use crate::{movement::Direction, syntax::TreeCursor, Range, RopeSlice, Selection, Syntax};

pub fn expand_selection(syntax: &Syntax, text: RopeSlice, selection: Selection) -> Selection {
    let cursor = &mut syntax.walk();

    selection.transform(|range| {
        let from = text.char_to_byte(range.from()) as u32;
        let to = text.char_to_byte(range.to()) as u32;

        let byte_range = from..to;
        cursor.reset_to_byte_range(from, to);

        while cursor.node().byte_range() == byte_range {
            if !cursor.goto_parent() {
                break;
            }
        }

        let node = cursor.node();
        let from = text.byte_to_char(node.start_byte() as usize);
        let to = text.byte_to_char(node.end_byte() as usize);

        Range::new(to, from).with_direction(range.direction())
    })
}

pub fn shrink_selection(syntax: &Syntax, text: RopeSlice, selection: Selection) -> Selection {
    selection.transform(move |range| {
        let (from, to) = range.into_byte_range(text);
        let mut cursor = syntax.walk();
        cursor.reset_to_byte_range(from, to);

        if let Some(node) = cursor
            .into_iter()
            .find(|node| node.is_named() && node.is_contained_within(from..to))
        {
            return Range::from_node(node, text, range.direction());
        }

        range
    })
}

pub fn select_next_sibling(syntax: &Syntax, text: RopeSlice, selection: Selection) -> Selection {
    selection.transform(move |range| {
        let (from, to) = range.into_byte_range(text);
        let mut cursor = syntax.walk();
        cursor.reset_to_byte_range(from, to);

        while !cursor.goto_next_sibling() {
            if !cursor.goto_parent() {
                return range;
            }
        }

        Range::from_node(cursor.node(), text, Direction::Forward)
    })
}

pub fn select_prev_sibling(syntax: &Syntax, text: RopeSlice, selection: Selection) -> Selection {
    selection.transform(move |range| {
        let (from, to) = range.into_byte_range(text);
        let mut cursor = syntax.walk();
        cursor.reset_to_byte_range(from, to);

        while !cursor.goto_previous_sibling() {
            if !cursor.goto_parent() {
                return range;
            }
        }

        Range::from_node(cursor.node(), text, Direction::Backward)
    })
}

pub fn select_all_siblings(syntax: &Syntax, text: RopeSlice, selection: Selection) -> Selection {
    let mut cursor = syntax.walk();
    selection.transform_iter(move |range| {
        let (from, to) = range.into_byte_range(text);
        cursor.reset_to_byte_range(from, to);

        if !cursor.goto_parent_with(|parent| parent.child_count() > 1) {
            return vec![range].into_iter();
        }

        select_children(&mut cursor, text, range).into_iter()
    })
}

pub fn select_all_children(syntax: &Syntax, text: RopeSlice, selection: Selection) -> Selection {
    let mut cursor = syntax.walk();
    selection.transform_iter(move |range| {
        let (from, to) = range.into_byte_range(text);
        cursor.reset_to_byte_range(from, to);
        select_children(&mut cursor, text, range).into_iter()
    })
}

fn select_children(cursor: &mut TreeCursor, text: RopeSlice, range: Range) -> Vec<Range> {
    let children = cursor
        .children()
        .filter(|child| child.is_named())
        .map(|child| Range::from_node(child, text, range.direction()))
        .collect::<Vec<_>>();

    if !children.is_empty() {
        children
    } else {
        vec![range]
    }
}