//! Support for in-kernel debugging.
//!
//! For printing, this module uses an internal buffer to write the strings into.
//! If you are writing and the buffer fills up, you can make the size of
//! `output_buffer` larger.
//!
//! Before debug interfaces can be used, the board file must assign them hardware:
//!
//! ```ignore
//! kernel::debug::assign_gpios(
//!     Some(&sam4l::gpio::PA[13]),
//!     Some(&sam4l::gpio::PA[15]),
//!     None,
//! );
//!
//! components::debug_writer::DebugWriterComponent::new(uart_mux).finalize(());
//! ```
//!
//! The debug queue is optional, if not set in the board it is just ignored.
//! You can add one in the board file as follows:
//!
//! ```ignore
//! let buf = static_init!([u8; 1024], [0; 1024]);
//! components::debug_queue::DebugQueueComponent::new(buf).finalize(());
//! ```
//!
//! Example
//! -------
//!
//! ```no_run
//! # use kernel::{debug, debug_enqueue, debug_flush_queue, debug_gpio, debug_verbose};
//! # fn main() {
//! # let i = 42;
//! debug!("Yes the code gets here with value {}", i);
//! debug_verbose!("got here"); // Includes message count, file, and line.
//!
//! debug_gpio!(0, toggle); // Toggles the first debug GPIO.
//!
//! debug_enqueue!("foo"); // Adds some message to the debug queue.
//! debug_flush_queue!(); // Flushes the queue, writing "foo".
//! debug_enqueue!("bar");
//! panic!("42"); // Flushes the queue, writing "bar" in the debug queue section
//!               // of the panic diagnostic.
//! # }
//! ```
//!
//! ```text
//! Yes the code gets here with value 42
//! TOCK_DEBUG(0): /tock/capsules/src/sensys.rs:24: got here
//! ```

use core::cell::Cell;
use core::fmt::{write, Arguments, Result, Write};
use core::panic::PanicInfo;
use core::str;

use crate::collections::queue::Queue;
use crate::collections::ring_buffer::RingBuffer;
use crate::hil;
use crate::platform::chip::Chip;
use crate::process::Process;
use crate::utilities::cells::NumericCellExt;
use crate::utilities::cells::{MapCell, TakeCell};
use crate::ErrorCode;

/// This trait is similar to std::io::Write in that it takes bytes instead of a string (contrary to
/// core::fmt::Write), but io::Write isn't available in no_std (due to std::io::Error not being
/// available).
///
/// Also, in our use cases, writes are infaillible, so the write function just doesn't return
/// anything.
///
/// See also the tracking issue: <https://github.com/rust-lang/rfcs/issues/2262>
pub trait IoWrite {
    fn write(&mut self, buf: &[u8]);

    fn write_ring_buffer<'a>(&mut self, buf: &RingBuffer<'a, u8>) {
        let (left, right) = buf.as_slices();
        if let Some(slice) = left {
            self.write(slice);
        }
        if let Some(slice) = right {
            self.write(slice);
        }
    }
}

///////////////////////////////////////////////////////////////////
// panic! support routines

/// Tock panic routine, without the infinite LED-blinking loop.
///
/// This is useful for boards which do not feature LEDs to blink or
/// want to implement their own behaviour. This method returns after
/// performing the panic dump.
///
/// After this method returns, the system is no longer in a
/// well-defined state. Care must be taken on how one interacts with
/// the system once this function returns.
///
/// **NOTE:** The supplied `writer` must be synchronous.
pub unsafe fn panic_print<W: Write + IoWrite, C: Chip>(
    writer: &mut W,
    panic_info: &PanicInfo,
    nop: &dyn Fn(),
    processes: &'static [Option<&'static dyn Process>],
    chip: &'static Option<&'static C>,
) {
    panic_begin(nop);
    panic_banner(writer, panic_info);
    // Flush debug buffer if needed
    flush(writer);
    panic_cpu_state(chip, writer);
    panic_process_info(processes, writer);
}

/// Tock default panic routine.
///
/// **NOTE:** The supplied `writer` must be synchronous.
pub unsafe fn panic<L: hil::led::Led, W: Write + IoWrite, C: Chip>(
    leds: &mut [&L],
    writer: &mut W,
    panic_info: &PanicInfo,
    nop: &dyn Fn(),
    processes: &'static [Option<&'static dyn Process>],
    chip: &'static Option<&'static C>,
) -> ! {
    // Call `panic_print` first which will print out the panic
    // information and return
    panic_print(writer, panic_info, nop, processes, chip);

    // The system is no longer in a well-defined state, we cannot
    // allow this function to return
    //
    // Forever blink LEDs in an infinite loop
    panic_blink_forever(leds)
}

/// Generic panic entry.
///
/// This opaque method should always be called at the beginning of a board's
/// panic method to allow hooks for any core kernel cleanups that may be
/// appropriate.
pub unsafe fn panic_begin(nop: &dyn Fn()) {
    // Let any outstanding uart DMA's finish
    for _ in 0..200000 {
        nop();
    }
}

/// Lightweight prints about the current panic and kernel version.
///
/// **NOTE:** The supplied `writer` must be synchronous.
pub unsafe fn panic_banner<W: Write>(writer: &mut W, panic_info: &PanicInfo) {
    let _ = writer.write_fmt(format_args!("\r\n{}\r\n", panic_info));

    // Print version of the kernel
    let _ = writer.write_fmt(format_args!(
        "\tKernel version {}\r\n",
        option_env!("TOCK_KERNEL_VERSION").unwrap_or("unknown")
    ));
}

/// Print current machine (CPU) state.
///
/// **NOTE:** The supplied `writer` must be synchronous.
pub unsafe fn panic_cpu_state<W: Write, C: Chip>(
    chip: &'static Option<&'static C>,
    writer: &mut W,
) {
    chip.map(|c| {
        c.print_state(writer);
    });
}

/// More detailed prints about all processes.
///
/// **NOTE:** The supplied `writer` must be synchronous.
pub unsafe fn panic_process_info<W: Write>(
    procs: &'static [Option<&'static dyn Process>],
    writer: &mut W,
) {
    // print data about each process
    let _ = writer.write_fmt(format_args!("\r\n---| App Status |---\r\n"));
    for idx in 0..procs.len() {
        procs[idx].as_ref().map(|process| {
            process.print_full_process(writer);
        });
    }
}

/// Blinks a recognizable pattern forever.
///
/// If a multi-color LED is used for the panic pattern, it is
/// advised to turn off other LEDs before calling this method.
///
/// Generally, boards should blink red during panic if possible,
/// otherwise choose the 'first' or most prominent LED. Some
/// boards may find it appropriate to blink multiple LEDs (e.g.
/// one on the top and one on the bottom), thus this method
/// accepts an array, however most will only need one.
pub fn panic_blink_forever<L: hil::led::Led>(leds: &mut [&L]) -> ! {
    leds.iter_mut().for_each(|led| led.init());
    loop {
        for _ in 0..1000000 {
            leds.iter_mut().for_each(|led| led.on());
        }
        for _ in 0..100000 {
            leds.iter_mut().for_each(|led| led.off());
        }
        for _ in 0..1000000 {
            leds.iter_mut().for_each(|led| led.on());
        }
        for _ in 0..500000 {
            leds.iter_mut().for_each(|led| led.off());
        }
    }
}

// panic! support routines
///////////////////////////////////////////////////////////////////

///////////////////////////////////////////////////////////////////
// debug_gpio! support

pub static mut DEBUG_GPIOS: (
    Option<&'static dyn hil::gpio::Pin>,
    Option<&'static dyn hil::gpio::Pin>,
    Option<&'static dyn hil::gpio::Pin>,
) = (None, None, None);

pub unsafe fn assign_gpios(
    gpio0: Option<&'static dyn hil::gpio::Pin>,
    gpio1: Option<&'static dyn hil::gpio::Pin>,
    gpio2: Option<&'static dyn hil::gpio::Pin>,
) {
    DEBUG_GPIOS.0 = gpio0;
    DEBUG_GPIOS.1 = gpio1;
    DEBUG_GPIOS.2 = gpio2;
}

/// In-kernel gpio debugging, accepts any GPIO HIL method
#[macro_export]
macro_rules! debug_gpio {
    ($i:tt, $method:ident $(,)?) => {{
        #[allow(unused_unsafe)]
        unsafe {
            $crate::debug::DEBUG_GPIOS.$i.map(|g| g.$method());
        }
    }};
}

///////////////////////////////////////////////////////////////////
// debug_enqueue! support

/// Wrapper type that we need a mutable reference to for the core::fmt::Write
/// interface.
pub struct DebugQueueWrapper {
    dw: MapCell<&'static DebugQueue>,
}

impl DebugQueueWrapper {
    pub fn new(dw: &'static DebugQueue) -> Self {
        Self {
            dw: MapCell::new(dw),
        }
    }
}

pub struct DebugQueue {
    ring_buffer: TakeCell<'static, RingBuffer<'static, u8>>,
}

impl DebugQueue {
    pub fn new(ring_buffer: &'static mut RingBuffer<'static, u8>) -> Self {
        Self {
            ring_buffer: TakeCell::new(ring_buffer),
        }
    }
}

static mut DEBUG_QUEUE: Option<&'static mut DebugQueueWrapper> = None;

/// Function used by board main.rs to set a reference to the debug queue.
pub unsafe fn set_debug_queue(buffer: &'static mut DebugQueueWrapper) {
    DEBUG_QUEUE = Some(buffer);
}

impl Write for DebugQueueWrapper {
    fn write_str(&mut self, s: &str) -> Result {
        self.dw.map(|dw| {
            dw.ring_buffer.map(|ring_buffer| {
                let bytes = s.as_bytes();
                for &b in bytes {
                    ring_buffer.push(b);
                }
            });
        });

        Ok(())
    }
}

pub fn debug_enqueue_fmt(args: Arguments) {
    unsafe { DEBUG_QUEUE.as_deref_mut() }.map(|buffer| {
        let _ = write(buffer, args);
        let _ = buffer.write_str("\r\n");
    });
}

pub fn debug_flush_queue_() {
    let writer = unsafe { get_debug_writer() };

    unsafe { DEBUG_QUEUE.as_deref_mut() }.map(|buffer| {
        buffer.dw.map(|dw| {
            dw.ring_buffer.map(|ring_buffer| {
                writer.write_ring_buffer(ring_buffer);
                ring_buffer.empty();
            });
        });
    });
}

/// This macro prints a new line to an internal ring buffer, the contents of
/// which are only flushed with `debug_flush_queue!` and in the panic handler.
#[macro_export]
macro_rules! debug_enqueue {
    () => ({
        debug_enqueue!("")
    });
    ($msg:expr $(,)?) => ({
        $crate::debug::debug_enqueue_fmt(format_args!($msg))
    });
    ($fmt:expr, $($arg:tt)+) => ({
        $crate::debug::debug_enqueue_fmt(format_args!($fmt, $($arg)+))
    });
}

/// This macro flushes the contents of the debug queue into the regular
/// debug output.
#[macro_export]
macro_rules! debug_flush_queue {
    () => {{
        $crate::debug::debug_flush_queue_()
    }};
}

///////////////////////////////////////////////////////////////////
// debug! and debug_verbose! support

/// Wrapper type that we need a mutable reference to for the core::fmt::Write
/// interface.
pub struct DebugWriterWrapper {
    dw: MapCell<&'static DebugWriter>,
}

/// Main type that we need an immutable reference to so we can share it with
/// the UART provider and this debug module.
pub struct DebugWriter {
    // What provides the actual writing mechanism.
    uart: &'static dyn hil::uart::Transmit<'static>,
    // The buffer that is passed to the writing mechanism.
    output_buffer: TakeCell<'static, [u8]>,
    // An internal buffer that is used to hold debug!() calls as they come in.
    internal_buffer: TakeCell<'static, RingBuffer<'static, u8>>,
    // Number of debug!() calls.
    count: Cell<usize>,
}

/// Static variable that holds the kernel's reference to the debug tool. This is
/// needed so the debug!() macros have a reference to the object to use.
static mut DEBUG_WRITER: Option<&'static mut DebugWriterWrapper> = None;

unsafe fn try_get_debug_writer() -> Option<&'static mut DebugWriterWrapper> {
    DEBUG_WRITER.as_deref_mut()
}

unsafe fn get_debug_writer() -> &'static mut DebugWriterWrapper {
    try_get_debug_writer().expect("Must call `set_debug_writer_wrapper` in board initialization.")
}

/// Function used by board main.rs to set a reference to the writer.
pub unsafe fn set_debug_writer_wrapper(debug_writer: &'static mut DebugWriterWrapper) {
    DEBUG_WRITER = Some(debug_writer);
}

impl DebugWriterWrapper {
    pub fn new(dw: &'static DebugWriter) -> DebugWriterWrapper {
        DebugWriterWrapper {
            dw: MapCell::new(dw),
        }
    }
}

impl DebugWriter {
    pub fn new(
        uart: &'static dyn hil::uart::Transmit,
        out_buffer: &'static mut [u8],
        internal_buffer: &'static mut RingBuffer<'static, u8>,
    ) -> DebugWriter {
        DebugWriter {
            uart: uart,
            output_buffer: TakeCell::new(out_buffer),
            internal_buffer: TakeCell::new(internal_buffer),
            count: Cell::new(0), // how many debug! calls
        }
    }

    fn increment_count(&self) {
        self.count.increment();
    }

    fn get_count(&self) -> usize {
        self.count.get()
    }

    /// Write as many of the bytes from the internal_buffer to the output
    /// mechanism as possible.
    fn publish_bytes(&self) {
        // Can only publish if we have the output_buffer. If we don't that is
        // fine, we will do it when the transmit done callback happens.
        self.internal_buffer.map(|ring_buffer| {
            if let Some(out_buffer) = self.output_buffer.take() {
                let mut count = 0;

                for dst in out_buffer.iter_mut() {
                    match ring_buffer.dequeue() {
                        Some(src) => {
                            *dst = src;
                            count += 1;
                        }
                        None => {
                            break;
                        }
                    }
                }

                if count != 0 {
                    // Transmit the data in the output buffer.
                    if let Err((_err, buf)) = self.uart.transmit_buffer(out_buffer, count) {
                        self.output_buffer.put(Some(buf));
                    } else {
                        self.output_buffer.put(None);
                    }
                }
            }
        });
    }

    fn extract(&self) -> Option<&mut RingBuffer<'static, u8>> {
        self.internal_buffer.take()
    }
}

impl hil::uart::TransmitClient for DebugWriter {
    fn transmitted_buffer(
        &self,
        buffer: &'static mut [u8],
        _tx_len: usize,
        _rcode: core::result::Result<(), ErrorCode>,
    ) {
        // Replace this buffer since we are done with it.
        self.output_buffer.replace(buffer);

        if self.internal_buffer.map_or(false, |buf| buf.has_elements()) {
            // Buffer not empty, go around again
            self.publish_bytes();
        }
    }
    fn transmitted_word(&self, _rcode: core::result::Result<(), ErrorCode>) {}
}

/// Pass through functions.
impl DebugWriterWrapper {
    fn increment_count(&self) {
        self.dw.map(|dw| {
            dw.increment_count();
        });
    }

    fn get_count(&self) -> usize {
        self.dw.map_or(0, |dw| dw.get_count())
    }

    fn publish_bytes(&self) {
        self.dw.map(|dw| {
            dw.publish_bytes();
        });
    }

    fn extract(&self) -> Option<&mut RingBuffer<'static, u8>> {
        self.dw.map_or(None, |dw| dw.extract())
    }
}

impl IoWrite for DebugWriterWrapper {
    fn write(&mut self, bytes: &[u8]) {
        const FULL_MSG: &[u8] = b"\n*** DEBUG BUFFER FULL ***\n";
        self.dw.map(|dw| {
            dw.internal_buffer.map(|ring_buffer| {
                let available_len_for_msg =
                    ring_buffer.available_len().saturating_sub(FULL_MSG.len());

                if available_len_for_msg >= bytes.len() {
                    for &b in bytes {
                        ring_buffer.enqueue(b);
                    }
                } else {
                    for &b in &bytes[..available_len_for_msg] {
                        ring_buffer.enqueue(b);
                    }
                    // When the buffer is close to full, print a warning and drop the current
                    // string.
                    for &b in FULL_MSG {
                        ring_buffer.enqueue(b);
                    }
                }
            });
        });
    }
}

impl Write for DebugWriterWrapper {
    fn write_str(&mut self, s: &str) -> Result {
        self.write(s.as_bytes());
        Ok(())
    }
}

pub fn debug_print(args: Arguments) {
    let writer = unsafe { get_debug_writer() };

    let _ = write(writer, args);
    writer.publish_bytes();
}

pub fn debug_println(args: Arguments) {
    let writer = unsafe { get_debug_writer() };

    let _ = write(writer, args);
    let _ = writer.write_str("\r\n");
    writer.publish_bytes();
}

fn write_header(writer: &mut DebugWriterWrapper, (file, line): &(&'static str, u32)) -> Result {
    writer.increment_count();
    let count = writer.get_count();
    writer.write_fmt(format_args!("TOCK_DEBUG({}): {}:{}: ", count, file, line))
}

pub fn debug_verbose_print(args: Arguments, file_line: &(&'static str, u32)) {
    let writer = unsafe { get_debug_writer() };

    let _ = write_header(writer, file_line);
    let _ = write(writer, args);
    writer.publish_bytes();
}

pub fn debug_verbose_println(args: Arguments, file_line: &(&'static str, u32)) {
    let writer = unsafe { get_debug_writer() };

    let _ = write_header(writer, file_line);
    let _ = write(writer, args);
    let _ = writer.write_str("\r\n");
    writer.publish_bytes();
}

/// In-kernel `println()` debugging.
#[macro_export]
macro_rules! debug {
    () => ({
        // Allow an empty debug!() to print the location when hit
        debug!("")
    });
    ($msg:expr $(,)?) => ({
        $crate::debug::debug_println(format_args!($msg))
    });
    ($fmt:expr, $($arg:tt)+) => ({
        $crate::debug::debug_println(format_args!($fmt, $($arg)+))
    });
}

/// In-kernel `println()` debugging with filename and line numbers.
#[macro_export]
macro_rules! debug_verbose {
    () => ({
        // Allow an empty debug_verbose!() to print the location when hit
        debug_verbose!("")
    });
    ($msg:expr $(,)?) => ({
        $crate::debug::debug_verbose_println(format_args!($msg), {
            // TODO: Maybe make opposite choice of panic!, no `static`, more
            // runtime code for less static data
            static _FILE_LINE: (&'static str, u32) = (file!(), line!());
            &_FILE_LINE
        })
    });
    ($fmt:expr, $($arg:tt)+) => ({
        $crate::debug::debug_verbose_println(format_args!($fmt, $($arg)+), {
            static _FILE_LINE: (&'static str, u32) = (file!(), line!());
            &_FILE_LINE
        })
    });
}

pub trait Debug {
    fn write(&self, buf: &'static mut [u8], len: usize);
}

#[cfg(debug = "true")]
impl Default for Debug {
    fn write(&self, buf: &'static mut [u8], len: usize) {
        panic!(
            "No registered kernel debug printer. Thrown printing {:?}",
            buf
        );
    }
}

pub unsafe fn flush<W: Write + IoWrite>(writer: &mut W) {
    if let Some(debug_writer) = try_get_debug_writer() {
        if let Some(ring_buffer) = debug_writer.extract() {
            if ring_buffer.has_elements() {
                let _ = writer.write_str(
                    "\r\n---| Debug buffer not empty. Flushing. May repeat some of last message(s):\r\n",
                );

                writer.write_ring_buffer(ring_buffer);
            }
        }

        match DEBUG_QUEUE.as_deref_mut() {
            None => {
                let _ = writer.write_str(
                    "\r\n---| No debug queue found. You can set it with the DebugQueue component.\r\n",
                );
            }
            Some(buffer) => {
                let _ = writer.write_str("\r\n---| Flushing debug queue:\r\n");
                buffer.dw.map(|dw| {
                    dw.ring_buffer.map(|ring_buffer| {
                        writer.write_ring_buffer(ring_buffer);
                    });
                });
            }
        }
    } else {
        let _ = writer.write_str(
            "\r\n---| Global debug writer not registered.\
             \r\n     Call `set_debug_writer_wrapper` in board initialization.\r\n",
        );
    }
}