CollectionParser.java

/**
 * MVEL 2.0
 * Copyright (C) 2007 The Codehaus
 * Mike Brock, Dhanji Prasanna, John Graham, Mark Proctor
 *
 * 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 org.mvel2.util;

import org.mvel2.CompileException;
import org.mvel2.DataConversion;
import org.mvel2.ParserContext;
import org.mvel2.compiler.ExecutableStatement;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import static org.mvel2.util.ParseTools.*;
import static org.mvel2.util.ReflectionUtil.isAssignableFrom;

/**
 * This is the inline collection sub-parser.  It produces a skeleton model of the collection which is in turn translated
 * into a sequenced AST to produce the collection efficiently at runtime, and passed off to one of the JIT's if
 * configured.
 *
 * @author Christopher Brock
 */
public class CollectionParser {
  private char[] property;

  private int cursor;
  private int start;
  private int end;

  private int type;

  public static final int LIST = 0;
  public static final int ARRAY = 1;
  public static final int MAP = 2;

  private Class colType;
  private ParserContext pCtx;

  private static final Object[] EMPTY_ARRAY = new Object[0];

  public CollectionParser() {
  }

  public CollectionParser(int type) {
    this.type = type;
  }

  public Object parseCollection(char[] property, int start, int offset, boolean subcompile, ParserContext pCtx) {
    this.property = property;
    this.pCtx = pCtx;
    this.end = start + offset;

    while (start < end && isWhitespace(property[start])) {
      start++;
    }
    this.start = this.cursor = start;

    return parseCollection(subcompile);
  }

  public Object parseCollection(char[] property, int start, int offset, boolean subcompile, Class colType, ParserContext pCtx) {
    if (colType != null) this.colType = getBaseComponentType(colType);
    this.property = property;

    this.end = start + offset;

    while (start < end && isWhitespace(property[start])) {
      start++;
    }

    this.start = this.cursor = start;

    this.pCtx = pCtx;

    return parseCollection(subcompile);
  }

  private Object parseCollection(boolean subcompile) {
    if (end - start == 0) {
      if (type == LIST) return new ArrayList();
      else return EMPTY_ARRAY;
    }

    Map<Object, Object> map = null;
    List<Object> list = null;

    int st = start;

    if (type != -1) {
      switch (type) {
        case ARRAY:
        case LIST:
          list = new ArrayList<Object>();
          break;
        case MAP:
          map = new HashMap<Object, Object>();
          break;
      }
    }

    Object curr = null;
    int newType = -1;


    for (; cursor < end; cursor++) {
      switch (property[cursor]) {
        case '{':
          if (newType == -1) {
            newType = ARRAY;
          }

        case '[':
          if (cursor > start && isIdentifierPart(property[cursor - 1])) continue;

          if (newType == -1) {
            newType = LIST;
          }

          /**
           * Sub-parse nested collections.
           */
          Object o = new CollectionParser(newType).parseCollection(property, (st = cursor) + 1,
              (cursor = balancedCapture(property, st, end, property[st])) - st - 1, subcompile, colType, pCtx);

          if (type == MAP) {
            map.put(curr, o);
          }
          else {
            list.add(curr = o);
          }

          cursor = skipWhitespace(property, ++cursor);

          if ((st = cursor) < end && property[cursor] == ',') {
            st = cursor + 1;
          }
          else if (cursor < end) {
            if (ParseTools.opLookup(property[cursor]) == -1) {
              throw new CompileException("unterminated collection element", property, cursor);
            }
          }

          continue;

        case '(':
          cursor = balancedCapture(property, cursor, end, '(');

          break;

        case '\"':
        case '\'':
          cursor = balancedCapture(property, cursor, end, property[cursor]);

          break;

        case ',':
          if (type != MAP) {
            list.add(new String(property, st, cursor - st).trim());
          }
          else {
            map.put(curr, createStringTrimmed(property, st, cursor - st));
          }

          if (subcompile) {
            subCompile(st, cursor - st);
          }

          st = cursor + 1;

          break;

        case ':':
          if (type != MAP) {
            map = new HashMap<Object, Object>();
            type = MAP;
          }
          curr = createStringTrimmed(property, st, cursor - st);

          if (subcompile) {
            subCompile(st, cursor - st);
          }

          st = cursor + 1;
          break;

        case '.':
          cursor++;
          cursor = skipWhitespace(property, cursor);
          if (cursor != end && property[cursor] == '{') {
            cursor = balancedCapture(property, cursor, '{');
          }
          break;
      }
    }

    if (st < end && isWhitespace(property[st])) {
      st = skipWhitespace(property, st);
    }

    if (st < end) {
      if (cursor < (end - 1)) cursor++;

      if (type == MAP) {
        map.put(curr, createStringTrimmed(property, st, cursor - st));
      }
      else {
        if (cursor < end) cursor++;
        list.add(createStringTrimmed(property, st, cursor - st));
      }

      if (subcompile) subCompile(st, cursor - st);
    }

    switch (type) {
      case MAP:
        return map;
      case ARRAY:
        return list.toArray();
      default:
        return list;
    }
  }

  private void subCompile(int start, int offset) {
    if (colType == null) {
      subCompileExpression(property, start, offset, pCtx);
    }
    else {
      Class r = ((ExecutableStatement) subCompileExpression(property, start, offset, pCtx)).getKnownEgressType();
      if (r != null && !isAssignableFrom(colType, r) && (isStrongType() || !DataConversion.canConvert(r, colType))) {
        throw new CompileException("expected type: " + colType.getName() + "; but found: " + r.getName(), property, cursor);
      }
    }
  }

  private boolean isStrongType() {
    return pCtx != null && pCtx.isStrongTyping();
  }

  public int getCursor() {
    return cursor;
  }
}