT_REPORT_LENGTH - 1) + 1;
                if  self.device.read_timeout(&mut buf[0..buf_size], 1)? > 0 {
                    let report_len: usize = buf[0] as usize;
                    data[num_bytes_read..(num_bytes_read + report_len)].copy_from_slice(&buf[1..(report_len + 1)]);
                    num_bytes_read = num_bytes_read + report_len;
                } else {
                    continue;
                }
            } else {
                break;
            }
        }
        Ok(num_bytes_read)
    }
}