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use super::Row;
use crate::utils::lines::spans;
use crate::utils::span::{IndexedSpan, SpannedText};

/// Generates rows of text in constrained width.
///
/// Given a long text and a width constraint, it iterates over
/// substrings of the text, each within the constraint.
pub struct LinesIterator<'a> {
    iter: spans::LinesIterator<DummySpannedText<'a>>,

    /// Available width. Don't output lines wider than that.
    width: usize,
}

struct DummySpannedText<'a> {
    content: &'a str,
    attrs: Vec<IndexedSpan<()>>,
}

impl<'a> DummySpannedText<'a> {
    fn new(content: &'a str) -> Self {
        let attrs = vec![IndexedSpan::simple_borrowed(content, ())];
        DummySpannedText { content, attrs }
    }
}

impl<'a> SpannedText for DummySpannedText<'a> {
    type S = IndexedSpan<()>;

    fn source(&self) -> &str {
        self.content
    }

    fn spans(&self) -> &[IndexedSpan<()>] {
        &self.attrs
    }
}

impl<'a> LinesIterator<'a> {
    /// Returns a new `LinesIterator` on `content`.
    ///
    /// Yields rows of `width` cells or less.
    pub fn new(content: &'a str, width: usize) -> Self {
        let iter =
            spans::LinesIterator::new(DummySpannedText::new(content), width);
        LinesIterator { iter, width }
    }

    /// Leave a blank cell at the end of lines.
    ///
    /// Unless a word had to be truncated, in which case
    /// it takes the entire width.
    pub fn show_spaces(self) -> Self {
        let iter = self.iter.show_spaces();
        let width = self.width;
        LinesIterator { iter, width }
    }
}

impl<'a> Iterator for LinesIterator<'a> {
    type Item = Row;

    fn next(&mut self) -> Option<Row> {
        let row = self.iter.next()?;

        let start = row.segments.first()?.start;
        let end = row.segments.last()?.end;

        let width = row.width;

        Some(Row { start, end, width })
    }
}