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use bit_set::BitSet;
use fxhash::FxBuildHasher;
use hashbrown::HashMap;
use crate::atn::INVALID_ALT;
use crate::atn_config::ATNConfig;
use crate::atn_config_set::MutableATNConfigSet;
use crate::atn_state::ATNStateRef;
use crate::prediction_context::{NoopHasherBuilder, PredictionContextRef};
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<'ephemeral>(
ephemerals: &'ephemeral bumpalo::Bump,
mode: PredictionMode,
configs: &MutableATNConfigSet<'ephemeral>,
) -> bool {
// if all_configs_in_rule_stop_states(configs) {
// return true checked outside
// }
if mode == PredictionMode::SLL && configs.has_semantic_context() {
let mut dup = MutableATNConfigSet::new(ephemerals, true);
configs.get_items().for_each(|it| {
let c = ATNConfig::new(it.get_state(), it.get_alt(), it.get_context())
.with_semantic_context(&SemanticContext::NONE);
dup.add(c);
});
let altsets = get_conflicting_alt_subsets(ephemerals, &dup);
has_conflicting_alt_set(altsets.values())
&& !has_state_associated_with_one_alt(ephemerals, &dup)
} else {
let altsets = get_conflicting_alt_subsets(ephemerals, configs);
has_conflicting_alt_set(altsets.values())
&& !has_state_associated_with_one_alt(ephemerals, configs)
}
}
//fn all_configs_in_rule_stop_states(configs: &ATNConfigSet) -> bool {
// for co
//}
pub(crate) fn resolves_to_just_one_viable_alt<'a>(
altsets: impl Iterator<Item = &'a BitSet>,
) -> i32 {
get_single_viable_alt(altsets)
}
pub(crate) fn all_subsets_conflict<'a>(altsets: impl Iterator<Item = &'a BitSet>) -> bool {
!has_non_conflicting_alt_set(altsets)
}
pub(crate) fn all_subsets_equal<'a>(mut altsets: impl Iterator<Item = &'a BitSet>) -> bool {
let first = altsets.next();
altsets.all(|it| it == first.unwrap())
}
fn has_non_conflicting_alt_set<'a>(mut altsets: impl Iterator<Item = &'a BitSet>) -> bool {
altsets.any(|it| it.len() == 1)
}
fn has_conflicting_alt_set<'a>(altsets: impl Iterator<Item = &'a BitSet>) -> bool {
for alts in altsets {
if alts.len() > 1 {
return true;
}
}
false
}
//fn get_unique_alt(altsets: &[BitSet]) -> int { unimplemented!() }
//
pub(crate) fn get_alts(altsets: impl Iterator<Item = BitSet>) -> BitSet {
altsets.fold(BitSet::new(), |mut acc, it| {
acc.extend(&it);
acc
})
}
#[derive(Eq, PartialEq)]
pub(crate) struct KeyWrapper<'a> {
state: ATNStateRef,
context: PredictionContextRef<'a>,
}
impl<'a> std::hash::Hash for KeyWrapper<'a> {
fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
let ptr = self.state.as_usize() as u64;
state.write_u64(ptr ^ (self.context.hash_code() as u64));
}
}
pub(crate) fn get_conflicting_alt_subsets<'ephemeral>(
ephemerals: &'ephemeral bumpalo::Bump,
configs: &MutableATNConfigSet<'ephemeral>,
) -> HashMap<KeyWrapper<'ephemeral>, BitSet, NoopHasherBuilder, &'ephemeral bumpalo::Bump> {
let mut configs_to_alts: HashMap<KeyWrapper<'ephemeral>, BitSet, _, _> =
HashMap::with_capacity_and_hasher_in(configs.length(), NoopHasherBuilder {}, ephemerals);
for c in configs.get_items() {
let alts = configs_to_alts
.entry(KeyWrapper {
state: c.get_state(),
context: c.get_context().unwrap(),
})
.or_default();
alts.insert(c.get_alt() as usize);
}
configs_to_alts
}
fn has_state_associated_with_one_alt(
ephemerals: &bumpalo::Bump,
configs: &MutableATNConfigSet,
) -> bool {
let mut lookup =
HashMap::with_capacity_and_hasher_in(configs.length(), FxBuildHasher::new(), ephemerals);
for c in configs.get_items() {
let state = c.get_state();
if let Some((alt, more_than_one)) = lookup.get_mut(&state) {
if *alt != c.get_alt() {
*more_than_one = true;
}
} else {
lookup.insert(state, (c.get_alt(), false));
}
}
lookup
.into_values()
.any(|(_, more_than_one)| !more_than_one)
}
pub(crate) fn get_single_viable_alt<'a>(altsets: impl Iterator<Item = &'a BitSet>) -> i32 {
let mut min_alt = INVALID_ALT as usize;
for alt in altsets {
let new_alt = alt.iter().next().unwrap();
if min_alt == INVALID_ALT as usize {
min_alt = new_alt;
} else if min_alt != new_alt {
return INVALID_ALT;
}
}
min_alt as i32
}