unity_formats/

scene.rs

//! A scene's hierarchy: GameObjects, their Transforms (local TRS composed to world matrices in Unity's frame), and
//! its mesh renderers (skinned ones with their bones), LODGroups, colliders, lights and terrains, each whatever its
//! state.
//!
//! State is data: each object carries its [`OffFlag`]s, the GameObjects on its Transform chain stored inactive and the
//! component itself stored disabled; Unity draws or uses it when it has none. A LODGroup lists its levels' renderers
//! ([`LodGroup`]); which level draws is Unity's choice by screen size. A static-batched renderer draws a slice of a
//! combined mesh whose vertices are already in world space (its matrix is the identity). A RectTransform's local x
//! and y come from its anchors (the stored position can be stale): the parent rect's minimum plus its size times the
//! anchors interpolated at the pivot, plus the anchored position.

use std::collections::BTreeMap;

use serde::Serialize;

use crate::bump;
use crate::player::{ObjRef, Player};
use crate::value::{Array, Value};
use crate::{Result, invalid};

/// A MonoBehaviour as stored: its script (namespace and class) and the script's serialized fields, kept as bytes
/// (a stripped build has no type tree for them).
#[derive(Clone, Debug, PartialEq, Serialize)]
pub struct UnityBehaviour {
    /// The MonoBehaviour object.
    pub behaviour: ObjRef,
    /// The script's class, `namespace.class`; empty when the script cannot be resolved.
    pub script: String,
    /// `m_Enabled`.
    pub enabled: bool,
    /// The script's serialized fields, as bytes.
    #[serde(skip)]
    pub data: Vec<u8>,
}

/// A scene's ambient lighting as RenderSettings stores it: `mode` (`m_AmbientMode`: 0 skybox, 1 trilight, a gradient
/// of the sky, equator and ground colours, 3 flat, the sky colour alone, 4 custom), the three colours as stored,
/// `intensity` (`m_AmbientIntensity`) and the ambient probe as stored (`m_AmbientProbe`, Unity's SphericalHarmonicsL2:
/// nine coefficients per channel, red 0..8, green 9..17, blue 18..26; `None` when the RenderSettings store none). The
/// probe is what the editor last generated: all zeros when it never did, and not necessarily from the colours stored
/// beside it.
#[derive(Clone, Debug, PartialEq, Serialize)]
pub struct UnityAmbient {
    /// `m_AmbientMode`.
    pub mode: i64,
    /// `m_AmbientSkyColor`, RGBA.
    pub sky: [f32; 4],
    /// `m_AmbientEquatorColor`, RGBA.
    pub equator: [f32; 4],
    /// `m_AmbientGroundColor`, RGBA.
    pub ground: [f32; 4],
    /// `m_AmbientIntensity`.
    pub intensity: f32,
    /// `m_AmbientProbe`: 27 coefficients, red then green then blue; `None` when none is stored.
    pub probe: Option<[f32; 27]>,
}

/// The scene's fog as RenderSettings stores it: whether it is on (`m_Fog`), its `mode` (`m_FogMode`: 1 linear, 2
/// exponential, 3 exponential squared), its colour, `density` (exponential modes) and the linear mode's `start` and
/// `end`.
#[derive(Clone, Debug, PartialEq, Serialize)]
pub struct UnityFog {
    /// `m_Fog`.
    pub enabled: bool,
    /// `m_FogMode`.
    pub mode: i64,
    /// `m_FogColor`, RGBA.
    pub color: [f32; 4],
    /// `m_FogDensity`.
    pub density: f32,
    /// `m_LinearFogStart`.
    pub start: f32,
    /// `m_LinearFogEnd`.
    pub end: f32,
}

/// A 4x4 matrix, rows of columns (`m[row][col]`), column vectors: Unity's `Matrix4x4` layout, in f64.
pub type Matrix = [[f64; 4]; 4];

/// The identity matrix.
pub const IDENTITY: Matrix = [
    [1.0, 0.0, 0.0, 0.0],
    [0.0, 1.0, 0.0, 0.0],
    [0.0, 0.0, 1.0, 0.0],
    [0.0, 0.0, 0.0, 1.0],
];

/// The product `a * b`.
pub fn mul(a: &Matrix, b: &Matrix) -> Matrix {
    let mut m = [[0.0; 4]; 4];
    for (row, a_row) in m.iter_mut().zip(a) {
        for (j, x) in row.iter_mut().enumerate() {
            *x = a_row
                .iter()
                .zip(b)
                .map(|(&av, b_row)| av * b_row.get(j).copied().unwrap_or(0.0))
                .sum();
        }
    }
    m
}

/// Unity's `Matrix4x4.TRS`: translation, rotation (the quaternion as stored), scale.
pub fn trs(p: [f64; 3], q: [f64; 4], s: [f64; 3]) -> Matrix {
    let [x, y, z, w] = q;
    let r = [
        [
            1.0 - 2.0 * (y * y + z * z),
            2.0 * (x * y - z * w),
            2.0 * (x * z + y * w),
        ],
        [
            2.0 * (x * y + z * w),
            1.0 - 2.0 * (x * x + z * z),
            2.0 * (y * z - x * w),
        ],
        [
            2.0 * (x * z - y * w),
            2.0 * (y * z + x * w),
            1.0 - 2.0 * (x * x + y * y),
        ],
    ];
    let mut m = IDENTITY;
    // the rotation's three rows scaled by column; the fourth row stays (0, 0, 0, 1)
    for ((row, r_row), &position) in m.iter_mut().zip(&r).zip(&p) {
        for ((x, &rv), &sv) in row.iter_mut().zip(r_row).zip(&s) {
            *x = rv * sv;
        }
        if let Some(last) = row.get_mut(3) {
            *last = position;
        }
    }
    m
}

fn num(v: &Value, k: &str) -> Result<f64> {
    v.get(k)
        .and_then(Value::as_f32)
        .map(f64::from)
        .ok_or_else(|| invalid(format!("no float {k}")))
}

fn vec3(v: &Value, k: &str) -> Result<[f64; 3]> {
    let x = v.get(k).ok_or_else(|| invalid(format!("no {k}")))?;
    Ok([num(x, "x")?, num(x, "y")?, num(x, "z")?])
}

fn vec2(v: &Value, k: &str) -> Result<[f64; 2]> {
    let x = v.get(k).ok_or_else(|| invalid(format!("no {k}")))?;
    Ok([num(x, "x")?, num(x, "y")?])
}

/// A flag stored as a bool or as an integer (`m_IsActive` and `m_Enabled` are `UInt8` in some layouts).
fn flag_value(v: &Value) -> bool {
    match v {
        Value::Bool(b) => *b,
        x => x.as_i64().is_some_and(|i| i != 0),
    }
}

fn flag(v: &Value, k: &str) -> Result<bool> {
    match v.get(k) {
        Some(Value::Bool(b)) => Ok(*b),
        Some(x) => x
            .as_i64()
            .map(|i| i != 0)
            .ok_or_else(|| invalid(format!("{k} is not a flag"))),
        None => Err(invalid(format!("no {k}"))),
    }
}

fn path_id(v: &Value, k: &str) -> Result<i64> {
    v.at(&[k, "m_PathID"])
        .and_then(Value::as_i64)
        .ok_or_else(|| invalid(format!("no {k}.m_PathID")))
}

fn values<'a>(v: &'a Value, k: &str) -> Result<&'a [Value]> {
    match v.get(k) {
        Some(Value::Array(Array::Values(items))) => Ok(items),
        Some(Value::Array(a)) if a.is_empty() => Ok(&[]),
        _ => Err(invalid(format!("no list {k}"))),
    }
}

/// A GameObject as stored.
#[derive(Clone, Debug)]
pub struct GameObject {
    /// `m_Name`.
    pub name: String,
    /// `m_IsActive`.
    pub active: bool,
    /// `m_Layer`.
    pub layer: u32,
    /// Its components' path ids, in order.
    pub components: Vec<i64>,
}

/// A stored "off" between an object and being drawn or used: a GameObject on its Transform chain stored inactive
/// (`m_IsActive`), or the component itself stored disabled (`m_Enabled`); path ids in the scene's file.
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum OffFlag {
    /// The GameObject (path id) is stored inactive.
    Inactive(i64),
    /// The component (path id) is stored disabled.
    Disabled(i64),
}

#[derive(Clone, Debug)]
struct Node {
    game_object: i64,
    father: i64,
    local: Matrix,
    /// The stored local position, rotation (a quaternion `[x, y, z, w]`) and scale (a RectTransform's `local`
    /// position comes from its anchors instead).
    trs: ([f64; 3], [f64; 4], [f64; 3]),
}

/// A Transform as a joint of a skeleton: its GameObject's name, its father (a Transform's path id) and its local
/// position, rotation (`[x, y, z, w]`) and scale as stored, in Unity's frame.
#[derive(Clone, Debug, PartialEq)]
pub struct SceneJoint {
    /// The GameObject's name.
    pub name: String,
    /// The parent Transform's path id; `None` for a root.
    pub father: Option<i64>,
    /// Local position.
    pub translation: [f64; 3],
    /// Local rotation, a quaternion `[x, y, z, w]`.
    pub rotation: [f64; 4],
    /// Local scale.
    pub scale: [f64; 3],
}

/// An Animator component: the GameObject it animates (its Transform is the root of the paths its clips name), the
/// controller that lists its clips and its avatar; a null pointer is `None`.
#[derive(Clone, Debug, PartialEq)]
pub struct Animator {
    /// The Animator object.
    pub animator: ObjRef,
    /// The path id of the GameObject it animates.
    pub game_object: i64,
    /// That GameObject's path from the scene root, names joined by `/`.
    pub path: String,
    /// `m_Controller`.
    pub controller: Option<ObjRef>,
    /// `m_Avatar`.
    pub avatar: Option<ObjRef>,
    /// `m_Enabled` (true when the Animator does not store one).
    pub enabled: bool,
    /// `m_ApplyRootMotion`.
    pub apply_root_motion: bool,
}

/// A character: an Animator with skinned renderers on its GameObject or below it.
#[derive(Clone, Debug, PartialEq)]
pub struct Character {
    /// The Animator.
    pub animator: Animator,
    /// The SkinnedMeshRenderers on the Animator's GameObject and its descendants.
    pub skinned_renderers: usize,
}

/// A skinned renderer's bones: the Transforms (path ids in the renderer's file) its mesh's bone slots name, in slot
/// order, and its root bone; a null entry stays `None`.
#[derive(Clone, Debug, PartialEq)]
pub struct RendererSkin {
    /// `m_Bones`: the bone Transforms (path ids) in slot order.
    pub bones: Vec<Option<i64>>,
    /// `m_RootBone`.
    pub root_bone: Option<i64>,
    /// `m_BlendShapeWeights`: the weight of each of the mesh's blend shape channels (0 to 100 for a full shape).
    pub blend_weights: Vec<f32>,
}

/// A mesh renderer with a mesh, whatever its state.
#[derive(Clone, Debug, PartialEq)]
pub struct Renderer {
    /// The renderer object.
    pub renderer: ObjRef,
    /// Its GameObject, in the scene file.
    pub game_object: i64,
    /// The GameObject path, names from the root joined by `/`.
    pub path: String,
    /// Its GameObject's layer.
    pub layer: u32,
    /// The mesh (a SkinnedMeshRenderer's own, else its MeshFilter's).
    pub mesh: ObjRef,
    /// `m_Materials`, one entry per submesh slot; `None` for a null pointer.
    pub materials: Vec<Option<ObjRef>>,
    /// World matrix in Unity's frame (the identity for a static-batched renderer).
    pub world: Matrix,
    /// A static-batched renderer's slice of its combined mesh: first submesh, count.
    pub submeshes: Option<(u32, u32)>,
    /// `m_CastShadows`: 0 off, 1 on, 2 two-sided, 3 shadows only (1 when absent, Unity's default).
    pub cast_shadows: i64,
    /// `m_ReceiveShadows`, when stored.
    pub receive_shadows: Option<bool>,
    /// What keeps it from being drawn; drawn when empty.
    pub off: Vec<OffFlag>,
    /// A SkinnedMeshRenderer's bones; `None` for a MeshRenderer.
    pub skin: Option<RendererSkin>,
}

/// A LODGroup: its levels' renderers (path ids in the scene's file, a level's in stored order, null entries left out),
/// finest first; whether the component is enabled (a disabled LODGroup switches no level off) and its own off flags.
#[derive(Clone, Debug, PartialEq)]
pub struct LodGroup {
    /// The LODGroup object.
    pub group: ObjRef,
    /// Its GameObject's path from the scene root, names joined by `/`.
    pub path: String,
    /// `m_Enabled`.
    pub enabled: bool,
    /// What keeps the group from switching levels.
    pub off: Vec<OffFlag>,
    /// Per level, the path ids of its renderers.
    pub levels: Vec<Vec<i64>>,
}

/// The deepest chain of parents a scene may have. A Unity hierarchy is a few dozen deep.
const MAX_DEPTH: usize = 1024;

/// What the scene reading skipped, by reason.
pub type Skipped = std::collections::BTreeMap<&'static str, u64>;

/// A scene file's hierarchy: its GameObjects and Transforms, and from them the paths and world matrices of what the
/// scene holds.
#[derive(Debug)]
pub struct Scene {
    /// The scene's file (`level1`).
    pub file: String,
    /// The scene's GameObjects by path id.
    pub game_objects: BTreeMap<i64, GameObject>,
    nodes: BTreeMap<i64, Node>,
    /// GameObject -> its Transform.
    transform_of: BTreeMap<i64, i64>,
    world: std::sync::Mutex<BTreeMap<i64, Matrix>>,
}

/// The chains of parents are at most [`MAX_DEPTH`] long (a loop is a chain that does not end): a path, a world matrix
/// and the off flags are walked up the chain for each node, so a chain of d transforms costs d^2 of them and d paths
/// of d names.
/// A GameObject's `m_Layer`: 0 when it states none; a stored value outside 32 bits unsigned is refused.
fn layer_of(g: &Value) -> Result<u32> {
    let layer = g.get("m_Layer").and_then(Value::as_i64).unwrap_or(0);
    u32::try_from(layer).map_err(|_| invalid(format!("m_Layer {layer} is not a 32-bit unsigned number")))
}

/// A component's `m_CullingMask.m_Bits`: every layer when it states none. The 32 bits may be stored unsigned or as a
/// signed `int` (-1 is every layer); a number that fits neither is refused, not wrapped.
fn culling_mask(c: &Value, path_id: i64) -> Result<u32> {
    match c.at(&["m_CullingMask", "m_Bits"]).and_then(Value::as_i64) {
        None => Ok(u32::MAX),
        Some(bits) => u32::try_from(bits)
            .or_else(|_| i32::try_from(bits).map(|signed| u32::from_ne_bytes(signed.to_ne_bytes())))
            .map_err(|_| {
                invalid(format!(
                    "object {path_id}: m_CullingMask {bits} does not fit 32 bits"
                ))
            }),
    }
}

fn check_depth(nodes: &BTreeMap<i64, Node>) -> Result<()> {
    let mut depths: BTreeMap<i64, usize> = BTreeMap::new();
    for &start in nodes.keys() {
        let mut chain = Vec::new();
        let mut t = start;
        let base = loop {
            if let Some(&d) = depths.get(&t) {
                break d;
            }
            let Some(n) = nodes.get(&t) else { break 0 };
            chain.push(t);
            if chain.len() > MAX_DEPTH {
                return Err(invalid(format!(
                    "transform {start}: its parents are deeper than {MAX_DEPTH} (or loop)"
                )));
            }
            if n.father == 0 {
                break 0;
            }
            t = n.father;
        };
        if base.saturating_add(chain.len()) > MAX_DEPTH {
            return Err(invalid(format!(
                "transform {start}: its parents are deeper than {MAX_DEPTH}"
            )));
        }
        for (k, &t) in chain.iter().rev().enumerate() {
            depths.insert(t, base.saturating_add(k).saturating_add(1));
        }
    }
    Ok(())
}

impl Scene {
    /// The hierarchy of the scene file `file` (`level1`).
    pub fn read(player: &Player, file: &str) -> Result<Scene> {
        let f = player.file(file)?;
        let r = |file: &str, pid: i64| ObjRef {
            file: file.to_owned(),
            path_id: pid,
        };
        let name_of =
            |o: &crate::serialized::ObjectInfo| player.class_name(&r(file, o.path_id)).unwrap_or("");
        let mut nodes = BTreeMap::new();
        let mut rects: BTreeMap<i64, Value> = BTreeMap::new();
        let mut game_objects = BTreeMap::new();
        for o in &f.objects {
            match name_of(o) {
                "Transform" | "RectTransform" => {
                    let t = player.decode(&r(file, o.path_id))?;
                    let p = vec3(&t, "m_LocalPosition")?;
                    let q = t
                        .get("m_LocalRotation")
                        .ok_or_else(|| invalid("no m_LocalRotation"))?;
                    let q = [num(q, "x")?, num(q, "y")?, num(q, "z")?, num(q, "w")?];
                    let s = vec3(&t, "m_LocalScale")?;
                    nodes.insert(
                        o.path_id,
                        Node {
                            game_object: path_id(&t, "m_GameObject")?,
                            father: path_id(&t, "m_Father")?,
                            local: trs(p, q, s),
                            trs: (p, q, s),
                        },
                    );
                    if name_of(o) == "RectTransform" {
                        rects.insert(o.path_id, t);
                    }
                }
                "GameObject" => {
                    let g = player.decode(&r(file, o.path_id))?;
                    let components = values(&g, "m_Component")?
                        .iter()
                        .map(|c| path_id(c, "component"))
                        .collect::<Result<Vec<_>>>()?;
                    game_objects.insert(
                        o.path_id,
                        GameObject {
                            name: g.get("m_Name").and_then(Value::as_str).unwrap_or("").to_owned(),
                            active: flag(&g, "m_IsActive")?,
                            layer: layer_of(&g)?,
                            components,
                        },
                    );
                }
                _ => {}
            }
        }
        check_depth(&nodes)?;
        // RectTransforms: local x, y from the anchors
        let mut sizes: BTreeMap<i64, ([f64; 2], [f64; 2])> = BTreeMap::new();
        fn rect_size(
            tp: i64,
            rects: &BTreeMap<i64, Value>,
            nodes: &BTreeMap<i64, Node>,
            sizes: &mut BTreeMap<i64, ([f64; 2], [f64; 2])>,
            depth: u32,
        ) -> Result<([f64; 2], [f64; 2])> {
            if let Some(s) = sizes.get(&tp) {
                return Ok(*s);
            }
            let Some(t) = rects.get(&tp) else {
                return Ok(([0.0; 2], [0.0; 2]));
            };
            if depth > 4096 {
                return Err(invalid("RectTransform parents loop"));
            }
            let (sd, amin, amax, piv) = (
                vec2(t, "m_SizeDelta")?,
                vec2(t, "m_AnchorMin")?,
                vec2(t, "m_AnchorMax")?,
                vec2(t, "m_Pivot")?,
            );
            let fa = nodes.get(&tp).map_or(0, |n| n.father);
            let (ps, _) = if fa != 0 {
                rect_size(fa, rects, nodes, sizes, depth.saturating_add(1))?
            } else {
                ([0.0; 2], [0.0; 2])
            };
            let s = (
                [
                    ps[0] * (amax[0] - amin[0]) + sd[0],
                    ps[1] * (amax[1] - amin[1]) + sd[1],
                ],
                piv,
            );
            sizes.insert(tp, s);
            Ok(s)
        }
        let rect_ids: Vec<i64> = rects.keys().copied().collect();
        for tp in rect_ids {
            let missing = || invalid(format!("RectTransform {tp} is not a transform of the scene"));
            let t = rects.get(&tp).ok_or_else(missing)?;
            let fa = nodes.get(&tp).ok_or_else(missing)?.father;
            let (ps, ppiv) = if fa != 0 {
                rect_size(fa, &rects, &nodes, &mut sizes, 0)?
            } else {
                ([0.0; 2], [0.0; 2])
            };
            let (amin, amax, piv, ap) = (
                vec2(t, "m_AnchorMin")?,
                vec2(t, "m_AnchorMax")?,
                vec2(t, "m_Pivot")?,
                vec2(t, "m_AnchoredPosition")?,
            );
            let n = nodes.get_mut(&tp).ok_or_else(missing)?;
            let anchored = ppiv
                .iter()
                .zip(&ps)
                .zip(&amin)
                .zip(&amax)
                .zip(&piv)
                .zip(&ap)
                .map(|(((((&pp, &p), &lo), &hi), &pv), &a)| -pp * p + p * (lo + (hi - lo) * pv) + a);
            for (row, value) in n.local.iter_mut().zip(anchored) {
                if let Some(x) = row.get_mut(3) {
                    *x = value;
                }
            }
        }
        let transform_of = nodes.iter().map(|(&tp, n)| (n.game_object, tp)).collect();
        Ok(Scene {
            file: file.to_owned(),
            game_objects,
            nodes,
            transform_of,
            world: std::sync::Mutex::new(BTreeMap::new()),
        })
    }

    /// The MonoBehaviours of GameObject `go`, in its component order: the script (`namespace.class`, empty when it
    /// can't be resolved), `m_Enabled`, and the script's serialized fields as bytes (a stripped build has no type tree
    /// for them).
    pub fn behaviours_of(&self, player: &Player, go: i64) -> Result<Vec<UnityBehaviour>> {
        let mut out = Vec::new();
        for &c in self.game_objects.get(&go).map_or(&[][..], |g| &g.components) {
            let r = ObjRef {
                file: self.file.clone(),
                path_id: c,
            };
            if player.class_name(&r) != Some("MonoBehaviour") {
                continue;
            }
            let (base, data) = player.behaviour(&r)?;
            let script = match base.get("m_Script") {
                Some(p) => match player.resolve(&r.file, p)? {
                    Some(s) => {
                        let s = player.decode(&s)?;
                        let field = |k: &str| s.get(k).and_then(Value::as_str).unwrap_or("").to_owned();
                        let (ns, class) = (field("m_Namespace"), field("m_ClassName"));
                        if ns.is_empty() {
                            class
                        } else {
                            format!("{ns}.{class}")
                        }
                    }
                    None => String::new(),
                },
                None => String::new(),
            };
            out.push(UnityBehaviour {
                behaviour: r.clone(),
                script,
                enabled: base
                    .get("m_Enabled")
                    .and_then(Value::as_i64)
                    .is_some_and(|x| x != 0)
                    || base.get("m_Enabled").and_then(Value::as_bool) == Some(true),
                data,
            });
        }
        Ok(out)
    }

    /// Every MonoBehaviour of the scene, by GameObject (in path id order), as [`Scene::behaviours_of`] gives them.
    pub fn behaviours(&self, player: &Player) -> Result<Vec<(i64, UnityBehaviour)>> {
        let mut out = Vec::new();
        for &go in self.game_objects.keys() {
            out.extend(self.behaviours_of(player, go)?.into_iter().map(|b| (go, b)));
        }
        Ok(out)
    }

    /// The world matrices computed so far. A thread that panicked holding the lock can leave nothing half-written (an
    /// entry is inserted whole), so a poisoned lock is still a valid cache.
    fn world_cache(&self) -> std::sync::MutexGuard<'_, BTreeMap<i64, Matrix>> {
        self.world
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
    }

    /// The Transform of the GameObject `root` that a query is limited to; `None` for a query of the whole file. A
    /// GameObject without a Transform is an error, not an empty or an unlimited query.
    fn root_transform(&self, root: Option<i64>) -> Result<Option<i64>> {
        root.map(|go| {
            self.transform_of(go)
                .ok_or_else(|| invalid(format!("GameObject {go} has no transform")))
        })
        .transpose()
    }

    /// A Transform's world matrix (Unity frame).
    pub fn world_of(&self, tp: i64) -> Result<Matrix> {
        let mut chain = Vec::new();
        let mut t = tp;
        let base = loop {
            if let Some(m) = self.world_cache().get(&t) {
                break *m;
            }
            let Some(n) = self.nodes.get(&t) else {
                break IDENTITY;
            };
            chain.push(t);
            if chain.len() > self.nodes.len() {
                return Err(invalid(format!("transform {tp}: parents loop")));
            }
            if n.father == 0 {
                break IDENTITY;
            }
            t = n.father;
        };
        let mut m = base;
        let mut cache = self.world_cache();
        for &t in chain.iter().rev() {
            let node = self
                .nodes
                .get(&t)
                .ok_or_else(|| invalid(format!("transform {t} on the chain of {tp} is not in the scene")))?;
            m = mul(&m, &node.local);
            cache.insert(t, m);
        }
        Ok(m)
    }

    /// The off flags of a component on Transform `tp`'s GameObject: the GameObjects stored inactive from the root down,
    /// then the component (`(path id, enabled)`) when it is stored disabled.
    pub fn off_flags(&self, tp: i64, component: Option<(i64, bool)>) -> Vec<OffFlag> {
        let mut out = Vec::new();
        let mut t = tp;
        for _ in 0..=self.nodes.len() {
            let Some(n) = self.nodes.get(&t) else { break };
            if !self.game_objects.get(&n.game_object).is_some_and(|g| g.active) {
                out.push(OffFlag::Inactive(n.game_object));
            }
            if n.father == 0 {
                break;
            }
            t = n.father;
        }
        out.reverse();
        if let Some((c, false)) = component {
            out.push(OffFlag::Disabled(c));
        }
        out
    }

    /// Whether a Transform's GameObject and all its ancestors' are active.
    pub fn active(&self, tp: i64) -> bool {
        let mut t = tp;
        for _ in 0..=self.nodes.len() {
            let Some(n) = self.nodes.get(&t) else { return true };
            if !self.game_objects.get(&n.game_object).is_some_and(|g| g.active) {
                return false;
            }
            if n.father == 0 {
                return true;
            }
            t = n.father;
        }
        false
    }

    /// The GameObject path of a Transform, names from the root joined by `/`.
    pub fn path(&self, tp: i64) -> String {
        let mut parts = Vec::new();
        let mut t = tp;
        while let Some(n) = self.nodes.get(&t) {
            parts.push(
                self.game_objects
                    .get(&n.game_object)
                    .map_or("", |g| g.name.as_str()),
            );
            if n.father == 0 || parts.len() > self.nodes.len() {
                break;
            }
            t = n.father;
        }
        parts.reverse();
        parts.join("/")
    }

    /// The Transform of a GameObject (both path ids).
    pub fn transform_of(&self, game_object: i64) -> Option<i64> {
        self.transform_of.get(&game_object).copied()
    }

    /// A GameObject and the GameObjects above it on its Transform chain, itself first, the root last; a GameObject
    /// without a Transform is alone.
    pub fn ancestors(&self, game_object: i64) -> Vec<i64> {
        let mut out = vec![game_object];
        let Some(mut t) = self.transform_of(game_object) else {
            return out;
        };
        while let Some(n) = self.nodes.get(&t) {
            if n.father == 0 || out.len() > self.nodes.len() {
                break;
            }
            t = n.father;
            match self.nodes.get(&t) {
                Some(p) => out.push(p.game_object),
                None => break,
            }
        }
        out
    }

    /// Transform `tp` as a joint ([`SceneJoint`]); `None` when it is no Transform of this file. A RectTransform's
    /// position is the one its anchors give (as in its local matrix), its rotation and scale as stored.
    pub fn joint(&self, tp: i64) -> Result<Option<SceneJoint>> {
        let Some(n) = self.nodes.get(&tp) else {
            return Ok(None);
        };
        Ok(Some(SceneJoint {
            name: self
                .game_objects
                .get(&n.game_object)
                .map_or("", |g| g.name.as_str())
                .to_owned(),
            father: (n.father != 0).then_some(n.father),
            translation: [n.local[0][3], n.local[1][3], n.local[2][3]],
            rotation: n.trs.1,
            scale: n.trs.2,
        }))
    }

    /// The characters of the file: its Animators with skinned renderers below them, in the order of its object table.
    pub fn characters(&self, player: &Player) -> Result<Vec<Character>> {
        let file = self.file.as_str();
        let r = |pid: i64| ObjRef {
            file: file.to_owned(),
            path_id: pid,
        };
        let mut skinned = Vec::new();
        for o in &player.file(file)?.objects {
            if player.class_name(&r(o.path_id)) == Some("SkinnedMeshRenderer") {
                let go = path_id(&player.decode(&r(o.path_id))?, "m_GameObject")?;
                skinned.extend(self.transform_of(go));
            }
        }
        let mut out = Vec::new();
        for animator in self.animators(player)? {
            let Some(tp) = self.transform_of(animator.game_object) else {
                continue;
            };
            let count = skinned
                .iter()
                .filter(|&&s| self.relative_to(s, tp).is_some())
                .count();
            if count > 0 {
                out.push(Character {
                    animator,
                    skinned_renderers: count,
                });
            }
        }
        Ok(out)
    }

    /// The names of the GameObjects from the child of Transform `root` down to Transform `tp` joined by `/` (empty
    /// for `root` itself): a path as an Animator's clips name their targets. `None` when `root` is not `tp` or one of
    /// its ancestors.
    pub fn path_below(&self, tp: i64, root: i64) -> Option<String> {
        let mut names = Vec::new();
        let mut t = tp;
        while t != root {
            let n = self.nodes.get(&t)?;
            names.push(
                self.game_objects
                    .get(&n.game_object)
                    .map_or("", |g| g.name.as_str()),
            );
            if n.father == 0 || names.len() > self.nodes.len() {
                return None;
            }
            t = n.father;
        }
        names.reverse();
        Some(names.join("/"))
    }

    /// The Animators of the file, in the order of its object table.
    pub fn animators(&self, player: &Player) -> Result<Vec<Animator>> {
        self.animators_under(player, None)
    }

    /// The Animators on the GameObject `root` and its descendants (a prefab's), all of the file's with `None`.
    pub fn animators_under(&self, player: &Player, root: Option<i64>) -> Result<Vec<Animator>> {
        let root_tp = self.root_transform(root)?;
        let file = self.file.as_str();
        let r = |pid: i64| ObjRef {
            file: file.to_owned(),
            path_id: pid,
        };
        let mut out = Vec::new();
        for o in &player.file(file)?.objects {
            if player.class_name(&r(o.path_id)) != Some("Animator") {
                continue;
            }
            let a = player.decode(&r(o.path_id))?;
            let go = path_id(&a, "m_GameObject")?;
            let Some(tp) = self.transform_of(go) else {
                continue;
            };
            if root_tp.is_some_and(|r| self.relative_to(tp, r).is_none()) {
                continue;
            }
            let pointer = |k: &str| -> Result<Option<ObjRef>> {
                a.get(k)
                    .map(|p| player.resolve(file, p))
                    .transpose()
                    .map(Option::flatten)
            };
            out.push(Animator {
                animator: r(o.path_id),
                game_object: go,
                path: self.path(tp),
                controller: pointer("m_Controller")?,
                avatar: pointer("m_Avatar")?,
                enabled: a.get("m_Enabled").is_none_or(flag_value),
                apply_root_motion: a.get("m_ApplyRootMotion").is_some_and(flag_value),
            });
        }
        Ok(out)
    }

    /// A Transform's local matrix.
    pub fn local_of(&self, tp: i64) -> Option<Matrix> {
        self.nodes.get(&tp).map(|n| n.local)
    }

    /// The matrix of Transform `tp` relative to its ancestor `root` (the product of the locals below `root`), or
    /// `None` when `root` is not `tp` or an ancestor of it.
    pub fn relative_to(&self, tp: i64, root: i64) -> Option<Matrix> {
        let mut chain = Vec::new();
        let mut t = tp;
        while t != root {
            let n = self.nodes.get(&t)?;
            chain.push(t);
            if n.father == 0 || chain.len() > self.nodes.len() {
                return None;
            }
            t = n.father;
        }
        chain
            .iter()
            .rev()
            .try_fold(IDENTITY, |m, t| Some(mul(&m, &self.nodes.get(t)?.local)))
    }

    /// The mesh renderers, in the order of the scene's object table, and what was skipped (no transform, no
    /// MeshFilter, no mesh).
    pub fn renderers(&self, player: &Player) -> Result<(Vec<Renderer>, Skipped)> {
        self.renderers_under(player, None)
    }

    /// The LODGroups of the GameObject `root` and its descendants (a prefab's), all of the file's with `None`, in the
    /// order of the object table.
    pub fn lod_groups_under(&self, player: &Player, root: Option<i64>) -> Result<Vec<LodGroup>> {
        let root_tp = self.root_transform(root)?;
        let file = self.file.as_str();
        let f = player.file(file)?;
        let r = |pid: i64| ObjRef {
            file: file.to_owned(),
            path_id: pid,
        };
        let mut out = Vec::new();
        for o in f
            .objects
            .iter()
            .filter(|o| player.class_name(&r(o.path_id)) == Some("LODGroup"))
        {
            let g = player.decode(&r(o.path_id))?;
            let Some(tp) = self.transform_of(path_id(&g, "m_GameObject")?) else {
                continue;
            };
            if root_tp.is_some_and(|root| self.relative_to(tp, root).is_none()) {
                continue;
            }
            let enabled = flag(&g, "m_Enabled")?;
            let mut levels = Vec::new();
            for lod in values(&g, "m_LODs")? {
                let mut level = Vec::new();
                for x in values(lod, "renderers")? {
                    let pid = path_id(x, "renderer")?;
                    if pid != 0 {
                        level.push(pid);
                    }
                }
                levels.push(level);
            }
            out.push(LodGroup {
                group: r(o.path_id),
                path: self.path(tp),
                enabled,
                off: self.off_flags(tp, Some((o.path_id, enabled))),
                levels,
            });
        }
        Ok(out)
    }

    /// The mesh renderers of the GameObject `root` and its descendants (a prefab's), their matrices relative to
    /// `root`; all of the file's with `None`.
    pub fn renderers_under(&self, player: &Player, root: Option<i64>) -> Result<(Vec<Renderer>, Skipped)> {
        let root_tp = self.root_transform(root)?;
        let file = self.file.as_str();
        let f = player.file(file)?;
        let r = |pid: i64| ObjRef {
            file: file.to_owned(),
            path_id: pid,
        };
        let class = |pid: i64| player.class_name(&r(pid)).unwrap_or("");
        let mut out = Vec::new();
        let mut skipped = Skipped::new();
        for o in f
            .objects
            .iter()
            .filter(|o| matches!(class(o.path_id), "MeshRenderer" | "SkinnedMeshRenderer"))
        {
            let skinned = class(o.path_id) == "SkinnedMeshRenderer";
            let mr = player.decode(&r(o.path_id))?;
            let go = path_id(&mr, "m_GameObject")?;
            let Some(tp) = self.transform_of(go) else {
                bump(&mut skipped, "no transform");
                continue;
            };
            let relative = match root_tp {
                Some(root) => match self.relative_to(tp, root) {
                    Some(m) => Some(m),
                    None => continue,
                },
                None => None,
            };
            let off = self.off_flags(tp, Some((o.path_id, flag(&mr, "m_Enabled")?)));
            let g = self.game_objects.get(&go).ok_or_else(|| {
                invalid(format!(
                    "GameObject {go} of renderer {} is not in the scene",
                    o.path_id
                ))
            })?;
            // a skinned renderer holds its mesh itself; a mesh renderer's is on its MeshFilter
            let filter;
            let mesh_ptr = if skinned {
                mr.get("m_Mesh")
                    .ok_or_else(|| invalid("SkinnedMeshRenderer without m_Mesh"))?
            } else {
                let Some(&mf) = g.components.iter().find(|&&c| class(c) == "MeshFilter") else {
                    bump(&mut skipped, "no MeshFilter");
                    continue;
                };
                filter = player.decode(&r(mf))?;
                filter
                    .get("m_Mesh")
                    .ok_or_else(|| invalid("MeshFilter without m_Mesh"))?
            };
            let Some(mesh) = player.resolve(file, mesh_ptr)? else {
                bump(&mut skipped, "null mesh");
                continue;
            };
            let materials = values(&mr, "m_Materials")?
                .iter()
                .map(|m| player.resolve(file, m))
                .collect::<Result<Vec<_>>>()?;
            let sb = mr.get("m_StaticBatchInfo");
            let first = sb
                .and_then(|s| s.get("firstSubMesh"))
                .and_then(Value::as_i64)
                .unwrap_or(0);
            let count = sb
                .and_then(|s| s.get("subMeshCount"))
                .and_then(Value::as_i64)
                .unwrap_or(0);
            let submeshes = if count > 0 {
                let to_u32 = |n: i64, k: &str| {
                    u32::try_from(n).map_err(|_| {
                        invalid(format!("renderer {}: {k} {n} is not 32-bit unsigned", o.path_id))
                    })
                };
                Some((to_u32(first, "firstSubMesh")?, to_u32(count, "subMeshCount")?))
            } else {
                None
            };
            let skin = if skinned {
                let bone = |p: &Value| -> Result<Option<i64>> {
                    let pid = p
                        .get("m_PathID")
                        .and_then(Value::as_i64)
                        .ok_or_else(|| invalid("a bone pointer without m_PathID"))?;
                    if p.get("m_FileID").and_then(Value::as_i64).unwrap_or(0) != 0 {
                        return Err(invalid(format!(
                            "SkinnedMeshRenderer {}: a bone in another file",
                            o.path_id
                        )));
                    }
                    Ok((pid != 0).then_some(pid))
                };
                Some(RendererSkin {
                    bones: values(&mr, "m_Bones")?.iter().map(bone).collect::<Result<_>>()?,
                    root_bone: match mr.get("m_RootBone") {
                        Some(p) => bone(p)?,
                        None => None,
                    },
                    blend_weights: match mr.get("m_BlendShapeWeights") {
                        Some(Value::Array(Array::F32(w))) => w.clone(),
                        Some(Value::Array(a)) if a.is_empty() => Vec::new(),
                        None => Vec::new(),
                        _ => return Err(invalid("SkinnedMeshRenderer: m_BlendShapeWeights not floats")),
                    },
                })
            } else {
                None
            };
            out.push(Renderer {
                renderer: r(o.path_id),
                game_object: go,
                path: self.path(tp),
                layer: g.layer,
                mesh,
                materials,
                world: if submeshes.is_some() {
                    IDENTITY
                } else {
                    match relative {
                        Some(m) => m,
                        None => self.world_of(tp)?,
                    }
                },
                submeshes,
                cast_shadows: mr.get("m_CastShadows").and_then(Value::as_i64).unwrap_or(1),
                receive_shadows: mr.get("m_ReceiveShadows").and_then(Value::as_i64).map(|v| v != 0),
                off,
                skin,
            });
        }
        Ok((out, skipped))
    }

    /// The Rigidbody on Transform `tp`'s GameObject or its nearest ancestor's: `Some(kinematic)`.
    fn rigidbody(&self, player: &Player, tp: i64) -> Result<Option<bool>> {
        let r = |pid: i64| ObjRef {
            file: self.file.clone(),
            path_id: pid,
        };
        let mut t = tp;
        for _ in 0..=self.nodes.len() {
            let Some(n) = self.nodes.get(&t) else {
                return Ok(None);
            };
            if let Some(g) = self.game_objects.get(&n.game_object)
                && let Some(&rb) = g
                    .components
                    .iter()
                    .find(|&&c| player.class_name(&r(c)) == Some("Rigidbody"))
            {
                return Ok(Some(flag(&player.decode(&r(rb))?, "m_IsKinematic")?));
            }
            if n.father == 0 {
                return Ok(None);
            }
            t = n.father;
        }
        Ok(None)
    }

    /// Every Box, Sphere, Capsule and Mesh collider of the GameObject `root` and its descendants (a prefab's, matrices
    /// relative to `root`), or of the whole file with `None`, in the order of the object table: those that do not
    /// collide (inactive, disabled, triggers) included, flagged.
    pub fn colliders_under(&self, player: &Player, root: Option<i64>) -> Result<Vec<ColliderComponent>> {
        let file = self.file.as_str();
        let f = player.file(file)?;
        let r = |pid: i64| ObjRef {
            file: file.to_owned(),
            path_id: pid,
        };
        let root_tp = self.root_transform(root)?;
        let v3 = |v: &Value, k: &str| -> Result<[f64; 3]> { vec3(v, k) };
        let mut out = Vec::new();
        for o in &f.objects {
            let class = player.class_name(&r(o.path_id)).unwrap_or("");
            if !matches!(
                class,
                "BoxCollider" | "SphereCollider" | "CapsuleCollider" | "MeshCollider"
            ) {
                continue;
            }
            let c = player.decode(&r(o.path_id))?;
            let go = path_id(&c, "m_GameObject")?;
            let Some(tp) = self.transform_of(go) else { continue };
            let world = match root_tp {
                Some(root) => match self.relative_to(tp, root) {
                    Some(m) => m,
                    None => continue,
                },
                None => self.world_of(tp)?,
            };
            let fl = |k: &str| -> Result<f64> { num(&c, k) };
            let shape = match class {
                "BoxCollider" => ColliderShape::Box {
                    center: v3(&c, "m_Center")?,
                    size: v3(&c, "m_Size")?,
                },
                "SphereCollider" => ColliderShape::Sphere {
                    center: v3(&c, "m_Center")?,
                    radius: fl("m_Radius")?,
                },
                "CapsuleCollider" => ColliderShape::Capsule {
                    center: v3(&c, "m_Center")?,
                    radius: fl("m_Radius")?,
                    height: fl("m_Height")?,
                    direction: match c.get("m_Direction").and_then(Value::as_i64).unwrap_or(1) {
                        d @ 0..=2 => usize::try_from(d).unwrap_or_default(),
                        d => {
                            return Err(invalid(format!(
                                "CapsuleCollider {}: m_Direction {d} is not 0, 1 or 2",
                                o.path_id
                            )));
                        }
                    },
                },
                _ => ColliderShape::Mesh {
                    mesh: match c.get("m_Mesh") {
                        Some(p) => player.resolve(file, p)?,
                        None => None,
                    },
                    convex: flag(&c, "m_Convex")?,
                },
            };
            out.push(ColliderComponent {
                collider: r(o.path_id),
                path: self.path(tp),
                layer: self.game_objects.get(&go).map_or(0, |g| g.layer),
                world,
                shape,
                off: self.off_flags(tp, Some((o.path_id, flag(&c, "m_Enabled")?))),
                trigger: c.get("m_IsTrigger").is_some_and(flag_value),
                physic_material: match c.get("m_Material") {
                    Some(p) => player.resolve(file, p)?,
                    None => None,
                },
                rigidbody: self.rigidbody(player, tp)?,
            });
        }
        Ok(out)
    }

    /// The scene's RenderSettings: the Light it names as its sun (`m_Sun`; `None` when it names none: Unity then
    /// lights its procedural sky by the brightest directional light, a choice of the engine's, not the scene's) and
    /// its ambient lighting. `None` when the scene has no RenderSettings.
    pub fn render_settings(&self, player: &Player) -> Result<Option<SceneRenderSettings>> {
        let file = self.file.as_str();
        let f = player.file(file)?;
        let r = |pid: i64| ObjRef {
            file: file.to_owned(),
            path_id: pid,
        };
        let mut found = None;
        for o in &f.objects {
            if player.class_name(&r(o.path_id)) != Some("RenderSettings") {
                continue;
            }
            if found.is_some() {
                return Err(invalid(format!("{file}: more than one RenderSettings")));
            }
            let settings = player.decode(&r(o.path_id))?;
            let sun = match settings.get("m_Sun") {
                Some(p) => player.resolve(file, p)?,
                None => None,
            };
            let rgba = |k: &str| -> Result<[f32; 4]> {
                let c = settings
                    .get(k)
                    .ok_or_else(|| invalid(format!("{file}: RenderSettings without {k}")))?;
                Ok([num(c, "r")?, num(c, "g")?, num(c, "b")?, num(c, "a")?].map(crate::narrow))
            };
            let ambient = match settings.get("m_AmbientMode").and_then(Value::as_i64) {
                None => None,
                Some(mode) => Some(UnityAmbient {
                    mode,
                    sky: rgba("m_AmbientSkyColor")?,
                    equator: rgba("m_AmbientEquatorColor")?,
                    ground: rgba("m_AmbientGroundColor")?,
                    intensity: settings
                        .get("m_AmbientIntensity")
                        .and_then(Value::as_f32)
                        .ok_or_else(|| {
                            invalid(format!("{file}: RenderSettings without m_AmbientIntensity"))
                        })?,
                    probe: match settings.get("m_AmbientProbe") {
                        None => None,
                        Some(sh) => {
                            let mut out = [0.0f32; 27];
                            for (i, c) in out.iter_mut().enumerate() {
                                // the type tree names the coefficients `sh[ 0]` .. `sh[26]`
                                *c = sh.get(&format!("sh[{i:2}]")).and_then(Value::as_f32).ok_or_else(
                                    || {
                                        invalid(format!(
                                            "{file}: RenderSettings' m_AmbientProbe without sh[{i:2}]"
                                        ))
                                    },
                                )?;
                            }
                            Some(out)
                        }
                    },
                }),
            };
            // fog: absent from a type tree that does not state it
            let fog = match settings.get("m_Fog").and_then(Value::as_bool) {
                None => None,
                Some(enabled) => Some(UnityFog {
                    enabled,
                    mode: settings
                        .get("m_FogMode")
                        .and_then(Value::as_i64)
                        .ok_or_else(|| invalid(format!("{file}: RenderSettings without m_FogMode")))?,
                    color: rgba("m_FogColor")?,
                    density: crate::narrow(num(&settings, "m_FogDensity")?),
                    start: crate::narrow(num(&settings, "m_LinearFogStart")?),
                    end: crate::narrow(num(&settings, "m_LinearFogEnd")?),
                }),
            };
            found = Some(SceneRenderSettings { sun, ambient, fog });
        }
        Ok(found)
    }

    /// The lights, whatever their state, in the order of the scene's object table.
    pub fn lights(&self, player: &Player) -> Result<Vec<LightComponent>> {
        let file = self.file.as_str();
        let f = player.file(file)?;
        let r = |pid: i64| ObjRef {
            file: file.to_owned(),
            path_id: pid,
        };
        let class = |pid: i64| player.class_name(&r(pid)).unwrap_or("");
        let mut out = Vec::new();
        for o in f.objects.iter().filter(|o| class(o.path_id) == "Light") {
            let l = player.decode(&r(o.path_id))?;
            let Some(tp) = self.transform_of(path_id(&l, "m_GameObject")?) else {
                continue;
            };
            let off = self.off_flags(tp, Some((o.path_id, flag(&l, "m_Enabled")?)));
            let fl = |k: &str| l.get(k).and_then(Value::as_f32);
            let int = |k: &str| l.get(k).and_then(Value::as_i64);
            let c = l.get("m_Color").ok_or_else(|| invalid("light: no m_Color"))?;
            let area = l.get("m_AreaSize");
            out.push(LightComponent {
                light: r(o.path_id),
                path: self.path(tp),
                world: self.world_of(tp)?,
                kind: int("m_Type").ok_or_else(|| invalid("light: no m_Type"))?,
                color: [num(c, "r")?, num(c, "g")?, num(c, "b")?, num(c, "a")?].map(crate::narrow),
                intensity: fl("m_Intensity").unwrap_or(1.0),
                range: fl("m_Range").unwrap_or(10.0),
                spot_angle: fl("m_SpotAngle").unwrap_or(30.0),
                inner_spot_angle: fl("m_InnerSpotAngle").unwrap_or(0.0),
                shadows: l
                    .at(&["m_Shadows", "m_Type"])
                    .and_then(Value::as_i64)
                    .unwrap_or(0),
                color_temperature: if l
                    .get("m_UseColorTemperature")
                    .is_some_and(|v| v.as_bool() == Some(true) || v.as_i64() == Some(1))
                {
                    fl("m_ColorTemperature")
                } else {
                    None
                },
                bounce_intensity: fl("m_BounceIntensity").unwrap_or(1.0),
                light_unit: int("m_LightUnit"),
                lux_at_distance: fl("m_LuxAtDistance"),
                area_size: [
                    area.and_then(|a| a.get("x"))
                        .and_then(Value::as_f32)
                        .unwrap_or(1.0),
                    area.and_then(|a| a.get("y"))
                        .and_then(Value::as_f32)
                        .unwrap_or(1.0),
                ],
                render_mode: int("m_RenderMode").unwrap_or(0),
                baked: l.at(&["m_BakingOutput", "isBaked"]).is_some_and(flag_value)
                    && l.at(&["m_BakingOutput", "lightmapBakeMode", "lightmapBakeType"])
                        .and_then(Value::as_i64)
                        == Some(2),
                culling_mask: culling_mask(&l, o.path_id)?,
                cookie: match l.get("m_Cookie") {
                    Some(p) => player.resolve(file, p)?,
                    None => None,
                },
                off,
            });
        }
        Ok(out)
    }

    /// The cameras, whatever their state, in the order of the scene's object table.
    pub fn cameras(&self, player: &Player) -> Result<Vec<CameraComponent>> {
        let file = self.file.as_str();
        let f = player.file(file)?;
        let r = |pid: i64| ObjRef {
            file: file.to_owned(),
            path_id: pid,
        };
        let class = |pid: i64| player.class_name(&r(pid)).unwrap_or("");
        let mut out = Vec::new();
        for o in f.objects.iter().filter(|o| class(o.path_id) == "Camera") {
            let c = player.decode(&r(o.path_id))?;
            let Some(tp) = self.transform_of(path_id(&c, "m_GameObject")?) else {
                continue;
            };
            out.push(CameraComponent {
                camera: r(o.path_id),
                path: self.path(tp),
                world: self.world_of(tp)?,
                culling_mask: culling_mask(&c, o.path_id)?,
                target_texture: match c.get("m_TargetTexture") {
                    Some(p) => player.resolve(file, p)?,
                    None => None,
                },
                off: self.off_flags(tp, Some((o.path_id, flag(&c, "m_Enabled")?))),
            });
        }
        Ok(out)
    }

    /// The terrains, whatever their state, in the order of the scene's object table, and what was skipped (no transform,
    /// no terrain data: a Terrain that names no TerrainData draws nothing).
    pub fn terrains(&self, player: &Player) -> Result<(Vec<TerrainComponent>, Skipped)> {
        let file = self.file.as_str();
        let f = player.file(file)?;
        let r = |pid: i64| ObjRef {
            file: file.to_owned(),
            path_id: pid,
        };
        let class = |pid: i64| player.class_name(&r(pid)).unwrap_or("");
        let mut out = Vec::new();
        let mut skipped = Skipped::new();
        for o in f.objects.iter().filter(|o| class(o.path_id) == "Terrain") {
            let t = player.decode(&r(o.path_id))?;
            let go = path_id(&t, "m_GameObject")?;
            let Some(tp) = self.transform_of(go) else {
                bump(&mut skipped, "no transform");
                continue;
            };
            let off = self.off_flags(tp, Some((o.path_id, flag(&t, "m_Enabled")?)));
            let pptr = |v: &Value, k: &str| -> Result<Option<ObjRef>> {
                match v.get(k) {
                    Some(p) => player.resolve(file, p),
                    None => Ok(None),
                }
            };
            let Some(data) = pptr(&t, "m_TerrainData")? else {
                bump(&mut skipped, "no terrain data");
                continue;
            };
            let collider = match self
                .game_objects
                .get(&go)
                .ok_or_else(|| {
                    invalid(format!(
                        "GameObject {go} of terrain {} is not in the scene",
                        o.path_id
                    ))
                })?
                .components
                .iter()
                .find(|&&c| class(c) == "TerrainCollider")
            {
                Some(&c) => {
                    let tc = player.decode(&r(c))?;
                    Some(TerrainColliderComponent {
                        collider: r(c),
                        enabled: flag(&tc, "m_Enabled")?,
                        data: pptr(&tc, "m_TerrainData")?,
                        material: pptr(&tc, "m_Material")?,
                        tree_colliders: flag(&tc, "m_EnableTreeColliders")?,
                    })
                }
                None => None,
            };
            out.push(TerrainComponent {
                terrain: r(o.path_id),
                path: self.path(tp),
                world: self.world_of(tp)?,
                data,
                material: pptr(&t, "m_MaterialTemplate")?,
                draw_heightmap: flag(&t, "m_DrawHeightmap")?,
                draw_trees: flag(&t, "m_DrawTreesAndFoliage")?,
                collider,
                off,
            });
        }
        Ok((out, skipped))
    }
}

/// A collider's shape as stored, in its GameObject's space (Unity's frame).
#[derive(Clone, Debug, PartialEq)]
pub enum ColliderShape {
    /// A box collider.
    Box {
        /// `m_Center`: the box's centre in its GameObject's space.
        center: [f64; 3],
        /// `m_Size`: the full edge lengths along x, y and z (not half-extents), before the GameObject's scale.
        size: [f64; 3],
    },
    /// A sphere collider.
    Sphere {
        /// `m_Center`: the sphere's centre in its GameObject's space.
        center: [f64; 3],
        /// `m_Radius`, before the GameObject's scale.
        radius: f64,
    },
    /// A capsule collider.
    Capsule {
        /// `m_Center`: the capsule's centre in its GameObject's space.
        center: [f64; 3],
        /// `m_Radius`, before the GameObject's scale.
        radius: f64,
        /// `m_Height`, including the caps, before the GameObject's scale.
        height: f64,
        /// `m_Direction`: the axis the height runs along (0 x, 1 y, 2 z).
        direction: usize,
    },
    /// A mesh collider.
    Mesh {
        /// `m_Mesh`; `None` for a null pointer.
        mesh: Option<ObjRef>,
        /// `m_Convex`.
        convex: bool,
    },
}

/// A collider as stored: its shape, its off flags, whether it is a trigger, its physic material, and the Rigidbody on
/// it or its nearest ancestor (`Some(true)`: kinematic).
#[derive(Clone, Debug, PartialEq)]
pub struct ColliderComponent {
    /// The collider object.
    pub collider: ObjRef,
    /// Its GameObject's path from the scene root, names joined by `/`.
    pub path: String,
    /// Its GameObject's layer.
    pub layer: u32,
    /// The matrix of its GameObject: world, or relative to `root` when one was given.
    pub world: Matrix,
    /// The shape.
    pub shape: ColliderShape,
    /// What keeps it from colliding; collides when empty.
    pub off: Vec<OffFlag>,
    /// `m_IsTrigger`.
    pub trigger: bool,
    /// `m_Material`.
    pub physic_material: Option<ObjRef>,
    /// The nearest Rigidbody: `Some(kinematic)`; `None` when there is none.
    pub rigidbody: Option<bool>,
}

/// A light as stored: Unity's LightType (0 spot, 1 directional, 2 point, 3 rectangle, 4 disc), colour as stored
/// (gamma-encoded), intensity, range, spot angles in degrees (full cone), shadow type, colour temperature (Kelvin, when
/// used), bounce intensity, URP's light unit and lux-at-distance, area size, render mode and culling mask.
#[derive(Clone, Debug, PartialEq)]
pub struct LightComponent {
    /// The Light object.
    pub light: ObjRef,
    /// Its GameObject's path from the scene root, names joined by `/`.
    pub path: String,
    /// Its GameObject's world matrix.
    pub world: Matrix,
    /// `m_Type`.
    pub kind: i64,
    /// `m_Color`, RGBA.
    pub color: [f32; 4],
    /// `m_Intensity` (1 when not stored).
    pub intensity: f32,
    /// `m_Range` (10 when not stored).
    pub range: f32,
    /// `m_SpotAngle` (30 when not stored).
    pub spot_angle: f32,
    /// `m_InnerSpotAngle` (0 when not stored).
    pub inner_spot_angle: f32,
    /// `m_Shadows.m_Type` (0 when not stored).
    pub shadows: i64,
    /// `m_ColorTemperature`, when `m_UseColorTemperature` is on.
    pub color_temperature: Option<f32>,
    /// `m_BounceIntensity` (1 when not stored).
    pub bounce_intensity: f32,
    /// `m_LightUnit`, when stored.
    pub light_unit: Option<i64>,
    /// `m_LuxAtDistance`, when stored.
    pub lux_at_distance: Option<f32>,
    /// `m_AreaSize` (1 x 1 when not stored).
    pub area_size: [f32; 2],
    /// `m_RenderMode` (0 when not stored).
    pub render_mode: i64,
    /// Fully baked: `m_BakingOutput` says baked, as `Baked` (2), not mixed or realtime.
    pub baked: bool,
    /// `m_CullingMask`'s bits (all layers when not stored).
    pub culling_mask: u32,
    /// `m_Cookie`.
    pub cookie: Option<ObjRef>,
    /// What keeps it from shining; shines when empty.
    pub off: Vec<OffFlag>,
}

/// A camera as stored: its culling mask (`m_CullingMask`, the layers it draws; all when absent) and the texture it
/// renders into (`m_TargetTexture`; `None`: it draws to the screen).
#[derive(Clone, Debug, PartialEq)]
pub struct CameraComponent {
    /// The Camera object.
    pub camera: ObjRef,
    /// Its GameObject's path from the scene root, names joined by `/`.
    pub path: String,
    /// Its GameObject's world matrix.
    pub world: Matrix,
    /// `m_CullingMask.m_Bits`: bit n set draws layer n (all 32 bits when not stored).
    pub culling_mask: u32,
    /// `m_TargetTexture`; `None` when it draws to the screen.
    pub target_texture: Option<ObjRef>,
    /// What keeps it from drawing; draws when empty.
    pub off: Vec<OffFlag>,
}

/// A terrain's collider: its own TerrainData (which may differ from the drawn one), physic material, tree colliders.
#[derive(Clone, Debug, PartialEq)]
pub struct TerrainColliderComponent {
    /// The TerrainCollider object.
    pub collider: ObjRef,
    /// `m_Enabled`.
    pub enabled: bool,
    /// `m_TerrainData`.
    pub data: Option<ObjRef>,
    /// `m_Material`.
    pub material: Option<ObjRef>,
    /// `m_EnableTreeColliders`.
    pub tree_colliders: bool,
}

/// A terrain, whatever its state: its GameObject's path and world matrix (a terrain is placed by its position only),
/// its data, material, collider and off flags (drawn when empty).
#[derive(Clone, Debug, PartialEq)]
pub struct TerrainComponent {
    /// The Terrain object.
    pub terrain: ObjRef,
    /// Its GameObject's path from the scene root, names joined by `/`.
    pub path: String,
    /// Its GameObject's world matrix.
    pub world: Matrix,
    /// `m_TerrainData`, read with [`crate::terrain::TerrainData::read`].
    pub data: ObjRef,
    /// `m_MaterialTemplate`.
    pub material: Option<ObjRef>,
    /// `m_DrawHeightmap`.
    pub draw_heightmap: bool,
    /// `m_DrawTreesAndFoliage`.
    pub draw_trees: bool,
    /// The terrain's TerrainCollider, if its GameObject has one.
    pub collider: Option<TerrainColliderComponent>,
    /// What keeps it from being drawn; drawn when empty.
    pub off: Vec<OffFlag>,
}

/// A scene's RenderSettings as read ([`Scene::render_settings`]).
#[derive(Clone, Debug, PartialEq)]
pub struct SceneRenderSettings {
    /// `m_Sun`: the Light the scene names as its sun.
    pub sun: Option<ObjRef>,
    /// The ambient lighting; `None` when the RenderSettings state no `m_AmbientMode`.
    pub ambient: Option<UnityAmbient>,
    /// The fog; `None` when the RenderSettings state no `m_Fog`.
    pub fog: Option<UnityFog>,
}

#[cfg(test)]
mod tests {
    use super::*;

    fn chain(len: i64) -> BTreeMap<i64, Node> {
        (1..=len)
            .map(|id| {
                let node = Node {
                    game_object: id,
                    father: if id == 1 { 0 } else { id - 1 },
                    local: IDENTITY,
                    trs: ([0.0; 3], [0.0, 0.0, 0.0, 1.0], [1.0; 3]),
                };
                (id, node)
            })
            .collect()
    }

    /// A chain of parents is as deep as it is long, and a loop or a chain past the limit is refused at the read, not
    /// walked by every node's path.
    #[test]
    fn deep_and_looping_parents_are_refused() {
        assert!(check_depth(&chain(MAX_DEPTH as i64)).is_ok());
        let e = check_depth(&chain(MAX_DEPTH as i64 + 1)).unwrap_err().to_string();
        assert!(e.contains("deeper than 1024"), "{e}");
        let mut looped = chain(3);
        looped.get_mut(&1).unwrap().father = 3;
        assert!(check_depth(&looped).is_err());
        // a father the scene does not hold ends the chain
        let mut orphan = chain(3);
        orphan.get_mut(&1).unwrap().father = 99;
        assert!(check_depth(&orphan).is_ok());
    }

    fn scene_of(nodes: BTreeMap<i64, Node>) -> Scene {
        Scene {
            file: "level0".into(),
            game_objects: BTreeMap::new(),
            transform_of: nodes.iter().map(|(&tp, n)| (n.game_object, tp)).collect(),
            nodes,
            world: std::sync::Mutex::new(BTreeMap::new()),
        }
    }

    /// A query limited to a GameObject without a Transform is an error for every query that takes a root, the LODGroup
    /// query among them, not an unlimited one.
    #[test]
    fn a_root_without_a_transform_is_refused() {
        let scene = scene_of(chain(2));
        assert_eq!(scene.root_transform(None).unwrap(), None);
        assert_eq!(scene.root_transform(Some(2)).unwrap(), Some(2));
        let e = scene.root_transform(Some(77)).unwrap_err().to_string();
        assert!(e.contains("GameObject 77 has no transform"), "{e}");
    }

    /// A panic while the world cache was locked leaves a usable cache, not a panic in every later call.
    #[test]
    fn a_poisoned_world_cache_is_still_read() {
        let scene = std::sync::Arc::new(scene_of(chain(3)));
        let held = scene.clone();
        let _ = std::thread::spawn(move || {
            let _guard = held.world.lock().unwrap();
            panic!("poison the cache");
        })
        .join();
        assert!(scene.world.is_poisoned());
        assert_eq!(scene.world_of(3).unwrap(), IDENTITY);
    }

    fn with(k: &str, v: Value) -> Value {
        Value::Struct(vec![(k.into(), v)])
    }

    /// Layers and culling masks outside 32 bits are refused, not wrapped to another layer set.
    #[test]
    fn layers_and_masks_are_not_cast() {
        assert_eq!(layer_of(&with("m_Layer", Value::Int(5))).unwrap(), 5);
        assert_eq!(layer_of(&Value::Struct(vec![])).unwrap(), 0);
        for bad in [-1, 1 << 32] {
            assert!(layer_of(&with("m_Layer", Value::Int(bad))).is_err());
        }
        let mask = |bits| culling_mask(&with("m_CullingMask", with("m_Bits", Value::Int(bits))), 9);
        assert_eq!(mask(0xffff_fff0).unwrap(), 0xffff_fff0);
        assert_eq!(mask(-1).unwrap(), u32::MAX);
        assert_eq!(culling_mask(&Value::Struct(vec![]), 9).unwrap(), u32::MAX);
        let e = mask(1 << 32).unwrap_err().to_string();
        assert!(e.contains("object 9") && e.contains("4294967296"), "{e}");
        assert!(mask(-(1 << 40)).is_err());
    }
}