Add SearchPatternShotSelector

77_Salvo/csharp/Targetting/SearchPatternShotSelector.cs

@@ -0,0 +1,54 @@
+namespace Salvo.Targetting;
+
+internal class SearchPatternShotSelector : ShotSelector
+{
+    private const int MaxSearchPatternAttempts = 100;
+    private readonly IRandom _random;
+    private readonly SearchPattern _searchPattern = new();
+    private readonly List<Position> _shots = new();
+
+    internal SearchPatternShotSelector(Grid source, Grid target, IRandom random) 
+        : base(source, target)
+    {
+        _random = random;
+    }
+
+    internal override IEnumerable<Position> GetShots()
+    {
+        while(_shots.Count < NumberOfShots)
+        {
+            var (seed, _) = _random.NextShipPosition();
+            SearchFrom(seed);
+        }
+        return _shots;
+    }
+
+    private void SearchFrom(Position candidateShot)
+    {
+        var attemptsLeft = MaxSearchPatternAttempts;
+        while (true)
+        {
+            _searchPattern.Reset();
+            if (attemptsLeft-- == 0) { return; }
+            candidateShot = candidateShot.BringIntoRange(_random);
+            if (FindValidShots(candidateShot)) { return; }
+        }
+    }
+
+    private bool FindValidShots(Position candidateShot)
+    {
+        while (true)
+        {
+            if (IsValidShot(candidateShot))
+            {
+                _shots.Add(candidateShot);
+                if (_shots.Count == NumberOfShots) { return true; }
+            }
+            if (!_searchPattern.TryGetOffset(out var offset)) { return false; }
+            candidateShot += offset;
+        }
+    }
+
+    private bool IsValidShot(Position candidate)
+        => candidate.IsInRange && !Target.WasTargetedAt(candidate, out _) && !_shots.Contains(candidate);
+}