private bool IsAligned(int y, int x, TransformedTile tile)
{
var edges = tile.GetEdges().Select(EdgeToNum).ToArray();
if (y == 0)
{
if (_matchingEdges[edges[0]].Count != 1)
{
return(false);
}
}
else
{
var otherTile = _matchingEdges[edges[0]].SingleOrDefault(t => t != tile.Tile.Id);
if (_result[y - 1, x].Tile.Id != otherTile || EdgeToNum(_result[y - 1, x].GetEdge(2)) != edges[0])
{
return(false);
}
}
if (x == 0)
{
if (_matchingEdges[edges[3]].Count != 1)
{
return(false);
}
}
else
{
var otherTile = _matchingEdges[edges[3]].SingleOrDefault(t => t != tile.Tile.Id);
if (_result[y, x - 1].Tile.Id != otherTile || EdgeToNum(_result[y, x - 1].GetEdge(1)) != edges[3])
{
return(false);
}
}
if (y + 1 == _result.GetLength(0))
{
if (_matchingEdges[edges[2]].Count != 1)
{
return(false);
}
}
if (x + 1 == _result.GetLength(1))
{
if (_matchingEdges[edges[1]].Count != 1)
{
return(false);
}
}
return(true);
}
private static IReadOnlyDictionary <ushort, IReadOnlySet <long> > FindMatchingEdges(IReadOnlyDictionary <long, Tile> tiles)
{
var potentialMatches = new ConcurrentDictionary <ushort, HashSet <long> >();
foreach (var(_, tile) in tiles)
{
var transformed = new TransformedTile(tile, Flip.None, Rotate.CW0);
foreach (var edge in transformed.GetEdges())
{
potentialMatches.GetOrAdd(EdgeToNum(edge), _ => new HashSet <long>()).Add(tile.Id);
potentialMatches.GetOrAdd(EdgeToNum(edge.Reverse().ToList()), _ => new HashSet <long>()).Add(tile.Id);
}
}
return(potentialMatches.ToDictionary(x => x.Key, x => (IReadOnlySet <long>)x.Value));
}