use crate::diag::SourceResult;
use crate::engine::Engine;
use crate::foundations::{elem, Content, NativeElement, Packed, Show, StyleChain};
use crate::layout::{BlockElem, Length};

/// Repeats content to the available space.
///
/// This can be useful when implementing a custom index, reference, or outline.
///
/// Space may be inserted between the instances of the body parameter, so be
/// sure to adjust the [`justify`]($repeat.justify) parameter accordingly.
///
/// Errors if there no bounds on the available space, as it would create
/// infinite content.
///
/// # Example
/// ```example
/// Sign on the dotted line:
/// #box(width: 1fr, repeat[.])
///
/// #set text(10pt)
/// #v(8pt, weak: true)
/// #align(right)[
///   Berlin, the 22nd of December, 2022
/// ]
/// ```
#[elem(Show)]
pub struct RepeatElem {
    /// The content to repeat.
    #[required]
    pub body: Content,

    /// The gap between each instance of the body.
    #[default]
    pub gap: Length,

    /// Whether to increase the gap between instances to completely fill the
    /// available space.
    #[default(true)]
    pub justify: bool,
}

impl Show for Packed<RepeatElem> {
    fn show(&self, engine: &mut Engine, _: StyleChain) -> SourceResult<Content> {
        Ok(BlockElem::single_layouter(self.clone(), engine.routines.layout_repeat)
            .pack()
            .spanned(self.span()))
    }
}