DiesalLibs/CallbackHandler-1.0/CallbackHandler-1.0.lua

--[[ $Id: CallbackHandler-1.0.lua 18 2014-10-16 02:52:20Z mikk $ ]]

local MAJOR, MINOR = "CallbackHandler-1.0", 6
local CallbackHandler = LibStub:NewLibrary(MAJOR, MINOR)

if not CallbackHandler then
    return
end -- No upgrade needed

local meta = {
    __index = function(tbl, key)
        tbl[key] = {}
        return tbl[key]
    end,
}

-- Lua APIs
local tconcat = table.concat
local assert, error, loadstring = assert, error, loadstring
local setmetatable, rawset, rawget = setmetatable, rawset, rawget
local next, select, pairs, type, tostring = next, select, pairs, type, tostring

-- Global vars/functions that we don't upvalue since they might get hooked, or upgraded
-- List them here for Mikk's FindGlobals script
-- GLOBALS: geterrorhandler

local xpcall = xpcall

local function errorhandler(err)
    return geterrorhandler()(err)
end

local function CreateDispatcher(argCount)
    local code = [[
	local next, xpcall, eh = ...

	local method, ARGS
	local function call() method(ARGS) end

	local function dispatch(handlers, ...)
		local index
		index, method = next(handlers)
		if not method then return end
		local OLD_ARGS = ARGS
		ARGS = ...
		repeat
			xpcall(call, eh)
			index, method = next(handlers, index)
		until not method
		ARGS = OLD_ARGS
	end

	return dispatch
	]]

    local ARGS, OLD_ARGS = {}, {}
    for i = 1, argCount do
        ARGS[i], OLD_ARGS[i] = "arg" .. i, "old_arg" .. i
    end
    code = code:gsub("OLD_ARGS", tconcat(OLD_ARGS, ", ")):gsub("ARGS", tconcat(ARGS, ", "))
    return assert(loadstring(code, "safecall Dispatcher[" .. argCount .. "]"))(next, xpcall, errorhandler)
end

local Dispatchers = setmetatable({}, {
    __index = function(self, argCount)
        local dispatcher = CreateDispatcher(argCount)
        rawset(self, argCount, dispatcher)
        return dispatcher
    end,
})

--------------------------------------------------------------------------
-- CallbackHandler:New
--
--   target            - target object to embed public APIs in
--   RegisterName      - name of the callback registration API, default "RegisterCallback"
--   UnregisterName    - name of the callback unregistration API, default "UnregisterCallback"
--   UnregisterAllName - name of the API to unregister all callbacks, default "UnregisterAllCallbacks". false == don't publish this API.

function CallbackHandler:New(target, RegisterName, UnregisterName, UnregisterAllName)
    RegisterName = RegisterName or "RegisterCallback"
    UnregisterName = UnregisterName or "UnregisterCallback"
    if UnregisterAllName == nil then -- false is used to indicate "don't want this method"
        UnregisterAllName = "UnregisterAllCallbacks"
    end

    -- we declare all objects and exported APIs inside this closure to quickly gain access
    -- to e.g. function names, the "target" parameter, etc

    -- Create the registry object
    local events = setmetatable({}, meta)
    local registry = { recurse = 0, events = events }

    -- registry:Fire() - fires the given event/message into the registry
    function registry:Fire(eventname, ...)
        if not rawget(events, eventname) or not next(events[eventname]) then
            return
        end
        local oldrecurse = registry.recurse
        registry.recurse = oldrecurse + 1

        Dispatchers[select("#", ...) + 1](events[eventname], eventname, ...)

        registry.recurse = oldrecurse

        if registry.insertQueue and oldrecurse == 0 then
            -- Something in one of our callbacks wanted to register more callbacks; they got queued
            for eventname, callbacks in pairs(registry.insertQueue) do
                local first = not rawget(events, eventname) or not next(events[eventname]) -- test for empty before. not test for one member after. that one member may have been overwritten.
                for self, func in pairs(callbacks) do
                    events[eventname][self] = func
                    -- fire OnUsed callback?
                    if first and registry.OnUsed then
                        registry.OnUsed(registry, target, eventname)
                        first = nil
                    end
                end
            end
            registry.insertQueue = nil
        end
    end

    -- Registration of a callback, handles:
    --   self["method"], leads to self["method"](self, ...)
    --   self with function ref, leads to functionref(...)
    --   "addonId" (instead of self) with function ref, leads to functionref(...)
    -- all with an optional arg, which, if present, gets passed as first argument (after self if present)
    target[RegisterName] = function(
        self,
        eventname,
        method,
        ... --[[actually just a single arg]]
    )
        if type(eventname) ~= "string" then
            error("Usage: " .. RegisterName .. "(eventname, method[, arg]): 'eventname' - string expected.", 2)
        end

        method = method or eventname

        local first = not rawget(events, eventname) or not next(events[eventname]) -- test for empty before. not test for one member after. that one member may have been overwritten.

        if type(method) ~= "string" and type(method) ~= "function" then
            error("Usage: " .. RegisterName .. '("eventname", "methodname"): \'methodname\' - string or function expected.', 2)
        end

        local regfunc

        if type(method) == "string" then
            -- self["method"] calling style
            if type(self) ~= "table" then
                error("Usage: " .. RegisterName .. '("eventname", "methodname"): self was not a table?', 2)
            elseif self == target then
                error("Usage: " .. RegisterName .. '("eventname", "methodname"): do not use Library:' .. RegisterName .. "(), use your own 'self'", 2)
            elseif type(self[method]) ~= "function" then
                error("Usage: " .. RegisterName .. '("eventname", "methodname"): \'methodname\' - method \'' .. tostring(method) .. "' not found on self.", 2)
            end

            if select("#", ...) >= 1 then -- this is not the same as testing for arg==nil!
                local arg = select(1, ...)
                regfunc = function(...)
                    self[method](self, arg, ...)
                end
            else
                regfunc = function(...)
                    self[method](self, ...)
                end
            end
        else
            -- function ref with self=object or self="addonId" or self=thread
            if type(self) ~= "table" and type(self) ~= "string" and type(self) ~= "thread" then
                error("Usage: " .. RegisterName .. "(self or \"addonId\", eventname, method): 'self or addonId': table or string or thread expected.", 2)
            end

            if select("#", ...) >= 1 then -- this is not the same as testing for arg==nil!
                local arg = select(1, ...)
                regfunc = function(...)
                    method(arg, ...)
                end
            else
                regfunc = method
            end
        end

        if events[eventname][self] or registry.recurse < 1 then
            -- if registry.recurse<1 then
            -- we're overwriting an existing entry, or not currently recursing. just set it.
            events[eventname][self] = regfunc
            -- fire OnUsed callback?
            if registry.OnUsed and first then
                registry.OnUsed(registry, target, eventname)
            end
        else
            -- we're currently processing a callback in this registry, so delay the registration of this new entry!
            -- yes, we're a bit wasteful on garbage, but this is a fringe case, so we're picking low implementation overhead over garbage efficiency
            registry.insertQueue = registry.insertQueue or setmetatable({}, meta)
            registry.insertQueue[eventname][self] = regfunc
        end
    end

    -- Unregister a callback
    target[UnregisterName] = function(self, eventname)
        if not self or self == target then
            error("Usage: " .. UnregisterName .. "(eventname): bad 'self'", 2)
        end
        if type(eventname) ~= "string" then
            error("Usage: " .. UnregisterName .. "(eventname): 'eventname' - string expected.", 2)
        end
        if rawget(events, eventname) and events[eventname][self] then
            events[eventname][self] = nil
            -- Fire OnUnused callback?
            if registry.OnUnused and not next(events[eventname]) then
                registry.OnUnused(registry, target, eventname)
            end
        end
        if registry.insertQueue and rawget(registry.insertQueue, eventname) and registry.insertQueue[eventname][self] then
            registry.insertQueue[eventname][self] = nil
        end
    end

    -- OPTIONAL: Unregister all callbacks for given selfs/addonIds
    if UnregisterAllName then
        target[UnregisterAllName] = function(...)
            if select("#", ...) < 1 then
                error("Usage: " .. UnregisterAllName .. "([whatFor]): missing 'self' or \"addonId\" to unregister events for.", 2)
            end
            if select("#", ...) == 1 and ... == target then
                error("Usage: " .. UnregisterAllName .. "([whatFor]): supply a meaningful 'self' or \"addonId\"", 2)
            end

            for i = 1, select("#", ...) do
                local self = select(i, ...)
                if registry.insertQueue then
                    for eventname, callbacks in pairs(registry.insertQueue) do
                        if callbacks[self] then
                            callbacks[self] = nil
                        end
                    end
                end
                for eventname, callbacks in pairs(events) do
                    if callbacks[self] then
                        callbacks[self] = nil
                        -- Fire OnUnused callback?
                        if registry.OnUnused and not next(callbacks) then
                            registry.OnUnused(registry, target, eventname)
                        end
                    end
                end
            end
        end
    end

    return registry
end

-- CallbackHandler purposefully does NOT do explicit embedding. Nor does it
-- try to upgrade old implicit embeds since the system is selfcontained and
-- relies on closures to work.