use crate::command::Command;

use std::iter::FromIterator;
use std::thread;
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};


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

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

impl Error for ModemError {}

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

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

impl<UART: serial::Uart> Modem<UART> {
    pub fn new(tx: Tx<UART>, rx: Rx<UART>) -> Self {
        Self {
            is_connected: false,
            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, expected: Option<String>, timeout: Duration) -> Result<String> {
        let len = self.rx.count()
            .map_err(|_| ModemError::CommandError("Error getting RX fifo length".to_owned()))?;

        println!("Reading {} bytes from serial RX ...", len);

        let mut response = String::new();
        let now = Instant::now();

        loop {
            let len = self.rx.count().unwrap();
            if len == 0 {
                if now + timeout > Instant::now() {
                    break;
                }
                thread::sleep(Duration::from_secs(1));
                continue;
            }
            println!("Reading {} bytes from serial RX ...", len);

            for _ in 0..len {
                nb::block!(self.rx.read())
                    .map(|b| response.push(b as char))
                    .map_err(|_| ModemError::CommandError("Error reading from RX".to_owned()))?;
            }
        }
        let response = response.trim();

        println!("Received: {}", response);

        expected.map(|expected_end| {
            if response.ends_with(&expected_end) {
                Ok(response.to_owned())
            } else {
                let res = String::from_iter(response.chars().rev().take(expected_end.len()));
                Err(ModemError::CommandError(format!("Got invalid response end {} instead of expected {}", res, expected_end)))
            }
        }).unwrap_or(Ok(response.to_owned()))
    }

    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_owned()))?;
        }
        self.read_response(cmd.ends_with, cmd.timeout)
    }

    pub fn connect_to_gprs_ap(&mut self, apn: &str, username: &str, password: &str)-> Result<()> {
        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))?;
        let _ = self.send_command(Command::opengprs())?;

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

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

/// 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 mut modem_pwrkey = dp.pins.gpio4.into_output().unwrap();
/// let mut modem_rst = dp.pins.gpio5.into_output().unwrap();
/// let mut 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_owned()))?;
    rst.set_high().map_err(|_| ModemError::SetupError("Error setting RST to high.".to_owned()))?;
    // 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_owned()))?;
    thread::sleep(Duration::from_millis(100));
    pwrkey.set_low().map_err(|_| ModemError::SetupError("Error setting PWRKEY to low.".to_owned()))?;
    thread::sleep(Duration::from_millis(1000));
    pwrkey.set_high().map_err(|_| ModemError::SetupError("Error setting PWRKEY to high.".to_owned()))?;
    println!("Waiting 3s for sim module to come online ...");
    thread::sleep(Duration::from_millis(3000));
    Ok(())
}