-- $Id: LibStub.lua 76 2007-09-03 01:50:17Z mikk $
-- LibStub is a simple versioning stub meant for use in Libraries.  http://www.wowace.com/wiki/LibStub for more info
-- LibStub is hereby placed in the Public Domain
-- Credits: Kaelten, Cladhaire, ckknight, Mikk, Ammo, Nevcairiel, joshborke
local LIBSTUB_MAJOR, LIBSTUB_MINOR = "LibStub", 2  -- NEVER MAKE THIS AN SVN REVISION! IT NEEDS TO BE USABLE IN ALL REPOS!
local LibStub = _G[LIBSTUB_MAJOR]

-- Check to see is this version of the stub is obsolete
if not LibStub or LibStub.minor < LIBSTUB_MINOR then
    LibStub = LibStub or {libs = {}, minors = {} }
    _G[LIBSTUB_MAJOR] = LibStub
    LibStub.minor = LIBSTUB_MINOR

    -- LibStub:NewLibrary(major, minor)
    -- major (string) - the major version of the library
    -- minor (string or number ) - the minor version of the library
    --
    -- returns nil if a newer or same version of the lib is already present
    -- returns empty library object or old library object if upgrade is needed
    function LibStub:NewLibrary(major, minor)
        assert(type(major) == "string", "Bad argument #2 to `NewLibrary' (string expected)")
        minor = assert(tonumber(strmatch(minor, "%d+")), "Minor version must either be a number or contain a number.")

        local oldminor = self.minors[major]
        if oldminor and oldminor >= minor then return nil end
        self.minors[major], self.libs[major] = minor, self.libs[major] or {}
        return self.libs[major], oldminor
    end

    -- LibStub:GetLibrary(major, [silent])
    -- major (string) - the major version of the library
    -- silent (boolean) - if true, library is optional, silently return nil if its not found
    --
    -- throws an error if the library can not be found (except silent is set)
    -- returns the library object if found
    function LibStub:GetLibrary(major, silent)
        if not self.libs[major] and not silent then
            error(("Cannot find a library instance of %q."):format(tostring(major)), 2)
        end
        return self.libs[major], self.minors[major]
    end

    -- LibStub:IterateLibraries()
    --
    -- Returns an iterator for the currently registered libraries
    function LibStub:IterateLibraries()
        return pairs(self.libs)
    end

    setmetatable(LibStub, { __call = LibStub.GetLibrary })
end
