use std::{
    collections::HashMap,
    io::{Read, Write},
    sync::{
        atomic::{AtomicBool, Ordering},
        Arc, Mutex,
    },
    thread,
    time::Duration,
};

use serialport::{DataBits, FlowControl, Parity, SerialPort, SerialPortType, StopBits};
use tauri::{AppHandle, Emitter};

use crate::domain::serial::{SerialConfig, SerialDataEvent, SerialErrorEvent, SerialPortSummary};

struct SerialSession {
    writer: Box<dyn SerialPort>,
    stop: Arc<AtomicBool>,
}

#[derive(Default)]
pub struct SerialService {
    sessions: Mutex<HashMap<String, SerialSession>>,
}

impl SerialService {
    pub fn list_ports(&self) -> Result<Vec<SerialPortSummary>, String> {
        let mut ports = serialport::available_ports()
            .map_err(|error| format!("failed to enumerate serial ports: {error}"))?
            .into_iter()
            .map(|port| SerialPortSummary {
                path: port.port_name,
                port_type: describe_port_type(port.port_type),
            })
            .collect::<Vec<_>>();
        ports.sort_by(|left, right| left.path.cmp(&right.path));
        Ok(ports)
    }

    pub fn open(
        &self,
        app: AppHandle,
        session_id: String,
        config: SerialConfig,
    ) -> Result<(), String> {
        let data_bits = match config.data_bits {
            5 => DataBits::Five,
            6 => DataBits::Six,
            7 => DataBits::Seven,
            8 => DataBits::Eight,
            value => return Err(format!("unsupported data bits: {value}")),
        };
        let stop_bits = match config.stop_bits {
            1 => StopBits::One,
            2 => StopBits::Two,
            value => return Err(format!("unsupported stop bits: {value}")),
        };
        let parity = match config.parity.to_ascii_lowercase().as_str() {
            "none" => Parity::None,
            "odd" => Parity::Odd,
            "even" => Parity::Even,
            value => return Err(format!("unsupported parity: {value}")),
        };
        let flow_control = match config.flow_control.to_ascii_lowercase().as_str() {
            "none" => FlowControl::None,
            "software" => FlowControl::Software,
            "hardware" => FlowControl::Hardware,
            value => return Err(format!("unsupported flow control: {value}")),
        };

        let port = serialport::new(&config.path, config.baud_rate)
            .data_bits(data_bits)
            .stop_bits(stop_bits)
            .parity(parity)
            .flow_control(flow_control)
            .timeout(Duration::from_millis(100))
            .open()
            .map_err(|error| format!("failed to open {}: {error}", config.path))?;

        let mut reader = port
            .try_clone()
            .map_err(|error| format!("failed to clone serial port: {error}"))?;
        let stop = Arc::new(AtomicBool::new(false));
        let reader_stop = Arc::clone(&stop);
        let reader_session_id = session_id.clone();

        self.sessions
            .lock()
            .map_err(|_| "serial session lock poisoned".to_string())?
            .insert(session_id, SerialSession { writer: port, stop });

        thread::spawn(move || {
            let mut buffer = [0_u8; 4096];
            while !reader_stop.load(Ordering::Relaxed) {
                match reader.read(&mut buffer) {
                    Ok(0) => {}
                    Ok(length) => {
                        let _ = app.emit(
                            "serial:data",
                            SerialDataEvent {
                                session_id: reader_session_id.clone(),
                                data: buffer[..length].to_vec(),
                            },
                        );
                    }
                    Err(error) if error.kind() == std::io::ErrorKind::TimedOut => {}
                    Err(error) => {
                        let _ = app.emit(
                            "serial:error",
                            SerialErrorEvent {
                                session_id: reader_session_id.clone(),
                                message: error.to_string(),
                            },
                        );
                        break;
                    }
                }
            }
        });

        Ok(())
    }

    pub fn write(&self, session_id: &str, data: &[u8]) -> Result<(), String> {
        let mut sessions = self
            .sessions
            .lock()
            .map_err(|_| "serial session lock poisoned".to_string())?;
        let session = sessions
            .get_mut(session_id)
            .ok_or_else(|| format!("serial session not found: {session_id}"))?;
        session
            .writer
            .write_all(data)
            .map_err(|error| format!("serial write failed: {error}"))?;
        session
            .writer
            .flush()
            .map_err(|error| format!("serial flush failed: {error}"))
    }

    pub fn close(&self, session_id: &str) -> Result<(), String> {
        if let Some(session) = self
            .sessions
            .lock()
            .map_err(|_| "serial session lock poisoned".to_string())?
            .remove(session_id)
        {
            session.stop.store(true, Ordering::Relaxed);
        }
        Ok(())
    }
}

fn describe_port_type(port_type: SerialPortType) -> String {
    match port_type {
        SerialPortType::UsbPort(info) => match info.product {
            Some(product) => format!("USB · {product}"),
            None => format!("USB · {:04x}:{:04x}", info.vid, info.pid),
        },
        SerialPortType::BluetoothPort => "Bluetooth".to_string(),
        SerialPortType::PciPort => "PCI".to_string(),
        SerialPortType::Unknown => "Serial".to_string(),
    }
}

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

    #[test]
    fn enumerated_ports_are_sorted_and_have_labels() {
        let ports = SerialService::default()
            .list_ports()
            .expect("serial port enumeration should not fail");
        assert!(ports.windows(2).all(|pair| pair[0].path <= pair[1].path));
        assert!(ports.iter().all(|port| !port.port_type.is_empty()));
    }

    #[test]
    fn describes_bluetooth_ports() {
        assert_eq!(
            describe_port_type(SerialPortType::BluetoothPort),
            "Bluetooth"
        );
    }
}