openusd 0.4.0

//! Scene description foundations.
//!
//! This module contains common data types used by parsers.
//! Roughly this correspond to C++ SDF module <https://openusd.org/dev/api/sdf_page_front.html>

use std::{borrow::Cow, collections::HashMap, fmt::Debug};

use anyhow::{anyhow, Result};
use bytemuck::{Pod, Zeroable};
use strum::{Display, EnumCount, FromRepr};

mod change;
mod data;
mod layer;
mod ordering;
mod path;
pub mod schema;
mod spec;
mod value;

pub use change::{ChangeEntry, ChangeFlags, ChangeList};
pub use data::Data;
pub use layer::{AuthoringError, Layer, LayerFormat};
pub use ordering::apply_ordering;
pub use path::{path, Path};
pub use schema::{ChildrenKey, FieldKey};
pub use spec::{
    AttributeSpec, AttributeSpecMut, PrimSpec, PrimSpecMut, PseudoRootSpec, PseudoRootSpecMut, RelationshipSpec,
    RelationshipSpecMut, Spec, SpecError,
};
pub use value::{Value, ValueConversionError};

/// An enum that specifies the type of an object.
/// Objects are entities that have fields and are addressable by path.
#[repr(u32)]
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, FromRepr, EnumCount, Display)]
pub enum SpecType {
    // The unknown type has a value of 0 so that SdfSpecType() is unknown.
    #[default]
    Unknown = 0,

    // Real concrete types
    Attribute = 1,
    Connection = 2,
    Expression = 3,
    Mapper = 4,
    MapperArg = 5,
    Prim = 6,
    PseudoRoot = 7,
    Relationship = 8,
    RelationshipTarget = 9,
    Variant = 10,
    VariantSet = 11,
}

#[repr(i32)]
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, FromRepr)]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
#[cfg_attr(feature = "serde", serde(rename_all = "camelCase"))]
pub enum Specifier {
    Def,
    Over,
    Class,
}

/// An enum that defines permission levels.
///
/// Permissions control which layers may refer to or express
/// opinions about a prim. Opinions expressed about a prim, or
/// relationships to that prim, by layers that are not allowed
/// permission to access the prim will be ignored.
#[repr(i32)]
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, FromRepr)]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
#[cfg_attr(feature = "serde", serde(rename_all = "camelCase"))]
pub enum Permission {
    Public,
    Private,
}

/// An enum that identifies variability types for attributes.
/// Variability indicates whether the attribute may vary over time and
/// value coordinates, and if its value comes through authoring or
/// or from its owner.
#[repr(i32)]
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, FromRepr)]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
#[cfg_attr(feature = "serde", serde(rename_all = "camelCase"))]
pub enum Variability {
    #[default]
    Varying,
    Uniform,
}

/// Represents a time offset and scale between layers.
#[repr(C)]
#[derive(Debug, Clone, Copy, PartialEq, Pod, Zeroable)]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
pub struct LayerOffset {
    /// Time offset.
    pub offset: f64,
    /// Scale factor.
    pub scale: f64,
}

impl Default for LayerOffset {
    fn default() -> Self {
        Self {
            offset: 0.0,
            scale: 1.0,
        }
    }
}

impl LayerOffset {
    /// Identity layer offset: offset 0, scale 1.
    pub const IDENTITY: LayerOffset = LayerOffset {
        offset: 0.0,
        scale: 1.0,
    };

    #[inline]
    pub fn new(offset: f64, scale: f64) -> Self {
        Self { offset, scale }
    }

    #[inline]
    pub fn is_valid(&self) -> bool {
        self.offset.is_finite() && self.scale.is_finite()
    }

    /// Returns `true` if this is the identity offset `(0.0, 1.0)`.
    #[inline]
    pub fn is_identity(&self) -> bool {
        self.offset == 0.0 && self.scale == 1.0
    }

    /// Returns `true` if this offset is well-formed for composition:
    /// finite `offset` and a strictly positive, finite `scale`.
    ///
    /// Per spec 10.3.1.1 / 10.3.2.1.2, a non-positive scale is a composition
    /// error.
    #[inline]
    pub fn is_valid_composition(&self) -> bool {
        self.offset.is_finite() && self.scale.is_finite() && self.scale > 0.0
    }

    /// Returns this offset if valid for composition, or the identity otherwise.
    ///
    /// Matches OpenUSD behaviour of silently dropping back to identity when a
    /// non-positive or non-finite scale is authored.
    #[inline]
    pub fn sanitized(self) -> Self {
        if self.is_valid_composition() {
            self
        } else {
            Self::IDENTITY
        }
    }

    /// Concatenates `self` (outer / closer to root) with `inner` (deeper).
    ///
    /// Given two offsets where a time value `t` in the inner frame maps to
    /// the outer frame as `t * inner.scale + inner.offset`, and outer's own
    /// transform is `t * outer.scale + outer.offset`, the composed transform
    /// from the deepest frame to the outermost is:
    ///
    /// ```text
    /// offset = outer.offset + outer.scale * inner.offset
    /// scale  = outer.scale * inner.scale
    /// ```
    #[inline]
    pub fn concatenate(&self, inner: &LayerOffset) -> LayerOffset {
        LayerOffset {
            offset: self.offset + self.scale * inner.offset,
            scale: self.scale * inner.scale,
        }
    }
}

/// Represents a payload and all its meta data.
///
/// A payload represents a prim reference to an external layer. A payload
/// is similar to a prim reference (see SdfReference) with the major
/// difference that payloads are explicitly loaded by the user.
///
/// Unloaded payloads represent a boundary that lazy composition and
/// system behaviors will not traverse across, providing a user-visible
/// way to manage the working set of the scene.
#[derive(Debug, Default, Clone, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
pub struct Payload {
    /// The asset path to the external layer.
    #[cfg_attr(feature = "serde", serde(rename = "asset", skip_serializing_if = "String::is_empty"))]
    pub asset_path: String,
    /// The root prim path to the referenced prim in the external layer.
    #[cfg_attr(feature = "serde", serde(rename = "path", skip_serializing_if = "Path::is_empty"))]
    pub prim_path: Path,
    /// The layer offset to transform time.
    #[cfg_attr(
        feature = "serde",
        serde(rename = "layerOffset", skip_serializing_if = "Option::is_none")
    )]
    pub layer_offset: Option<LayerOffset>,
}

/// Represents a reference and all its meta data.
///
/// A reference is expressed on a prim in a given layer and it identifies a
/// prim in a layer stack. All opinions in the namespace hierarchy
/// under the referenced prim will be composed with the opinions in the
/// namespace hierarchy under the referencing prim.
#[derive(Debug, Default, Clone, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
pub struct Reference {
    /// The asset path to the external layer.
    #[cfg_attr(feature = "serde", serde(rename = "asset", skip_serializing_if = "String::is_empty"))]
    pub asset_path: String,
    /// The path to the referenced prim in the external layer.
    #[cfg_attr(feature = "serde", serde(rename = "path", skip_serializing_if = "Path::is_empty"))]
    pub prim_path: Path,
    /// The layer offset to transform time.
    #[cfg_attr(feature = "serde", serde(rename = "layerOffset"))]
    pub layer_offset: LayerOffset,
    /// The custom data associated with the reference.
    #[cfg_attr(
        feature = "serde",
        serde(rename = "customData", skip_serializing_if = "HashMap::is_empty")
    )]
    pub custom_data: HashMap<String, Value>,
}

mod list_op;

pub use list_op::ListOp;

pub type IntListOp = ListOp<i32>;
pub type UintListOp = ListOp<u32>;

pub type Int64ListOp = ListOp<i64>;
pub type Uint64ListOp = ListOp<u64>;

pub type StringListOp = ListOp<String>;
pub type TokenListOp = ListOp<String>;
pub type PathListOp = ListOp<Path>;
pub type ReferenceListOp = ListOp<Reference>;
pub type PayloadListOp = ListOp<Payload>;

pub type TimeSampleMap = Vec<(f64, Value)>;

/// Interface to access scene description data similar to `SdfAbstractData` in C++ version of USD.
///
/// `AbstractData` is an anonymous container that owns scene description values.
///
/// For now holds read-only portion of the API.
pub trait AbstractData {
    /// Returns `true` if this data has a spec for the given path.
    fn has_spec(&self, path: &Path) -> bool;

    /// Returns `true` if this data has a field for the given path.
    fn has_field(&self, path: &Path, field: &str) -> bool;

    /// Returns the type of the spec at the given path.
    fn spec_type(&self, path: &Path) -> Option<SpecType>;

    /// Returns the value for a field, or `None` if not authored.
    ///
    /// The value can be either owned or borrowed depending on internals.
    /// In the binary format, the data is typically compressed and/or encoded,
    /// so memory allocation is required to store unpacked result, so owned
    /// values are typically expected. With text parsers, there is a data copy
    /// already stored, so a borrowed value is returned to avoid unnecessary copies.
    ///
    /// Errors propagate I/O or decoding failures; a missing spec or field is
    /// signalled by `Ok(None)`.
    fn try_get(&self, path: &Path, field: &str) -> Result<Option<Cow<'_, Value>>>;

    /// Returns the value for a field, erroring if not authored.
    ///
    /// Use [`AbstractData::try_get`] when absence is an expected condition.
    fn get(&self, path: &Path, field: &str) -> Result<Cow<'_, Value>> {
        self.try_get(path, field)?
            .ok_or_else(|| anyhow!("No field '{field}' at path '{path}'"))
    }

    /// Returns the field names for a given path in authored order.
    fn list(&self, path: &Path) -> Option<Vec<String>>;

    /// Returns every authored path, sorted lexicographically.
    ///
    /// The order is deterministic and stable across repeated calls. Emitters
    /// rely on this for reproducible output.
    fn paths(&self) -> Vec<Path>;

    /// Returns a reference to the underlying [`Data`] backend, if this impl
    /// is a writable in-memory store. Read-only file-backed impls return
    /// `None`. The default implementation returns `None`, so adding a new
    /// `AbstractData` impl does not require opting in.
    fn as_data(&self) -> Option<&Data> {
        None
    }

    /// Returns a mutable reference to the underlying [`Data`] backend, if this
    /// impl is a writable in-memory store.
    ///
    /// Read-only backends (USDA text readers, USDC binary readers) return
    /// `None`. The default implementation returns `None`, so adding a new
    /// `AbstractData` impl does not require opting in. Authoring code that
    /// needs to mutate a layer uses this hook to reach the writable store.
    fn as_data_mut(&mut self) -> Option<&mut Data> {
        None
    }
}

/// A boxed layer data source, used throughout the layer stack.
pub type LayerData = Box<dyn AbstractData>;

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

    #[test]
    fn layer_offset_identity_is_identity() {
        assert!(LayerOffset::IDENTITY.is_identity());
        assert!(LayerOffset::default().is_identity());
        assert!(!LayerOffset::new(0.0, 2.0).is_identity());
        assert!(!LayerOffset::new(1.0, 1.0).is_identity());
    }

    #[test]
    fn layer_offset_valid_composition_rejects_non_positive_scale() {
        assert!(LayerOffset::new(10.0, 1.0).is_valid_composition());
        assert!(!LayerOffset::new(10.0, 0.0).is_valid_composition());
        assert!(!LayerOffset::new(10.0, -1.0).is_valid_composition());
        assert!(!LayerOffset::new(f64::INFINITY, 1.0).is_valid_composition());
        assert!(!LayerOffset::new(0.0, f64::NAN).is_valid_composition());
    }

    #[test]
    fn layer_offset_sanitized_drops_invalid_to_identity() {
        assert_eq!(LayerOffset::new(10.0, 2.0).sanitized(), LayerOffset::new(10.0, 2.0));
        assert_eq!(LayerOffset::new(5.0, -1.0).sanitized(), LayerOffset::IDENTITY);
        assert_eq!(LayerOffset::new(5.0, 0.0).sanitized(), LayerOffset::IDENTITY);
    }

    #[test]
    fn layer_offset_concatenate_matches_spec_formula() {
        let outer = LayerOffset::new(10.0, 2.0);
        let inner = LayerOffset::new(20.0, 1.0);
        // Matches BasicTimeOffset_root pcp.txt: (10,2) concat (20,1) = (50, 2).
        assert_eq!(outer.concatenate(&inner), LayerOffset::new(50.0, 2.0));
    }

    #[test]
    fn layer_offset_concatenate_is_associative() {
        let a = LayerOffset::new(10.0, 2.0);
        let b = LayerOffset::new(20.0, 0.5);
        let c = LayerOffset::new(5.0, 3.0);
        let ab_c = a.concatenate(&b).concatenate(&c);
        let a_bc = a.concatenate(&b.concatenate(&c));
        assert!((ab_c.offset - a_bc.offset).abs() < 1e-12);
        assert!((ab_c.scale - a_bc.scale).abs() < 1e-12);
    }

    #[test]
    fn layer_offset_identity_is_neutral() {
        let a = LayerOffset::new(10.0, 2.0);
        assert_eq!(a.concatenate(&LayerOffset::IDENTITY), a);
        assert_eq!(LayerOffset::IDENTITY.concatenate(&a), a);
    }
}