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[/] [trunk/] [Libs/] [CallbackHandler-1.0/] [CallbackHandler-1.0.lua] - Rev 17

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--[[ $Id: CallbackHandler-1.0.lua 1186 2018-07-21 14:19:18Z nevcairiel $ ]]
local MAJOR, MINOR = "CallbackHandler-1.0", 7
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 Dispatch(handlers, ...)
        local index, method = next(handlers)
        if not method then return end
        repeat
                xpcall(method, errorhandler, ...)
                index, method = next(handlers, index)
        until not method
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

                Dispatch(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.

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