Add split-second-stopwatch exercise

Author: ErikSchierboom

config.json

@@ -2717,10 +2717,16 @@
       {
         "slug": "split-second-stopwatch",
         "name": "Split-Second Stopwatch",
-        "uuid": "791feb53-7250-4176-bd8e-6b1a76748f19",
-        "practices": [],
-        "prerequisites": [],
-        "difficulty": 4
+        "uuid": "1d95976d-b3db-4705-b345-0832f226620f",
+        "practices": [
+          "datetimes",
+          "classes"
+        ],
+        "prerequisites": [
+          "datetimes",
+          "classes"
+        ],
+        "difficulty": 5
       }
     ],
     "foregone": [

exercises/Exercises.sln

@@ -1 +1,22 @@
 # Instructions
+
+Your task is to build a stopwatch to keep precise track of lap times.
+
+The stopwatch uses four commands (start, stop, lap, and reset) to keep track of:
+
+1. The current lap's tracked time
+2. Previously recorded lap times
+
+What commands can be used depends on which state the stopwatch is in:
+
+1. Ready: initial state
+2. Running: tracking time
+3. Stopped: not tracking time
+
+| Command | Begin state | End state | Effect                                                   |
+| ------- | ----------- | --------- | -------------------------------------------------------- |
+| Start   | Ready       | Running   | Start tracking time                                      |
+| Start   | Stopped     | Running   | Resume tracking time                                     |
+| Stop    | Running     | Stopped   | Stop tracking time                                       |
+| Lap     | Running     | Running   | Add current lap to previous laps, then reset current lap |
+| Reset   | Stopped     | Ready     | Reset current lap and clear previous laps                |

exercises/practice/split-second-stopwatch/.docs/instructions.md

@@ -1 +1,6 @@
 # Introduction
+
+You've always run for the thrill of it — no schedules, no timers, just the sound of your feet on the pavement.
+But now that you've joined a competitive running crew, things are getting serious.
+Training sessions are timed to the second, and every split second counts.
+To keep pace, you've picked up the _Split-Second Stopwatch_ — a sleek, high-tech gadget that's about to become your new best friend.

exercises/practice/split-second-stopwatch/.docs/introduction.md

@@ -0,0 +1,12 @@
+using Xunit;
+
+public class {{ testClass }}
+{
+    {{- for test in tests }}
+    [Fact{{ if !for.first }}(Skip = "Remove this Skip property to run this test"){{ end }}]
+    public void {{ test.testMethod }}()
+    {
+        Assert.Equal({{ test.expected }}, {{ testedClass }}.{{ test.testedMethod }}({{ test.input.commands }}));
+    }
+    {{ end -}}
+}

exercises/practice/split-second-stopwatch/.meta/Generator.tpl

@@ -4,14 +4,16 @@
   ],
   "files": {
     "solution": [
-      "LastLap.cs"
+      "SplitSecondStopwatch.cs"
     ],
     "test": [
-      "LastLapTests.cs"
+      "SplitSecondStopwatchTests.cs"
     ],
     "example": [
       ".meta/Example.cs"
     ]
   },
-  "blurb": ""
+  "blurb": "Keep track of time through a digital stopwatch.",
+  "source": "Erik Schierboom",
+  "source_url": "https://github.com/exercism/problem-specifications/pull/2547"
 }

exercises/practice/split-second-stopwatch/.meta/config.json

@@ -0,0 +1,97 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[ddb238ea-99d4-4eaa-a81d-3c917a525a23]
+description = "new stopwatch starts in ready state"
+
+[b19635d4-08ad-4ac3-b87f-aca10e844071]
+description = "new stopwatch's current lap has no elapsed time"
+
+[492eb532-268d-43ea-8a19-2a032067d335]
+description = "new stopwatch's total has no elapsed time"
+
+[8a892c1e-9ef7-4690-894e-e155a1fe4484]
+description = "new stopwatch does not have previous laps"
+
+[5b2705b6-a584-4042-ba3a-4ab8d0ab0281]
+description = "start from ready state changes state to running"
+
+[748235ce-1109-440b-9898-0a431ea179b6]
+description = "start does not change previous laps"
+
+[491487b1-593d-423e-a075-aa78d449ff1f]
+description = "start initiates time tracking for current lap"
+
+[a0a7ba2c-8db6-412c-b1b6-cb890e9b72ed]
+description = "start initiates time tracking for total"
+
+[7f558a17-ef6d-4a5b-803a-f313af7c41d3]
+description = "start cannot be called from running state"
+
+[32466eef-b2be-4d60-a927-e24fce52dab9]
+description = "stop from running state changes state to stopped"
+
+[621eac4c-8f43-4d99-919c-4cad776d93df]
+description = "stop pauses time tracking for current lap"
+
+[465bcc82-7643-41f2-97ff-5e817cef8db4]
+description = "stop pauses time tracking for total"
+
+[b1ba7454-d627-41ee-a078-891b2ed266fc]
+description = "stop cannot be called from ready state"
+
+[5c041078-0898-44dc-9d5b-8ebb5352626c]
+description = "stop cannot be called from stopped state"
+
+[3f32171d-8fbf-46b6-bc2b-0810e1ec53b7]
+description = "start from stopped state changes state to running"
+
+[626997cb-78d5-4fe8-b501-29fdef804799]
+description = "start from stopped state resumes time tracking for current lap"
+
+[58487c53-ab26-471c-a171-807ef6363319]
+description = "start from stopped state resumes time tracking for total"
+
+[091966e3-ed25-4397-908b-8bb0330118f8]
+description = "lap adds current lap to previous laps"
+
+[1aa4c5ee-a7d5-4d59-9679-419deef3c88f]
+description = "lap resets current lap and resumes time tracking"
+
+[4b46b92e-1b3f-46f6-97d2-0082caf56e80]
+description = "lap continues time tracking for total"
+
+[ea75d36e-63eb-4f34-97ce-8c70e620bdba]
+description = "lap cannot be called from ready state"
+
+[63731154-a23a-412d-a13f-c562f208eb1e]
+description = "lap cannot be called from stopped state"
+
+[e585ee15-3b3f-4785-976b-dd96e7cc978b]
+description = "stop does not change previous laps"
+
+[fc3645e2-86cf-4d11-97c6-489f031103f6]
+description = "reset from stopped state changes state to ready"
+
+[20fbfbf7-68ad-4310-975a-f5f132886c4e]
+description = "reset resets current lap"
+
+[00a8f7bb-dd5c-43e5-8705-3ef124007662]
+description = "reset clears previous laps"
+
+[76cea936-6214-4e95-b6d1-4d4edcf90499]
+description = "reset cannot be called from ready state"
+
+[ba4d8e69-f200-4721-b59e-90d8cf615153]
+description = "reset cannot be called from running state"
+
+[0b01751a-cb57-493f-bb86-409de6e84306]
+description = "supports very long laps"

exercises/practice/split-second-stopwatch/.meta/tests.toml

@@ -1,32 +1,59 @@
 public enum StopwatchState
 {
     Ready,
-    Running,
-    Paused,
-    Stopped
+    Running
 }
 
 public class SplitSecondStopwatch(TimeProvider time)
 {
-    public StopwatchState State { get; private set; }
+    private readonly List<TimeSpan> _splits = new();
+    private DateTimeOffset? _splitStart;
+    
+    private TimeSpan PreviousSplits => _splits.Aggregate(TimeSpan.Zero, (total, split) => total + split);
+    private TimeSpan CurrentSplit => _splitStart is {} start ? time.GetUtcNow() - start : TimeSpan.Zero;
+
+    public StopwatchState State { get; private set; } = StopwatchState.Ready;
+    public List<TimeSpan> PreviousLaps { get; } = new();
+
+    public TimeSpan CurrentLap => CurrentSplit + PreviousSplits;
+    public TimeSpan Total => CurrentLap + PreviousLaps.Aggregate(TimeSpan.Zero, (total, split) => total + split);
 
     public void Start()
     {
-        throw new NotImplementedException();
+        if (State != StopwatchState.Ready)
+            throw new InvalidOperationException("Can't start a stopwatch that is not stopped.");
+        
+        _splitStart = time.GetUtcNow();
+        State = StopwatchState.Running;
     }
 
     public void Stop()
     {
-        throw new NotImplementedException();
-    }
+        if (State != StopwatchState.Running)
+            throw new InvalidOperationException("Can't stop a stopwatch that is not started.");
 
-    public void Split()
+        _splits.Add(CurrentSplit);
+        _splitStart = null;
+        State = StopwatchState.Ready;
+    }
+    
+    public void Reset()
     {
-        throw new NotImplementedException();
+        if (State != StopwatchState.Ready)
+            throw new InvalidOperationException("Can't reset a stopwatch that is not stopped.");
+        
+        _splits.Clear();
+        _splitStart = null;
+        State = StopwatchState.Ready;
     }
-
-    public void Pause()
+    
+    public void Lap()
     {
-        throw new NotImplementedException();
+        if (State != StopwatchState.Running)
+            throw new InvalidOperationException("Can't lap a stopwatch that is not started stopped.");
+        
+        PreviousLaps.Add(CurrentLap);
+        _splits.Clear();
+        _splitStart = time.GetUtcNow();
     }
 }