--[[ $Id: CallbackHandler-1.0.lua 60548 2008-02-07 11:04:06Z 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.