/// <summary>
/// Yields all possible matches for this leg definition held within the collection of <paramref name="positions"/>
/// </summary>
/// <param name="options">Strategy matcher options guiding matching behaviors</param>
/// <param name="legs">The preceding legs already matched for the parent strategy definition</param>
/// <param name="positions">The remaining, unmatched positions available to be matched against</param>
/// <returns>An enumerable of potential matches</returns>
public IEnumerable <OptionStrategyLegDefinitionMatch> Match(
OptionStrategyMatcherOptions options,
IReadOnlyList <OptionPosition> legs,
OptionPositionCollection positions
)
{
foreach (var position in options.Enumerate(Filter(legs, positions, false)))
{
var multiplier = position.Quantity / Quantity;
if (multiplier != 0)
{
yield return(new OptionStrategyLegDefinitionMatch(multiplier,
position.WithQuantity(multiplier * Quantity)
));
}
}
}
private IEnumerable <OptionStrategyDefinitionMatch> Match(
OptionStrategyMatcherOptions options,
ImmutableList <OptionStrategyLegDefinitionMatch> legMatches,
ImmutableList <OptionPosition> legPositions,
OptionPositionCollection positions,
int multiplier
)
{
var nextLegIndex = legPositions.Count;
if (nextLegIndex == Legs.Count)
{
if (nextLegIndex > 0)
{
yield return(new OptionStrategyDefinitionMatch(this, legMatches, multiplier));
}
}
else if (positions.Count >= LegCount - nextLegIndex)
{
// grab the next leg definition and perform the match, restricting total to configured maximum per leg
var nextLeg = Legs[nextLegIndex];
var maxLegMatch = options.GetMaximumLegMatches(nextLegIndex);
foreach (var legMatch in nextLeg.Match(options, legPositions, positions).Take(maxLegMatch))
{
// add match to the match we're constructing and deduct matched position from positions collection
// we track the min multiplier in line so when we're done, we have the total number of matches for
// the matched set of positions in this 'thread' (OptionStrategy.Quantity)
foreach (var definitionMatch in Match(options,
legMatches.Add(legMatch),
legPositions.Add(legMatch.Position),
positions - legMatch.Position,
Math.Min(multiplier, legMatch.Multiplier)
))
{
yield return(definitionMatch);
}
}
}
else
{
// positions.Count < LegsCount indicates a failed match
// could include partial matches, would allow an algorithm to determine if adding a
// new position could help reduce overall margin exposure by completing a strategy
}
}
/// <summary>
/// Determines all possible matches for this definition using the provided <paramref name="positions"/>.
/// This includes OVERLAPPING matches. It's up to the actual matcher to make decisions based on which
/// matches to accept. This allows the matcher to prioritize matching certain positions over others.
/// </summary>
public IEnumerable <OptionStrategyDefinitionMatch> Match(
OptionStrategyMatcherOptions options,
OptionPositionCollection positions
)
{
// TODO : Pass OptionStrategyMatcherOptions in and respect applicable options
if (positions.Count < LegCount)
{
return(Enumerable.Empty <OptionStrategyDefinitionMatch>());
}
var multiplier = int.MaxValue;
// first check underlying lots has correct sign and sufficient magnitude
var underlyingLotsSign = Math.Sign(UnderlyingLots);
if (underlyingLotsSign != 0)
{
var underlyingPositionSign = Math.Sign(positions.UnderlyingQuantity);
if (underlyingLotsSign != underlyingPositionSign ||
Math.Abs(positions.UnderlyingQuantity) < Math.Abs(UnderlyingLots))
{
return(Enumerable.Empty <OptionStrategyDefinitionMatch>());
}
// set multiplier for underlying
multiplier = positions.UnderlyingQuantity / UnderlyingLots;
}
// TODO : Consider add OptionStrategyLegDefinition for underlying for consistency purposes.
// Might want to enforce that it's always the first leg definition as well for easier slicing.
return(Match(options,
ImmutableList <OptionStrategyLegDefinitionMatch> .Empty,
ImmutableList <OptionPosition> .Empty,
positions,
multiplier
).Distinct());
}
/// <summary>
/// Initializes a new instance of the <see cref="OptionStrategyMatcher"/> class
/// </summary>
/// <param name="options">Specifies definitions and other options controlling the matcher</param>
public OptionStrategyMatcher(OptionStrategyMatcherOptions options)
{
Options = options;
}
/// <summary>
/// Determines all possible matches for this definition using the provided <paramref name="positions"/>.
/// This includes OVERLAPPING matches. It's up to the actual matcher to make decisions based on which
/// matches to accept. This allows the matcher to prioritize matching certain positions over others.
/// </summary>
public IEnumerable <OptionStrategyDefinitionMatch> Match(OptionPositionCollection positions)
{
return(Match(OptionStrategyMatcherOptions.ForDefinitions(this), positions));
}
/// <summary>
/// Attempts to match the positions to this definition exactly once, by evaluating the enumerable and
/// taking the first entry matched. If not match is found, then false is returned and <paramref name="match"/>
/// will be null.
/// </summary>
public bool TryMatchOnce(OptionStrategyMatcherOptions options, OptionPositionCollection positions, out OptionStrategyDefinitionMatch match)
{
match = Match(options, positions).FirstOrDefault();
return(match != null);
}
