r701/src/r701.rs

use crate::RecordIterator;
use std::io::{BufRead, BufReader, Error, ErrorKind::InvalidData, Result, Write};
use std::net::{TcpStream, ToSocketAddrs};

#[derive(Debug)]
pub struct R701 {
    tcp_stream: TcpStream,
    sequence_number: u16,
}

impl R701 {
    pub fn connect(connection_info: impl ToSocketAddrs) -> Result<Self> {
        // Create a new R701 struct
        let mut new = Self {
            tcp_stream: TcpStream::connect(connection_info)?,
            sequence_number: 0,
        };

        // Try to ping the endpoint
        new.ping()?;
        Ok(new)
    }

    pub fn request(&mut self, payload: &[u8; 12]) -> Result<Vec<u8>> {
        // Create a blank request
        let mut request = [0x55, 0xaa, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];

        // Insert the payload
        request[2..14].clone_from_slice(payload);

        // Insert the sequence number
        request[14..].clone_from_slice(&self.sequence_number.to_le_bytes());
        self.sequence_number += 1;

        // Send the request
        self.tcp_stream.write_all(&request)?;

        // Create a buffer and return the response
        let mut buffer = BufReader::new(&self.tcp_stream);
        Ok(buffer.fill_buf()?.to_vec())
    }

    pub fn ping(&mut self) -> Result<()> {
        // Create a request with a payload of `01 80 00 00 00 00 00 00 00 00 00
        // 00` and get the response
        let response = self.request(&[0x01, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0])?;

        // If the response is not `aa 55 01 01 00 00 00 00 00 00` then return an
        // error
        if response != [0xaa, 0x55, 0x01, 0x01, 0, 0, 0, 0, 0, 0] {
            return Err(Error::new(InvalidData, "Malformed response"));
        }

        Ok(())
    }

    pub fn get_name(&mut self, id: u32) -> Result<Option<String>> {
        // Create a request with a payload of `01 c7 xx xx xx xx 00 00 00 00 14
        // 00`, where `xx xx xx xx` is the employee ID in little endian
        let mut request = [0x01, 0xc7, 0, 0, 0, 0, 0, 0, 0, 0, 0x14, 0];
        request[2..6].clone_from_slice(&id.to_le_bytes());

        // Get the response
        let response = self.request(&request)?;

        // If the response length is right but the header is `01 00 00 00 00 00
        // 00 00` then the request is been succesful but the name was not found
        if response.len() == 34
            && response[..12] == [0xaa, 0x55, 0x01, 0, 0, 0, 0, 0, 0, 0, 0x55, 0xaa]
        {
            return Ok(None);
        }

        // If one between the response length or the response header is wrong
        // return an error
        if response.len() != 34
            || response[..12] != [0xaa, 0x55, 0x01, 0x01, 0, 0, 0, 0, 0, 0, 0x55, 0xaa]
        {
            return Err(Error::new(InvalidData, "Malformed response"));
        }

        // Get the name as a UTF-8 string and delete the `\0` at the end
        let name = String::from_utf8_lossy(&response[12..22])
            .trim_end_matches('\0')
            .to_string();

        // Return None if the name is empty, else return the name wrapped into a
        // Some
        Ok(Some(name).filter(|name| !name.is_empty()))
    }

    pub fn get_total_record_count(&mut self) -> Result<u16> {
        // Create a request with a payload of `01 b4 08 00 00 00 00 00 ff ff 00
        // 00` and get the response
        let response = self.request(&[0x01, 0xb4, 0x08, 0, 0, 0, 0, 0, 0xff, 0xff, 0, 0])?;

        // If one between the response length or the response header is wrong
        // return an error
        if response.len() != 10
            || response[..4] != [0xaa, 0x55, 0x01, 0x01]
            || response[6..] != [0u8; 4]
        {
            return Err(Error::new(InvalidData, "Malformed response"));
        }

        // Convert the payload into a u16 and return it
        let mut record_count_le = [0u8; 2];
        record_count_le.clone_from_slice(&response[4..6]);
        Ok(u16::from_le_bytes(record_count_le))
    }

    pub fn get_record_bytes(
        &mut self,
        total_records: u16,
        sequence_number: u16,
    ) -> Result<Vec<u8>> {
        // Create a request with a payload of `01 a4 00 00 00 00 xx xx xx xx 00
        // 04`, where `xx xx xx xx` changes meaning based on the sequence_number
        // value
        let mut request: [u8; 12] = [0x01, 0xa4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x04];

        // If sequence_number is 0 then `xx xx xx xx` is `xx xx 00 00`, where
        // `xx xx` is total_records in little endian
        //
        // Else `xx xx xx xx` is `00 00 xx xx`, where `xx xx` is sequence_number
        // in little endian
        if sequence_number == 0 {
            request[6..8].clone_from_slice(&total_records.to_le_bytes());
        } else {
            request[8..10].clone_from_slice(&sequence_number.to_le_bytes());
        }

        // Get the response
        let response = self.request(&request)?;

        // If one between the response length, the response header or the last
        // two bits is wrong return an error
        if response.len() != 1038
            || response[..12] != [0xaa, 0x55, 0x01, 0x01, 0, 0, 0, 0, 0, 0, 0x55, 0xaa]
            || response[1036..] != [0, 0]
        {
            return Err(Error::new(InvalidData, "Malformed response"));
        }

        // Return only the payload bits as a vector
        Ok(response[12..1036].to_vec())
    }

    pub fn into_record_iter(&mut self) -> Result<RecordIterator> {
        RecordIterator::from(self)
    }
}