dotlr/src/index.ts

An LR(1) parser generator and visualizer created for educational purposes.

import {
  Grammar as _Grammar,
  Parser as _Parser,
  WasmParserError,
} from "./pkg/dotlr";
import {
  ActionTable,
  Automaton,
  FirstTable,
  FollowTable,
  GoToTable,
  GrammarError,
  LALR1ParserOfGrammar,
  LR1ParserOfGrammar,
  ParserError,
  ParsingError,
  ParsingTables,
  Rule,
  Spanned,
  Token,
  Trace,
  Tree,
} from "./types";
import { Err, Ok } from "ts-results-es";

export class Grammar<
  T extends string = string,
  NT extends string = string,
  R extends string = string,
> {
  grammar: _Grammar;
  private cache = {
    symbols: null as NT[] | null,
    constant_tokens: null as T[] | null,
    start_symbol: null as NT | null,
    regex_tokens: null as Map<R, string> | null,
    productions: null as Rule<Token<T, R>>[] | null,
    stringify: null as string | null,
  };

  private constructor(grammar: _Grammar) {
    this.grammar = grammar;
  }

  static parse<
    T extends string = string,
    NT extends string = string,
    R extends string = string,
  >(grammar: string) {
    try {
      const res = _Grammar.parse_wasm(grammar);
      return Ok(new Grammar<T, NT, R>(res));
    } catch (e) {
      return Err(e as GrammarError);
    }
  }

  getSymbols() {
    return (this.cache.symbols ??= this.grammar.symbols_wasm() as NT[]);
  }

  getConstantTokens() {
    return (this.cache.constant_tokens ??=
      this.grammar.constant_tokens_wasm() as T[]);
  }

  getStartSymbol() {
    return (this.cache.start_symbol ??= this.grammar.start_symbol_wasm() as NT);
  }

  getProductions() {
    return (this.cache.productions ??= this.grammar.rules_wasm() as Rule<
      Token<T, R>
    >[]);
  }

  getRegexTokens() {
    return (this.cache.regex_tokens ??=
      this.grammar.regular_expressions_wasm() as Map<R, string>);
  }

  stringify() {
    return (this.cache.stringify ??= this.grammar.to_string_wasm() as string);
  }

  clone() {
    return new Grammar<T, NT, R>(this.grammar.clone_wasm());
  }
}

export class Parser<
  T extends string = string,
  NT extends string = string,
  R extends string = string,
> {
  private parser: _Parser;
  private cache = {
    action_table: null as ActionTable<Token<T, R>> | null,
    goto_table: null as GoToTable<NT> | null,
    parsing_tables: null as ParsingTables<NT, Token<T, R>> | null,
    automaton: null as Automaton<Token<T, R>> | null,
    first_table: null as FirstTable<Token<T, R>> | null,
    follow_table: null as FollowTable<Token<T, R>> | null,
  };

  constructor(parser: _Parser) {
    this.parser = parser;
  }

  parse(input: string) {
    try {
      return Ok(this.parser.parse_wasm(input) as Tree<NT, Token<T, R>>);
    } catch (e) {
      return Err(e as ParsingError);
    }
  }

  getActionTable() {
    return (this.cache.action_table ??=
      this.parser.action_table_wasm() as ActionTable<Token<T, R>>);
  }

  getGotoTable() {
    return (this.cache.goto_table ??=
      this.parser.goto_table_wasm() as GoToTable<NT>);
  }

  getParseTables() {
    return (this.cache.parsing_tables ??=
      this.parser.parsing_tables_wasm() as ParsingTables<NT, Token<T, R>>);
  }

  getAutomaton() {
    return (this.cache.automaton ??= this.parser.automaton_wasm() as Automaton<
      Token<T, R>
    >);
  }

  getFirstTable() {
    return (this.cache.first_table ??=
      this.parser.first_table_wasm() as FirstTable<Token<T, R>>);
  }

  getFollowTable() {
    return (this.cache.follow_table ??=
      this.parser.follow_table_wasm() as FollowTable<Token<T, R>>);
  }

  tokenize(input: string) {
    try {
      const tokens = this.parser.tokenize_wasm(input) as [
        Spanned<Token<T, R>>,
        string,
      ][];
      return Ok(
        tokens.map(([token, slice]) => ({
          token,
          slice,
        })),
      );
    } catch (e) {
      return Err(e as ParsingError);
    }
  }

  trace(input: string) {
    try {
      const [trace, tree] = this.parser.trace_wasm(input) as [
        Trace<Tree<NT, Token<T, R>>>,
        Tree<NT, Token<T, R>>,
      ];
      return Ok({
        trace,
        tree,
      });
    } catch (e) {
      return Err(e as ParsingError);
    }
  }
}

// this function tries to recover the serialized parser into the actual parser
function mapParserError(error: WasmParserError, kind: "lalr1" | "lr1") {
  const serialized = error.serialize() as ParserError;
  if (serialized.type === "Conflict") {
    serialized.value.parser =
      kind === "lalr1"
        ? // @ts-expect-error private constructor
          new LALR1Parser(error.into_conflict_parser())
        : // @ts-expect-error private constructor
          new LR1Parser(error.into_conflict_parser());
  }
  return serialized as ParserError;
}

export class LR1Parser<
  T extends string = string,
  NT extends string = string,
  R extends string = string,
> extends Parser<T, NT, R> {
  private constructor(parser: _Parser) {
    super(parser);
  }

  /**
   * Consumes a grammar and returns a parser, the grammar is consumed and the ownership is transferred to the parser
   */
  static fromGrammar<G extends Grammar>(grammar: G) {
    try {
      return Ok(
        new LR1Parser(
          _Parser.new_wasm(grammar.grammar),
        ) as LR1ParserOfGrammar<G>,
      );
    } catch (e) {
      return Err(
        mapParserError(e as WasmParserError, "lr1") as ParserError<
          LR1ParserOfGrammar<G>
        >,
      );
    }
  }
}

export class LALR1Parser<
  T extends string = string,
  NT extends string = string,
  R extends string = string,
> extends Parser<T, NT, R> {
  private constructor(parser: _Parser) {
    super(parser);
  }

  /**
   * Consumes a grammar and returns a parser, the grammar is consumed and the ownership is transferred to the parser
   */
  static fromGrammar<G extends Grammar>(grammar: G) {
    try {
      return Ok(
        new LALR1Parser(
          _Parser.new_wasm(grammar.grammar),
        ) as LALR1ParserOfGrammar<G>,
      );
    } catch (e) {
      return Err(
        mapParserError(e as WasmParserError, "lalr1") as ParserError<
          LALR1ParserOfGrammar<G>
        >,
      );
    }
  }
}