mtg-online-drafter/docs/development/devlog/2025-12-17-140000_fix_expansion_generation.md

Fix Expansion Pack Generation (Infinite Cards)

Problem

The user reported two issues with "From Expansion" pack generation:

1. Incorrect amount of packs generated (e.g., 10 instead of 36).
2. The generator was using a finite pool of cards (like a custom cube) instead of an infinite supply (like opening fresh packs).

Root Cause

The PackGeneratorService defaults to generating packs without replacement (withReplacement: false). This means once a card is used, it is removed from the pool. For a standard set (Expansion), the pool contains only one copy of each card (from Scryfall fetch). When generating a large number of packs (e.g., 36 for a box), the rare/mythic/uncommon pools would deplete quickly, causing the generator to stop early and produce fewer packs than requested.

Solution

Modified src/server/index.ts to enforce settings.withReplacement = true when sourceMode === 'set'. This ensures that:

• The pack generator refreshes the card pools for every new pack.
• Generating 36 packs (or any number) is possible even from a single set of source cards.
• Duplicates are allowed across packs (simulating a print run), while maintaining uniqueness within a single pack (handled by buildSinglePack).

Changes

• File: src/server/index.ts
• Logic: Added a check in the /api/packs/generate route to set settings.withReplacement = true if sourceMode === 'set'.