com.github.jknack.handlebars.internal.HbsParserFactory Maven / Gradle / Ivy

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Logic-less and semantic templates with Java
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/**
 * Copyright (c) 2012-2015 Edgar Espina
 *
 * This file is part of Handlebars.java.
 *
 * 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
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.github.jknack.handlebars.internal;

import java.io.IOException;
import java.util.Optional;

import org.antlr.v4.runtime.ANTLRErrorListener;
import org.antlr.v4.runtime.CharStream;
import org.antlr.v4.runtime.CharStreams;
import org.antlr.v4.runtime.CommonToken;
import org.antlr.v4.runtime.CommonTokenStream;
import org.antlr.v4.runtime.LexerNoViableAltException;
import org.antlr.v4.runtime.Recognizer;
import org.antlr.v4.runtime.atn.PredictionMode;
import org.antlr.v4.runtime.misc.Interval;
import org.antlr.v4.runtime.tree.ParseTree;
import org.antlr.v4.runtime.tree.ParseTreeWalker;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.github.jknack.handlebars.Handlebars;
import com.github.jknack.handlebars.Parser;
import com.github.jknack.handlebars.ParserFactory;
import com.github.jknack.handlebars.Template;
import com.github.jknack.handlebars.io.TemplateSource;

/**
 * The default {@link ParserFactory}.
 *
 * @author edgar.espina
 * @since 0.10.0
 */
public class HbsParserFactory implements ParserFactory {

  /**
   * The logging system.
   */
  private final Logger logger = LoggerFactory.getLogger(getClass());

  /**
   * Creates a new {@link Parser}.
   *
   * @param handlebars The parser owner.
   * @param startDelimiter The start delimiter.
   * @param endDelimiter The end delimiter.
   * @return A new {@link Parser}.
   */
  @Override
  public Parser create(final Handlebars handlebars,
      final String startDelimiter,
      final String endDelimiter) {
    return new Parser() {

      @Override
      public Template parse(final TemplateSource source) throws IOException {
        logger.debug("About to parse: {}", source);
        String sourceName = source.filename();
        final ANTLRErrorListener errorReporter = new HbsErrorReporter(sourceName);

        // 1. Lexer
        String content = Optional.ofNullable(source.content(handlebars.getCharset()))
            .orElse("");
        final HbsLexer lexer = newLexer(CharStreams.fromString(content, sourceName), startDelimiter, endDelimiter);
        configure(lexer, errorReporter);

        // 2. Parser
        final HbsParser parser = newParser(lexer);
        configure(parser, errorReporter);

        logger.debug("Building AST");
        // 3. Parse
        ParseTree tree = parser.template();

        // remove unnecessary spaces and new lines?
        if (handlebars.prettyPrint()) {
          logger.debug("Applying Mustache spec");
          new ParseTreeWalker().walk(new MustacheSpec(), tree);
        }
        
        if (lexer.whiteSpaceControl) {
          logger.debug("Applying white spaces control");
          new ParseTreeWalker().walk(new WhiteSpaceControl((CommonTokenStream)parser.getTokenStream()), tree);
        }

        /**
         * Build the AST.
         */
        TemplateBuilder builder = new TemplateBuilder(handlebars, source) {
          @Override
          protected void reportError(final CommonToken offendingToken, final int line,
              final int column,
              final String message) {
            errorReporter.syntaxError(parser, offendingToken, line, column, message, null);
          }
        };
        logger.debug("Creating templates");
        Template template = builder.visit(tree);
        return template;
      }

    };
  }

  /**
   * Creates a new {@link HbsLexer}.
   *
   * @param stream The input stream.
   * @param startDelimiter The start delimiter.
   * @param endDelimiter The end delimiter.
   * @return A new {@link HbsLexer}.
   */
  private HbsLexer newLexer(final CharStream stream, final String startDelimiter,
      final String endDelimiter) {
    return new HbsLexer(stream, startDelimiter, endDelimiter) {

      @Override
      public void notifyListeners(final LexerNoViableAltException e) {
        String text = _input.getText(Interval.of(_tokenStartCharIndex, _input.index()));
        String msg = "found: '" + getErrorDisplay(text) + "'";
        ANTLRErrorListener listener = getErrorListenerDispatch();
        listener
            .syntaxError(this, null, _tokenStartLine, _tokenStartCharPositionInLine, msg, e);
      }

      @Override
      public void recover(final LexerNoViableAltException e) {
        throw new IllegalArgumentException(e);
      }
    };
  }

  /**
   * Creates a new {@link HbsParser}.
   *
   * @param lexer The {@link HbsLexer}.
   * @return A new {@link HbsParser}.
   */
  private HbsParser newParser(final HbsLexer lexer) {
    return new HbsParser(new CommonTokenStream(lexer)) {
      @Override
      void setStart(final String start) {
        lexer.start = start;
      }

      @Override
      void setEnd(final String end) {
        lexer.end = end;
      }
    };
  }

  /**
   * Configure a {@link HbsParser}.
   *
   * @param parser The {@link HbsParser}.
   * @param errorReporter The error reporter.
   */
  @SuppressWarnings("rawtypes")
  private void configure(final HbsParser parser, final ANTLRErrorListener errorReporter) {
    configure((Recognizer) parser, errorReporter);

    parser.setErrorHandler(new HbsErrorStrategy());
    parser.getInterpreter().setPredictionMode(PredictionMode.SLL);
  }

  /**
   * Configure a recognizer with an error reporter.
   *
   * @param recognizer A recognizer.
   * @param errorReporter The error reporter.
   */
  private void configure(final Recognizer recognizer,
      final ANTLRErrorListener errorReporter) {
    recognizer.removeErrorListeners();
    recognizer.addErrorListener(errorReporter);
  }
}