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use super::{ChildPosition, Direction, Parenthood};
use derive_more::{AsRef, Deref, Display, Into};
use fmt_iter::FmtIter;
use pipe_trait::Pipe;
use std::fmt::{Display, Error, Formatter};
use zero_copy_pads::Width;

/// Determine 3 characters to use as skeletal component that connect a node
/// to the rest of the tree.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct TreeSkeletalComponent {
    /// Whether the node is the last child amongst its parent's `children`.
    pub child_position: ChildPosition,
    /// The direction of the visualization of the tree.
    pub direction: Direction,
    /// Whether the node has children.
    pub parenthood: Parenthood,
}

/// String made by calling [`TreeSkeletalComponent::visualize`](TreeSkeletalComponent).
#[derive(Debug, Clone, Copy, PartialEq, Eq, AsRef, Deref, Display, Into)]
pub struct TreeSkeletalComponentVisualization(&'static str);

impl TreeSkeletalComponent {
    /// Determine 3 characters to use as skeletal component that connect a node
    /// to the rest of the tree.
    pub const fn visualize(self) -> TreeSkeletalComponentVisualization {
        use ChildPosition::*;
        use Direction::*;
        use Parenthood::*;
        let result = match (self.child_position, self.direction, self.parenthood) {
            (Init, BottomUp, Parent) => "├─┴",
            (Init, BottomUp, Childless) => "├──",
            (Init, TopDown, Parent) => "├─┬",
            (Init, TopDown, Childless) => "├──",
            (Last, BottomUp, Parent) => "┌─┴",
            (Last, BottomUp, Childless) => "┌──",
            (Last, TopDown, Parent) => "└─┬",
            (Last, TopDown, Childless) => "└──",
        };
        TreeSkeletalComponentVisualization(result)
    }
}

impl Display for TreeSkeletalComponent {
    fn fmt(&self, formatter: &mut Formatter<'_>) -> Result<(), Error> {
        write!(formatter, "{}", self.visualize())
    }
}

impl Width for TreeSkeletalComponent {
    fn width(&self) -> usize {
        self.visualize().width()
    }
}

/// Horizontal slice of a tree of the height of exactly 1 line of text.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct TreeHorizontalSlice<Name: Width> {
    pub(super) ancestor_relative_positions: Vec<ChildPosition>,
    pub(super) skeletal_component: TreeSkeletalComponent,
    pub(super) name: Name,
}

impl<Name: Width> TreeHorizontalSlice<Name> {
    #[inline]
    fn depth(&self) -> usize {
        self.ancestor_relative_positions.len()
    }

    #[inline]
    fn indent_width(&self) -> usize {
        self.depth() * 2
    }

    #[inline]
    fn required_width(&self) -> usize {
        self.indent_width() + self.skeletal_component.width()
    }

    #[inline]
    fn indent(&self) -> impl Display + '_ {
        self.ancestor_relative_positions
            .iter()
            .map(|position| match position {
                ChildPosition::Init => "│ ",
                ChildPosition::Last => "  ",
            })
            .pipe(FmtIter::from)
    }
}

impl<Name: Width> Display for TreeHorizontalSlice<Name> {
    fn fmt(&self, formatter: &mut Formatter<'_>) -> Result<(), Error> {
        write!(
            formatter,
            "{}{}{}",
            self.indent(),
            self.skeletal_component,
            &self.name,
        )
    }
}

impl<Name: Width> Width for TreeHorizontalSlice<Name> {
    fn width(&self) -> usize {
        self.required_width() + self.name.width()
    }
}

impl TreeHorizontalSlice<String> {
    /// Truncate the name to fit specified `max_width`.
    ///
    /// * If `max_width` is already sufficient, do nothing other than return `Ok(())`.
    /// * If `max_width` is insufficient even for the required part, return `Err(N)`
    ///   where `N` is the required width.
    /// * If `max_width` is sufficient for the required part but insufficient for the
    ///   name, truncate and add `"..."` to the name.
    pub fn truncate(&mut self, max_width: usize) -> Result<(), usize> {
        if self.width() <= max_width {
            return Ok(());
        }

        let min_width = self.required_width() + "...".len();
        if min_width >= max_width {
            return Err(min_width);
        }

        self.name.truncate(max_width - min_width);
        self.name += "...";
        Ok(())
    }
}