Module:Catalog lookup link
--[[
 |1=, |2=, |3=, |4=, |5=, |6=, |7=, |8=, |9=: Optional unnamed parameters for 0 to 9 items to be listed.
 	Whitespace is trimmed off both ends and the strings are urlencoded as if they were query strings.
 |article-link=: Optional Wikipedia article name to link to.
 |article-name=: Optional alternative text to be displayed for |article-link= link in front of catalog link.
 	If not specified, |article-link= is used for display as well. If both parameters are not specified, the prefix is omitted completely.
 |article-suffix=: Optional symbol to be displayed after article name or link (f.e. &quot;:&quot;; omitted, if not defined).
 |link-prefix=: Optional prefix portion of url to external catalog item(s).
 |link-suffix=: Optional suffix portion of url to external catalog item(s).
 |item-prefix=: Optional text displayed in front of each external link (omitted, if not defined)
 |item-suffix=: Optional text displayed immediately after each external link (omitted, if not defined)
 |list-separator=: Optional alternative separator displayed between list items (default: &quot;, &quot;, if not specified). Whitespace must be encoded.
 |list-leadout=: Optional alternative leadout text displayed between the last two list items (f.e. &quot;and&quot;, &quot;or&quot;, &quot;as well as&quot;, etc., default is the |list-separator= or &quot;, &quot;.)
 |leadout-suffix=: Optional alternative suffix text of the leadout (see |list-leadout=) displayed between the last two list items.
 	This gets added in front of the last list item instead of the default whitespace which is added without this parameter.
 	This may be necessary if |list-separator= is used not only to define the list separator but also parts of the item prefix
 	(except for the first one). (At present, this is used only to cope with format oddities of the {{MR}} template.)
 
 
 new parameters that support access icons:
 |allowed_icons= – comma-separated list of keywords: free, limited, registration, subscription, none, all (default; 'all' implied when this parameter empty or omitted)
 	the icons specified in the following parameters are checked agains the list in |allowed-icons=; not in the list? not displayed
 |url-access-all= – applies specified icon to all items in the list; accepted keywords: free, limited, registration, subscription;
 |url-accessn= – applies specified icon to item n of the list (the nth positional parameter); accepted keywords: free, limited, registration, subscription;
 
 ]]
 
 require('Module:No globals');
 local getArgs = require ('Module:Arguments').getArgs;
 local lock_icons = {															--icon classes are defined in Module:Citation/CS1/styles.css
 	['free'] = {'cs1-lock-free', 'Freely accessible'},
 	['registration'] = {'cs1-lock-registration', 'Free registration required'},
 	['limited'] = {'cs1-lock-limited', 'Free access subject to limited trial, subscription normally required'},
 	['subscription'] = {'cs1-lock-subscription', 'Paid subscription required'},
 	}
 
 
 --[[--------------------------&lt; I S _ S E T &gt;------------------------------------------------------------------
 
 Returns true if argument is set; false otherwise. Argument is 'set' when it exists (not nil) or when it is not an empty string.
 
 ]]
 
 local function is_set( var )
 	return not (var == nil or var == '');
 end
 
 
 --[=[-------------------------&lt; M A K E _ L A B E L &gt;----------------------------------------------------------
 
 Makes a wikilinked or plain text label from arguments; when both link and display text is provided, makes a
 wikilink in the form [[L|D]]; if only link is provided, makes a wikilinked label in the form [[L]]; if only display
 is provided, makes a plain-text label; if neither are provided makes a label from suffix, returns an empty string else.
 
 ]=]
 
 local function make_label (link, display, suffix)
 local label = '';
 	if is_set (link) then
 		if is_set (display) then
 			label = table.concat ({'[[', link, '|', display, ']]'});			-- make [[L|D]] wikilinked label
 		else
 			label = table.concat ({'[[', link, ']]'});							-- make [[L]] wikilinked label
 		end
 	elseif is_set (display) then
 		label = display;														-- plain-text label
 	end
 
 	if is_set (label) then														
 		return table.concat ({label, suffix, '&amp;nbsp;'});						-- assemble the complete label
 	else
 		return suffix;															-- no space after suffix if no label
 	end
 end
 
 
 --[[--------------------------&lt; I C O N _ I N D E X _ G E T &gt;--------------------------------------------------
 
 returns index into lock_icons[] if value assigned to |url-access= or |url-access-all= is a valid icon selector
 (free, limited, registration, subscription)
 
 icon selection may be limited to a subset of the icons with:
 	|allow_icons=&lt;comma-separated list of allowed icons&gt;
 &lt;comma-separated list of allowed icons&gt; may be any of the keywords: free, limited, registration, subscription, none, all
 
 keyword 'all' is default condition; 'all' is implied when |allowed=icons= is empty or omitted
 
 keyword 'none' for use with identifiers where icons are inappropriate (isbn, issn, oclc)
 
 Templates using this module should set:
 	|allow_icons=free for most identifiers;
 	|allow_icons=none for isbn, issn, oclc, etc
 
 |url-access= is alias of |url-access1=
 
 ]]
 
 local function icon_index_get (args, k)
 	local icon;
 	local param_name = (1 == k and is_set (args['url-access']) and 'url-access') or table.concat ({'url-access', k});	-- make an enumerated parameter name
 
 	if is_set (args['url-access-all']) and lock_icons[args['url-access-all']] then	-- if set and valid
 		icon = args['url-access-all'];											-- tentatively 
 
 	elseif is_set (args[param_name]) and lock_icons[args[param_name]] then		-- if set and valid
 		icon = args[param_name];												-- tentatively
 
 	else
 		return nil;																-- neither |url-access-all= nor |url-accessn= set so return nil
 	end
 
 	if args['allow_icons'] and args['allow_icons']:find ('none') then			-- if 'none' keyword is present
 		return nil;																-- icons display not allowed
 	end
 
 	if not is_set (args['allow_icons']) or args['allow_icons']:find ('all') or args['allow_icons']:find (icon) then	--if all allowed or specified icon is allowed
 		return icon;															-- return selected icon as index into icon table
 	end
 end
 
 
 --[[--------------------------&lt; M A I N &gt;----------------------------------------------------------------------
 
 Template entrypoint to this module; arguments come primarily from the parent frame though in templates that use
 this module, |allowed-icons= is typically set, if needed, in the {{#invoke:}}.
 
 ]]
 
 local function main (frame)
 	local args = getArgs (frame);
 	local out_text = '';
 
 	if is_set(args[1]) then
 		local result = {};
 		local label;
 		
 		local article_suffix = args['article-suffix'] or args['article-postfix'] or '';
 		local link_prefix = args['link-prefix'] or '';
 		local link_suffix = args['link-suffix'] or args['link-postfix'] or '';
 		local item_prefix = args['item-prefix'] or '';
 		local item_suffix = args['item-suffix'] or args['item-postfix'] or '';
 		local list_separator = args['list-separator'] or ', ';
 		local leadout_suffix = args['leadout-suffix'] or args['leadout-postfix'] or ' ';
 		local list_leadout;
 
 		local icon_index;
 		
 		if is_set (args['list-leadout']) then
 			list_leadout = table.concat ({
 				mw.ustring.gsub (args['list-leadout'], '^(%a)', ' %1'),			-- insert leading space if first character is a letter
 				leadout_suffix,
 			});
 		else
 			list_leadout = '';
 		end
 		
 		label = make_label (args['article-link'], args['article-name'], article_suffix);
 
 		for k, item in ipairs (args) do											-- for each of the positional parameters
 			item = mw.text.trim (item);											-- remove extraneous whitespace
 			if is_set (link_prefix) then										-- if there is link prefix...
 				item = table.concat ({											-- create an external link item
 					'[',														-- open ext link markup
 					link_prefix,												-- url prefix
 					mw.uri.encode (item),										-- item is part of url
 					link_suffix,												-- url suffix
 					' ',														-- required space between url and label
 					item_prefix,												-- label prefix
 					item,														-- item as label
 					item_suffix,												-- item suffix
 					']'															-- close ext link markup
 				});
 
 				icon_index = icon_index_get (args, k);							-- set if icon specified and allowed for this item; nil else
 				if icon_index then
 					item = table.concat ({										-- add access icon markup to this item
 						'&lt;span class=&quot;',										-- open the opening span tag; icon classes are defined in Module:Citation/CS1/styles.css
 						lock_icons[icon_index][1],								-- add the appropriate lock icon class
 						'&quot; title=&quot;',											-- and the title attribute
 						lock_icons[icon_index][2],								-- for an appropriate tool tip
 						'&quot;&gt;',													-- close the opening span tag
 						item,
 						'&lt;/span&gt;',												-- and close the span
 					});
 				end	
 			else
 				item = table.concat ({											-- create an unlinked item
 					item_prefix,												-- label prefix
 					item,														-- item as label
 					item_suffix,												-- item suffix
 				});
 			end
 	
 			table.insert (result, item);										-- add the item to the result list
 		end
 	
 		if is_set (args['list-leadout']) then
 			out_text = table.concat ({label, mw.text.listToText (result, list_separator, list_leadout)});
 		else
 			out_text = table.concat ({label, table.concat (result, list_separator)});
 		end
 
 	end	--is_set (args[1])
 	
 	return out_text
 end