--[[ $Id: CallbackHandler-1.0.lua 60697 2008-02-09 16:51:20Z nevcairiel $ ]]

local MAJOR, MINOR = "CallbackHandler-1.0", 3

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}



local type = type

local pcall = pcall

local pairs = pairs

local assert = assert

local concat = table.concat

local loadstring = loadstring

local next = next

local select = select

local type = type

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", concat(OLD_ARGS, ", ")):gsub("ARGS", concat(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, OnUsed, OnUnused)

	-- TODO: Remove this after beta has gone out

	assert(not OnUsed and not OnUnused, "ACE-80: OnUsed/OnUnused are deprecated. Callbacks are now done to registry.OnUsed and registry.OnUnused")



	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"

			if type(self)~="table" and type(self)~="string" then

				error("Usage: "..RegisterName.."(self or \"addonId\", eventname, method): 'self or addonId': table or string 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.



