molframe-core 0.2.1

//! The normalised structure: what a file means, rather than how it was written.
//!
//! A structure is immutable and shared by reference. Editing produces a new one
//! rather than changing this one in place, which is what makes handing out a
//! pointer to the coordinates safe: a buffer given to a caller belongs to a
//! snapshot that can never change underneath it, and every derived index stays
//! valid for as long as the snapshot it was built against.
//!
//! Formatting is not preserved here. Reproducing whitespace, column widths and
//! quoting is the document's job; this layer preserves meaning.

use super::ExtensionStore;
use crate::annotation::AtomAnnotations;
use crate::chunk::AtomChunk;
use crate::coords::{CoordinateBlock, CoordinateGeneration};
use crate::index::ModelIndex;
use crate::symbol::{Interner, SymbolId};
use crate::topology::Topology;
use std::fmt;
use std::sync::Arc;

const PLACEHOLDER_TOLERANCE: f64 = 1e-6;

/// What the entry as a whole says about itself.
///
/// The identifier is a variable-length string. Four characters was a property of
/// one file format, not of the archive, and extended identifiers are already
/// being issued.
#[derive(Clone, Debug, Default)]
pub struct EntryMetadata {
    /// The entry identifier, as deposited.
    pub id: Option<Box<str>>,
    /// The entry title.
    pub title: Option<Box<str>>,
    /// The experimental method.
    pub method: Option<Box<str>>,
    /// Resolution in ångström, where the method reports one.
    pub resolution: Option<f32>,
}

/// The crystallographic cell.
#[derive(Clone, Copy, PartialEq, Debug)]
pub struct UnitCell {
    /// Cell edge lengths in ångström.
    pub lengths: [f64; 3],
    /// Cell angles in degrees.
    pub angles: [f64; 3],
}

impl UnitCell {
    /// Returns true when the cell is the placeholder some files write when they
    /// have no cell at all.
    ///
    /// A unit cube with right angles is what a structure determined without
    /// crystallography carries, and treating it as a real cell would produce
    /// periodic images of a molecule that was never in a crystal.
    #[must_use]
    pub fn is_placeholder(&self) -> bool {
        values_are_near(&self.lengths, 1.0) && values_are_near(&self.angles, 90.0)
    }
}

/// Where the positions of each model live.
#[derive(Clone, Debug)]
pub enum CoordinateStore {
    /// One model.
    Single(CoordinateBlock),
    /// Several models over identical topology, so only positions differ.
    ///
    /// This covers ensembles and trajectory frames, where annotations are shared
    /// and repeating them per frame would multiply the memory by the frame count.
    Dense {
        /// One block per model, each with the same atom count.
        frames: Vec<CoordinateBlock>,
    },
    /// Models whose atom content genuinely differs.
    ///
    /// Padding these into one rectangular block would fabricate atoms that were
    /// never modelled and destroy the difference between absent and unrecorded,
    /// so they are held as separate structures instead.
    Ragged {
        /// One structure per model.
        models: Vec<Structure>,
    },
}

impl CoordinateStore {
    pub(crate) fn make_unique_in(
        &mut self,
        context: &crate::ExecutionContext,
    ) -> Result<(), crate::MemoryBudgetError> {
        match self {
            Self::Single(block) => block.make_unique_in(context),
            Self::Dense { frames } => {
                for frame in frames {
                    frame.make_unique_in(context)?;
                }
                Ok(())
            }
            Self::Ragged { .. } => Ok(()),
        }
    }

    /// The number of models.
    #[must_use]
    pub fn model_count(&self) -> usize {
        match self {
            Self::Single(_) => 1,
            Self::Dense { frames } => frames.len(),
            Self::Ragged { models } => models.len(),
        }
    }

    /// The positions of one model, where they are held directly.
    ///
    /// A ragged ensemble answers `None`: its models are structures in their own
    /// right and are reached through [`CoordinateStore::Ragged`].
    #[must_use]
    pub fn block(&self, model: ModelIndex) -> Option<&CoordinateBlock> {
        match self {
            Self::Single(block) => (model.get() == 0).then_some(block),
            Self::Dense { frames } => frames.get(model.as_usize()),
            // A ragged ensemble's models are structures in their own right, and
            // a single-model store has no second model to offer.
            Self::Ragged { .. } => None,
        }
    }

    /// Returns true when every model shares one topology.
    #[must_use]
    pub const fn is_dense(&self) -> bool {
        matches!(self, Self::Single(_) | Self::Dense { .. })
    }

    /// The independent structures of a ragged ensemble.
    #[must_use]
    pub fn ragged_models(&self) -> Option<&[Structure]> {
        match self {
            Self::Ragged { models } => Some(models),
            Self::Single(_) | Self::Dense { .. } => None,
        }
    }
}

/// Everything a structure holds.
#[derive(Clone, Debug)]
pub struct StructureData {
    /// What the entry says about itself.
    pub entry: EntryMetadata,
    /// The hierarchy.
    pub topology: Topology,
    /// The atoms, in chunks.
    pub chunks: Arc<Vec<AtomChunk>>,
    /// Chemical connectivity as compact edge columns.
    pub bonds: crate::bond::BondTable,
    /// Structure-local typed columns aligned exactly to atom rows.
    pub annotations: AtomAnnotations,
    /// Cold, typed domain metadata attached to this snapshot.
    pub extensions: ExtensionStore,
    /// The positions.
    pub coords: CoordinateStore,
    /// The identifiers this structure interned.
    pub dictionary: Interner,
    /// The crystallographic cell, where the file carried one.
    pub cell: Option<UnitCell>,
    /// How many times the positions have changed.
    pub generation: CoordinateGeneration,
    pub(crate) reservation: Option<Arc<crate::MemoryReservation>>,
}

/// An immutable structure, shared by reference.
///
/// Cloning one is a reference count, not a copy, so passing a structure to
/// another thread or holding several versions at once is cheap.
///
/// # Examples
///
/// ```
/// use molframe_core::structure::{Structure, StructureData};
///
/// let structure = Structure::new(StructureData::empty());
/// assert_eq!(structure.atom_count(), 0);
/// assert_eq!(structure.model_count(), 1);
/// ```
#[repr(C)]
#[derive(Clone, Debug)]
pub struct Structure(Arc<StructureData>);

impl StructureData {
    /// A structure with nothing in it.
    #[must_use]
    pub fn empty() -> Self {
        Self {
            reservation: None,
            entry: EntryMetadata::default(),
            topology: Topology::default(),
            chunks: Arc::new(Vec::new()),
            bonds: crate::bond::BondTable::default(),
            annotations: AtomAnnotations::default(),
            extensions: ExtensionStore::new(),
            coords: CoordinateStore::Single(CoordinateBlock::new()),
            dictionary: Interner::new(),
            cell: None,
            generation: CoordinateGeneration::INITIAL,
        }
    }

    pub(crate) fn atom_count(&self) -> u32 {
        match self.chunks.last() {
            Some(chunk) => chunk.atoms().end,
            None => 0,
        }
    }
}

impl Structure {
    /// Wraps structure data for sharing.
    #[must_use]
    pub fn new(data: StructureData) -> Self {
        Self(Arc::new(data))
    }

    pub(crate) fn retain_reservation(mut self, reservation: Arc<crate::MemoryReservation>) -> Self {
        let data = Arc::make_mut(&mut self.0);
        if let CoordinateStore::Ragged { models } = &mut data.coords {
            for model in models {
                *model = model.clone().retain_reservation(Arc::clone(&reservation));
            }
        }
        data.reservation = Some(reservation);
        self
    }

    /// The data behind the reference.
    #[must_use]
    pub fn data(&self) -> &StructureData {
        &self.0
    }

    /// The shared handle, for a view that must outlive this reference.
    #[must_use]
    pub fn shared(&self) -> Arc<StructureData> {
        Arc::clone(&self.0)
    }

    /// The number of atoms in one model.
    #[must_use]
    pub fn atom_count(&self) -> u32 {
        self.0.atom_count()
    }

    /// A lightweight handle on one atom.
    #[must_use]
    pub fn atom(&self, atom: crate::index::AtomIndex) -> Option<super::AtomRef<'_>> {
        self.0.atom(atom)
    }

    /// A lightweight handle on one model.
    #[must_use]
    pub fn model(&self, model: ModelIndex) -> Option<super::ModelRef<'_>> {
        self.0.model(model)
    }

    /// The structure and local model position that represent one model.
    ///
    /// Dense models share this structure and retain their position. Ragged
    /// models are independent single-model structures, so their local position
    /// is zero. This keeps callers from padding unlike topologies.
    #[must_use]
    pub fn model_snapshot(&self, model: ModelIndex) -> Option<(Self, ModelIndex)> {
        match &self.0.coords {
            CoordinateStore::Ragged { models } => models
                .get(model.as_usize())
                .cloned()
                .map(|structure| (structure, ModelIndex::new(0))),
            CoordinateStore::Single(_) | CoordinateStore::Dense { .. } => self
                .model(model)
                .map(|_| (self.clone(), model))
                .or_else(|| {
                    (model.get() == 0 && self.model_count() == 1).then(|| (self.clone(), model))
                }),
        }
    }

    /// A lightweight handle on one chain.
    #[must_use]
    pub fn chain(&self, chain: crate::index::ChainIndex) -> Option<super::ChainRef<'_>> {
        self.0.chain(chain)
    }

    /// A lightweight handle on one residue.
    #[must_use]
    pub fn residue(&self, residue: crate::index::ResidueIndex) -> Option<super::ResidueRef<'_>> {
        self.0.residue(residue)
    }

    /// The number of models.
    #[must_use]
    pub fn model_count(&self) -> usize {
        self.0.coords.model_count()
    }

    /// The independent model structures when topology differs between models.
    #[must_use]
    pub fn ragged_models(&self) -> Option<&[Self]> {
        self.0.coords.ragged_models()
    }

    /// The number of chains.
    #[must_use]
    pub fn chain_count(&self) -> usize {
        self.0.topology.chains.len()
    }

    /// The number of residues.
    #[must_use]
    pub fn residue_count(&self) -> usize {
        self.0.topology.residues.len()
    }

    /// The number of distinct chemical species.
    #[must_use]
    pub fn entity_count(&self) -> usize {
        self.0.topology.entities.len()
    }

    /// The positions of the first model, contiguously.
    ///
    /// This slice is the buffer itself, not a copy of it, which is what makes
    /// handing coordinates to a numeric array free.
    #[must_use]
    pub fn positions(&self) -> &[[f32; 3]] {
        match self.model_positions(ModelIndex::new(0)) {
            Some(positions) => positions,
            None => &[],
        }
    }

    /// The positions of one model.
    #[must_use]
    pub fn model_positions(&self, model: ModelIndex) -> Option<&[[f32; 3]]> {
        self.0.coords.block(model).map(CoordinateBlock::as_slice)
    }

    /// How many times the positions have changed.
    #[must_use]
    pub fn generation(&self) -> CoordinateGeneration {
        self.0.generation
    }

    /// Structure-local typed columns aligned to atom rows.
    #[must_use]
    pub fn annotations(&self) -> &AtomAnnotations {
        &self.0.annotations
    }

    /// Cold, typed domain metadata attached to this snapshot.
    #[must_use]
    pub fn extensions(&self) -> &ExtensionStore {
        &self.0.extensions
    }

    /// Returns a new snapshot with one typed domain extension attached.
    #[must_use]
    pub fn with_extension<T>(&self, key: &'static str, value: T) -> Self
    where
        T: std::any::Any + Send + Sync + std::panic::RefUnwindSafe,
    {
        let mut data = self.data().clone();
        data.extensions.insert(key, value);
        Self::new(data)
    }

    /// Returns a new snapshot without domain extensions.
    #[must_use]
    pub fn without_extensions(&self) -> Self {
        if self.0.extensions.is_empty() {
            return self.clone();
        }
        let mut data = self.data().clone();
        data.extensions.clear();
        Self::new(data)
    }

    /// The string an interned identifier names.
    #[must_use]
    pub fn resolve(&self, symbol: SymbolId) -> Option<&str> {
        self.0.dictionary.resolve(symbol)
    }
}

impl From<StructureData> for Structure {
    fn from(data: StructureData) -> Self {
        Self::new(data)
    }
}

fn values_are_near(values: &[f64], expected: f64) -> bool {
    values
        .iter()
        .all(|value| (value - expected).abs() < PLACEHOLDER_TOLERANCE)
}

impl fmt::Display for Structure {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(
            f,
            "Structure(models={}, chains={}, residues={}, atoms={})",
            self.model_count(),
            self.chain_count(),
            self.residue_count(),
            self.atom_count(),
        )
    }
}

#[cfg(test)]
#[path = "data_tests.rs"]
mod tests;