Dave Jarvis' Repositories

/*
 * Copyright 2016 White Magic Software, Ltd.
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  o Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 *  o Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.scrivenvar.processors;

import com.scrivenvar.Services;
import com.scrivenvar.service.Options;
import com.scrivenvar.service.events.Notifier;
import org.renjin.eval.EvalException;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import java.nio.file.Path;
import java.util.Map;

import static com.scrivenvar.Constants.*;
import static com.scrivenvar.Messages.get;
import static com.scrivenvar.decorators.RVariableDecorator.PREFIX;
import static com.scrivenvar.decorators.RVariableDecorator.SUFFIX;
import static com.scrivenvar.processors.text.TextReplacementFactory.replace;
import static java.lang.Math.min;

/**
 * Transforms a document containing R statements into Markdown.
 *
 * @author White Magic Software, Ltd.
 */
public final class InlineRProcessor extends DefinitionProcessor {

  private static final Notifier NOTIFIER = Services.load( Notifier.class );
  private static final Options OPTIONS = Services.load( Options.class );

  // Only one editor is open at a time.
  private static final ScriptEngine ENGINE =
      (new ScriptEngineManager()).getEngineByName( "Renjin" );

  /**
   * Constructs a processor capable of evaluating R statements.
   *
   * @param processor Subsequent link in the processing chain.
   * @param map       Resolved definitions map.
   */
  public InlineRProcessor(
      final Processor<String> processor,
      final Map<String, String> map ) {
    super( processor, map );
    init();
  }

  /**
   * Initialises the R code so that R can find imported libraries.
   */
  private void init() {
    try {
      final Path wd = getWorkingDirectory();
      final String dir = wd.toString().replace( '\\', '/' );
      final Map<String, String> map = getDefinitions();
      map.put( "$application.r.working.directory$", dir );

      final String initScript = getInitScript();

      if( !initScript.isBlank() ) {
        eval( replace( initScript, map ) );
      }
    } catch( final Exception e ) {
      getNotifier().notify( e );
    }
  }

  /**
   * Loads the R init script from the application's persisted preferences.
   *
   * @return A non-null String, possibly empty.
   */
  private String getInitScript() {
    return getOptions().get( PERSIST_R_STARTUP, "" );
  }

  /**
   * Evaluates all R statements in the source document and inserts the
   * calculated value into the generated document.
   *
   * @param text The document text that includes variables that should be
   *             replaced with values when rendered as HTML.
   * @return The generated document with output from all R statements
   * substituted with value returned from their execution.
   */
  @Override
  public String processLink( final String text ) {
    final int length = text.length();
    final int prefixLength = PREFIX.length();

    // Pre-allocate the same amount of space. A calculation is longer to write
    // than its computed value inserted into the text.
    final StringBuilder sb = new StringBuilder( length );

    int prevIndex = 0;
    int currIndex = text.indexOf( PREFIX );

    while( currIndex >= 0 ) {
      // Copy everything up to, but not including, an R statement (`r#).
      sb.append( text, prevIndex, currIndex );

      // Jump to the start of the R statement.
      prevIndex = currIndex + prefixLength;

      // Find the statement ending (`), without indexing past the text boundary.
      currIndex = text.indexOf( SUFFIX, min( currIndex + 1, length ) );

      // Only evalutate inline R statements that have end delimiters.
      if( currIndex > 1 ) {
        // Extract the inline R statement to be evaluated.
        final String r = text.substring( prevIndex, currIndex );

        // Pass the R statement into the R engine for evaluation.
        try {
          final Object result = eval( r );

          // Append the string representation of the result into the text.
          sb.append( result );
        } catch( final Exception e ) {
          // If the string couldn't be parsed using R, append the statement
          // that failed to parse, instead of its evaluated value.
          sb.append( PREFIX ).append( r ).append( SUFFIX );

          // Tell the user that there was a problem.
          getNotifier().notify(
              get( STATUS_PARSE_ERROR, e.getMessage(), currIndex )
          );
        }

        // Retain the R statement's ending position in the text.
        prevIndex = currIndex + 1;
      }

      // Find the start of the next inline R statement.
      currIndex = text.indexOf( PREFIX, min( currIndex + 1, length ) );
    }

    // Copy from the previous index to the end of the string.
    return sb.append( text.substring( min( prevIndex, length ) ) ).toString();
  }

  /**
   * Evaluate an R expression and return the resulting object.
   *
   * @param r The expression to evaluate.
   * @return The object resulting from the evaluation.
   */
  private Object eval( final String r ) throws ScriptException, EvalException {
    return getScriptEngine().eval( r );
  }

  private synchronized ScriptEngine getScriptEngine() {
    return ENGINE;
  }

  private Notifier getNotifier() {
    return NOTIFIER;
  }

  private Options getOptions() {
    return OPTIONS;
  }

  /**
   * This will return the given path if not null, otherwise it will return
   * the path to the user's directory.
   *
   * @return A non-null path.
   */
  private Path getWorkingDirectory() {
    return Path.of( getPreference( PERSIST_R_DIRECTORY, USER_DIRECTORY ) );
  }

  /**
   * Returns the user-defined preference value for the given key.
   *
   * @param key          The key to find in the user's preferences.
   * @param defaultValue The default value to return if no preference is set.
   * @return The value for the preference, or {@code defaultValue} if not found.
   */
  @SuppressWarnings("SameParameterValue")
  private String getPreference( final String key, final String defaultValue ) {
    return OPTIONS.get( key, defaultValue );
  }
}