Emberfall/docs/DECISIONS.md

DECISIONS.md — Architecture Decision Log

Record any choice that deviates from or fills a gap in the docs. Newest at the bottom.

Format:

## D-NNN: Title
- Date:
- Context: (what problem / ambiguity)
- Decision: (what you chose)
- Alternatives considered:
- Consequences:

D-001: SQLite + better-sqlite3 as the datastore

• Date: (project start)
• Context: Needs persistent accounts and game state with zero setup for a local build.
• Decision: SQLite file in data/, synchronous driver, WAL mode.
• Alternatives considered: Postgres (heavier setup), JSON files (no integrity/transactions).
• Consequences: Single-process deployment; synchronous transactions give simple double-spend protection. Migrate to Postgres only if scaling beyond one server.

D-002: Lazy time evaluation instead of tick loops

• Date: (project start)
• Context: Game must progress while players are offline.
• Decision: Store timestamps; compute energy/timers on demand.
• Consequences: No background workers, trivially testable with injected clocks.

D-003: Vanilla frontend, no build step

• Date: (project start)
• Context: Reduce tooling surface area for a local-model build.
• Decision: Static HTML/CSS/JS served by Express.
• Consequences: Slightly more DOM boilerplate; far fewer moving parts.

D-004: Both combatants attack every round

• Date: 2026-10-20 (review)
• Context: Combat treated "higher speed acts first" as "only the faster side acts", so the slower side never attacked.
• Decision: Each round, both attack; faster first; hero wins speed ties; a kill ends the round.
• Consequences: Round log has up to 2 entries per round (max 40). Win rates need re-tuning (see STATUS issue 1).

D-022: Material sell prices use item-level formula

• Context: BALANCE.md says materials sell at common 2×level, uncommon 4×level, rare 8×level — but "level" was ambiguous (hero level vs item level). The code used defaultRate * heroLevel / itemMinLevel, making high-level heroes overpay and low-level heroes underpay for high-level materials.
• Decision: Use materialSellPrice(rarity, itemMinLevel) from src/game/rewards.js — price depends on the ITEM's level, not the hero's. BALANCE.md table corrected to match the formula (e.g., Drake Scale: 90g → 112g).
• Consequences: Existing shop tests that asserted hero-level prices updated; material sell prices are now consistent regardless of hero level.

D-005: Equipment stats are counted once in derived stats

• Context: maxHp added equipment VIT twice (once in totalVit, once as a separate term).
• Decision: calcDerived in src/game/stats.js is the ONLY derived-stat formula; combat and services call it.

D-006: Real SQLite session store everywhere; unref its cleanup timer

• Context: better-sqlite3-session-store ignores expired.clear:false (clear || true), so its setInterval kept tests alive; the project had used a memory store in tests, so the real store was never exercised.
• Decision: Wrap store creation so its interval is unref'd. Tests now use the real store.

D-007: src/utils/time.js is the only clock

• Decision: Services call time.now(); tests use time.setNow(). Game functions take nowMs/rng as parameters.