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use rusttype;

pub type Font = rusttype::Font<'static>;

pub struct Text {
    pub bytes: Vec<u8>,
    pub size: (u32, u32),
}

impl Text {
    pub fn new(text: &str, font: &Font, height: f32) -> Self {
        let scale = rusttype::Scale::uniform(height);
        let offset = rusttype::point(0.0, font.v_metrics(scale).ascent);
        let glyphs: Vec<_> = font.layout(text, scale, offset).collect();
        let width = glyphs.last().unwrap().pixel_bounding_box().unwrap().max.x;
        let height = height.ceil();
        let size = (width as u32, height as u32);
        let bytes = Text::render(&glyphs, size);
        Self { bytes, size }
    }

    fn render(glyphs: &[rusttype::PositionedGlyph], size: (u32, u32)) -> Vec<u8> {
        let width = size.0 as usize;
        let height = size.1 as usize;
        let mut bytes = vec![0_u8; 4 * width * height];
        let mapping_scale = 255.0;
        for glyph in glyphs.iter() {
            if let Some(bbox) = glyph.pixel_bounding_box() {
                glyph.draw(|x, y, alpha| {
                    let alpha = (alpha * mapping_scale + 0.5) as u8;
                    let x = x as i32 + bbox.min.x;
                    let y = y as i32 + bbox.min.y;
                    if alpha > 0 && x >= 0 && x < width as i32 && y >= 0 && y < height as i32 {
                        let i = (x as usize + y as usize * width) * 4;
                        bytes[i] = 255;
                        bytes[i + 1] = 255;
                        bytes[i + 2] = 255;
                        bytes[i + 3] = alpha;
                    }
                });
            }
        }
        bytes
    }
}