use ratatui::prelude::*;
use ratatui::widgets::Widget;

pub struct LineNumberWidget(pub usize, pub usize);

fn usize_to_hex(mut value: usize, buffer: &mut [u8; 64]) -> &str {
    const HEX: &[u8; 16] = b"0123456789ABCDEF";
    let len = std::mem::size_of_val(&value);

    for i in 0..len {
        let current_byte = value & 0xff;

        buffer[63 - 2 * i] = HEX[current_byte & 0x0f];
        buffer[63 - 2 * i - 1] = HEX[current_byte >> 4];

        value >>= 8;
    }

    unsafe { std::str::from_utf8_unchecked(&buffer[64 - len * 2..]) }
}

impl Widget for LineNumberWidget {
    fn render(self, area: Rect, buf: &mut Buffer) {
        let visible_lines = area.height as usize;
        let mut buffer = [b'0'; 64];

        let areas =
            Layout::vertical(vec![Constraint::Length(1); visible_lines.min(self.1)]).split(area);

        for (i, a) in areas.iter().enumerate() {
            Line::from(usize_to_hex(self.0 + i * 16, &mut buffer)).render(*a, buf);
        }
    }
}