package com.macasaet;

import java.util.ArrayList;

import java.util.List;

import java.util.stream.Collectors;

import java.util.stream.Stream;

import java.util.stream.StreamSupport;

import org.junit.jupiter.api.Test;

public class Day03 {

/**

protected Stream<byte[]> getDiagnosticReport() {

return StreamSupport

.stream(new LineSpliterator("day-03.txt"),

false)

.map(string -> {

final var chars = string.toCharArray();

final var bits = new byte[chars.length];

for (int i = chars.length; --i >= 0; bits[i] = chars[i] == '0' ? (byte) 0 : (byte) 1) ;

return bits;

});

}

protected int toUnsignedInt(final byte[] bits) {

int result = 0;

for (int i = bits.length; --i >= 0; result += bits[i] * Math.pow(2, bits.length - i - 1)) ;

return result;

}

@Test

public final void part1() {

final var list = getDiagnosticReport().collect(Collectors.toList());

final int width = list.get(0).length;

final int[] zeroCounts = new int[width];

for (int i = zeroCounts.length; --i >= 0; zeroCounts[i] = 0) ;

final int[] oneCounts = new int[width];

for (int i = oneCounts.length; --i >= 0; oneCounts[i] = 0) ;

for (final var array : list) {

for (int j = 0; j < width; j++) {

if (array[j] == 0) {

zeroCounts[j] += 1;

} else {

oneCounts[j] += 1;

}

}

}

final byte[] gammaArray = new byte[width];

final byte[] epsilonArray = new byte[width];

for (int i = gammaArray.length; --i >= 0; ) {

gammaArray[i] = zeroCounts[i] > oneCounts[i] ? (byte) 0 : (byte) 1;

epsilonArray[i] = zeroCounts[i] > oneCounts[i] ? (byte) 1 : (byte) 0;

}

final int gammaRate = toUnsignedInt(gammaArray);

final int epsilonRate = toUnsignedInt(epsilonArray);

System.out.println("Part 1: " + (gammaRate * epsilonRate));

}

@Test

public final void part2() {

final var list = getDiagnosticReport().collect(Collectors.toList());

final int width = list.get(0).length;

List<byte[]> oxygenCandidates = new ArrayList<>(list);

for (int i = 0; i < width && oxygenCandidates.size() > 1; i++) {

int zeros = 0;

int ones = 0;

for (final var value : oxygenCandidates) {

if (value[i] == 0) {

zeros++;

} else {

ones++;

}

}

final int index = i;

if (ones >= zeros) {

oxygenCandidates = oxygenCandidates.stream().filter(value -> value[index] == 1).collect(Collectors.toList());

} else {

oxygenCandidates = oxygenCandidates.stream().filter(value -> value[index] == 0).collect(Collectors.toList());

}

}

if (oxygenCandidates.size() > 1) {

throw new IllegalStateException("Too many oxygen candidates");

}

List<byte[]> co2Candidates = new ArrayList<>(list);

for (int i = 0; i < width && co2Candidates.size() > 1; i++) {

int zeros = 0;

int ones = 0;

for (final var value : co2Candidates) {

if (value[i] == 0) {

zeros++;

} else {

ones++;

}

}

final int index = i;

if (zeros <= ones) {

co2Candidates = co2Candidates.stream().filter(value -> value[index] == 0).collect(Collectors.toList());

} else {

co2Candidates = co2Candidates.stream().filter(value -> value[index] == 1).collect(Collectors.toList());

}

}

if (co2Candidates.size() > 1) {

throw new IllegalStateException("Too many CO2 candidates");

}

final byte[] oxyArray = oxygenCandidates.get(0);

final byte[] co2Array = co2Candidates.get(0);

final int oxygenGeneratorRating = toUnsignedInt(oxyArray);

final int co2ScrubberRating = toUnsignedInt(co2Array);

System.out.println("Part 2: " + (oxygenGeneratorRating * co2ScrubberRating));

}

}

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