AcronymDataJsonParser.java

package vandy.mooc.model.aidl;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

import android.util.JsonReader;
import android.util.JsonToken;

/**
 * Parses the Json acronym data returned from the Acronym Services API
 * and returns a List of JsonAcronym objects that contain this data.
 */
public class AcronymDataJsonParser {
    /**
     * Used for logging purposes.
     */
    private final String TAG =
        this.getClass().getCanonicalName();

    /**
     * Parse the @a inputStream and convert it into a List of AcronymData
     * objects.
     */
    public List<AcronymExpansion> parseJsonStream(InputStream inputStream)
        throws IOException {

        // Create a JsonReader for the inputStream.
        try (JsonReader reader =
             new JsonReader(new InputStreamReader(inputStream,
                                                  "UTF-8"))) {
            // Log.d(TAG, "Parsing the results returned as an array");

            // Handle the array returned from the Acronym Service.
            return parseAcronymWebServiceResults(reader);
        }
    }

    /**
     * Parse a Json stream and convert it into a List of AcronymData
     * objects.
     */
    public List<AcronymExpansion> parseAcronymWebServiceResults(JsonReader reader)
        throws IOException {

        reader.beginArray();
        // If the acronym wasn't expanded return null;
        if (reader.peek() == JsonToken.END_ARRAY)
            return null;

        // Create a AcronymData object for each element in the
        // Json array.
        final List<AcronymExpansion> acronymExpansion =
            parseAcronymData(reader);
        reader.endArray();
        return acronymExpansion;
    }

    public List<AcronymExpansion> parseAcronymData(JsonReader reader)
        throws IOException {

        List<AcronymExpansion> acronymExpansion = null;
        reader.beginObject();

        outerloop:
        while (reader.hasNext()) {
            String name = reader.nextName();
            switch (name) {
            case AcronymData.sf_JSON:
                // Log.d(TAG, "reading sf field");
                reader.nextString();
                break;
            case AcronymData.lfs_JSON:
                // Log.d(TAG, "reading lfs field");
                if (reader.peek() == JsonToken.BEGIN_ARRAY)
                    acronymExpansion = parseAcronymLongFormArray(reader);
                break outerloop;
            default:
                reader.skipValue();
                // Log.d(TAG, "weird problem with " + name + " field");
                break;
            }
        }

        reader.endObject();
        return acronymExpansion;
    }

    /**
     * Parse a Json stream and convert it into a List of AcronymData
     * objects.
     */
    public List<AcronymExpansion> parseAcronymLongFormArray(JsonReader reader)
        throws IOException {

        // Log.d(TAG, "reading lfs elements");

        reader.beginArray();

        final List<AcronymExpansion> acronyms =
            new ArrayList<AcronymExpansion>();

        while (reader.hasNext()) 
            acronyms.add(parseAcronymExpansion(reader));
            
        reader.endArray();
        return acronyms;
    }

    /**
     * Parse a Json stream and return a AcronymExpansion object.
     */
    public AcronymExpansion parseAcronymExpansion(JsonReader reader) 
        throws IOException {

        reader.beginObject();

        final AcronymExpansion acronymExpansion =
            new AcronymExpansion();

        while (reader.hasNext()) {
            String name = reader.nextName();
            switch (name) {
            case AcronymExpansion.lf_JSON:
                acronymExpansion.setLf(reader.nextString());
                // Log.d(TAG, "reading lf " + acronym.getLongForm());
                break;
            case AcronymExpansion.freq_JSON:
                acronymExpansion.setFreq(reader.nextInt());
                // Log.d(TAG, "reading freq " + acronym.getFreq());
                break;
            case AcronymExpansion.since_JSON:
                acronymExpansion.setSince(reader.nextInt());
                // Log.d(TAG, "reading since " + acronym.getSince());
                break;
            default:
                reader.skipValue();
                // Log.d(TAG, "ignoring " + name);
                break;
            }
        } 
        
        reader.endObject();
        return acronymExpansion;
    }
}