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use std::fmt::{self, Debug, Formatter};
use std::hash::Hash;
use std::num::NonZeroUsize;
use super::{Content, Selector};
use crate::diag::StrResult;
use crate::doc::{Frame, FrameItem, Meta, Position};
use crate::eval::cast_from_value;
use crate::geom::{Point, Transform};
use crate::model::Label;
use crate::util::NonZeroExt;
/// Stably identifies an element in the document across multiple layout passes.
///
/// This struct is created by [`StabilityProvider::locate`].
#[derive(Copy, Clone, Eq, PartialEq, Hash)]
pub struct Location {
/// The hash of the element.
hash: u128,
/// An unique number among elements with the same hash. This is the reason
/// we need a mutable `StabilityProvider` everywhere.
disambiguator: usize,
/// A synthetic location created from another one. This is used for example
/// in bibliography management to create individual linkable locations for
/// reference entries from the bibliography's location.
variant: usize,
}
impl Location {
/// Produce a variant of this location.
pub fn variant(mut self, n: usize) -> Self {
self.variant = n;
self
}
}
impl Debug for Location {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
f.pad("..")
}
}
cast_from_value! {
Location: "location",
}
/// Provides stable identities to elements.
#[derive(Clone, Default)]
pub struct StabilityProvider {
hashes: Vec<u128>,
checkpoints: Vec<usize>,
}
impl StabilityProvider {
/// Create a new stability provider.
pub fn new() -> Self {
Self::default()
}
}
#[comemo::track]
impl StabilityProvider {
/// Produce a stable identifier for this call site.
pub fn locate(&mut self, hash: u128) -> Location {
let disambiguator = self.hashes.iter().filter(|&&prev| prev == hash).count();
self.hashes.push(hash);
Location { hash, disambiguator, variant: 0 }
}
/// Create a checkpoint of the state that can be restored.
pub fn save(&mut self) {
self.checkpoints.push(self.hashes.len());
}
/// Restore the last checkpoint.
pub fn restore(&mut self) {
if let Some(checkpoint) = self.checkpoints.pop() {
self.hashes.truncate(checkpoint);
}
}
}
/// Can be queried for elements and their positions.
pub struct Introspector {
pages: usize,
elems: Vec<(Content, Position)>,
}
impl Introspector {
/// Create a new introspector.
pub fn new(frames: &[Frame]) -> Self {
let mut introspector = Self { pages: frames.len(), elems: vec![] };
for (i, frame) in frames.iter().enumerate() {
let page = NonZeroUsize::new(1 + i).unwrap();
introspector.extract(frame, page, Transform::identity());
}
introspector
}
/// Iterate over all elements.
pub fn all(&self) -> impl Iterator<Item = &Content> {
self.elems.iter().map(|(elem, _)| elem)
}
/// Extract metadata from a frame.
fn extract(&mut self, frame: &Frame, page: NonZeroUsize, ts: Transform) {
for (pos, item) in frame.items() {
match item {
FrameItem::Group(group) => {
let ts = ts
.pre_concat(Transform::translate(pos.x, pos.y))
.pre_concat(group.transform);
self.extract(&group.frame, page, ts);
}
FrameItem::Meta(Meta::Elem(content), _)
if !self
.elems
.iter()
.any(|(prev, _)| prev.location() == content.location()) =>
{
let pos = pos.transform(ts);
self.elems.push((content.clone(), Position { page, point: pos }));
}
_ => {}
}
}
}
}
#[comemo::track]
impl Introspector {
/// Whether this introspector is not yet initialized.
pub fn init(&self) -> bool {
self.pages > 0
}
/// Query for all matching elements.
pub fn query(&self, selector: Selector) -> Vec<Content> {
self.all().filter(|elem| selector.matches(elem)).cloned().collect()
}
/// Query for all matching element up to the given location.
pub fn query_before(&self, selector: Selector, location: Location) -> Vec<Content> {
let mut matches = vec![];
for elem in self.all() {
if selector.matches(elem) {
matches.push(elem.clone());
}
if elem.location() == Some(location) {
break;
}
}
matches
}
/// Query for all matching elements starting from the given location.
pub fn query_after(&self, selector: Selector, location: Location) -> Vec<Content> {
self.all()
.skip_while(|elem| elem.location() != Some(location))
.filter(|elem| selector.matches(elem))
.cloned()
.collect()
}
/// Query for a unique element with the label.
pub fn query_label(&self, label: &Label) -> StrResult<Content> {
let mut found = None;
for elem in self.all().filter(|elem| elem.label() == Some(label)) {
if found.is_some() {
return Err("label occurs multiple times in the document".into());
}
found = Some(elem.clone());
}
found.ok_or_else(|| "label does not exist in the document".into())
}
/// The total number pages.
pub fn pages(&self) -> NonZeroUsize {
NonZeroUsize::new(self.pages).unwrap_or(NonZeroUsize::ONE)
}
/// Find the page number for the given location.
pub fn page(&self, location: Location) -> NonZeroUsize {
self.position(location).page
}
/// Find the position for the given location.
pub fn position(&self, location: Location) -> Position {
self.elems
.iter()
.find(|(elem, _)| elem.location() == Some(location))
.map(|(_, loc)| *loc)
.unwrap_or(Position { page: NonZeroUsize::ONE, point: Point::zero() })
}
}
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