loto router

-- LOTO ROUTER
-- warning: overwrites savestate 5 ("searchsave" below).
--
-- this program finds crit routes for axe knight battles in Dragon Warrior.
--
-- loads a prepared save state ("startsave") and then buffers "Command?"
-- prompts using B some number of times until attacking gives useful crits. it
-- assumes the battle is set up so that you get to attack first. the tactic is
-- to crit high, tank a hit, and then crit again, because buffering "sleep"
-- is too hard and would require L7 which is harder to manipulate.

-- startsave is a savestate on the swamp tile left of the axe knight.
-- for the battle to sync consistently, the savestate should either have the
-- hero moving right onto the axe knight tile, or be in the 16-frame
-- "hesitation" window after releasing right.
startsave = savestate.object(4)  -- save slot 4

-- searchsave is a scratch save slot used to search for the next crit buffer.
searchsave = savestate.object(5) -- save slot 5

-- the maximum crit for whatever level you are attempting this insanity at.
-- this is set for level 6 with a broad sword. (no, really, level 6.)
maxcrit = 36

-- joypad state to set before waiting
jp = {}

-- wait for n frames while pushing some buttons
function waitframes(n)
  for i=1,n do
    joypad.set(1, jp)
    emu.frameadvance()
  end
end

-- detects a critical hit.
crit = false
function detectcrit()
  crit = true
end
memory.registerexecute(0xe628, detectcrit)

-- ok, here we go.
savestate.load(startsave)
emu.speedmode("turbo")
-- walk right onto battle tile
jp.right = true
waitframes(32)
jp.right = false

-- wait for battle menu to load and poll joypad
jp.B = true
while emu.lagged() do
  waitframes(1)
end
emu.print(string.format("in battle. [%d hp]", memory.readbyte(0xe2)))

-- set to true if the battle is won.
won = false
-- count of how many times you've buffered in the current turn.
buffers = 0
-- the overall buffer route.
route = {}

while true do
  -- figure out what to do this turn.
  repeat
    -- savestate and then attack.
    savestate.save(searchsave)
    emu.print(string.format("attack after %d", buffers))
    jp.A = true
    waitframes(16)

    -- wait and see how it went.
    crit = false
    waitframes(200)
    if memory.readbyte(0xc5) == 0 then
      -- thou art dead.
      emu.print("... cod")
    elseif memory.readbytesigned(0xe2) <= 0 then
      -- we got him!
      emu.print("... rekt!")
      table.insert(route, buffers)
      won = true
      do break end
    elseif memory.readbyte(0xdf) >= 0x80 then
      -- thou art asleep.
      emu.print("... zzz")
    elseif crit == true then
      -- we got a crit, awesome.
      if memory.readbyte(0xe2) <= maxcrit then
        -- the axe knight has less hp left than our max crit, so we can kill it
        -- next turn. let's keep this one.
        emu.print(string.format("good crit@%d. [%d hp]", buffers, memory.readbyte(0xe2)))
        table.insert(route, buffers)
        buffers = 0
        -- rewind to the point of the savestate and commit it.
        savestate.load(searchsave)
        jp.A = true
        waitframes(16)
        -- loop until the menu starts polling again.
        jp.A = false
        jp.B = true
        while emu.lagged() do
          waitframes(1)
        end
        -- next turn.
        do break end
      else
        -- assume this crit is not going to cut it.
        emu.print(string.format("weak crit@%d. [%d hp]", buffers, memory.readbyte(0xe2)))
      end
    else
      -- either this was a miss or a weak hit.
      emu.print("... meh")
    end

    -- not a good attack. buffer another "command" window.
    savestate.load(searchsave)
    jp.A = false
    jp.B = true
    waitframes(16)
    while emu.lagged() do
      waitframes(1)
    end
    buffers = buffers + 1
  until true
  -- lua is totally awesome.
  if won then break end
end

-- print out the route
emu.print("courage and wit have served thee well")
for i,v in ipairs(route) do
  emu.print(string.format("- turn %d: buffer %d", i, v))
end
emu.speedmode("normal")