typst/crates/typst-library/src/model/quote.rs

use typst_syntax::Span;

use crate::foundations::{
    cast, elem, Content, Depth, Label, NativeElement, Packed, ShowSet, Smart, StyleChain,
    Styles,
};
use crate::introspection::Locatable;
use crate::layout::{BlockElem, Em, PadElem};
use crate::model::{CitationForm, CiteElem};
use crate::text::{SmartQuotes, SpaceElem, TextElem};

/// Displays a quote alongside an optional attribution.
///
/// # Example
/// ```example
/// Plato is often misquoted as the author of #quote[I know that I know
/// nothing], however, this is a derivation form his original quote:
///
/// #set quote(block: true)
///
/// #quote(attribution: [Plato])[
///   ... ἔοικα γοῦν τούτου γε σμικρῷ τινι αὐτῷ τούτῳ σοφώτερος εἶναι, ὅτι
///   ἃ μὴ οἶδα οὐδὲ οἴομαι εἰδέναι.
/// ]
/// #quote(attribution: [from the Henry Cary literal translation of 1897])[
///   ... I seem, then, in just this little thing to be wiser than this man at
///   any rate, that what I do not know I do not think I know either.
/// ]
/// ```
///
/// By default block quotes are padded left and right by `{1em}`, alignment and
/// padding can be controlled with show rules:
/// ```example
/// #set quote(block: true)
/// #show quote: set align(center)
/// #show quote: set pad(x: 5em)
///
/// #quote[
///   You cannot pass... I am a servant of the Secret Fire, wielder of the
///   flame of Anor. You cannot pass. The dark fire will not avail you,
///   flame of Udûn. Go back to the Shadow! You cannot pass.
/// ]
/// ```
#[elem(Locatable, ShowSet)]
pub struct QuoteElem {
    /// Whether this is a block quote.
    ///
    /// ```example
    /// An inline citation would look like
    /// this: #quote(
    ///   attribution: [René Descartes]
    /// )[
    ///   cogito, ergo sum
    /// ], and a block equation like this:
    /// #quote(
    ///   block: true,
    ///   attribution: [JFK]
    /// )[
    ///   Ich bin ein Berliner.
    /// ]
    /// ```
    pub block: bool,

    /// Whether double quotes should be added around this quote.
    ///
    /// The double quotes used are inferred from the `quotes` property on
    /// [smartquote], which is affected by the `lang` property on [text].
    ///
    /// - `{true}`: Wrap this quote in double quotes.
    /// - `{false}`: Do not wrap this quote in double quotes.
    /// - `{auto}`: Infer whether to wrap this quote in double quotes based on
    ///   the `block` property. If `block` is `{false}`, double quotes are
    ///   automatically added.
    ///
    /// ```example
    /// #set text(lang: "de")
    ///
    /// Ein deutsch-sprechender Author
    /// zitiert unter umständen JFK:
    /// #quote[Ich bin ein Berliner.]
    ///
    /// #set text(lang: "en")
    ///
    /// And an english speaking one may
    /// translate the quote:
    /// #quote[I am a Berliner.]
    /// ```
    pub quotes: Smart<bool>,

    /// The attribution of this quote, usually the author or source. Can be a
    /// label pointing to a bibliography entry or any content. By default only
    /// displayed for block quotes, but can be changed using a `{show}` rule.
    ///
    /// ```example
    /// #quote(attribution: [René Descartes])[
    ///   cogito, ergo sum
    /// ]
    ///
    /// #show quote.where(block: false): it => {
    ///   ["] + h(0pt, weak: true) + it.body + h(0pt, weak: true) + ["]
    ///   if it.attribution != none [ (#it.attribution)]
    /// }
    ///
    /// #quote(
    ///   attribution: link("https://typst.app/home")[typst.app]
    /// )[
    ///   Compose papers faster
    /// ]
    ///
    /// #set quote(block: true)
    ///
    /// #quote(attribution: <tolkien54>)[
    ///   You cannot pass... I am a servant
    ///   of the Secret Fire, wielder of the
    ///   flame of Anor. You cannot pass. The
    ///   dark fire will not avail you, flame
    ///   of Udûn. Go back to the Shadow! You
    ///   cannot pass.
    /// ]
    ///
    /// #bibliography("works.bib", style: "apa")
    /// ```
    pub attribution: Option<Attribution>,

    /// The quote.
    #[required]
    pub body: Content,

    /// The nesting depth.
    #[internal]
    #[fold]
    #[ghost]
    pub depth: Depth,
}

impl QuoteElem {
    /// Quotes the body content with the appropriate quotes based on the current
    /// styles and surroundings.
    pub fn quoted(body: Content, styles: StyleChain<'_>) -> Content {
        let quotes = SmartQuotes::get_in(styles);

        // Alternate between single and double quotes.
        let Depth(depth) = styles.get(QuoteElem::depth);
        let double = depth % 2 == 0;

        Content::sequence([
            TextElem::packed(quotes.open(double)),
            body,
            TextElem::packed(quotes.close(double)),
        ])
        .set(QuoteElem::depth, Depth(1))
    }
}

/// Attribution for a [quote](QuoteElem).
#[derive(Debug, Clone, PartialEq, Hash)]
pub enum Attribution {
    Content(Content),
    Label(Label),
}

impl Attribution {
    /// Realize as an em dash followed by text or a citation.
    pub fn realize(&self, span: Span) -> Content {
        Content::sequence([
            TextElem::packed('—'),
            SpaceElem::shared().clone(),
            match self {
                Attribution::Content(content) => content.clone(),
                Attribution::Label(label) => CiteElem::new(*label)
                    .with_form(Some(CitationForm::Prose))
                    .pack()
                    .spanned(span),
            },
        ])
    }
}

cast! {
    Attribution,
    self => match self {
        Self::Content(content) => content.into_value(),
        Self::Label(label) => label.into_value(),
    },
    content: Content => Self::Content(content),
    label: Label => Self::Label(label),
}

impl ShowSet for Packed<QuoteElem> {
    fn show_set(&self, styles: StyleChain) -> Styles {
        let mut out = Styles::new();
        if self.block.get(styles) {
            out.set(PadElem::left, Em::new(1.0).into());
            out.set(PadElem::right, Em::new(1.0).into());
            out.set(BlockElem::above, Smart::Custom(Em::new(2.4).into()));
            out.set(BlockElem::below, Smart::Custom(Em::new(1.8).into()));
        }
        out
    }
}