oxgraph-property 0.4.1

//! Property index width contracts, per-axis markers, and metadata-word codecs.
//!
//! Defines the sealed [`PropertyIndex`] / [`PropertySnapshotMetaWord`] width
//! traits, the three built-in [`PropertyAxis`] markers and their [`AxisIndex`]
//! topology-bound dispatch, the snapshot section-kind constants keyed by
//! metadata width, and the little-endian metadata-word conversion helpers.

use std::vec::Vec;

use arrow_array::{PrimitiveArray, types::ArrowPrimitiveType};
use oxgraph_layout_util::SnapshotWidth;
use oxgraph_topology::{DenseElementIndex, DenseIncidenceIndex, DenseRelationIndex, TopologyBase};

use crate::model::{IdFamily, PropertyError};

/// 4-aligned base section kind for property-layer descriptors; the persisted
/// kind is `BASE | WIDTH_CODE` for the metadata width.
///
/// The six property-band bases ascend by at least 4 in the canonical export
/// order (descriptors, data, identity modes, element/relation/incidence
/// identity maps), so every derived kind of one role sorts below every derived
/// kind of the next role for any metadata/map width mix — the
/// strictly-ascending order the container mandates.
///
/// # Performance
///
/// `perf: unspecified`; this is a compile-time constant.
pub const SNAPSHOT_KIND_PROPERTY_DESCRIPTORS_BASE: u32 = 0x0100;

/// 4-aligned base section kind for Arrow IPC property-layer payloads.
///
/// # Performance
///
/// `perf: unspecified`; this is a compile-time constant.
pub const SNAPSHOT_KIND_PROPERTY_DATA_BASE: u32 = 0x0104;

/// 4-aligned base section kind for identity-mode metadata records.
///
/// # Performance
///
/// `perf: unspecified`; this is a compile-time constant.
pub const SNAPSHOT_KIND_IDENTITY_MODES_BASE: u32 = 0x0110;

/// 4-aligned base section kind for element local-to-canonical maps.
///
/// # Performance
///
/// `perf: unspecified`; this is a compile-time constant.
pub const SNAPSHOT_KIND_ELEMENT_IDENTITY_MAP_BASE: u32 = 0x0114;

/// 4-aligned base section kind for relation local-to-canonical maps.
///
/// # Performance
///
/// `perf: unspecified`; this is a compile-time constant.
pub const SNAPSHOT_KIND_RELATION_IDENTITY_MAP_BASE: u32 = 0x0118;

/// 4-aligned base section kind for incidence local-to-canonical maps.
///
/// # Performance
///
/// `perf: unspecified`; this is a compile-time constant.
pub const SNAPSHOT_KIND_INCIDENCE_IDENTITY_MAP_BASE: u32 = 0x011C;

/// Internal property/identity snapshot section version.
///
/// # Performance
///
/// `perf: unspecified`; this is a compile-time constant.
pub const SNAPSHOT_PROPERTY_VERSION: u32 = 1;

/// Sealed trait modules for property width contracts.
mod sealed {
    /// Seals [`super::PropertyIndex`] to supported unsigned sparse widths.
    pub trait PropertyIndex {}

    /// Seals [`super::PropertySnapshotMetaWord`] to supported metadata widths.
    pub trait PropertySnapshotMetaWord {}

    /// Seals [`super::PropertyAxis`] to the three built-in axis markers.
    pub trait PropertyAxis {}
}

/// Unsigned index width usable for sparse property indexes.
///
/// This is the thin Arrow-specific layer over the shared
/// [`SnapshotWidth`](oxgraph_layout_util::SnapshotWidth) contract: the
/// `usize`/little-endian-word conversions and [`SnapshotWidth::WIDTH_CODE`]
/// resolve through that trait, so `I::LittleEndianWord` and `I::to_le_word`
/// have one definition substrate-wide. This trait only adds the Arrow
/// primitive-array vocabulary plus the `Into<u64>` diagnostic widening.
///
/// # Performance
///
/// Implementations perform conversions in `O(1)` and array construction in
/// `O(values.len())`.
pub trait PropertyIndex: sealed::PropertyIndex + SnapshotWidth + Into<u64> {
    /// Arrow unsigned primitive type for sparse index arrays.
    type ArrowType: ArrowPrimitiveType<Native = Self> + 'static;

    /// Builds an Arrow primitive array from native index values.
    ///
    /// # Performance
    ///
    /// This function is `O(values.len())`.
    fn primitive_array(values: Vec<Self>) -> PrimitiveArray<Self::ArrowType>;
}

/// Metadata/canonical-ID word width for property and identity snapshot sections.
///
/// Derives each width-specific section kind from the crate's 4-aligned base
/// constants or-ed with [`SnapshotWidth::WIDTH_CODE`] (inherited through
/// [`PropertyIndex`]), so the two-bit width encoding has one source of truth.
///
/// # Performance
///
/// Reading the kind constants is `O(1)`.
pub trait PropertySnapshotMetaWord: sealed::PropertySnapshotMetaWord + PropertyIndex {
    /// Property descriptor section kind for this metadata width.
    const PROPERTY_DESCRIPTORS_KIND: u32 =
        SNAPSHOT_KIND_PROPERTY_DESCRIPTORS_BASE | Self::WIDTH_CODE;

    /// Property data section kind for this metadata width.
    const PROPERTY_DATA_KIND: u32 = SNAPSHOT_KIND_PROPERTY_DATA_BASE | Self::WIDTH_CODE;

    /// Identity mode section kind for this metadata width.
    const IDENTITY_MODES_KIND: u32 = SNAPSHOT_KIND_IDENTITY_MODES_BASE | Self::WIDTH_CODE;

    /// Element identity map section kind for this metadata width.
    const ELEMENT_IDENTITY_MAP_KIND: u32 =
        SNAPSHOT_KIND_ELEMENT_IDENTITY_MAP_BASE | Self::WIDTH_CODE;

    /// Relation identity map section kind for this metadata width.
    const RELATION_IDENTITY_MAP_KIND: u32 =
        SNAPSHOT_KIND_RELATION_IDENTITY_MAP_BASE | Self::WIDTH_CODE;

    /// Incidence identity map section kind for this metadata width.
    const INCIDENCE_IDENTITY_MAP_KIND: u32 =
        SNAPSHOT_KIND_INCIDENCE_IDENTITY_MAP_BASE | Self::WIDTH_CODE;
}

/// Implements property width traits for one unsigned integer.
macro_rules! impl_property_width {
    ($index:ty, $arrow:ty) => {
        impl sealed::PropertyIndex for $index {}

        impl PropertyIndex for $index {
            type ArrowType = $arrow;

            fn primitive_array(values: Vec<Self>) -> PrimitiveArray<Self::ArrowType> {
                PrimitiveArray::<$arrow>::from(values)
            }
        }

        impl sealed::PropertySnapshotMetaWord for $index {}

        impl PropertySnapshotMetaWord for $index {}
    };
}

impl_property_width!(u16, arrow_array::types::UInt16Type);

impl_property_width!(u32, arrow_array::types::UInt32Type);

impl_property_width!(u64, arrow_array::types::UInt64Type);

/// Marker trait selecting which axis of a topology view a property layer
/// keys against (elements, relations, or incidences).
///
/// Built-in axis markers — [`ElementAxis`], [`RelationAxis`], [`IncidenceAxis`]
/// — opt into the corresponding [`*Index`] topology trait when paired with
/// [`DenseWeights`] or [`SparseWeights`] storage. The trait itself only
/// reports the layer's [`IdFamily`]; per-axis topology accessors live in
/// inherent impls on each storage type for each axis marker.
///
/// # Performance
///
/// `perf: unspecified`; this is a metadata trait.
pub trait PropertyAxis: sealed::PropertyAxis {
    /// Returns the [`IdFamily`] this axis selects from a property layer.
    ///
    /// # Performance
    ///
    /// This function is `O(1)`.
    fn id_family() -> IdFamily;
}

/// Element-keyed axis marker.
///
/// # Performance
///
/// Copying and debug-formatting are `O(1)`.
#[derive(Clone, Copy, Debug, Default)]
pub struct ElementAxis;

impl sealed::PropertyAxis for ElementAxis {}
impl PropertyAxis for ElementAxis {
    fn id_family() -> IdFamily {
        IdFamily::Element
    }
}

/// Relation-keyed axis marker.
///
/// # Performance
///
/// Copying and debug-formatting are `O(1)`.
#[derive(Clone, Copy, Debug, Default)]
pub struct RelationAxis;

impl sealed::PropertyAxis for RelationAxis {}
impl PropertyAxis for RelationAxis {
    fn id_family() -> IdFamily {
        IdFamily::Relation
    }
}

/// Incidence-keyed axis marker.
///
/// # Performance
///
/// Copying and debug-formatting are `O(1)`.
#[derive(Clone, Copy, Debug, Default)]
pub struct IncidenceAxis;

impl sealed::PropertyAxis for IncidenceAxis {}
impl PropertyAxis for IncidenceAxis {
    fn id_family() -> IdFamily {
        IdFamily::Incidence
    }
}

/// Axis-aware topology bound accessor.
///
/// Implemented for every topology view that exposes the per-axis index trait
/// `DenseElementIndex` / `DenseRelationIndex` / `DenseIncidenceIndex`. Exists so that
/// generic constructors on [`DenseWeights`] and [`SparseWeights`] can dispatch
/// to the right `element_bound` / `relation_bound` / `incidence_bound` accessor
/// from a single body, without parallel per-axis impl blocks.
///
/// External code does not normally implement this trait; it is `pub` only
/// because it appears as a bound in `pub` constructor signatures.
///
/// # Performance
///
/// `axis_bound` is `O(1)` — it forwards to the topology's own
/// `*_bound` accessor.
pub trait AxisIndex<A: PropertyAxis>: TopologyBase {
    /// Returns the dense index bound for axis `A` on this topology view.
    ///
    /// # Performance
    ///
    /// `O(1)`.
    fn axis_bound(&self) -> usize;
}

impl<T> AxisIndex<ElementAxis> for T
where
    T: DenseElementIndex,
{
    fn axis_bound(&self) -> usize {
        self.element_bound()
    }
}

impl<T> AxisIndex<RelationAxis> for T
where
    T: DenseRelationIndex,
{
    fn axis_bound(&self) -> usize {
        self.relation_bound()
    }
}

impl<T> AxisIndex<IncidenceAxis> for T
where
    T: DenseIncidenceIndex,
{
    fn axis_bound(&self) -> usize {
        self.incidence_bound()
    }
}

/// Converts `value` into a little-endian metadata word.
///
/// # Performance
///
/// This function is `O(1)`.
pub(crate) fn le_word<W>(value: usize) -> Result<W::LittleEndianWord, PropertyError>
where
    W: PropertySnapshotMetaWord,
{
    let Some(value) = W::from_usize(value) else {
        return Err(PropertyError::SnapshotDescriptorMismatch {
            reason: "value does not fit selected metadata width",
        });
    };
    Ok(value.to_le_word())
}

/// Decodes a little-endian metadata word as `usize`.
///
/// # Performance
///
/// This function is `O(1)`.
pub(crate) fn le_word_to_usize<W>(word: W::LittleEndianWord) -> Result<usize, PropertyError>
where
    W: PropertySnapshotMetaWord,
{
    W::from_le_word(word)
        .to_usize()
        .ok_or(PropertyError::SnapshotDescriptorMismatch {
            reason: "metadata word does not fit usize",
        })
}

/// Decodes a little-endian metadata word as `u64`.
///
/// # Performance
///
/// This function is `O(1)`.
pub(crate) fn le_word_to_u64<W>(word: W::LittleEndianWord) -> u64
where
    W: PropertySnapshotMetaWord,
{
    W::from_le_word(word).into()
}

/// Decodes a little-endian metadata word as `u32`.
///
/// # Performance
///
/// This function is `O(1)`.
pub(crate) fn le_word_to_u32<W>(word: W::LittleEndianWord) -> Result<u32, PropertyError>
where
    W: PropertySnapshotMetaWord,
{
    let value = le_word_to_u64::<W>(word);
    u32::try_from(value).map_err(|_error| PropertyError::SnapshotDescriptorMismatch {
        reason: "metadata word does not fit u32 tag",
    })
}