//! hexwork-render: camera → raycast/DDA → glyph+color buffer → ANSI diff.
//! Render thread reads triple-buffered snapshots; sim never blocks on render.
//! Full spec: docs/05-renderer-spec.md.

pub mod ansi;
pub mod camera;
pub mod env;
pub mod palette;
mod production;
pub mod projection;
pub mod ray;
pub mod scene;
pub mod shade;
pub mod snapshot;
mod transfer;

/// Distance density ramp, near → far (docs/05 §5.1).
pub const DENSITY_RAMP: &[char] = &['█', '▓', '▒', '░', '=', '-', ':', '.', '·', ' '];

/// Map a 0.0–1.0 distance fraction to a density glyph.
pub fn density_glyph(frac: f32) -> char {
    let f = frac.clamp(0.0, 1.0);
    let i = (f * (DENSITY_RAMP.len() - 1) as f32).round() as usize;
    DENSITY_RAMP[i]
}

/// One cell of the frame buffer: glyph + truecolor fg/bg.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Cell {
    pub glyph: char,
    pub fg: [u8; 3],
    pub bg: [u8; 3],
}

impl Default for Cell {
    fn default() -> Self {
        Self {
            glyph: ' ',
            fg: [0, 0, 0],
            bg: [0, 0, 0],
        }
    }
}

/// Frame buffer: W×H cells, pooled and reused (zero hot-path allocs).
#[derive(Clone, Debug)]
pub struct FrameBuffer {
    pub w: usize,
    pub h: usize,
    pub cells: Vec<Cell>,
}

impl FrameBuffer {
    pub fn new(w: usize, h: usize) -> Self {
        Self {
            w,
            h,
            cells: vec![Cell::default(); w * h],
        }
    }

    pub fn clear(&mut self) {
        for c in self.cells.iter_mut() {
            *c = Cell::default();
        }
    }

    /// Count cells differing from a previous frame (for ANSI diff budgets).
    pub fn diff_count(&self, prev: &FrameBuffer) -> usize {
        assert_eq!((self.w, self.h), (prev.w, prev.h));
        self.cells
            .iter()
            .zip(prev.cells.iter())
            .filter(|(a, b)| a != b)
            .count()
    }
}

/// Which camera views the same sim (docs/05 §5.1).
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Camera {
    FirstPerson,
    ChaseOrbit,
    TopTactical,
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn ramp_endpoints() {
        assert_eq!(density_glyph(0.0), '█');
        assert_eq!(density_glyph(1.0), ' ');
    }

    #[test]
    fn identical_frames_diff_zero() {
        let a = FrameBuffer::new(80, 24);
        let b = FrameBuffer::new(80, 24);
        assert_eq!(a.diff_count(&b), 0);
    }
}