/*
 * 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.streams.plugins.pig;

import org.apache.streams.util.schema.FieldType;
import org.apache.streams.util.schema.FieldUtil;
import org.apache.streams.util.schema.FileUtil;
import org.apache.streams.util.schema.Schema;
import org.apache.streams.util.schema.SchemaStore;
import org.apache.streams.util.schema.SchemaStoreImpl;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.node.ObjectNode;
import org.apache.commons.lang3.StringUtils;
import org.jsonschema2pojo.util.URLUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.net.URL;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Objects;

import static org.apache.streams.util.schema.FileUtil.dropExtension;
import static org.apache.streams.util.schema.FileUtil.dropSourcePathPrefix;
import static org.apache.streams.util.schema.FileUtil.swapExtension;
import static org.apache.streams.util.schema.FileUtil.writeFile;

/**
 * Embed within your own java code
 *
 * <p/>
 * StreamsPigGenerationConfig config = new StreamsPigGenerationConfig();
 * config.setSourceDirectory("src/main/jsonschema");
 * config.setTargetDirectory("target/generated-resources");
 * StreamsPigResourceGenerator generator = new StreamsPigResourceGenerator(config);
 * generator.run();
 *
 */
public class StreamsPigResourceGenerator implements Runnable {

  private static final Logger LOGGER = LoggerFactory.getLogger(StreamsPigResourceGenerator.class);

  private static final String LS = System.getProperty("line.separator");

  private StreamsPigGenerationConfig config;

  private SchemaStore schemaStore = new SchemaStoreImpl();

  private int currentDepth = 0;

  /**
   * Run from CLI without Maven
   *
   * <p/>
   * java -jar streams-plugin-pig-jar-with-dependencies.jar StreamsPigResourceGenerator src/main/jsonschema target/generated-resources
   *
   * @param args [sourceDirectory, targetDirectory]
   * */
  public static void main(String[] args) {
    StreamsPigGenerationConfig config = new StreamsPigGenerationConfig();

    String sourceDirectory = "src/main/jsonschema";
    String targetDirectory = "target/generated-resources/pig-cli";

    if ( args.length > 0 ) {
      sourceDirectory = args[0];
    }
    if ( args.length > 1 ) {
      targetDirectory = args[1];
    }

    config.setSourceDirectory(sourceDirectory);
    config.setTargetDirectory(targetDirectory);

    StreamsPigResourceGenerator streamsPigResourceGenerator = new StreamsPigResourceGenerator(config);
    streamsPigResourceGenerator.run();

  }

  public StreamsPigResourceGenerator(StreamsPigGenerationConfig config) {
    this.config = config;
  }

  @Override
  public void run() {

    Objects.requireNonNull(config);

    generate(config);

  }

  /**
   * run generate using supplied StreamsPigGenerationConfig.
   * @param config StreamsPigGenerationConfig
   */
  public void generate(StreamsPigGenerationConfig config) {

    List<File> sourceFiles = new LinkedList<>();

    for (Iterator<URL> sources = config.getSource(); sources.hasNext(); ) {
      URL source = sources.next();
      sourceFiles.add(URLUtil.getFileFromURL(source));
    }

    LOGGER.info("Seeded with {} source paths:", sourceFiles.size());

    FileUtil.resolveRecursive(config, sourceFiles);

    LOGGER.info("Resolved {} schema files:", sourceFiles.size());

    for (File item : sourceFiles) {
      schemaStore.create(item.toURI());
    }

    LOGGER.info("Identified {} objects:", schemaStore.getSize());

    for (Iterator<Schema> schemaIterator = schemaStore.getSchemaIterator(); schemaIterator.hasNext(); ) {
      Schema schema = schemaIterator.next();
      currentDepth = 0;
      if (schema.getUri().getScheme().equals("file")) {
        String inputFile = schema.getUri().getPath();
        String resourcePath = dropSourcePathPrefix(inputFile, config.getSourceDirectory());
        for (String sourcePath : config.getSourcePaths()) {
          resourcePath = dropSourcePathPrefix(resourcePath, sourcePath);
        }
        String outputFile = config.getTargetDirectory() + "/" + swapExtension(resourcePath, "json", "pig");

        LOGGER.info("Processing {}:", resourcePath);

        String resourceId = schemaSymbol(schema);

        String resourceContent = generateResource(schema, resourceId);

        writeFile(outputFile, resourceContent);

        LOGGER.info("Wrote {}:", outputFile);
      }
    }
  }

  /**
   * generateResource String from schema and resourceId.
   * @param schema Schema
   * @param resourceId String
   * @return mapping
   */
  public String generateResource(Schema schema, String resourceId) {
    StringBuilder resourceBuilder = new StringBuilder();
    resourceBuilder.append(pigEscape(resourceId));
    resourceBuilder.append(" = ");
    resourceBuilder.append("LOAD '' USING JsonLoader('");
    resourceBuilder = appendRootObject(resourceBuilder, schema, resourceId, ':');
    resourceBuilder.append("');");
    return resourceBuilder.toString();
  }

  protected StringBuilder appendRootObject(StringBuilder builder, Schema schema, String resourceId, Character separator) {
    ObjectNode propertiesNode = schemaStore.resolveProperties(schema, null, resourceId);
    if (propertiesNode != null && propertiesNode.isObject() && propertiesNode.size() > 0) {
      builder = appendPropertiesNode(builder, schema, propertiesNode, separator);
    }
    return builder;
  }

  private StringBuilder appendPropertiesNode(StringBuilder builder, Schema schema, ObjectNode propertiesNode, Character seperator) {
    Objects.requireNonNull(builder);
    Objects.requireNonNull(propertiesNode);
    Iterator<Map.Entry<String, JsonNode>> fields = propertiesNode.fields();
    List<String> fieldStrings = new ArrayList<>();
    for ( ; fields.hasNext(); ) {
      Map.Entry<String, JsonNode> field = fields.next();
      String fieldId = field.getKey();
      if ( !config.getExclusions().contains(fieldId) && field.getValue().isObject()) {
        ObjectNode fieldNode = (ObjectNode) field.getValue();
        FieldType fieldType = FieldUtil.determineFieldType(fieldNode);
        if (fieldType != null ) {
          switch (fieldType) {
            case ARRAY:
              ObjectNode resolvedItems = schemaStore.resolveItems(schema, fieldNode, fieldId);
              if ( resolvedItems != null && currentDepth <= config.getMaxDepth()) {
                StringBuilder arrayItemsBuilder = appendArrayItems(new StringBuilder(), schema, fieldId, resolvedItems, seperator);
                if (StringUtils.isNotBlank(arrayItemsBuilder.toString())) {
                  fieldStrings.add(arrayItemsBuilder.toString());
                }
              }
              break;
            case OBJECT:
              ObjectNode childProperties = schemaStore.resolveProperties(schema, fieldNode, fieldId);
              if ( currentDepth < config.getMaxDepth()) {
                StringBuilder structFieldBuilder = appendStructField(new StringBuilder(), schema, fieldId, childProperties, seperator);
                if (StringUtils.isNotBlank(structFieldBuilder.toString())) {
                  fieldStrings.add(structFieldBuilder.toString());
                }
              }
              break;
            default:
              StringBuilder valueFieldBuilder = appendValueField(new StringBuilder(), schema, fieldId, fieldType, seperator);
              if (StringUtils.isNotBlank(valueFieldBuilder.toString())) {
                fieldStrings.add(valueFieldBuilder.toString());
              }
          }
        }
      }
    }
    builder.append(String.join(", ", fieldStrings));
    Objects.requireNonNull(builder);
    return builder;
  }

  private StringBuilder appendValueField(StringBuilder builder, Schema schema, String fieldId, FieldType fieldType, Character seperator) {
    // safe to append nothing
    Objects.requireNonNull(builder);
    builder.append(pigEscape(fieldId));
    builder.append(seperator);
    builder.append(pigType(fieldType));
    return builder;
  }

  protected StringBuilder appendArrayItems(StringBuilder builder, Schema schema, String fieldId, ObjectNode itemsNode, Character seperator) {
    // not safe to append nothing
    Objects.requireNonNull(builder);
    if ( itemsNode == null ) {
      return builder;
    }
    FieldType itemType = FieldUtil.determineFieldType(itemsNode);
    try {
      switch ( itemType ) {
        case OBJECT:
          builder = appendArrayObject(builder, schema, fieldId, itemsNode, seperator);
          break;
        case ARRAY:
          ObjectNode subArrayItems = (ObjectNode) itemsNode.get("items");
          builder = appendArrayItems(builder, schema, fieldId, subArrayItems, seperator);
          break;
        default:
          builder = appendArrayField(builder, schema, fieldId, itemType, seperator);
      }
    } catch (Exception ex) {
      LOGGER.warn("No item type resolvable for {}", fieldId);
    }

    Objects.requireNonNull(builder);
    return builder;
  }

  private StringBuilder appendArrayField(StringBuilder builder, Schema schema, String fieldId, FieldType fieldType, Character seperator) {
    // safe to append nothing
    Objects.requireNonNull(builder);
    Objects.requireNonNull(fieldId);
    builder.append("{t: (");
    builder.append(pigEscape(fieldId));
    builder.append(seperator);
    builder.append(pigType(fieldType));
    builder.append(")}");
    Objects.requireNonNull(builder);
    return builder;
  }

  private StringBuilder appendArrayObject(StringBuilder builder, Schema schema, String fieldId, ObjectNode fieldNode, Character seperator) {
    // safe to append nothing
    Objects.requireNonNull(builder);
    Objects.requireNonNull(fieldId);
    Objects.requireNonNull(fieldNode);
    ObjectNode propertiesNode = schemaStore.resolveProperties(schema, fieldNode, fieldId);
    if ( propertiesNode.size() > 0 ) {
      builder.append("{t: (");
      builder = appendStructField(builder, schema, "", propertiesNode, ':');
      builder.append(")}");
    }
    Objects.requireNonNull(builder);
    return builder;
  }

  private StringBuilder appendStructField(StringBuilder builder, Schema schema, String fieldId, ObjectNode propertiesNode, Character seperator) {
    // safe to append nothing
    Objects.requireNonNull(builder);
    Objects.requireNonNull(propertiesNode);

    if ( propertiesNode != null && propertiesNode.isObject() && propertiesNode.size() > 0 ) {

      currentDepth += 1;

      if (StringUtils.isNotBlank(fieldId)) {
        builder.append(pigEscape(fieldId));
        builder.append(seperator);
        builder.append("(");
        builder = appendPropertiesNode(builder, schema, propertiesNode, ':');
        builder.append(")");
      }

      currentDepth -= 1;

    }
    Objects.requireNonNull(builder);
    return builder;
  }

  private static String pigEscape( String fieldId ) {
    return fieldId;
  }

  private static String pigType( FieldType fieldType ) {
    switch ( fieldType ) {
      case STRING:
        return "chararray";
      case INTEGER:
        return "int";
      case NUMBER:
        return "double";
      case OBJECT:
        return "tuple";
      default:
        return fieldType.name().toLowerCase();
    }
  }

  private String schemaSymbol( Schema schema ) {
    if (schema == null) {
      return null;
    }
    // this needs to return whatever
    if (schema.getUri().getScheme().equals("file")) {
      String inputFile = schema.getUri().getPath();
      String resourcePath = dropSourcePathPrefix(inputFile, config.getSourceDirectory());
      for (String sourcePath : config.getSourcePaths()) {
        resourcePath = dropSourcePathPrefix(resourcePath, sourcePath);
      }
      return dropExtension(resourcePath).replace("/", "_").replace("-", "");
    } else {
      return "IDK";
    }
  }
}
