//! Successive Approximation Analog-to-Digital Converter (SAADC) driver.

#![macro_use]

use core::future::poll_fn;
use core::sync::atomic::{compiler_fence, Ordering};
use core::task::Poll;

use embassy_hal_internal::drop::OnDrop;
use embassy_hal_internal::{impl_peripheral, into_ref, PeripheralRef};
use embassy_sync::waitqueue::AtomicWaker;
pub(crate) use vals::Psel as InputChannel;

use crate::interrupt::InterruptExt;
use crate::pac::saadc::vals;
use crate::ppi::{ConfigurableChannel, Event, Ppi, Task};
use crate::timer::{Frequency, Instance as TimerInstance, Timer};
use crate::{interrupt, pac, peripherals, Peripheral};

/// SAADC error
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[cfg_attr(feature = "defmt", derive(defmt::Format))]
#[non_exhaustive]
pub enum Error {}

/// Interrupt handler.
pub struct InterruptHandler {
    _private: (),
}

impl interrupt::typelevel::Handler<interrupt::typelevel::SAADC> for InterruptHandler {
    unsafe fn on_interrupt() {
        let r = pac::SAADC;

        if r.events_calibratedone().read() != 0 {
            r.intenclr().write(|w| w.set_calibratedone(true));
            WAKER.wake();
        }

        if r.events_end().read() != 0 {
            r.intenclr().write(|w| w.set_end(true));
            WAKER.wake();
        }

        if r.events_started().read() != 0 {
            r.intenclr().write(|w| w.set_started(true));
            WAKER.wake();
        }
    }
}

static WAKER: AtomicWaker = AtomicWaker::new();

/// Used to configure the SAADC peripheral.
///
/// See the `Default` impl for suitable default values.
#[non_exhaustive]
pub struct Config {
    /// Output resolution in bits.
    pub resolution: Resolution,
    /// Average 2^`oversample` input samples before transferring the result into memory.
    pub oversample: Oversample,
}

impl Default for Config {
    /// Default configuration for single channel sampling.
    fn default() -> Self {
        Self {
            resolution: Resolution::_12BIT,
            oversample: Oversample::BYPASS,
        }
    }
}

/// Used to configure an individual SAADC peripheral channel.
///
/// Construct using the `single_ended` or `differential` methods.  These provide sensible defaults
/// for the public fields, which can be overridden if required.
#[non_exhaustive]
pub struct ChannelConfig<'d> {
    /// Reference voltage of the SAADC input.
    pub reference: Reference,
    /// Gain used to control the effective input range of the SAADC.
    pub gain: Gain,
    /// Positive channel resistor control.
    pub resistor: Resistor,
    /// Acquisition time in microseconds.
    pub time: Time,
    /// Positive channel to sample
    p_channel: PeripheralRef<'d, AnyInput>,
    /// An optional negative channel to sample
    n_channel: Option<PeripheralRef<'d, AnyInput>>,
}

impl<'d> ChannelConfig<'d> {
    /// Default configuration for single ended channel sampling.
    pub fn single_ended(input: impl Peripheral<P = impl Input> + 'd) -> Self {
        into_ref!(input);
        Self {
            reference: Reference::INTERNAL,
            gain: Gain::GAIN1_6,
            resistor: Resistor::BYPASS,
            time: Time::_10US,
            p_channel: input.map_into(),
            n_channel: None,
        }
    }
    /// Default configuration for differential channel sampling.
    pub fn differential(
        p_input: impl Peripheral<P = impl Input> + 'd,
        n_input: impl Peripheral<P = impl Input> + 'd,
    ) -> Self {
        into_ref!(p_input, n_input);
        Self {
            reference: Reference::INTERNAL,
            gain: Gain::GAIN1_6,
            resistor: Resistor::BYPASS,
            time: Time::_10US,
            p_channel: p_input.map_into(),
            n_channel: Some(n_input.map_into()),
        }
    }
}

/// Value returned by the SAADC callback, deciding what happens next.
#[derive(PartialEq)]
pub enum CallbackResult {
    /// The SAADC should keep sampling and calling the callback.
    Continue,
    /// The SAADC should stop sampling, and return.
    Stop,
}

/// One-shot and continuous SAADC.
pub struct Saadc<'d, const N: usize> {
    _p: PeripheralRef<'d, peripherals::SAADC>,
}

impl<'d, const N: usize> Saadc<'d, N> {
    /// Create a new SAADC driver.
    pub fn new(
        saadc: impl Peripheral<P = peripherals::SAADC> + 'd,
        _irq: impl interrupt::typelevel::Binding<interrupt::typelevel::SAADC, InterruptHandler> + 'd,
        config: Config,
        channel_configs: [ChannelConfig; N],
    ) -> Self {
        into_ref!(saadc);

        let r = pac::SAADC;

        let Config { resolution, oversample } = config;

        // Configure channels
        r.enable().write(|w| w.set_enable(true));
        r.resolution().write(|w| w.set_val(resolution.into()));
        r.oversample().write(|w| w.set_oversample(oversample.into()));

        for (i, cc) in channel_configs.iter().enumerate() {
            r.ch(i).pselp().write(|w| w.set_pselp(cc.p_channel.channel()));
            if let Some(n_channel) = &cc.n_channel {
                r.ch(i).pseln().write(|w| w.set_pseln(n_channel.channel()));
            }
            r.ch(i).config().write(|w| {
                w.set_refsel(cc.reference.into());
                w.set_gain(cc.gain.into());
                w.set_tacq(cc.time.into());
                w.set_mode(match cc.n_channel {
                    None => vals::ConfigMode::SE,
                    Some(_) => vals::ConfigMode::DIFF,
                });
                w.set_resp(cc.resistor.into());
                w.set_resn(vals::Resn::BYPASS);
                w.set_burst(!matches!(oversample, Oversample::BYPASS));
            });
        }

        // Disable all events interrupts
        r.intenclr().write(|w| w.0 = 0x003F_FFFF);

        interrupt::SAADC.unpend();
        unsafe { interrupt::SAADC.enable() };

        Self { _p: saadc }
    }

    fn regs() -> pac::saadc::Saadc {
        pac::SAADC
    }

    /// Perform SAADC calibration. Completes when done.
    pub async fn calibrate(&self) {
        let r = Self::regs();

        // Reset and enable the end event
        r.events_calibratedone().write_value(0);
        r.intenset().write(|w| w.set_calibratedone(true));

        // Order is important
        compiler_fence(Ordering::SeqCst);

        r.tasks_calibrateoffset().write_value(1);

        // Wait for 'calibratedone' event.
        poll_fn(|cx| {
            let r = Self::regs();

            WAKER.register(cx.waker());

            if r.events_calibratedone().read() != 0 {
                r.events_calibratedone().write_value(0);
                return Poll::Ready(());
            }

            Poll::Pending
        })
        .await;
    }

    /// One shot sampling. The buffer must be the same size as the number of channels configured.
    /// The sampling is stopped prior to returning in order to reduce power consumption (power
    /// consumption remains higher if sampling is not stopped explicitly). Cancellation will
    /// also cause the sampling to be stopped.
    pub async fn sample(&mut self, buf: &mut [i16; N]) {
        // In case the future is dropped, stop the task and wait for it to end.
        let on_drop = OnDrop::new(Self::stop_sampling_immediately);

        let r = Self::regs();

        // Set up the DMA
        r.result().ptr().write_value(buf.as_mut_ptr() as u32);
        r.result().maxcnt().write(|w| w.set_maxcnt(N as _));

        // Reset and enable the end event
        r.events_end().write_value(0);
        r.intenset().write(|w| w.set_end(true));

        // Don't reorder the ADC start event before the previous writes. Hopefully self
        // wouldn't happen anyway.
        compiler_fence(Ordering::SeqCst);

        r.tasks_start().write_value(1);
        r.tasks_sample().write_value(1);

        // Wait for 'end' event.
        poll_fn(|cx| {
            let r = Self::regs();

            WAKER.register(cx.waker());

            if r.events_end().read() != 0 {
                r.events_end().write_value(0);
                return Poll::Ready(());
            }

            Poll::Pending
        })
        .await;

        drop(on_drop);
    }

    /// Continuous sampling with double buffers.
    ///
    /// A TIMER and two PPI peripherals are passed in so that precise sampling
    /// can be attained. The sampling interval is expressed by selecting a
    /// timer clock frequency to use along with a counter threshold to be reached.
    /// For example, 1KHz can be achieved using a frequency of 1MHz and a counter
    /// threshold of 1000.
    ///
    /// A sampler closure is provided that receives the buffer of samples, noting
    /// that the size of this buffer can be less than the original buffer's size.
    /// A command is return from the closure that indicates whether the sampling
    /// should continue or stop.
    ///
    /// NOTE: The time spent within the callback supplied should not exceed the time
    /// taken to acquire the samples into a single buffer. You should measure the
    /// time taken by the callback and set the sample buffer size accordingly.
    /// Exceeding this time can lead to samples becoming dropped.
    ///
    /// The sampling is stopped prior to returning in order to reduce power consumption (power
    /// consumption remains higher if sampling is not stopped explicitly), and to
    /// free the buffers from being used by the peripheral. Cancellation will
    /// also cause the sampling to be stopped.

    pub async fn run_task_sampler<F, T: TimerInstance, const N0: usize>(
        &mut self,
        timer: &mut T,
        ppi_ch1: &mut impl ConfigurableChannel,
        ppi_ch2: &mut impl ConfigurableChannel,
        frequency: Frequency,
        sample_counter: u32,
        bufs: &mut [[[i16; N]; N0]; 2],
        callback: F,
    ) where
        F: FnMut(&[[i16; N]]) -> CallbackResult,
    {
        let r = Self::regs();

        // We want the task start to effectively short with the last one ending so
        // we don't miss any samples. It'd be great for the SAADC to offer a SHORTS
        // register instead, but it doesn't, so we must use PPI.
        let mut start_ppi = Ppi::new_one_to_one(
            ppi_ch1,
            Event::from_reg(r.events_end()),
            Task::from_reg(r.tasks_start()),
        );
        start_ppi.enable();

        let timer = Timer::new(timer);
        timer.set_frequency(frequency);
        timer.cc(0).write(sample_counter);
        timer.cc(0).short_compare_clear();

        let timer_cc = timer.cc(0);

        let mut sample_ppi = Ppi::new_one_to_one(ppi_ch2, timer_cc.event_compare(), Task::from_reg(r.tasks_sample()));

        timer.start();

        self.run_sampler(
            bufs,
            None,
            || {
                sample_ppi.enable();
            },
            callback,
        )
        .await;
    }

    async fn run_sampler<I, F, const N0: usize>(
        &mut self,
        bufs: &mut [[[i16; N]; N0]; 2],
        sample_rate_divisor: Option<u16>,
        mut init: I,
        mut callback: F,
    ) where
        I: FnMut(),
        F: FnMut(&[[i16; N]]) -> CallbackResult,
    {
        // In case the future is dropped, stop the task and wait for it to end.
        let on_drop = OnDrop::new(Self::stop_sampling_immediately);

        let r = Self::regs();

        // Establish mode and sample rate
        match sample_rate_divisor {
            Some(sr) => {
                r.samplerate().write(|w| {
                    w.set_cc(sr);
                    w.set_mode(vals::SamplerateMode::TIMERS);
                });
                r.tasks_sample().write_value(1); // Need to kick-start the internal timer
            }
            None => r.samplerate().write(|w| {
                w.set_cc(0);
                w.set_mode(vals::SamplerateMode::TASK);
            }),
        }

        // Set up the initial DMA
        r.result().ptr().write_value(bufs[0].as_mut_ptr() as u32);
        r.result().maxcnt().write(|w| w.set_maxcnt((N0 * N) as _));

        // Reset and enable the events
        r.events_end().write_value(0);
        r.events_started().write_value(0);
        r.intenset().write(|w| {
            w.set_end(true);
            w.set_started(true);
        });

        // Don't reorder the ADC start event before the previous writes. Hopefully self
        // wouldn't happen anyway.
        compiler_fence(Ordering::SeqCst);

        r.tasks_start().write_value(1);

        let mut inited = false;
        let mut current_buffer = 0;

        // Wait for events and complete when the sampler indicates it has had enough.
        let r = poll_fn(|cx| {
            let r = Self::regs();

            WAKER.register(cx.waker());

            if r.events_end().read() != 0 {
                compiler_fence(Ordering::SeqCst);

                r.events_end().write_value(0);
                r.intenset().write(|w| w.set_end(true));

                match callback(&bufs[current_buffer]) {
                    CallbackResult::Continue => {
                        let next_buffer = 1 - current_buffer;
                        current_buffer = next_buffer;
                    }
                    CallbackResult::Stop => {
                        return Poll::Ready(());
                    }
                }
            }

            if r.events_started().read() != 0 {
                r.events_started().write_value(0);
                r.intenset().write(|w| w.set_started(true));

                if !inited {
                    init();
                    inited = true;
                }

                let next_buffer = 1 - current_buffer;
                r.result().ptr().write_value(bufs[next_buffer].as_mut_ptr() as u32);
            }

            Poll::Pending
        })
        .await;

        drop(on_drop);

        r
    }

    // Stop sampling and wait for it to stop in a blocking fashion
    fn stop_sampling_immediately() {
        let r = Self::regs();

        compiler_fence(Ordering::SeqCst);

        r.events_stopped().write_value(0);
        r.tasks_stop().write_value(1);

        while r.events_stopped().read() == 0 {}
        r.events_stopped().write_value(0);
    }
}

impl<'d> Saadc<'d, 1> {
    /// Continuous sampling on a single channel with double buffers.
    ///
    /// The internal clock is to be used with a sample rate expressed as a divisor of
    /// 16MHz, ranging from 80..2047. For example, 1600 represents a sample rate of 10KHz
    /// given 16_000_000 / 10_000_000 = 1600.
    ///
    /// A sampler closure is provided that receives the buffer of samples, noting
    /// that the size of this buffer can be less than the original buffer's size.
    /// A command is return from the closure that indicates whether the sampling
    /// should continue or stop.
    pub async fn run_timer_sampler<I, S, const N0: usize>(
        &mut self,
        bufs: &mut [[[i16; 1]; N0]; 2],
        sample_rate_divisor: u16,
        sampler: S,
    ) where
        S: FnMut(&[[i16; 1]]) -> CallbackResult,
    {
        self.run_sampler(bufs, Some(sample_rate_divisor), || {}, sampler).await;
    }
}

impl<'d, const N: usize> Drop for Saadc<'d, N> {
    fn drop(&mut self) {
        let r = Self::regs();
        r.enable().write(|w| w.set_enable(false));
    }
}

impl From<Gain> for vals::Gain {
    fn from(gain: Gain) -> Self {
        match gain {
            Gain::GAIN1_6 => vals::Gain::GAIN1_6,
            Gain::GAIN1_5 => vals::Gain::GAIN1_5,
            Gain::GAIN1_4 => vals::Gain::GAIN1_4,
            Gain::GAIN1_3 => vals::Gain::GAIN1_3,
            Gain::GAIN1_2 => vals::Gain::GAIN1_2,
            Gain::GAIN1 => vals::Gain::GAIN1,
            Gain::GAIN2 => vals::Gain::GAIN2,
            Gain::GAIN4 => vals::Gain::GAIN4,
        }
    }
}

/// Gain control
#[non_exhaustive]
#[derive(Clone, Copy)]
pub enum Gain {
    /// 1/6
    GAIN1_6 = 0,
    /// 1/5
    GAIN1_5 = 1,
    /// 1/4
    GAIN1_4 = 2,
    /// 1/3
    GAIN1_3 = 3,
    /// 1/2
    GAIN1_2 = 4,
    /// 1
    GAIN1 = 5,
    /// 2
    GAIN2 = 6,
    /// 4
    GAIN4 = 7,
}

impl From<Reference> for vals::Refsel {
    fn from(reference: Reference) -> Self {
        match reference {
            Reference::INTERNAL => vals::Refsel::INTERNAL,
            Reference::VDD1_4 => vals::Refsel::VDD1_4,
        }
    }
}

/// Reference control
#[non_exhaustive]
#[derive(Clone, Copy)]
pub enum Reference {
    /// Internal reference (0.6 V)
    INTERNAL = 0,
    /// VDD/4 as reference
    VDD1_4 = 1,
}

impl From<Resistor> for vals::Resp {
    fn from(resistor: Resistor) -> Self {
        match resistor {
            Resistor::BYPASS => vals::Resp::BYPASS,
            Resistor::PULLDOWN => vals::Resp::PULLDOWN,
            Resistor::PULLUP => vals::Resp::PULLUP,
            Resistor::VDD1_2 => vals::Resp::VDD1_2,
        }
    }
}

/// Positive channel resistor control
#[non_exhaustive]
#[derive(Clone, Copy)]
pub enum Resistor {
    /// Bypass resistor ladder
    BYPASS = 0,
    /// Pull-down to GND
    PULLDOWN = 1,
    /// Pull-up to VDD
    PULLUP = 2,
    /// Set input at VDD/2
    VDD1_2 = 3,
}

impl From<Time> for vals::Tacq {
    fn from(time: Time) -> Self {
        match time {
            Time::_3US => vals::Tacq::_3US,
            Time::_5US => vals::Tacq::_5US,
            Time::_10US => vals::Tacq::_10US,
            Time::_15US => vals::Tacq::_15US,
            Time::_20US => vals::Tacq::_20US,
            Time::_40US => vals::Tacq::_40US,
        }
    }
}

/// Acquisition time, the time the SAADC uses to sample the input voltage
#[non_exhaustive]
#[derive(Clone, Copy)]
pub enum Time {
    /// 3 us
    _3US = 0,
    ///  5 us
    _5US = 1,
    /// 10 us
    _10US = 2,
    /// 15 us
    _15US = 3,
    /// 20 us
    _20US = 4,
    /// 40 us
    _40US = 5,
}

impl From<Oversample> for vals::Oversample {
    fn from(oversample: Oversample) -> Self {
        match oversample {
            Oversample::BYPASS => vals::Oversample::BYPASS,
            Oversample::OVER2X => vals::Oversample::OVER2X,
            Oversample::OVER4X => vals::Oversample::OVER4X,
            Oversample::OVER8X => vals::Oversample::OVER8X,
            Oversample::OVER16X => vals::Oversample::OVER16X,
            Oversample::OVER32X => vals::Oversample::OVER32X,
            Oversample::OVER64X => vals::Oversample::OVER64X,
            Oversample::OVER128X => vals::Oversample::OVER128X,
            Oversample::OVER256X => vals::Oversample::OVER256X,
        }
    }
}

/// Oversample control
#[non_exhaustive]
#[derive(Clone, Copy)]
pub enum Oversample {
    /// Bypass oversampling
    BYPASS = 0,
    /// Oversample 2x
    OVER2X = 1,
    /// Oversample 4x
    OVER4X = 2,
    /// Oversample 8x
    OVER8X = 3,
    /// Oversample 16x
    OVER16X = 4,
    /// Oversample 32x
    OVER32X = 5,
    /// Oversample 64x
    OVER64X = 6,
    /// Oversample 128x
    OVER128X = 7,
    /// Oversample 256x
    OVER256X = 8,
}

impl From<Resolution> for vals::Val {
    fn from(resolution: Resolution) -> Self {
        match resolution {
            Resolution::_8BIT => vals::Val::_8BIT,
            Resolution::_10BIT => vals::Val::_10BIT,
            Resolution::_12BIT => vals::Val::_12BIT,
            Resolution::_14BIT => vals::Val::_14BIT,
        }
    }
}

/// Set the resolution
#[non_exhaustive]
#[derive(Clone, Copy)]
pub enum Resolution {
    /// 8 bits
    _8BIT = 0,
    /// 10 bits
    _10BIT = 1,
    /// 12 bits
    _12BIT = 2,
    /// 14 bits
    _14BIT = 3,
}

pub(crate) trait SealedInput {
    fn channel(&self) -> InputChannel;
}

/// An input that can be used as either or negative end of a ADC differential in the SAADC periperhal.
#[allow(private_bounds)]
pub trait Input: SealedInput + Into<AnyInput> + Peripheral<P = Self> + Sized + 'static {
    /// Convert this SAADC input to a type-erased `AnyInput`.
    ///
    /// This allows using several inputs  in situations that might require
    /// them to be the same type, like putting them in an array.
    fn degrade_saadc(self) -> AnyInput {
        AnyInput {
            channel: self.channel(),
        }
    }
}

/// A type-erased SAADC input.
///
/// This allows using several inputs  in situations that might require
/// them to be the same type, like putting them in an array.
pub struct AnyInput {
    channel: InputChannel,
}

impl_peripheral!(AnyInput);

impl SealedInput for AnyInput {
    fn channel(&self) -> InputChannel {
        self.channel
    }
}

impl Input for AnyInput {}

macro_rules! impl_saadc_input {
    ($pin:ident, $ch:ident) => {
        impl_saadc_input!(@local, crate::peripherals::$pin, $ch);
    };
    (@local, $pin:ty, $ch:ident) => {
        impl crate::saadc::SealedInput for $pin {
            fn channel(&self) -> crate::saadc::InputChannel {
                crate::saadc::InputChannel::$ch
            }
        }
        impl crate::saadc::Input for $pin {}

        impl From<$pin> for crate::saadc::AnyInput {
            fn from(val: $pin) -> Self {
                crate::saadc::Input::degrade_saadc(val)
            }
        }
    };
}

/// A dummy `Input` pin implementation for SAADC peripheral sampling from the
/// internal voltage.
pub struct VddInput;

impl_peripheral!(VddInput);
#[cfg(not(feature = "_nrf91"))]
impl_saadc_input!(@local, VddInput, VDD);
#[cfg(feature = "_nrf91")]
impl_saadc_input!(@local, VddInput, VDD_GPIO);

/// A dummy `Input` pin implementation for SAADC peripheral sampling from the
/// VDDH / 5 voltage.
#[cfg(any(feature = "_nrf5340-app", feature = "nrf52833", feature = "nrf52840"))]
pub struct VddhDiv5Input;

#[cfg(any(feature = "_nrf5340-app", feature = "nrf52833", feature = "nrf52840"))]
impl_peripheral!(VddhDiv5Input);

#[cfg(any(feature = "_nrf5340-app", feature = "nrf52833", feature = "nrf52840"))]
impl_saadc_input!(@local, VddhDiv5Input, VDDHDIV5);