package sparseviewer.otf;

public class DelayCorrection {

    public static CorrectedXY correctXY(double[] x,
                                        double[] y,
                                        double shiftSamples) {
        double[] xc = shiftArray(x, shiftSamples);
        double[] yc = shiftArray(y, shiftSamples);

        return new CorrectedXY(xc, yc);
    }

    public static double[] shiftArray(double[] values, double shiftSamples) {
        if (values == null) {
            return null;
        }

        double[] out = new double[values.length];

        for (int i = 0; i < values.length; i++) {
            double sourceIndex = i - shiftSamples;
            out[i] = interpolateAt(values, sourceIndex);
        }

        return out;
    }

    private static double interpolateAt(double[] values, double index) {
        if (values == null || values.length == 0) {
            return Double.NaN;
        }

        if (index < 0.0 || index > values.length - 1) {
            return Double.NaN;
        }

        int i0 = (int) Math.floor(index);
        int i1 = i0 + 1;

        if (i1 >= values.length) {
            return values[i0];
        }

        double v0 = values[i0];
        double v1 = values[i1];

        if (!isFinite(v0) || !isFinite(v1)) {
            return Double.NaN;
        }

        double alpha = index - i0;

        return (1.0 - alpha) * v0 + alpha * v1;
    }

    private static boolean isFinite(double v) {
        return !Double.isNaN(v) && !Double.isInfinite(v);
    }

    public static class CorrectedXY {

        private final double[] x;
        private final double[] y;

        public CorrectedXY(double[] x, double[] y) {
            this.x = x;
            this.y = y;
        }

        public double[] getX() {
            return x;
        }

        public double[] getY() {
            return y;
        }
    }
}