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 *   and the following disclaimer.
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 *   with the distribution.
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 *   STMicroelectronics company nor the names of its contributors may be used to endorse or
 *   promote products derived from this software without specific prior written permission.
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 * - All of the icons, pictures, logos and other images that are provided with the source code
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 *   shall not be redistributed to any third party or modified in any way.
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package com.st.BlueMS.demos.Audio.BlueVoice.ASRServices.GoogleASR;

import android.support.annotation.NonNull;
import android.support.annotation.Nullable;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;

/**
 * Class that parse a json response from the ASR algorithm and extract the best transcript
 */
public class GoogleASRResponseParser {

    private static final String RESULT= "result";
    private static final String RESULT_INDEX= "result_index";
    private static final String TRANSCRIPT= "transcript";
    private static final String CONFIDENCE= "confidence";
    private static final String ALTERNATIVE= "alternative";

    private double mConfidence=1.0;
    private String mTranscript=null;

    private static String extractJsonString(InputStream in) throws IOException {
        InputStreamReader inputStreamReader = new InputStreamReader(in, "UTF-8");
        BufferedReader br = new BufferedReader(inputStreamReader);
        String s;
        StringBuilder resultContent = new StringBuilder();
        br.readLine();
        while ((s = br.readLine()) != null) {
            resultContent.append(s);
        }
        return resultContent.toString();
    }

    /**
     * parse the response
     * @param response response stream
     * @throws JSONException exception throw if the response is malformed
     */
    GoogleASRResponseParser(InputStream response) throws JSONException {
        String json = null;
        try {
            json = extractJsonString(response);
        } catch (IOException e) {
            e.printStackTrace();
        }
        parseJson(json);
    }

    private ArrayList<Result> extractAllResults(JSONArray alternative) throws JSONException {
        int nAlternative = alternative.length();
        ArrayList<Result> res = new ArrayList<>(nAlternative);
        for(int i=0;i<nAlternative ; i++){
            JSONObject result = alternative.getJSONObject(i);
            String str = result.getString(TRANSCRIPT);
            double conf =1.0;
            if(result.has(CONFIDENCE))
                conf = result.getDouble(CONFIDENCE);
            res.add(new Result(str,conf));

        }
        return res;
    }

    private void parseJson(String json) throws JSONException {

        JSONObject jsonResponse = new JSONObject(json);
        JSONArray jsonArrayResults = jsonResponse.getJSONArray(RESULT);
        int respIndex = jsonResponse.getInt(RESULT_INDEX);
        JSONObject jsonObjectAlternative = jsonArrayResults.getJSONObject(respIndex);
        JSONArray jsonArrayAlternative = jsonObjectAlternative.getJSONArray(ALTERNATIVE);

        ArrayList<Result> allResult = extractAllResults(jsonArrayAlternative);
        Collections.sort(allResult);
        Result bestResult = allResult.get(0);
        mConfidence=bestResult.confidence;
        mTranscript=bestResult.transcript;

    }

    /**
     * get the best transcript
     * @return transcript or null if the is not present
     */
    @Nullable String getTranscript(){
        return mTranscript;
    }

    /**
     * get the confidence value (between 0 and 1) of the best transcript
     * @return confidence value for the transcript
     */
    double getConfidence(){
        return mConfidence;
    }


    private static class Result implements Comparable<Result> {

        public String transcript;
        public double confidence;

        public Result(String t, double c){
            transcript=t;
            confidence=c;
        }

        @Override
        public int compareTo(@NonNull Result result) {
            return Double.compare(result.confidence,confidence);
        }
    }

}
