//! Datastructures for cached pattern

use std::fmt;

use itertools::Itertools;
use orchid_base::interner::Tok;
use orchid_base::name::Sym;
use orchid_base::side::Side;
use orchid_base::tokens::{PARENS, Paren};

pub enum ScalMatcher {
	Name(Sym),
	S(Paren, Box<AnyMatcher>),
	Lambda(Box<AnyMatcher>, Box<AnyMatcher>),
	Placeh { key: Tok<String> },
}

pub enum VecMatcher {
	Placeh {
		key: Tok<String>,
		nonzero: bool,
	},
	Scan {
		left: Box<VecMatcher>,
		sep: Vec<ScalMatcher>,
		right: Box<VecMatcher>,
		/// The separator traverses the sequence towards this side
		direction: Side,
	},
	Middle {
		/// Matches the left outer region
		left: Box<VecMatcher>,
		/// Matches the left separator
		left_sep: Vec<ScalMatcher>,
		/// Matches the middle - can only ever be a plain placeholder
		mid: Box<VecMatcher>,
		/// Matches the right separator
		right_sep: Vec<ScalMatcher>,
		/// Matches the right outer region
		right: Box<VecMatcher>,
		/// Order of significance for sorting equally good projects based on
		/// the length of matches on either side.
		///
		/// Vectorial keys that appear on either side, in priority order
		key_order: Vec<Tok<String>>,
	},
}

pub enum AnyMatcher {
	Scalar(Vec<ScalMatcher>),
	Vec { left: Vec<ScalMatcher>, mid: VecMatcher, right: Vec<ScalMatcher> },
}

// ################ Display ################

impl fmt::Display for ScalMatcher {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		match self {
			Self::Placeh { key } => write!(f, "${key}"),
			Self::Name(n) => write!(f, "{n}"),
			Self::S(t, body) => {
				let (l, r, _) = PARENS.iter().find(|r| r.2 == *t).unwrap();
				write!(f, "{l}{body}{r}")
			},
			Self::Lambda(arg, body) => write!(f, "\\{arg}.{body}"),
		}
	}
}

impl fmt::Display for VecMatcher {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		match self {
			Self::Placeh { key, nonzero: true } => write!(f, "...${key}"),
			Self::Placeh { key, nonzero: false } => write!(f, "..${key}"),
			Self::Scan { left, sep, right, direction } => {
				let arrow = if direction == &Side::Left { "<==" } else { "==>" };
				write!(f, "Scan{{{left} {arrow} {} {arrow} {right}}}", sep.iter().join(" "))
			},
			Self::Middle { left, left_sep, mid, right_sep, right, .. } => {
				let left_sep_s = left_sep.iter().join(" ");
				let right_sep_s = right_sep.iter().join(" ");
				write!(f, "Middle{{{left}|{left_sep_s}|{mid}|{right_sep_s}|{right}}}")
			},
		}
	}
}

impl fmt::Display for AnyMatcher {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		match self {
			Self::Scalar(s) => {
				write!(f, "({})", s.iter().join(" "))
			},
			Self::Vec { left, mid, right } => {
				let lefts = left.iter().join(" ");
				let rights = right.iter().join(" ");
				write!(f, "[{lefts}|{mid}|{rights}]")
			},
		}
	}
}