--- A bucket to catch events in. **AceBucket-3.0** provides throttling of events that fire in bursts and
-- your addon only needs to know about the full burst.
-- 
-- This Bucket implementation works as follows:\\
--   Initially, no schedule is running, and its waiting for the first event to happen.\\
--   The first event will start the bucket, and get the scheduler running, which will collect all
--   events in the given interval. When that interval is reached, the bucket is pushed to the 
--   callback and a new schedule is started. When a bucket is empty after its interval, the scheduler is 
--   stopped, and the bucket is only listening for the next event to happen, basically back in its initial state.
-- 
-- In addition, the buckets collect information about the "arg1" argument of the events that fire, and pass those as a 
-- table to your callback. This functionality was mostly designed for the UNIT_* events.\\
-- The table will have the different values of "arg1" as keys, and the number of occurances as their value, e.g.\\
--   { ["player"] = 2, ["target"] = 1, ["party1"] = 1 }
--
-- **AceBucket-3.0** can be embeded into your addon, either explicitly by calling AceBucket:Embed(MyAddon) or by 
-- specifying it as an embeded library in your AceAddon. All functions will be available on your addon object
-- and can be accessed directly, without having to explicitly call AceBucket itself.\\
-- It is recommended to embed AceBucket, otherwise you'll have to specify a custom `self` on all calls you
-- make into AceBucket.
-- @usage
-- MyAddon = LibStub("AceAddon-3.0"):NewAddon("BucketExample", "AceBucket-3.0")
-- 
-- function MyAddon:OnEnable()
--   -- Register a bucket that listens to all the HP related events, 
--   -- and fires once per second
--   self:RegisterBucketEvent({"UNIT_HEALTH", "UNIT_MAXHEALTH"}, 1, "UpdateHealth")
-- end
--
-- function MyAddon:UpdateHealth(units)
--   if units.player then
--     print("Your HP changed!")
--   end
-- end
-- @class file
-- @name AceBucket-3.0.lua
-- @release $Id: AceBucket-3.0.lua 1185 2018-07-21 14:15:16Z nevcairiel $

local MAJOR, MINOR = "AceBucket-3.0", 4
local AceBucket, oldminor = LibStub:NewLibrary(MAJOR, MINOR)

if not AceBucket then return end -- No Upgrade needed

AceBucket.buckets = AceBucket.buckets or {}
AceBucket.embeds = AceBucket.embeds or {}

-- the libraries will be lazyly bound later, to avoid errors due to loading order issues
local AceEvent, AceTimer

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

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

local bucketCache = setmetatable({}, {__mode='k'})

--[[
	 xpcall safecall implementation
]]
local xpcall = xpcall

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

local function safecall(func, ...)
	if func then
		return xpcall(func, errorhandler, ...)
	end
end

-- FireBucket ( bucket )
--
-- send the bucket to the callback function and schedule the next FireBucket in interval seconds
local function FireBucket(bucket)
	local received = bucket.received
	
	-- we dont want to fire empty buckets
	if next(received) ~= nil then
		local callback = bucket.callback
		if type(callback) == "string" then
			safecall(bucket.object[callback], bucket.object, received)
		else
			safecall(callback, received)
		end
		
		for k in pairs(received) do
			received[k] = nil
		end
		
		-- if the bucket was not empty, schedule another FireBucket in interval seconds
		bucket.timer = AceTimer.ScheduleTimer(bucket, FireBucket, bucket.interval, bucket)
	else -- if it was empty, clear the timer and wait for the next event
		bucket.timer = nil
	end
end

-- BucketHandler ( event, arg1 )
-- 
-- callback func for AceEvent
-- stores arg1 in the received table, and schedules the bucket if necessary
local function BucketHandler(self, event, arg1)
	if arg1 == nil then
		arg1 = "nil"
	end
	
	self.received[arg1] = (self.received[arg1] or 0) + 1
	
	-- if we are not scheduled yet, start a timer on the interval for our bucket to be cleared
	if not self.timer then
		self.timer = AceTimer.ScheduleTimer(self, FireBucket, self.interval, self)
	end
end

-- RegisterBucket( event, interval, callback, isMessage )
--
-- event(string or table) - the event, or a table with the events, that this bucket listens to
-- interval(int) - time between bucket fireings
-- callback(func or string) - function pointer, or method name of the object, that gets called when the bucket is cleared
-- isMessage(boolean) - register AceEvent Messages instead of game events
local function RegisterBucket(self, event, interval, callback, isMessage)
	-- try to fetch the librarys
	if not AceEvent or not AceTimer then 
		AceEvent = LibStub:GetLibrary("AceEvent-3.0", true)
		AceTimer = LibStub:GetLibrary("AceTimer-3.0", true)
		if not AceEvent or not AceTimer then
			error(MAJOR .. " requires AceEvent-3.0 and AceTimer-3.0", 3)
		end
	end
	
	if type(event) ~= "string" and type(event) ~= "table" then error("Usage: RegisterBucket(event, interval, callback): 'event' - string or table expected.", 3) end
	if not callback then
		if type(event) == "string" then
			callback = event
		else
			error("Usage: RegisterBucket(event, interval, callback): cannot omit callback when event is not a string.", 3)
		end
	end
	if not tonumber(interval) then error("Usage: RegisterBucket(event, interval, callback): 'interval' - number expected.", 3) end
	if type(callback) ~= "string" and type(callback) ~= "function" then error("Usage: RegisterBucket(event, interval, callback): 'callback' - string or function or nil expected.", 3) end
	if type(callback) == "string" and type(self[callback]) ~= "function" then error("Usage: RegisterBucket(event, interval, callback): 'callback' - method not found on target object.", 3) end
	
	local bucket = next(bucketCache)
	if bucket then
		bucketCache[bucket] = nil
	else
		bucket = { handler = BucketHandler, received = {} }
	end
	bucket.object, bucket.callback, bucket.interval = self, callback, tonumber(interval)
	
	local regFunc = isMessage and AceEvent.RegisterMessage or AceEvent.RegisterEvent
	
	if type(event) == "table" then
		for _,e in pairs(event) do
			regFunc(bucket, e, "handler")
		end
	else
		regFunc(bucket, event, "handler")
	end
	
	local handle = tostring(bucket)
	AceBucket.buckets[handle] = bucket
	
	return handle
end

--- Register a Bucket for an event (or a set of events)
-- @param event The event to listen for, or a table of events.
-- @param interval The Bucket interval (burst interval)
-- @param callback The callback function, either as a function reference, or a string pointing to a method of the addon object.
-- @return The handle of the bucket (for unregistering)
-- @usage
-- MyAddon = LibStub("AceAddon-3.0"):NewAddon("MyAddon", "AceBucket-3.0")
-- MyAddon:RegisterBucketEvent("BAG_UPDATE", 0.2, "UpdateBags")
-- 
-- function MyAddon:UpdateBags()
--   -- do stuff
-- end
function AceBucket:RegisterBucketEvent(event, interval, callback)
	return RegisterBucket(self, event, interval, callback, false)
end

--- Register a Bucket for an AceEvent-3.0 addon message (or a set of messages)
-- @param message The message to listen for, or a table of messages.
-- @param interval The Bucket interval (burst interval)
-- @param callback The callback function, either as a function reference, or a string pointing to a method of the addon object.
-- @return The handle of the bucket (for unregistering)
-- @usage
-- MyAddon = LibStub("AceAddon-3.0"):NewAddon("MyAddon", "AceBucket-3.0")
-- MyAddon:RegisterBucketEvent("SomeAddon_InformationMessage", 0.2, "ProcessData")
-- 
-- function MyAddon:ProcessData()
--   -- do stuff
-- end
function AceBucket:RegisterBucketMessage(message, interval, callback)
	return RegisterBucket(self, message, interval, callback, true)
end

--- Unregister any events and messages from the bucket and clear any remaining data.
-- @param handle The handle of the bucket as returned by RegisterBucket*
function AceBucket:UnregisterBucket(handle)
	local bucket = AceBucket.buckets[handle]
	if bucket then
		AceEvent.UnregisterAllEvents(bucket)
		AceEvent.UnregisterAllMessages(bucket)
		
		-- clear any remaining data in the bucket
		for k in pairs(bucket.received) do
			bucket.received[k] = nil
		end
		
		if bucket.timer then
			AceTimer.CancelTimer(bucket, bucket.timer)
			bucket.timer = nil
		end
		
		AceBucket.buckets[handle] = nil
		-- store our bucket in the cache
		bucketCache[bucket] = true
	end
end

--- Unregister all buckets of the current addon object (or custom "self").
function AceBucket:UnregisterAllBuckets()
	-- hmm can we do this more efficient? (it is not done often so shouldn't matter much)
	for handle, bucket in pairs(AceBucket.buckets) do
		if bucket.object == self then
			AceBucket.UnregisterBucket(self, handle)
		end
	end
end



-- embedding and embed handling
local mixins = {
	"RegisterBucketEvent",
	"RegisterBucketMessage", 
	"UnregisterBucket",
	"UnregisterAllBuckets",
} 

-- Embeds AceBucket into the target object making the functions from the mixins list available on target:..
-- @param target target object to embed AceBucket in
function AceBucket:Embed( target )
	for _, v in pairs( mixins ) do
		target[v] = self[v]
	end
	self.embeds[target] = true
	return target
end

function AceBucket:OnEmbedDisable( target )
	target:UnregisterAllBuckets()
end

for addon in pairs(AceBucket.embeds) do
	AceBucket:Embed(addon)
end
