#![no_std]
#![doc = include_str!("../README.md")]
#![warn(missing_docs)]

use core::fmt::Write as _;
use core::future::Future;

use embassy_futures::join::join;
use embassy_sync::pipe::Pipe;
use embassy_usb::class::cdc_acm::{CdcAcmClass, Receiver, Sender, State};
use embassy_usb::driver::{Driver, EndpointError};
use embassy_usb::{Builder, Config};
use log::{Metadata, Record};

type CS = embassy_sync::blocking_mutex::raw::CriticalSectionRawMutex;

/// A trait that can be implemented and then passed to the
pub trait ReceiverHandler {
    /// Data comes in from the serial port with each command and runs this function
    fn handle_data(&self, data: &[u8]) -> impl Future<Output = ()> + Send;

    /// Create a new instance of the Handler
    fn new() -> Self;
}

/// Use this Handler if you don't wish to use any handler
pub struct DummyHandler;

impl ReceiverHandler for DummyHandler {
    async fn handle_data(&self, _data: &[u8]) {}
    fn new() -> Self {
        Self {}
    }
}

/// The logger state containing buffers that must live as long as the USB peripheral.
pub struct LoggerState<'d> {
    state: State<'d>,
    config_descriptor: [u8; 128],
    bos_descriptor: [u8; 16],
    msos_descriptor: [u8; 256],
    control_buf: [u8; 64],
}

impl<'d> LoggerState<'d> {
    /// Create a new instance of the logger state.
    pub fn new() -> Self {
        Self {
            state: State::new(),
            config_descriptor: [0; 128],
            bos_descriptor: [0; 16],
            msos_descriptor: [0; 256],
            control_buf: [0; 64],
        }
    }
}

/// The packet size used in the usb logger, to be used with `create_future_from_class`
pub const MAX_PACKET_SIZE: u8 = 64;

/// The logger handle, which contains a pipe with configurable size for buffering log messages.
pub struct UsbLogger<const N: usize, T: ReceiverHandler + Send + Sync> {
    buffer: Pipe<CS, N>,
    custom_style: Option<fn(&Record, &mut Writer<'_, N>) -> ()>,
    recieve_handler: Option<T>,
}

impl<const N: usize, T: ReceiverHandler + Send + Sync> UsbLogger<N, T> {
    /// Create a new logger instance.
    pub const fn new() -> Self {
        Self {
            buffer: Pipe::new(),
            custom_style: None,
            recieve_handler: None,
        }
    }

    /// Create a new logger instance with a custom formatter.
    pub const fn with_custom_style(custom_style: fn(&Record, &mut Writer<'_, N>) -> ()) -> Self {
        Self {
            buffer: Pipe::new(),
            custom_style: Some(custom_style),
            recieve_handler: None,
        }
    }

    /// Add a command handler to the logger
    pub fn with_handler(&mut self, handler: T) {
        self.recieve_handler = Some(handler);
    }

    /// Run the USB logger using the state and USB driver. Never returns.
    pub async fn run<'d, D>(&'d self, state: &'d mut LoggerState<'d>, driver: D) -> !
    where
        D: Driver<'d>,
        Self: 'd,
    {
        let mut config = Config::new(0xc0de, 0xcafe);
        config.manufacturer = Some("Embassy");
        config.product = Some("USB-serial logger");
        config.serial_number = None;
        config.max_power = 100;
        config.max_packet_size_0 = MAX_PACKET_SIZE;

        let mut builder = Builder::new(
            driver,
            config,
            &mut state.config_descriptor,
            &mut state.bos_descriptor,
            &mut state.msos_descriptor,
            &mut state.control_buf,
        );

        // Create classes on the builder.
        let class = CdcAcmClass::new(&mut builder, &mut state.state, MAX_PACKET_SIZE as u16);
        let (mut sender, mut receiver) = class.split();

        // Build the builder.
        let mut device = builder.build();
        loop {
            let run_fut = device.run();
            let class_fut = self.run_logger_class(&mut sender, &mut receiver);
            join(run_fut, class_fut).await;
        }
    }

    async fn run_logger_class<'d, D>(&self, sender: &mut Sender<'d, D>, receiver: &mut Receiver<'d, D>)
    where
        D: Driver<'d>,
    {
        let log_fut = async {
            let mut rx: [u8; MAX_PACKET_SIZE as usize] = [0; MAX_PACKET_SIZE as usize];
            sender.wait_connection().await;
            loop {
                let len = self.buffer.read(&mut rx[..]).await;
                if Err(EndpointError::Disabled) == sender.write_packet(&rx[..len]).await
                    || len as u8 == MAX_PACKET_SIZE && Err(EndpointError::Disabled) == sender.write_packet(&[]).await
                {
                    sender.wait_connection().await;
                };
            }
        };
        let reciever_fut = async {
            let mut reciever_buf: [u8; MAX_PACKET_SIZE as usize] = [0; MAX_PACKET_SIZE as usize];
            receiver.wait_connection().await;
            loop {
                let n = match receiver.read_packet(&mut reciever_buf).await {
                    Err(EndpointError::Disabled) => {
                        receiver.wait_connection().await;
                        continue;
                    }
                    Err(_) => continue,
                    Ok(n) => n,
                };
                match &self.recieve_handler {
                    Some(handler) => {
                        let data = &reciever_buf[..n];
                        handler.handle_data(data).await;
                    }
                    None => (),
                }
            }
        };

        join(log_fut, reciever_fut).await;
    }

    /// Creates the futures needed for the logger from a given class
    /// This can be used in cases where the usb device is already in use for another connection
    /// Never returns.
    pub async fn create_future_from_class<'d, D>(&'d self, class: CdcAcmClass<'d, D>) -> !
    where
        D: Driver<'d>,
    {
        let (mut sender, mut receiver) = class.split();
        loop {
            self.run_logger_class(&mut sender, &mut receiver).await;
        }
    }
}

impl<const N: usize, T: ReceiverHandler + Send + Sync> log::Log for UsbLogger<N, T> {
    fn enabled(&self, _metadata: &Metadata) -> bool {
        true
    }

    fn log(&self, record: &Record) {
        if self.enabled(record.metadata()) {
            if let Some(custom_style) = self.custom_style {
                custom_style(record, &mut Writer(&self.buffer));
            } else {
                let _ = write!(Writer(&self.buffer), "{}\r\n", record.args());
            }
        }
    }

    fn flush(&self) {}
}

/// A writer that writes to the USB logger buffer.
pub struct Writer<'d, const N: usize>(&'d Pipe<CS, N>);

impl<'d, const N: usize> core::fmt::Write for Writer<'d, N> {
    fn write_str(&mut self, s: &str) -> Result<(), core::fmt::Error> {
        // The Pipe is implemented in such way that we cannot
        // write across the wraparound discontinuity.
        let b = s.as_bytes();
        if let Ok(n) = self.0.try_write(b) {
            if n < b.len() {
                // We wrote some data but not all, attempt again
                // as the reason might be a wraparound in the
                // ring buffer, which resolves on second attempt.
                let _ = self.0.try_write(&b[n..]);
            }
        }
        Ok(())
    }
}

/// Initialize and run the USB serial logger, never returns.
///
/// Arguments specify the buffer size, log level and the USB driver, respectively. You can optionally add a RecieverHandler.
///
/// # Usage
///
/// ```
/// embassy_usb_logger::run!(1024, log::LevelFilter::Info, driver); //never returns
/// ```
///
/// # Safety
///
/// This macro should only be invoked only once since it is setting the global logging state of the application.
#[macro_export]
macro_rules! run {
    ( $x:expr, $l:expr, $p:ident ) => {
        static LOGGER: ::embassy_usb_logger::UsbLogger<$x, ::embassy_usb_logger::DummyHandler> =
            ::embassy_usb_logger::UsbLogger::new();
        unsafe {
            let _ = ::log::set_logger_racy(&LOGGER).map(|()| log::set_max_level_racy($l));
        }
        let _ = LOGGER.run(&mut ::embassy_usb_logger::LoggerState::new(), $p).await;
    };

    ( $x:expr, $l:expr, $p:ident, $h:ty ) => {
        unsafe {
            static mut LOGGER: ::embassy_usb_logger::UsbLogger<$x, $h> = ::embassy_usb_logger::UsbLogger::new();
            LOGGER.with_handler(<$h>::new());
            let _ = ::log::set_logger_racy(&LOGGER).map(|()| log::set_max_level_racy($l));
            let _ = LOGGER.run(&mut ::embassy_usb_logger::LoggerState::new(), $p).await;
        }
    };
}

/// Initialize the USB serial logger from a serial class and return the future to run it.
/// The future never returns.
///
/// Arguments specify the buffer size, log level and the serial class, respectively. You can optionally add a RecieverHandler.
///
/// # Usage
///
/// ```
/// embassy_usb_logger::with_class!(1024, log::LevelFilter::Info, class).await; //never returns.
/// ```
///
/// # Safety
///
/// This macro should only be invoked only once since it is setting the global logging state of the application.
#[macro_export]
macro_rules! with_class {
    ( $x:expr, $l:expr, $p:ident ) => {{
        static LOGGER: ::embassy_usb_logger::UsbLogger<$x, ::embassy_usb_logger::DummyHandler> =
            ::embassy_usb_logger::UsbLogger::new();
        unsafe {
            let _ = ::log::set_logger_racy(&LOGGER).map(|()| log::set_max_level_racy($l));
        }
        LOGGER.create_future_from_class($p)
    }};

    ( $x:expr, $l:expr, $p:ident, $h:ty ) => {{
        unsafe {
            static mut LOGGER: ::embassy_usb_logger::UsbLogger<$x, $h> = ::embassy_usb_logger::UsbLogger::new();
            LOGGER.with_handler(<$h>::new());
            let _ = ::log::set_logger_racy(&LOGGER).map(|()| log::set_max_level_racy($l));
            LOGGER.create_future_from_class($p)
        }
    }};
}

/// Initialize the USB serial logger from a serial class and return the future to run it.
/// The future never returns.
/// This version of the macro allows for a custom style function to be passed in.
/// The custom style function will be called for each log record and is responsible for writing the log message to the buffer.
///
/// Arguments specify the buffer size, log level, the serial class and the custom style function, respectively. You can optionally add a RecieverHandler.
///
/// # Usage
///
/// ```
/// let log_fut = embassy_usb_logger::with_custom_style!(1024, log::LevelFilter::Info, logger_class, |record, writer| {
///     use core::fmt::Write;
///     let level = record.level().as_str();
///     write!(writer, "[{level}] {}\r\n", record.args()).unwrap();
/// });
/// log_fut.await; // never returns
/// ```
///
/// # Safety
///
/// This macro should only be invoked only once since it is setting the global logging state of the application.
#[macro_export]
macro_rules! with_custom_style {
    ( $x:expr, $l:expr, $p:ident, $s:expr ) => {{
        static LOGGER: ::embassy_usb_logger::UsbLogger<$x, ::embassy_usb_logger::DummyHandler> =
            ::embassy_usb_logger::UsbLogger::with_custom_style($s);
        unsafe {
            let _ = ::log::set_logger_racy(&LOGGER).map(|()| log::set_max_level_racy($l));
        }
        LOGGER.create_future_from_class($p)
    }};

    ( $x:expr, $l:expr, $p:ident, $s:expr, $h:ty ) => {{
        unsafe {
            static mut LOGGER: ::embassy_usb_logger::UsbLogger<$x, $h> =
                ::embassy_usb_logger::UsbLogger::with_custom_style($s);
            LOGGER.with_handler(<$h>::new());
            let _ = ::log::set_logger_racy(&LOGGER).map(|()| log::set_max_level_racy($l));
            LOGGER.create_future_from_class($p)
        }
    }};
}
