//! Retained CPU-layout diagnostics on one reproducible random tree.
//!
//! Counters and phase timers:
//!
//!     cargo test --release --features layout-diagnostics \
//!       --test layout_diagnostics -- --ignored --nocapture
//!
//! Uninstrumented hardware totals for one phase:
//!
//!     IRIS_PHASE=resize IRIS_FRAMES=1000 perf stat \
//!       -e cycles:u,instructions:u cargo test --release \
//!       --test layout_diagnostics -- --ignored --nocapture
//!
//! `IRIS_PHASE` is `cold`, `repaint`, `many`, `size`, `scroll`, `resize`, or
//! `all`. `IRIS_SEED`, `IRIS_DEPTH`, and `IRIS_FRAMES` select the load, and
//! `IRIS_DIRTY` how many widgets `many` marks at once.

use iris::harness::Harness;
use iris::prelude::*;
use iris::random::{Edits, Tree, grow};
use std::time::Instant;

const OUTPUT: (f32, f32) = (1920.0, 1200.0);

#[cfg(feature = "layout-diagnostics")]
#[test]
fn a_selected_widget_retains_its_layout_events() {
    use iris::core::layout_diagnostics::{self as diagnostics, TraceEvent};

    diagnostics::clear_traced_widgets();
    let _ = diagnostics::take();
    let mut harness = Harness::new((400, 200));
    let leaf = rect(Color::RED).add(&mut harness.rsc);
    let other = rect(Color::BLUE).add(&mut harness.rsc);
    let root = (leaf, other).span(Dir::RIGHT).add(&mut harness.rsc);
    harness.set_root(root);
    diagnostics::trace_widget(leaf.id());
    let _ = diagnostics::take();

    let _ = harness.rsc.widgets_mut().get_dyn_mut(root.id());
    let _ = harness.rsc.widgets_mut().get_dyn_mut(leaf.id());
    harness.frame();

    let report = diagnostics::take();
    assert!(
        report
            .traces()
            .iter()
            .any(|event| matches!(event, TraceEvent::Placed { id, .. } if *id == leaf.id()))
    );
    assert!(
        report
            .traces()
            .iter()
            .any(|event| matches!(event, TraceEvent::DrawRequest { id, .. } if *id == leaf.id()))
    );
    assert!(
        report
            .traces()
            .iter()
            .any(|event| matches!(event, TraceEvent::SizeRead { id, .. } if *id == leaf.id()))
    );
    assert!(
        report
            .traces()
            .iter()
            .any(|event| matches!(event, TraceEvent::SizeReported { id, .. } if *id == leaf.id()))
    );
    diagnostics::clear_traced_widgets();
}

fn env<T: std::str::FromStr>(name: &str, fallback: T) -> T {
    std::env::var(name)
        .ok()
        .and_then(|value| value.parse().ok())
        .unwrap_or(fallback)
}

#[cfg(feature = "layout-diagnostics")]
fn trace_selected(tree: &Tree) {
    let Ok(value) = std::env::var("IRIS_TRACE_INDEX") else {
        return;
    };
    let index = value
        .parse::<usize>()
        .expect("IRIS_TRACE_INDEX must be a tree.ids index");
    let id = tree.ids[index];
    iris::core::layout_diagnostics::trace_widget(id);
    println!("tracing tree.ids[{index}] = {id:?}");
}

#[cfg(not(feature = "layout-diagnostics"))]
fn trace_selected(_: &Tree) {}

fn warm(seed: u64, depth: usize) -> (Harness, Tree) {
    let mut harness = Harness::new(OUTPUT);
    let (root, tree) = grow(&mut harness.rsc, seed, depth, &Edits::default());
    harness.state.root = Some(root);
    harness.frame();
    println!(
        "fixture: seed {seed}, depth {depth}, {} widgets, {} active",
        tree.ids.len(),
        harness.render.active_widgets()
    );
    #[cfg(feature = "layout-diagnostics")]
    let _ = iris::core::layout_diagnostics::take();
    (harness, tree)
}

fn report(label: &str, mut elapsed: Vec<f64>, _harness: &Harness) {
    elapsed.sort_by(|a, b| a.partial_cmp(b).unwrap());
    let frames = elapsed.len();
    // The worst frame is the stutter somebody sees, so it goes beside the
    // median; p99 says whether it is the load or a single interruption.
    println!(
        "{label}: {frames} frame(s), min {:.3} ms, median {:.3} ms, p99 {:.3} ms, \
         max {:.3} ms, total {:.1} ms",
        elapsed[0],
        elapsed[frames / 2],
        elapsed[frames * 99 / 100],
        elapsed[frames - 1],
        elapsed.iter().sum::<f64>(),
    );
    #[cfg(feature = "layout-diagnostics")]
    {
        let diagnostics = iris::core::layout_diagnostics::take();
        print!("{}", diagnostics.per_frame(frames));
        for callsite in diagnostics.hot_text().iter().take(3) {
            let mut ancestry = Vec::new();
            let mut id = Some(callsite.id);
            while let Some(widget) = id {
                ancestry.push(_harness.rsc.widgets().label(widget).as_str());
                id = _harness
                    .render
                    .active
                    .get(&widget)
                    .and_then(|active| active.parent);
            }
            println!("    text ancestry: {}", ancestry.join(" < "));
        }
    }
}

fn run(
    label: &str,
    frames: usize,
    harness: &mut Harness,
    mut change: impl FnMut(&mut Harness, usize),
) {
    let mut elapsed = Vec::with_capacity(frames);
    for frame in 0..frames {
        change(harness, frame);
        let start = Instant::now();
        harness.frame();
        elapsed.push(start.elapsed().as_secs_f64() * 1_000.0);
    }
    report(label, elapsed, harness);
}

#[test]
#[ignore = "measurement, not a check"]
fn layout_cost() {
    let seed = env("IRIS_SEED", 1_u64);
    let depth = env("IRIS_DEPTH", 7_usize);
    let frames = env("IRIS_FRAMES", 100_usize);
    assert!(frames > 0, "IRIS_FRAMES must be greater than zero");
    let phase = env("IRIS_PHASE", String::from("all"));
    assert!(
        ["all", "cold", "repaint", "many", "size", "scroll", "resize"].contains(&phase.as_str()),
        "unknown IRIS_PHASE {phase:?}"
    );
    let selected = |name| phase == "all" || phase == name;

    if selected("cold") {
        let mut harness = Harness::new(OUTPUT);
        let (root, tree) = grow(&mut harness.rsc, seed, depth, &Edits::default());
        harness.state.root = Some(root);
        println!(
            "fixture: seed {seed}, depth {depth}, {} widgets",
            tree.ids.len()
        );
        trace_selected(&tree);
        #[cfg(feature = "layout-diagnostics")]
        let _ = iris::core::layout_diagnostics::take();
        run("cold", 1, &mut harness, |_, _| {});
        drop(tree);
    }

    if selected("repaint") {
        let (mut harness, tree) = warm(seed, depth);
        trace_selected(&tree);
        let leaf = tree.ids[0];
        run("repaint", frames, &mut harness, move |harness, _| {
            let _ = harness.rsc.widgets_mut().get_dyn_mut(leaf);
        });
    }

    if selected("many") {
        let (mut harness, tree) = warm(seed, depth);
        trace_selected(&tree);
        // Spread through the tree rather than taken from one subtree, so the
        // dependency paths the frame settles overlap.
        let wanted = env("IRIS_DIRTY", 32_usize).max(1);
        let step = (tree.ids.len() / wanted).max(1);
        let dirty: Vec<_> = tree.ids.iter().copied().step_by(step).collect();
        println!("marking {} of {} widgets", dirty.len(), tree.ids.len());
        run("many", frames, &mut harness, move |harness, _| {
            for &id in &dirty {
                harness.rsc.widgets_mut().get_dyn_mut(id);
            }
        });
    }

    if selected("size") {
        let (mut harness, tree) = warm(seed, depth);
        trace_selected(&tree);
        let sized = tree.sized[0];
        run("size", frames, &mut harness, move |harness, frame| {
            harness.rsc[sized].x = Some(Len::px(100.0 + (frame % 2) as f32 * 40.0));
        });
    }

    if selected("scroll") {
        let (mut harness, tree) = warm(seed, depth);
        trace_selected(&tree);
        let scroll = tree.scrolls[0];
        run("scroll", frames, &mut harness, move |harness, frame| {
            harness.rsc[scroll].scroll(if frame % 2 == 0 { 12.0 } else { -12.0 });
        });
    }

    if selected("resize") {
        let (mut harness, tree) = warm(seed, depth);
        trace_selected(&tree);
        run("resize", frames, &mut harness, |harness, frame| {
            harness.resize((OUTPUT.0 - ((frame + 1) % 2) as f32 * 8.0, OUTPUT.1));
        });
        drop(tree);
    }
}