tekton/server/nakama/lua/gacha.lua

local nk = require("nakama")

local gacha = {}

-- Embedded Gacha Data from gacha_data.json
local GACHA_DATA = {
    banners = {
        star = {
            name = "Star Banner",
            currency = "star",
            pull_1_cost = 160,
            pull_10_cost = 1440,
            pity_at = 90,
            rates = {
                common = 0.60,
                uncommon = 0.25,
                rare = 0.14,
                real_prize = 0.01
            }
        },
        gold = {
            name = "Gold Banner",
            currency = "gold",
            pull_1_cost = 50,
            pull_10_cost = 450,
            pity_at = 90,
            rates = {
                common = 0.60,
                uncommon = 0.25,
                rare = 0.14,
                real_prize = 0.01
            }
        }
    },
    fragments = {
        frag_common = { name = "Common Fragment", rarity = "common", icon = "⬜" },
        frag_uncommon = { name = "Uncommon Fragment", rarity = "uncommon", icon = "🟩" },
        frag_rare = { name = "Rare Fragment", rarity = "rare", icon = "🟦" }
    },
    pools = {
        common = {"frag_common"},
        uncommon = {"frag_uncommon"},
        rare = {"frag_rare"},
        real_prize = {
            "skin_gacha_rainbow_suit",
            "skin_gacha_dragon_hat",
            "skin_gacha_phantom_gloves",
            "skin_gacha_neon_acc"
        }
    },
    real_prize_catalog = {
        skin_gacha_rainbow_suit = { name = "Rainbow Suit", category = "costume", rarity = "real_prize", character = "" },
        skin_gacha_dragon_hat = { name = "Dragon Hat", category = "head", rarity = "real_prize", character = "" },
        skin_gacha_phantom_gloves = { name = "Phantom Gloves", category = "glove", rarity = "real_prize", character = "" },
        skin_gacha_neon_acc = { name = "Neon Accessory", category = "accessory", rarity = "real_prize", character = "" }
    }
}

local function roll_rarity(rates)
    local roll = math.random()
    local cumulative = 0.0
    local rarities = {"real_prize", "rare", "uncommon", "common"}
    for _, rarity in ipairs(rarities) do
        cumulative = cumulative + (rates[rarity] or 0.0)
        if roll <= cumulative then
            return rarity
        end
    end
    return "common"
end

local function pick_from_pool(rarity)
    local pool = GACHA_DATA.pools[rarity]
    if not pool or #pool == 0 then return "" end
    return pool[math.random(1, #pool)]
end

function gacha.rpc_perform_gacha_pull(context, payload)
    if not context.user_id then error("Not authenticated") end

    local request = nk.json_decode(payload)
    local banner_id = request.banner_id
    local count = request.count or 1

    if not banner_id or banner_id == "" then error("Banner ID required") end
    if count < 1 then error("Invalid count") end

    local banner = GACHA_DATA.banners[banner_id]
    if not banner then error("Unknown banner: " .. banner_id) end

    local currency = banner.currency or "star"
    local cost = banner["pull_" .. count .. "_cost"]
    if not cost then cost = (banner.pull_1_cost or 999) * count end
    local pity_at = banner.pity_at or 90

    -- Read wallet
    local status, account = pcall(nk.account_get_id, context.user_id)
    if not status or not account then error("Could not read account") end
    
    local wallet = account.wallet
    if type(wallet) == "string" then wallet = nk.json_decode(wallet) end
    local bal = wallet[currency] or 0

    if bal < cost then
        error("Insufficient currency")
    end

    -- Read pity and fragments from storage
    local pity_counters = {}
    local fragments = {}
    local read_reqs = {
        { collection = "profiles", key = "pity_counters", user_id = context.user_id },
        { collection = "profiles", key = "fragments", user_id = context.user_id }
    }
    local status_read, read_objs = pcall(nk.storage_read, read_reqs)
    if status_read and read_objs then
        for _, obj in ipairs(read_objs) do
            if obj.key == "pity_counters" then
                pity_counters = obj.value
            elseif obj.key == "fragments" then
                fragments = obj.value
            end
        end
    end

    -- Perform pulls
    local results = {}
    local inventory_writes = {}
    local inventory_items = {}

    for i = 1, count do
        local pity = pity_counters[banner_id] or 0
        local rarity
        if pity + 1 >= pity_at then
            rarity = "real_prize"
            pity_counters[banner_id] = 0
        else
            rarity = roll_rarity(banner.rates)
            pity_counters[banner_id] = (rarity == "real_prize") and 0 or (pity + 1)
        end

        local item_id = pick_from_pool(rarity)
        
        local item_data = {}
        if rarity == "real_prize" then
            item_data = GACHA_DATA.real_prize_catalog[item_id] or {}
            
            -- Add to inventory_writes
            table.insert(inventory_writes, {
                collection = "inventory",
                key = item_id,
                user_id = context.user_id,
                value = { category = item_data.category or "accessory", purchased_at = os.date("!%Y-%m-%dT%H:%M:%S.000Z"), quantity = 1 },
                permission_read = 1,
                permission_write = 0
            })
            table.insert(inventory_items, item_id)
        else
            item_data = GACHA_DATA.fragments[item_id] or {}
            fragments[item_id] = (fragments[item_id] or 0) + 1
        end

        table.insert(results, {
            id = item_id,
            rarity = rarity,
            name = item_data.name or item_id
        })
    end

    -- Write wallet
    local changeset = {}
    changeset[currency] = -cost
    local s, err = pcall(function()
        nk.wallet_update(context.user_id, changeset, {}, true)
    end)
    if not s then error("Failed to update wallet") end

    -- Write storage (pity, fragments, inventory)
    local write_objs = {
        {
            collection = "profiles",
            key = "pity_counters",
            user_id = context.user_id,
            value = pity_counters,
            permission_read = 1,
            permission_write = 0
        },
        {
            collection = "profiles",
            key = "fragments",
            user_id = context.user_id,
            value = fragments,
            permission_read = 1,
            permission_write = 0
        }
    }
    
    for _, iw in ipairs(inventory_writes) do
        table.insert(write_objs, iw)
    end

    local s2, err2 = pcall(nk.storage_write, write_objs)
    if not s2 then error("Failed to write storage: " .. tostring(err2)) end

    return nk.json_encode({ success = true, results = results, new_pity = pity_counters[banner_id] })
end

nk.register_rpc(gacha.rpc_perform_gacha_pull, "perform_gacha_pull")

nk.logger_info("LUA TEST: gacha module loaded successfully")

return gacha