//! An OPAQUE full-screen primitive cannot paint on top of elements that are
//! visible at the same time — the screen would be blank.
//!
//! That is a constraint read off the file, not a preference. For each keyless
//! primitive this computes the interval over which it is opaque, and the interval
//! over which any OTHER element is visible, and reports the overlap.
//!
//! The falsifier: `pteff00.prm` is MEASURED painting last on the title and the
//! main menu. If any of its instances is opaque while content is up, the
//! constraint is wrong and this whole line is dead.
use sylpheed_formats::{pak, ratc, ui_layout};

/// Interval(s) where alpha >= `thr`, sampled at every half unit.
fn opaque_span(el: &ui_layout::Element, thr: u32, tmax: u32) -> Vec<(f64, f64)> {
    let mut out = Vec::new();
    let mut cur: Option<f64> = None;
    let mut t = 0.0;
    while t <= tmax as f64 {
        let a = el.pose_at(t as u32).map(|k| k.fade >> 24).unwrap_or(0);
        if a >= thr {
            if cur.is_none() {
                cur = Some(t)
            }
        } else if let Some(s) = cur.take() {
            out.push((s, t));
        }
        t += 0.5;
    }
    if let Some(s) = cur {
        out.push((s, tmax as f64))
    }
    out
}

fn main() {
    let root =
        std::env::var("SYLPHEED_DISC").expect("set SYLPHEED_DISC to the extracted disc root");
    let mut paks: Vec<_> = std::fs::read_dir(format!("{root}/dat"))
        .expect("dat/")
        .flatten()
        .map(|e| e.path())
        .filter(|p| p.extension().and_then(|s| s.to_str()) == Some("pak"))
        .collect();
    paks.sort();
    let want = [
        "pteff00.prm",
        "pgloading_eff00.prm",
        "palogo_eff0.prm",
        "pfbase.tbm",
        "pteff02.prm",
        "pzeff00.prm",
        "pceff00.prm",
        "pdeff00.prm",
    ];
    println!(
        "{:>22} {:>5}  {:>16}  {:>18}  overlap",
        "primitive", "entry", "opaque while", "content visible"
    );
    for p in &paks {
        let Ok(ar) = pak::PakArchive::open(p) else {
            continue;
        };
        for (ei, e) in ar.entries().iter().enumerate() {
            let Ok(by) = ar.read(e) else { continue };
            if !ratc::is_ratc(&by) {
                continue;
            }
            let Some(b) = ui_layout::parse_build(&by) else {
                continue;
            };
            let tmax = b
                .elements
                .iter()
                .flat_map(|el| el.keyframes.iter().filter_map(|k| k.time))
                .max()
                .unwrap_or(0);
            if tmax == 0 {
                continue;
            }
            for el in &b.elements {
                if !want.contains(&el.name.as_str()) {
                    continue;
                }
                if ui_layout::sprite_layer_key(&b, &by, el).is_some() {
                    continue;
                }
                let op = opaque_span(el, 255, tmax);
                if op.is_empty() {
                    continue;
                }
                // when is any OTHER element visible?
                let mut cmin = f64::MAX;
                let mut cmax = f64::MIN;
                for o in &b.elements {
                    if o.index == el.index {
                        continue;
                    }
                    for (s, t) in opaque_span(o, 1, tmax) {
                        cmin = cmin.min(s);
                        cmax = cmax.max(t)
                    }
                }
                if cmin > cmax {
                    continue;
                }
                // overlap of the primitive's opaque span with the content span
                let ov: f64 = op
                    .iter()
                    .map(|&(s, t)| (t.min(cmax) - s.max(cmin)).max(0.0))
                    .sum();
                let opd: String = op
                    .iter()
                    .map(|&(s, t)| format!("{s:.0}-{t:.0}"))
                    .collect::<Vec<_>>()
                    .join(",");
                let flag = if ov > 2.0 {
                    "  🔴 CANNOT BE ON TOP"
                } else {
                    ""
                };
                println!(
                    "{:>22} {:>5}  {:>16}  {:>18}  {ov:6.1}{flag}",
                    el.name,
                    format!(
                        "{}:{}",
                        p.file_name()
                            .unwrap()
                            .to_string_lossy()
                            .trim_end_matches(".pak")
                            .trim_start_matches("GP_"),
                        ei
                    ),
                    opd,
                    format!("{cmin:.0}-{cmax:.0}")
                );
            }
        }
    }
}