[Contra NES][Memory Inspection] Enemy HP Stats research for Difficulty/Loop Challenge

contra_enemy_hp_stats_and_force_loop.lua

--[[
This script renders the enemy HP in screen + forces a difficulty/loop level

Made with the help of the followin apps & resources
bizhawk@Linux = monocomplete + libopenal1
Game Genius Addresses: https://gamehacking.org/game/29281
Contra Lua Sample Code: https://www.romhacking.net/games/137/


HP of enemies in final level
Loop lvl:    0   1   2   3   4  10  20  30  40  50  60  70  80  90 100
=======================================================================
    mouths:  7   9  11  13  15  27  47  67  87 107 127 147 167 187 207
   spiders:  5   6   7   8   9  15  25  35  45  55  65  75  85  95 105
      eggs: 30  32  34  36  38  50  70  90 110 130 150 170 190 210 230           
     heart:103 119 135 151 160 160 160 160 160 135 160 160 103 160 160
alien head:103 119 135 151 160 160 160 160 160 135 160 160 103 160 160
]]

local enemy_state = {}
function game_loop()
    -- Reading from disk file in realtime so I don't have to refresh the lua interpreter all the time
    f = io.open('/home/someone/cuack.txt', 'r')
    file_content = f:read()
    f:close()
    -- gui.text(50, 20, 'File: '.. file_content)
    -- memory.writebyte(0x31, 70) -- Hardcode Difficulty
    if file_content ~= nil then
        memory.writebyte(0x31, tonumber(file_content)) -- Difficulty on file
    end

    local difficulty = memory.readbyte(0x31)

    memory.writebyte(0xDA03, 0xA5) --Infinite Lives
    memory.writebyte(0xD467, 0xB5) -- Invincible
    memory.writebyte(0xDAD2, 0x03) -- Spread Gun after death
    memory.writebyte(0x30, 0x07) --Jump to last level

    -- -- memory.writebyte(0x07F8, 0)
    gui.text(50, 50, 'Loop#: '.. difficulty, 'white', 'yellow')

    local table = input.get()
    if table.G then
        gui.text(50, 80, 'G')
        -- memory.write_u16_le(0xD04D, 0x3B) -- Pass level on START        
    end

    if table.B then
        gui.text(50, 90, 'B')
        -- memory.writebyte(0x31, difficulty + 1)
        enemy_state = {} -- clear table of enemy states
    end

    for i = 0,0xf do -- iterating through all possible enemies
        local ENEMY_X_POS = memory.readbyte(0x033e + i)
        local ENEMY_Y_POS = memory.readbyte(0x0324 + i)
        local ENEMY_HP = memory.readbyte(0x0578 + i)
        
        if ENEMY_HP ~= 240 and ENEMY_HP ~= 0 then
            if enemy_state[i] == nil or ENEMY_HP > enemy_state[i] then
                enemy_state[i] = ENEMY_HP -- best effort way to guess max health
            end
            gui.text(ENEMY_X_POS*3.1, ENEMY_Y_POS*3.1, string.format("%d/%d", ENEMY_HP, enemy_state[i]))
        else
            enemy_state[i] = nil
        end        
    end
end

event.onframestart(game_loop)