//! `.prm` elements are untextured quads, and the declaration table says so.
//!
//! Every composite the port draws is missing them: they carry no sprite, so
//! `compose` skips them. What they are was settled statically on 2026-08-19 —
//! see `docs/re/structures/ui-prm-primitives.md`. This pins the three facts the
//! decoding rests on, and is disc-gated like the rest of the corpus.

use std::path::{Path, PathBuf};

use sylpheed_formats::{pak::PakArchive, ratc, ui_layout};

mod common;
use common::disc_root;

fn for_each_build(root: &Path, mut f: impl FnMut(&str, &[u8])) {
    let mut paks: Vec<PathBuf> = std::fs::read_dir(root.join("dat"))
        .expect("dat/")
        .flatten()
        .map(|e| e.path())
        .filter(|p| p.extension().and_then(|s| s.to_str()) == Some("pak"))
        .collect();
    paks.sort();
    for p in &paks {
        let name = p.file_name().unwrap().to_string_lossy().to_string();
        let Ok(arc) = PakArchive::open(p) else {
            continue;
        };
        for e in arc.entries() {
            let Ok(bytes) = arc.read(e) else { continue };
            if ratc::is_ratc(&bytes) {
                f(&name, &bytes);
            }
        }
    }
}

/// **Bit `0x10` of `kind` means "untextured primitive", and it is exact.**
///
/// This is the point of the whole item: the primitive-ness is a *decoded field*,
/// not a guess from the `.prm` file extension. Over every screen build on the
/// disc, `kind & 0x10` and a `.prm` name agree with **zero** exceptions in
/// either direction — so a port can classify without parsing names.
///
/// Also pinned here because it is the same sweep: no `.prm` element has a RATC
/// child of its own name. All 369 of them are payload-less, which is what
/// "untextured" means concretely — there is nothing in the bundle to draw.
#[test]
fn kind_bit_0x10_means_prm_exactly_and_prm_carries_no_payload() {
    let Some(root) = disc_root() else {
        eprintln!("SKIP: extracted disc not found (set SYLPHEED_DISC to enable)");
        return;
    };
    let (mut prm, mut prm_without_bit, mut bit_without_prm, mut with_child) = (0, 0, 0, 0);
    let (mut full_screen, mut sized) = (0, 0);
    for_each_build(&root, |pak, bytes| {
        let Some(build) = ui_layout::parse_build(bytes) else {
            return;
        };
        if build.from_fallback {
            return;
        }
        let kids = ratc::parse(bytes).unwrap_or_default();
        for el in &build.elements {
            let is_prm = el.name.to_ascii_lowercase().ends_with(".prm");
            let has_bit = el.kind & 0x10 != 0;
            if is_prm && !has_bit {
                prm_without_bit += 1;
                eprintln!("{pak}: {} is .prm without bit 0x10", el.name);
            }
            if has_bit && !is_prm {
                bit_without_prm += 1;
                eprintln!("{pak}: {} has bit 0x10 but is not .prm", el.name);
            }
            if !is_prm {
                continue;
            }
            prm += 1;
            if kids.iter().any(|c| c.name == el.name) {
                with_child += 1;
                eprintln!("{pak}: {} has a payload child", el.name);
            }
            sized += 1;
            if (el.pivot_x * 2, el.pivot_y * 2) == (1280, 720) {
                full_screen += 1;
            }
        }
    });
    assert!(
        prm > 300,
        "only {prm} `.prm` elements — the sweep did not run"
    );
    assert_eq!(prm_without_bit, 0, "a `.prm` element without kind bit 0x10");
    assert_eq!(
        bit_without_prm, 0,
        "kind bit 0x10 on something that is not `.prm`"
    );
    assert_eq!(with_child, 0, "a `.prm` element with a payload child");
    // 361 of 369 are exactly the design space; the handful that are not are
    // small coloured quads (844x600, and two degenerate 0x720).
    assert!(
        full_screen * 10 > sized * 9,
        "only {full_screen}/{sized} `.prm` elements are full-screen"
    );
    eprintln!(
        "{prm} `.prm` elements: all kind&0x10, none with a payload, {full_screen} full-screen"
    );
}

/// **A `.prm` fade quad rests at its transparent plateau**, which is what makes
/// it drawable at all.
///
/// The title's `pteff00.prm` is a screen transition: opaque black at t=12,
/// transparent by t=64, held transparent to t=74, opaque black again on the way
/// out. What the title screen sits at is the transparent plateau — and this
/// element is painted **last** in the measured order, so getting it wrong means
/// a full-screen opaque black quad over everything.
///
/// It *was* wrong: the old longest-dwell resting rule picked the opaque
/// endpoint. This test asserted that defect deliberately until the plateau rule
/// replaced it (`docs/re/structures/ui-resting-pose.md`); now it guards the fix.
#[test]
fn the_title_fade_quad_rests_transparent() {
    let Some(root) = disc_root() else {
        eprintln!("SKIP: extracted disc not found (set SYLPHEED_DISC to enable)");
        return;
    };
    let arc = PakArchive::open(root.join("dat").join("GP_TITLE.pak")).expect("GP_TITLE.pak");
    let mut checked = 0usize;
    for e in arc.entries() {
        let Ok(bytes) = arc.read(e) else { continue };
        let Some(build) = ui_layout::parse_build(&bytes) else {
            continue;
        };
        for el in &build.elements {
            if el.name != "pteff00.prm" || el.keyframes.len() != 4 {
                continue;
            }
            checked += 1;
            let a: Vec<u32> = el.keyframes.iter().map(|k| k.fade >> 24).collect();
            assert_eq!(
                a,
                vec![0xff, 0x00, 0x00, 0xff],
                "the fade group is opaque → transparent → transparent → opaque"
            );
            assert_eq!(
                el.rest().map(|k| k.fade),
                Some(0x0000_0000),
                "the fade quad must rest at its transparent plateau — an opaque \
                 answer here paints a full-screen black quad over the title"
            );
        }
    }
    assert!(
        checked >= 3,
        "found {checked} title fade quads, expected several"
    );
}

/// **Drawing the primitives with the derived order swallows screens** — which
/// is why `ComposeOptions::include_primitives` is off by default.
///
/// A primitive has no `T8aD` header, so it has no layer key, and
/// `derived_paint_order` sorts the keyless to the very end. That is not a
/// harmless default: `GP_DIALOG`'s `pzeff00.prm` is a **single** keyframe of
/// opaque black at full screen, and painted last it wipes the build.
///
/// The ground truth contradicts *both* simple defaults. On the developer-logo
/// splash the game paints `palogo_eff0.prm` **first** — it is the black
/// backdrop. On the title it paints `pteff02.prm` at slot 4, beneath the
/// wordmark, and `pteff00.prm` **last**, as the fade-out. So the order is real,
/// per-element, and not derivable from anything decoded so far.
///
/// This test measures the damage rather than asserting the feature works, so the
/// number stays honest and moves when the ordering is solved.
#[test]
fn the_derived_order_puts_primitives_last_and_that_wipes_screens() {
    let Some(root) = disc_root() else {
        eprintln!("SKIP: extracted disc not found (set SYLPHEED_DISC to enable)");
        return;
    };
    let opts = |primitives| ui_layout::ComposeOptions {
        backdrop: [0, 0, 0, 255],
        include_primitives: primitives,
        ..Default::default()
    };
    let flatness = |c: &ui_layout::ComposedScreen| {
        let mut hist = std::collections::HashMap::<[u8; 3], usize>::new();
        for p in c.rgba.chunks_exact(4) {
            *hist.entry([p[0], p[1], p[2]]).or_default() += 1;
        }
        *hist.values().max().unwrap_or(&0) as f64 / (c.width * c.height) as f64
    };
    let (mut with_prm, mut wiped_on, mut wiped_off) = (0usize, 0usize, 0usize);
    for_each_build(&root, |_pak, bytes| {
        if !ui_layout::is_build(bytes) {
            return;
        }
        let Some(b) = ui_layout::parse_build(bytes) else {
            return;
        };
        if b.from_fallback
            || !b.elements.iter().any(|e| {
                e.kind & 0x10 != 0
                    && e.sprite.is_none()
                    && e.rest().map(|k| (k.fade >> 24) & 0xff).unwrap_or(0) != 0
            })
        {
            return;
        }
        with_prm += 1;
        if flatness(&ui_layout::compose(&b, bytes, opts(true), None)) > 0.99 {
            wiped_on += 1;
        }
        if flatness(&ui_layout::compose(&b, bytes, opts(false), None)) > 0.99 {
            wiped_off += 1;
        }
    });
    assert!(with_prm > 50, "only {with_prm} builds draw a primitive");
    assert_eq!(
        wiped_off, 0,
        "the DEFAULT composite wipes {wiped_off} builds — primitives are supposed \
         to be off unless asked for"
    );
    assert!(
        wiped_on > 0,
        "no build is wiped with primitives on — the ordering problem this flag \
         exists for may be solved, in which case turn it on by default"
    );
    eprintln!(
        "{with_prm} builds draw a visible primitive; with the derived order \
         {wiped_on} of them come out >99% one colour, {wiped_off} by default"
    );
}