use crate::command::Command;

use std::thread;
use std::io::{Error as IoError, ErrorKind, BufRead};
use std::error::Error;
use std::time::{Duration, Instant};

use embedded_hal::serial::{Read, Write};
use embedded_hal::digital::v2::OutputPin;
use esp_idf_hal::serial::{self, Rx, Tx, SerialError};

pub type Result<T> = std::result::Result<T, ModemError>;

pub struct Modem<UART: serial::Uart> {
    is_connected: bool,
    rx: MyRx<UART>,
    tx: Tx<UART>,
}

#[derive(Debug)]
pub enum ModemError {
    CommandError(String),
    SetupError(String),
    TimeoutError,
}

impl Error for ModemError {}

impl std::fmt::Display for ModemError {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(f, "{:?}", self)
    }
}

struct MyRx<UART: serial::Uart>(Rx<UART>);

impl<UART: serial::Uart> MyRx<UART> {
    fn read(&mut self) -> nb::Result<u8, SerialError> {
        self.0.read()
    }

    fn read_blocking(&mut self) -> std::result::Result<u8, SerialError> {
        nb::block!(self.read())
    }
}

impl<UART: serial::Uart> std::io::Read for MyRx<UART> {
    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
        let mut read_bytes: usize = 0;
        loop {
            let b = self.read_blocking()
                .map_err(|err| IoError::new(ErrorKind::Other, format!("Serial error {:?}", err)))?;
            buf[read_bytes] = b;
            read_bytes += 1;
            if b == '\0' as u8 || b == '\n' as u8 {
                break;
            }
        };
        Ok(read_bytes)
    }
}

impl<UART: serial::Uart> Modem<UART> {
    pub fn new(tx: Tx<UART>, rx: Rx<UART>) -> Self {
        Self {
            is_connected: false,
            rx: MyRx(rx),
            tx,
        }
    }

    /// Reads the serial RX until it has bytes, or until a timeout is reached. The timeout is
    /// provided on input via the `timeout` argument. The first argument `expected` is the expected
    /// end of the buffer. If it's `None`, the whole response is returned as is. If it's
    /// `Some(expected_end)`, then the end of the response is matched against `expected_end`. If
    /// they match, great! The response is returned from the function, but if not, then a
    /// [ModemError::CommandError](crate::modem::ModemError::CommandError) is returned.
    ///
    /// It's ok to use this function like this for now because the write/read cycle is blocking,
    /// hence the case where multiple writes happen asynchronously isn't handled. See
    /// [send_command](crate::modem::Modem::send_command) for more info on the blocking part.
    fn read_response(&mut self, contains: Option<String>, timeout: Duration) -> Result<String> {
        let mut response = String::new();
        let now = Instant::now();
        let match_text: String = contains.unwrap_or("".to_string());

        let mut reader = std::io::BufReader::new(&mut self.rx);

        loop {
            let mut line = String::new();
            reader.read_line(&mut line)
                .map_err(|err| ModemError::CommandError(format!("read line failed: {}", err)))?;
            println!("Read {} from serial ...", line.trim());

            // check if empty first because it's much simpler and more frequent
            if line == "" {
                if now + timeout > Instant::now() {
                    return Err(ModemError::TimeoutError);
                }
                thread::sleep(Duration::from_millis(1000));
                continue;
            } else {
                response.push_str(&line);
                if line.contains(&match_text) {
                    println!("Found match {} for line {} ... exiting response reader now!", match_text, line);
                    println!("-----------------------------------------------------------");
                    break;
                }
            }
        }
        Ok(response.to_string())
    }

    fn send_command(&mut self, cmd: Command) -> Result<String> {
        for b in cmd.text.as_bytes().iter() {
            nb::block!(self.tx.write(*b)).map_err(|_| ModemError::CommandError("error writing to serial".to_string()))?;
        }
        nb::block!(self.tx.write('\r' as u8)).map_err(|_| ModemError::CommandError("error writing <CR> to serial".to_string()))?;
        self.read_response(cmd.contains.clone(), cmd.timeout.clone())
    }

    pub fn get_ip_addr(&mut self) -> Result<String> {
        println!("getting ip addres ...");
        let res = self.send_command(Command::getbear())?;
        println!("{}", res);
        Ok(res)
    }

    pub fn connect_to_gprs_ap(&mut self, apn: &str, username: &str, password: &str)-> Result<()> {
        println!("init gprs ...");
        let _ = self.send_command(Command::initgprs())?;

        println!("connecting to {} with {}:{}", apn, username, password);

        let _ = self.send_command(Command::setapn(apn))?;
        let _ = self.send_command(Command::setuser(username))?;
        let _ = self.send_command(Command::setpwd(password))?;

        println!("open gprs ...");
        let _ = self.send_command(Command::initgprs())?;

        self.is_connected = true;
        Ok(())
    }

    pub fn info(&mut self)-> Result<String> {
        println!("getting modem info with API command");
        self.send_command(Command::modeminfo())
    }

    pub fn probe(&mut self)-> Result<String> {
        println!("probing modem with AP command");
        self.send_command(Command::probe())
    }

    pub fn is_gprs_attached(&mut self)-> Result<bool> {
        println!("testing gprs connection ...");
        let res = self.send_command(Command::is_gprs_attached())?;

        Ok(res.contains("+CGATT: 1"))
    }
}

/// Initialize the modem (sim800l in this case). The initialization process sets all pins in the
/// required state so that the modem is turned on, then resets it a couple of times (beats me) and
/// sleeps for 3 seconds, which is enough for the modem to come online.
///
/// Below is an example for sim800l pins on a LilyGo TTGO T-Call.
///
/// # Examples
///
/// ```
/// let modem_pwrkey = dp.pins.gpio4.into_output().unwrap();
/// let modem_rst = dp.pins.gpio5.into_output().unwrap();
/// let modem_power = dp.pins.gpio23.into_output().unwrap();
///
/// modem::init(modem_pwrkey, modem_rst, modem_power);
/// ```
pub fn init(mut pwrkey: impl OutputPin, mut rst: impl OutputPin, mut power: impl OutputPin) -> Result<()> {
    println!("Turning SIM800L on ...");
    power.set_high().map_err(|_| ModemError::SetupError("Error setting POWER to high.".to_string()))?;
    rst.set_high().map_err(|_| ModemError::SetupError("Error setting RST to high.".to_string()))?;
    // Pull down PWRKEY for more than 1 second according to manual requirements
    pwrkey.set_high().map_err(|_| ModemError::SetupError("Error setting PWRKEY to high.".to_string()))?;
    thread::sleep(Duration::from_millis(100));
    pwrkey.set_low().map_err(|_| ModemError::SetupError("Error setting PWRKEY to low.".to_string()))?;
    thread::sleep(Duration::from_millis(1000));
    pwrkey.set_high().map_err(|_| ModemError::SetupError("Error setting PWRKEY to high.".to_string()))?;
    println!("Waiting 3s for sim module to come online ...");
    thread::sleep(Duration::from_millis(3000));
    Ok(())
}