--[[
Purpose: Help obtaining Pokérus in Pokémon Ruby, Sapphire and Emerald.

Version: v1.0

Credits: RainingChain, Real96

License: GNU General Public License v3.0
--]] 


--[[
 Exported :
    gameVersionName: Emerald | Ruby | Sapphire
    gameRevision: "" | 1.0 | 1.2
    getCurrentAdv() => currentAdvance
    getNextRandVal() => u16
    getCurrentRandValU32() => u32
    LCRNG(s, mul, sum) => new s
--]]

if not emu then
    console:log("Error: This script must be executed while a game is running.")
    return
end

local lang = emu:read8(0x80000AF)

if lang ~= 0x45 then -- not English
    console:log("Error: Only English games supported.")
    return
end

local gameVersionId = emu:read8(0x80000AE)

local gameVersionName = emu:read8(0x80000AE)
if gameVersionId == 0x56 then
    gameVersionName = "Ruby"
elseif gameVersionId == 0x50 then
    gameVersionName = "Sapphire"
elseif gameVersionId == 0x45 then
    gameVersionName = "Emerald"
else
    console:log("Error: Only Pokémon Ruby, Sapphire and Emerald are supported.")
    return
end

local gameRevision = ""

local getCurrentAdv
local getCurrentRandValU32

function LCRNG(s, mul, sum)
    local a = (mul >> 16) * (s % 0x10000) + (s >> 16) * (mul % 0x10000)
    local b = (mul % 0x10000) * (s % 0x10000) + (a % 0x10000) * 0x10000 + sum

    return b % 0x100000000
end

local getNextRandVal = function() 
    return LCRNG(getCurrentRandValU32() >> 16, 0x6073, 0x41c64e6d)
end

if gameVersionName == "Emerald" then
    gameRevision = "1.0"
    getCurrentAdv = function()
        return emu:read32(0x020249c0)
    end
    getCurrentRandValU32 = function()
        return emu:read32(0x03005d80)
    end
end


if gameVersionName == "Ruby" or gameVersionName == "Sapphire" then

    if emu:read16(0x08040068) == 46448 then
        gameRevision = "1.2"
    elseif emu:read16(0x08040068) == 512 then
        gameRevision = "1.0"
    else
        console:log("Error: Unable to determine the Pokémon Ruby/Sapphire version.")
    end

    local JUMP_DATA = {{0x41C64E6D, 0x6073}, {0xC2A29A69, 0xE97E7B6A}, {0xEE067F11, 0x31B0DDE4},
                       {0xCFDDDF21, 0x67DBB608}, {0x5F748241, 0xCBA72510}, {0x8B2E1481, 0x1D29AE20},
                       {0x76006901, 0xBA84EC40}, {0x1711D201, 0x79F01880}, {0xBE67A401, 0x8793100},
                       {0xDDDF4801, 0x6B566200}, {0x3FFE9001, 0x803CC400}, {0x90FD2001, 0xA6B98800},
                       {0x65FA4001, 0xE6731000}, {0xDBF48001, 0x30E62000}, {0xF7E90001, 0xF1CC4000},
                       {0xEFD20001, 0x23988000}, {0xDFA40001, 0x47310000}, {0xBF480001, 0x8E620000},
                       {0x7E900001, 0x1CC40000}, {0xFD200001, 0x39880000}, {0xFA400001, 0x73100000},
                       {0xF4800001, 0xE6200000}, {0xE9000001, 0xCC400000}, {0xD2000001, 0x98800000},
                       {0xA4000001, 0x31000000}, {0x48000001, 0x62000000}, {0x90000001, 0xC4000000},
                       {0x20000001, 0x88000000}, {0x40000001, 0x10000000}, {0x80000001, 0x20000000}, {0x1, 0x40000000},
                       {0x1, 0x80000000}}

    local timerAddr = 0x3001790
    local currentSeedAddr = 0x3004818

    local tempCurrentSeed = 0

    function LCRNGDistance(state0, state1)
        local mask = 1
        local dist = 0

        if state0 ~= state1 then
            for _, data in ipairs(JUMP_DATA) do
                local mult, add = table.unpack(data)

                if state0 == state1 then
                    break
                end

                if ((state0 ~ state1) & mask) ~= 0 then
                    state0 = LCRNG(state0, mult, add)
                    dist = dist + mask
                end

                mask = mask << 1
            end

            tempCurrentSeed = state1
        end

        return dist > 999 and dist - 0x100000000 or dist
    end

    local initialSeed, advances = 0, 0

    getCurrentAdv = function()
        local timer = emu:read16(timerAddr)
        local current = emu:read32(currentSeedAddr)

        if (timer == 0 and current <= 0xFFFF) or current == timer then
            initialSeed = current
            tempCurrentSeed = current
        end

        if initialSeed == current then
            advances = 0
        else
            advances = advances + LCRNGDistance(tempCurrentSeed, current)
        end

        return advances
    end
end

function printMessage(currentAdv, targetAdv, rngVal)
    console:log("-------------------------------------------------")
    console:log("Pokérus-related code was triggered!:")
    console:log("  RNG advance when Pokérus code was triggered: " .. (currentAdv - 1))
    console:log("  RNG advance needed to obtain Pokérus: " .. targetAdv)

    local diff = targetAdv - currentAdv

    if diff == 0 then
        console:log("Congratulations! One of your Pokémon now has Pokérus!")
        return
    end

    if diff > 0 then
        console:log("  Advance difference: +" .. diff)
    else
        console:log("  Advance difference: " .. diff)
    end

    if diff % 2 ~= 0 then
        console:log("")
        console:log("Warning: The current battle can't be used to obtain Pokérus. Start another battle.")
    elseif diff > 0 then
        console:log("")
        console:log("Reload a savestate during the battle and press A " .. diff .. " advances later.")
        console:log(
            "  Ex: If the Current advance you wrote down is XXXXX: reload your savestate, press Ctrl+N until Current advance displays (XXXXX + " ..
                diff .. "), then press A + Ctrl+P.")
    else
        console:log("")
        console:log("Reload a savestate during the battle and press A " .. (-diff) .. " advances earlier.")
    end
end

local GameInfo = console:createBuffer("Pokérus")
GameInfo:setSize(100, 100)

if gameVersionName == "Emerald" then
    console:log("Pokémon Emerald detected")
    emu:setBreakpoint(function()
        printMessage(emu:read32(0x020249c0), 66611)
    end, 0x806dcbe)

    callbacks:add("frame", function()
        GameInfo:clear()
        GameInfo:print("Current advance: " .. emu:read32(0x020249c0) .. "\n" .. "Target advance for Pokérus: 66611")
    end)
end

if gameVersionName == "Ruby" or gameVersionName == "Sapphire" then
    -- https://raw.githubusercontent.com/pret/pokeruby/refs/heads/symbols/pokesapphire_rev2.sym
    local currentSeedAddr = 0x3004818
    
    -- RandomlyGivePartyPokerus
    local POKERUS_FUNC_ADDRS = {
        0x08040068, -- Ruby Rev1, Ruby Rev2, Sapphire Rev1, Sapphire Rev2,
        0x08040048 -- Ruby, Sapphire
    }
    local pokerusFuncAddr = POKERUS_FUNC_ADDRS[1]
    if gameRevision == "1.2" then
        console:log("Pokémon Ruby/Sapphire v1.1 or v1.2 detected")
    elseif gameRevision == "1.0" == 512 then
        console:log("Pokémon Ruby/Sapphire v1.0 detected")
        pokerusFuncAddr = POKERUS_FUNC_ADDRS[2]
    else
        console:log("Error: Unable to determine the Pokémon Ruby/Sapphire version.")
    end

    emu:setBreakpoint(function()
        local currentAdvances = getCurrentAdv()
        printMessage(currentAdvances, 26923)

        -- console:log("    r0=" .. string.format("%04x", emu:readRegister("r0")))
        -- console:log("    r5=" .. string.format("%04x", emu:readRegister("r5")))
    end, pokerusFuncAddr + 0x10)

    emu:setBreakpoint(function()
        local currentAdvances = getCurrentAdv()
        console:log("atkE5_pickup triggered. RNG Adv = " .. currentAdvances .. ". RNG Val = " ..
                        emu:read32(currentSeedAddr))

        -- console:log("    r0=" .. string.format("%04x", emu:readRegister("r0")))
        -- console:log("    r5=" .. string.format("%04x", emu:readRegister("r5")))
    end, 0x0802af68)

    callbacks:add("frame", function()
        local currentAdvances = getCurrentAdv()
        GameInfo:clear()
        if currentAdvances < 0 then
            GameInfo:print("Error: Unable to determine the current advance. Reset the game with Ctrl+R.")
        else
            GameInfo:print("Current advance: " .. currentAdvances .. "\n" .. "Target advance for Pokérus: 26924")
        end
    end)
end

console:log("Pokérus helper script was activated.")
console:log("")
console:log("Guide:")
console:log("  - Restart the game with Ctrl+R.")
console:log("  - Start a Pokémon battle and attack the wild Pokémon until it faints")
console:log("  - Make a savestate on the message \"XXX gained YY EXP.Points.\"")
console:log("  - Pause the game with Ctrl+P.")
console:log("  - Write down the Current advance, which is displayed on the panel above.")
console:log("  - Press A with the game paused, and while holding A, unpause the game with Ctrl+P.")
console:log("  - A message from the script will be displayed with additional steps.")
console:log(
    "  - If no message is displayed after the battle, it's possibly an issue with mGBA. Try closing and opening mGBA again.")