//! Definitions for the 'classical' mechanism for computation.
//!
//! Allows to define the 'classical' mechanism to compute in a Reaction System
//! (RS) Framework.

use serde::{Deserialize, Serialize};
use std::hash::Hash;

use super::element::{IdState, IdType};
use super::set::{BasicSet, ExtensionsSet, Set, PositiveSet};
use super::translator::{Translator, PrintableWithTranslator, Formatter};

pub trait BasicReaction:
Clone + Default + Eq + Hash + Serialize + PrintableWithTranslator
where for<'de> Self: Deserialize<'de>,
{
	type Set: BasicSet;
	fn enabled(&self, state: &Self::Set) -> bool;
	fn compute_step(&self, state: &Self::Set) -> Option<&Self::Set>;
}

pub trait ExtensionReaction: Sized {
	type Set: BasicSet;

	fn compute_all(reactions: &[Self], state: &Self::Set) -> Self::Set;

	fn find_loop(
		reactions: &[Self],
		entities: Self::Set,
		q: &Self::Set
	) -> (Vec<Self::Set>, Vec<Self::Set>);

	fn find_only_loop(
		reactions: &[Self],
		entities: Self::Set,
		q: &Self::Set
	) -> Vec<Self::Set>;

	fn find_prefix_len_loop(
		reactions: &[Self],
		entities: Self::Set,
		q: &Self::Set
	) -> (usize, Vec<Self::Set>);

	fn lollipops_only_loop_decomposed_q(
		reactions: &[Self],
		entities: &Self::Set,
		q: &Self::Set
	) -> Vec<Self::Set>;
}

/// Implementations for all reactions.
impl<T: BasicReaction<Set = Set>, Set: BasicSet> ExtensionReaction for T {
	type Set = Set;

	/// Computes the result of a series of reactions. Returns the union of all
	/// products.
	/// see result
	fn compute_all(
		reactions: &[Self],
		state: &Set
	) -> Set
	where Self: Sized {
		reactions.iter().fold(Set::default(), |mut acc: Set, r| {
			acc.extend(r.compute_step(state));
			acc
		})
	}

	/// Finds the loops by simulating the system.
	fn find_loop(
		reactions: &[Self],
		entities: Set,
		q: &Set
	) -> (Vec<Set>, Vec<Set>) {
		let mut entities = entities;
		let mut trace = vec![];
		loop {
			if let Some((prefix, hoop)) = entities.split(&trace) {
				return (prefix.to_vec(), hoop.to_vec());
			} else {
				let t = entities.union(q);
				let products = Self::compute_all(reactions, &t);
				trace.push(entities.clone());
				entities = products;
			}
		}
	}


	/// Finds the loops by simulating the system.
	fn find_only_loop(
		reactions: &[Self],
		entities: Set,
		q: &Set
	) -> Vec<Set> {
		let mut entities = entities;
		let mut trace = vec![];
		loop {
			if let Some((_prefix, hoop)) = entities.split(&trace) {
				return hoop.to_vec();
			} else {
				let t = entities.union(q);
				let products = Self::compute_all(reactions, &t);
				trace.push(entities.clone());
				entities = products;
			}
		}
	}


	/// Finds the loops and the length of the prefix by simulating the system.
	fn find_prefix_len_loop(
		reactions: &[Self],
		entities: Set,
		q: &Set
	) -> (usize, Vec<Set>) {
		let mut entities = entities;
		let mut trace = vec![];
		loop {
			if let Some((prefix, hoop)) = entities.split(&trace) {
				return (prefix.len(), hoop.to_vec());
			} else {
				let t = entities.union(q);
				let products = Self::compute_all(reactions, &t);
				trace.push(entities.clone());
				entities = products;
			}
		}
	}


	/// see loop/5
	fn lollipops_only_loop_decomposed_q(
		reactions: &[Self],
		entities: &Set,
		q: &Set,
	) -> Vec<Set> {
		let find_loop_fn =
			|q| Self::find_only_loop(reactions,
									 entities.clone(),
									 q);
		find_loop_fn(q)
	}
}




// -----------------------------------------------------------------------------

/// Basic structure for a reaction.
#[derive(Clone, Debug, Default, Serialize, Deserialize, PartialEq, Eq, Hash)]
pub struct Reaction {
	pub reactants: Set,
	pub inhibitors: Set,
	pub products: Set,
}

impl BasicReaction for Reaction {
	type Set = Set;

	/// returns true if ```current_state``` enables the reaction
	/// see enable
	fn enabled(&self, current_state: &Self::Set) -> bool {
		self.reactants.is_subset(current_state)
			&& self.inhibitors.is_disjoint(current_state)
	}

	/// Computes the result of a single reaction (if enabled returns the
	/// products) otherwise returns None.
	/// see result
	fn compute_step(&self, state: &Self::Set) -> Option<&Self::Set> {
		if self.enabled(state) {
			Some(&self.products)
		} else {
			None
		}
	}
}

impl PrintableWithTranslator for Reaction {
	fn print(&self, f: &mut std::fmt::Formatter, translator: &Translator)
			 -> std::fmt::Result {
		write!(
			f,
			"(r: {}, i: {}, p: {})",
			Formatter::from(translator, &self.reactants),
			Formatter::from(translator, &self.inhibitors),
			Formatter::from(translator, &self.products)
		)
	}
}

impl Reaction {
	pub fn from(reactants: Set, inhibitors: Set, products: Set) -> Self {
		Reaction { reactants, inhibitors, products }
	}

	pub fn all_products(reactions: &[Self]) -> Set {
		reactions.iter().fold(
			Set::default(),
			|acc, r|
			acc.union(&r.products)
		)
	}

	pub fn all_reactions_with_product<'a>(
		reactions: &'a [Self],
		el: &IdType
	) -> Vec<&'a Self> {
		reactions.iter().fold(
			vec![],
			|mut acc, r| {
				if r.products.contains(el) {
					acc.push(r);
				}
				acc
			}
		)
	}
}

// -----------------------------------------------------------------------------

#[derive(Clone, Debug, Default, Serialize, Deserialize, PartialEq, Eq, Hash)]
pub struct PositiveReaction {
	pub reactants: PositiveSet,
	pub products: PositiveSet
}

impl BasicReaction for PositiveReaction {
	type Set = PositiveSet;

	fn enabled(&self, state: &Self::Set) -> bool {
		self.reactants.is_subset(state)
	}

	fn compute_step(&self, state: &Self::Set) -> Option<&Self::Set> {
		if self.enabled(state) {
			Some(&self.products)
		} else {
			None
		}
	}
}

impl PrintableWithTranslator for PositiveReaction {
	fn print(&self, f: &mut std::fmt::Formatter, translator: &Translator)
			 -> std::fmt::Result {
		write!(
			f,
			"(r: {}, p: {})",
			Formatter::from(translator, &self.reactants),
			Formatter::from(translator, &self.products),
		)
	}
}

impl PositiveReaction {
	pub fn from(reactants: PositiveSet, products: PositiveSet) -> Self {
		Self { reactants, products }
	}

	pub fn create(reactants: Set, inhibitors: Set, products: Set) -> Self {
		Self { reactants:
			   reactants.to_positive_set(IdState::Positive).union(
				   &inhibitors.to_positive_set(IdState::Negative)
			   ),
			   products: products.to_positive_set(IdState::Positive) }
	}
}