Implement circular-buffer

config.json

@@ -742,6 +742,15 @@
         "prerequisites": [],
         "difficulty": 1,
         "topics": []
+      },
+      {
+        "slug": "circular-buffer",
+        "name": "Circular Buffer",
+        "uuid": "2e709c96-56e3-4a48-8948-e180b210e86d",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 1,
+        "topics": []
       }
     ]
   },

exercises/practice/circular-buffer/.docs/instructions.md

@@ -0,0 +1,58 @@
+# Instructions
+
+A circular buffer, cyclic buffer or ring buffer is a data structure that uses a single, fixed-size buffer as if it were connected end-to-end.
+
+A circular buffer first starts empty and of some predefined length.
+For example, this is a 7-element buffer:
+
+```text
+[ ][ ][ ][ ][ ][ ][ ]
+```
+
+Assume that a 1 is written into the middle of the buffer (exact starting location does not matter in a circular buffer):
+
+```text
+[ ][ ][ ][1][ ][ ][ ]
+```
+
+Then assume that two more elements are added — 2 & 3 — which get appended after the 1:
+
+```text
+[ ][ ][ ][1][2][3][ ]
+```
+
+If two elements are then removed from the buffer, the oldest values inside the buffer are removed.
+The two elements removed, in this case, are 1 & 2, leaving the buffer with just a 3:
+
+```text
+[ ][ ][ ][ ][ ][3][ ]
+```
+
+If the buffer has 7 elements then it is completely full:
+
+```text
+[5][6][7][8][9][3][4]
+```
+
+When the buffer is full an error will be raised, alerting the client that further writes are blocked until a slot becomes free.
+
+When the buffer is full, the client can opt to overwrite the oldest data with a forced write.
+In this case, two more elements — A & B — are added and they overwrite the 3 & 4:
+
+```text
+[5][6][7][8][9][A][B]
+```
+
+3 & 4 have been replaced by A & B making 5 now the oldest data in the buffer.
+Finally, if two elements are removed then what would be returned is 5 & 6 yielding the buffer:
+
+```text
+[ ][ ][7][8][9][A][B]
+```
+
+Because there is space available, if the client again uses overwrite to store C & D then the space where 5 & 6 were stored previously will be used not the location of 7 & 8.
+7 is still the oldest element and the buffer is once again full.
+
+```text
+[C][D][7][8][9][A][B]
+```

exercises/practice/circular-buffer/.meta/config.json

@@ -0,0 +1,17 @@
+{
+  "authors": [],
+  "files": {
+    "solution": [
+      "lib/CircularBuffer.rakumod"
+    ],
+    "test": [
+      "t/circular-buffer.rakutest"
+    ],
+    "example": [
+      ".meta/solutions/lib/CircularBuffer.rakumod"
+    ]
+  },
+  "blurb": "A data structure that uses a single, fixed-size buffer as if it were connected end-to-end.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Circular_buffer"
+}

exercises/practice/circular-buffer/.meta/solutions/lib/CircularBuffer.rakumod

@@ -0,0 +1,15 @@
+my class X::CircularBuffer::BufferIsEmpty is Exception {
+    method message {'Buffer is empty'}
+}
+
+class CircularBuffer {
+    has $.capacity;
+
+    method read {}
+
+    method write {}
+
+    method clear {}
+
+    method overwrite {}
+}

exercises/practice/circular-buffer/.meta/solutions/t/circular-buffer.rakutest

@@ -0,0 +1 @@
+../../../t/circular-buffer.rakutest

exercises/practice/circular-buffer/.meta/template-data.yaml

@@ -0,0 +1,83 @@
+properties:
+  run:
+    test: |-
+      my $ops = %case<input><operations>.map(-> %op {
+          given %op<operation> {
+              when 'read' {
+                  if %op<should_succeed> {
+                      sprintf(q:to/CASE/, %op<expected>).trim-trailing;
+                          is(
+                              $buffer.read,
+                              %s,
+                              "read buffer",
+                          );
+                      CASE
+                  }
+                  else {
+                      sprintf(q:to/CASE/).trim-trailing;
+                          throws-like(
+                              { $buffer.read },
+                              X::CircularBuffer::BufferIsEmpty,
+                              "read error",
+                          );
+                      CASE
+                  }
+              }
+              when 'write' {
+                  '    flunk "write NYI";'
+              }
+              when 'clear' {
+                  '    flunk "clear NYI";'
+              }
+              when 'overwrite' {
+                  '    flunk "overwrite NYI";'
+              }
+              default {
+                  '    flunk "NYI";'
+              }
+          }
+      }).join("\n\n");
+
+      sprintf(q:to/END/, %case<description>.raku, %case<input><capacity>, $ops);
+      subtest %s => {
+          my CircularBuffer $buffer.=new(:capacity(%s));
+
+      %s
+      };
+      END
+
+unit: false
+
+example: |-
+  my class X::CircularBuffer::BufferIsEmpty is Exception {
+      method message {'Buffer is empty'}
+  }
+
+  class CircularBuffer {
+      has $.capacity;
+      
+      method read {}
+
+      method write {}
+
+      method clear {}
+
+      method overwrite {}
+  }
+
+stub: |-
+  my class X::CircularBuffer::BufferIsEmpty is Exception {
+      method message {'Buffer is empty'}
+  }
+
+  class CircularBuffer {
+      has $.capacity;
+      
+      method read {}
+
+      method write {}
+
+      method clear {}
+
+      method overwrite {}
+  }

exercises/practice/circular-buffer/.meta/tests.toml

@@ -0,0 +1,52 @@
+# 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.
+
+[28268ed4-4ff3-45f3-820e-895b44d53dfa]
+description = "reading empty buffer should fail"
+
+[2e6db04a-58a1-425d-ade8-ac30b5f318f3]
+description = "can read an item just written"
+
+[90741fe8-a448-45ce-be2b-de009a24c144]
+description = "each item may only be read once"
+
+[be0e62d5-da9c-47a8-b037-5db21827baa7]
+description = "items are read in the order they are written"
+
+[2af22046-3e44-4235-bfe6-05ba60439d38]
+description = "full buffer can't be written to"
+
+[547d192c-bbf0-4369-b8fa-fc37e71f2393]
+description = "a read frees up capacity for another write"
+
+[04a56659-3a81-4113-816b-6ecb659b4471]
+description = "read position is maintained even across multiple writes"
+
+[60c3a19a-81a7-43d7-bb0a-f07242b1111f]
+description = "items cleared out of buffer can't be read"
+
+[45f3ae89-3470-49f3-b50e-362e4b330a59]
+description = "clear frees up capacity for another write"
+
+[e1ac5170-a026-4725-bfbe-0cf332eddecd]
+description = "clear does nothing on empty buffer"
+
+[9c2d4f26-3ec7-453f-a895-7e7ff8ae7b5b]
+description = "overwrite acts like write on non-full buffer"
+
+[880f916b-5039-475c-bd5c-83463c36a147]
+description = "overwrite replaces the oldest item on full buffer"
+
+[bfecab5b-aca1-4fab-a2b0-cd4af2b053c3]
+description = "overwrite replaces the oldest item remaining in buffer following a read"
+
+[9cebe63a-c405-437b-8b62-e3fdc1ecec5a]
+description = "initial clear does not affect wrapping around"

exercises/practice/circular-buffer/lib/CircularBuffer.rakumod

@@ -0,0 +1,15 @@
+my class X::CircularBuffer::BufferIsEmpty is Exception {
+    method message {'Buffer is empty'}
+}
+
+class CircularBuffer {
+    has $.capacity;
+
+    method read {}
+
+    method write {}
+
+    method clear {}
+
+    method overwrite {}
+}