initial commit

src/battle/TurnOrder.lua

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+-- Turn order, from engine/battle/core.asm MainInBattleLoop: compare
+-- effective speed; ties are a coin flip.  QUICK_ATTACK moves first and
+-- COUNTER last (Gen 1 has only these two priority moves, checked by id).
+
+local Stats = require("src.pokemon.Stats")
+
+local TurnOrder = {}
+
+local function effectiveSpeed(battler)
+  local spd = Stats.applyStage(battler.curStats.speed,
+                               battler.stages and battler.stages.speed or 0)
+  -- ApplyBadgeStatBoosts: the SOULBADGE (bit 4) boosts speed
+  if battler.badges and battler.badges.SOULBADGE then
+    spd = math.floor(spd * 9 / 8)
+  end
+  -- paralysis quarters speed; hazeStatReset suppresses it because Haze
+  -- (haze.asm ResetStats) copied the unmodified speed over the quartered
+  -- battle stat, lifting the penalty until the next stat recompute.
+  if battler.mon.status == "PAR" and not battler.hazeStatReset then
+    spd = math.max(1, math.floor(spd / 4))
+  end
+  return spd
+end
+
+local function priority(moveId)
+  if moveId == "QUICK_ATTACK" then return 1 end
+  if moveId == "COUNTER" then return -1 end
+  return 0
+end
+
+-- Returns true when battler a moves before battler b.  invertTie flips
+-- the coin-flip result only: lockstep link battles share one RNG
+-- stream, so the guest inverts the tie roll to agree with the host on
+-- who moves first.
+function TurnOrder.firstMover(a, aMove, b, bMove, rng, invertTie)
+  rng = rng or love.math.random
+  local pa, pb = priority(aMove and aMove.id), priority(bMove and bMove.id)
+  if pa ~= pb then return pa > pb end
+  local sa, sb = effectiveSpeed(a), effectiveSpeed(b)
+  if sa ~= sb then return sa > sb end
+  local aFirst = rng(0, 1) == 0
+  if invertTie then aFirst = not aFirst end
+  return aFirst
+end
+
+TurnOrder.effectiveSpeed = effectiveSpeed
+
+return TurnOrder