AnnotationListHandler.java

package nl.knaw.huygens.alexandria.endpoint.iiif;

/*
 * #%L
 * alexandria-main
 * =======
 * Copyright (C) 2015 - 2017 Huygens ING (KNAW)
 * =======
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/gpl-3.0.html>.
 * #L%
 */

import java.io.IOException;
import java.io.InputStream;
import java.time.Instant;
import java.util.Deque;
import java.util.concurrent.ConcurrentLinkedDeque;
import java.util.concurrent.atomic.AtomicBoolean;

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;
import com.fasterxml.jackson.databind.node.TextNode;

import nl.knaw.huygens.alexandria.endpoint.webannotation.WebAnnotationService;
import nl.knaw.huygens.alexandria.exception.BadRequestException;

public class AnnotationListHandler {

  private JsonParser jParser;
  private String context;
  private Deque<String> deque = new ConcurrentLinkedDeque<>();
  private AtomicBoolean firstField = new AtomicBoolean(true);
  private AtomicBoolean inResources = new AtomicBoolean(false);
  private WebAnnotationService webAnnotationService;

  public AnnotationListHandler(InputStream inputStream, WebAnnotationService webAnnotationService) {
    this.webAnnotationService = webAnnotationService;
    try {
      jParser = new JsonFactory().createParser(inputStream);
      deque.add("{");
    } catch (IOException e) {
      e.printStackTrace();
    }
  }

  public String getNextString() {
    try {
      if (inResources.get()) {
        handleNextResource();

      } else {
        handleRootFields();
      }
    } catch (IOException e) {
      e.printStackTrace();
    }
    return deque.isEmpty() ? null : deque.pop();
  }

  private void handleRootFields() throws IOException, JsonProcessingException {
    if (jParser.nextToken() != JsonToken.END_OBJECT) {
      String fieldname = jParser.getCurrentName();
      if (fieldname != null) {
        if (!firstField.get()) {
          deque.add(",");
        }
        firstField.set(false);

        switch (fieldname) {
        case "@context":
          jParser.nextToken();
          context = jParser.getText(); // we'll be needing this later
          deque.add("\"@context\":\"" + context + "\"");
          break;

        case "resources":
          if (context == null) {
            throw new BadRequestException("Missing @context field, should be defined at the start of the json payload.");
          }
          deque.add("\"resources\":[");
          jParser.nextToken(); // "["
          // parse each resource
          firstField.set(true);
          inResources.set(true);
          break;

        default:
          jParser.nextToken();
          deque.add("\"" + fieldname + "\":");
          JsonToken currentToken = jParser.currentToken();
          if (currentToken.isStructStart()) {
            deque.add(new ObjectMapper().readTree(jParser).toString());
          } else if (currentToken.isNumeric()) {
            deque.add(jParser.getValueAsString());
          } else {
            deque.add("\"" + jParser.getText() + "\"");
          }
          break;
        }
      }

    } else {
      close();
    }
  }

  private void handleNextResource() throws IOException, JsonProcessingException {
    if (jParser.nextToken() != JsonToken.END_ARRAY) {
      if (!firstField.get()) {
        deque.add(",");
      }
      firstField.set(false);
      ObjectNode annotationNode = new ObjectMapper().readTree(jParser);
      String created = Instant.now().toString();
      annotationNode.set("http://purl.org/dc/terms/created", new TextNode(created));
      annotationNode.set("@context", new TextNode(context));
      ObjectNode storedAnnotation = webAnnotationService.validateAndStore(annotationNode);
      deque.add(new ObjectMapper().writeValueAsString(storedAnnotation));

    } else {
      deque.add("]");
      inResources.set(false);
    }
  }

  private void close() {
    try {
      jParser.close();
      deque.add("}");
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}