/// <summary>
/// Determines whether the the given army can surprise strike another army.
/// </summary>
/// <param name="striker">The striking army.</param>
/// <param name="sustainer">The army being struck.</param>
/// <returns>True if the surprise strike is valid; false otherwise.</returns>
private static bool CanSurpriseStrike(Army striker, Army sustainer)
{
// To be valid:
// 1) The striking army must of course contain a submarine, and
// 2) The sustaining army must not contain a destroyer, which counters surprise strikes.
return(striker.Contains(UnitType.Submarine) && !sustainer.Contains(UnitType.Destroyer));
}
/// <summary>
/// Ensures that an air unit cannot fire upon a submarine without a destroyer.
/// </summary>
/// <param name="firer">The firing unit type.</param>
/// <param name="sustainer">The unit type being fired upon.</param>
/// <param name="firingArmy">The army to which the firing unit belongs.</param>
/// <returns>True if the hit is not an air-to-submarine hit or if a destroyer is present in the firing army; false otherwise.</returns>
private static bool CheckAir(UnitType firer, UnitType sustainer, Army firingArmy)
{
// One of two conditions must be met for this to not be an air-to-submarine hit at all:
// 1) The firing unit type is not an air unit, or
// 2) The unit type being fired upon is not a submarine.
// Finally, even if this is an air-to-submarine hit, it is still valid if the firing army contains a destroyer. Thus, if even
// one of these three conditions are met, the hit is valid.
return(firer.Category != UnitCategory.Air || sustainer != UnitType.Submarine || firingArmy.Contains(UnitType.Destroyer));
}