#![cfg_attr(test, allow(unused_imports))]
#![cfg_attr(not(test), no_std)]
#![cfg_attr(not(test), no_main)]
#![feature(half_open_range_patterns)]
#![feature(exclusive_range_pattern)]
#![feature(destructuring_assignment)]
#![allow(dead_code)]

// custom panic handler
#[cfg(not(test))]
use core::panic::PanicInfo;

use core::{cell::RefCell, ops::DerefMut};
use cortex_m::interrupt::{Mutex, free};
use stm32l4xx_hal::{delay::Delay, device::{I2C1, TIM2, TIM7}, gpio::{
        Alternate, Edge, Floating, Input, OpenDrain, Output, PullUp, PushPull, AF4, PA3, PB5, PC15,
    }, gpio::{State, PA10, PA9}, i2c::I2c, prelude::*, rcc, rng::Rng, timer::{Timer, Event}};

mod ds3231;
mod nixie;
mod pca9685;
mod tusb322;

use nixie::*;

type FaultLed = PC15<Output<PushPull>>;
static FAULT_LED: Mutex<RefCell<Option<FaultLed>>> = Mutex::new(RefCell::new(None));

#[rtic::app(device = stm32l4xx_hal::pac, peripherals = true)]
const APP: () = {
    struct Resources {
        #[init(Clock::default())]
        clock: Clock,

        // Late initialized resources (shared peripherals)
        rtc_int: PB5<Input<Floating>>,
        fault_int: PA3<Input<PullUp>>,
        i2c: I2c<I2C1, (PA9<Alternate<AF4, Output<OpenDrain>>>,PA10<Alternate<AF4,Output<OpenDrain>>>)>,
        refresh_timer: Timer<TIM2>,
        cycle_timer: Timer<TIM7>,
        delay_timer: Delay,
        rng: Rng,
    }

    #[init(spawn = [start_cycle])]
    fn init(ctx: init::Context) -> init::LateResources {
        let mut dp = ctx.device;
        let cp = ctx.core;

        // Consume the raw peripheral and return a new object that implements a higher level API
        let mut flash = dp.FLASH.constrain();
        let mut rcc = dp.RCC.constrain();
        let mut pwr = dp.PWR.constrain(&mut rcc.apb1r1);

        // Configure clocks to run at maximum frequency off internal oscillator
        let clocks = rcc
            .cfgr
            .pll_source(rcc::PllSource::HSI16)
            .sysclk(64.mhz())
            .hclk(64.mhz())
            .pclk1(64.mhz())
            .pclk2(64.mhz())
            .hsi48(true)
            .freeze(&mut flash.acr, &mut pwr);

        // Configure delay timer that operates off systick timer
        let mut delay_timer = Delay::new(cp.SYST, clocks);

        // Split GPIO peripheral into independent pins and registers
        let mut gpioa = dp.GPIOA.split(&mut rcc.ahb2);
        let mut gpiob = dp.GPIOB.split(&mut rcc.ahb2);
        let mut gpioc = dp.GPIOC.split(&mut rcc.ahb2);

        // Configure high voltage PSU enable pin on PA2
        let mut hv_enable = gpioa.pa2.into_push_pull_output_with_state(&mut gpioa.moder, &mut gpioa.otyper, State::Low);

        // Configure serial port
        // let tx = gpiob.pb6.into_af7(&mut gpiob.moder, &mut gpiob.afrl);
        // let rx = gpiob.pb7.into_af7(&mut gpiob.moder, &mut gpiob.afrl);
        // let _serial = Serial::usart1(
        //     dp.USART1,
        //     (tx, rx),
        //     Config::default().baudrate(115_200.bps()),
        //     clocks,
        //     &mut rcc.apb2,
        // );

        // Configure fault LED output on PC15
        let fault_led = gpioc.pc15.into_push_pull_output_with_state(&mut gpioc.moder, &mut gpioc.otyper, State::Low);

        // Store fault LED in static singleton so that it's accessible from anywhere
        free(|cs| {
            FAULT_LED.borrow(cs).replace(Some(fault_led));
        });

        // Configure fault input interrupt on PA3
        let mut fault_int = gpioa.pa3.into_pull_up_input(&mut gpioa.moder, &mut gpioa.pupdr);
        fault_int.make_interrupt_source(&mut dp.SYSCFG, &mut rcc.apb2);
        fault_int.enable_interrupt(&mut dp.EXTI);
        fault_int.trigger_on_edge(&mut dp.EXTI, Edge::FALLING);

        // Sanity check that fault pin isn't already set (active low)
        if fault_int.is_low().unwrap() {
            panic!();
        }

        // Enable RNG peripheral
        let rng = dp.RNG.enable(&mut rcc.ahb2, clocks);

        // Configure I2C SCL pin
        let scl = gpioa.pa9.into_open_drain_output(&mut gpioa.moder, &mut gpioa.otyper);
        let scl = scl.into_af4(&mut gpioa.moder, &mut gpioa.afrh);

        // Configure I2C SDA pin
        let sda = gpioa.pa10.into_open_drain_output(&mut gpioa.moder, &mut gpioa.otyper);
        let sda = sda.into_af4(&mut gpioa.moder, &mut gpioa.afrh);

        // Initialize I2C (configured for 1Mhz, but actually runs at 600kHz)
        let mut i2c = I2c::i2c1(dp.I2C1, (scl, sda), 1.mhz(), clocks, &mut rcc.apb1r1);

        // Initialize TUSB322 (USB Type-C configuration chip)
        tusb322::init(TUSB322_ADDR, &mut i2c);

        // Initialize DS3231 (RTC)
        ds3231::init(DS3231_ADDR, &mut i2c);

        // ds3231::set_date(DS3231_ADDR, &mut i2c, ds3231::Weekday::Wednesday, 15, 9, 21, 20);
        // ds3231::set_time(DS3231_ADDR, &mut i2c, 00, 37, 12);

        // Configure input interrupt pin from DS3231 on PB5
        // Interrupt is pulled high, with open drain on DS3231 
        // Interrupt enable is automatically handled by RTIC's #[task]
        let mut rtc_int = gpiob.pb5.into_floating_input(&mut gpiob.moder, &mut gpiob.pupdr);
        rtc_int.make_interrupt_source(&mut dp.SYSCFG, &mut rcc.apb2);
        rtc_int.enable_interrupt(&mut dp.EXTI);
        rtc_int.trigger_on_edge(&mut dp.EXTI, Edge::FALLING);

        // Configure DAC AMP enable pin for AD8591 on PB1
        let mut _dac_enable = gpiob.pb1.into_push_pull_output_with_state(&mut gpiob.moder, &mut gpiob.otyper, State::High);

        // Configure DAC VIN for AD8591 on PA5
        // Note that this pin should actually be configured as analog output (for DAC)
        // but stm32l4xx_hal doesn't have support for the DAC as of now. We also currently
        // set the output to only the highest possible voltage, so the same functionality
        // can be achieved by configuring the pin as a digital output set to high.
        let mut _dac_output = gpioa.pa5.into_push_pull_output_with_state(&mut gpioa.moder, &mut gpioa.otyper, State::High);

        // Configure PWM enable pin (active low) for PCA9685 on PA7
        let mut pwm_enable = gpioa.pa7.into_push_pull_output_with_state(&mut gpioa.moder, &mut gpioa.otyper, State::High);

        // Initialize the PCA9685 display refresh timer
        // Interrupt enable is automatically handled by RTIC's #[task]
        let refresh_timer = Timer::tim2(dp.TIM2, nixie::DISPLAY_REFRESH_FPS.hz(), clocks, &mut rcc.apb1r1);

        // Initiaize display cycle timer
        // Interrupt enable is automatically handled by RTIC's #[task]
        let cycle_timer = Timer::tim7(dp.TIM7, (1000 / nixie::CYCLE_FADE_DURATION_MS).hz(), clocks, &mut rcc.apb1r1);

        // Small delay to ensure that PCA9685 is fully powered on before writing to it
        delay_timer.delay_us(10_u32);

        // Initialize PCA9685 (PWM driver)
        pca9685::init(PCA9685_ALL_CALL, &mut i2c);

        // Enable PWM output after PCA9685 has been initialized
        pwm_enable.set_low().unwrap();

        // Enable the high voltage power supply last
        hv_enable.set_high().unwrap();

        // Spawn tasks to cycle through all tubes on powerup
        ctx.spawn.start_cycle(0).unwrap();
        ctx.spawn.start_cycle(1).unwrap();
        ctx.spawn.start_cycle(2).unwrap();
        ctx.spawn.start_cycle(3).unwrap();

        init::LateResources { rtc_int, fault_int, i2c, refresh_timer, cycle_timer, delay_timer, rng }
    }

    #[idle(spawn = [start_cycle], resources = [delay_timer, rng])]
    fn idle(ctx: idle::Context) -> ! {
        let idle::Resources {delay_timer, rng} = ctx.resources;

        loop {
            // Delay before cycling digits to prevent cathode poisoning
            delay_timer.delay_ms(CYCLE_REFRESH_INTERVAL * 1000);

            // Choose a random tube to cycle
            let tube = (rng.get_random_data() % 4) as usize;
            ctx.spawn.start_cycle(tube).unwrap();
        }
    }

    // Interrupt handler for 1HZ signal from offchip RTC (DS3231)
    #[task(binds = EXTI9_5, priority = 1, resources = [clock, rtc_int, i2c, refresh_timer])]
    fn rtc_interrupt(ctx: rtc_interrupt::Context) {
        let rtc_interrupt::Resources {mut clock, rtc_int, mut i2c, mut refresh_timer} = ctx.resources;

        let (mut second, mut minute, mut hour) = (0, 0, 0);
        let (mut weekday, mut day, mut month) = (ds3231::Weekday::Sunday, 0, 0);

        // Lower priority task requires a critical section to access shared peripheral
        i2c.lock(|i2c| {
            // Read new time from DS3231
            (second, minute, hour) = ds3231::get_time(DS3231_ADDR, i2c);
            (weekday, day, month, ..) = ds3231::get_date(DS3231_ADDR, i2c);
        });

        // Calculate new values and account for DST
        let hour = if ds3231::in_dst(weekday, day, month, hour) { (hour + 1) % 12 } else { hour % 12 };
        let hour = if hour == 0 { 12 } else { hour };

        // Lower priority task requires a critical section to access shared peripheral
        clock.lock(|clock| {
            // Trigger the processing of a new time value
            clock.rtc_tick(second, minute, hour);
        });

        // Start the refresh timer to update the display
        // Lower priority task requires a critical section to access shared peripheral
        refresh_timer.lock(|refresh_timer| {
            refresh_timer.listen(Event::TimeOut);
        });
        
        // Clear the interrupt flag for the timer
        rtc_int.clear_interrupt_pending_bit();
    }

    // Interrupt handler for fault interrupt from USB monitor (TUSB322)
    // Configured as priority 4 for highest priority (pre-empts all other interrupts)
    #[task(binds = EXTI3, priority = 4, resources = [fault_int])]
    fn fault_interrupt(ctx: fault_interrupt::Context) {
        let fault_interrupt::Resources {fault_int} = ctx.resources;

        if fault_int.check_interrupt() {
            fault_int.clear_interrupt_pending_bit();
            panic!();
        }
    }

    // Interrupt handler for internal timer that drives display refresh rate
    #[task(binds = TIM2, priority = 3, resources = [clock, i2c, refresh_timer])]
    fn refresh_interrupt(ctx: refresh_interrupt::Context) {
        let refresh_interrupt::Resources {clock, refresh_timer, i2c} = ctx.resources;

        // Compute updates for non-static digits
        let updated = clock.fps_tick();

        // Write new values if values have changed, otherwise disable the refresh timer
        if updated {
            clock.write_i2c(i2c);
            refresh_timer.clear_interrupt(Event::TimeOut);
        } else {
            refresh_timer.unlisten(Event::TimeOut);
        }
    }

    // Interrupt handler for internal timer that drives individual digits within a cycle sequence
    #[task(binds = TIM7, priority = 2, resources = [clock, refresh_timer, cycle_timer])]
    fn cycle_interrupt(ctx: cycle_interrupt::Context) {
        let cycle_interrupt::Resources {mut clock, mut refresh_timer, cycle_timer} = ctx.resources;
        let mut cycle_ended = true;

        // Lower priority task requires a critical section to access shared data
        clock.lock(|clock| {
            cycle_ended = clock.cycle_tick();
        });

        // Trigger the next step in the cycling sequence
        if cycle_ended {
            cycle_timer.unlisten(Event::TimeOut);
        } else {
            cycle_timer.clear_interrupt(Event::TimeOut);
        }

        // Start the refresh timer to update the display
        // Lower priority task requires a critical section to access shared peripheral
        refresh_timer.lock(|refresh_timer| {
            refresh_timer.listen(Event::TimeOut);
        });
    }

    // Trigger the start of a new cycle sequence
    #[task(resources = [clock, cycle_timer], priority = 2, capacity = 4)]
    fn start_cycle(ctx: start_cycle::Context, tube: usize) {
        let start_cycle::Resources {mut clock, cycle_timer} = ctx.resources;

        // Lower priority task requires a critical section to access shared data
        clock.lock(|clock| {
            // Trigger the start of a cycling sequence
            clock.cycle_start(tube);
        });

        // Start the timer to cycle through individual digits
        cycle_timer.listen(Event::TimeOut);
    }

    // RTIC requires that unused interrupts are declared in an extern block when
    // using software tasks; these free interrupts will be used to dispatch the
    // software tasks.
    extern "C" {
        fn TSC();
        fn LCD();
        fn AES();
    }
};

// Helper function to set onboard LED state
fn set_fault_led(state: State) {
    free(|cs| {
        let mut led_ref = FAULT_LED.borrow(cs).borrow_mut();
        if let Some(ref mut led) = led_ref.deref_mut() {
            match state {
                State::High => led.set_high().unwrap(),
                State::Low => led.set_low().unwrap(),
            };
        }
    });
}

// Custom panic handler
#[panic_handler]
#[cfg(not(test))]
fn panic(_info: &PanicInfo) -> ! {
    set_fault_led(State::High);
    loop {
        continue;
    }
}