--[[---------------------------------------------------------------------------------
 AceLibrary by Cladhaire <cladhaire@gmail.com>
 Based on the concept by Iriel <iriel@vigilance-committee.org>
 Design influenced by Tekkub <tekkub@gmail.com>

  This aims to be a standard for Ace embedded libraries, as the general stub they
  all use to register themselves.  This concept of embedded libraries came as a
  result of a number of discussions in both #wowace and #wowi-lounge.

  See http://www.iriel.org/wow/addondev/embedlibrary1.html for more information
----------------------------------------------------------------------------------]]

-- DO NOT CHANGE THESE VALUES -----------------------------
local ACELIBRARY_MAJOR = "AceLibrary"
local ACELIBRARY_MINOR = 2
-- DO NOT CHANGE THESE VALUES ------------------------------

local genv = getfenv(0)
local previous = genv[ACELIBRARY_MAJOR]
if previous and not previous:NewVersion(ACELIBRARY_MAJOR, ACELIBRARY_MINOR) then
	return
end

local mt = {}
local AceLibrary = setmetatable({}, mt)
	
-- Instance replacement method.  Handles "upgrading" to a new version
function AceLibrary:ReplaceInstance(old,new)
	for k,v in pairs(old) do old[k]=nil end
	for k,v in pairs(new) do old[k]=v end
end

-- Returns a new stub.  This allows multiple libraries to use the same stub
function AceLibrary:NewStub(name)
	local newStub = {}
	self:ReplaceInstance(newStub, self)
	newStub.versions = {}
	newStub.libName = name
	return newStub
end

-- Returns true if the supplied version would be an upgrade to the current version
-- This allows for bypass code in library declaration.

function AceLibrary:NewVersion(version, minor)
	local versionData = self.versions[version]
	if not versionData or versionData.minor < minor then return true end
end

-- Returns the version of the given library with the highest minor revision
function AceLibrary:GetInstance(version)
	if not version then
		error("You must specify a version when requesting a library instance", 2)
	end

	local versionData = self.versions[version]
	if not versionData then
		error(string.format("Cannot find a library instance of %s.", version), 2)
		return
	end
	return versionData.instance
end

-- Syntax sugar.  AceLibrary("FooBar-1.0")
mt.__call = AceLibrary.GetInstance

-- Registers a new version of a given library.  Takes the library object.
function AceLibrary:Register(newInstance)
	if not newInstance.GetLibraryVersion then return end
	local version,minor = newInstance:GetLibraryVersion()
	local versionData = self.versions[version]
	if not versionData then
		-- This is new
		versionData = { instance=newInstance, minor=minor, old={}}
		self.versions[version] = versionData
		newInstance:LibActivate(self)
		return newInstance
	end
	if minor <= versionData.minor then
		-- This one is already obsolete
		if newInstance.LibDiscard then
			newInstance:LibDiscard()
		end
		return versionData.instance
	end

	-- This is an update
	local oldInstance = versionData.instance
	local oldList = versionData.old
	versionData.instance = newInstance
	versionData.minor = minor
	local skipCopy = newInstance:LibActivate(self, oldInstance, oldList)
	table.insert(oldList, oldInstance)
	if not skipCopy then
		for i,old in ipairs(oldList) do
			self:ReplaceInstance(old, newInstance)
		end
	end
	return newInstance
end

function AceLibrary:GetLibraryVersion()
	return ACELIBRARY_MAJOR, ACELIBRARY_MINOR
end

function AceLibrary:LibActivate(stub, oldInstance, oldList)
	if not self.versions then
		if oldInstance then
			self.versions = oldInstance.versions
		else
			self.versions = {}
		end
	end
	
	-- Expose the library in the global environment
	genv[ACELIBRARY_MAJOR] = self
end

if previous then 
	previous:Register(AceLibrary)
else
	AceLibrary.versions = {}
	AceLibrary.libName = version
	AceLibrary:Register(AceLibrary)
end