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use std::collections::{vec_deque::IntoIter, VecDeque};
use std::fmt::{Debug, Display};
use std::hash::Hash;
use std::str::FromStr;

pub type PathIDX = usize;

/// A path to a [Tree] node
/// A [Path] is a collection of branches to follow to get to the desired node.
/// An empty [Path] represents the root of the [Tree].
///
/// # Examples
/// ```rust
/// use nb_tree::prelude::{Tree, Path};
/// let mut tree = Tree::new();
/// // Paths from string litterals, vectors, or manually built
/// let path_d: Path<String> = "/b/d".into();
/// //let path_e: Path<String> = vec!["a", "c", "e"].into();
/// //let mut path_f = Path::new();
/// //path_f.l("b").l("f");
/// // Use paths to insert data
/// tree.i("/", 0)
///     .i("/a", 1)
///     .i("/b", 2)
///     .i("/a/c", 3)
///     .i(path_d, 4)
/// //    .i(path_e, 5)
///     .i("/a/c/e", 5)
///     .i("/b/f", 6);
/// //    .i(path_f, 6);
///
/// // Use paths to retrieve data
/// assert_eq!(tree.get(&"/a/c".into()), Ok(&3));
///
/// // Use paths to remove data
/// //tree.remove_sub_tree()
/// //assert
/// ```
#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Path<B: Clone + Default + PartialEq + Eq + PartialOrd + Ord + Hash> {
    path: VecDeque<B>,
}

impl<B: Clone + Default + PartialEq + Eq + PartialOrd + Ord + Hash> Path<B> {
    pub fn new() -> Self {
        Self {
            path: VecDeque::new(),
        }
    }
    /*
    pub fn branches_mut(&mut self) -> &mut [B] {
        self.path.make_contiguous().as_mut()
    }*/

    pub fn pop_root(&mut self) -> Option<B> {
        self.path.pop_front()
    }

    pub fn pop_leaf(&mut self) -> Option<B> {
        self.path.pop_back()
    }

    pub(crate) fn path_to(&self, path_idx: PathIDX) -> Path<B> {
        Self {
            path: self.path.range(..path_idx).cloned().collect(),
        }
    }

    pub(crate) fn path_from(&self, path_idx: PathIDX) -> Path<B> {
        Self {
            path: self.path.range(path_idx..).cloned().collect(),
        }
    }

    pub fn push_leaf(&mut self, value: B) {
        self.path.push_back(value);
    }

    pub fn push_root(&mut self, value: B) {
        self.path.push_front(value);
    }

    pub fn last(&self) -> Option<&B> {
        self.path.back()
    }

    pub fn first(&self) -> Option<&B> {
        self.path.front()
    }

    pub fn iter(&self) -> std::collections::vec_deque::Iter<'_, B> {
        self.path.iter()
    }
}

//TODO: P parse error
#[derive(Debug)]
pub enum ParsePathError {
    NoRoot,
    ParseError,
}

/*
impl<P> From<P> for ParsePathError {
    fn from(value: P) -> Self {
        ParsePathError::ParseError(value)
    }
}*/

impl<B: Clone + Default + PartialEq + Eq + PartialOrd + Ord + Hash + FromStr> FromStr for Path<B> {
    type Err = ParsePathError; //<B::Err>;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if !s.contains('/') {
            return Err(ParsePathError::NoRoot);
        }
        // Skip everything preceeding the root slash
        Ok(Self {
            path: s
                .split('/')
                .skip(1)
                .filter(|s| !s.is_empty())
                .map(|s| s.parse::<B>())
                .collect::<Result<VecDeque<B>, _>>()
                .map_err(|_| ParsePathError::ParseError)?,
        })
    }
}
impl<B: Clone + Default + PartialEq + Eq + PartialOrd + Ord + Hash> From<Vec<B>> for Path<B> {
    fn from(value: Vec<B>) -> Self {
        Self { path: value.into() }
    }
}

impl<B: Clone + Default + PartialEq + Eq + PartialOrd + Ord + Hash + FromStr> From<&str>
    for Path<B>
{
    fn from(value: &str) -> Self {
        value.parse().unwrap()
    }
}
/*

impl<B: Clone + Default + PartialEq + Eq + PartialOrd + Ord + Hash, C: Into<B>> From<Vec<C>>
    for Path<B>
{
    fn from(value: Vec<C>) -> Self {
        Self {
            path: value.into_iter().map(|v| v.into()).collect(),
        }
    }
}*/

impl<B: Clone + Default + Ord + Hash> IntoIterator for Path<B> {
    type Item = B;

    type IntoIter = IntoIter<B>;

    fn into_iter(self) -> Self::IntoIter {
        self.path.into_iter()
    }
}

impl<B: Clone + Default + PartialEq + Eq + PartialOrd + Ord + Hash> FromIterator<B> for Path<B> {
    fn from_iter<T: IntoIterator<Item = B>>(iter: T) -> Self {
        Self {
            path: iter.into_iter().collect(),
        }
    }
}

impl<B: Clone + Default + Display + PartialEq + Eq + PartialOrd + Ord + Hash> Display for Path<B> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        //TODO: multi line B display management?
        for b in self.path.iter() {
            write!(f, "/{}", b)?;
        }
        Ok(())
    }
}