//! When the resting-pose DWELL FALLBACK actually runs, does it pick a visible pose?
//!
//! `ui-resting-pose.md` argues the fallback is structurally unsound — the gap it
//! maximises is time spent *interpolating*, so neither endpoint is held. Its one
//! worked example, `GP_TITLE` build 7's `ptlogo_eff3.t32`, **no longer
//! discriminates**: under the corrected keyframe-record layout the longest gap
//! moved from `61→103` to `0→46`, and both ends of that are `a = 0`. The page's
//! listing still shows the stale parser's trailing `-`.
//!
//! Losing the example is not the same as closing the question, so: disc-wide, how
//! often does the fallback fire, and when it does, does it return something the
//! player would see? An element resting at `a = 0` is harmless whichever end the
//! rule lands on.
//!
//!     cargo run -p sylpheed-formats --example rest_fallback_census

use sylpheed_formats::{pak::PakArchive, ui_layout};
use std::path::PathBuf;

fn main() {
    let root = PathBuf::from(std::env::var("SYLPHEED_DISC").expect("SYLPHEED_DISC"));
    let mut paks: Vec<PathBuf> = std::fs::read_dir(root.join("dat"))
        .expect("dat/")
        .filter_map(|e| e.ok().map(|e| e.path()))
        .filter(|p| p.extension().is_some_and(|x| x == "pak"))
        .collect();
    paks.sort();

    let (mut elements, mut plateau, mut fallback, mut fb_visible) = (0usize, 0, 0, 0);
    let mut worst: Vec<(u32, String, String)> = Vec::new();
    let mut per_pak: std::collections::BTreeMap<String, (usize, usize)> = Default::default();
    for pak in &paks {
        let Ok(ar) = PakArchive::open(pak) else { continue };
        let name = pak.file_name().unwrap().to_string_lossy().to_string();
        for (i, e) in ar.entries().iter().enumerate() {
            let Ok(by) = ar.read(e) else { continue };
            let Some(b) = ui_layout::parse_build(&by) else { continue };
            for el in &b.elements {
                if el.keyframes.len() < 2 { continue }
                elements += 1;
                // a plateau is two ADJACENT poses that are equal — the same test
                // the plateau path makes before the fallback can run
                let has_plateau = el.keyframes.windows(2).any(|w| {
                    w[0].x == w[1].x && w[0].y == w[1].y
                        && w[0].scale_x == w[1].scale_x && w[0].scale_y == w[1].scale_y
                        && w[0].fade == w[1].fade
                });
                if has_plateau { plateau += 1; continue }
                fallback += 1;
                per_pak.entry(name.clone()).or_default().0 += 1;
                let Some(r) = el.rest() else { continue };
                let a = (r.fade >> 24) & 0xff;
                if a > 0 {
                    fb_visible += 1;
                    per_pak.entry(name.clone()).or_default().1 += 1;
                    worst.push((a, name.clone(), format!("e{i}/{}", el.name)));
                }
            }
        }
    }
    println!("POPULATION: {elements} elements with >= 2 keyframes, over {} archives", paks.len());
    println!("COVERAGE:   {plateau} have a plateau (fallback never runs)");
    println!("            {fallback} have NONE -> the dwell fallback decides");
    println!("            {fb_visible} of those rest at alpha > 0 -- i.e. VISIBLE\n");
    println!("PER ARCHIVE — fallback fires / of those, rests VISIBLE:");
    let mut rows: Vec<_> = per_pak.into_iter().collect();
    rows.sort_by(|a, b| b.1.1.cmp(&a.1.1));
    for (pak, (fires, vis)) in &rows {
        println!("   {pak:34} {fires:5} fires   {vis:5} visible");
    }
    println!();
    worst.sort_by(|a, b| b.0.cmp(&a.0));
    for (a, pak, el) in worst.iter().take(6) {
        println!("   a={a:3}  {pak}  {el}");
    }
    println!("\n--- END OF CENSUS (if this line is missing, the run did not finish) ---");
}