Allow resetting password through email.

This also adopts the use of an Alert template for error and success messages.

models/Authentication.php

@@ -44,6 +44,31 @@ class Authentication
 		return empty($res) ? false : $res;
 	}
 
+	public static function setResetKey($id_user)
+	{
+		return Registry::get('db')->query('
+			UPDATE users
+			SET reset_key = {string:key}
+			WHERE id_user = {int:id}',
+			[
+				'id' => $id_user,
+				'key' => self::newActivationKey(),
+			]);
+	}
+
+	public static function checkResetKey($id_user, $reset_key)
+	{
+		$key = Registry::get('db')->queryValue('
+			SELECT reset_key
+			FROM users
+			WHERE id_user = {int:id}',
+			[
+				'id' => $id_user,
+			]);
+
+		return $key == $reset_key;
+	}
+
 	/**
 	 * Verifies whether the user is currently logged in.
 	 */
@@ -62,6 +87,18 @@ class Authentication
 		return isset($_SESSION['user_id']) && self::checkExists($_SESSION['user_id']);
 	}
 
+	/**
+	 * Generates a new activation key.
+	 */
+	public static function newActivationKey()
+	{
+		$alpha = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
+		$string = '';
+		for ($i = 0; $i < 16; $i++)
+			$string .= $alpha[mt_rand(0, strlen($alpha) - 1)];
+		return $string;
+	}
+
 	/**
 	 * Checks a password for a given username against the database.
 	 */