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package cn.apiclub.captcha.audio.noise;

import java.security.SecureRandom;
import java.util.List;
import java.util.Random;

import cn.apiclub.captcha.audio.Mixer;
import cn.apiclub.captcha.audio.Sample;
import cn.apiclub.captcha.util.FileUtil;

/**
 * Adds noise to a {@link Sample} from one of the given noiseFiles.
 * By default this noise comes from one of three files, all located in
 * /sounds/noises/: radio_tuning.wav,
 * restaurant.wav, and swimming.wav. This can be
 * overridden by passing the location of your own sound files to the
 * constructor, e.g.:
 * 
 *  * String myFiles = { "/mysounds/noise1.wav", "/mysounds/noise2.wav" };
 * NoiseProducer myNp = new RandomNoiseProducer(myFiles);
 * 
 * 
 * @author James Childers
 * 
 */
public class RandomNoiseProducer implements NoiseProducer {

    private static final Random RAND = new SecureRandom();
    private static final String[] DEFAULT_NOISES = {
            "/sounds/noises/radio_tuning.wav", 
            "/sounds/noises/restaurant.wav",
            "/sounds/noises/swimming.wav", };

    private final String _noiseFiles[];

    public RandomNoiseProducer() {
        this(DEFAULT_NOISES);
    }

    public RandomNoiseProducer(String[] noiseFiles) {
        _noiseFiles = noiseFiles;
    }

    /**
     * Append the given samples to each other, then add random
     * noise to the result.
     * 
     */
    @Override public Sample addNoise(List samples) {
        Sample appended = Mixer.append(samples);
        String noiseFile = _noiseFiles[RAND.nextInt(_noiseFiles.length)];
        Sample noise = FileUtil.readSample(noiseFile);

        // Decrease the volume of the noise to make sure the voices can be heard
        return Mixer.mix(appended, 1.0, noise, 0.6);
    }

    @Override public String toString() {
        StringBuffer sb = new StringBuffer();
        sb.append("[Noise files: ");
        sb.append(_noiseFiles);
        sb.append("]");

        return sb.toString();
    }
}