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/*
 * Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * or in the "license" file accompanying this file. This file is distributed
 * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package com.amazon.randomcutforest.testutils;

import static java.lang.Math.PI;

import java.util.Random;

public class ShingledData {

    public static double[][] generateShingledData(int size, int period, int dimensions, long seed) {
        double[][] answer = new double[size][];
        int entryIndex = 0;
        boolean filledShingleAtleastOnce = false;
        double[] history = new double[dimensions];
        int count = 0;
        double[] data = getData(size + dimensions - 1, period, 100, 5, seed);
        for (int j = 0; j < size + dimensions - 1; ++j) { // we stream here ....
            history[entryIndex] = data[j];
            entryIndex = (entryIndex + 1) % dimensions;
            if (entryIndex == 0) {
                filledShingleAtleastOnce = true;
            }
            if (filledShingleAtleastOnce) {
                answer[count++] = getShinglePoint(history, entryIndex, dimensions);
            }
        }
        return answer;
    }

    private static double[] getShinglePoint(double[] recentPointsSeen, int indexOfOldestPoint, int shingleLength) {
        double[] shingledPoint = new double[shingleLength];
        int i = 0;
        for (int j = 0; j < shingleLength; ++j) {
            double point = recentPointsSeen[(j + indexOfOldestPoint) % shingleLength];
            shingledPoint[i++] = point;

        }
        return shingledPoint;
    }

    private static double[] getData(int num, int period, double amplitude, double noise, long seed) {

        double[] data = new double[num];
        Random noiseprg = new Random(seed);
        for (int i = 0; i < num; i++) {
            data[i] = amplitude * Math.cos(2 * PI * (i + 50) / period) + noise * noiseprg.nextDouble();
            if (noiseprg.nextDouble() < 0.01) {
                double change = noiseprg.nextDouble() < 0.5 ? 10 * noise : -10 * noise;
                data[i] += change;
                System.out.println(" timestamp " + i + " changing by " + change);
            }

        }

        return data;
    }
}