locum 0.1.3

//! One-frame capture: everything a frame did on the GPU, with the state of every draw and the contents of every
//! resource it used, written to `captures/<name>/capture.db` with the contents in the blob store.
//!
//! Requested by creating the file `capture` in locum's folder; it is removed when seen. Everything is captured by
//! default; its lines can change that:
//! - `label NAME`: the capture's folder name (default `frame-<n>`);
//! - `skip targets`: no target readback at pass ends or clear-output checkpoints; `skip contents`: no resource contents;
//! - `max_mb N`: the most memory the copies of targets, clears and what draws and dispatches wrote through UAVs may use
//!   (default 4096);
//! - `skip memory`: no memory dump of the process (see [`super::dump`]);
//! - `frames N`: the next N frames, each a capture of its own (`<label>-1` to `<label>-N`, or `frame-<n>` each), with
//!   nothing between them: the frame after one capture's is the next one's (see [Series](#series)).
//!
//! A capture runs over two frames:
//! - **before** (from the present that sees the file): deferred contexts record their work, so command lists
//!   recorded now and executed in the captured frame are complete;
//! - **recording** (the next frame): every draw, dispatch and resource-changing call on every context, in the order
//!   the GPU runs them (a command list's work where it is executed);
//! - **finish** (the present ending that frame): the copies are read and the capture is handed to the writer thread.
//!
//! A resource's contents as the frame began are copied on the immediate context just before the first event on the
//! GPU's timeline that touches it (reads or writes it): before an immediate-context call, or before the
//! `ExecuteCommandList` whose list touches it first. Nothing has touched it since the frame began, so the copy is
//! exact whatever the frame does to it later, on whichever context, and however often a list runs. Immutable
//! resources whose upload is stored are not copied: the upload is their contents.
//!
//! # Series
//!
//! With `frames N`, the present ending a captured frame starts the next one's recording: deferred contexts go on
//! recording through it, and the command lists recorded so far (finished or not) are handed to the next capture with
//! the views, states, hidden counters and resources their events refer to and the constant-buffer staging their copies
//! write into, so a list recorded in one frame and executed in the next is complete in the next. Each capture is whole
//! on its own: its resources' contents as its frame began, every event of its frame. A resource's number is the same
//! in every capture of the process, so what one frame wrote can be followed into the next. The memory dump is taken at
//! the first frame only.
//!
//! The state of each draw is read from the real context with its getters. Constant buffers are copied by the GPU on
//! the draw's own context, so each draw's constants are the ones the GPU read. A pass ends where the targets in
//! effect change on the GPU's timeline; its targets are read back there (see [`targets`]).

pub mod contents;
mod counters;
pub mod coverage;
pub mod ids;
pub mod ops;
mod snapshot;
mod targets;
pub mod tiled;
mod write;

use core::ffi::c_void;
use std::collections::{BTreeMap, BTreeSet};
use std::sync::Mutex;
use std::sync::atomic::{AtomicBool, AtomicU32, AtomicU64, Ordering};

use locum_capture::cost::Cost;
use locum_capture::db;
use serde_json::Value;
use windows::Win32::Graphics::Direct3D11::*;

use crate::d3d11::registry::Dims;
use crate::log::{folder, log};

use ids::buffer_id;
pub use ids::input_layout_created;

/// True from the request to the end of the captured frame: the only check on the hot paths otherwise.
static ARMED: AtomicBool = AtomicBool::new(false);
static EPOCH: AtomicU64 = AtomicU64::new(0);

fn epoch() -> u64 {
    if armed() { EPOCH.load(Ordering::Relaxed) } else { 0 }
}

pub fn armed() -> bool {
    ARMED.load(Ordering::Relaxed)
}

#[derive(Clone, Copy, PartialEq, Eq, Debug)]
enum Phase {
    Idle,
    Before,
    Recording,
}

/// What a capture request asked for.
#[derive(Clone, Debug)]
struct Request {
    label: Option<String>,
    targets: bool,
    contents: bool,
    memory: bool,
    max_target_bytes: u64,
    /// How many consecutive frames to capture, each its own capture.
    frames: u32,
}

/// The most frames one request captures.
const MAX_FRAMES: u32 = 64;

impl Request {
    fn parse(text: &str) -> Request {
        let mut r = Request {
            label: None,
            targets: true,
            contents: true,
            memory: true,
            max_target_bytes: 4096 << 20,
            frames: 1,
        };
        for line in text.lines() {
            let mut words = line.split_whitespace();
            match (words.next(), words.next()) {
                (Some("label"), Some(name)) => {
                    let clean: String = name
                        .chars()
                        .filter(|c| c.is_ascii_alphanumeric() || "-_.".contains(*c))
                        .collect();
                    r.label = (!clean.is_empty()).then_some(clean);
                }
                (Some("skip"), Some("targets")) => r.targets = false,
                (Some("skip"), Some("contents")) => r.contents = false,
                (Some("skip"), Some("memory")) => r.memory = false,
                (Some("max_mb"), Some(n)) => {
                    if let Ok(n) = n.parse::<u64>() {
                        r.max_target_bytes = n << 20;
                    }
                }
                (Some("frames"), Some(n)) => match n.parse::<u32>() {
                    Ok(n @ 1..=MAX_FRAMES) => r.frames = n,
                    _ => log!("capture request: frames {n:?} is not 1 to {MAX_FRAMES}; one frame"),
                },
                // Older requests asked for targets; they are on by default now.
                (Some("targets"), None) => {}
                (Some(other), _) => log!("capture request: unknown option {other:?} ignored"),
                (None, _) => {}
            }
        }
        r
    }
}

/// The context a call is made on: the real context, locum's number for it, and whether it is deferred.
#[derive(Clone, Copy)]
pub struct Ctx<'a> {
    pub c: &'a ID3D11DeviceContext4,
    pub id: u32,
    pub deferred: bool,
}

/// A constant buffer bound at a draw and where its GPU copy went.
#[derive(Clone)]
pub(super) struct CbCopy {
    /// Its row in the draw's bindings.
    binding: usize,
    source: Option<ID3D11Buffer>,
    first: u32,
    count: u32,
    /// The bound window intersects no constants in the buffer.
    empty: bool,
    /// Staging chunk, offset, bytes.
    copy: Option<(u32, u32, u32)>,
}

/// A draw's or dispatch's state.
#[derive(Clone, Default)]
pub(super) struct Draw {
    shaders: [Option<String>; 6],
    bindings: Vec<db::Binding>,
    cb_copies: Vec<CbCopy>,
    viewports: Vec<db::Viewport>,
    scissors: Vec<db::Scissor>,
    topology: i32,
    layout: Option<u64>,
    rasterizer: Option<u64>,
    blend: Option<u64>,
    depth_stencil: Option<u64>,
    blend_factor: Option<[f32; 4]>,
    sample_mask: Option<u32>,
    stencil_ref: Option<u32>,
    predicate: Option<u64>,
    predicate_value: Option<bool>,
    /// The targets as they were when the pass this draw is the last of ended, and how many events (clears, copies,
    /// dispatches) after the draw on its context ran before that.
    after: Vec<targets::Target>,
    after_events: u32,
    /// The targets bound at the draw.
    bound: Vec<targets::Bound>,
    /// Whether the pass this draw ends has been dealt with.
    closed: bool,
    /// Whether one of its shaders writes what depends on the order the GPU runs its threads.
    order_dependent: bool,
    /// Live rules actually applied after this snapshot (kept with deferred draws until execution).
    overrides: Vec<String>,
}

/// One thing a context did, as recorded on it.
#[derive(Clone)]
pub(super) struct Event {
    kind: &'static str,
    call: &'static str,
    context: u32,
    deferred: bool,
    args: Value,
    /// Key of the bytes an update or map wrote.
    data: Option<String>,
    /// A tile seed copied at this event, read and hashed before serialization.
    data_readback: Option<contents::Readback>,
    stack: Vec<u64>,
    draw: Option<Box<Draw>>,
    reads: Vec<u64>,
    writes: Vec<u64>,
    /// Views whose hidden counters this event uses or resets.
    counters: Vec<u64>,
    /// The number of the command list execution it came in with (set when spliced).
    list: Option<u64>,
    /// Output checkpoints made immediately after a draw, dispatch or clear.
    results: Vec<(u64, Result<contents::Readback, String>)>,
    results_taken: bool,
}

/// A finished command list's events, whether it was finished before the captured frame, and how often the captured
/// frame executed it.
struct List {
    events: Vec<Event>,
    complete: bool,
    before: bool,
    executions: u32,
}

/// A resource the capture uses, held until it ends.
pub(super) struct Tracked {
    resource: ID3D11Resource,
    dims: Dims,
    /// Whether an event on the timeline has touched it (so its contents were copied, or are its upload).
    touched: bool,
}

struct State {
    phase: Phase,
    frame: u64,
    request: Request,
    /// Events recorded on a deferred context since its last FinishCommandList, by context id.
    pending: BTreeMap<u32, Vec<Event>>,
    /// Finished command lists, by address.
    lists: BTreeMap<usize, List>,
    timeline: Vec<Event>,
    lists_spliced: u32,
    lists_before: u32,
    lists_unrecorded: u32,
    /// Constant-buffer staging chunks and the bytes used in the last one.
    staging: Vec<ID3D11Buffer>,
    used: u32,
    copy_failures: u32,
    /// Bytes of target and output copies made so far, against the request's `max_mb`.
    target_bytes: u64,
    targets_skipped: u32,
    targets_skipped_bytes: u64,
    /// Captures requested so far: the current capture's number.
    captures: u64,
    views: Vec<db::View>,
    states: Vec<db::State>,
    resources: BTreeMap<u64, Tracked>,
    /// Copies of contents not read yet, and their bytes.
    in_flight: Vec<(u64, Result<contents::Readback, String>)>,
    in_flight_bytes: u64,
    /// Contents read so far (key and subresource keys), or why there are none.
    contents: BTreeMap<u64, contents::Read>,
    counter_views: BTreeMap<u64, ID3D11UnorderedAccessView>,
    /// Every view with a hidden counter this capture has described (`counter_views` loses each as it is copied).
    counter_seen: BTreeMap<u64, ID3D11UnorderedAccessView>,
    counter_copies: BTreeMap<u64, Result<ID3D11Buffer, String>>,
    gaps: BTreeMap<(String, String), u64>,
    tile_initialized: BTreeSet<u64>,
    tile_seeded: BTreeSet<(u64, u32)>,
    /// Packed seeds preserve canonical texels only for their recorded group and ordered pool mappings.
    tile_packed_seeded: BTreeSet<(u64, u64, u32, Vec<u32>)>,
    /// The resource and global packed-mapping generations last checked (`tiled::touch`).
    tile_seen: BTreeMap<u64, (u64, u64)>,
    /// Where in the timeline the tile seeds whose copies are still in flight are.
    tile_seeds: Vec<usize>,
    /// The back buffer the captured frame presented.
    presented: Option<u64>,
    /// The captured frame's place in its series, from 1 (`frames N` in the request).
    index: u32,
}

/// What one capture of a series hands the next: the deferred work recorded and not yet run, and everything its events
/// refer to that the capture keeps (see [Series](self#series)).
pub(super) struct Carried {
    pending: BTreeMap<u32, Vec<Event>>,
    lists: BTreeMap<usize, List>,
    staging: Vec<ID3D11Buffer>,
    used: u32,
    views: Vec<db::View>,
    states: Vec<db::State>,
    counters: BTreeMap<u64, ID3D11UnorderedAccessView>,
    resources: BTreeMap<u64, Tracked>,
}

static STATE: Mutex<State> = Mutex::new(State {
    phase: Phase::Idle,
    frame: 0,
    request: Request {
        label: None,
        targets: false,
        contents: false,
        memory: false,
        max_target_bytes: 0,
        frames: 1,
    },
    pending: BTreeMap::new(),
    lists: BTreeMap::new(),
    timeline: Vec::new(),
    lists_spliced: 0,
    lists_before: 0,
    lists_unrecorded: 0,
    staging: Vec::new(),
    used: 0,
    copy_failures: 0,
    target_bytes: 0,
    targets_skipped: 0,
    targets_skipped_bytes: 0,
    captures: 0,
    views: Vec::new(),
    states: Vec::new(),
    resources: BTreeMap::new(),
    in_flight: Vec::new(),
    in_flight_bytes: 0,
    contents: BTreeMap::new(),
    counter_views: BTreeMap::new(),
    counter_seen: BTreeMap::new(),
    counter_copies: BTreeMap::new(),
    gaps: BTreeMap::new(),
    tile_initialized: BTreeSet::new(),
    tile_seeded: BTreeSet::new(),
    tile_packed_seeded: BTreeSet::new(),
    tile_seen: BTreeMap::new(),
    tile_seeds: Vec::new(),
    presented: None,
    index: 0,
});

fn state() -> std::sync::MutexGuard<'static, State> {
    STATE.lock().unwrap_or_else(|e| e.into_inner())
}

impl State {
    /// Whether work on a context is recorded now: deferred contexts from the request on, the immediate context only
    /// in the captured frame.
    fn records(&self, deferred: bool) -> bool {
        match self.phase {
            Phase::Idle => false,
            Phase::Before => deferred,
            Phase::Recording => true,
        }
    }

    fn reset(&mut self) {
        self.pending.clear();
        self.lists.clear();
        self.timeline.clear();
        self.lists_spliced = 0;
        self.lists_before = 0;
        self.lists_unrecorded = 0;
        self.staging.clear();
        self.used = 0;
        self.copy_failures = 0;
        self.target_bytes = 0;
        self.targets_skipped = 0;
        self.targets_skipped_bytes = 0;
        self.views.clear();
        self.states.clear();
        self.resources.clear();
        self.in_flight.clear();
        self.in_flight_bytes = 0;
        self.contents.clear();
        self.counter_views.clear();
        self.counter_seen.clear();
        self.counter_copies.clear();
        self.gaps.clear();
        self.tile_initialized.clear();
        self.tile_seeded.clear();
        self.tile_packed_seeded.clear();
        self.tile_seen.clear();
        self.tile_seeds.clear();
        self.presented = None;
    }

    /// Whether the frame being recorded or finished has another of its series after it.
    fn continues(&self) -> bool {
        self.index < self.request.frames
    }

    /// The deferred work recorded so far and what it refers to, for the next capture of the series: every list is
    /// one recorded before that capture's frame, not yet executed in it.
    fn carry(&mut self) -> Carried {
        let pending = std::mem::take(&mut self.pending);
        let mut lists = std::mem::take(&mut self.lists);
        for l in lists.values_mut() {
            l.before = true;
            l.executions = 0;
        }
        let referred: BTreeSet<u64> = pending
            .values()
            .flatten()
            .chain(lists.values().flat_map(|l| &l.events))
            .flat_map(|e| e.reads.iter().chain(&e.writes).copied())
            .collect();
        let resources = referred
            .iter()
            .filter_map(|id| {
                let t = self.resources.get(id)?;
                Some((
                    *id,
                    Tracked {
                        resource: t.resource.clone(),
                        dims: t.dims.clone(),
                        touched: false,
                    },
                ))
            })
            .collect();
        Carried {
            pending,
            lists,
            staging: self.staging.clone(),
            used: self.used,
            views: self.views.clone(),
            states: self.states.clone(),
            counters: self.counter_seen.clone(),
            resources,
        }
    }

    /// Takes on what the previous capture of the series carried (after [`State::reset`]).
    fn take_on(&mut self, c: Carried) {
        self.pending = c.pending;
        self.lists = c.lists;
        self.staging = c.staging;
        self.used = c.used;
        self.views = c.views;
        self.states = c.states;
        self.counter_views = c.counters.clone();
        self.counter_seen = c.counters;
        self.resources = c.resources;
    }
}

/// Ids for contexts, handed out as they are wrapped.
pub fn next_context_id() -> u32 {
    static NEXT: AtomicU32 = AtomicU32::new(0);
    NEXT.fetch_add(1, Ordering::Relaxed)
}

/// Gives up a capture in progress, if any, releasing everything it holds (a swap chain resize needs its back buffers
/// free). The request is not taken again: a new one is needed.
pub fn abandon(why: &str) {
    if !armed() {
        return;
    }
    let mut s = state();
    if s.phase == Phase::Idle {
        return;
    }
    ARMED.store(false, Ordering::Relaxed);
    s.phase = Phase::Idle;
    s.reset();
    drop(s);
    ops::reset();
    log!("capture abandoned: {why}");
}

/// At each present, before the real one (and after [`end_frame`]). Ends a frame being recorded.
pub fn before_present(presented: impl FnOnce() -> Option<u64>) -> bool {
    // the back buffer is looked up only while a capture is armed, and before the state is locked
    let presented = if armed() { presented() } else { None };
    let mut s = state();
    s.frame += 1;
    if s.phase == Phase::Recording {
        s.presented = presented;
        if s.continues() {
            // Deferred contexts go on recording for the next frame of the series while this one is finished.
            s.phase = Phase::Before;
        } else {
            ARMED.store(false, Ordering::Relaxed);
            s.phase = Phase::Idle;
        }
        return true;
    }
    false
}

/// At each present, after the real one. `finished` is what [`before_present`] returned; `immediate` is the real
/// immediate context.
pub fn after_present(finished: bool, immediate: &ID3D11DeviceContext4) {
    if finished {
        write::finish(immediate);
        // The next frame of a series is recorded from here, under the same epoch: a list recorded across the two
        // frames is complete. Views and states are described again under the next capture's number.
        let mut s = state();
        if s.phase == Phase::Before {
            s.index += 1;
            s.captures += 1;
            log!("capture: frame {} of {}", s.index, s.request.frames);
            drop(s);
            start();
        }
        return;
    }
    let phase = state().phase;
    match phase {
        Phase::Idle => {
            let mut s = state();
            // Look for a request every 30 frames.
            if !s.frame.is_multiple_of(30) {
                return;
            }
            let Some(path) = folder().map(|d| d.join("capture")) else {
                return;
            };
            let Ok(text) = std::fs::read_to_string(&path) else {
                return;
            };
            if std::fs::remove_file(&path).is_err() {
                return;
            }
            s.reset();
            s.request = Request::parse(&text);
            s.index = 1;
            s.phase = Phase::Before;
            s.captures += 1;
            EPOCH.store(s.captures, Ordering::Relaxed);
            ARMED.store(true, Ordering::Relaxed);
            log!(
                "capture requested at frame {}: {:?}; recording frame {}",
                s.frame,
                s.request,
                s.frame + 2
            );
            log!("  {}", crate::cost::line());
        }
        Phase::Before => start(),
        Phase::Recording => {}
    }
}

/// The present before the captured frame: the frame is recorded from here.
fn start() {
    state().phase = Phase::Recording;
    log!("capture: recording");
    log!("  getting ready, {}", crate::cost::line());
}

/// Copies the contents of each resource `event` touches that the timeline has not touched before, on the immediate
/// context `immediate`, before the caller makes the real call (see the module's documentation). A copy that would
/// take the bytes in flight past [`contents::IN_FLIGHT`] has those read first.
fn first_touch(immediate: &ID3D11DeviceContext4, event: &Event) {
    let started = std::time::Instant::now();
    let todo: Vec<(u64, ID3D11Resource, u64)> = {
        let mut s = state();
        if s.phase != Phase::Recording || !s.request.contents {
            return;
        }
        let mut todo = Vec::new();
        for id in event.reads.iter().chain(&event.writes) {
            if let Some(t) = s.resources.get_mut(id)
                && (!t.touched
                    || t.dims.misc
                        & (D3D11_RESOURCE_MISC_TILED.0 as u32 | D3D11_RESOURCE_MISC_TILE_POOL.0 as u32)
                        != 0)
            {
                t.touched = true;
                let bytes = t.dims.subs().map_or(0, |s| locum_capture::layout::total(&s));
                todo.push((*id, t.resource.clone(), bytes));
            }
        }
        todo
    };
    counters::touch(immediate, &event.counters);
    if todo.is_empty() {
        return;
    }
    let mut bytes = 0;
    for (id, resource, size) in todo {
        if tiled::special(&resource) {
            tiled::touch(immediate, &resource);
            continue;
        }
        if write::upload_of(id).is_some() {
            continue;
        }
        let full = state().in_flight_bytes + size > contents::IN_FLIGHT;
        if full {
            read_in_flight(immediate);
        }
        let copy = unsafe { contents::issue(immediate, &resource) };
        bytes += size;
        let mut s = state();
        s.in_flight.push((id, copy));
        s.in_flight_bytes += size;
    }
    COPIED.add(started, bytes);
}

/// Reads the copies in flight (waiting for the GPU to make them), outside the capture's lock.
fn read_in_flight(immediate: &ID3D11DeviceContext4) {
    let copies = {
        let mut s = state();
        s.in_flight_bytes = 0;
        std::mem::take(&mut s.in_flight)
    };
    let read = unsafe { contents::read_all(immediate, copies) };
    state().contents.extend(read);
    let seeds: Vec<_> = {
        let mut s = state();
        let at = std::mem::take(&mut s.tile_seeds);
        at.into_iter()
            .filter_map(|seq| Some((seq, s.timeline.get_mut(seq)?.data_readback.take()?)))
            .collect()
    };
    for (seq, rb) in seeds {
        match unsafe { contents::read(immediate, &rb) } {
            Ok((key, _)) => {
                if let Some(e) = state().timeline.get_mut(seq) {
                    e.data = Some(key);
                }
            }
            Err(error) => {
                *state().gaps.entry(("tiled".into(), error)).or_default() += 1;
            }
        }
    }
}

/// Contents copied before the timeline first touched them, with the time it took (and any reads keeping the copies
/// in flight under their limit).
pub static COPIED: Cost = Cost::new();

/// Records an event on a context, while armed. An event on the immediate context in the captured frame first has
/// the contents of what it touches copied (see [`first_touch`]); a deferred context's wait for its command list.
pub(super) fn record(c: &ID3D11DeviceContext4, mut event: Event) {
    let started = std::time::Instant::now();
    if !state().records(event.deferred) {
        return;
    }
    if event.deferred {
        state().pending.entry(event.context).or_default().push(event);
    } else {
        tiled::dependencies(&mut event);
        first_touch(c, &event);
        state().timeline.push(event);
    }
    RECORDED.add(started, 0);
}

/// Events recorded (the copies before them are [`COPIED`]).
pub static RECORDED: Cost = Cost::new();

/// What [`record`] does before recording an event, for a call recorded later: a map's resource is copied before the
/// map, and the map is recorded at the unmap, when its data is known.
pub(super) fn touch_only(c: &ID3D11DeviceContext4, event: &Event) {
    if !event.deferred {
        first_touch(c, event);
    }
}

fn new_event(kind: &'static str, call: &'static str, context: u32, deferred: bool, args: Value) -> Event {
    let mut counters: Vec<_> = args["view"].as_u64().into_iter().collect();
    counters.extend(
        args["set"]
            .as_array()
            .into_iter()
            .flatten()
            .filter_map(|s| s["view"].as_u64()),
    );
    Event {
        kind,
        call,
        context,
        deferred,
        args,
        data: None,
        data_readback: None,
        stack: Vec::new(),
        draw: None,
        reads: Vec::new(),
        writes: Vec::new(),
        counters,
        list: None,
        results: Vec::new(),
        results_taken: false,
    }
}

/// A draw or dispatch on a context, while armed. `context` is the real context it runs on.
pub fn on_draw(x: Ctx, call: &'static str, args: &[i64]) {
    draw_event(x, call, args.iter().map(|&a| Value::from(a)).collect(), &[]);
}

/// An indirect draw or dispatch, while armed: its arguments are the buffer's number and offset, and it reads the
/// buffer.
///
/// # Safety
/// `buffer` must be null or a live `ID3D11Buffer`.
pub unsafe fn on_indirect(x: Ctx, call: &'static str, buffer: *mut c_void, offset: u32) {
    let id = unsafe { buffer_id(buffer) };
    let reads: Vec<u64> = (id != 0).then_some(id).into_iter().collect();
    draw_event(x, call, vec![Value::from(id), Value::from(offset)], &reads);
}

fn draw_event(
    Ctx {
        c: context,
        id,
        deferred,
    }: Ctx,
    call: &'static str,
    args: Vec<Value>,
    extra_reads: &[u64],
) {
    let (records, targets) = {
        let s = state();
        (s.records(deferred), s.request.targets)
    };
    let compute = call.starts_with("Dispatch");
    let mut draw = Box::<Draw>::default();
    let touches = unsafe { snapshot::snapshot(context, compute, &mut draw) };
    if records {
        if targets && !compute {
            draw.bound = unsafe { targets::bound(context) };
        }
        // Constant-buffer copies, recorded on this context right now.
        for cb in &mut draw.cb_copies {
            cb.copy = unsafe { snapshot::copy_cb(context, cb) };
        }
    }
    let kind = if compute { "dispatch" } else { "draw" };
    let mut event = new_event(kind, call, id, deferred, Value::Array(args));
    event.reads = touches.reads;
    event.reads.extend_from_slice(extra_reads);
    event.writes = touches.writes;
    event.counters.extend(
        draw.bindings
            .iter()
            .filter(|b| b.kind == "uav")
            .filter_map(|b| b.view),
    );
    event.draw = Some(draw);
    record(context, event);
}

/// After a draw or dispatch ran on a context, while armed: what it wrote through UAVs is copied now, on its context,
/// within the capture's memory limit. Replay checks its own output against the game's and goes on from the game's, so
/// the first event whose output differs is the one named, and what follows is compared from the game's state. For a
/// shader whose writes depend on the order the GPU runs its threads, the same records in another order are that
/// order, not a difference.
pub fn after_draw(ctx: Ctx) {
    after_output(ctx, false);
}

/// A clear can write a view which was never bound, and need not be followed by a draw.
pub fn after_clear(ctx: Ctx) {
    after_output(ctx, true);
}

/// The snapshot preceded this live rule. Keep the reason with the draw so an unexecuted list does not create a gap.
pub fn rule_applied(Ctx { id, deferred, .. }: Ctx, rule: &str) {
    let mut s = state();
    if !s.records(deferred) {
        return;
    }
    let event = if deferred {
        s.pending.get_mut(&id).and_then(|p| p.last_mut())
    } else {
        s.timeline.last_mut()
    };
    if let Some(draw) = event.and_then(|e| e.draw.as_deref_mut()) {
        draw.overrides.push(rule.to_owned());
    }
}

fn after_output(
    Ctx {
        c: context,
        id,
        deferred,
    }: Ctx,
    clear: bool,
) {
    let outputs: Vec<(u64, ID3D11Resource)> = {
        let mut s = state();
        if !s.records(deferred)
            || !(if clear {
                s.request.targets
            } else {
                s.request.contents
            })
        {
            return;
        }
        let last = if deferred {
            s.pending.get_mut(&id).and_then(|p| p.last_mut())
        } else {
            s.timeline.last_mut()
        };
        let Some(e) = last else {
            return;
        };
        if e.results_taken || (clear && e.kind != "clear") || (!clear && e.draw.is_none()) {
            return;
        }
        e.results_taken = true;
        let mut ids: Vec<u64> = if clear {
            e.writes.clone()
        } else {
            e.draw
                .as_ref()
                .expect("draw")
                .bindings
                .iter()
                .filter(|b| b.kind == "uav")
                .filter_map(|b| b.resource)
                .collect()
        };
        ids.sort_unstable();
        ids.dedup();
        ids.into_iter()
            .filter_map(|i| s.resources.get(&i).map(|t| (i, t.resource.clone())))
            .collect()
    };
    let results: Vec<(u64, Result<contents::Readback, String>)> = outputs
        .into_iter()
        .map(|(i, r)| (i, unsafe { output_copy(context, &r) }))
        .collect();
    let mut s = state();
    let last = if deferred {
        s.pending.get_mut(&id).and_then(|p| p.last_mut())
    } else {
        s.timeline.last_mut()
    };
    if let Some(e) = last {
        e.results = results;
    }
}

/// An event's output, unless its copy would take the capture past its memory limit.
///
/// # Safety
/// `resource` must be a live resource of `context`'s device.
unsafe fn output_copy(
    context: &ID3D11DeviceContext4,
    resource: &ID3D11Resource,
) -> Result<contents::Readback, String> {
    let bytes = locum_d3d11::readback::bytes(resource)?;
    {
        let mut s = state();
        if s.target_bytes + bytes > s.request.max_target_bytes {
            return Err(OVER_LIMIT.into());
        }
        s.target_bytes += bytes;
    }
    unsafe { contents::issue(context, resource) }
}

/// Why an output was not copied: the capture's target and output copies reached `max_mb`.
pub(super) const OVER_LIMIT: &str = "over the capture's memory limit (max_mb)";

/// `OMSetRenderTargets` (or `ClearState`, with no targets) on a context, while armed: if it binds other targets than
/// the context's last draw used, that draw ended a pass and its targets are copied now, on this context.
///
/// # Safety
/// `rtvs` must hold null or live render target views, `dsv` null or a live depth stencil view.
pub unsafe fn targets_changing(
    Ctx {
        c: context,
        id,
        deferred,
    }: Ctx,
    rtvs: &[*mut c_void],
    dsv: *mut c_void,
) {
    if !state().request.targets {
        return;
    }
    let next = unsafe { targets::from_raw(rtvs, dsv) };
    if !deferred {
        close_timeline_pass(context, Some(&next));
        return;
    }
    let (index, bound) = {
        let s = state();
        if !s.records(true) {
            return;
        }
        let Some(pending) = s.pending.get(&id) else {
            return;
        };
        let Some(index) = pending.iter().rposition(|e| e.kind == "draw") else {
            return;
        };
        match pending[index].draw.as_deref() {
            Some(last) if !last.closed && !last.bound.is_empty() && !targets::same(&last.bound, &next) => {
                (index, last.bound.clone())
            }
            _ => return,
        }
    };
    let copied = unsafe { targets::copy(context, &bound) };
    let mut s = state();
    let Some(pending) = s.pending.get_mut(&id) else {
        return;
    };
    let after_events = (pending.len() - 1 - index) as u32;
    if let Some(last) = pending.get_mut(index).and_then(|e| e.draw.as_deref_mut()) {
        last.after = copied;
        last.after_events = after_events;
        last.closed = true;
    }
}

/// The timeline's last draw, if it is the last event that is a draw.
fn last_timeline_draw(s: &mut State) -> Option<(usize, &mut Draw)> {
    let index = s.timeline.iter().rposition(|e| e.kind == "draw")?;
    let draw = s.timeline[index].draw.as_deref_mut()?;
    Some((index, draw))
}

/// Copies the targets of the timeline's last draw, on the immediate context `immediate`, unless that pass is closed
/// already or `next` (the targets about to be used) are the same ones.
fn close_timeline_pass(immediate: &ID3D11DeviceContext4, next: Option<&[targets::Bound]>) {
    let (index, bound) = {
        let mut s = state();
        if !s.request.targets || s.phase != Phase::Recording {
            return;
        }
        let Some((index, last)) = last_timeline_draw(&mut s) else {
            return;
        };
        if last.closed || last.bound.is_empty() || next.is_some_and(|n| targets::same(&last.bound, n)) {
            return;
        }
        (index, last.bound.clone())
    };
    let copied = unsafe { targets::copy(immediate, &bound) };
    let mut s = state();
    let after_events = (s.timeline.len() - 1 - index) as u32;
    if let Some(d) = s.timeline[index].draw.as_deref_mut() {
        d.after = copied;
        d.after_events = after_events;
        d.closed = true;
    }
}

/// At each present, before [`before_present`]: the frame's last pass ends.
pub fn end_frame(immediate: &ID3D11DeviceContext4) {
    if armed() {
        close_timeline_pass(immediate, None);
    }
}

/// A deferred context's FinishCommandList: its pending events (possibly none) belong to the list.
pub fn on_finish_list(id: u32, list: *mut c_void, complete: bool) {
    let mut s = state();
    let events = s.pending.remove(&id).unwrap_or_default();
    let before = s.phase == Phase::Before;
    if !list.is_null() {
        s.lists.insert(
            list as usize,
            List {
                events,
                complete,
                before,
                executions: 0,
            },
        );
    }
}

/// ExecuteCommandList on `context`. On the immediate context the list's events join the timeline (after the pass
/// before them is closed if the list starts with other targets); on a deferred context (a list run from inside
/// another) they join that context's pending events. A list can be executed more than once, so its recording is kept
/// until the capture ends.
pub fn on_execute_list(
    Ctx {
        c: context,
        id,
        deferred,
    }: Ctx,
    list: *mut c_void,
) {
    let first = {
        let mut s = state();
        if !s.records(deferred) {
            return;
        }
        match s.lists.get(&(list as usize)) {
            Some(l) => l
                .events
                .iter()
                .find_map(|e| e.draw.as_deref().filter(|_| e.kind == "draw"))
                .map(|d| d.bound.clone()),
            None => {
                if !deferred {
                    s.lists_unrecorded += 1;
                }
                return;
            }
        }
    };
    if !deferred {
        if let Some(first) = first {
            close_timeline_pass(context, Some(&first));
        }
        // What the list touches first is copied before it runs.
        let touches = {
            let s = state();
            let mut e = new_event("execute", "ExecuteCommandList", id, false, Value::Null);
            if let Some(l) = s.lists.get(&(list as usize)) {
                for le in &l.events {
                    e.reads.extend_from_slice(&le.reads);
                    e.writes.extend_from_slice(&le.writes);
                    e.counters.extend_from_slice(&le.counters);
                }
            }
            e
        };
        first_touch(context, &touches);
    }
    let mut s = state();
    let number = u64::from(s.lists_spliced);
    let Some(l) = s.lists.get_mut(&(list as usize)) else {
        return;
    };
    l.executions += 1;
    let (mut events, before, complete) = (l.events.clone(), l.before, l.complete);
    if !deferred && !complete {
        *s.gaps.entry(("partial_list".into(), format!("command list {number}: commands before capture arming or from an earlier capture were not recorded"))).or_default() += 1;
    }
    if deferred {
        s.pending.entry(id).or_default().extend(events);
    } else {
        for e in &mut events {
            e.list = Some(number);
        }
        s.lists_spliced += 1;
        s.lists_before += u32::from(before);
        drop(s);
        for e in &mut events {
            tiled::dependencies(e);
        }
        state().timeline.extend(events);
    }
}

/// The resources the timeline touches, in the order it first touches them, with whether it writes them.
pub(super) fn touched(timeline: &[Event]) -> (BTreeSet<u64>, BTreeSet<u64>) {
    let mut used = BTreeSet::new();
    let mut written = BTreeSet::new();
    for e in timeline {
        used.extend(e.reads.iter().copied());
        used.extend(e.writes.iter().copied());
        written.extend(e.writes.iter().copied());
    }
    (used, written)
}

/// A retained list could not be reconstructed; the application executes its original list.
pub fn recorder_gap(reason: String) {
    *state()
        .gaps
        .entry(("deferred_recorder".into(), reason))
        .or_default() += 1;
}
pub fn discard_pending(context: u32) {
    state().pending.remove(&context);
}

pub fn list_recorded_before(list: *mut c_void, before: bool) {
    if let Some(list) = state().lists.get_mut(&(list as usize)) {
        list.before = before;
    }
}