alpha2 (#2)

- Change multiple field matching to enum
- Implement auto-generated IDs

Reviewed-on: #2

src/AutoId.php

@@ -0,0 +1,51 @@
+<?php declare(strict_types=1);
+
+namespace BitBadger\PDODocument;
+
+use Random\RandomException;
+
+/**
+ * How automatic ID generation should be performed
+ */
+enum AutoId
+{
+    /** Do not automatically generate IDs */
+    case None;
+
+    /** New documents with a 0 ID should receive max ID plus one */
+    case Number;
+
+    /** New documents with a blank ID should receive a v4 UUID (Universally Unique Identifier) */
+    case UUID;
+
+    /** New documents with a blank ID should receive a random string (set `Configuration::$idStringLength`) */
+    case RandomString;
+
+    /**
+     * Generate a v4 UUID
+     *
+     * @return string The v4 UUID
+     * @throws RandomException If an appropriate source of randomness cannot be found
+     */
+    public static function generateUUID(): string
+    {
+        // hat tip: https://stackoverflow.com/a/15875555/276707
+        $bytes = random_bytes(16);
+
+        $bytes[6] = chr(ord($bytes[6]) & 0x0f | 0x40); // set version to 0100
+        $bytes[8] = chr(ord($bytes[8]) & 0x3f | 0x80); // set bits 6-7 to 10
+
+        return vsprintf('%s%s-%s-%s-%s-%s%s%s', str_split(bin2hex($bytes), 4));
+    }
+
+    /**
+     * Generate a random string ID
+     *
+     * @return string A string filled with the hexadecimal representation of random bytes
+     * @throws RandomException If an appropriate source of randomness cannot be found
+     */
+    public static function generateRandom(): string
+    {
+        return bin2hex(random_bytes(Configuration::$idStringLength / 2));
+    }
+}