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//! Filter bibliographies by structural selection.
/// Construct a [`Selector`].
///
/// Selectors can be used to filter bibliographies or to differentiate between
/// [`entries`](Entry) during processing. An [introduction to selectors][intro]
/// is available in the Git repository. This macro accepts expressions very
/// similar to the user-facing macros as parsed by [`Selector::parse`].
///
/// There are three main differences:
/// - Binding names and attributes have to be strings and thus wrapped in double
/// quotes
/// - Type names are case sensitive and have to start with a capital letter
/// since they are just variants of [`EntryType`][EType]
/// - Any non-atomic selector (`*` or an [`EntryType`][EType] variant are
/// atomic) in other constructions like ancestrage selectors or bindings must
/// be in parentheses since they have to parse as a single token tree for
/// correct expansion. If you get an error message along the lines of having
/// too much recursion, you likely forgot some parentheses.
///
/// This example illustrates some of the differences:
///
/// ```rust
/// use hayagriva::select;
/// use hayagriva::Selector;
///
/// // finds an article that is parented by a conference proceedings volume
/// assert_eq!(Selector::parse("article > proceedings").unwrap(), select!(Article > Proceedings));
///
/// // matches either a video or audio item or an artwork
/// assert_eq!(Selector::parse("video | audio | artwork").unwrap(), select!(Video | Audio | Artwork));
///
/// // matches anything that is parented by both a blog and a newspaper
/// assert_eq!(Selector::parse("* > (blog | newspaper)").unwrap(), select!(* > (Blog | Newspaper)));
///
/// // matches anything with a URL or a parent with a URL and binds the entry with the attribute to the variable `i`.
/// // Note that expressions like i:*[url] do not need parentheses in the parsed selector, but they do in the macro!
/// assert_eq!(Selector::parse("i:*[url] | (* > i:*[url])").unwrap(), select!(("i":(*["url"])) | (* > ("i":(*["url"])))));
/// ```
///
/// [intro]: https://github.com/typst/hayagriva/blob/main/docs/selectors.md
/// [CitStyle]: crate::style::CitationStyle
/// [BibStyle]: crate::style::BibliographyStyle
/// [EType]: crate::types::EntryType
#[macro_export]
macro_rules! select {
(($($tts:tt)*)) => {
select!($($tts)*)
};
(*) => {
$crate::Selector::Wildcard
};
($entry_type:ident) => {
$crate::Selector::Entry($crate::types::EntryType::$entry_type)
};
($binding:literal:$expr:tt) => {
$crate::Selector::Binding(
$binding.to_string(),
Box::new(select!($expr)),
)
};
($expr:tt[$($attr:literal),* $(,)?]) => {
$crate::Selector::Attr(
Box::new(select!($expr)),
vec![$($attr.to_string()),*],
)
};
(!$expr:tt) => {
$crate::Selector::Neg(Box::new(select!($expr)))
};
($lhs:tt > $rhs:tt) => {
$crate::Selector::Ancestrage(
Box::new(select!($lhs)),
Box::new(select!($rhs)),
)
};
($($expr:tt)|+) => {
$crate::Selector::Alt(vec![$(select!($expr)),*])
};
($($expr:tt)&+) => {
$crate::Selector::Multi(vec![$(select!($expr)),*])
};
}
mod parser;
use std::collections::HashMap;
use thiserror::Error;
use crate::types::EntryType;
use crate::Entry;
/// A selector used to filter bibliographies and match on entries.
#[derive(Debug, Clone, Eq, PartialEq)]
#[non_exhaustive]
pub enum Selector {
/// A wildcard selector: `*`.
Wildcard,
/// An entry type literal: `report`.
Entry(EntryType),
/// A negation: `!x`.
Neg(Box<Self>),
/// A binding: `x:misc`.
Binding(String, Box<Self>),
/// An attribute filtering: `abc[att1, attr2]`.
Attr(Box<Self>, Vec<String>),
/// An alternate selector: `a | b`.
Alt(Vec<Self>),
/// A multi-parent selector: `a & b`.
Multi(Vec<Self>),
/// An ancestrage selector: `a > b`.
Ancestrage(Box<Self>, Box<Self>),
}
impl Selector {
/// Parse a selector from a string.
pub fn parse(src: &str) -> SelectorResult<Self> {
parser::parse(src)
}
/// Checks if the selector matches the provided [`Entry`].
pub fn matches(&self, entry: &Entry) -> bool {
self.apply(entry).is_some()
}
/// Applies the selector and returns the bound element if there was a match.
///
/// This can panic if there are resolving entries which do not bind the
/// argument.
pub fn bound<'s>(&self, entry: &'s Entry, bound: &str) -> Option<&'s Entry> {
self.apply(entry).map(|mut hm| hm.remove(bound).unwrap())
}
/// Applies the selector to an [`Entry`] and returns the bound variables
/// in a hash map if there was a match.
pub fn apply<'s>(&self, entry: &'s Entry) -> Option<HashMap<String, &'s Entry>> {
match self {
Self::Wildcard => Some(HashMap::new()),
Self::Entry(entry_type) => {
if &entry.entry_type == entry_type {
Some(HashMap::new())
} else {
None
}
}
Self::Neg(expr) => {
if expr.apply(entry).is_some() {
None
} else {
Some(HashMap::new())
}
}
Self::Binding(binding, expr) => expr.apply(entry).map(|mut bound| {
bound.insert(binding.to_string(), entry);
bound
}),
Self::Attr(expr, attributes) => expr.apply(entry).and_then(|bound| {
if attributes.iter().all(|arg| entry.has(arg.as_ref())) {
Some(bound)
} else {
None
}
}),
Self::Alt(exprs) => {
for expr in exprs {
let applied = expr.apply(entry);
if applied.is_some() {
return applied;
}
}
None
}
Self::Multi(_) => None,
Self::Ancestrage(lhs, rhs) => lhs.apply(entry).and_then(|mut bound| {
let parents = &entry.parents;
if let Some((other, _)) = rhs.apply_any(parents) {
bound.extend(other);
Some(bound)
} else {
None
}
}),
}
}
fn apply_any<'s>(
&self,
entries: &'s [Entry],
) -> Option<(HashMap<String, &'s Entry>, Vec<&'s Entry>)> {
match self {
Self::Wildcard => {
if !entries.is_empty() {
Some((HashMap::new(), entries.iter().collect()))
} else {
None
}
}
Self::Entry(_) => entries
.iter()
.filter_map(|e| self.apply(e).map(|r| (r, vec![e])))
.next(),
Self::Neg(expr) => {
if expr.apply_any(entries).is_some() {
None
} else {
Some((HashMap::new(), vec![]))
}
}
Self::Binding(binding, expr) => {
expr.apply_any(entries).map(|(mut bound, es)| {
if !es.is_empty() {
bound.insert(binding.to_string(), es.get(0).unwrap());
}
(bound, vec![])
})
}
Self::Attr(expr, attributes) => {
expr.apply_any(entries).and_then(|(bound, es)| {
if !es.is_empty() {
if es
.iter()
.any(|e| attributes.iter().all(|arg| e.has(arg.as_ref())))
{
Some((bound, es))
} else {
None
}
} else {
Some((bound, es))
}
})
}
Self::Alt(exprs) => {
for expr in exprs {
let applied = expr.apply_any(entries);
if applied.is_some() {
return applied;
}
}
None
}
Self::Multi(exprs) => {
let mut consumed = vec![];
let mut res = HashMap::new();
for spec in exprs {
let mut item = None;
for (i, e) in entries.iter().enumerate() {
if consumed.contains(&i) {
continue;
}
item = spec.apply(e).map(|v| (i, v));
if item.is_some() {
break;
}
}
if let Some((index, bound)) = item {
res.extend(bound);
consumed.push(index);
} else {
return None;
}
}
let mut es = vec![];
for i in consumed.into_iter() {
es.push(entries.get(i).unwrap());
}
Some((res, es))
}
Self::Ancestrage(_, _) => entries
.iter()
.filter_map(|e| self.apply(e).map(|r| (r, vec![e])))
.next(),
}
}
}
/// A specialized result type with a selector error.
type SelectorResult<T> = Result<T, SelectorError>;
/// The error when parsing a selector expression fails.
#[derive(Debug, Clone, Eq, PartialEq, Error)]
pub enum SelectorError {
/// A value (entry type or subexpression) was expected.
#[error("missing value")]
MissingValue,
/// An attribute list contained something expected.
#[error("malformed attribute")]
MalformedAttribute,
/// A comma was expected in an attribute expression.
#[error("missing comma")]
MissingComma,
/// The parentheses are unbalanced.
#[error("unbalanced parentheses")]
UnbalancedParens,
/// The entry type is not known.
#[error("unknown entry type: `{0}`")]
UnknownEntryType(String),
}