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Implement coastal accessibility checks for support-move orders

This commit is contained in:
Tim Van Baak 2024-09-06 15:19:58 +00:00
parent aaf2e78730
commit 4096e4d517
2 changed files with 64 additions and 21 deletions
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51
MultiversalDiplomacy/Model/OrderParser.cs
View File

@ -403,36 +403,47 @@ public class OrderParser(World world)
: target.Season.Turn;
var destProvince = world.Map.Provinces.Single(province => province.Is(support.destProvince));
string? destLocationKey = null;
// DATC 4.B.6 requires that "irrelevant" locations like army to Spain nc be ignored.
// To satisfy this, any location of the wrong type is categorically ignored, so for an army the
// "north coast" location effectively doesn't exist here.
// Note that target is used instead of subject, since it is possible to support a move to an inaccessible
// coast as long as the subject can reach the province and the target can reach the location.
// DATC 4.B specifies how to interpret orders with missing or incorrect locations. These issues arise because
// of provinces with multiple locations of the same type, i.e. two-coast provinces in Classical. In general,
// DATC's only concern is to disambiguate the order, failing the order only when it is ineluctably ambiguous
// (4.B.1) or explicitly incorrect (4.B.3). Irrelevant or nonexistent locations can be ignored.
// If there is only one possible location for the moving unit, that location is used. The idea of land and
// water locations is an implementation detail of 5dplomacy and not part of the Diplomacy rules, so they will
// usually be omitted, and so moving an army to any land province or a fleet to a non-multi-coast province is
// naturally unambiguous even without the location.
var unitLocations = destProvince.Locations.Where(loc => loc.Type switch {
LocationType.Land => target.Type == UnitType.Army,
LocationType.Water => target.Type == UnitType.Fleet,
_ => false,
});
// DATC 4.6.B also requires that unknown coasts be ignored. To satisfy this, an additional filter by name.
// Doing both of these filters means "A - Spain/nc" is as meaningful as "F - Spain/wc".
var matchingLocations = unitLocations.Where(loc => loc.Is(support.destLocation));
// If one location matched, use that location. If the coast is inaccessible to the target, the order will
// be invalidated by a path check later to satisfy DATC 4.B.3.
string? destLocationKey = matchingLocations.FirstOrDefault(defaultValue: null)?.Key;
if (!unitLocations.Any()) return false; // If *no* locations match, the move is illegal
if (unitLocations.Count() == 1) destLocationKey ??= unitLocations.Single().Key;
// If more than one location is possible for the unit, the order must be disambiguated by the dest location
// or the physical realities of which coast is accessible. DATC 4.B.3 makes an order illegal if the location
// is specified but it isn't an accessible coast, so successfully specifying a location takes precedence over
// there being one accessible coast.
if (destLocationKey is null) {
// If no location matched, location was omitted, nonexistent, or the wrong type.
// If one location is accessible, DATC 4.B.2 requires that it be used.
// If more than one location is accessible, DATC 4.B.1 requires the order fail.
// TODO check which locations are accessible per the above
destLocationKey = unitLocations.First().Key;
// return false;
var matchingLocations = unitLocations.Where(loc => loc.Is(support.destLocation));
if (matchingLocations.Any()) destLocationKey ??= matchingLocations.Single().Key;
}
// If the order location didn't disambiguate the coasts, either because it's missing or it's nonsense, the
// order can be disambiguated by there being one accessible coast from the order source.
if (destLocationKey is null) {
Location source = world.Map.GetLocation(target.Location);
var accessibleLocations = destProvince.Locations.Where(loc => loc.Adjacents.Contains(source));
if (accessibleLocations.Count() == 1) destLocationKey ??= accessibleLocations.Single().Key;
}
// If the order is still ambiguous, fail per DATC 4.B.1. This also satisfies 4.B.4, which prefers for
// programmatic adjudicators with order validation to require the coasts instead of interpreting the ambiguous
// support by referring to the move order it supports.
if (destLocationKey is null) return false;
var destLocation = world.Map.GetLocation(destLocationKey);
order = new SupportMoveOrder(power, subject, target, new(destTimeline, destTurn), destLocation);
return true;

34
MultiversalDiplomacyTests/OrderParserTest.cs
View File

@ -296,8 +296,40 @@ public class OrderParserTest
World world = World.WithStandardMap().AddUnits("France F Portugal");
Assert.That(
OrderParser.TryParseOrder(world, "France", "Portugal - Spain", out Order? northOrder),
OrderParser.TryParseOrder(world, "France", "Portugal - Spain", out Order? _),
Is.False,
"Should not parse ambiguous coastal move");
}
[Test]
public void DisambiguateSupportToSingleAccessibleCoast()
{
World world = World.WithStandardMap().AddUnits("France F Gascony", "France F Marseilles");
Assert.That(
OrderParser.TryParseOrder(world, "France", "Gascony S Marseilles - Spain", out Order? northOrder),
"Failed to parse north coast order");
Assert.That(
OrderParser.TryParseOrder(world, "France", "Marseilles S Gascony - Spain", out Order? southOrder),
"Failed to parse south coast order");
Assert.That(northOrder, Is.TypeOf<SupportMoveOrder>(), "Unexpected north coast order");
Assert.That(southOrder, Is.TypeOf<SupportMoveOrder>(), "Unexpected south coast order");
Location northTarget = ((SupportMoveOrder)northOrder!).Location;
Location southTarget = ((SupportMoveOrder)southOrder!).Location;
Assert.That(northTarget.Name, Is.EqualTo("south coast"), "Unexpected disambiguation");
Assert.That(southTarget.Name, Is.EqualTo("north coast"), "Unexpected disambiguation");
}
[Test]
public void DisambiguateSupportToMultipleAccessibleCoasts()
{
World world = World.WithStandardMap().AddUnits("France F Portugal", "France F Marseilles");
Assert.That(
OrderParser.TryParseOrder(world, "France", "Marseilles S Portugal - Spain", out Order? _),
Is.False,
"Should not parse ambiguous coastal support");
}
}