#![no_main]
#![no_std]

use heapless::{String, Vec};
use panic_probe as _;

use defmt_rtt as _; // global logger

use cortex_m_rt::entry;
use hal::{
    delay::Delay,
    gpio::{Output, PushPull, gpioa::*, gpiob::*, gpioc::*},
    pac,
    prelude::*,
    rcc::Config,
};
use hd44780_driver::HD44780;

#[defmt::panic_handler]
fn panic() -> ! {
    cortex_m::asm::udf()
}

type Lcd = HD44780<
    hd44780_driver::bus::FourBitBus<
        PA9<Output<PushPull>>,
        PC7<Output<PushPull>>,
        PB5<Output<PushPull>>,
        PB4<Output<PushPull>>,
        PB10<Output<PushPull>>,
        PA8<Output<PushPull>>,
    >,
>;

const FPS: u32 = 12;
const LINES: usize = 4;
const CHARS: usize = 20;
const SIGNS_LEN: usize = 7;
const SIGNS: [char; SIGNS_LEN] = ['N', 'e', 'w', 'T', 'e', 'c', ' '];

#[entry]
fn main() -> ! {
    let dp = pac::Peripherals::take().unwrap();
    let cp = cortex_m::Peripherals::take().unwrap();

    let mut rcc = dp.RCC.freeze(Config::hsi16());

    let gpioa = dp.GPIOA.split(&mut rcc);
    let gpiob = dp.GPIOB.split(&mut rcc);
    let gpioc = dp.GPIOC.split(&mut rcc);

    // literal D4-D7 ports etc as written on the nucleo board, mapped to the D4-D7 ports of the LCD
    // controller
    let d4 = gpiob.pb5.into_push_pull_output();
    let d5 = gpiob.pb4.into_push_pull_output();
    let d6 = gpiob.pb10.into_push_pull_output();
    let d7 = gpioa.pa8.into_push_pull_output();

    // clock enable on D9
    let en = gpioc.pc7.into_push_pull_output();
    // register select on D8, the lib wants that but I'd just put it on ground otherwise
    let rs = gpioa.pa9.into_push_pull_output();

    // See https://en.wikipedia.org/wiki/Hitachi_HD44780_LCD_controller#Interface
    // for the pins of the LCD

    let mut delay = cp.SYST.delay(rcc.clocks);

    let mut led = gpioa.pa5.into_push_pull_output();

    let mut lcd: Lcd = HD44780::new_4bit(rs, en, d4, d5, d6, d7, &mut delay)
        .expect("could not init HD44780 driver");
    lcd.set_display_mode(
        hd44780_driver::DisplayMode {
            cursor_visibility: hd44780_driver::Cursor::Invisible,
            cursor_blink: hd44780_driver::CursorBlink::Off,
            display: hd44780_driver::Display::On,
        },
        &mut delay,
    )
    .expect("could not set display properties");
    lcd.reset(&mut delay).expect("could not reset the lcd");

    let mut i: usize = 0;
    let mut buf: Vec<String<CHARS>, LINES> = Vec::new();

    loop {
        led.set_high().unwrap();

        reset_buf(&mut buf);
        animation(&mut buf, i);
        display(&buf, &mut lcd, &mut delay, i % LINES);

        led.set_low().unwrap();

        delay.delay_us(1_000_000 / FPS);
        i += 1;
    }
}

fn display<const LINES: usize, const CHARS: usize>(
    buf: &Vec<String<CHARS>, LINES>,
    lcd: &mut Lcd,
    delay: &mut Delay,
    which: usize,
) {
    match which {
        0 => {
            lcd.set_cursor_pos(0, delay)
                .expect("could not set cursor pos");
            lcd.write_str(&buf[0], delay)
                .expect("could not display string");
        }
        1 => {
            lcd.set_cursor_pos(60, delay)
                .expect("could not set cursor pos");
            lcd.write_str(&buf[1], delay)
                .expect("could not display string");
        }
        2 => {
            lcd.set_cursor_pos(20, delay)
                .expect("could not set cursor pos");
            lcd.write_str(&buf[2], delay)
                .expect("could not display string");
        }
        3 => {
            // line 4 is a bit weird and needs some offset
            let mut tmp: String<30> = String::new();
            tmp.push_str("    ").unwrap();
            tmp.push_str(&buf[3]).unwrap();
            lcd.set_cursor_pos(80, delay)
                .expect("could not set cursor pos");
            lcd.write_str(&tmp, delay)
                .expect("could not display string");
        }
        _ => unreachable!(),
    }
}

fn animation<const LINES: usize, const CHARS: usize>(
    buf: &mut Vec<String<CHARS>, LINES>,
    frame: usize,
) {
    for i in 0..CHARS {
        for (bi, buf) in buf.iter_mut().enumerate() {
            match buf.push(SIGNS[(i + bi * 2 + frame) % SIGNS_LEN]) {
                Ok(_) => (),
                Err(_e) => {
                    panic!("Could not push string in animation. i={}, bi={}", i, bi);
                }
            }
        }
    }
}

fn reset_buf<const LINES: usize, const CHARS: usize>(buf: &mut Vec<String<CHARS>, LINES>) {
    buf.clear();
    for _ in 0..LINES {
        buf.push(String::new()).unwrap();
    }
}