CREATE FUNCTION CreateInstance(
  IN patient TEXT,
  IN study TEXT,
  IN series TEXT,
  IN instance TEXT,
  OUT isNewPatient BIGINT,
  OUT isNewStudy BIGINT,
  OUT isNewSeries BIGINT,
  OUT isNewInstance BIGINT,
  OUT patientKey BIGINT,
  OUT studyKey BIGINT,
  OUT seriesKey BIGINT,
  OUT instanceKey BIGINT) AS $$
BEGIN
  SELECT internalId FROM Resources INTO instanceKey WHERE publicId = instance AND resourceType = 3;

  IF NOT (instanceKey IS NULL) THEN
    -- This instance already exists, stop here
    isNewInstance := 0;
  ELSE
    SELECT internalId FROM Resources INTO patientKey WHERE publicId = patient AND resourceType = 0;
    SELECT internalId FROM Resources INTO studyKey WHERE publicId = study AND resourceType = 1;
    SELECT internalId FROM Resources INTO seriesKey WHERE publicId = series AND resourceType = 2;

    IF patientKey IS NULL THEN
      -- Must create a new patient
      ASSERT studyKey IS NULL;
      ASSERT seriesKey IS NULL;
      ASSERT instanceKey IS NULL;
      INSERT INTO Resources VALUES (DEFAULT, 0, patient, NULL) RETURNING internalId INTO patientKey;
      isNewPatient := 1;
    ELSE
      isNewPatient := 0;
    END IF;
  
    ASSERT NOT patientKey IS NULL;

    IF studyKey IS NULL THEN
      -- Must create a new study
      ASSERT seriesKey IS NULL;
      ASSERT instanceKey IS NULL;
      INSERT INTO Resources VALUES (DEFAULT, 1, study, patientKey) RETURNING internalId INTO studyKey;
      isNewStudy := 1;
    ELSE
      isNewStudy := 0;
    END IF;

    ASSERT NOT studyKey IS NULL;
    
    IF seriesKey IS NULL THEN
      -- Must create a new series
      ASSERT instanceKey IS NULL;
      INSERT INTO Resources VALUES (DEFAULT, 2, series, studyKey) RETURNING internalId INTO seriesKey;
      isNewSeries := 1;
    ELSE
      isNewSeries := 0;
    END IF;
  
    ASSERT NOT seriesKey IS NULL;
    ASSERT instanceKey IS NULL;

    INSERT INTO Resources VALUES (DEFAULT, 3, instance, seriesKey) RETURNING internalId INTO instanceKey;
    isNewInstance := 1;
  END IF;  
END;
$$ LANGUAGE plpgsql;