Module lki 

Last-Known Information (LKI) system.

Mirrors Java’s Game.copyLastState() + Game.lastStateBattlefield.

Overview

The LKI system maintains two types of snapshots to resolve trigger SVars (e.g. TriggeredCard$CardPower) using a card’s state at the time it was last on the battlefield:

1. Periodic snapshots (GameState.last_state_battlefield):

   • Captured by copy_last_state() at key checkpoints (phase transitions, before SBAs, before combat)
   • Lightweight CardSnapshot structs for all battlefield cards
   • Stale snapshots persist after cards leave (for LKI lookups)

2. Per-card LKI (Card.lki_power / lki_toughness):

   • Saved in action.rs::change_zone() when a card leaves the battlefield
   • Captures the exact power/toughness at zone-change time
   • Primary source for trigger SVars

Resolution hierarchy

When resolving TriggeredCard$CardPower / TriggeredCard$CardToughness:

1. Check card.lki_power / card.lki_toughness (captured at zone change)
2. If zero, check periodic snapshot (in case card entered after last checkpoint)
3. Fall back to zero if neither source has data

Lifecycle

Card enters battlefield
  → assign zone timestamp
  → update_lki_snapshot() creates/updates periodic snapshot

Phase transition / SBA check
  → copy_last_state() refreshes all battlefield snapshots

Card leaves battlefield (dies, exiled, etc.)
  → action.rs captures lki_power/lki_toughness
  → periodic snapshot remains (stale but valid for LKI)

Trigger fires (e.g. "When ~ dies, deal damage equal to its power")
  → resolve_lki_power() checks lki_power, then periodic snapshot
  → SpellAbility resolves with correct LKI value

Java equivalents

• Game.copyLastState() → GameState::copy_last_state()
• Game.lastStateBattlefield → GameState.last_state_battlefield
• Card.getPower() (during trigger) → resolve_lki_power()

Structs

CardSnapshot

Lightweight snapshot of a card’s state on the battlefield. Captured by GameState::copy_last_state() at key checkpoints.

Functions

resolve_lki_counter_count

Resolve LKI counter count for a trigger source card.

resolve_lki_power

Resolve LKI power for a trigger source card.

resolve_lki_toughness

Resolve LKI toughness for a trigger source card.

resolve_triggered_card_lki_property

resolve_triggered_card_lki_svar

Resolve SVar properties that explicitly ask for triggered-card LKI.