namespace day3;

public class Day3
{
    private int _rows;
    private int _columns;
    private char[][] _grid;

    public Day3(string fileContents)
    {
        var lines = fileContents.Split(Environment.NewLine);
        _grid = lines.Select(line => line.ToCharArray()).ToArray();
        _rows = _grid.Length;
        _columns = _grid[0].Length;
    }

    private bool _isCharacterASymbol(char c) {
        return !char.IsDigit(c) && c != '.';
    }

    private bool _isSymbolInSurroundingLocation(int i, int j) 
    {
        var foundSymbol = false;
        for (var ii = i - 1; ii <= i + 1; ii++)
        {
            for (var jj = j - 1; jj <= j + 1; jj++)
            {
                if (ii >= 0 && jj >= 0 && ii < _rows && jj < _columns) {
                    foundSymbol |= _isCharacterASymbol(_grid[ii][jj]);
                }
            }
        }
        return foundSymbol;
    }

    private IEnumerable<MachinePart> _getSurroundingMachineParts(int i, int j, IList<MachinePart> machineParts)
    {
        return machineParts.Where(machinePart => machinePart.Locations.Aggregate(false, (hasBeenFound, currentPoint) => {
            var differenceRow = Math.Abs(i - currentPoint.Item1);
            var differenceCol = Math.Abs(j - currentPoint.Item2);
            return hasBeenFound || (!(differenceRow == 0 && differenceCol == 0) && differenceRow <= 1 && differenceCol <= 1);
        }));
    }

    private IList<MachinePart> _getAllMachinePartsInGrid() 
    {
        var machinePartsList = new List<MachinePart>();
        int currentlyParsedNumber = 0;
        var locations = new List<(int, int)>();
        bool isSymbolFound = false;
        
        // We want to iterate over every cell
        for (int i = 0; i < _rows; i++) 
        {
            for (int j = 0; j < _columns; j++)
            {
                var cellContents = _grid[i][j];
                if (char.IsDigit(cellContents))
                {
                    // Check the surroundings for a symbol
                    isSymbolFound |= _isSymbolInSurroundingLocation(i, j);
                    locations.Add((i, j));
                    currentlyParsedNumber = (currentlyParsedNumber * 10) + int.Parse(cellContents.ToString());
                }

                // Check if we are done scanning the number (i.e. at the end of a row or we find a non-integer)
                if (!char.IsDigit(cellContents) || j == _columns - 1) 
                {
                    if (isSymbolFound) 
                    {
                        machinePartsList.Add(new MachinePart {
                          Id = machinePartsList.Count,
                          Value = currentlyParsedNumber,
                          Locations = locations
                        });
                    }

                    locations = new List<(int, int)>();
                    currentlyParsedNumber = 0;
                    isSymbolFound = false;
                }
            }
        }

        return machinePartsList;
    }

    public int PartOne()
    {
        var machinePartsList = _getAllMachinePartsInGrid();
        return machinePartsList.Aggregate(0, (total, current) => total + current.Value);
    }

    public long PartTwo() 
    {
        var machinePartsList = _getAllMachinePartsInGrid();
        var runningTotal = 0L;

        // We are going to do a scan for all gears 

        for (int i = 0; i < _rows; i++) 
        {
            for (int j = 0; j < _columns; j++)
            {
                var cellContents = _grid[i][j];
                if (cellContents == '*') 
                {
                    var surroundingMachineParts = _getSurroundingMachineParts(i, j, machinePartsList);
                    var numberOfSurroundingMachingParts = surroundingMachineParts.Count();
                    if (numberOfSurroundingMachingParts == 2) {
                        runningTotal += surroundingMachineParts.Aggregate(1, (currentRatio, machinePart) => currentRatio * machinePart.Value);
                    }
                }
            }
        }

        return runningTotal;
    }

}