Sheets and albums

A sticker sheet, or an album, is a set of tilttek/sets whose members are sticker codes. Define it with the sets of the application, tiers and rewards included:

use Tilttek\Sets\{Reward, SetDefinition, Tier};

$sets->define(new SetDefinition('dragons-sheet', 1, ['red-dragon', 'blue-dragon', 'green-dragon', 'gold-dragon'],
    tiers: [new Tier('first-two', required: 2)],
    rewards: [new Reward('sticker', 'dragon-queen')],
));

StickerSheets measures a sheet against the stickers a holder owns:

• progress($holder, $sheet) gives the Tilttek\Sets\Progress of the sheet, recording nothing;
• record($holder, $sheet) records the completion of the sheet and of its tiers the first time they are reached, and tilttek/sets dispatches SetCompleted and TierReached with the rewards declared.

Call record() for the sheets a sticker belongs to when you hear Event\StickerGranted. A completion is never taken back: a holder who loses a sticker keeps the sheet completed. A reward of kind sticker, as above, is the application's to grant, by Stickers::grant().