tajo-common/src/main/java/org/apache/tajo/type/TypeStringEncoder.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.tajo.type;

import com.google.common.base.Function;
import com.google.common.collect.ImmutableList;
import org.apache.tajo.Assert;
import org.apache.tajo.common.TajoDataTypes;
import org.apache.tajo.exception.TajoInternalError;
import org.apache.tajo.exception.UnsupportedException;
import org.apache.tajo.schema.Field;
import org.apache.tajo.schema.IdentifierUtil;
import org.apache.tajo.schema.QualifiedIdentifier;
import org.apache.tajo.util.StringUtils;

import javax.annotation.Nullable;
import java.util.List;
import java.util.Stack;

import static org.apache.tajo.schema.IdentifierPolicy.DefaultPolicy;

/**
 * This class enables to serialize a type into a string representation and vice versa.
 */
public class TypeStringEncoder {

  /**
   * Encode a type into a string representation
   * @param type A type
   * @return A type string representation
   */
  public static String encode(Type type) {
    StringBuilder sb = new StringBuilder(type.kind().name());

    if (type.isTypeParameterized()) {
      sb.append("<");
      sb.append(StringUtils.join(type.getTypeParameters(), ",", new Function<Type, String>() {
        @Override
        public String apply(@Nullable Type type) {
          return TypeStringEncoder.encode(type);
        }
      }));
      sb.append(">");
    }

    // Assume all parameter values are integers.
    if (type.isValueParameterized()) {
      sb.append("(");
      sb.append(StringUtils.join(type.getValueParameters(), ","));
      sb.append(")");
    }

    if (type.isStruct()) {
      Record record = (Record) type;
      sb.append("[");
      sb.append(StringUtils.join(record.fields(), ",", new Function<Field, String>() {
        @Override
        public String apply(@Nullable Field field) {
          return serializeField(field);
        }
      }));
      sb.append("]");
    }

    return sb.toString();
  }

  /**
   * Make a string from a field
   * @param field A field
   * @return String representation for a field
   */
  static String serializeField(Field field) {
    return field.name().raw(DefaultPolicy()) + " " + encode(field.type());
  }

  /**
   * Decode a string representation to a Type.
   * @param signature Type string representation
   * @return Type
   */
  public static Type decode(String signature) {

    // termination condition in this recursion
    if (!(signature.contains("<") || signature.contains("(") || signature.contains("["))) {
      return createType(signature,
          ImmutableList.<Type>of(),
          ImmutableList.<Integer>of(),
          ImmutableList.<Field>of());
    }

    final Stack<Character> stack = new Stack<>();
    final Stack<Integer> spanStack = new Stack<>();
    String baseType = null;
    for (int i = 0; i < signature.length(); i++) {
      char c = signature.charAt(i);

      if (c == '<') {
        if (stack.isEmpty()) {
          Assert.assertCondition(baseType == null, "Expected baseName to be null");
          baseType = signature.substring(0, i);
        }
        stack.push('<');
        spanStack.push(i + 1);

      } else if (c == '>') {
        Assert.assertCondition(stack.pop() == '<', "Bad signature: '%s'", signature);
        int paramStartIdx = spanStack.pop();

        if (stack.isEmpty()) { // ensure outermost parameters
          return createType(baseType,
              parseList(signature.substring(paramStartIdx, i), new Function<String, Type>() {
                @Override
                public Type apply(@Nullable String s) {
                  return decode(s);
                }
              }),
              ImmutableList.<Integer>of(),
              ImmutableList.<Field>of());
        }

      } else if (c == '[') {
        if (stack.isEmpty()) {
          Assert.assertCondition(baseType == null, "Expected baseName to be null");
          baseType = signature.substring(0, i);
        }

        stack.push('[');
        spanStack.push(i + 1);

      } else if (c == ']') {
        Assert.assertCondition(stack.pop() == '[', "Bad signature: '%s'", signature);

        int paramStartIdx = spanStack.pop();
        if (stack.isEmpty()) { // ensure outermost parameters
          return createType(baseType,
              ImmutableList.<Type>of(),
              ImmutableList.<Integer>of(),
              parseList(signature.substring(paramStartIdx, i), new Function<String, Field>() {
                @Override
                public Field apply(@Nullable String s) {
                  return parseField(s);
                }
              }));
        }

      } else if (c == '(') {
        if (stack.isEmpty()) {
          Assert.assertCondition(baseType == null, "Expected baseName to be null");
          baseType = signature.substring(0, i);
        }
        stack.push('(');
        spanStack.push(i + 1);

      } else if (c == ')') {
        Assert.assertCondition(stack.pop() == '(', "Bad signature: '%s'", signature);
        int paramStartIdx = spanStack.pop();

        if (stack.isEmpty()) { // ensure outermost parameters
          return createType(baseType,
              ImmutableList.<Type>of(),
              parseList(signature.substring(paramStartIdx, i), new Function<String, Integer>() {
                @Override
                public Integer apply(@Nullable String s) {
                  return parseValue(s);
                }
              }),
              ImmutableList.<Field>of());
        }
      }
    }

    return null;
  }

  public static int parseValue(String literal) {
    try {
      return Integer.parseInt(literal);
    } catch (NumberFormatException e) {
      throw new TajoInternalError(e);
    }
  }

  /**
   * Parse a string delimited by comma into a list of object instances depending on <pre>itemParser</pre>.
   * @param str String delimited by comma
   * @param itemParser A function to transform a string to an object.
   * @param <T> Type to be transformed from a string
   * @return List of object instances
   */
  static <T> List<T> parseList(String str, Function<String, T> itemParser) {
    if (!str.contains(",")) { // if just one item
      return ImmutableList.of(itemParser.apply(str));
    }

    final ImmutableList.Builder<T> fields = ImmutableList.builder();
    final Stack<Character> stack = new Stack<>();
    int paramStartIdx = 0;
    for (int i = 0; i < str.length(); i++) {
      char c = str.charAt(i);

      if (c == '<' || c == '[' || c == '(') {
        stack.push(c);
      } else if (c == '>') {
        Assert.assertCondition(stack.pop() == '<', "Bad signature: '%s'", str);
      } else if (c == ']') {
        Assert.assertCondition(stack.pop() == '[', "Bad signature: '%s'", str);
      } else if (c == ')') {
        Assert.assertCondition(stack.pop() == '(', "Bad signature: '%s'", str);
      } else if (c == ',') {
        if (stack.isEmpty()) { // ensure outermost type parameters
          fields.add(itemParser.apply(str.substring(paramStartIdx, i)));
          paramStartIdx = i + 1;
        }
      }
    }

    Assert.assertCondition(stack.empty(), "Bad signature: '%s'", str);
    if (paramStartIdx < str.length()) {
      fields.add(itemParser.apply(str.substring(paramStartIdx, str.length())));
    }

    return fields.build();
  }

  /**
   * Make a field from a string representation
   * @param str String
   * @return Field
   */
  static Field parseField(String str) {
    // A field consists of an identifier and a type, and they are delimited by space.
    if (!str.contains(" ")) {
      Assert.assertCondition(false, "Bad field signature: '%s'", str);
    }

    // Stack to track the nested bracket depth
    Stack<Character> stack = new Stack<>();
    int paramStartIdx = 0;
    for (int i = 0; i < str.length(); i++) {
      char c = str.charAt(i);

      if (c == '<' || c == '[' || c == '(') {
        stack.push(c);
      } else if (c == '>') { // for validation
        Assert.assertCondition(stack.pop() == '<', "Bad field signature: '%s'", str);
      } else if (c == ']') { // for validation
        Assert.assertCondition(stack.pop() == '[', "Bad field signature: '%s'", str);
      } else if (c == ')') { // for validation
        Assert.assertCondition(stack.pop() == '(', "Bad field signature: '%s'", str);

      } else if (c == ' ') {
        if (stack.isEmpty()) { // ensure outermost type parameters
          QualifiedIdentifier identifier =
              IdentifierUtil.makeIdentifier(str.substring(paramStartIdx, i), DefaultPolicy());
          String typePart = str.substring(i + 1, str.length());
          return new Field(identifier, decode(typePart));
        }
      }
    }

    return null;
  }

  public static Type createType(String baseTypeStr,
                                List<Type> typeParams,
                                List<Integer> valueParams,
                                List<Field> fieldParams) {
    final TajoDataTypes.Type baseType;

    try {
      baseType = TajoDataTypes.Type.valueOf(baseTypeStr);
    } catch (Throwable t) {
      throw new TajoInternalError(new UnsupportedException(baseTypeStr));
    }

    return TypeFactory.create(baseType, typeParams, valueParams, fieldParams);
  }

}