/*
 * 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
 *
 *     https://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.avro.io.parsing;

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

import org.apache.avro.Schema;
import org.apache.avro.Schema.Field;

The class that generates validating grammar.
/**
 * The class that generates validating grammar.
 */
public class ValidatingGrammarGenerator {
  
Returns the non-terminal that is the start symbol for the grammar for the
given schema sc.
/**
   * Returns the non-terminal that is the start symbol for the grammar for the
   * given schema <tt>sc</tt>.
   */
  public Symbol generate(Schema schema) {
    return Symbol.root(generate(schema, new HashMap<>()));
  }

  
Returns the non-terminal that is the start symbol for the grammar for the
given schema sc. If there is already an entry for the given schema
in the given map seen then that entry is returned. Otherwise a new
symbol is generated and an entry is inserted into the map.
Params:
sc –   The schema for which the start symbol is required
seen – A map of schema to symbol mapping done so far.
Returns:
The start symbol for the schema/**
   * Returns the non-terminal that is the start symbol for the grammar for the
   * given schema <tt>sc</tt>. If there is already an entry for the given schema
   * in the given map <tt>seen</tt> then that entry is returned. Otherwise a new
   * symbol is generated and an entry is inserted into the map.
   * 
   * @param sc   The schema for which the start symbol is required
   * @param seen A map of schema to symbol mapping done so far.
   * @return The start symbol for the schema
   */
  public Symbol generate(Schema sc, Map<LitS, Symbol> seen) {
    switch (sc.getType()) {
    case NULL:
      return Symbol.NULL;
    case BOOLEAN:
      return Symbol.BOOLEAN;
    case INT:
      return Symbol.INT;
    case LONG:
      return Symbol.LONG;
    case FLOAT:
      return Symbol.FLOAT;
    case DOUBLE:
      return Symbol.DOUBLE;
    case STRING:
      return Symbol.STRING;
    case BYTES:
      return Symbol.BYTES;
    case FIXED:
      return Symbol.seq(Symbol.intCheckAction(sc.getFixedSize()), Symbol.FIXED);
    case ENUM:
      return Symbol.seq(Symbol.intCheckAction(sc.getEnumSymbols().size()), Symbol.ENUM);
    case ARRAY:
      return Symbol.seq(Symbol.repeat(Symbol.ARRAY_END, generate(sc.getElementType(), seen)), Symbol.ARRAY_START);
    case MAP:
      return Symbol.seq(Symbol.repeat(Symbol.MAP_END, generate(sc.getValueType(), seen), Symbol.STRING),
          Symbol.MAP_START);
    case RECORD: {
      LitS wsc = new LitS(sc);
      Symbol rresult = seen.get(wsc);
      if (rresult == null) {
        Symbol[] production = new Symbol[sc.getFields().size()];

        /**
         * We construct a symbol without filling the array. Please see
         * {@link Symbol#production} for the reason.
         */
        rresult = Symbol.seq(production);
        seen.put(wsc, rresult);

        int i = production.length;
        for (Field f : sc.getFields()) {
          production[--i] = generate(f.schema(), seen);
        }
      }
      return rresult;
    }
    case UNION:
      List<Schema> subs = sc.getTypes();
      Symbol[] symbols = new Symbol[subs.size()];
      String[] labels = new String[subs.size()];

      int i = 0;
      for (Schema b : sc.getTypes()) {
        symbols[i] = generate(b, seen);
        labels[i] = b.getFullName();
        i++;
      }
      return Symbol.seq(Symbol.alt(symbols, labels), Symbol.UNION);

    default:
      throw new RuntimeException("Unexpected schema type");
    }
  }

  
A wrapper around Schema that does "==" equality. /** A wrapper around Schema that does "==" equality. */
  static class LitS {
    public final Schema actual;

    public LitS(Schema actual) {
      this.actual = actual;
    }

    
Two LitS are equal if and only if their underlying schema is the same (not
merely equal).
/**
     * Two LitS are equal if and only if their underlying schema is the same (not
     * merely equal).
     */
    @Override
    public boolean equals(Object o) {
      if (!(o instanceof LitS))
        return false;
      return actual.equals(((LitS) o).actual);
    }

    @Override
    public int hashCode() {
      return actual.hashCode();
    }
  }
}