Add practice exercise: rotational-cipher

config.json

@@ -386,6 +386,14 @@
         "prerequisites": [],
         "difficulty": 8
       },
+      {
+        "slug": "rotational-cipher",
+        "name": "Rotational Cipher",
+        "uuid": "76fd6c44-a09b-41a7-9fec-addf26b35059",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 8
+      },
       {
         "slug": "scrabble-score",
         "name": "Scrabble Score",

exercises/practice/rotational-cipher/.docs/instructions.md

@@ -0,0 +1,29 @@
+# Instructions
+
+Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.
+
+The Caesar cipher is a simple shift cipher that relies on transposing all the letters in the alphabet using an integer key between `0` and `26`.
+Using a key of `0` or `26` will always yield the same output due to modular arithmetic.
+The letter is shifted for as many values as the value of the key.
+
+The general notation for rotational ciphers is `ROT + <key>`.
+The most commonly used rotational cipher is `ROT13`.
+
+A `ROT13` on the Latin alphabet would be as follows:
+
+```text
+Plain:  abcdefghijklmnopqrstuvwxyz
+Cipher: nopqrstuvwxyzabcdefghijklm
+```
+
+It is stronger than the Atbash cipher because it has 27 possible keys, and 25 usable keys.
+
+Ciphertext is written out in the same formatting as the input including spaces and punctuation.
+
+## Examples
+
+- ROT5 `omg` gives `trl`
+- ROT0 `c` gives `c`
+- ROT26 `Cool` gives `Cool`
+- ROT13 `The quick brown fox jumps over the lazy dog.` gives `Gur dhvpx oebja sbk whzcf bire gur ynml qbt.`
+- ROT13 `Gur dhvpx oebja sbk whzcf bire gur ynml qbt.` gives `The quick brown fox jumps over the lazy dog.`

exercises/practice/rotational-cipher/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "jimmytty"
+  ],
+  "files": {
+    "solution": [
+      "rotational-cipher.sql"
+    ],
+    "test": [
+      "rotational-cipher_test.sql"
+    ],
+    "example": [
+      ".meta/example.sql"
+    ]
+  },
+  "blurb": "Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Caesar_cipher"
+}

exercises/practice/rotational-cipher/.meta/example.sql

@@ -0,0 +1,33 @@
+UPDATE "rotational-cipher"
+    SET result = (
+        WITH RECURSIVE rcte (text, chr, shift) AS (
+            VALUES(text, NULL, NULL)
+            UNION ALL
+            SELECT
+                SUBSTR(text, 2),
+                SUBSTR(text, 1, 1),
+                IIF(
+                    GLOB('[A-Za-z]', SUBSTR(text, 1, 1)),
+                    UNICODE(SUBSTR(text, 1, 1)) + shift_key,
+                    UNICODE(SUBSTR(text, 1, 1))
+               )
+            FROM rcte
+            WHERE text <> ''
+        )
+        SELECT
+            GROUP_CONCAT(
+                CHAR(
+                    CASE
+                    WHEN GLOB('[A-Z]', chr) AND shift > UNICODE('Z')
+                    THEN shift - UNICODE('Z') + UNICODE('A') - 1
+                    WHEN GLOB('[a-z]', chr) AND shift > UNICODE('z')
+                    THEN shift - UNICODE('z') + UNICODE('a') - 1
+                    ELSE shift
+                    END
+                ),
+                ''
+            )
+        FROM rcte
+        WHERE chr NOTNULL
+   )
+;

exercises/practice/rotational-cipher/.meta/tests.toml

@@ -0,0 +1,40 @@
+# 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.
+
+[74e58a38-e484-43f1-9466-877a7515e10f]
+description = "rotate a by 0, same output as input"
+
+[7ee352c6-e6b0-4930-b903-d09943ecb8f5]
+description = "rotate a by 1"
+
+[edf0a733-4231-4594-a5ee-46a4009ad764]
+description = "rotate a by 26, same output as input"
+
+[e3e82cb9-2a5b-403f-9931-e43213879300]
+description = "rotate m by 13"
+
+[19f9eb78-e2ad-4da4-8fe3-9291d47c1709]
+description = "rotate n by 13 with wrap around alphabet"
+
+[a116aef4-225b-4da9-884f-e8023ca6408a]
+description = "rotate capital letters"
+
+[71b541bb-819c-4dc6-a9c3-132ef9bb737b]
+description = "rotate spaces"
+
+[ef32601d-e9ef-4b29-b2b5-8971392282e6]
+description = "rotate numbers"
+
+[32dd74f6-db2b-41a6-b02c-82eb4f93e549]
+description = "rotate punctuation"
+
+[9fb93fe6-42b0-46e6-9ec1-0bf0a062d8c9]
+description = "rotate all letters"

exercises/practice/rotational-cipher/create_fixture.sql

@@ -0,0 +1,11 @@
+DROP TABLE IF EXISTS "rotational-cipher";
+CREATE TABLE "rotational-cipher" (
+    text TEXT NOT NULL,
+    shift_key INTEGER NOT NULL,
+    result TEXT
+);
+
+.mode csv
+.import ./data.csv "rotational-cipher"
+
+UPDATE "rotational-cipher" SET result = NULL;

exercises/practice/rotational-cipher/create_test_table.sql

@@ -0,0 +1,29 @@
+DROP TABLE IF EXISTS tests;
+CREATE TABLE IF NOT EXISTS tests (
+    -- uuid and description are taken from the test.toml file
+    uuid TEXT PRIMARY KEY,
+    description TEXT NOT NULL,
+    -- The following section is needed by the online test-runner
+    status TEXT DEFAULT 'fail',
+    message TEXT,
+    output TEXT,
+    test_code TEXT,
+    task_id INTEGER DEFAULT NULL,
+    -- Here are columns for the actual tests
+    text TEXT NOT NULL,
+    shift_key INTEGER NOT NULL,
+    expected TEXT NOT NULL
+);
+
+INSERT INTO tests (uuid, description, text, shift_key, expected)
+    VALUES
+        ('74e58a38-e484-43f1-9466-877a7515e10f', 'rotate a by 0, same output as input', 'a', 0, 'a'),
+        ('7ee352c6-e6b0-4930-b903-d09943ecb8f5', 'rotate a by 1', 'a', 1, 'b'),
+        ('edf0a733-4231-4594-a5ee-46a4009ad764', 'rotate a by 26, same output as input', 'a', 26, 'a'),
+        ('e3e82cb9-2a5b-403f-9931-e43213879300', 'rotate m by 13', 'm', 13, 'z'),
+        ('19f9eb78-e2ad-4da4-8fe3-9291d47c1709', 'rotate n by 13 with wrap around alphabet', 'n', 13, 'a'),
+        ('a116aef4-225b-4da9-884f-e8023ca6408a', 'rotate capital letters', 'OMG', 5, 'TRL'),
+        ('71b541bb-819c-4dc6-a9c3-132ef9bb737b', 'rotate spaces', 'O M G', 5, 'T R L'),
+        ('ef32601d-e9ef-4b29-b2b5-8971392282e6', 'rotate numbers', 'Testing 1 2 3 testing', 4, 'Xiwxmrk 1 2 3 xiwxmrk'),
+        ('32dd74f6-db2b-41a6-b02c-82eb4f93e549', 'rotate punctuation', 'Let''s eat, Grandma!', 21, 'Gzo''n zvo, Bmviyhv!'),
+        ('9fb93fe6-42b0-46e6-9ec1-0bf0a062d8c9', 'rotate all letters', 'The quick brown fox jumps over the lazy dog.', 13, 'Gur dhvpx oebja sbk whzcf bire gur ynml qbt.');

exercises/practice/rotational-cipher/data.csv

@@ -0,0 +1,10 @@
+"a",0,
+"a",1,
+"a",26,
+"m",13,
+"n",13,
+"OMG",5,
+"O M G",5,
+"Testing 1 2 3 testing",4,
+"Let's eat, Grandma!",21,
+"The quick brown fox jumps over the lazy dog.",13,

exercises/practice/rotational-cipher/rotational-cipher.sql

@@ -0,0 +1,8 @@
+-- Schema:
+-- CREATE TABLE "rotational-cipher" (
+--   text      TEXT NOT NULL,
+--   shift_key INTEGER NOT NULL,
+--   result    TEXT
+-- );
+--
+-- Task: update the rotational-cipher table and set the result based on text and shift_key.

exercises/practice/rotational-cipher/rotational-cipher_test.sql

@@ -0,0 +1,40 @@
+-- Create database:
+.read ./create_fixture.sql
+
+-- Read user student solution and save any output as markdown in user_output.md:
+.mode markdown
+.output user_output.md
+.read ./rotational-cipher.sql
+.output
+
+-- Create a clean testing environment:
+.read ./create_test_table.sql
+
+-- Comparison of user input and the tests updates the status for each test:
+UPDATE tests
+    SET status = 'pass'
+    FROM (SELECT text, shift_key, result FROM "rotational-cipher") AS actual
+    WHERE (actual.text, actual.shift_key, actual.result) =
+        (tests.text,  tests.shift_key, tests.expected);
+
+-- Update message for failed tests to give helpful information:
+UPDATE tests
+    SET message = (
+        'Result for "'
+        || PRINTF('text=%s, shift_key=%d', tests.text, tests.shift_key)
+        || '"' || ' is <' || COALESCE(actual.result, 'NULL')
+        || '> but should be <' || tests.expected || '>' )
+    FROM (SELECT text, shift_key, result FROM "rotational-cipher") AS actual
+    WHERE (actual.text, actual.shift_key) = (tests.text, tests.shift_key)
+    AND tests.status = 'fail';
+
+-- Save results to ./output.json (needed by the online test-runner)
+.mode json
+.once './output.json'
+SELECT description, status, message, output, test_code, task_id
+FROM tests;
+
+-- Display test results in readable form for the student:
+.mode table
+SELECT description, status, message
+FROM tests;