extern crate bytes;
extern crate serial;
#[macro_use]
extern crate log;

use bytes::{BufMut, BytesMut};
use serial::prelude::*;
use std::io;
use std::io::{Error, ErrorKind};
use std::time::{Duration, Instant};

/// type alias for relay vecs
pub type RelayIndex = Vec<u8>;
/// type alias for card index vecs
pub type CardIndex = Vec<u8>;

/// Provides access to serial port
pub struct Relay8x {
    // address of the first card, succeding card has +1 and so on
    start_address: u8,
    // struct containing the serial port settings and stuff
    port: Box<SerialPort>,
}

/// enum for all possbile commands
#[derive(Debug)]
pub enum Relay8xCmdSet {
    // initialisation command
    Init,
    // switch relays on or off
    Set,
    // toggle relays
    Toggle,
    // reset (switch off) relays
    Reset,
}

impl Relay8xCmdSet {
    /// based on command, address and card, returns the command frame for the relay card
    pub fn encode(
        self,
        bytes: &mut BytesMut,
        start_address: u8,
        card: Option<u8>,
        relays: Option<&RelayIndex>,
    ) -> io::Result<()> {
        match self {
            Relay8xCmdSet::Init => {
                let cmd = 1; // init command: 1
                bytes.put_u8(cmd); // first byte: command
                bytes.put_u8(start_address); // second byte: address of card
                bytes.put_u8(0); // third: dont care
                let checksum = Relay8xCmdSet::checksummed(&bytes[..]); // fourth: XOR
                bytes.put_u8(checksum);
                debug!(
                    "Init command: {:02x} {:02x} {:02x} {:02x}",
                    &bytes[0], &bytes[1], &bytes[2], &bytes[3]
                );
            }
            Relay8xCmdSet::Set => {
                let cmd = 6; // command for turning on: 6
                bytes.put_u8(cmd); // first byte: command
                let address = Relay8xCmdSet::addressed(start_address, card);
                bytes.put_u8(address); // second byte: address of card
                let relay_bin = Relay8xCmdSet::relay_as_u8(relays.unwrap());
                debug!("Relays to set: {:08b}", relay_bin);
                bytes.put_u8(relay_bin); // third byte: data of relays
                let checksum = Relay8xCmdSet::checksummed(&bytes[..]); // fourth: XOR
                bytes.put_u8(checksum);
                debug!(
                    "Set command: {:02x} {:02x} {:02x} {:02x}",
                    &bytes[0], &bytes[1], &bytes[2], &bytes[3]
                );
            }
            Relay8xCmdSet::Toggle => {
                let cmd = 8; // command for turning on
                bytes.put_u8(cmd); // first byte: command
                let address = Relay8xCmdSet::addressed(start_address, card);
                bytes.put_u8(address); // second byte: address of card
                let relay_bin = Relay8xCmdSet::relay_as_u8(relays.unwrap());
                debug!("Relays to set: {:08b}", relay_bin);
                bytes.put_u8(relay_bin); // third byte: data of relays
                let checksum = Relay8xCmdSet::checksummed(&bytes[..]); // fourth: XOR
                bytes.put_u8(checksum);
                debug!(
                    "Toggle command: {:02x} {:02x} {:02x} {:02x}",
                    &bytes[0], &bytes[1], &bytes[2], &bytes[3]
                );
            }
            Relay8xCmdSet::Reset => {
                let cmd = 7; // command for turning on
                bytes.put_u8(cmd);
                let address = Relay8xCmdSet::addressed(start_address, card);
                bytes.put_u8(address); // second byte: address of card
                let relay_bin = Relay8xCmdSet::relay_as_u8(relays.unwrap());
                debug!("Relays to set: {:08b}", relay_bin);
                bytes.put_u8(relay_bin); // third byte: data of relays
                let checksum = Relay8xCmdSet::checksummed(&bytes[..]); // fourth: XOR
                bytes.put_u8(checksum);
                debug!(
                    "Reset command: {:02x} {:02x} {:02x} {:02x}",
                    &bytes[0], &bytes[1], &bytes[2], &bytes[3]
                );
            }
        }
        Ok(())
    }

    /// calculates the data byte based on the relays to be switchted
    fn relay_as_u8(vec: &RelayIndex) -> u8 {
        let mut relay_bin = 0b00000000;
        vec.iter().rev().for_each(|x| {
            relay_bin |= (1 << (x - 1)) as u8; // shift ones to the specified relays
        });
        relay_bin
    }

    /// calculates the XOR checksum for the fourth  byte ot the command
    fn checksummed(x: &[u8]) -> u8 {
        x.iter().fold(0u8, |checksum, elem| checksum ^ elem)
    }

    /// calculates the address for each card based on starting address of first card
    fn addressed(address: u8, card: Option<u8>) -> u8 {
        address + card.unwrap_or(1) - 1
    }
}

impl Relay8x {
    /// constructor for a new Relay Card
    pub fn new(device_name: &str, address: u8) -> Result<Self, io::Error> {
        let port = ::serial::open(device_name)?;
        Ok(Self {
            port: Box::new(port),
            start_address: address,
        })
    }

    /// initialise device with correct params
    ///
    /// sets device address, function can be used to re-set it
    pub fn configure_device(&mut self) -> io::Result<BytesMut> {
        let port = &mut self.port;
        // configure interface with its params, see doc of relay card
        port.reconfigure(&|settings| {
            settings.set_baud_rate(::serial::Baud19200)?;
            settings.set_char_size(::serial::Bits8);
            settings.set_parity(::serial::ParityNone);
            settings.set_stop_bits(::serial::Stop1);
            settings.set_flow_control(::serial::FlowNone);
            Ok(())
        })?;

        port.set_timeout(Duration::from_millis(1000))?;

        // init relay card
        let mut cmd = BytesMut::with_capacity(4);
        Relay8xCmdSet::encode(
            Relay8xCmdSet::Init,
            &mut cmd,
            self.start_address,
            None,
            None,
        )?;

        port.write(&cmd[..])?;
        debug!("Wrote init message..");
        let mut resp = BytesMut::new();
        let now = Instant::now();
        // read until last card has responded
        loop {
            resp.put_u32_le(0);
            port.read(&mut resp[..])?;
            debug!(
                "Response init: {:02x} {:02x} {:02x} {:02x}",
                &resp[0], &resp[1], &resp[2], &resp[3]
            );
            if *resp.first().unwrap() == self.start_address {
                break;
            } else if now.elapsed().as_secs() > 30 {
                return Err(Error::new(
                    ErrorKind::Other,
                    "Initialisation took to long..",
                ));
            }
        }

        Ok(cmd)
    }

    /// switch arbitrary relays on
    ///
    /// - numbers: Vector containing all relay numbers (1..8)
    /// - state: true for switching on, false for off
    pub fn set_relays(&mut self, cards: CardIndex, numbers: RelayIndex) -> io::Result<BytesMut> {
        let port = &mut self.port;
        let start_address = self.start_address;
        // with capacity makes it only working for current relay card, but it ensures the
        // right length
        let mut cmd = BytesMut::with_capacity(4);

        for &card in cards.iter() {
            Relay8xCmdSet::encode(
                Relay8xCmdSet::Set,
                &mut cmd,
                start_address,
                Some(card),
                Some(&numbers),
            )?;
            port.write(&cmd[..])?;
            let sent_cmd = cmd.clone();
            port.read(&mut cmd[..])?;
            debug!(
                "Set Relays response: {:02x} {:02x} {:02x} {:02x}",
                &cmd[0], &cmd[1], &cmd[2], &cmd[3]
            );
            Relay8x::check_response(&cmd, &sent_cmd)?;
            cmd.clear();
        }
        Ok(cmd)
    }

    /// switch arbitrary relays off
    ///
    /// - numbers: Vector containing all relay numbers (1..8)
    /// - state: true for switching on, false for off
    pub fn reset_relays(&mut self, cards: CardIndex, numbers: RelayIndex) -> io::Result<BytesMut> {
        let port = &mut self.port;
        let start_address = self.start_address;
        // with capacity makes it only working for current relay card, but it ensures the
        // right length
        let mut cmd = BytesMut::with_capacity(4);

        for &card in cards.iter() {
            Relay8xCmdSet::encode(
                Relay8xCmdSet::Reset,
                &mut cmd,
                start_address,
                Some(card),
                Some(&numbers),
            )?;
            port.write(&cmd[..])?;
            let sent_cmd = cmd.clone();
            port.read(&mut cmd[..])?;
            debug!(
                "Reset Relays response: {:02x} {:02x} {:02x} {:02x}",
                &cmd[0], &cmd[1], &cmd[2], &cmd[3]
            );
            Relay8x::check_response(&cmd, &sent_cmd)?;
            cmd.clear();
        }
        Ok(cmd)
    }

    /// toggle aribtrary relays
    ///
    /// numbers: vector containing all relay numbers (1..8)
    pub fn toggle_relays(&mut self, cards: CardIndex, numbers: RelayIndex) -> io::Result<BytesMut> {
        let port = &mut self.port;
        let start_address = self.start_address;
        // with capacity makes it only working for current relay card, but it ensures the
        // right length
        let mut cmd = BytesMut::with_capacity(4);

        for &card in cards.iter() {
            Relay8xCmdSet::encode(
                Relay8xCmdSet::Toggle,
                &mut cmd,
                start_address,
                Some(card),
                Some(&numbers),
            )?;
            port.write(&cmd[..])?;
            let sent_cmd = cmd.clone();
            port.read(&mut cmd[..])?;
            debug!(
                "Toggle Relays response: {:02x} {:02x} {:02x} {:02x}",
                &cmd[0], &cmd[1], &cmd[2], &cmd[3]
            );
            Relay8x::check_response(&cmd, &sent_cmd)?;
            cmd.clear();
        }
        Ok(cmd)
    }

    /// simple response checker of recieved frame
    fn check_response(msg: &BytesMut, sent_msg: &BytesMut) -> io::Result<()> {
        // check first byte
        let checker_byte = sent_msg.get(0).unwrap_or(&1);
        let checked_bytes = msg.get(0).unwrap_or(&1);
        if *checked_bytes != !checker_byte {
            return Err(Error::new(
                ErrorKind::Other,
                format!(
                    "Bad first byte: is {}, should be {}",
                    checked_bytes, !checker_byte
                ),
            ));
        }
        // second byte: adress
        let resp_addr = msg.get(1).unwrap_or(&0);
        let sent_addr = sent_msg.get(1).unwrap_or(&1);
        // weird error, it prints the same addresses but says there are not equal...
        if resp_addr != sent_addr && *sent_addr != 0u8 {
            return Err(Error::new(
                ErrorKind::Other,
                format!(
                    "Wrong Adress: 0x{:02x} instead of 0x{:02x}",
                    resp_addr, sent_addr
                ),
            ));
        }
        // last byte: XOR
        if *msg.get(3).unwrap_or(&0)
            != (*msg.get(0).unwrap_or(&1) ^ *msg.get(1).unwrap_or(&0) ^ *msg.get(2).unwrap_or(&0))
        {
            return Err(Error::new(ErrorKind::Other, "XOR in last byte is wrong"));
        }
        debug!("Check ok");
        Ok(())
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn connect_to_card() {
        let mut relay =
            Relay8x::new(String::from("/dev/ttyUSB0"), 1).expect("Failed to connect to device");
        let init_response = relay.init_device().expect("Failed to init device");
        let expected_res = BytesMut::from(vec![
            254,
            relay.start_address,
            11,
            254 ^ relay.start_address ^ 11,
        ]);
        assert_eq!(init_response, expected_res);
    }

}