[TFM-LUA] Man In The Middle

do
    local _MITM = {}

    local split = function(t, s)
        local a={}
        for i in string.gmatch(t, "[^" .. (s or "%s") .. "]+") do
            a[#a + 1] = i
        end
        return a
    end

    setmetatable(_G, {
        __index = function(self, index)
            if _MITM[index] then
                return function(...)
                    for i, v in next, {"before", "default", "after"} do
                        if _MITM[index][v] then
                            if v == "default" then
                                _MITM[index][v](...)
                            else
                                for o, a in next, _MITM[index][v] do
                                    a(...)
                                end
                            end
                        end
                    end
                end
            else
                rawget(self, index)
            end
        end,
        __newindex = function(self, index, value)
            if type(value) == "function" then
                if not _MITM[index] then
                    _MITM[index] = {}
                end

                _MITM[index].default = value
            else
                rawset(self, index, value)
            end
        end,
        __metatable = nil
    });

    function injectFunction(positionType, objectToProxy, objectToReplace)
        if type(objectToProxy) == "string" then
            local arg = split(objectToProxy, '.')

            if #arg > 1 then
                local tb = _G

                for i = 1, #arg do
                    if i == #arg then
                        local old = tb[arg[i]]
                        tb[arg[i]] = {}

                        if not _MITM[objectToProxy] then
                            _MITM[objectToProxy] = {}
                        end

                        _MITM[objectToProxy][positionType] = objectToReplace

                        if not getmetatable(tb[arg[i]]) then
                            setmetatable(tb[arg[i]], {
                                __call = function(self, ...)
                                    for o, a in next, {"before", "default", "after"} do
                                        if a == "default" and positionType ~= "default" then
                                            old(...)
                                        elseif a == positionType then
                                            _MITM[objectToProxy][positionType](old, ...)
                                        end
                                    end
                                end
                            });
                        end
                    else
                        tb = tb[arg[i]]
                    end
                end
            elseif arg[1] then
                if not _MITM[arg[1]] then
                    _MITM[arg[1]] = {}
                end

                if positionType ~= "default" and not _MITM[arg[1]][positionType] then
                    _MITM[arg[1]][positionType] = {}
                end

                if positionType == "default" then
                    _MITM[arg[1]][positionType] = objectToReplace
                else
                    _MITM[arg[1]][positionType][#_MITM[arg[1]][positionType] + 1] = objectToReplace
                end
            end
        end
    end
end

-- Example

function eventChatMessage(name, message)
    print(message)
end

injectFunction("after", "eventChatMessage", function()
    print("after!")
end)

injectFunction("default", "eventChatMessage", function()
    print("default event removed")
end)