Simple Stat Item Framework

local mod = RegisterMod("ExampleFrameworkMod", 1)

--[==[
KubeRoot's simple stat item framework

Free to use for any purpose as long as this notice is preserved. (No need to keep the "How to use")
--]==]


--[==[
How to use:
Put everything from 'local items' to the last 'end' at the top of your mod just below your RegisterMod.
Read any comments in the code and adjust the code as written
Put your item declarations into the items table, with your item's name as the table key.

For example:

items["Mysterious fabric"] = {
    CanFly = true,
    TearFlags = 3,
    Damage = 1,
    TearColor = Color(0.9,0.9,1,0.6,0,0,0),
}

items["Pegasus Boots"] = {
    MoveSpeed = 2,
    TearFlags = 8,
    ShotSpeed = 1,
    Damage = -1,
    TearColor = Color(0.3, 1, 0.4, 1, 0, 50, 0)
}

Make sure all the items are included in a valid items.xml for your mod.


NOTE:
At the current time (18.01.2017) MaxFireDelay appears to have a broken cache evaluation - the callback
triggers, but the stat changes aren't preserved. I am not including any fixes for that for futureproofing
reasons, as well as to raise awareness of the issue.
--]==]

local items
do
    local mod = mod -- !!! CHANGE THIS IF YOUR RegisterMod VARIABLE ISN'T mod !!!

    local mt, mt2 = {}, {}
    items = setmetatable({}, mt)
    local nextCache = 0
    local game = Game()
    local stats = {
        [CacheFlag.CACHE_DAMAGE] = {"Damage"},
        [CacheFlag.CACHE_FIREDELAY] = {"MaxFireDelay"},
        [CacheFlag.CACHE_SHOTSPEED] = {"ShotSpeed"},
        [CacheFlag.CACHE_RANGE] = { "TearHeight", "TearFallingSpeed", "TearFallingAcceleration" },
        [CacheFlag.CACHE_SPEED] = {"MoveSpeed"},
        [CacheFlag.CACHE_TEARFLAG] = {"TearFlags"},
        [CacheFlag.CACHE_TEARCOLOR] = {"TearColor", "LaserColor"},
        [CacheFlag.CACHE_FLYING] = {"CanFly"},
        [CacheFlag.CACHE_LUCK] = {"Luck"},
        --[CacheFlag.CACHE_WEAPON] = ,
        --[CacheFlag.CACHE_FAMILIARS] = ,
    }
    local statLookup = {}
    for k, v in pairs(stats) do
        for _, v2 in pairs(v) do
            statLookup[v2] = k
        end
    end

    local bitwiseStats = {
        TearFlags = true
    }

    local function __players(n, i)
        i=i+1
        if i<n then
            return i, game:GetPlayer(i)
        end
    end

    local function players()
        return __players, game:GetNumPlayers(), -1
    end

    function mt:__newindex(name, item)
        local t = {}
        t.id = Isaac.GetItemIdByName(name)
        t.name = name
        t.__orig = item

        local itemflags = 0
        for flag, flagtab in pairs(stats) do
            for _, flagname in pairs(flagtab) do
                if item[flagname] then
                    itemflags = itemflags | flag
                    break
                end
            end
        end
        t.cacheflags = itemflags

        rawset(self, name, setmetatable(t, mt2))
    end

    function mt2:__index(k)
        return self.__orig[k]
    end

    function mt2:__newindex(k, v)
        local stat = statLookup[k]
        if stat then
            nextCache = nextCache | stat
            self.cacheflags = self.cacheflags | stat
        end

        self.__orig[k] = v
    end

    local isColor
    do
        local function colorTest(c)
            local _ = (c.R and c.G and c.B and c.A and c.RO and c.__mul) or error()
        end

        isColor = function(c)
            return type(c)=="userdata" and pcall(colorTest, c)
        end
    end

    local cwhite = Color(1,1,1,1,0,0,0)
    local function cloneColor(c)
        return Color.Lerp(c, cwhite, 0)
    end

    local function onEvaluateCache(_mod, ply, flag)
        for name, item in pairs(items) do
            if ply:HasCollectible(item.id) and (flag & item.cacheflags) ~= 0 then
                local n = ply:GetCollectibleNum(item.id)
                for k, v in pairs(item.__orig) do
                    if (flag & statLookup[k]) ~= 0 then
                        if type(v) == "number" then
                            if bitwiseStats[k] then
                                ply[k] = ply[k] | v
                            else
                                ply[k] = ply[k] + v * n
                            end
                        elseif isColor(v) then
                            ply[k] = cloneColor(v) * ply[k]
                        else
                            ply[k] = v
                        end
                    end
                end
            end
        end
    end

    local function onUpdate(_mod)
        if nextCache ~= 0 then
            for k, ply in players() do
                ply:AddCacheFlags(nextCache)
                ply:EvaluateItems()
            end
            nextCache = 0
        end
    end

    mod:AddCallback(ModCallbacks.MC_EVALUATE_CACHE, onEvaluateCache)
    mod:AddCallback(ModCallbacks.MC_POST_UPDATE, onUpdate)
end

items["Mysterious fabric"] = {
    CanFly = true,
    TearFlags = 3,
    Damage = 1,
    TearColor = Color(0.9,0.9,1,0.6,0,0,0),
}

items["Pegasus Boots"] = {
    MoveSpeed = 2,
    TearFlags = 8,
    ShotSpeed = 1,
    Damage = -1,
    TearColor = Color(0.3, 1, 0.4, 1, 0, 50, 0)
}

items["Pegasus Boots"].Damage = -2