use stm32f4xx_hal::pac;
use stm32f4xx_hal::rcc::Enable;
use stm32f4xx_hal::{
    pac::{ADC2, NVIC},
    gpio::{Analog, Output, PushPull, gpioa::PA3, gpiod::PD9},
    interrupt,
};
use uom::si::{
    electric_potential::millivolt,
    f64::ElectricPotential,
    ratio::ratio
};

// 12 bit Resolution
const MAX_SAMPLE: u16 = 4095;
pub type LdPwrEnPinType = PD9<Output<PushPull>>;
pub type PdMonAdcPinType = PA3<Analog>;
const PD_MON_ADC_CH_ID: u8 = 0x03;

static mut LD_PWR_EXC_PROTECTOR: Option<LdPwrExcProtector> = None;

pub struct LdPwrExcProtectorPhy {
    // To make sure Pd Mon Pin is configured to Analog mode
    pub _pd_mon_ch0: PdMonAdcPinType, 
    pub pwr_en_ch0:  LdPwrEnPinType,
}

#[derive(Clone)]
pub struct Status {
    pub pwr_excursion: bool,
    pub v_tripped: ElectricPotential,
    pub pwr_engaged: bool,
    pub v: ElectricPotential,
}

impl Default for Status {
    fn default() -> Self {
        Status {
            pwr_excursion: false,
            v_tripped: ElectricPotential::new::<millivolt>(0.0),
            pwr_engaged: false,
            v: ElectricPotential::new::<millivolt>(0.0),
        }
    }
}

pub struct LdPwrExcProtector {
    pac: ADC2,
    phy: LdPwrExcProtectorPhy,
    alarm_status: Status,
    calibrated_vdda: u32, 
}

impl LdPwrExcProtector {
    /// ADC Analog Watchdog is configured to guard a single regular Adc channel on Pd Mon Pin.
    /// ADC is configured to start continuous conversion without using DMA immediately.
    /// Interrupt is disabled by default.
    pub fn setup(pac_adc: ADC2, mut phy: LdPwrExcProtectorPhy){
        unsafe {
            // All ADCs share the same reset interface.
            // NOTE(unsafe) this reference will only be used for atomic writes with no side effects.
            let rcc = &(*pac::RCC::ptr());
            // Enable the ADC2 Clock
            pac::ADC2::enable(rcc);
            // Enable ADC Interrupt
            NVIC::unmask(interrupt::ADC);
        }

        pac_adc.cr1.reset();
        pac_adc.cr2.reset();
        pac_adc.sqr1.reset();
        pac_adc.sqr2.reset();
        pac_adc.sqr3.reset();
        
        pac_adc.cr1.write(|w| w
            // 12 Bit Resolution
            .res().twelve_bit()
            // Set Analog Watchdog to guard Single Regular Channel
            .awden().enabled()
            .awdsgl().single_channel()
            .jawden().disabled()
            // Disable Analog Watchdog Interrupt
            .awdie().disabled()
            // Set Analog Watchdog to monitor Pd Mon Pin
            .awdch().variant(PD_MON_ADC_CH_ID)
        );
        pac_adc.cr2.write(|w| w
            // Continous Conversion Mode
            .cont().set_bit()
            // Power up ADC
            .adon().set_bit()
            // Set data alignment to the right
            .align().right()
            // End of conversion selection: Each Sequence
            .eocs().each_sequence()
            .exten().disabled()
            .extsel().tim1cc1()
        );
        // Set the Conversion Sequence to include Pd Mon Pin
        pac_adc.sqr3.write(|w| w
            .sq1().variant(PD_MON_ADC_CH_ID)
        );
        // Set all sampling channels to have fastest sampling interval
        pac_adc.smpr1.reset();
        pac_adc.smpr2.reset();
        
        // Set the higher threshold to be max value initially
        pac_adc.htr.write(|w| w.ht().variant(MAX_SAMPLE));
        // Set the lower threshold to be min value initially
        pac_adc.ltr.write(|w| w.lt().variant(0));

        // SWStart should only be set when ADON = 1. Otherwise no conversion is launched.
        pac_adc.cr2.modify(|_, w| w
            .swstart().set_bit()
        );

        phy.pwr_en_ch0.set_low();

        unsafe {
            LD_PWR_EXC_PROTECTOR = Some(
                LdPwrExcProtector { 
                    pac: pac_adc, 
                    phy: phy,
                    alarm_status: Status::default(),
                    calibrated_vdda: 3300,
                }
            );
        }
    }

    fn get() -> Option<&'static mut Self> {
        unsafe { LD_PWR_EXC_PROTECTOR.as_mut() }
    }

    fn convert_sample_to_volt(sample :u16) -> ElectricPotential {
        if let Some(ref mut wdg ) = LdPwrExcProtector::get() {
            return ElectricPotential::new::<millivolt>(((u32::from(sample) * wdg.calibrated_vdda) / u32::from(MAX_SAMPLE)) as f64)
        }
        ElectricPotential::new::<millivolt>(0.0)
    }

    pub fn set_trigger_threshold_v(htr: ElectricPotential){
        if let Some(ref mut wdg ) = LdPwrExcProtector::get() {
            let code: u32 = ((htr / (ElectricPotential::new::<millivolt>(wdg.calibrated_vdda as f64))).get::<ratio>() * (MAX_SAMPLE as f64)) as u32;
            wdg.pac.htr.write(|w| unsafe {w.bits(code)});
        }
    }

    pub fn set_calibrated_vdda(val: u32) {
        if let Some(ref mut wdg ) = LdPwrExcProtector::get() {
            wdg.calibrated_vdda = val;
        }
    }

    pub fn get_status() -> Status {
        if let Some(ref mut wdg ) = LdPwrExcProtector::get() {
            wdg.alarm_status.v = LdPwrExcProtector::convert_sample_to_volt(wdg.pac.dr.read().data().bits());
            return wdg.alarm_status.clone()
        }
        Status::default()
    }

    pub fn pwr_on_and_arm_protection(){
        if let Some(ref mut wdg ) = LdPwrExcProtector::get() {
            wdg.alarm_status = Status::default();
            LdPwrExcProtector::pwr_on();
            // Interrupt should be enabled after power on to tackle the following edge case:
            //      Pd_Mon pin voltage has already exceed threshold before LD Power is on.
            LdPwrExcProtector::enable_watchdog_interrupt();
        }
    }

    pub fn clear_alarm_status(){
        if let Some(ref mut wdg ) = LdPwrExcProtector::get() {
            wdg.alarm_status.pwr_excursion = false;
            wdg.alarm_status.v_tripped = ElectricPotential::new::<millivolt>(0.0);
        }
    }

    fn enable_watchdog_interrupt(){
        if let Some(ref mut wdg ) = LdPwrExcProtector::get() {
            wdg.pac.cr1.modify(|_, w| w
                .awdie().set_bit()
            );
        }
    }

    fn disable_watchdog_interrupt(){
        if let Some(ref mut wdg ) = LdPwrExcProtector::get() {
            wdg.pac.cr1.modify(|_, w| w
                .awdie().clear_bit()
            );
        }
    }

    fn clear_interrupt_bit(){
        if let Some(ref mut wdg ) = LdPwrExcProtector::get() {
            wdg.pac.sr.modify(|_, w| w
                .awd().clear_bit()
            );
        }
    }

    fn pwr_on(){
        if let Some(ref mut wdg ) = LdPwrExcProtector::get() {
            wdg.alarm_status.pwr_engaged = true;
            wdg.phy.pwr_en_ch0.set_high()
        }
    }

    pub fn pwr_off(){
        if let Some(ref mut wdg ) = LdPwrExcProtector::get() {
            wdg.alarm_status.pwr_engaged = false;
            wdg.phy.pwr_en_ch0.set_low()
        }
    }

    fn pwr_excursion_handler(){
        if let Some(ref mut wdg ) = LdPwrExcProtector::get() {
            let sample = wdg.pac.dr.read().data().bits();
            LdPwrExcProtector::pwr_off();
            wdg.alarm_status.pwr_excursion = true;
            wdg.alarm_status.v_tripped = LdPwrExcProtector::convert_sample_to_volt(sample);
        }
    }
}

#[interrupt]
fn ADC(){
    cortex_m::interrupt::free(|_| {
            LdPwrExcProtector::pwr_excursion_handler();
            // Disable interrupt to avoid getting stuck in infinite loop
            LdPwrExcProtector::disable_watchdog_interrupt();
            LdPwrExcProtector::clear_interrupt_bit();
        }
    )
}