error_cats_t = {};															-- for categorizing citations that contain errors
	error_ids_t = {};															-- list of error identifiers; used to prevent duplication of certain errors; local to this module
	error_msgs_t = {};															-- sequence table of error messages
	maint_cats_t = {};															-- for categorizing citations that aren't erroneous per se, but could use a little work
	prop_cats_t = {};															-- for categorizing citations based on certain properties, language of source for instance
	prop_keys_t = {};															-- for adding classes to the citation's  tag

------------------------------------------------------------------

local cfg;																		-- table of tables imported from selected Module:Citation/CS1/Configuration

----------------------------------------------------------------------------------------------

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

------------------------------------------------------------------------------------------

Whether needle is in haystack


local function in_array 
	if needle == nil then
		return false;
	end
	for n, v in ipairs (haystack) do
		if v == needle then
			return n;
		end
	end
	return false;
end

----------------------------------------------------------------

When  and false else

with allow_empty = false,  must have at least one character inside the markup
with allow_empty = true,  the markup frame can be empty like () to distinguish an empty template parameter from the specific condition "has no applicable value" in citation-context.

After further evaluation the two cases might be merged at a later stage, but should be kept separated for now.


local function has_accept_as_written 
	if not is_set (str) then
		return str, false;
	end

	local count;

	if true == allow_empty then
		str, count = str:gsub ('^%(%((.*)%)%)$', '%1'); 						-- allows () to be an empty set
	else
		str, count = str:gsub ('^%(%((.+)%)%)$', '%1');
	end
	return str, 0 ~= count;
end

--------------------------------------------------------------------------------------

Populates numbered arguments in a message string using an argument table.  may be a single string or a
sequence table of multiple strings.


local function substitute 
	return args and mw.message.newRawMessage :plain or msg;
end

--------------------------------------------------------------------------------

Wraps error messages with CSS markup according to the state of hidden.  may be a single string or a
sequence table of multiple strings.


local function error_comment 
	return substitute ;
end

------------------------------------------------------------------------------

Converts a hyphen to a dash under certain conditions. The hyphen must separate
like items; unlike items are returned unmodified. These forms are modified:
	letter - letter (A - B)
	digit - digit (4-5)
	digit separator digit - digit separator digit (4.1-4.5 or 4-1-4-5)
	letterdigit - letterdigit (A1-A5) (an optional separator between letter and
		digit is supported – a.1-a.5 or a-1-a-5)
	digitletter - digitletter (5a - 5d) (an optional separator between letter and
		digit is supported – 5.a-5.d or 5-a-5-d)

any other forms are returned unmodified.

str may be a comma- or semicolon-separated list


local function hyphen_to_dash (str)
	if not is_set (str) then
		return str;
	end

	local accept;																-- boolean

	str = str:gsub ("(%(%(.-%)%))", function(m) return m:gsub:gsub end) -- replace commas and semicolons in accept-as-written markup with similar unicode characters so they'll be ignored during the split	
	str = str:gsub ;		-- replace &mdash; and &ndash; entities with their characters; semicolon mucks up the text.split
	str = str:gsub ; -- replace HTML numeric entity with hyphen character
	str = str:gsub ; -- replace &nbsp; entity with generic keyboard space character
	
	local out = {};
	local list = mw.text.split ;								-- split str at comma or semicolon separators if there are any

	for _, item in ipairs (list) do												-- for each item in the list
		item, accept = has_accept_as_written (item);							-- remove accept-this-as-written markup when it wraps all of item
		if not accept and mw.ustring.match  then	-- if a hyphenated range or has endash or emdash separators
			if item:match ('^%a+[%.%-]?%d+%s*%-%s*%a+[%.%-]?%d+$') or			-- letterdigit hyphen letterdigit (optional separator between letter and digit)
				item:match ('^%d+[%.%-]?%a+%s*%-%s*%d+[%.%-]?%a+$') or			-- digitletter hyphen digitletter (optional separator between digit and letter)
				item:match ('^%d+[%.%-]%d+%s*%-%s*%d+[%.%-]%d+$') or			-- digit separator digit hyphen digit separator digit
				item:match ('^%d+%s*%-%s*%d+$') or								-- digit hyphen digit
				item:match ('^%a+%s*%-%s*%a+$') then							-- letter hyphen letter
					item = item:gsub ('(%w*[%.%-]?%w+)%s*%-%s*(%w*[%.%-]?%w+)', '%1–%2');	-- replace hyphen, remove extraneous space characters
			else
				item = mw.ustring.gsub ;				-- for endash or emdash separated ranges, replace em with en, remove extraneous whitespace
			end
		end
		table.insert ;												-- add the (possibly modified) item to the output table
	end

	local temp_str = '';														-- concatenate the output table into a comma separated string
	temp_str, accept = has_accept_as_written (table.concat );		-- remove accept-this-as-written markup when it wraps all of concatenated out
	if accept then
		temp_str = has_accept_as_written (str);									-- when global markup removed, return original str; do it this way to suppress boolean second return value
		return temp_str:gsub:gsub;
	else
		return temp_str:gsub:gsub;						-- else, return assembled temp_str
	end
end

--[=[-----------------------------------------------------------------------------

Makes a wikilink; when both link and display text is provided, returns a wikilink in the form D; if only
link is provided (or link and display are the same), returns a wikilink in the form L; if neither are
provided or link is omitted, returns an empty string.

]=]

local function make_wikilink 
	if not is_set (link) then return '' end

	if is_set (display) and link ~= display then			
		return table.concat ;			
	else
		return table.concat ;
	end
end

--[[------------------------------------------------------------------------------------

Sets an error message using the ~/Configuration error_conditions{} table along with arguments supplied in the function
call, inserts the resulting message in z.error_msgs_t{} sequence table, and returns the error message.

 – key value for appropriate error handler in ~/Configuration error_conditions{} table 
 – may be a single string or a sequence table of multiple strings to be subsititued into error_conditions[error_id].message
 – boolean
	true –	causes this function to return the error message not wrapped in visible-error, hidden-error span tag;
			returns error_conditions[error_id].hidden as a second return value
			does not add message to z.error_msgs_t sequence table
	false, nil – adds message wrapped in visible-error, hidden-error span tag to z.error_msgs_t
			returns the error message wrapped in visible-error, hidden-error span tag; there is no second return value
									-- TODO: remove support for these unused(?) arguments?

TODO: change z.error_cats_t and z.maint_cats_t to have the form cat_name = true? this to avoid dups without having to have an extra table

]]

local added_maint_cats = {}														-- list of maintenance categories that have been added to z.maint_cats_t; TODO: figure out how to delete this table

local function set_message 
	local error_state = cfg.error_conditions[error_id];
	
	prefix = prefix or '';
	suffix = suffix or '';
	
	if error_state == nil then
		error (cfg.messages['undefined_error'] .. ': ' .. error_id);			-- because missing error handler in Module:Citation/CS1/Configuration

	elseif is_set (error_state.category) then
		if error_state.message then												-- when error_state.message defined, this is an error message
			table.insert ;
		else
			if not added_maint_cats[error_id] then
				added_maint_cats[error_id] = true;								-- note that we've added this category
				table.insert (z.maint_cats_t, substitute );	-- make cat name then add to table
			end
			return;																-- because no message, nothing more to do
		end
	end

	local message = substitute ;

	message = table.concat (
		message,
		' (',
		make_wikilink (
			table.concat ,
		')'

	z.error_ids_t[error_id] = true;
	if z.error_ids_t['err_citation_missing_title'] and							-- if missing-title error already noted
		in_array  then		-- and this error is one of these
			return '', false;													-- don't bother because one flavor of missing title is sufficient
	end
	
	message = table.concat ;

	if true == raw then
		return message, error_state.hidden;										-- return message not wrapped in visible-error, hidden-error span tag
	end		

	message = error_comment ;						-- wrap message in visible-error, hidden-error span tag
	table.insert ;										-- add it to the messages sequence table
	return message;																-- and done; return value generally not used but is used as a flag in various functions of ~/Identifiers
end

--------------------------------------------------------------------------------

This function is used by select_one to determine if one of a list of alias parameters is in the argument list
provided by the template.

Input:
	args – pointer to the arguments table from calling template
	alias – one of the list of possible aliases in the aliases lists from Module:Citation/CS1/Configuration
	index – for enumerated parameters, identifies which one
	enumerated – true/false flag used to choose how enumerated aliases are examined
	value – value associated with an alias that has previously been selected; nil if not yet selected
	selected – the alias that has previously been selected; nil if not yet selected
	error_list – list of aliases that are duplicates of the alias already selected

Returns:
	value – value associated with alias we selected or that was previously selected or nil if an alias not yet selected
	selected – the alias we selected or the alias that was previously selected or nil if an alias not yet selected


local function is_alias_used 
	if enumerated then															-- is this a test for an enumerated parameters?
		alias = alias:gsub ;										-- replace '#' with the value in index
	else
		alias = alias:gsub ;											-- remove '#' if it exists
	end

	if is_set (args[alias]) then												-- alias is in the template's argument list
		if value ~= nil and selected ~= alias then								-- if we have already selected one of the aliases
			local skip;
			for _, v in ipairs (error_list) do									-- spin through the error list to see if we've added this alias
				if v == alias then
					skip = true;
					break;														-- has been added so stop looking 
				end
			end
			if not skip then													-- has not been added so
				table.insert ;								-- add error alias to the error list
			end
		else
			value = args[alias];												-- not yet selected an alias, so select this one
			selected = alias;
		end
	end
	return value, selected;														-- return newly selected alias, or previously selected alias
end

----------------------------------------------------------------------------------

Adds a category to z.maint_cats_t using names from the configuration file with additional text if any.
To prevent duplication, the added_maint_cats table lists the categories by key that have been added to z.maint_cats_t.


local function add_maint_cat 
	if not added_maint_cats [key] then
		added_maint_cats [key] = true;											-- note that we've added this category
		table.insert (z.maint_cats_t, substitute );	-- make name then add to table
	end
end

------------------------------------------------------------------------------------

Adds a category to z.prop_cats_t using names from the configuration file with additional text if any.

foreign_lang_source and foreign_lang_source_2 keys have a language code appended to them so that multiple languages
may be categorized but multiples of the same language are not categorized.

added_prop_cats is a table declared in page scope variables above


local added_prop_cats = {};														-- list of property categories that have been added to z.prop_cats_t

local function add_prop_cat 
	local key_modified = key .. ((key_modifier and key_modifier) or '');		-- modify  if present and not nil
	
	if not added_prop_cats [key_modified] then
		added_prop_cats [key_modified] = true;									-- note that we've added this category
		table.insert (z.prop_cats_t, substitute );	-- make name then add to table
		table.insert ;						-- convert key to class for use in the citation's  tag
	end
end

--------------------------------------------------------------------------

Protects a string that will be wrapped in wiki italic markup '' ... ''

Note: We cannot use  for italics, as the expected behavior for italics specified by ''...'' in the title is that
they will be inverted (i.e. unitalicized) in the resulting references. In addition,  and '' tend to interact
poorly under Mediawiki's HTML tidy.


local function safe_for_italics (str)
	if not is_set (str) then return str end

	if str:sub  == "'" then str = "" .. str; end
	if str:sub  == "'" then str = str .. ""; end
	
	return str:gsub ;												-- Remove newlines as they break italics.
end

--------------------------------------------------------------------------------------

Applies styling to various parameters. Supplied string is wrapped using a message_list configuration taking one
argument; protects italic styled parameters. Additional text taken from citation_config.presentation - the reason
this function is similar to but separate from wrap_msg.


local function wrap_style 
	if not is_set (str) then
		return "";
	elseif in_array  then
		str = safe_for_italics (str);
	end

	return substitute ;
end

--[[--------------------------------------------------------------------------------------

make a separated list of items using provided separators.
	'
	'
	'

defaults to cfg.presentation['sep_list'], cfg.presentation['sep_list_pair'], and cfg.presentation['sep_list_end']
if  must also be supplied

]]

local function make_sep_list 
	local list = '';

	if not sep_list then														-- set the defaults
		sep_list = cfg.presentation['sep_list'];
		sep_list_pair = cfg.presentation['sep_list_pair'];
		sep_list_end = cfg.presentation['sep_list_end'];
	end
	
	if 2 >= count then
		list = table.concat ;							-- insert separator between two items; returns list_seq[1] then only one item
	elseif 2 < count then
		list = table.concat ;					-- concatenate all but last item with plain list separator
		list = table.concat ;			-- concatenate last item onto end of  with final separator
	end
	
	return list;
end

--author-last1= and |author1-last= are represented as 'author-last#' and 'author#-last'.

Because enumerated parameter |= we must test for both possibilities.

Generates an error if more than one match is present.


local function select_one 
	local value = nil;															-- the value assigned to the selected parameter
	local selected = '';														-- the name of the parameter we have chosen
	local error_list = {};

	if index ~= nil then index = tostring(index); end

	for _, alias in ipairs (aliases_list) do									-- for each alias in the aliases list
		if alias:match ('#') then												-- if this alias can be enumerated
			if '1' == index then												-- when index is 1 test for enumerated and non-enumerated aliases
				value, selected = is_alias_used ;	-- first test for non-enumerated alias
			end
			value, selected = is_alias_used ;	-- test for enumerated alias
		else
			value, selected = is_alias_used ;	-- test for non-enumerated alias
		end
	end

	if #error_list > 0 and 'none' ~= error_condition then						-- for cases where this code is used outside of extract_names
		for i, v in ipairs (error_list) do
			error_list[i] = wrap_style ;
		end
		table.insert (error_list, wrap_style );
		set_message (error_condition, {make_sep_list });
	end
	
	return value, selected;
end

--[=[-----------------------------------------------------------------------

Gets the display text from a wikilink like B or B gives B

The str:gsub returns either A|B froma B or B from B or B from B (no wikilink markup).

In l, l:gsub removes the link and pipe (if they exist); the second :gsub trims whitespace from the label
if str was wrapped in wikilink markup. Presumably, this is because without wikimarkup in str, there is no match
in the initial gsub, the replacement function l doesn't get called.

]=]

local function remove_wiki_link (str)
	return (str:gsub ("%[%[([^%[%]]*)%]%]", function(l)
		return l:gsub ("^[^|]*|(.*)$", "%1" ):gsub ("^%s*(.-)%s*$", "%1");
	end));
end

--[=[---------------------------------------------------------------------------------

Determines if str is a wikilink, extracts, and returns the wikilink type, link text, and display text parts.
If str is a complex wikilink (D):
	returns wl_type 2 and D and L from D;
if str is a simple wikilink (D)
	returns wl_type 1 and D from D and L as empty string;
if not a wikilink:
	returns wl_type 0, str as D, and L as empty string.

trims leading and trailing whitespace and pipes from L and D .

]=]

local function is_wikilink (str)
	local D, L
	local wl_type = 2;															-- assume that str is a complex wikilink D

	if not str:match ('^%[%^%+%]%]$') then									-- is str some sort of a wikilink (must have some sort of content)
		return 0, str, '';														-- not a wikilink; return wl_type as 0, str as D, and empty string as L
	end
	
	L, D = str:match ('^%[%[([^|]+)|([^%]]+)%]%]$');							-- get L and D from D 

	if not is_set (D) then														-- if no separate display
		D = str:match ('^%[%[([^%]]*)|*%]%]$');									-- get D from D or D|
		wl_type = 1; 
	end
	
	D = mw.text.trim ;												-- trim white space and pipe characters 
	return wl_type, D, L or '';
end

------------------------------------------------------------

Strip wiki italic and bold markup from argument so that it doesn't contaminate COinS metadata.
This function strips common patterns of apostrophe markup. We presume that editors who have taken the time to
markup a title have, as a result, provided valid markup. When they don't, some single apostrophes are left behind.

Returns the argument without wiki markup and a number; the number is more-or-less meaningless except as a flag
to indicate that markup was replaced; do not rely on it as an indicator of how many of any kind of markup was
removed; returns the argument and nil when no markup removed


local function strip_apostrophe_markup (argument)
	if not is_set (argument) then
		return argument, nil;													-- no argument, nothing to do
	end

	if nil == argument:find  then								-- Is there at least one double apostrophe? If not, exit.
		return argument, nil;
	end

	local flag;
	while true do
		if argument:find  then								-- bold italic (5)
			argument, flag = argument:gsub ;					-- remove all instances of it
		elseif argument:find  then								-- italic start and end without content (4)
			argument, flag=argument:gsub ;
		elseif argument:find  then								-- bold (3)
			argument, flag=argument:gsub ;
		elseif argument:find  then								-- italic (2)
			argument, flag = argument:gsub ;
		else
			break;
		end
	end

	return argument, flag;														-- done
end

------------------------------------------------------------------

Sets local cfg table to same (live or sandbox) as that used by the other modules.


local function set_selected_modules (cfg_table_ptr)
	cfg = cfg_table_ptr;
	
end

--------------------------------------------------------------------------------------------

return {
	add_maint_cat = add_maint_cat,												-- exported functions
	add_prop_cat = add_prop_cat,
	error_comment = error_comment,
	has_accept_as_written = has_accept_as_written,
	hyphen_to_dash = hyphen_to_dash,
	in_array = in_array,
	is_set = is_set,
	is_wikilink = is_wikilink,
	make_sep_list = make_sep_list,
	make_wikilink = make_wikilink,
	remove_wiki_link = remove_wiki_link,
	safe_for_italics = safe_for_italics,
	select_one = select_one,
	set_message = set_message,
	set_selected_modules = set_selected_modules,
	strip_apostrophe_markup = strip_apostrophe_markup,
	substitute = substitute,
	wrap_style = wrap_style,

	z = z,																		-- exported table