Difference between revisions of "Module:Category handler"

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----------------------------------------------------------------------
+
--------------------------------------------------------------------------------
--                                                                 --
+
--                                                                           --
--                         CATEGORY HANDLER                         --
+
--                             CATEGORY HANDLER                             --
--                                                                 --
+
--                                                                           --
--      This module implements the {{category handler}} template   --
+
--      This module implements the {{category handler}} template in Lua,      --
--      in Lua, with a few improvements: all namespaces and all    --
+
--      with a few improvements: all namespaces and all namespace aliases     --
--      namespace aliases are supported, and namespace names are   --
+
--      are supported, and namespace names are detected automatically for    --
--      detected automatically for the local wiki. This module      --
+
--      the local wiki. This module requires [[Module:Namespace detect]]     --
--      requires [[Module:Namespace detect]] to be available on    --
+
--      and [[Module:Yesno]] to be available on the local wiki. It can be     --
--      the local wiki. It can be configured for different wikis   --
+
--      configured for different wikis by altering the values in              --
--      by altering the values in the "cfg" table.                 --
+
--      [[Module:Category handler/config]], and pages can be blacklisted      --
--                                                                 --
+
--      from categorisation by using [[Module:Category handler/blacklist]].   --
----------------------------------------------------------------------
+
--                                                                           --
 +
--------------------------------------------------------------------------------
  
----------------------------------------------------------------------
+
-- Load required modules
--                      Configuration data                          --
+
local yesno = require('Module:Yesno')
--      Language-specific parameter names and values can be set    --
 
--      here.                                                      --
 
----------------------------------------------------------------------
 
  
local cfg = {}
+
-- Lazily load things we don't always need
 +
local mShared, mappings
  
-- cfg.nocat is the parameter name to suppress categorisation.
+
local p = {}
-- cfg.nocatTrue is the value to suppress categorisation, and
 
-- cfg.nocatFalse is the value to both categorise and to skip the
 
-- blacklist check.
 
cfg.nocat = 'nocat'   
 
cfg.nocatTrue = 'true'
 
cfg.nocatFalse = 'false'
 
  
-- The parameter name for the legacy "categories" parameter. This
+
--------------------------------------------------------------------------------
-- skips the blacklist if set to the cfg.category2Yes value, and
+
-- Helper functions
-- suppresses categorisation if set to the cfg.categoriesNo value.
+
--------------------------------------------------------------------------------
cfg.categories = 'categories'
 
cfg.categoriesYes = 'yes'
 
cfg.categoriesNo = 'no'
 
  
-- The parameter name for the legacy "category2" parameter. This
+
local function trimWhitespace(s, removeBlanks)
-- skips the blacklist if set to the cfg.category2Yes value, and
+
if type(s) ~= 'string' then
-- suppresses categorisation if present but equal to anything other
+
return s
-- than cfg.category2Yes or cfg.category2Negative.
+
end
cfg.category2 = 'category2'
+
s = s:match('^%s*(.-)%s*$')
cfg.category2Yes = 'yes'
+
if removeBlanks then
cfg.category2Negative = '¬'
+
if s ~= '' then
 +
return s
 +
else
 +
return nil
 +
end
 +
else
 +
return s
 +
end
 +
end
  
-- cfg.subpage is the parameter name to specify how to behave on
+
--------------------------------------------------------------------------------
-- subpages. cfg.subpageNo is the value to specify to not
+
-- CategoryHandler class
-- categorise on subpages; cfg.only is the value to specify to only
+
--------------------------------------------------------------------------------
-- categorise on subpages.
 
cfg.subpage = 'subpage'
 
cfg.subpageNo = 'no'
 
cfg.subpageOnly = 'only'
 
  
-- The parameter for data to return in all namespaces.
+
local CategoryHandler = {}
cfg.all = 'all'
+
CategoryHandler.__index = CategoryHandler
  
-- The parameter name for data to return if no data is specified for
+
function CategoryHandler.new(data, args)
-- the namespace that is detected. This must be the same as the
+
local obj = setmetatable({ _data = data, _args = args }, CategoryHandler)
-- cfg.other parameter in [[Module:Namespace detect]].
+
cfg.other = 'other'
+
-- Set the title object
 +
do
 +
local pagename = obj:parameter('demopage')
 +
local success, titleObj
 +
if pagename then
 +
success, titleObj = pcall(mw.title.new, pagename)
 +
end
 +
if success and titleObj then
 +
obj.title = titleObj
 +
if titleObj == mw.title.getCurrentTitle() then
 +
obj._usesCurrentTitle = true
 +
end
 +
else
 +
obj.title = mw.title.getCurrentTitle()
 +
obj._usesCurrentTitle = true
 +
end
 +
end
  
-- The parameter name used to specify a page other than the current
+
-- Set suppression parameter values
-- page; used for testing and demonstration. This must be the same
+
for _, key in ipairs{'nocat', 'categories'} do
-- as the cfg.page parameter in [[Module:Namespace detect]].
+
local value = obj:parameter(key)
cfg.page = 'page'
+
value = trimWhitespace(value, true)
 +
obj['_' .. key] = yesno(value)
 +
end
 +
do
 +
local subpage = obj:parameter('subpage')
 +
local category2 = obj:parameter('category2')
 +
if type(subpage) == 'string' then
 +
subpage = mw.ustring.lower(subpage)
 +
end
 +
if type(category2) == 'string' then
 +
subpage = mw.ustring.lower(category2)
 +
end
 +
obj._subpage = trimWhitespace(subpage, true)
 +
obj._category2 = trimWhitespace(category2) -- don't remove blank values
 +
end
 +
return obj
 +
end
  
-- The categorisation blacklist. Pages that match Lua patterns in this
+
function CategoryHandler:parameter(key)
-- list will not be categorised unless any of the following options are
+
local parameterNames = self._data.parameters[key]
-- set: "nocat=false", "categories=yes", or "category2=yes".
+
local pntype = type(parameterNames)
-- If the namespace name has a space in, it must be written with an
+
if pntype == 'string' or pntype == 'number' then
-- underscore, e.g. "Wikipedia_talk". Other parts of the title can have
+
return self._args[parameterNames]
-- either underscores or spaces.
+
elseif pntype == 'table' then
cfg.blacklist = {
+
for _, name in ipairs(parameterNames) do
    '^Main Page$', -- don't categorise the main page.
+
local value = self._args[name]
   
+
if value ~= nil then
    -- Don't categorise the following pages or their subpages.
+
return value
    '^Wikipedia:Cascade%-protected items$',
+
end
    '^Wikipedia:Cascade%-protected items/.*$',
+
end
    '^User:UBX$', -- The userbox "template" space.
+
return nil
    '^User:UBX/.*$',
+
else
    '^User_talk:UBX$',
+
error(string.format(
    '^User_talk:UBX/.*$',
+
'invalid config key "%s"',
   
+
tostring(key)
    -- Don't categorise subpages of these pages, but allow
+
), 2)
    -- categorisation of the base page.
+
end
    '^Wikipedia:Template messages/.+$',
+
end
   
 
    '/[aA]rchive' -- Don't categorise archives.
 
}
 
  
-- This is a table of namespaces to categorise by default. They
+
function CategoryHandler:isSuppressedByArguments()
-- should be in the format of parameter names accepted by
+
return
-- [[Module:Namespace detect]].
+
-- See if a category suppression argument has been set.
cfg.defaultNamespaces = {
+
self._nocat == true
    'main',
+
or self._categories == false
    'file',
+
or (
    'help',
+
self._category2
    'category'
+
and self._category2 ~= self._data.category2Yes
}
+
and self._category2 ~= self._data.category2Negative
 +
)
  
----------------------------------------------------------------------
+
-- Check whether we are on a subpage, and see if categories are
--                    End configuration data                      --
+
-- suppressed based on our subpage status.
----------------------------------------------------------------------
+
or self._subpage == self._data.subpageNo and self.title.isSubpage
 +
or self._subpage == self._data.subpageOnly and not self.title.isSubpage
 +
end
  
-- Get [[Module:Namespace detect]] and declare the table of functions
+
function CategoryHandler:shouldSkipBlacklistCheck()
-- that we will return.
+
-- Check whether the category suppression arguments indicate we
local NamespaceDetect = require('Module:Namespace detect')
+
-- should skip the blacklist check.
local p = {}
+
return self._nocat == false
 +
or self._categories == true
 +
or self._category2 == self._data.category2Yes
 +
end
  
----------------------------------------------------------------------
+
function CategoryHandler:matchesBlacklist()
--                        Local functions                          --
+
if self._usesCurrentTitle then
--      The following are internal functions, which we do not want  --
+
return self._data.currentTitleMatchesBlacklist
--      to be accessible from other modules.                       --
+
else
----------------------------------------------------------------------
+
mShared = mShared or require('Module:Category handler/shared')
 +
return mShared.matchesBlacklist(
 +
self.title.prefixedText,
 +
mw.loadData('Module:Category handler/blacklist')
 +
)
 +
end
 +
end
  
-- Find whether we need to return a category or not.
+
function CategoryHandler:isSuppressed()
local function needsCategory( pageObject, args )
+
-- Find if categories are suppressed by either the arguments or by
    -- Don't categorise if the relevant options are set.
+
-- matching the blacklist.
    if args[cfg.nocat] == cfg.nocatTrue
+
return self:isSuppressedByArguments()
        or args[cfg.categories] == cfg.categoriesNo
+
or not self:shouldSkipBlacklistCheck() and self:matchesBlacklist()
        or ( args[cfg.category2]
 
            and args[cfg.category2] ~= cfg.category2Yes
 
            and args[cfg.category2] ~= cfg.category2Negative )
 
        then
 
        return false
 
    end
 
    -- If there is no pageObject available, then that either means that we are over
 
    -- the expensive function limit or that the title specified was invalid. Invalid
 
    -- titles will probably only be a problem during testing, so we choose the best
 
    -- fallback for being over the expensive function limit. The fallback behaviour
 
    -- of the old template was to assume the page was not a subpage, so we will do
 
    -- the same here.
 
    if args[cfg.subpage] == cfg.subpageNo and pageObject and pageObject.isSubpage then
 
        return false
 
    end
 
    if args[cfg.subpage] == cfg.subpageOnly
 
        and (not pageObject or (pageObject and not pageObject.isSubpage) ) then
 
        return false
 
    end
 
    return true
 
 
end
 
end
  
-- Find whether we need to check the blacklist or not.
+
function CategoryHandler:getNamespaceParameters()
local function needsBlacklistCheck( args )
+
if self._usesCurrentTitle then
    if args[cfg.nocat] == cfg.nocatFalse
+
return self._data.currentTitleNamespaceParameters
        or args[cfg.categories] == cfg.categoriesYes
+
else
        or args[cfg.category2] == cfg.category2Yes then
+
if not mappings then
        return false
+
mShared = mShared or require('Module:Category handler/shared')
    else
+
mappings = mShared.getParamMappings(true) -- gets mappings with mw.loadData
        return true
+
end
    end
+
return mShared.getNamespaceParameters(
 +
self.title,
 +
mappings
 +
)
 +
end
 
end
 
end
  
-- Searches the blacklist to find a match with the page object. The
+
function CategoryHandler:namespaceParametersExist()
-- string searched is the namespace plus the title, including subpages.
+
-- Find whether any namespace parameters have been specified.
-- Returns true if there is a match, otherwise returns false.
+
-- We use the order "all" --> namespace params --> "other" as this is what
local function findBlacklistMatch( pageObject )
+
-- the old template did.
    if not pageObject then return end
+
if self:parameter('all') then
   
+
return true
    -- Get the title to check.
+
end
    local title = pageObject.nsText -- Get the namespace.
+
if not mappings then
    -- Append a colon if the namespace isn't the blank string.
+
mShared = mShared or require('Module:Category handler/shared')
    if #title > 0 then
+
mappings = mShared.getParamMappings(true) -- gets mappings with mw.loadData
        title = title .. ':' .. pageObject.text
+
end
    else
+
for ns, params in pairs(mappings) do
        title = pageObject.text
+
for i, param in ipairs(params) do
    end
+
if self._args[param] then
   
+
return true
    -- Check the blacklist.
+
end
    for i, pattern in ipairs( cfg.blacklist ) do
+
end
        if mw.ustring.match( title, pattern ) then
+
end
            return true
+
if self:parameter('other') then
        end
+
return true
    end
+
end
    return false
+
return false
 
end
 
end
  
-- Find whether any namespace parameters have been specified.
+
function CategoryHandler:getCategories()
-- Mappings is the table of parameter mappings taken from
+
local params = self:getNamespaceParameters()
-- [[Module:Namespace detect]].
+
local nsCategory
local function nsParamsExist( mappings, args )
+
for i, param in ipairs(params) do
    if args[cfg.all] or args[cfg.other] then
+
local value = self._args[param]
        return true
+
if value ~= nil then
    end
+
nsCategory = value
    for ns, params in pairs( mappings ) do
+
break
        for i, param in ipairs( params ) do
+
end
            if args[param] then
+
end
                return true
+
if nsCategory ~= nil or self:namespaceParametersExist() then
            end
+
-- Namespace parameters exist - advanced usage.
        end
+
if nsCategory == nil then
    end
+
nsCategory = self:parameter('other')
    return false
+
end
 +
local ret = {self:parameter('all')}
 +
local numParam = tonumber(nsCategory)
 +
if numParam and numParam >= 1 and math.floor(numParam) == numParam then
 +
-- nsCategory is an integer
 +
ret[#ret + 1] = self._args[numParam]
 +
else
 +
ret[#ret + 1] = nsCategory
 +
end
 +
if #ret < 1 then
 +
return nil
 +
else
 +
return table.concat(ret)
 +
end
 +
elseif self._data.defaultNamespaces[self.title.namespace] then
 +
-- Namespace parameters don't exist, simple usage.
 +
return self._args[1]
 +
end
 +
return nil
 
end
 
end
  
-- The main structure of the module. Checks whether we need to categorise,
+
--------------------------------------------------------------------------------
-- and then passes the relevant arguments to [[Module:Namespace detect]].
+
-- Exports
local function _main( args )
+
--------------------------------------------------------------------------------
    -- Get the page object and argument mappings from
+
 
    -- [[Module:Namespace detect]], to save us from having to rewrite the
+
local p = {}
    -- code.
+
 
    local pageObject = NamespaceDetect.getPageObject( args[cfg.page] )
+
function p._exportClasses()
    local mappings = NamespaceDetect.getParamMappings()
+
-- Used for testing purposes.
   
+
return {
    -- Check if we need a category or not, and return nothing if not.
+
CategoryHandler = CategoryHandler
    if not needsCategory( pageObject, args ) then return end
+
}
   
 
    local ret = '' -- The string to return.
 
    -- Check blacklist if necessary.
 
    if not needsBlacklistCheck( args )
 
        or not findBlacklistMatch( pageObject ) then
 
       
 
        if not nsParamsExist( mappings, args ) then
 
            -- No namespace parameters exist; basic usage. Pass args[1] to
 
            -- [[Module:Namespace detect]] using the default namespace
 
            -- parameters, and return the result.
 
            local ndargs = {}
 
            for _, ndarg in ipairs( cfg.defaultNamespaces ) do
 
                ndargs[ndarg] = args[1]
 
            end
 
            ndargs.page = args.page
 
            local ndresult = NamespaceDetect.main( ndargs )
 
            if ndresult then
 
                ret = ret .. ndresult
 
            end
 
        else
 
            -- Namespace parameters exist; advanced usage.
 
            -- If the all parameter is specified, return it.
 
            if args.all then
 
                ret = ret .. args.all
 
            end
 
           
 
            -- Get the arguments to pass to [[Module:Namespace detect]].
 
            local ndargs = {}
 
            for ns, params in pairs( mappings ) do
 
                for _, param in ipairs( params ) do
 
                    ndargs[param] = args[param] or args[cfg.other] or nil
 
                end
 
            end
 
            if args.other then
 
                ndargs.other = args.other
 
            end
 
            if args.page then
 
                ndargs.page = args.page
 
            end
 
           
 
            local data = NamespaceDetect.main( ndargs )
 
           
 
            -- Work out what to return based on the result of the namespace
 
            -- detect call.
 
            local datanum = tonumber( data )
 
            if type( datanum ) == 'number' then
 
                -- "data" is a number, so return that positional parameter.
 
                -- Remove non-positive integer values, as only positive integers
 
                -- from 1-10 were used with the old template.
 
                if datanum > 0
 
                    and math.floor( datanum ) == datanum
 
                    and args[datanum] then
 
                    ret = ret .. args[ datanum ]
 
                end
 
            else
 
                -- "data" is not a number, so return it as it is.
 
                if type(data) == 'string' then
 
                    ret = ret .. data
 
                end
 
            end
 
        end
 
    end
 
    return ret
 
 
end
 
end
  
----------------------------------------------------------------------
+
function p._main(args, data)
--                        Global functions                          --
+
data = data or mw.loadData('Module:Category handler/data')
--      The following functions are global, because we want them    --
+
local handler = CategoryHandler.new(data, args)
--      to be accessible from #invoke and from other Lua modules.  --
+
if handler:isSuppressed() then
--      At the moment only the main function is here. It processes  --
+
return nil
--      the arguments and passes them to the _main function.        --
+
end
----------------------------------------------------------------------
+
return handler:getCategories()
 
+
end
function p.main( frame )
 
    -- If called via #invoke, use the args passed into the invoking
 
    -- template, or the args passed to #invoke if any exist. Otherwise
 
    -- assume args are being passed directly in.
 
    local origArgs
 
    if frame == mw.getCurrentFrame() then
 
        origArgs = frame:getParent().args
 
        for k, v in pairs( frame.args ) do
 
            origArgs = frame.args
 
            break
 
        end
 
    else
 
        origArgs = frame
 
    end
 
  
    -- Trim whitespace and remove blank arguments for the following args:
+
function p.main(frame, data)
    -- 1, 2, 3 etc., "nocat", "categories", "subpage", and "page".
+
data = data or mw.loadData('Module:Category handler/data')
    local args = {}
+
local args = require('Module:Arguments').getArgs(frame, {
    for k, v in pairs( origArgs ) do
+
wrappers = data.wrappers,
        v = mw.text.trim(v) -- Trim whitespace.
+
valueFunc = function (k, v)
        if type(k) == 'number'
+
v = trimWhitespace(v)
            or k == cfg.nocat
+
if type(k) == 'number' then
            or k == cfg.categories
+
if v ~= '' then
            or k == cfg.subpage
+
return v
            or k == cfg.page then
+
else
            if v ~= '' then
+
return nil
                args[k] = v
+
end
            end
+
else
        else
+
return v
            args[k] = v
+
end
        end
+
end
    end
+
})
   
+
return p._main(args, data)
    -- Lower-case "nocat", "categories", "category2", and "subpage". These
 
    -- parameters are put in lower case whenever they appear in the old
 
    -- template, so we can just do it once here and save ourselves some work.
 
    local lowercase = { cfg.nocat, cfg.categories, cfg.category2, cfg.subpage }
 
    for _, v in ipairs( lowercase ) do
 
        if args[v] then
 
            args[v] = mw.ustring.lower( args[v] )
 
        end
 
    end
 
   
 
    return _main( args )
 
 
end
 
end
  
 
return p
 
return p

Latest revision as of 02:45, 18 May 2018

Documentation for this module may be created at Module:Category handler/doc

--------------------------------------------------------------------------------
--                                                                            --
--                              CATEGORY HANDLER                              --
--                                                                            --
--      This module implements the {{category handler}} template in Lua,      --
--      with a few improvements: all namespaces and all namespace aliases     --
--      are supported, and namespace names are detected automatically for     --
--      the local wiki. This module requires [[Module:Namespace detect]]      --
--      and [[Module:Yesno]] to be available on the local wiki. It can be     --
--      configured for different wikis by altering the values in              --
--      [[Module:Category handler/config]], and pages can be blacklisted      --
--      from categorisation by using [[Module:Category handler/blacklist]].   --
--                                                                            --
--------------------------------------------------------------------------------

-- Load required modules
local yesno = require('Module:Yesno')

-- Lazily load things we don't always need
local mShared, mappings

local p = {}

--------------------------------------------------------------------------------
-- Helper functions
--------------------------------------------------------------------------------

local function trimWhitespace(s, removeBlanks)
	if type(s) ~= 'string' then
		return s
	end
	s = s:match('^%s*(.-)%s*$')
	if removeBlanks then
		if s ~= '' then
			return s
		else
			return nil
		end
	else
		return s
	end
end

--------------------------------------------------------------------------------
-- CategoryHandler class
--------------------------------------------------------------------------------

local CategoryHandler = {}
CategoryHandler.__index = CategoryHandler

function CategoryHandler.new(data, args)
	local obj = setmetatable({ _data = data, _args = args }, CategoryHandler)
	
	-- Set the title object
	do
		local pagename = obj:parameter('demopage')
		local success, titleObj
		if pagename then
			success, titleObj = pcall(mw.title.new, pagename)
		end
		if success and titleObj then
			obj.title = titleObj
			if titleObj == mw.title.getCurrentTitle() then
				obj._usesCurrentTitle = true
			end
		else
			obj.title = mw.title.getCurrentTitle()
			obj._usesCurrentTitle = true
		end
	end

	-- Set suppression parameter values
	for _, key in ipairs{'nocat', 'categories'} do
		local value = obj:parameter(key)
		value = trimWhitespace(value, true)
		obj['_' .. key] = yesno(value)
	end
	do
		local subpage = obj:parameter('subpage')
		local category2 = obj:parameter('category2')
		if type(subpage) == 'string' then
			subpage = mw.ustring.lower(subpage)
		end
		if type(category2) == 'string' then
			subpage = mw.ustring.lower(category2)
		end
		obj._subpage = trimWhitespace(subpage, true)
		obj._category2 = trimWhitespace(category2) -- don't remove blank values
	end
	return obj
end

function CategoryHandler:parameter(key)
	local parameterNames = self._data.parameters[key]
	local pntype = type(parameterNames)
	if pntype == 'string' or pntype == 'number' then
		return self._args[parameterNames]
	elseif pntype == 'table' then
		for _, name in ipairs(parameterNames) do
			local value = self._args[name]
			if value ~= nil then
				return value
			end
		end
		return nil
	else
		error(string.format(
			'invalid config key "%s"',
			tostring(key)
		), 2)
	end
end

function CategoryHandler:isSuppressedByArguments()
	return
		-- See if a category suppression argument has been set.
		self._nocat == true
		or self._categories == false
		or (
			self._category2
			and self._category2 ~= self._data.category2Yes
			and self._category2 ~= self._data.category2Negative
		)

		-- Check whether we are on a subpage, and see if categories are
		-- suppressed based on our subpage status.
		or self._subpage == self._data.subpageNo and self.title.isSubpage
		or self._subpage == self._data.subpageOnly and not self.title.isSubpage
end

function CategoryHandler:shouldSkipBlacklistCheck()
	-- Check whether the category suppression arguments indicate we
	-- should skip the blacklist check.
	return self._nocat == false
		or self._categories == true
		or self._category2 == self._data.category2Yes
end

function CategoryHandler:matchesBlacklist()
	if self._usesCurrentTitle then
		return self._data.currentTitleMatchesBlacklist
	else
		mShared = mShared or require('Module:Category handler/shared')
		return mShared.matchesBlacklist(
			self.title.prefixedText,
			mw.loadData('Module:Category handler/blacklist')
		)
	end
end

function CategoryHandler:isSuppressed()
	-- Find if categories are suppressed by either the arguments or by
	-- matching the blacklist.
	return self:isSuppressedByArguments()
		or not self:shouldSkipBlacklistCheck() and self:matchesBlacklist()
end

function CategoryHandler:getNamespaceParameters()
	if self._usesCurrentTitle then
		return self._data.currentTitleNamespaceParameters
	else
		if not mappings then
			mShared = mShared or require('Module:Category handler/shared')
			mappings = mShared.getParamMappings(true) -- gets mappings with mw.loadData
		end
		return mShared.getNamespaceParameters(
			self.title,
			mappings
		)
	end
end

function CategoryHandler:namespaceParametersExist()
	-- Find whether any namespace parameters have been specified.
	-- We use the order "all" --> namespace params --> "other" as this is what
	-- the old template did.
	if self:parameter('all') then
		return true
	end
	if not mappings then
		mShared = mShared or require('Module:Category handler/shared')
		mappings = mShared.getParamMappings(true) -- gets mappings with mw.loadData
	end
	for ns, params in pairs(mappings) do
		for i, param in ipairs(params) do
			if self._args[param] then
				return true
			end
		end
	end
	if self:parameter('other') then
		return true
	end
	return false
end

function CategoryHandler:getCategories()
	local params = self:getNamespaceParameters()
	local nsCategory
	for i, param in ipairs(params) do
		local value = self._args[param]
		if value ~= nil then
			nsCategory = value
			break
		end
	end
	if nsCategory ~= nil or self:namespaceParametersExist() then
		-- Namespace parameters exist - advanced usage.
		if nsCategory == nil then
			nsCategory = self:parameter('other')
		end
		local ret = {self:parameter('all')}
		local numParam = tonumber(nsCategory)
		if numParam and numParam >= 1 and math.floor(numParam) == numParam then
			-- nsCategory is an integer
			ret[#ret + 1] = self._args[numParam]
		else
			ret[#ret + 1] = nsCategory
		end
		if #ret < 1 then
			return nil
		else
			return table.concat(ret)
		end
	elseif self._data.defaultNamespaces[self.title.namespace] then
		-- Namespace parameters don't exist, simple usage.
		return self._args[1]
	end
	return nil
end

--------------------------------------------------------------------------------
-- Exports
--------------------------------------------------------------------------------

local p = {}

function p._exportClasses()
	-- Used for testing purposes.
	return {
		CategoryHandler = CategoryHandler
	}
end

function p._main(args, data)
	data = data or mw.loadData('Module:Category handler/data')
	local handler = CategoryHandler.new(data, args)
	if handler:isSuppressed() then
		return nil
	end
	return handler:getCategories()
end

function p.main(frame, data)
	data = data or mw.loadData('Module:Category handler/data')
	local args = require('Module:Arguments').getArgs(frame, {
		wrappers = data.wrappers,
		valueFunc = function (k, v)
			v = trimWhitespace(v)
			if type(k) == 'number' then
				if v ~= '' then
					return v
				else
					return nil
				end
			else
				return v
			end
		end
	})
	return p._main(args, data)
end

return p