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use std::collections::HashMap;
use bit_set::BitSet;
use crate::atn::INVALID_ALT;
use crate::atn_config::ATNConfig;
use crate::atn_config_set::ATNConfigSet;
use crate::atn_state::ATNStateRef;
use crate::prediction_context::PredictionContext;
use crate::semantic_context::SemanticContext;
/// This enum defines the prediction modes available in ANTLR 4 along with
/// utility methods for analyzing configuration sets for conflicts and/or
/// ambiguities.
///
/// It is set through `ParserATNSimulator::
#[allow(non_camel_case_types)]
#[derive(Eq, PartialEq, Copy, Clone, Debug)]
pub enum PredictionMode {
/// The SLL(*) prediction mode. This prediction mode ignores the current
/// parser context when making predictions. This is the fastest prediction
/// mode, and provides correct results for many grammars. This prediction
/// mode is more powerful than the prediction mode provided by ANTLR 3, but
/// may result in syntax errors for grammar and input combinations which are
/// not SLL.
///
/// <p>
/// When using this prediction mode, the parser will either return a correct
/// parse tree (i.e. the same parse tree that would be returned with the
/// {@link #LL} prediction mode), or it will report a syntax error. If a
/// syntax error is encountered when using the {@link #SLL} prediction mode,
/// it may be due to either an actual syntax error in the input or indicate
/// that the particular combination of grammar and input requires the more
/// powerful {@link #LL} prediction abilities to complete successfully.</p>
///
/// <p>
/// This prediction mode does not provide any guarantees for prediction
/// behavior for syntactically-incorrect inputs.</p>
///
SLL = 0,
///
/// The LL(*) prediction mode. This prediction mode allows the current parser
/// context to be used for resolving SLL conflicts that occur during
/// prediction. This is the fastest prediction mode that guarantees correct
/// parse results for all combinations of grammars with syntactically correct
/// inputs.
///
/// <p>
/// When using this prediction mode, the parser will make correct decisions
/// for all syntactically-correct grammar and input combinations. However, in
/// cases where the grammar is truly ambiguous this prediction mode might not
/// report a precise answer for <em>exactly which</em> alternatives are
/// ambiguous.</p>
///
/// <p>
/// This prediction mode does not provide any guarantees for prediction
/// behavior for syntactically-incorrect inputs.</p>
///
LL,
///
/// The LL(*) prediction mode with exact ambiguity detection. In addition to
/// the correctness guarantees provided by the {@link #LL} prediction mode,
/// this prediction mode instructs the prediction algorithm to determine the
/// complete and exact set of ambiguous alternatives for every ambiguous
/// decision encountered while parsing.
///
/// <p>
/// This prediction mode may be used for diagnosing ambiguities during
/// grammar development. Due to the performance overhead of calculating sets
/// of ambiguous alternatives, this prediction mode should be avoided when
/// the exact results are not necessary.</p>
///
/// <p>
/// This prediction mode does not provide any guarantees for prediction
/// behavior for syntactically-incorrect inputs.</p>
///
LL_EXACT_AMBIG_DETECTION,
}
impl PredictionMode {
//todo move everything here
}
//
//
pub(crate) fn has_sll_conflict_terminating_prediction(
mode: PredictionMode,
configs: &ATNConfigSet,
) -> bool {
// if all_configs_in_rule_stop_states(configs) {
// return true checked outside
// }
let mut dup = ATNConfigSet::new_base_atnconfig_set(true);
let mut configs = &*configs;
if mode == PredictionMode::SLL {
if configs.has_semantic_context() {
configs.get_items().for_each(|it| {
let c = ATNConfig::new_with_semantic(
it.get_state(),
it.get_alt(),
it.get_context().cloned(),
Box::new(SemanticContext::NONE),
);
dup.add(Box::new(c));
});
configs = &dup;
}
}
let altsets = get_conflicting_alt_subsets(&configs);
let heuristic =
has_conflicting_alt_set(&altsets) && !has_state_associated_with_one_alt(&configs);
return heuristic;
}
//fn all_configs_in_rule_stop_states(configs: &ATNConfigSet) -> bool {
// for co
//}
pub(crate) fn resolves_to_just_one_viable_alt(altsets: &Vec<BitSet>) -> isize {
get_single_viable_alt(altsets)
}
pub(crate) fn all_subsets_conflict(altsets: &Vec<BitSet>) -> bool {
!has_non_conflicting_alt_set(altsets)
}
pub(crate) fn all_subsets_equal(altsets: &Vec<BitSet>) -> bool {
let mut iter = altsets.iter();
let first = iter.next();
iter.all(|it| it == first.unwrap())
}
fn has_non_conflicting_alt_set(altsets: &Vec<BitSet>) -> bool {
altsets.iter().any(|it| it.len() == 1)
}
fn has_conflicting_alt_set(altsets: &Vec<BitSet>) -> bool {
for alts in altsets {
if alts.len() > 1 {
return true;
}
}
false
}
//fn get_unique_alt(altsets: &Vec<BitSet>) -> int { unimplemented!() }
//
pub(crate) fn get_alts(altsets: &Vec<BitSet>) -> BitSet {
altsets.iter().fold(BitSet::new(), |mut acc, it| {
acc.extend(it);
acc
})
}
//
pub(crate) fn get_conflicting_alt_subsets(configs: &ATNConfigSet) -> Vec<BitSet> {
let mut configs_to_alts: HashMap<(ATNStateRef, &PredictionContext), BitSet> = HashMap::new();
for c in configs.get_items() {
let alts = configs_to_alts
.entry((c.get_state(), c.get_context().unwrap()))
.or_default();
alts.insert(c.get_alt() as usize);
}
configs_to_alts.drain().map(|(_, x)| x).collect()
}
fn get_state_to_alt_map(configs: &ATNConfigSet) -> HashMap<ATNStateRef, BitSet> {
let mut m = HashMap::new();
for c in configs.get_items() {
let alts = m.entry(c.get_state()).or_insert(BitSet::new());
alts.insert(c.get_alt() as usize);
}
m
}
fn has_state_associated_with_one_alt(configs: &ATNConfigSet) -> bool {
let x = get_state_to_alt_map(configs);
for alts in x.values() {
if alts.len() == 1 {
return true;
}
}
false
}
pub(crate) fn get_single_viable_alt(altsets: &Vec<BitSet>) -> isize {
let mut viable_alts = BitSet::new();
let mut min_alt = INVALID_ALT as usize;
for alt in altsets {
min_alt = alt.iter().next().unwrap();
viable_alts.insert(min_alt);
if viable_alts.len() > 1 {
return INVALID_ALT;
}
}
min_alt as isize
}