package org.atriasoft.pngencoder;

import java.util.Objects;

class PngEncoderDeflaterSegmentResult {
	// https://github.com/madler/zlib/blob/master/adler32.c#L143
	static long combine(final long adler1, final long adler2, final long len2) {
		long BASEL = 65521;
		long sum1;
		long sum2;
		long rem;
		
		rem = len2 % BASEL;
		sum1 = adler1 & 0xffffL;
		sum2 = rem * sum1;
		sum2 %= BASEL;
		sum1 += (adler2 & 0xffffL) + BASEL - 1;
		sum2 += ((adler1 >> 16) & 0xffffL) + ((adler2 >> 16) & 0xffffL) + BASEL - rem;
		if (sum1 >= BASEL) {
			sum1 -= BASEL;
		}
		if (sum1 >= BASEL) {
			sum1 -= BASEL;
		}
		if (sum2 >= (BASEL << 1)) {
			sum2 -= (BASEL << 1);
		}
		if (sum2 >= BASEL) {
			sum2 -= BASEL;
		}
		return sum1 | (sum2 << 16);
	}
	
	private final PngEncoderDeflaterBuffer deflatedSegment;
	private final PngEncoderDeflaterBuffer originalSegment;
	private final long originalSegmentAdler32;
	
	private final int originalSegmentLength;
	
	PngEncoderDeflaterSegmentResult(final PngEncoderDeflaterBuffer originalSegment, final PngEncoderDeflaterBuffer deflatedSegment, final long originalSegmentAdler32,
			final int originalSegmentLength) {
		this.originalSegment = Objects.requireNonNull(originalSegment, "originalSegment");
		this.deflatedSegment = Objects.requireNonNull(deflatedSegment, "deflatedSegment");
		this.originalSegmentAdler32 = originalSegmentAdler32;
		this.originalSegmentLength = originalSegmentLength;
	}
	
	public PngEncoderDeflaterBuffer getDeflatedSegment() {
		return this.deflatedSegment;
	}
	
	public PngEncoderDeflaterBuffer getOriginalSegment() {
		return this.originalSegment;
	}
	
	long getUpdatedAdler32(final long originalAdler32) {
		return PngEncoderDeflaterSegmentResult.combine(originalAdler32, this.originalSegmentAdler32, this.originalSegmentLength);
	}
}