//! How many tied pairs can cost a pixel, as a function of TIME?
//!
//! `tie_break_pixel_cost` answers "at one pose". That leaves the answer looking
//! like it might be a knife-edge: pick a different instant and the count could
//! jump. This sweeps every keyframe time in the bundle and reports, per entry,
//! how many same-key pairs are simultaneously **opaque, non-collapsed and
//! overlapping** — the pairs whose order could possibly matter at that instant.
//!
//! The instrument's control is built in: the count at t=0 (nothing has faded in)
//! and the count at rest must bracket it, and an entry whose count is flat at
//! zero for the whole sweep would be suspicious rather than reassuring — so the
//! peak is printed too.
use sylpheed_formats::{pak, ui_layout};
use ui_layout::UiBuild;

fn rect(e: &ui_layout::Element, t: u32) -> Option<(i32, i32, i32, i32)> {
    let kf = e.pose_at(t)?;
    if kf.fade >> 24 == 0 || kf.scale_x == 0 || kf.scale_y == 0 {
        return None;
    }
    let (w, h) = ((e.pivot_x * 2) as i32, (e.pivot_y * 2) as i32);
    if w == 0 || h == 0 {
        return None;
    }
    Some((kf.x, kf.y, w, h))
}

fn live_pairs(b: &UiBuild, bytes: &[u8], keys: &[u32], t: u32) -> usize {
    let mut n = 0;
    for a in 0..keys.len() {
        for c in (a + 1)..keys.len() {
            if keys[a] != keys[c] || keys[a] == u32::MAX {
                continue;
            }
            let (Some(ra), Some(rb)) = (rect(&b.elements[a], t), rect(&b.elements[c], t)) else {
                continue;
            };
            if (ra.0 + ra.2).min(rb.0 + rb.2) - ra.0.max(rb.0) > 0
                && (ra.1 + ra.3).min(rb.1 + rb.3) - ra.1.max(rb.1) > 0
            {
                n += 1
            }
        }
    }
    n
}

fn main() {
    let path = std::env::args()
        .nth(1)
        .expect("usage: tie_cost_over_time <pak>");
    let ar = pak::PakArchive::open(&path).expect("open pak");
    println!("# tied pairs that could cost a pixel, over time — {path}\n");
    for (i, e) in ar.entries().to_vec().iter().enumerate() {
        let Ok(by) = ar.read(e) else { continue };
        let Some(b) = ui_layout::parse_build(&by) else {
            continue;
        };
        let keys: Vec<u32> = b
            .elements
            .iter()
            .map(|el| ui_layout::sprite_layer_key(&b, &by, el).unwrap_or(u32::MAX))
            .collect();
        let mut ts: Vec<u32> = b
            .elements
            .iter()
            .flat_map(|el| el.keyframes.iter().filter_map(|k| k.time))
            .collect();
        ts.sort_unstable();
        ts.dedup();
        if ts.len() < 2 {
            continue;
        }
        let last = *ts.last().unwrap();
        // sample every keyframe time AND every midpoint between them
        let mut samples: Vec<u32> = ts.clone();
        for w in ts.windows(2) {
            samples.push(w[0] + (w[1] - w[0]) / 2);
        }
        samples.sort_unstable();
        samples.dedup();
        let counts: Vec<(u32, usize)> = samples
            .iter()
            .map(|&t| (t, live_pairs(&b, &by, &keys, t)))
            .collect();
        let peak = counts.iter().map(|&(_, n)| n).max().unwrap_or(0);
        if peak == 0 {
            continue;
        }
        let Some((lo, hi)) = b.settle_window() else {
            continue;
        };
        let st = b.settle_time().unwrap();
        let at_settle = live_pairs(&b, &by, &keys, st);
        // the whole plateau, not just its midpoint
        let plateau: Vec<usize> = (lo..=hi)
            .step_by(((hi - lo).max(1) / 8).max(1) as usize)
            .map(|t| live_pairs(&b, &by, &keys, t))
            .collect();
        let pmax = plateau.iter().copied().max().unwrap_or(0);
        println!(
            "entry {i:2}  peak {peak} live pair(s) over t=0..{last}   \
settle window [{lo},{hi}]  at t={st}: {at_settle}   ACROSS THE WHOLE WINDOW: max {pmax}"
        );
        let busy: Vec<String> = counts
            .iter()
            .filter(|&&(_, n)| n > 0)
            .map(|&(t, n)| format!("t{t}:{n}"))
            .collect();
        if busy.len() <= 24 {
            println!("      live only at  {}", busy.join(" "));
        } else {
            println!(
                "      live at {} of {} sampled instants",
                busy.len(),
                counts.len()
            );
        }
    }
}