From 882f51057d5cdca3d559eb2451b7fe7b369af3c5 Mon Sep 17 00:00:00 2001
From: Andrew Cooper <andrew.cooper@nearmap.com>
Date: Sat, 30 Oct 2021 23:52:13 +1100
Subject: [PATCH] Add tower models

---
 90 Tower/csharp/Tower/Models/Needle.cs | 31 +++++++++++++
 90 Tower/csharp/Tower/Models/Towers.cs | 60 ++++++++++++++++++++++++++
 2 files changed, 91 insertions(+)
 create mode 100644 90 Tower/csharp/Tower/Models/Needle.cs
 create mode 100644 90 Tower/csharp/Tower/Models/Towers.cs

diff --git a/90 Tower/csharp/Tower/Models/Needle.cs b/90 Tower/csharp/Tower/Models/Needle.cs
new file mode 100644
index 00000000..e373efe9
--- /dev/null
+++ b/90 Tower/csharp/Tower/Models/Needle.cs	
@@ -0,0 +1,31 @@
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Tower.Models
+{
+    internal class Needle : IEnumerable<int>
+    {
+        private readonly Stack<int> _disks = new Stack<int>();
+
+        public int Top => _disks.TryPeek(out var disc) ? disc : default;
+
+        public bool TryPut(int disc)
+        {
+            if (_disks.Count == 0 || disc < _disks.Peek())
+            {
+                _disks.Push(disc);
+                return true;
+            }
+
+            return false;
+        }
+
+        public bool TryGetTopDisk(out int disk) => _disks.TryPop(out disk);
+
+        public IEnumerator<int> GetEnumerator() =>
+            Enumerable.Repeat(1, 7 - _disks.Count).Concat(_disks).GetEnumerator();
+
+        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+    }
+}
\ No newline at end of file
diff --git a/90 Tower/csharp/Tower/Models/Towers.cs b/90 Tower/csharp/Tower/Models/Towers.cs
new file mode 100644
index 00000000..830fa631
--- /dev/null
+++ b/90 Tower/csharp/Tower/Models/Towers.cs	
@@ -0,0 +1,60 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Tower.Models
+{
+    internal class Towers : IEnumerable<(int, int, int)>
+    {
+        private readonly Needle[] _needles = new[] { new Needle(), new Needle(), new Needle() };
+
+        public bool TryFindDisk(int disk, out int needle)
+        {
+            for (needle = 1; needle <= 3; needle++)
+            {
+                if (_needles[needle].Top == disk) { return true; }
+            }
+
+            return false;
+        }
+
+        public bool TryMoveDisk(int from, int to)
+        {
+            if (!_needles[from].TryGetTopDisk(out var disk))
+            {
+                throw new InvalidOperationException($"Needle {from} is empty");
+            }
+
+            if (_needles[to].TryPut(disk)) { return true; }
+
+            _needles[from].TryPut(disk);
+            return false;
+        }
+
+        public IEnumerator<(int, int, int)> GetEnumerator() => new TowersEnumerator(_needles);
+
+        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+        private class TowersEnumerator : IEnumerator<(int First, int Second, int Third)>
+        {
+            private readonly List<IEnumerator<int>> _enumerators;
+
+            public TowersEnumerator(Needle[] needles)
+            {
+                _enumerators = needles.Select(n => n.GetEnumerator()).ToList();
+            }
+
+            public (int First, int Second, int Third) Current =>
+                (_enumerators[0].Current, _enumerators[1].Current, _enumerators[2].Current);
+
+            object IEnumerator.Current => Current;
+
+            public void Dispose() => _enumerators.ForEach(e => e.Dispose());
+
+            public bool MoveNext() => _enumerators.All(e => e.MoveNext());
+
+            public void Reset() => _enumerators.ForEach(e => e.Reset());
+        }
+    }
+}
\ No newline at end of file