add brain-progression

Makefile

@@ -13,6 +13,9 @@ brain-calc:
 brain-gcd:
 	./bin/brain-gcd
 
+brain-progression:
+	./bin/brain-progression
+
 validate:
 	composer validate
 

bin/brain-progression

@@ -0,0 +1,14 @@
+#!/usr/bin/env php
+
+<?php
+
+$autoloadPath1 = __DIR__ . '/../../../autoload.php';
+$autoloadPath2 = __DIR__ . '/../vendor/autoload.php';
+
+if (file_exists($autoloadPath1)) {
+    require_once $autoloadPath1;
+} else {
+    require_once $autoloadPath2;
+}
+
+Brain\Games\Progression\play();

composer.json

@@ -21,7 +21,8 @@
             "src/Engine.php",
             "src/Games/Even.php",
             "src/Games/Calc.php",
-            "src/Games/Gcd.php"
+            "src/Games/Gcd.php",
+            "src/Games/Progression.php"
         ]
     },
     "scripts": {

src/Games/Progression.php

@@ -0,0 +1,45 @@
+<?php
+
+namespace Brain\Games\Progression;
+
+use function Brain\Engine\gameLogic;
+use function cli\line;
+use function cli\prompt;
+
+const DESCRIPTION = 'What number is missing in the progression?';
+const PROGRESSION_LENGTH = 10;
+const RANDOM_MIN = 1;
+const RANDOM_MAX = 10;
+
+function generateProgression($start, $step, $progressionLength)
+{
+    $progression = [];
+    for ($i = 0; $i < $progressionLength; $i += 1) {
+        $progression[] = $start + $step * $i;
+    }
+    return $progression;
+}
+
+function getRandomNumber()
+{
+    return rand(RANDOM_MIN, RANDOM_MAX);
+}
+
+function play()
+{
+    $generateGameData = function () {
+        $start = getRandomNumber();
+        $step = getRandomNumber();
+        $progression = generateProgression($start, $step, PROGRESSION_LENGTH);
+        $progressionWithHiddenElement = array_slice($progression, 0);
+        $hiddenElementIndex = rand(0, PROGRESSION_LENGTH - 1);
+        $progressionWithHiddenElement[$hiddenElementIndex] = '..';
+        $question = implode(' ', $progressionWithHiddenElement);
+        $answer = $progression[$hiddenElementIndex];
+
+        return [$question, "{$answer}"];
+    };
+
+    gameLogic(DESCRIPTION, $generateGameData);
+    return;
+}