#![feature(used, const_fn)]
#![no_std]

#[macro_use]
extern crate cortex_m;
extern crate cortex_m_rt;
extern crate tm4c129x;

use core::cell::Cell;
use cortex_m::ctxt::Local;
use cortex_m::exception::Handlers as ExceptionHandlers;
use tm4c129x::interrupt::Handlers as InterruptHandlers;

const LED1: u8 = 0x10;
const LED2: u8 = 0x40;
const HV_PWM: u8 = 0x01;
const FV_PWM: u8 = 0x04;
const FBV_PWM: u8 = 0x01;

const PWM_LOAD: u16 = (/*pwmclk*/16_000_000u32 / /*freq*/100_000) as u16;

fn set_led(nr: u8, state: bool) {
    cortex_m::interrupt::free(|cs| {
        let gpio_k = tm4c129x::GPIO_PORTK.borrow(cs);
        if state {
            gpio_k.data.modify(|r, w| w.data().bits(r.data().bits() | nr))
        } else {
            gpio_k.data.modify(|r, w| w.data().bits(r.data().bits() & !nr))
        }
    });
}

fn set_hv_pwm(duty: u16) {
    cortex_m::interrupt::free(|cs| {
        let pwm0 = tm4c129x::PWM0.borrow(cs);
        pwm0._0_cmpa.write(|w| w.compa().bits(duty));
    });
}

fn set_fv_pwm(duty: u16) {
    cortex_m::interrupt::free(|cs| {
        let pwm0 = tm4c129x::PWM0.borrow(cs);
        pwm0._1_cmpa.write(|w| w.compa().bits(duty));
    });
}

fn set_fbv_pwm(duty: u16) {
    cortex_m::interrupt::free(|cs| {
        let pwm0 = tm4c129x::PWM0.borrow(cs);
        pwm0._2_cmpa.write(|w| w.compa().bits(duty));
    });
}

enum EmissionRange {
    Low,  // 22K
    Med,  // 22K//(200Ω + compensated diode)
    High  // 22K//(39Ω + uncompensated diode)
}

fn set_emission_range(range: EmissionRange) {
    cortex_m::interrupt::free(|cs| {
        let gpio_p = tm4c129x::GPIO_PORTP.borrow(cs);
        gpio_p.data.modify(|r, w| {
            let value = r.data().bits() & 0b100111;
            match range {
                EmissionRange::Low  => w.data().bits(value | 0b000000),
                EmissionRange::Med  => w.data().bits(value | 0b001000),
                EmissionRange::High => w.data().bits(value | 0b010000),
            }
        });
    });
}

fn main() {
    hprintln!("Hello, world!");

    cortex_m::interrupt::free(|cs| {
        let sysctl = tm4c129x::SYSCTL.borrow(cs);

        // Set up system timer
        let systick = tm4c129x::SYST.borrow(cs);
        systick.set_reload(systick.get_ticks_per_10ms());
        systick.enable_counter();
        systick.enable_interrupt();

        // Bring up GPIO ports F, G, K, P
        sysctl.rcgcgpio.modify(|_, w| {
            w.r5().bit(true)
             .r6().bit(true)
             .r9().bit(true)
             .r13().bit(true)
        });
        while !sysctl.prgpio.read().r5().bit() {}
        while !sysctl.prgpio.read().r6().bit() {}
        while !sysctl.prgpio.read().r9().bit() {}
        while !sysctl.prgpio.read().r13().bit() {}

        // Set up LEDs
        let gpio_k = tm4c129x::GPIO_PORTK.borrow(cs);
        gpio_k.dir.write(|w| w.dir().bits(LED1|LED2));
        gpio_k.den.write(|w| w.den().bits(LED1|LED2));

        // Set up gain and emission range control pins
        let gpio_p = tm4c129x::GPIO_PORTP.borrow(cs);
        gpio_p.dir.write(|w| w.dir().bits(0b111111));
        gpio_p.den.write(|w| w.den().bits(0b111111));

        // Set up PWMs
        let gpio_f = tm4c129x::GPIO_PORTF_AHB.borrow(cs);
        gpio_f.dir.write(|w| w.dir().bits(HV_PWM|FV_PWM));
        gpio_f.den.write(|w| w.den().bits(HV_PWM|FV_PWM));
        gpio_f.afsel.write(|w| w.afsel().bits(HV_PWM|FV_PWM));
        gpio_f.pctl.write(|w| unsafe { w.pmc0().bits(6).pmc2().bits(6) });

        let gpio_g = tm4c129x::GPIO_PORTG_AHB.borrow(cs);
        gpio_g.dir.write(|w| w.dir().bits(FBV_PWM));
        gpio_g.den.write(|w| w.den().bits(FBV_PWM));
        gpio_g.afsel.write(|w| w.afsel().bits(FBV_PWM));
        gpio_g.pctl.write(|w| unsafe { w.pmc0().bits(6) });

        sysctl.rcgcpwm.modify(|_, w| w.r0().bit(true));
        while !sysctl.prpwm.read().r0().bit() {}

        let pwm0 = tm4c129x::PWM0.borrow(cs);
        // HV_PWM
        pwm0._0_gena.write(|w| w.actload().zero().actcmpad().one());
        pwm0._0_load.write(|w| w.load().bits(PWM_LOAD));
        pwm0._0_cmpa.write(|w| w.compa().bits(0));
        pwm0._0_ctl.write(|w| w.enable().bit(true));
        // FV_PWM
        pwm0._1_gena.write(|w| w.actload().zero().actcmpad().one());
        pwm0._1_load.write(|w| w.load().bits(PWM_LOAD));
        pwm0._1_cmpa.write(|w| w.compa().bits(0));
        pwm0._1_ctl.write(|w| w.enable().bit(true));
        // FBV_PWM
        pwm0._2_gena.write(|w| w.actload().zero().actcmpad().one());
        pwm0._2_load.write(|w| w.load().bits(PWM_LOAD));
        pwm0._2_cmpa.write(|w| w.compa().bits(0));
        pwm0._2_ctl.write(|w| w.enable().bit(true));
        // Enable all at once
        pwm0.enable.write(|w| {
            w.pwm0en().bit(true)
             .pwm2en().bit(true)
             .pwm4en().bit(true)
        });

        set_emission_range(EmissionRange::Med);
        set_hv_pwm(PWM_LOAD/64);
        set_fv_pwm(PWM_LOAD/16);
        set_fbv_pwm(PWM_LOAD/8);
    });
}

use cortex_m::exception::SysTick;

extern fn sys_tick(ctxt: SysTick) {
    static ELAPSED: Local<Cell<u32>, SysTick> = Local::new(Cell::new(0));
    let elapsed = ELAPSED.borrow(&ctxt);

    elapsed.set(elapsed.get() + 1);
    if elapsed.get() % 100 == 0 {
        set_led(LED1, true);
        set_led(LED2, false);
    }
    if elapsed.get() % 100 == 50 {
        set_led(LED1, false);
        set_led(LED2, true);
    }
}

#[used]
#[link_section = ".rodata.exceptions"]
pub static EXCEPTIONS: ExceptionHandlers = ExceptionHandlers {
    sys_tick: sys_tick,
    ..cortex_m::exception::DEFAULT_HANDLERS
};

#[used]
#[link_section = ".rodata.interrupts"]
pub static INTERRUPTS: InterruptHandlers = InterruptHandlers {
    ..tm4c129x::interrupt::DEFAULT_HANDLERS
};