//! # rusty_grammar
//!
//! rusty_grammar is a library that makes use of a modified CYK algorithm to define grammars and understand language.
//!
//! # About
//! The rusty_grammar library leverages the [CYK algorithm](https://en.wikipedia.org/wiki/CYK_algorithm). It modifies it to work for words and parts of speech/writing. For example adjectives, nouns, prepositional phrases and etc. Exposes traits to define a WordBank and Grammar set. Of course grammars must be defined in CNF form. For more information on that find it at [Chomsky Normal Form](https://en.wikipedia.org/wiki/Chomsky_normal_form).
//!
//! See the rusty_grammar [website](https://docs.rs/rusty_grammar) for additional documentation and usage examples.
//!
//! # Quick Example
//! ```ignore
//! struct G {}
//! impl<'grammar> Grammar<'grammar> for G {
//!     fn convert(&self) -> Vec<GrammarRule<'grammar>> {
//! 	let mut rules = Vec::new();
//! 	rules.push(GrammarRule{ left_symbol: "ActionSentence", right_symbol: "Verb NounClause | Verb NounClause PrepClause" });
//! 	rules.push(GrammarRule{ left_symbol: "NounClause", right_symbol: "Count ANoun | Adjective Noun" });
//! 	rules.push(GrammarRule{ left_symbol: "PrepClause", right_symbol: "Prep NounClause" });
//! 	rules.push(GrammarRule{ left_symbol: "ANoun", right_symbol: "Adjective Noun" });
//! 	rules.push(GrammarRule{ left_symbol: "Adjective", right_symbol: "adjective" });
//! 	rules.push(GrammarRule{ left_symbol: "Prep", right_symbol: "prep" });
//! 	rules.push(GrammarRule{ left_symbol: "Verb", right_symbol: "verb" });
//! 	rules.push(GrammarRule{ left_symbol: "Noun", right_symbol: "noun" });
//! 	rules.push(GrammarRule{ left_symbol: "Count", right_symbol: "definiteArticle | indefiniteArticle | number" });
//! 	rules
//!     }
//! }
//!
//! struct WB {}
//! impl WordBank for WB {
//!     fn lookup(&self, word: &str) -> &str {
//! 	match word {
//! 	    "examine" => "verb",
//! 	    "sword" => "noun",
//! 	    "rusty" => "adjective",
//! 	    _ => "dne"
//! 	}
//!     }
//! }
//!
//! fn main() {
//!     let g = G{};
//!     let wb = WB{};
//!     let input = "examine rusty sword";
//!     let cyk: CYK<WB> = CYK::new(g, wb);
//!     let res = cyk.memoized_parse(input);
//!     println!("{}", res);
//!     println!("final_res: {:?}", res.get_final());
//! }
//! ```
////////////////////////////////////////////////////////////////////////////////
use std::collections::HashMap;
use std::fmt;
use std::sync::Mutex;
use itertools::{iproduct, join};
use linked_hash_map::LinkedHashMap;

#[derive(Clone, Debug)]
/// The Struct to define a Grammar Rule.
pub struct GrammarRule<'symbol> {
    /// The left side of a grammar rule.
    left_symbol: &'symbol str,
    /// The right side of a grammar rule.
    right_symbol: &'symbol str,
}

/// The trait for a grammar. For a struct to be a grammar it must implement these methods.
pub trait Grammar<'grammar> {
    /// The convert function takes whatever struct you define and generates a Vector of Grammar Rules.
    fn convert(&self) -> Vec<GrammarRule<'grammar>>;
}

/// The trait for a wordbank. For a struct to be a wordbank it must implment these methods.
pub trait WordBank {
    /// The lookup function takes whatever struct you have given a word and looks up the type of word it is. i.e. noun.
    fn lookup(&self, word: &str) -> &str;
}

/// The struct for the CYK algorithm.
pub struct CYK<'rules, W> {
    /// Grammar Rules: the list of grammar rules in CNF form.
    grammar_rules: Vec<GrammarRule<'rules>>,
    /// The struct that implments the WordBank Trait.
    word_bank: W,
}

#[derive(Clone, Debug, Hash, PartialEq)]
/// A struct to represent the poisiton of the CYK rule lookup in a hashmap. i.e. the key of a hashmap.
struct MatrixIndicator {
    x: usize,
    y: usize,
}

impl fmt::Display for MatrixIndicator {
    /// A print method for the MatrixIndicator method.
    ///
    /// # Arguments
    ///
    /// * `f` - A fmt Formatter to be passed to the write macro.
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	write!(f, "({}, {})", self.x, self.y)
    }
}

// To implment Equality for the MatrixIndicator struct.
impl Eq for MatrixIndicator {}

#[derive(Clone, Debug)]
/// A struct to store the result of the CYK algorithm.
pub struct MatrixResult {
    /// A hashmap to store all the rule conversions done by the algorithm.
    map: HashMap<MatrixIndicator, String>,
    /// The final result of what the given sentence was.
    final_res: Option<String>,
    /// The number of words in the given sentence.
    num_words: usize,
}

impl MatrixResult {
    /// A function to create an instance of the MatrixResult struct.
    fn new() -> Self {
	Self {
	    map: HashMap::new(),
	    final_res: None,
	    num_words: 0
	}
    }

    /// A function to get the final result of the CYK algorithm.
    pub fn get_final(&self) -> Option<String> {
	self.final_res.clone()
    }

    /// A function to set the final result of the CYK algorithm.
    ///
    /// # Arguments
    ///
    /// * `final_res` - The string to set for the final result of CYK algo.
    fn set_final(&mut self, final_res: String) {
	self.final_res = Some(final_res);
    }

    /// A function to insert a result into a position in the map of the result.
    fn insert(&mut self, mi: MatrixIndicator, res: String) {
	self.map.insert(mi, res);
    }

    /// A function to set the number of words in the Matrix Result. Refers to the number of words in the sentence given.
    fn set_num_words(&mut self, size: usize) {
	self.num_words = size;
    }

    /// A function to get the number of words in the Matrix Result. Refers to the number of words in the sentence given.
    pub fn get_num_words(&self) -> usize {
	self.num_words
    }
}

impl fmt::Display for MatrixResult {
    /// Function to display the MatrixResult. Shows the table printed in line by line format.
    ///
    /// # Arguments
    ///
    /// * `f` - A fmt Formatter to be passed to the write macro.
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	if self.num_words == 0 {
	    return write!(f, "No result caluclated.");
	}

	let mut output = Vec::new();
	output.push("LN# 1:".to_owned());

	for position in 0..self.num_words {
	    output.push(format!("\t({}, {}):", position+1, position+1));
	    let entry = self.map.get(&MatrixIndicator{ x: position, y: position }).expect("Can not be empty");
	    output.push(format!("{}", entry));
	}
	output.push("\n".to_owned());

	let mut line_num = 2;
	for ln in 1..self.num_words {
	    output.push(format!("LN# {}:", line_num));

	    for x in 0..self.num_words-ln {
		let entry = self.map.get(&MatrixIndicator{ x, y: x+ln }).expect("Can not be empty");
		if entry == "" {
		    continue;
		}
		output.push(format!("\t({}, {}):", x, x+ln));
		output.push(format!("{}", entry));
	    }
	    output.push("\n".to_owned());
	    line_num += 1;
	}

	write!(f, "{}", join(&output, ""))
    }
}


lazy_static::lazy_static! {
    /// Used for the memoized version of parse. Memoizes 100 sentences.
    static ref MEMO: Mutex<LinkedHashMap<&'static str, MatrixResult>> = Mutex::new(LinkedHashMap::with_capacity(101));
}

/// A function to join two strings into one.
///
/// # Arguments
///
/// * `str1` - The frist string to be split and combined.
/// * `str2` - The second string to be split and combined.
fn vec_production(str1: &str, str2: &str) -> Vec<String> {
    iproduct!(
	str1.split(" ").collect::<Vec<&str>>(),
	str2.split(" ").collect::<Vec<&str>>())
	.map(|vals| {
	    join(&[vals.0, vals.1], " ")
	})
	.collect::<Vec<String>>()
}

impl<'grammar, W> CYK<'grammar, W> where
    W: WordBank {
    /// Creates a new instance of a CYK algo with a set of rules and a word brank.
    ///
    /// # Arguments
    ///
    /// * `rules` - The object that implements the Grammar Trait.
    /// * `word_bank` - The object that implements the WordBank Trait.
    pub fn new<G>(rules: G, word_bank: W) -> Self where
	G: Grammar<'grammar> {
	Self {
	    grammar_rules: rules.convert(),
	    word_bank
	}
    }

    /// Finding the terminal left side rule for a grammar given a terminal right side rule.
    fn find_terminal_assign(&self, terminal: &str) -> String {
	let mut res = Vec::new();

	for grammar in &self.grammar_rules {
	    for rule in grammar.right_symbol.split(" | ").collect::<Vec<&str>>() {
		if rule == terminal {
		    res.push(grammar.left_symbol.clone());
		}
	    }
	}
	
	join(res, " ")
    }

    /// A function that parses the given sentence for the rules and wordbank in the CYK struct.
    ///
    /// # Arguments
    ///
    /// * `input` - The input string to be parsed and validated.
    pub fn parse<'word>(&self, input: &'word str) -> MatrixResult {
	let mut result: MatrixResult = MatrixResult::new();
	
	let words = input.split_whitespace().collect::<Vec<&str>>();
	let num_words = words.len();
	result.set_num_words(num_words);
	
	for (pos, word) in words.iter().enumerate() {
	    let terminal = self.word_bank.lookup(word);
	    result.insert(MatrixIndicator{ x: pos, y: pos }, self.find_terminal_assign(terminal));
	}

	for l in 1..=num_words {
	    for i in 0..(num_words - l) {
		let j = i + l;

		let mut targets: Vec<String> = Vec::new();
		for k in 1..=j {
		    let empty = String::from("");
		    let fv = result.map.get(&MatrixIndicator{ x: i, y: i+k-1 }).unwrap_or(&empty);
		    let sv = result.map.get(&MatrixIndicator{ x: i+k, y: j }).unwrap_or(&empty);
		    let mut products = vec_production(fv, sv);
		    targets.append(&mut products);
		}

		let mut res = String::from("");
		for target in targets {
		    let target_symbol = self.find_terminal_assign(target.as_str());
		    
		    if !res.contains(&target_symbol) {
			res = match res.as_str() {
			    "" => target_symbol,
			    _ => join(&[res, target_symbol], " ")
			};
		    }
		}

		result.insert(MatrixIndicator{ x: i, y: j }, res);
	    }
	}
	
	let final_result = result.map.get(&MatrixIndicator{ x: 0, y: num_words - 1 }).expect("Can not be empty").to_owned();
	result.set_final(final_result);
	
	return result;
    }

    /// A memoized version of the parse function. i.e. if sentence exists in map just instant return results.
    ///
    /// # Arguments
    ///
    /// * `input` - The input string to be parsed and validated.
    pub fn memoized_parse<'word>(&self, input: &'static str) -> MatrixResult {
	if MEMO.lock().expect("Memo should not be NONE.").contains_key(input) {
	    return MEMO.lock().expect("Memo should not be NONE.").get(input).expect("Should never be none.").clone();
	}

	let res = self.parse(input);
	MEMO.lock().expect("Memo should not be NONE.").insert(input, res.clone());
	if MEMO.lock().expect("Memo should not be NONE.").len() > 100 {
	    MEMO.lock().expect("Memo should not be NONE.").pop_back();
	}

	res
    }


}

#[cfg(test)]
mod tests {
    use super::*;
    
    struct G {}

    impl<'grammar> Grammar<'grammar> for G {
	fn convert(&self) -> Vec<GrammarRule<'grammar>> {
	    let mut rules = Vec::new();
	    rules.push(GrammarRule{ left_symbol: "ActionSentence", right_symbol: "Verb Noun | Verb NounClause | ActionSentence PrepClause" });
	    rules.push(GrammarRule{ left_symbol: "DescriptiveSentence", right_symbol: "Noun Verb Adjective" });
	    rules.push(GrammarRule{ left_symbol: "NounClause", right_symbol: "Count ANoun | Adjective Noun"});
	    rules.push(GrammarRule{ left_symbol: "PrepClause", right_symbol: "Prep Noun" });
	    rules.push(GrammarRule{ left_symbol: "ANoun", right_symbol: "Adjective Noun" });
	    rules.push(GrammarRule{ left_symbol: "Adjective", right_symbol: "adjective" });
	    rules.push(GrammarRule{ left_symbol: "Prep", right_symbol: "prep" });
	    rules.push(GrammarRule{ left_symbol: "Verb", right_symbol: "verb" });
	    rules.push(GrammarRule{ left_symbol: "Noun", right_symbol: "noun" });
	    rules.push(GrammarRule{ left_symbol: "Count", right_symbol: "definiteArticle | indefiniteArticle | number" });
	    rules
	}
    }

    struct WB {}

    impl WordBank for WB {
	fn lookup(&self, word: &str) -> &str {
	    match word {
		"examine" => "verb",
		"sword" => "noun",
		"rusty" => "adjective",
		"google" => "verb",
		// "google" => "verb | noun",
		"is" => "verb",
		"cool" => "adjective",
		"from" => "prep",
		"apple" => "noun",
		"take" => "verb",
		"table" => "noun",
		_ => "fuck"
	    }
	}
    }
    
    #[test]
    fn basic_test() {
	let g = G{};
	let wb = WB{};
	let input = "examine rusty sword";
	let cyk: CYK<WB> = CYK::new(g, wb);
	let res = cyk.parse(input);
	assert_eq!(Some("ActionSentence".to_owned()), res.get_final());
    }

    #[test]
    fn double_meaning_test() {
	let g = G{};
	let wb = WB{};
	let input = "google sword";
	let cyk: CYK<WB> = CYK::new(g, wb);
	let res = cyk.parse(input);
	assert_eq!(Some("ActionSentence".to_owned()), res.get_final());

	// TODO: allow double meaning words 
	// let input2 = "google is cool";
	// let res2 = cyk.parse(input2);
	// assert_eq!(Some("DescriptiveSentence".to_owned()), res.get_final());
    }

    #[test]
    fn complicated_test() {
	let g = G{};
	let wb = WB{};
	let input = "take apple from table";
	let cyk: CYK<WB> = CYK::new(g, wb);
	let res = cyk.parse(input);
	assert_eq!(Some("ActionSentence".to_owned()), res.get_final());
    }
}