ctmirrors

-- ctmirrors.lua
-- Script designed for DeSmuME
-- Usage: Load the US ROM of Chrono Trigger DS, load your save, run this script, close the Lua window, then save your game
-- You now have the following:
-- Nu Arcana x7
-- Uranian Mirror x1
-- Pontic Mirror x2
-- Promethean Mirror x1
-- Aresian Mirror x2
-- Item Encyclopedia entries for all of the above

-- Lua is a terrible language and you should kill yourself if you like it

-- If modifying this script for your own purposes, you may find this Google Sheet that I've created (and am still working on) to be useful
-- https://docs.google.com/spreadsheets/d/1x0rUPHkSwbUqhCnvJYKhIgAJEVe2DUS-XyZxj1bwu5Y/pubhtml

-- memory address to start looping through, and the maximum number of 4-byte item records that can be there
local start_address = 0x02072ED4
local length = 59

-- array representing all items to add, and their item encyclopedia offsets
-- items[i][1] = Item ID
-- items[i][2] = Category ID
-- items[i][3] = quantity (max 0x63, which is 99 in decimal)
-- items[i][4] = value to be used by the code, leave it zero or Unexpected Things(tm) will happen
local items = {
    { 0x2B, 0x30, 0x07, 0 }, -- Nu Arcana x7
    { 0x2C, 0x30, 0x01, 0 }, -- Uranian Mirror x1
    { 0x2D, 0x30, 0x02, 0 }, -- Pontic Mirror x2
    { 0x2E, 0x30, 0x01, 0 }, -- Promethean Mirror x1
    { 0x2F, 0x30, 0x01, 0 }, -- Hadean Mirror x1
    { 0x30, 0x30, 0x02, 0 }  -- Aresian Mirror x2
}

-- item encyclopedia modifications to make
-- encyclopedia[i][1] = address
-- encyclopedia[i][2] = bitmask to be bitwise OR'd with the value at that address
local encyclopedia = {
    { 0x0207454A, 0xF8 }, -- Everything except the Aresian Mirror
    { 0x0207454B, 0x01 }  -- Aresian Mirror
}

-- Everything below this line is absolutely perfect (except for the fact that it's written in Lua)
-- therefore, if you modify it, you're a bad person.
-- unless you're modifying it to make it be in a different language and somehow still have it work in DeSmuME
-- in which case, you're amazing, share your Lua library that's making that possible with me so I can be free as well

-- WHY ARE LUA ARRAYS ONE-BASED
-- WHY
-- anyway, this is just to name my numeric indices so the code is more readable
local item_id = 1
local category_id = 2
local quantity = 3
local inv_slot = 4

local address = 1
local bitmask = 2

-- also I'm just going to ignore lexical scoping by declaring everything I'm using as high up as possible
-- this is because I come from real, non-toy languages where variables have to be declared at the beginning of the function
-- besides, it ain't particularly clean to be declaring variables in the middle of your code
-- also, Lua doesn't have any kind of "strict mode" and will happily let you use uninitialized variables
local idx
local itemidx = 1
local curraddr
local item

-- okay, so.
-- For some stupid reason, emulators are stuck on Lua 5.1
-- this means no bitwise operators, as found in Lua 5.3
-- to "gloss over" this, DeSmuME includes a language extension that adds a 'bit' library
-- instead of, you know, using Lua 5.3
-- yay for shoehorning in functionality that you could get by simply updating Lua?
-- anyway
-- Item encyclopedia entries, go.
-- this is actually the easy part.
for idx, item in ipairs( encyclopedia ) do
    memory.writebyte( item[address], bit.bor( memory.readbyte( item[address] ), item[bitmask] ) )
end
-- See?  Look how easy that was.

-- now the hard part, which is actually giving the items to the player
-- look to see if each item already exists
-- if it does, make a note of the address
for idx = 0, length - 1 do
    curraddr = start_address + ( idx * 4 )
    for itemidx, item in ipairs( items ) do
        if memory.readbyte( curraddr     ) == item[item_id] and
           memory.readbyte( curraddr + 1 ) == item[category_id] then
            item[inv_slot] = curraddr
        end
    end
end

-- now find an empty inventory slot for any item that the player doesn't already have
itemidx = 1
for idx = 0, length - 1 do -- see?  zero-based arrays are far more intuitive from a programming perspective
    curraddr = start_address + ( idx * 4 ) -- because then math like this (essentially pointer math) Just Works(tm) without a shitty "gotta subtract one" in there
    while itemidx <= #items and items[itemidx][inv_slot] ~= 0 do
        itemidx = itemidx + 1 -- because Lua was designed by geniuses, we can't do itemidx += 1 or itemidx++
    end
    if itemidx > #items then
        break -- exit our search early if we've got addresses for all the items
    end
    if memory.readdword( curraddr ) == 0 then
        items[itemidx][inv_slot] = curraddr -- found an empty inventory slot, store that sucker
    end
end

-- now go through and actually do things
for itemidx, item in ipairs( items ) do
    memory.writebyte( item[inv_slot]    , item[item_id] )
    memory.writebyte( item[inv_slot] + 1, item[category_id] )
    memory.writebyte( item[inv_slot] + 2, item[quantity] )
    memory.writebyte( item[inv_slot] + 3, 0x00 ) -- just for sanity's sake (mmm, sake)
end