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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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*/

package com.google.refine.importers;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.jena.rdf.model.Model;
import org.apache.jena.rdf.model.ModelFactory;
import org.apache.jena.rdf.model.Statement;
import org.apache.jena.rdf.model.StmtIterator;

import com.fasterxml.jackson.databind.node.ObjectNode;
import com.google.refine.ProjectMetadata;
import com.google.refine.expr.ExpressionUtils;
import com.google.refine.importing.ImportingJob;
import com.google.refine.model.Cell;
import com.google.refine.model.Column;
import com.google.refine.model.ModelException;
import com.google.refine.model.Project;
import com.google.refine.model.Row;


public class RdfTripleImporter extends ImportingParserBase {
    private Mode mode;
    
    public enum Mode {
        RDFXML,
        NT,
        N3,
        TTL,
        JSONLD
    }

    public RdfTripleImporter() {
        this(Mode.NT);
    }
    
    public RdfTripleImporter(Mode mode) {
        super(true);
        this.mode = mode;
    }

    @Override
    public void parseOneFile(Project project, ProjectMetadata metadata, ImportingJob job, String fileSource,
            InputStream input, int limit, ObjectNode options, List<Exception> exceptions) {
        // create an empty model
        Model model = ModelFactory.createDefaultModel();

        try {
            switch (mode) {
            case NT:
                // TODO: The standard lang name is "N-TRIPLE"
                // we may need to switch if we change packagings
                model.read(input, null, "NT");
                break;
            case N3:
                model.read(input, null, "N3");
                break;
            case TTL:
                model.read(input, null, "TTL");
                break;
            case JSONLD:
                // TODO: The standard lang name is "JSONLD"
                model.read(input, null, "JSON-LD");
                break;
            case RDFXML:
                model.read(input, null);            
                break;
            default:
                throw new IllegalArgumentException("Unknown parsing mode");    
            }
        } catch (Exception e) {
            exceptions.add(e);
            return;
        }

      StmtIterator triples = model.listStatements();
      
      try {
          Map<String, List<Row>> subjectToRows = new LinkedHashMap<String, List<Row>>();
          Column subjectColumn = new Column(project.columnModel.allocateNewCellIndex(), "subject");
          project.columnModel.addColumn(0, subjectColumn, false);
          project.columnModel.setKeyColumnIndex(0);
          
          while (triples.hasNext()) {
              Statement triple = triples.nextStatement();
              String subject = triple.getSubject().toString();
              String predicate = triple.getPredicate().toString();
              String object = triple.getObject().toString();

              Column column = project.columnModel.getColumnByName(predicate);
              if (column == null) {
                  column = new Column(project.columnModel.allocateNewCellIndex(), predicate);
                  project.columnModel.addColumn(-1, column, true);
              }

              int cellIndex = column.getCellIndex();
              if (subjectToRows.containsKey(subject)) {
                  List<Row> rows = subjectToRows.get(subject);
                  for (Row row : rows) {
                      if (!ExpressionUtils.isNonBlankData(row.getCellValue(cellIndex))) {
                          row.setCell(cellIndex, new Cell(object, null));
                          object = null;
                          break;
                      }
                  }

                  if (object != null) {
                      Row row = new Row(project.columnModel.getMaxCellIndex() + 1);
                      rows.add(row);

                      row.setCell(cellIndex, new Cell(object, null));
                  }
              } else {
                  List<Row> rows = new ArrayList<Row>();
                  subjectToRows.put(subject, rows);

                  Row row = new Row(project.columnModel.getMaxCellIndex() + 1);
                  rows.add(row);

                  row.setCell(subjectColumn.getCellIndex(), new Cell(subject, null));
                  row.setCell(cellIndex, new Cell(object, null));
              }
          }

          for (Entry<String, List<Row>> entry : subjectToRows.entrySet()) {
              project.rows.addAll(entry.getValue());
          }
      } catch (ModelException e) {
          exceptions.add(e);
      } 
    }
}
