swiftlet 0.2.0

use crate::error::{LexerError, ParseError, SwiftletError};
use crate::lexer::TokenMatch;
use crate::{
    ParserConfig,
    ast::Ast,
    grammar::{Rule, RuleMeta},
    lexer::{Symbol, Token, Tokenizer},
    non_terms,
    parser::ParserBackend,
    parser::utils::dot_state,
    parser_frontends::GrammarRuntime,
    terms,
};
use indexmap::IndexSet;
use std::collections::{HashMap, HashSet};
use std::fmt::Display;
use std::iter::Iterator;
use std::sync::Arc;

// Type Alias
pub(crate) type SymbolSet = IndexSet<Arc<Symbol>>;
pub(crate) type SymbolMap = HashMap<Arc<Symbol>, Vec<(usize, Arc<Rule>)>>;
pub(crate) type ItemSet = HashSet<Arc<ClrItem>>;
pub(crate) type VecItemSet = Vec<ItemSet>;
pub(crate) type StateSymbol = HashMap<usize, HashSet<Arc<Symbol>>>;
pub(crate) type Action = HashMap<(usize, Arc<Symbol>), IndexSet<ParseAction>>;
pub(crate) type GoTo = HashMap<(usize, Arc<Symbol>), usize>;
pub(crate) type First = HashMap<Arc<Symbol>, HashSet<Arc<Symbol>>>;
type ItemSetKey = Vec<(usize, usize, bool, String)>;

/// Describes a parser table action for the CLR automaton.
#[derive(Debug, Hash, PartialEq, Eq, Clone)]
pub enum ParseAction {
    Shift(usize),
    Reduce(usize),
    Accepted,
}

impl ParseAction {
    /// Returns action kind label.
    fn name(&self) -> String {
        match self {
            ParseAction::Shift(_) => "Shift".to_string(),
            ParseAction::Reduce(_) => "Reduce".to_string(),
            ParseAction::Accepted => "Accepted".to_string(),
        }
    }
}

/// Represents a CLR item with a lookahead symbol.
#[derive(Eq, Hash, PartialEq, Debug)]
pub(crate) struct ClrItem {
    pub(crate) rule_id: usize,
    pub(crate) dot: usize,
    pub(crate) rule: Arc<Rule>,
    pub(crate) lookahead: Arc<Symbol>,
}

impl ClrItem {
    /// Creates an LR item with lookahead.
    fn new(rule_id: usize, dot: usize, rule: Arc<Rule>, lookahead: Arc<Symbol>) -> ClrItem {
        ClrItem {
            rule_id,
            dot,
            rule,
            lookahead,
        }
    }

    /// Returns whether dot is at rule end.
    pub(crate) fn is_complete(&self) -> bool {
        self.dot == self.rule.len()
    }

    /// Returns whether `symbol` is the next expected symbol.
    pub(crate) fn is_next_symbol(&self, symbol: &Arc<Symbol>) -> bool {
        if self.is_complete() {
            return false;
        }
        self.rule.expansion[self.dot] == *symbol
    }

    /// Returns next symbol after dot.
    pub(crate) fn next_symbol(&self) -> Option<&Arc<Symbol>> {
        if self.is_complete() {
            return None;
        }
        Some(&self.rule.expansion[self.dot])
    }

    /// Returns a new item with dot advanced by one.
    fn move_dot(&self) -> Option<Self> {
        if self.is_complete() {
            return None;
        }
        Some(ClrItem::new(
            self.rule_id,
            self.dot + 1,
            self.rule.clone(),
            self.lookahead.clone(),
        ))
    }
}

impl Display for ClrItem {
    /// Formats item as `rule_id; A -> alpha ● beta ; lookahead`.
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let (rule, before_dot, after_dot) = dot_state(&self.rule, self.dot);
        write!(
            f,
            "{:>3}; {} -> {} ● {} ; {}",
            self.rule_id,
            rule,
            before_dot,
            after_dot,
            self.lookahead.as_ref().as_str()
        )
    }
}

/// Returns special end-of-input terminal symbol.
pub(crate) fn get_last_symbol() -> Arc<Symbol> {
    terms!("$END")
}

/// Creates a stable comparison key for an item set.
fn item_set_key(items: &ItemSet) -> ItemSetKey {
    let mut key = items
        .iter()
        .map(|item| {
            (
                item.rule_id,
                item.dot,
                item.lookahead.is_terminal(),
                item.lookahead.as_ref().as_str().to_string(),
            )
        })
        .collect::<Vec<_>>();
    key.sort_unstable();
    key
}

#[inline]
/// Collects grammar rules and constructs a symbol-to-rule index map.
pub(crate) fn setup(
    parser_frontend: Arc<GrammarRuntime>,
    start: Arc<Symbol>,
) -> (Vec<Arc<Rule>>, SymbolMap) {
    let mut rules = parser_frontend.get_parser().get_all_expansion().to_vec();

    let mut mapped: SymbolMap = HashMap::new();

    for (index, rule) in rules.iter().enumerate() {
        mapped
            .entry(rule.origin.clone())
            .or_default()
            .push((index, rule.clone()));
    }

    let augmented_grammar = Arc::new(Rule::new(
        non_terms!("gamma"),
        vec![start],
        Arc::new(RuleMeta::default()),
        0,
    ));
    rules.push(augmented_grammar);
    (rules, mapped)
}

/// Canonical LR parser with precomputed ACTION and GOTO tables.
pub struct ClrParser {
    parser_frontend: Arc<GrammarRuntime>,
    #[allow(dead_code)]
    parser_conf: Arc<ParserConfig>,
    pub(crate) rules: Vec<Arc<Rule>>,
    pub(crate) mapped: SymbolMap,
    pub(crate) first: First,
    action: Action,
    goto: GoTo,
    state_symbol: StateSymbol,
}

impl ClrParser {
    /// Creates a CLR parser and builds canonical items plus ACTION/GOTO tables.
    pub(crate) fn new(parser_frontend: Arc<GrammarRuntime>, parser_conf: Arc<ParserConfig>) -> ClrParser {
        let (rules, mapped) = setup(parser_frontend.clone(), non_terms!(parser_conf.start));

        let first = first_set(&rules);

        #[cfg(feature = "debug")]
        if parser_conf.debug {
            debug_clr_rules(&rules);
            debug_first_set(&first);
        }

        let mut clr = ClrParser {
            parser_frontend,
            parser_conf,
            rules,
            mapped,
            first,
            action: HashMap::new(),
            goto: HashMap::new(),
            state_symbol: HashMap::new(),
        };
        let (canonical_items, transitions) = canonical_items(&mut clr);

        #[cfg(feature = "debug")]
        if clr.parser_conf.debug {
            debug_canonical_and_transtion_sets(&canonical_items, &transitions);
        }

        let (action, goto, state_symbol) =
            clr.build_action_and_goto_table(&canonical_items, &transitions);

        #[cfg(feature = "debug")]
        if clr.parser_conf.debug {
            println!("\nState Symbol Mapping");
            println!("====================");

            let _len = state_symbol.len();

            for i in 0.._len {
                let _state_symbols = state_symbol.get(&i).unwrap();
                println!(
                    "\t{} -> {:?}",
                    i,
                    _state_symbols
                        .iter()
                        .map(|sym| sym.as_str())
                        .collect::<Vec<_>>()
                        .join(", ")
                );
            }

            let action_table = "Action Table";
            println!("\n{}", action_table);
            println!("{}", "=".repeat(action_table.len()));

            let max_symbol_len = |symbols: &mut dyn Iterator<Item = &Arc<Symbol>>| {
                let mut max_len = 0;
                for symbol in symbols {
                    max_len = max_len.max(symbol.get_value().len());
                }
                max_len
            };

            let mut _action = action
                .iter()
                .map(|((index, symbol), v)| (index, symbol.clone(), v.clone()))
                .collect::<Vec<_>>();
            _action.sort_unstable_by(|a, b| a.0.cmp(b.0));

            let _symbol_max_len = max_symbol_len(&mut _action.iter().map(|(_, symbol, _)| symbol));

            _action.iter().for_each(|(index, symbol, v)| {
                let _symbol_value = symbol.get_value();
                println!(
                    "\t{} | {}{}-> {:?}",
                    index,
                    symbol.get_value(),
                    " ".repeat(_symbol_max_len + 2 - _symbol_value.len()),
                    v
                );
            });

            let goto_table = "Goto Table";
            println!("\n{}", goto_table);
            println!("{}", "-".repeat(goto_table.len()));

            let mut _goto = goto
                .iter()
                .map(|((index, symbol), next_index)| (index, symbol.clone(), next_index))
                .collect::<Vec<_>>();
            _goto.sort_unstable_by(|a, b| a.0.cmp(b.0));

            let _goto_max_len = max_symbol_len(&mut _goto.iter().map(|(_, symbol, _)| symbol));

            _goto.iter().for_each(|(index, symbol, next_index)| {
                let _symbol_value = symbol.get_value();
                println!(
                    "\t{} | {}{}-> {}",
                    index,
                    _symbol_value,
                    " ".repeat(_goto_max_len + 2 - _symbol_value.len()),
                    next_index
                );
            });
        }
        clr.action = action;
        clr.goto = goto;
        clr.state_symbol = state_symbol;

        clr
    }

    /// Returns ordered rule list used by parser tables.
    fn get_rules(&self) -> &Vec<Arc<Rule>> {
        &self.rules
    }

    #[inline]
    /// Returns FIRST set for a symbol.
    fn get_first(&self, seq: &Arc<Symbol>) -> Option<&HashSet<Arc<Symbol>>> {
        self.first.get(seq)
    }

    #[inline]
    /// Builds ACTION and GOTO tables from canonical items and transitions.
    fn build_action_and_goto_table(
        &self,
        canonical_items: &VecItemSet,
        transition: &GoTo,
    ) -> (Action, GoTo, StateSymbol) {
        let mut action: Action = HashMap::new();
        let mut goto: GoTo = HashMap::new();
        let mut state_symbol: HashMap<usize, HashSet<Arc<Symbol>>> = HashMap::new();

        for (index, item) in canonical_items.iter().enumerate() {
            for it in item.iter() {
                if it.is_complete() {
                    if it.rule.origin == non_terms!("gamma") {
                        action
                            .entry((index, get_last_symbol()))
                            .or_default()
                            .insert(ParseAction::Accepted);
                        state_symbol
                            .entry(index)
                            .or_default()
                            .insert(get_last_symbol());
                    } else {
                        action
                            .entry((index, it.lookahead.clone()))
                            .or_default()
                            .insert(ParseAction::Reduce(it.rule_id));

                        state_symbol
                            .entry(index)
                            .or_default()
                            .insert(it.lookahead.clone());
                    }
                } else if let Some(next_symbol) = it.next_symbol()
                    && let Some(transition_index) = transition.get(&(index, next_symbol.clone()))
                {
                    if next_symbol.is_terminal() {
                        action
                            .entry((index, next_symbol.clone()))
                            .or_default()
                            .insert(ParseAction::Shift(*transition_index));
                        state_symbol
                            .entry(index)
                            .or_default()
                            .insert(next_symbol.clone());
                    } else {
                        goto.insert((index, next_symbol.clone()), *transition_index);
                    }
                }
            }
        }
        (action, goto, state_symbol)
    }

    /// Resolves a parser action from a possible conflict set using priorities.
    fn get_next_action<'a>(
        &self,
        lr_table: &'a IndexSet<ParseAction>,
    ) -> Result<&'a ParseAction, SwiftletError> {
        if lr_table.len() == 1 {
            return Ok(lr_table.first().unwrap());
        }
        let mut best_action = None;
        let mut best_priority = 0usize;

        for action in lr_table.iter() {
            let priority = match action {
                ParseAction::Reduce(n) => {
                    self.rules.get(*n).map(|rule| rule.rule_option.priority())
                }
                ParseAction::Accepted => self.rules.first().map(|rule| rule.rule_option.priority()),
                ParseAction::Shift(_) => None,
            };

            let Some(priority) = priority else {
                let conflict = lr_table
                    .iter()
                    .map(|x| x.name())
                    .collect::<Vec<String>>()
                    .join("-");

                return Err(ParseError::Conflict {
                    lr_table: lr_table.clone(),
                    conflict,
                }
                .into());
            };

            for other in lr_table.iter() {
                if std::ptr::eq(action, other) {
                    continue;
                }

                let other_priority = match other {
                    ParseAction::Reduce(n) => {
                        self.rules.get(*n).map(|rule| rule.rule_option.priority())
                    }
                    ParseAction::Accepted => {
                        self.rules.first().map(|rule| rule.rule_option.priority())
                    }
                    ParseAction::Shift(_) => None,
                };

                if other_priority == Some(priority) {
                    let conflict = lr_table
                        .iter()
                        .map(|x| x.name())
                        .collect::<Vec<String>>()
                        .join("-");

                    return Err(ParseError::Conflict {
                        lr_table: lr_table.clone(),
                        conflict,
                    }
                    .into());
                }
            }

            if best_action.is_none() || priority > best_priority {
                best_action = Some(action);
                best_priority = priority;
            }
        }

        if let Some(best_action) = best_action {
            Ok(best_action)
        } else {
            let conflict = lr_table
                .iter()
                .map(|x| x.name())
                .collect::<Vec<String>>()
                .join("-");

            Err(ParseError::Conflict {
                lr_table: lr_table.clone(),
                conflict,
            }
            .into())
        }
    }

    #[inline]
    /// Executes shift action and fetches next lookahead token.
    fn shift_action(
        &self,
        pos: usize,
        stack_states: &mut Vec<usize>,
        stack_symbols: &mut Vec<Ast>,
        lookahead: &TokenMatch,
        tokenizer: &mut Tokenizer,
    ) -> Result<TokenMatch, SwiftletError> {
        stack_states.push(pos);
        stack_symbols.push(Ast::Token(lookahead.token.clone()));

        match self.get_lookahead(tokenizer, pos) {
            Ok(next_lookahead) => match next_lookahead {
                Some(next_lookahead) => Ok(next_lookahead),
                None => Err(LexerError::State(pos.to_string()).into()),
            },
            Err(_) => {
                let token = Arc::new(Token::new(
                    Arc::<str>::from(get_last_symbol().as_ref().as_str()),
                    0,
                    get_last_symbol().as_ref().as_str().len(),
                    0,
                    get_last_symbol(),
                ));
                Ok(TokenMatch {
                    token,
                    next_start: 0,
                    next_line: 0,
                })
            }
        }
    }

    /// Executes reduce action and performs goto transition.
    fn reduce_action(
        &self,
        pos: usize,
        stack_states: &mut Vec<usize>,
        stack_symbols: &mut Vec<Ast>,
    ) -> Result<bool, SwiftletError> {
        let rule = self.rules.get(pos).unwrap();

        let mut children = Vec::with_capacity(rule.expansion.len());
        for _ in 0..rule.expansion.len() {
            stack_states.pop();
            let ast = stack_symbols.pop().unwrap();
            let is_flattened = ast.is_hidden();
            if is_flattened {
                match ast {
                    Ast::Tree(_, child) => children.extend(child.into_iter().rev()),
                    Ast::Token(_) => continue,
                }
            } else {
                children.push(ast);
            }
        }

        if rule.rule_option.is_expand() && children.len() == 1 {
            stack_symbols.push(children.pop().unwrap());
        } else if children.len() == 1
            && let Some(Ast::Tree(name, _)) = children.first()
            && let Some(alias_rule) = rule.rule_option.alias_rule()
            && alias_rule.contains(name)
        {
            stack_symbols.push(children.pop().unwrap());
        } else {
            children.reverse();
            stack_symbols.push(Ast::Tree(
                rule.origin.as_ref().as_str().to_string(),
                children,
            ));
        }

        if let Some(index) = stack_states.last()
            && let Some(goto_state) = self.goto.get(&(*index, rule.origin.clone()))
        {
            stack_states.push(*goto_state);
        } else {
            return Err(ParseError::Transition(rule.origin.clone()).into());
        }
        Ok(true)
    }

    fn get_lookahead(
        &self,
        tokenizer: &mut Tokenizer,
        state: usize,
    ) -> Result<Option<TokenMatch>, SwiftletError> {
        #[cfg(feature = "debug")]
        if self.parser_conf.debug {
            println!();
            println!("state: {}", state);
        }
        let symbols = self.state_symbol.get(&state).unwrap();
        #[cfg(feature = "debug")]
        if self.parser_conf.debug {
            println!("symbols: {:?}", symbols);
        }
        let mut terminal_defs = symbols
            .iter()
            .filter_map(|symbol| tokenizer.get_terminal_def(symbol).cloned())
            .collect::<Vec<_>>();
        terminal_defs.sort_by(|a, b| {
            b.priority
                .cmp(&a.priority)
                .then(b.max_width.cmp(&a.max_width))
        });
        #[cfg(feature = "debug")]
        if self.parser_conf.debug {
            println!("terminal_def: ");
            for td in terminal_defs.iter() {
                println!("\t{:?}", td);
            }
        }

        for terminal_def in terminal_defs {
            let sym = terminal_def.get_name();
            match tokenizer.peek_token_with_next_symbol(&sym) {
                Ok(lookahead) => {
                    if let Some(lookahead) = lookahead {
                        #[cfg(feature = "debug")]
                        if self.parser_conf.debug {
                            println!("lookahead: {:?}", lookahead);
                        }
                        tokenizer.commit_token_match(&lookahead);
                        return Ok(Some(lookahead));
                    }
                }
                Err(err) => {
                    return Err(err);
                }
            }
        }

        Ok(Some(TokenMatch {
            token: Arc::new(Token::new("", 0, 0, 0, get_last_symbol())),
            next_start: 0,
            next_line: 0,
        }))
    }
}

impl ParserBackend for ClrParser {
    /// Returns parser frontend.
    fn get_parser_frontend(&self) -> Arc<GrammarRuntime> {
        self.parser_frontend.clone()
    }

    fn parse(&self, tokenizer: &mut Tokenizer) -> Result<Ast, SwiftletError> {
        let mut stack_states = vec![0usize];
        let mut stack_symbols = Vec::new();
        let mut lookahead = match self.get_lookahead(tokenizer, 0) {
            Ok(lookahead) => match lookahead {
                Some(lookahead) => lookahead,
                None => return Err(LexerError::State("0".to_string()).into()),
            },
            Err(err) => {
                return Err(err);
            }
        };

        loop {
            let state = *stack_states.last().unwrap();
            if let Some(lr_table) = self.action.get(&(state, lookahead.token.terminal.clone())) {
                #[cfg(feature = "debug")]
                if self.parser_conf.debug {
                    println!("\nstate: {:?} | lookahead: {:?}", state, lookahead);
                    println!("lr_table: {:?}", lr_table);
                }
                // Check SR & RR conflict
                match self.get_next_action(lr_table) {
                    Ok(action) => match action {
                        ParseAction::Accepted => break,
                        ParseAction::Shift(pos) => {
                            lookahead = self.shift_action(
                                *pos,
                                &mut stack_states,
                                &mut stack_symbols,
                                &lookahead,
                                tokenizer,
                            )?;
                        }
                        ParseAction::Reduce(pos) => {
                            self.reduce_action(*pos, &mut stack_states, &mut stack_symbols)?;
                        }
                    },
                    Err(message) => {
                        return Err(message);
                    }
                }
            } else {
                return Err(ParseError::RuleNotFound(lookahead.token.word().to_string()).into());
            }
        }
        if let Some(ast) = stack_symbols.pop() {
            return Ok(ast);
        }
        Err(ParseError::FailedToParse(tokenizer.get_text().to_string()).into())
    }
}

/// Computes closure for an item set and collects next transition symbols.
pub(crate) fn closure(
    lr_parser: &ClrParser,
    it_item: impl Iterator<Item = Arc<ClrItem>>,
) -> (ItemSet, SymbolSet) {
    let mut next_symbols: SymbolSet = IndexSet::new();
    let mut items: ItemSet = HashSet::new();
    let mut worklist = Vec::new();

    for item in it_item {
        if items.insert(item.clone()) {
            worklist.push(item);
        }
    }

    while let Some(item) = worklist.pop() {
        if item.is_complete() {
            continue;
        }

        let next_symbol = item.next_symbol().unwrap();
        next_symbols.insert(next_symbol.clone());

        if !next_symbol.is_terminal()
            && let Some(productions) = lr_parser.mapped.get(next_symbol)
        {
            if let Some(v) = item.rule.expansion[item.dot + 1..].first() {
                let lookahead = lr_parser.get_first(v).unwrap();
                for (index, rule) in productions.iter() {
                    for lh in lookahead.iter() {
                        let next_item = Arc::new(ClrItem::new(*index, 0, rule.clone(), lh.clone()));
                        if items.insert(next_item.clone()) {
                            worklist.push(next_item);
                        }
                    }
                }
            } else {
                for (index, rule) in productions.iter() {
                    let next_item =
                        Arc::new(ClrItem::new(*index, 0, rule.clone(), item.lookahead.clone()));
                    if items.insert(next_item.clone()) {
                        worklist.push(next_item);
                    }
                }
            }
        }
    }
    (items, next_symbols)
}

/// Expands canonical LR item sets recursively and records transitions.
fn find_canonical_items(
    lr_parser: &mut ClrParser,
    canonical_items: &mut VecItemSet,
    canonical_index: &mut HashMap<ItemSetKey, usize>,
    next_symbols_by_index: &mut Vec<SymbolSet>,
    transitions: &mut GoTo,
) {
    let mut pending = vec![0usize];

    while let Some(item_index) = pending.pop() {
        let item = canonical_items[item_index].clone();
        let list_of_next_symbols = next_symbols_by_index[item_index].clone();

        for symbol in list_of_next_symbols.iter() {
            let moved_items = item
                .iter()
                .filter(|x1| x1.is_next_symbol(symbol))
                .map(|x2| Arc::new(x2.move_dot().unwrap()))
                .collect::<Vec<_>>();
            let (next_canonical_item, next_list_of_next_symbols) =
                closure(lr_parser, moved_items.into_iter());
            if next_canonical_item.is_empty() {
                continue;
            }

            let key = item_set_key(&next_canonical_item);
            let next_item_index = if let Some(existing_index) = canonical_index.get(&key) {
                *existing_index
            } else {
                let next_item_index = canonical_items.len();
                canonical_items.push(next_canonical_item);
                next_symbols_by_index.push(next_list_of_next_symbols);
                canonical_index.insert(key, next_item_index);
                pending.push(next_item_index);
                next_item_index
            };
            transitions.insert((item_index, symbol.clone()), next_item_index);
        }
    }
}

/// Builds canonical collection of LR(1) item sets and transition graph.
pub(crate) fn canonical_items(lr_parser: &mut ClrParser) -> (VecItemSet, GoTo) {
    // Augmented grammar
    let first_items = [Arc::new(ClrItem::new(
        lr_parser.get_rules().len() - 1,
        0,
        lr_parser.get_rules().iter().last().unwrap().clone(),
        get_last_symbol(),
    ))];

    let (first_items, list_of_next_symbols) = closure(lr_parser, first_items.iter().cloned());

    let mut canonical_items: VecItemSet = Vec::from([first_items.clone()]);
    let mut canonical_index = HashMap::from([(item_set_key(&first_items), 0usize)]);
    let mut next_symbols_by_index = vec![list_of_next_symbols];
    let mut transitions: GoTo = HashMap::new();

    find_canonical_items(
        lr_parser,
        &mut canonical_items,
        &mut canonical_index,
        &mut next_symbols_by_index,
        &mut transitions,
    );

    (canonical_items, transitions)
}

/// Computes FIRST sets used during CLR closure expansion.
pub(crate) fn first_set(rules: &[Arc<Rule>]) -> First {
    let mut first: First = rules
        .iter()
        .map(|x| (x.origin.clone(), HashSet::new()))
        .collect();

    let mut added = true;

    while added {
        added = false;
        for rule in rules.iter() {
            let origin = &rule.origin;
            if let Some(e) = rule.expansion.first() {
                if e.is_terminal() {
                    if first.get_mut(origin).unwrap().insert(e.clone()) {
                        added = true;
                    }
                    let val = first.entry(e.clone()).or_default();
                    val.insert(e.clone());
                } else if !first[e].is_empty() {
                    // In the block, first v_iter calculate before val to avoid mutatable and non-mutatable error.
                    let v_iter: HashSet<Arc<Symbol>> =
                        first.get(e).unwrap().iter().cloned().collect();

                    let val = first.get_mut(origin).unwrap();
                    for v in v_iter {
                        if val.insert(v) {
                            added = true;
                        }
                    }
                }
            }
            for t in rule.expansion[1..].iter().filter(|x| x.is_terminal()) {
                first.entry(t.clone()).or_default().insert(t.clone());
            }
        }
    }
    first
}

// ---------------- CLR Debug ---------------- //
/// Prints numbered rules for debug tracing.
#[cfg(feature = "debug")]
#[inline]
fn debug_clr_rules(rules: &[Arc<Rule>]) {
    println!("\nList of Rules in BNF format.");
    println!("============================");

    for (index, rule) in rules.iter().enumerate() {
        println!("\t{:>2}; {}", index, rule);
    }
    println!();
}

#[cfg(feature = "debug")]
#[inline]
/// Prints FIRST sets for debug tracing.
fn debug_first_set(first: &First) {
    println!("First Set");
    println!("=========");
    for (k, v) in first.iter() {
        println!(
            "\t{:?} => {:?}",
            k.as_ref().as_str(),
            v.iter()
                .map(|x| { x.as_ref().as_str().to_string() })
                .collect::<Vec<String>>()
        );
    }
    println!();
}

/// Prints canonical items and transitions for debug tracing.
#[cfg(feature = "debug")]
#[inline]
fn debug_canonical_and_transtion_sets(canonical_items: &VecItemSet, transitions: &GoTo) {
    println!("Canonical Items:");
    println!("================");
    for (index, items) in canonical_items.iter().enumerate() {
        println!("I-{}:", index);
        for item in items.iter() {
            println!("\t{}", item);
        }
    }
    println!();

    println!("Transitions:");
    println!("============");

    let mut trans = transitions
        .iter()
        .map(|((k1, k2), v)| (k1, k2, v))
        .collect::<Vec<_>>();
    trans.sort_by(|a, b| a.0.cmp(b.0));

    for (index, sym, transition) in trans.iter() {
        println!(
            "\t(I-{:<2}, {}): I-{}",
            index,
            sym.as_ref().as_str(),
            transition
        );
    }
}
// ----------------------------------------------- //