#[derive(Copy, Clone)]
pub struct Display {
    pub buf: [u8; Self::SCREEN_SIZE],
}

impl Display {
    const SCREEN_SIZE: usize = 64 * 32;

    pub fn clear(&mut self) {
        self.buf = [0x0; Self::SCREEN_SIZE]
    }

    pub fn draw_sprite(&mut self, coords: (u8, u8), data: &[u8]) -> bool {
        let x = coords.0;
        let y = coords.1;
        let mut set_vf = false;
        // Each Byte is a row, and there are n bytes in data
        // When writing, x should not change but y should be incremented
        // after each iteration in the loop.
        for (i, byte) in data.iter().enumerate() {
            // Access every bit of the byte
            for j in 0..8 {
                let bit = (byte >> j) & 0x01;
                let display_index = j as usize + 8 * i as usize;

                let old_value = self.buf[display_index];
                self.buf[display_index] ^= bit;

                if old_value == 0x01 && self.buf[display_index] == 0x00 {
                    set_vf = true;
                }
            }
        }

        set_vf
    }
}

impl Default for Display {
    fn default() -> Self {
        Display {
            buf: [0x0; Self::SCREEN_SIZE],
        }
    }
}

#[derive(Debug, Copy, Clone)]
pub struct Timer {
    remaining: u8,
    enabled: bool,
}

impl Default for Timer {
    fn default() -> Self {
        Timer {
            remaining: 0,
            enabled: false,
        }
    }
}

impl Timer {
    pub fn set(&mut self, secs: u8) {
        self.remaining = secs;
        self.enabled = true;
    }

    pub fn get(&self) -> u8 {
        self.remaining
    }

    pub fn tick(&mut self) {
        if self.enabled {
            self.remaining -= 1;

            if self.remaining == 0 {
                println!("Beep!");
                self.enabled = false;
            }
        }
    }
}

#[derive(Debug, Copy, Clone)]
pub struct Keypad {
    keys: [bool; 16],
}

impl Default for Keypad {
    fn default() -> Self {
        Self { keys: [false; 16] }
    }
}

impl Keypad {
    pub fn get_any_pressed(&self) -> Option<u8> {
        for (i, key) in self.keys.iter().enumerate() {
            if *key {
                return Some(i as u8);
            }
        }
        None
    }

    pub fn reset(&mut self) {
        self.keys = [false; 16];
    }

    pub fn get_overview(&self) -> [bool; 16] {
        self.keys
    }

    pub fn is_pressed(&self, key: u8) -> bool {
        self.keys[key as usize]
    }

    pub fn set_all(&mut self, keys: [bool; 16]) {
        self.keys = keys;
    }

    pub fn set_key(&mut self, index: usize) {
        self.keys[index] = true;
    }

    pub fn unset_key(&mut self, index: usize) {
        self.keys[index] = false;
    }
}