using System;
using System.IO;
using System.Linq;
using AdvenOfCode.Contracts;

namespace AoC_2025;

public class Day03 : IPuzzleSolver<long>
{
    private string[] ParsePuzzleInput(string path)
    {
        var puzzleInput = File.ReadAllLines(path)
            .Where(line => !string.IsNullOrWhiteSpace(line))
            .ToArray();
        return puzzleInput;
    }

    public long SolvePart1(string pathToPuzzleInput)
    {
        var batterieBankStrings = ParsePuzzleInput(pathToPuzzleInput);
        var batterieBanks = batterieBankStrings.Select(bbs => ParseBatterieBank(bbs));
        var voltages = batterieBanks.Select(bb => FindMaxVoltage(bb));
        var sumVoltages = voltages.Sum();
        return sumVoltages;
    }
    
    public long SolvePart2(string pathToPuzzleInput)
    {
        const int voltageLength = 12;
        var batterieBankStrings = ParsePuzzleInput(pathToPuzzleInput);
        var batterieBanks = batterieBankStrings.Select(bbs => ParseBatterieBank(bbs));
        var voltages = batterieBanks.Select(bb => GetMaxSuperVoltage(bb, voltageLength));
        var sumVoltages = voltages.Sum();
        return sumVoltages;
    }

    private int[] ParseBatterieBank(string batterieBank)
    {
        return batterieBank
            .Select(c => new string(c, 1))
            .Select(value => int.Parse(value))
            .ToArray();
    }

    private long FindMaxVoltage(Span<int> batterieBank)
    {
        var (firstNumber, position) = GetMax(batterieBank[..^1]);
        var (secondNumber, _) = GetMax(batterieBank[(position + 1)..]);
        var voltage = Combine(firstNumber, secondNumber);
        return voltage;
    }

    private long Combine(long first, long second)
    {
        return (first * 10) + second;
    }
    
    private long GetMaxSuperVoltage(Span<int> batterieBank, int voltageLength)
    {
        var indexedVoltageLength = voltageLength - 1;
        var currentBankPosition = 0;
        var superVoltage = 0L;
        for (var i = 0; i < voltageLength; i++)
        {
            var (max, numberPosition) = GetMax(batterieBank[currentBankPosition..^(indexedVoltageLength - i)]);
            superVoltage = Combine(superVoltage, max);
            currentBankPosition += numberPosition + 1;
        }

        return superVoltage;
    }

    private (int max, int currentPosition) GetMax(Span<int> batterieBank)
    {
        var max = batterieBank[0];
        var currentPosition = 0;
        for (var i = 1; i < batterieBank.Length; i++)
        {
            if (max < batterieBank[i])
            {
                max = batterieBank[i];
                currentPosition = i;
            }
        }

        return (max, currentPosition);
    }
}