initial commit

src/battle/Catching.lua

@@ -0,0 +1,66 @@
+-- Gen 1 catch algorithm (engine/items/item_effects.asm, ItemUseBall).
+
+local Catching = {}
+
+local BALL_RAND_MAX = { MASTER_BALL = 0, POKE_BALL = 255, GREAT_BALL = 200,
+                        ULTRA_BALL = 150, SAFARI_BALL = 150 }
+local BALL_HP_FACTOR = { POKE_BALL = 12, GREAT_BALL = 8, ULTRA_BALL = 12,
+                         SAFARI_BALL = 12 }
+
+-- Returns caught, shakes (0-3).  rateOverride replaces the species catch
+-- rate (the Safari game's BAIT/ROCK-modified wEnemyMonActualCatchRate).
+--
+-- On failure the ball wobbles per the original's shake calculation:
+-- Y = rate*100/ballFactor2 (255/200/150), Z = X*Y/255 + status2 (5/10)
+-- where X is the HP factor; Z<10: 0 shakes, <30: 1, <70: 2, else 3.
+-- (We use the HP factor for X on both failure paths; the original reads
+-- a stale quotient when the first roll fails.)
+function Catching.attempt(ball, targetMon, targetDef, rng, rateOverride)
+  rng = rng or love.math.random
+  if ball == "MASTER_BALL" then return true, 3 end
+  local randMax = BALL_RAND_MAX[ball] or 255
+  local rate = rateOverride or targetDef.catchRate
+
+  local statusBonus = 0
+  local s = targetMon.status
+  if s == "SLP" or s == "FRZ" then
+    statusBonus = 25
+  elseif s == "PSN" or s == "BRN" or s == "PAR" then
+    statusBonus = 12
+  end
+
+  -- HP factor (X)
+  local maxhp = targetMon.stats.hp
+  local hpQuarter = math.max(1, math.floor(targetMon.hp / 4))
+  local factor = BALL_HP_FACTOR[ball] or 12
+  -- the 255 cap applies only after BOTH divisions (ItemUseBall keeps
+  -- the intermediate in 16 bits); capping early collapses the value
+  local f = math.min(255, math.floor(math.floor(maxhp * 255 / factor) / hpQuarter))
+
+  local function shakes()
+    local ballFactor2 = ball == "POKE_BALL" and 255
+                        or ball == "GREAT_BALL" and 200 or 150
+    local y = math.floor(rate * 100 / ballFactor2)
+    local z
+    if y > 255 then
+      z = 255
+    else
+      z = math.floor(f * y / 255)
+    end
+    if s == "SLP" or s == "FRZ" then
+      z = z + 10
+    elseif s then
+      z = z + 5
+    end
+    if z < 10 then return 0 elseif z < 30 then return 1
+    elseif z < 70 then return 2 else return 3 end
+  end
+
+  local r = rng(0, randMax) - statusBonus
+  if r < 0 then return true, 3 end
+  if r > rate then return false, shakes() end
+  if rng(0, 255) <= f then return true, 3 end
+  return false, shakes()
+end
+
+return Catching