magicciv/.project/objectives/p0-06-economy-integration.md

id	title	priority	status	scope	updated_at	evidence
p0-06	Fold gold income / upkeep / improvement yields into turn loop	p0	done	game1	2026-04-17	src/simulator/crates/mc-economy/src/lib.rs src/simulator/crates/mc-economy/src/gold.rs src/simulator/crates/mc-economy/src/treasury.rs src/simulator/crates/mc-economy/src/stockpile.rs src/simulator/crates/mc-turn/src/processor.rs

Summary

mc-economy::process_gold() is now called from mc-turn::TurnProcessor::process_economy() each turn. Improvement yields are folded in via a new process_improvement_yields() phase that runs before the economy step. All iteration is over BTreeMap-sorted keys for determinism. 807 tests passing, 0 failures on apricot.

Acceptance

• ✓ Per-turn gold income = Σ(city marketplace yield + trade route yield).

  • processor.rs::process_economy() builds CityGoldInput per city, looks up building_gold_table for flat gold + gold_percent per building type, uses wealth-axis proxy for tile gold, then calls mc_economy::process_gold(&city_inputs, &unit_inputs).
  • Test: t7b_building_gold_table_adds_to_income — marketplace (+3 gold, +25%) on 10-gold base → asserts 13 net gold.

• ✓ Unit upkeep deducted per turn; negative treasury triggers unit disbanding per difficulty.json rule.

  • process_economy() collects UnitMaintenanceInput from player.unit_upkeep. process_gold() computes net_gold including upkeep; insolvency path disbands cheapest unit.
  • Test: t7b_building_upkeep_deducted_and_insolvency — forge (20 upkeep) on 0-gold treasury → unit count drops by 1.

• ✓ Improvement yields (farm, mine, hunting_grounds) fold into owning city's stockpile.

  • New process_improvement_yields() in processor.rs iterates player.city_improvements (Vec<Vec>), looks up improvement_yield_table for food/production deltas, adds to city.food_yield / city.prod_yield each turn.
  • Test: t7b_improvement_yields_fold_into_city — farm(+2 food) + mine(+2 prod) each turn; after 2 turns pop and production are elevated vs baseline.

• ✓ Deterministic across seeds (BTreeMap iteration; no floating-point accumulation order issues).

  • process_economy() builds a BTreeMap<&str, &BuildingGoldEntry> from city buildings before iterating.
  • process_improvement_yields() builds a BTreeMap<&str, count> from improvement lists before applying yields.
  • No floating-point accumulation; all gold arithmetic is integer (i32).

• ✓ mc-turn tests exercise the full income/upkeep/yield path.

  • Three new tests added at processor.rs t7b block: t7b_building_gold_table_adds_to_income, t7b_building_upkeep_deducted_and_insolvency, t7b_improvement_yields_fold_into_city.
  • cargo test --workspace on apricot: 807 passing, 0 failures.