Add the proverb exercise.

config.json

@@ -139,6 +139,17 @@
         "difficulty": 2,
         "topics": ["filtering", "strings"]
       },
+      {
+        "slug": "proverb",
+        "name": "Proverb",
+        "uuid": "75519a64-8237-49e5-927f-c5974816258e",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2,
+        "topics": [
+          "strings"
+        ]
+      },
       {
         "slug": "gigasecond",
         "name": "Gigasecond",

exercises/practice/proverb/.docs/instructions.md

@@ -0,0 +1,17 @@
+# Instructions
+
+For want of a horseshoe nail, a kingdom was lost, or so the saying goes.
+
+Given a list of inputs, generate the relevant proverb. For example, given the list `["nail", "shoe", "horse", "rider", "message", "battle", "kingdom"]`, you will output the full text of this proverbial rhyme:
+
+```text
+For want of a nail the shoe was lost.
+For want of a shoe the horse was lost.
+For want of a horse the rider was lost.
+For want of a rider the message was lost.
+For want of a message the battle was lost.
+For want of a battle the kingdom was lost.
+And all for the want of a nail.
+```
+
+Note that the list of inputs may vary; your solution should be able to handle lists of arbitrary length and content. No line of the output text should be a static, unchanging string; all should vary according to the input given.

exercises/practice/proverb/.meta/config.json

@@ -0,0 +1,10 @@
+{
+  "blurb": "For want of a horseshoe nail, a kingdom was lost, or so the saying goes. Output the full text of this proverbial rhyme.",
+  "authors": ["MichaelBunker"],
+  "contributors": [],
+  "files": {
+    "solution": ["Proverb.php"],
+    "test": ["ProverbTest.php"],
+    "example": [".meta/example.php"]
+  }
+}

exercises/practice/proverb/.meta/example.php

@@ -0,0 +1,45 @@
+<?php
+
+/*
+ * By adding type hints and enabling strict type checking, code can become
+ * easier to read, self-documenting and reduce the number of potential bugs.
+ * By default, type declarations are non-strict, which means they will attempt
+ * to change the original type to match the type specified by the
+ * type-declaration.
+ *
+ * In other words, if you pass a string to a function requiring a float,
+ * it will attempt to convert the string value to a float.
+ *
+ * To enable strict mode, a single declare directive must be placed at the top
+ * of the file.
+ * This means that the strictness of typing is configured on a per-file basis.
+ * This directive not only affects the type declarations of parameters, but also
+ * a function's return type.
+ *
+ * For more info review the Concept on strict type checking in the PHP track
+ * <link>.
+ *
+ * To disable strict typing, comment out the directive below.
+ */
+
+declare(strict_types=1);
+
+class Proverb
+{
+    public static function recite(array $pieces): array
+    {
+        $verses = [];
+
+        foreach ($pieces as $index => $piece) {
+            if ($index == count($pieces) - 1) {
+                $verses[] = "And all for the want of a $pieces[0].";
+                continue;
+            }
+
+            $wanted   = $pieces[$index + 1];
+            $verses[] = "For want of a $piece the $wanted was lost.";
+        }
+
+        return $verses;
+    }
+}

exercises/practice/proverb/Proverb.php

@@ -0,0 +1,33 @@
+<?php
+
+/*
+ * By adding type hints and enabling strict type checking, code can become
+ * easier to read, self-documenting and reduce the number of potential bugs.
+ * By default, type declarations are non-strict, which means they will attempt
+ * to change the original type to match the type specified by the
+ * type-declaration.
+ *
+ * In other words, if you pass a string to a function requiring a float,
+ * it will attempt to convert the string value to a float.
+ *
+ * To enable strict mode, a single declare directive must be placed at the top
+ * of the file.
+ * This means that the strictness of typing is configured on a per-file basis.
+ * This directive not only affects the type declarations of parameters, but also
+ * a function's return type.
+ *
+ * For more info review the Concept on strict type checking in the PHP track
+ * <link>.
+ *
+ * To disable strict typing, comment out the directive below.
+ */
+
+declare(strict_types=1);
+
+class Proverb
+{
+    public static function recite()
+    {
+        throw new \Exception(sprintf('Implement the %s method', __FUNCTION__));
+    }
+}

exercises/practice/proverb/ProverbTest.php

@@ -0,0 +1,92 @@
+<?php
+
+/*
+ * By adding type hints and enabling strict type checking, code can become
+ * easier to read, self-documenting and reduce the number of potential bugs.
+ * By default, type declarations are non-strict, which means they will attempt
+ * to change the original type to match the type specified by the
+ * type-declaration.
+ *
+ * In other words, if you pass a string to a function requiring a float,
+ * it will attempt to convert the string value to a float.
+ *
+ * To enable strict mode, a single declare directive must be placed at the top
+ * of the file.
+ * This means that the strictness of typing is configured on a per-file basis.
+ * This directive not only affects the type declarations of parameters, but also
+ * a function's return type.
+ *
+ * For more info review the Concept on strict type checking in the PHP track
+ * <link>.
+ *
+ * To disable strict typing, comment out the directive below.
+ */
+
+declare(strict_types=1);
+
+class ProverbTest extends PHPUnit\Framework\TestCase
+{
+    public static function setUpBeforeClass(): void
+    {
+        require_once 'Proverb.php';
+    }
+
+    public function testNoVerses(): void
+    {
+        $pieces   = [];
+        $expected = [];
+        $this->assertEquals($expected, Proverb::recite($pieces));
+    }
+
+    public function testOneVerse(): void
+    {
+        $pieces   = ['nail'];
+        $expected = ['And all for the want of a nail.'];
+        $this->assertEquals($expected, Proverb::recite($pieces));
+    }
+
+    public function testTwoVerses(): void
+    {
+        $pieces   = ['nail', 'shoe'];
+        $expected = ['For want of a nail the shoe was lost.', 'And all for the want of a nail.'];
+        $this->assertEquals($expected, Proverb::recite($pieces));
+    }
+
+    public function testThreeVerses(): void
+    {
+        $pieces   = ['nail', 'shoe', 'horse'];
+        $expected = [
+            'For want of a nail the shoe was lost.',
+            'For want of a shoe the horse was lost.',
+            'And all for the want of a nail.'
+        ];
+        $this->assertEquals($expected, Proverb::recite($pieces));
+    }
+
+    public function testFullProverb(): void
+    {
+        $pieces   = ['nail', 'shoe', 'horse', 'rider', 'message', 'battle', 'kingdom'];
+        $expected = [
+            'For want of a nail the shoe was lost.',
+            'For want of a shoe the horse was lost.',
+            'For want of a horse the rider was lost.',
+            'For want of a rider the message was lost.',
+            'For want of a message the battle was lost.',
+            'For want of a battle the kingdom was lost.',
+            'And all for the want of a nail.'
+        ];
+        $this->assertEquals($expected, Proverb::recite($pieces));
+    }
+
+    public function testFourModernizedVerses(): void
+    {
+        $pieces   = ['pin', 'gun', 'soldier', 'battle'];
+        $expected = [
+            'For want of a pin the gun was lost.',
+            'For want of a gun the soldier was lost.',
+            'For want of a soldier the battle was lost.',
+            'And all for the want of a pin.'
+        ];
+        $this->assertEquals($expected, Proverb::recite($pieces));
+    }
+}