//! # MCPWM Timer Module
//!
//! ## Overview
//! The `timer` module provides an interface to configure and use timers for
//! generating `PWM` signals used in motor control and other applications.

use core::marker::PhantomData;

use super::PeripheralGuard;
use crate::{
    mcpwm::{FrequencyError, PeripheralClockConfig, PwmClockGuard, PwmPeripheral},
    pac,
    time::Rate,
};

/// A MCPWM timer
///
/// Every timer of a particular [`MCPWM`](super::McPwm) peripheral can be used
/// as a timing reference for every
/// [`Operator`](super::operator::Operator) of that peripheral
pub struct Timer<const TIM: u8, PWM> {
    pub(super) phantom: PhantomData<PWM>,
    _guard: PeripheralGuard,
    _pwm_clock_guard: PwmClockGuard,
}

impl<const TIM: u8, PWM: PwmPeripheral> Timer<TIM, PWM> {
    pub(super) fn new(guard: PeripheralGuard) -> Self {
        Timer {
            phantom: PhantomData,
            _guard: guard,
            _pwm_clock_guard: PwmClockGuard::new::<PWM>(),
        }
    }

    /// Apply the given timer configuration.
    ///
    /// ### Note:
    /// The prescaler and period configuration will be applied immediately by
    /// default and before setting the [`PwmWorkingMode`].
    /// If the timer is already running you might want to call [`Timer::stop`]
    /// and/or [`Timer::set_counter`] first
    /// (if the new period is larger than the current counter value this will
    /// cause weird behavior).
    ///
    /// If configured via [`TimerClockConfig::with_period_updating_method`],
    /// another behavior can be applied. Currently, only
    /// [`PeriodUpdatingMethod::Immediately`]
    /// and [`PeriodUpdatingMethod::TimerEqualsZero`] are useful as the sync
    /// method is not yet implemented.
    ///
    /// The hardware supports writing these settings in sync with certain timer
    /// events but this HAL does not expose these for now.
    pub fn start(&mut self, timer_config: TimerClockConfig) {
        // write prescaler and period with immediate update method
        self.cfg0().write(|w| unsafe {
            w.prescale().bits(timer_config.prescaler);
            w.period().bits(timer_config.period);
            w.period_upmethod()
                .bits(timer_config.period_updating_method as u8)
        });

        // set timer to continuously run and set the timer working mode
        self.cfg1().write(|w| unsafe {
            w.start().bits(2);
            w.mod_().bits(timer_config.mode as u8)
        });
    }

    /// Stop the timer in its current state
    pub fn stop(&mut self) {
        // freeze the timer
        self.cfg1().write(|w| unsafe { w.mod_().bits(0) });
    }

    /// Set the timer counter to the provided value
    pub fn set_counter(&mut self, phase: u16, direction: CounterDirection) {
        // SAFETY:
        // We only write to our TIMERx_SYNC register
        let tmr = unsafe { Self::tmr() };
        let sw = tmr.sync().read().sw().bit_is_set();
        tmr.sync().write(|w| {
            w.phase_direction().bit(direction as u8 != 0);
            unsafe {
                w.phase().bits(phase);
            }
            w.sw().bit(!sw)
        });
    }

    /// Read the counter value and counter direction of the timer
    pub fn status(&self) -> (u16, CounterDirection) {
        // SAFETY:
        // We only read from our TIMERx_STATUS register
        let reg = unsafe { Self::tmr() }.status().read();
        (reg.value().bits(), reg.direction().bit_is_set().into())
    }

    fn cfg0(&mut self) -> &pac::mcpwm0::timer::CFG0 {
        // SAFETY:
        // We only grant access to our CFG0 register with the lifetime of &mut self
        unsafe { Self::tmr() }.cfg0()
    }

    fn cfg1(&mut self) -> &pac::mcpwm0::timer::CFG1 {
        // SAFETY:
        // We only grant access to our CFG0 register with the lifetime of &mut self
        unsafe { Self::tmr() }.cfg1()
    }

    unsafe fn tmr() -> &'static pac::mcpwm0::TIMER {
        let block = unsafe { &*PWM::block() };
        block.timer(TIM as usize)
    }
}

/// Clock configuration of a MCPWM timer
///
/// Use [`PeripheralClockConfig::timer_clock_with_prescaler`](super::PeripheralClockConfig::timer_clock_with_prescaler) or
/// [`PeripheralClockConfig::timer_clock_with_frequency`](super::PeripheralClockConfig::timer_clock_with_frequency) to it.
#[derive(Copy, Clone)]
pub struct TimerClockConfig {
    frequency: Rate,
    period: u16,
    period_updating_method: PeriodUpdatingMethod,
    prescaler: u8,
    mode: PwmWorkingMode,
}

impl TimerClockConfig {
    pub(super) fn with_prescaler(
        clock: &PeripheralClockConfig,
        period: u16,
        mode: PwmWorkingMode,
        prescaler: u8,
    ) -> Self {
        let cycle_period = match mode {
            PwmWorkingMode::Increase | PwmWorkingMode::Decrease => period as u32 + 1,
            // The reference manual seems to provide an incorrect formula for UpDown
            PwmWorkingMode::UpDown => period as u32 * 2,
        };
        let frequency = clock.frequency / (prescaler as u32 + 1) / cycle_period;

        TimerClockConfig {
            frequency,
            prescaler,
            period,
            period_updating_method: PeriodUpdatingMethod::Immediately,
            mode,
        }
    }

    pub(super) fn with_frequency(
        clock: &PeripheralClockConfig,
        period: u16,
        mode: PwmWorkingMode,
        target_freq: Rate,
    ) -> Result<Self, FrequencyError> {
        let cycle_period = match mode {
            PwmWorkingMode::Increase | PwmWorkingMode::Decrease => period as u32 + 1,
            // The reference manual seems to provide an incorrect formula for UpDown
            PwmWorkingMode::UpDown => period as u32 * 2,
        };
        let target_timer_frequency = target_freq
            .as_hz()
            .checked_mul(cycle_period)
            .ok_or(FrequencyError)?;
        if target_timer_frequency == 0 || target_freq > clock.frequency {
            return Err(FrequencyError);
        }
        let prescaler = clock.frequency.as_hz() / target_timer_frequency - 1;
        if prescaler > u8::MAX as u32 {
            return Err(FrequencyError);
        }
        let frequency = clock.frequency / (prescaler + 1) / cycle_period;

        Ok(TimerClockConfig {
            frequency,
            prescaler: prescaler as u8,
            period,
            period_updating_method: PeriodUpdatingMethod::Immediately,
            mode,
        })
    }

    /// Set the method for updating the PWM period
    pub fn with_period_updating_method(self, method: PeriodUpdatingMethod) -> Self {
        Self {
            period_updating_method: method,
            ..self
        }
    }

    /// Get the timer clock frequency.
    ///
    /// ### Note:
    /// The actual value is rounded down to the nearest `u32` value
    pub fn frequency(&self) -> Rate {
        self.frequency
    }
}

/// Method for updating the PWM period
#[derive(Clone, Copy)]
#[repr(u8)]
pub enum PeriodUpdatingMethod {
    /// The period is updated immediately.
    Immediately           = 0,
    /// The period is updated when the timer equals zero.
    TimerEqualsZero       = 1,
    /// The period is updated on a synchronization event.
    Sync                  = 2,
    /// The period is updated either when the timer equals zero or on a
    /// synchronization event.
    TimerEqualsZeroOrSync = 3,
}

/// PWM working mode
#[derive(Copy, Clone)]
#[repr(u8)]
pub enum PwmWorkingMode {
    /// In this mode, the PWM timer increments from zero until reaching the
    /// value configured in the period field. Once done, the PWM timer
    /// returns to zero and starts increasing again. PWM period is equal to the
    /// value of the period field + 1.
    Increase = 1,
    /// The PWM timer decrements to zero, starting from the value configured in
    /// the period field. After reaching zero, it is set back to the period
    /// value. Then it starts to decrement again. In this case, the PWM period
    /// is also equal to the value of period field + 1.
    Decrease = 2,
    /// This is a combination of the two modes mentioned above. The PWM timer
    /// starts increasing from zero until the period value is reached. Then,
    /// the timer decreases back to zero. This pattern is then repeated. The
    /// PWM period is the result of the value of the period field × 2.
    UpDown   = 3,
}

/// The direction the timer counter is changing
#[derive(Debug)]
#[repr(u8)]
pub enum CounterDirection {
    /// The timer counter is increasing
    Increasing = 0,
    /// The timer counter is decreasing
    Decreasing = 1,
}

impl From<bool> for CounterDirection {
    fn from(bit: bool) -> Self {
        match bit {
            false => CounterDirection::Increasing,
            true => CounterDirection::Decreasing,
        }
    }
}
