/*
 * 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.rocketmq.connect.transforms;

import com.google.common.base.Strings;
import io.openmessaging.KeyValue;
import io.openmessaging.connector.api.data.ConnectRecord;
import io.openmessaging.connector.api.data.Field;
import io.openmessaging.connector.api.data.Schema;
import io.openmessaging.connector.api.data.SchemaAndValue;
import io.openmessaging.connector.api.data.SchemaBuilder;
import io.openmessaging.connector.api.data.Struct;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 * change case
 * @param <R>
 */
public abstract class ChangeCase<R extends ConnectRecord> extends BaseTransformation<R> {
  private static final Logger log = LoggerFactory.getLogger(ChangeCase.class);

  class State {
    public final Map<String, String> columnMapping;
    public final Schema schema;
    State(Map<String, String> columnMapping, Schema schema) {
      this.columnMapping = columnMapping;
      this.schema = schema;
    }
  }

  Map<Schema, State> schemaState = new HashMap<>();
  private ChangeCaseConfig config;
  @Override
  public void start(KeyValue config) {
    this.config = new ChangeCaseConfig(config);
  }

  @Override
  protected SchemaAndValue processStruct(R record, Schema inputSchema, Struct input) {
    // state
    final State state = this.schemaState.computeIfAbsent(inputSchema, schema -> {
      final SchemaBuilder builder = SchemaBuilder.struct();
      if (!Strings.isNullOrEmpty(schema.getName())) {
        builder.name(schema.getName());
      }
      if (schema.isOptional()) {
        builder.optional();
      }
      final Map<String, String> columnMapping = new LinkedHashMap<>();
      for (Field field : schema.getFields()) {
        final String newFieldName = this.config.from.to(this.config.to, field.getName());
        log.trace("processStruct() - Mapped '{}' to '{}'", field.getName(), newFieldName);
        columnMapping.put(field.getName(), newFieldName);
        builder.field(newFieldName, field.getSchema());
      }
      return new State(columnMapping, builder.build());
    });


    final Struct outputStruct = new Struct(state.schema);
    for (Map.Entry<String, String> kvp : state.columnMapping.entrySet()) {
      final Object value = input.get(kvp.getKey());
      outputStruct.put(kvp.getValue(), value);
    }
    return new SchemaAndValue(state.schema, outputStruct);
  }

  /**
   * transform key
   */
  public static class Key extends ChangeCase<ConnectRecord> {
    @Override
    public ConnectRecord doTransform(ConnectRecord r) {
      final SchemaAndValue transformed = process(r, r.getKeySchema(), r.getKey());
      ConnectRecord record = new ConnectRecord(
              r.getPosition().getPartition(),
              r.getPosition().getOffset(),
              r.getTimestamp(),
              transformed.schema(),
              transformed.value(),
              r.getSchema(),
              r.getData()
      );
      record.setExtensions(r.getExtensions());
      return record;
    }
  }


  /**
   * transform value
   */
  public static class Value extends ChangeCase<ConnectRecord> {
    @Override
    public ConnectRecord doTransform(ConnectRecord r) {
      final SchemaAndValue transformed = process(r, r.getSchema(), r.getData());
      ConnectRecord record = new ConnectRecord(
              r.getPosition().getPartition(),
              r.getPosition().getOffset(),
              r.getTimestamp(),
              r.getKeySchema(),
              r.getKey(),
              transformed.schema(),
              transformed.value()
      );
      record.setExtensions(r.getExtensions());
      return record;
    }
  }
}