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 * Copyright (C) jparsec.org                                                *
 * ------------------------------------------------------------------------- *
 * Licensed under the Apache License, Version 2.0 (the "License");           *
 * you may not use this file except in compliance with the License.          *
 * You may obtain a copy of the License at                                   *
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 * http://www.apache.org/licenses/LICENSE-2.0                                *
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 * Unless required by applicable law or agreed to in writing, software       *
 * distributed under the License is distributed on an "AS IS" BASIS,         *
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 * See the License for the specific language governing permissions and       *
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package org.jparsec.examples.sql.parser;

import static java.util.Arrays.asList;

import org.jparsec.Parser;
import org.jparsec.Parsers;
import org.jparsec.Scanners;
import org.jparsec.Terminals;
import org.jparsec.examples.sql.ast.QualifiedName;
import org.jparsec.*;

/**
 * Lexers and terminal level parsers for SQL.
 * 
 * @author Ben Yu
 */
final class TerminalParser {
  
  private static final String[] OPERATORS = {
    "+", "-", "*", "/", "%", ">", "<", "=", ">=", "<=", "<>", ".", ",", "(", ")", "[", "]"
  };
  
  private static final String[] KEYWORDS = {
    "select", "distinct", "from", "as", "where", "group", "by", "having", "order", "asc", "desc", 
    "and", "or", "not", "in", "exists", "between", "is", "null", "like", "escape",
    "inner", "outer", "left", "right", "full", "cross", "join", "on",
    "union", "all", "case", "when", "then", "else", "end"
  };
  
  private static final Terminals TERMS =
      Terminals.operators(OPERATORS).words(Scanners.IDENTIFIER).caseInsensitiveKeywords(asList(KEYWORDS)).build();
  
  private static final Parser TOKENIZER = Parsers.or(
      Terminals.DecimalLiteral.TOKENIZER, Terminals.StringLiteral.SINGLE_QUOTE_TOKENIZER,
      TERMS.tokenizer());
  
  static final Parser NUMBER = Terminals.DecimalLiteral.PARSER;
  static final Parser STRING = Terminals.StringLiteral.PARSER;
  
  static final Parser NAME =
      Parsers.between(term("["), Terminals.fragment(Tokens.Tag.RESERVED, Tokens.Tag.IDENTIFIER), term("]"))
      .or(Terminals.Identifier.PARSER);
  
  static final Parser QUALIFIED_NAME =
      NAME.sepBy1(term(".")).map(QualifiedName::new);
  
  static  T parse(Parser parser, String source) {
    return parser.from(TOKENIZER, Scanners.SQL_DELIMITER).parse(source);
  }
  
  public static Parser term(String term) {
    return TERMS.token(term);
  }
  
  public static Parser phrase(String phrase) {
    return TERMS.phrase(phrase.split("\\s"));
  }
}