//!
//! Based on an example from https://github.com/jamwaffles/ssd1306
//! Sends random raw data to the display, emulating an old untuned TV.
//! Retrieves the underlying display properties struct and allows calling of the
//! low-level `draw()` method, sending a 1024 byte buffer straight to the
//! display.
//!
//! Uses SmallRng as random number generator.
//! NOTE: these are pseudorandom numbers, not suitable for cryptographic or
//! similar purposes.

#![no_std]
#![no_main]

use arduino_nano33iot as bsp;
use bsp::hal;

use rand;
use ssd1306;

#[cfg(not(feature = "use_semihosting"))]
use panic_halt as _;
#[cfg(feature = "use_semihosting")]
use panic_semihosting as _;

use bsp::entry;
use hal::clock::GenericClockController;
use hal::delay::Delay;
use hal::pac::{CorePeripherals, Peripherals};
use hal::prelude::*;
use hal::time::KiloHertz;

use ssd1306::{prelude::*, I2CDisplayInterface, Ssd1306};

use rand::prelude::*;

const BOOT_DELAY_MS: u16 = 100; //small delay for the I2C to initiate correctly and start on boot without
                                // having to reset the board

#[entry]
fn main() -> ! {
    let mut peripherals = Peripherals::take().unwrap();
    let core = CorePeripherals::take().unwrap();
    let mut clocks = GenericClockController::with_internal_32kosc(
        peripherals.GCLK,
        &mut peripherals.PM,
        &mut peripherals.SYSCTRL,
        &mut peripherals.NVMCTRL,
    );
    let pins = bsp::Pins::new(peripherals.PORT);
    let mut delay = Delay::new(core.SYST, &mut clocks);

    delay.delay_ms(BOOT_DELAY_MS);

    let i2c = bsp::i2c_master(
        &mut clocks,
        KiloHertz(400),
        peripherals.SERCOM4,
        &mut peripherals.PM,
        pins.sda,
        pins.scl,
    );

    let interface = I2CDisplayInterface::new(i2c);
    let mut disp = Ssd1306::new(interface, DisplaySize128x64, DisplayRotation::Rotate0)
        .into_buffered_graphics_mode();
    disp.init().unwrap();

    let mut buf = [0x00u8; 512]; //each line has 128 pixels, that's 8 bytes, x 32 lines = 512 bytes for the
                                 // whole display

    let mut rng = SmallRng::seed_from_u64(0x0101_0303_0808_0909);

    loop {
        rng.fill_bytes(&mut buf); // repeatedly fills the display buffer with randomly generated bytes
        disp.bounded_draw(
            &buf,
            DisplaySize128x64::WIDTH.into(),
            (0, 0),
            (DisplaySize128x64::WIDTH, DisplaySize128x64::HEIGHT),
        )
        .unwrap();
        disp.flush().unwrap();
    }
}