static AdjacencyGraph<AutoMixingBucket, AutoMixEdge> BuildGraph(
IEnumerable<IMixItem> mixableTracks,
IEnumerable<IMixItem> unknownTracks,
AutoMixingContext context, out AutoMixingBucket optionalStartVertex)
{
IList<AutoMixingBucket> buckets = mixableTracks
.GroupBy(g => g.ActualKey)
.Select(g => new AutoMixingBucket(g, g.Key))
.ToList();
Log.DebugFormat("{0} mixable tracks ({1} buckets aka vertices), {2} unmixable tracks (unknown key/BPM).",
mixableTracks.Count(), buckets.Count(), unknownTracks.Count());
var graph = new AdjacencyGraph<AutoMixingBucket, AutoMixEdge>();
graph.AddVertexRange(buckets);
// If we are auto-mixing a subset of tracks within a mix, we must
// keep them harmonically compatible with the tracks immediately
// before and after i.e. (preceeding)(tracks to mix)(following).
//
// To find such a path, we unfortunately can't just look for paths
// where (start = preceeding and end = following) because they
// might be using different keys that are not used by any of the
// tracks in the graph.
//
// To get around this problem, we add empty 'placeholder' buckets
// (vertices) to the graph for the preceeding/following keys, and
// look for paths that use these vertices as start/end points.
// This works because when we unpack the buckets, these vertices
// simply unpack as empty (they don't contain any tracks) so we can
// use them for the final path of mix items without producing any
// messy placeholder/temporary tracks.
optionalStartVertex = AddPlaceholderVertexIfRequired(graph, context.GetOptionalStartKey());
AddPlaceholderVertexIfRequired(graph, context.GetOptionalEndKey());
return graph;
}
static IEnumerable<AutoMixingBucket> GetPreferredMix(
IVertexListGraph<AutoMixingBucket, AutoMixEdge> graph,
AutoMixingBucket optionalStartVertex,
HarmonicKey? optionalEndKey,
bool computeAll)
{
LongestPathAlgorithm<AutoMixingBucket, AutoMixEdge> algo;
if (!computeAll && (optionalEndKey == null && optionalStartVertex == null))
algo = new LongestPathAlgorithm<AutoMixingBucket, AutoMixEdge>(graph);
else
algo = new AllLongestPathsAlgorithm<AutoMixingBucket, AutoMixEdge>(graph);
HarmonicKey? optionalStartKey = null;
if (optionalStartVertex != null)
{
algo.SetRootVertex(optionalStartVertex);
optionalStartKey = optionalStartVertex.ActualKey;
}
var stopwatch = Stopwatch.StartNew();
algo.Compute();
stopwatch.Stop();
Log.DebugFormat("Found {0} paths in {1}.", algo.LongestPaths.Count(), stopwatch.Elapsed);
if (!algo.LongestPaths.Any())
return null;
LogPaths(algo.LongestPaths);
IEnumerable<AutoMixEdge> bestPath = GetPathSatisfyingOptionalStartAndEndKey(algo.LongestPaths,
optionalStartKey, optionalEndKey);
if (bestPath == null)
return null;
Log.DebugFormat("Using path: {0}", FormatPath(bestPath));
return GetVertices(bestPath);
}
static AutoMixingBucket AddPlaceholderVertexIfRequired(
AdjacencyGraph<AutoMixingBucket, AutoMixEdge> graph, HarmonicKey? key)
{
if (!key.HasValue)
return null;
var vertex = new AutoMixingBucket(key.Value);
graph.AddVertex(vertex);
return vertex;
}
