tree-sitter/src/compiler/build_tables/perform.cpp

#include "./perform.h"
#include "item.h"
#include "item_set_closure.h"
#include "item_set_transitions.h"
#include "tree_sitter/compiler.h"

#include "stream_methods.h"

namespace tree_sitter {
    using std::pair;
    using std::string;
    using std::map;
    using std::make_shared;
    using rules::Symbol;
    using rules::CharacterSet;

    namespace build_tables {
        static int NOT_FOUND = -1;
        static Symbol START("start", true);
        static Symbol END_OF_INPUT("end", true);

        class TableBuilder {
            const Grammar grammar;
            const Grammar lex_grammar;
            map<const ParseItemSet, size_t> parse_state_indices;
            map<const LexItemSet, size_t> lex_state_indices;
            ParseTable parse_table;
            LexTable lex_table;
            
            long parse_state_index_for_item_set(const ParseItemSet &item_set) const {
                auto entry = parse_state_indices.find(item_set);
                return (entry == parse_state_indices.end()) ? NOT_FOUND : entry->second;
            }

            long lex_state_index_for_item_set(const LexItemSet &item_set) const {
                auto entry = lex_state_indices.find(item_set);
                return (entry == lex_state_indices.end()) ? NOT_FOUND : entry->second;
            }
            
            void add_shift_actions(const ParseItemSet &item_set, size_t state_index) {
                for (auto transition : sym_transitions(item_set, grammar)) {
                    Symbol symbol = transition.first;
                    ParseItemSet item_set = transition.second;
                    size_t new_state_index = add_parse_state(item_set);
                    parse_table.add_action(state_index, symbol, ParseAction::Shift(new_state_index));
                }
            }
            
            void add_advance_actions(const LexItemSet &item_set, size_t state_index) {
                for (auto transition : char_transitions(item_set, grammar)) {
                    CharacterSet rule = transition.first;
                    LexItemSet item_set = transition.second;
                    size_t new_state_index = add_lex_state(item_set);
                    lex_table.add_action(state_index, rule, LexAction::Advance(new_state_index));
                }
            }
            
            void add_accept_token_actions(const LexItemSet &item_set, size_t state_index) {
                for (LexItem item : item_set) {
                    if (item.is_done()) {
                        lex_table.add_default_action(state_index, LexAction::Accept(item.lhs));
                    }
                }
            }
            
            void add_reduce_actions(const ParseItemSet &item_set, size_t state_index) {
                for (ParseItem item : item_set) {
                    if (item.is_done()) {
                        ParseAction action = (item.lhs == START) ?
                            ParseAction::Accept() :
                            ParseAction::Reduce(item.lhs, item.consumed_symbols);
                        parse_table.add_action(state_index, item.lookahead_sym, action);
                    }
                }
            }
            
            void assign_lex_state(size_t state_index) {
                ParseState &state = parse_table.states[state_index];
                LexItemSet item_set;
                for (auto &symbol : state.expected_inputs()) {
                    if (symbol == END_OF_INPUT)
                        item_set.insert(LexItem(symbol, make_shared<CharacterSet>(std::set<rules::CharacterRange>{ '\0' })));
                    if (lex_grammar.has_definition(symbol))
                        item_set.insert(LexItem(symbol, lex_grammar.rule(symbol)));
                }

                state.lex_state_index = add_lex_state(item_set);
            }
            
            size_t add_lex_state(const LexItemSet &item_set) {
                auto state_index = lex_state_index_for_item_set(item_set);
                if (state_index == NOT_FOUND) {
                    state_index = lex_table.add_state();
                    lex_state_indices[item_set] = state_index;
                    add_advance_actions(item_set, state_index);
                    add_accept_token_actions(item_set, state_index);
                }
                return state_index;
            }
            
            size_t add_parse_state(const ParseItemSet &item_set) {
                auto state_index = parse_state_index_for_item_set(item_set);
                if (state_index == NOT_FOUND) {
                    state_index = parse_table.add_state();
                    parse_state_indices[item_set] = state_index;

                    add_shift_actions(item_set, state_index);
                    add_reduce_actions(item_set, state_index);
                    assign_lex_state(state_index);
                }
                return state_index;
            }
            
            // TODO - remove
            void dump_item_sets() {
                std::vector<const ParseItemSet *> item_sets(parse_state_indices.size());
                for (auto &pair : parse_state_indices)
                    item_sets[pair.second] = &pair.first;
                
                for (int i = 0; i < item_sets.size(); i++) {
                    std:cout << "\n\n" << i;
                    for (auto &item : *item_sets[i]) {
                        cout << "\n" << item.lhs;
                        cout << "\n  " << item.rule;
                        cout << "\n  " << item.lookahead_sym.name;
                    }
                }
            }
            
        public:
            
            TableBuilder(const Grammar &grammar, const Grammar &lex_grammar) :
                grammar(grammar),
                lex_grammar(lex_grammar) {};

            pair<ParseTable, LexTable> build() {
                auto item = ParseItem(START, make_shared<Symbol>(grammar.start_rule_name), {}, END_OF_INPUT);
                ParseItemSet item_set = item_set_closure(ParseItemSet({ item }), grammar);
                add_parse_state(item_set);
                return pair<ParseTable, LexTable>(parse_table, lex_table);
            }
        };
        
        pair<ParseTable, LexTable> perform(const Grammar &grammar, const Grammar &lex_grammar) {
            return TableBuilder(grammar, lex_grammar).build();
        }
    }
}