વિભાગ:Citation/CS1/Identifiers

local identifiers = {};

--[[--------------------------< F O R W A R D D E C L A R A T I O N S >--------------------------------------
]]

local is\_set, in\_array, set\_error, select\_one, add\_maint\_cat, substitute, make\_wikilink; -- functions in Module:Citation/CS1/Utilities

local z; -- table of tables defined in Module:Citation/CS1/Utilities

local cfg; -- table of configuration tables that are defined in Module:Citation/CS1/Configuration

--============================<< H E L P E R F U N C T I O N S >>============================================

--[[--------------------------< E X T E R N A L \_ L I N K \_ I D >----------------------------------------------

Formats a wiki style external link

]]

local function external\_link\_id(options)
 local url\_string = options.id;
 local ext\_link;

 if options.encode == true or options.encode == nil then
 url\_string = mw.uri.encode( url\_string );
 if 'doi' == options.label then -- 2018-07-02 doi.org stopped accepting urls with url encoded '/' (%2F)
 url\_string = url\_string:gsub ('%%2F', '/'); -- special case for doi; undo url-encoded slashes
 end
 end

 ext\_link = mw.ustring.format ('[%s%s%s %s]', options.prefix, url\_string, options.suffix or "", mw.text.nowiki(options.id));
 if is\_set(options.access) then
 ext\_link = substitute (cfg.presentation['access-signal'], {ext\_link, cfg.presentation[options.access]}); -- add the free-to-read / paywall lock
 end

 return table.concat ({
 make\_wikilink (options.link, options.label),
 options.separator or ' ',
 ext\_link
 });
end

--[[--------------------------< I N T E R N A L \_ L I N K \_ I D >----------------------------------------------

Formats a wiki style internal link

]]

local function internal\_link\_id(options)

 return table.concat (
 {
 make\_wikilink (options.link, options.label),
 options.separator or ' ',
 make\_wikilink (
 table.concat (
 {
 options.prefix,
 options.id,
 options.suffix or
 }),
 mw.text.nowiki (options.id)
 );
 });
end

--[[--------------------------< I S \_ E M B A R G O E D >------------------------------------------------------

Determines if a PMC identifier's online version is embargoed. Compares the date in |embargo= against today's date. If embargo date is
in the future, returns the content of |embargo=; otherwise, returns and empty string because the embargo has expired or because

]]

local function is\_embargoed (embargo)
 if is\_set (embargo) then
 local lang = mw.getContentLanguage();
 local good1, embargo\_date, good2, todays\_date;
 good1, embargo\_date = pcall( lang.formatDate, lang, 'U', embargo );
 good2, todays\_date = pcall( lang.formatDate, lang, 'U' );

 if good1 and good2 then -- if embargo date and today's date are good dates
 if tonumber( embargo\_date ) >= tonumber( todays\_date ) then -- is embargo date is in the future?
 return embargo; -- still embargoed
 else
 add\_maint\_cat ('embargo')
 return *; -- unset because embargo has expired*
 end
 end
 end
 return *; -- |embargo= not set return empty string*
end

--[[--------------------------< IS \_ V A L I D \_ I S X N >-----------------------------------------------------

ISBN-10 and ISSN validator code calculates checksum across all isbn/issn digits including the check digit.
ISBN-13 is checked in isbn().

If the number is valid the result will be 0. Before calling this function, issbn/issn must be checked for length
and stripped of dashes, spaces and other non-isxn characters.

]]

local function is\_valid\_isxn (isxn\_str, len)
 local temp = 0;
 isxn\_str = { isxn\_str:byte(1, len) }; -- make a table of byte values '0' → 0x30 .. '9' → 0x39, 'X' → 0x58
 len = len+1; -- adjust to be a loop counter
 for i, v in ipairs( isxn\_str ) do -- loop through all of the bytes and calculate the checksum
 if v == string.byte( "X" ) then -- if checkdigit is X (compares the byte value of 'X' which is 0x58)
 temp = temp + 10\*( len - i ); -- it represents 10 decimal
 else
 temp = temp + tonumber( string.char(v) )\*(len-i);
 end
 end
 return temp % 11 == 0; -- returns true if calculation result is zero
end

--[[--------------------------< IS \_ V A L I D \_ I S X N \_ 1 3 >-----------------------------------------------

ISBN-13 and ISMN validator code calculates checksum across all 13 isbn/ismn digits including the check digit.
If the number is valid, the result will be 0. Before calling this function, isbn-13/ismn must be checked for length
and stripped of dashes, spaces and other non-isxn-13 characters.

]]

local function is\_valid\_isxn\_13 (isxn\_str)
 local temp=0;

 isxn\_str = { isxn\_str:byte(1, 13) }; -- make a table of byte values '0' → 0x30 .. '9' → 0x39
 for i, v in ipairs( isxn\_str ) do
 temp = temp + (3 - 2\*(i % 2)) \* tonumber( string.char(v) ); -- multiply odd index digits by 1, even index digits by 3 and sum; includes check digit
 end
 return temp % 10 == 0; -- sum modulo 10 is zero when isbn-13/ismn is correct
end

--[[--------------------------< N O R M A L I Z E \_ L C C N >--------------------------------------------------

lccn normalization (http://www.loc.gov/marc/lccn-namespace.html#normalization)
1. Remove all blanks.
2. If there is a forward slash (/) in the string, remove it, and remove all characters to the right of the forward slash.
3. If there is a hyphen in the string:
 a. Remove it.
 b. Inspect the substring following (to the right of) the (removed) hyphen. Then (and assuming that steps 1 and 2 have been carried out):
 1. All these characters should be digits, and there should be six or less. (not done in this function)
 2. If the length of the substring is less than 6, left-fill the substring with zeroes until the length is six.

Returns a normalized lccn for lccn() to validate. There is no error checking (step 3.b.1) performed in this function.
]]

local function normalize\_lccn (lccn)
 lccn = lccn:gsub ("%s", ""); -- 1. strip whitespace

 if nil ~= string.find (lccn,'/') then
 lccn = lccn:match ("(.-)/"); -- 2. remove forward slash and all character to the right of it
 end

 local prefix
 local suffix
 prefix, suffix = lccn:match ("(.+)%-(.+)"); -- 3.a remove hyphen by splitting the string into prefix and suffix

 if nil ~= suffix then -- if there was a hyphen
 suffix=string.rep("0", 6-string.len (suffix)) .. suffix; -- 3.b.2 left fill the suffix with 0s if suffix length less than 6
 lccn=prefix..suffix; -- reassemble the lccn
 end

 return lccn;
 end

--============================<< I D E N T I F I E R F U N C T I O N S >>====================================

--[[--------------------------< A R X I V >--------------------------------------------------------------------

See: http://arxiv.org/help/arxiv\_identifier

format and error check arXiv identifier. There are three valid forms of the identifier:
the first form, valid only between date codes 9108 and 0703 is:
 arXiv:<archive>.<class>/<date code><number><version>
where:
 <archive> is a string of alpha characters - may be hyphenated; no other punctuation
 <class> is a string of alpha characters - may be hyphenated; no other punctuation
 <date code> is four digits in the form YYMM where YY is the last two digits of the four-digit year and MM is the month number January = 01
 first digit of YY for this form can only 9 and 0
 <number> is a three-digit number
 <version> is a 1 or more digit number preceded with a lowercase v; no spaces (undocumented)

the second form, valid from April 2007 through December 2014 is:
 arXiv:<date code>.<number><version>
where:
 <date code> is four digits in the form YYMM where YY is the last two digits of the four-digit year and MM is the month number January = 01
 <number> is a four-digit number
 <version> is a 1 or more digit number preceded with a lowercase v; no spaces

the third form, valid from January 2015 is:
 arXiv:<date code>.<number><version>
where:
 <date code> and <version> are as defined for 0704-1412
 <number> is a five-digit number
]]

local function arxiv (id, class)
 local handler = cfg.id\_handlers['ARXIV'];
 local year, month, version;
 local err\_cat = *;*
 local text;

 if id:match("^%a[%a%.%-]+/[90]%d[01]%d%d%d%d$") or id:match("^%a[%a%.%-]+/[90]%d[01]%d%d%d%dv%d+$") then -- test for the 9108-0703 format w/ & w/o version
 year, month = id:match("^%a[%a%.%-]+/([90]%d)([01]%d)%d%d%d[v%d]\*$");
 year = tonumber(year);
 month = tonumber(month);
 if ((not (90 < year or 8 > year)) or (1 > month or 12 < month)) or -- if invalid year or invalid month
 ((91 == year and 7 > month) or (7 == year and 3 < month)) then -- if years ok, are starting and ending months ok?
 err\_cat = ' ' .. set\_error( 'bad\_arxiv' ); -- set error message
 end
 elseif id:match("^%d%d[01]%d%.%d%d%d%d$") or id:match("^%d%d[01]%d%.%d%d%d%dv%d+$") then -- test for the 0704-1412 w/ & w/o version
 year, month = id:match("^(%d%d)([01]%d)%.%d%d%d%d[v%d]\*$");
 year = tonumber(year);
 month = tonumber(month);
 if ((7 > year) or (14 < year) or (1 > month or 12 < month)) or -- is year invalid or is month invalid? (doesn't test for future years)
 ((7 == year) and (4 > month)) then --or -- when year is 07, is month invalid (before April)?
 err\_cat = ' ' .. set\_error( 'bad\_arxiv' ); -- set error message
 end
 elseif id:match("^%d%d[01]%d%.%d%d%d%d%d$") or id:match("^%d%d[01]%d%.%d%d%d%d%dv%d+$") then -- test for the 1501- format w/ & w/o version
 year, month = id:match("^(%d%d)([01]%d)%.%d%d%d%d%d[v%d]\*$");
 year = tonumber(year);
 month = tonumber(month);
 if ((15 > year) or (1 > month or 12 < month)) then -- is year invalid or is month invalid? (doesn't test for future years)
 err\_cat = ' ' .. set\_error( 'bad\_arxiv' ); -- set error message
 end
 else
 err\_cat = ' ' .. set\_error( 'bad\_arxiv' ); -- arXiv id doesn't match any format
 end

 text = external\_link\_id({link = handler.link, label = handler.label,
 prefix=handler.prefix,id=id,separator=handler.separator, encode=handler.encode, access=handler.access}) .. err\_cat;

 if is\_set (class) then
 class = ' ' .. '//arxiv.org/archive/' .. class .. ' ' .. class .. ''; -- external link within square brackets, not wikilink
 else
 class = *; -- empty string for concatenation*
 end

 return text .. class;
end

--[[--------------------------< B I B C O D E >--------------------------------------------------------------------

Validates (sort of) and formats a bibcode id.

Format for bibcodes is specified here: http://adsabs.harvard.edu/abs\_doc/help\_pages/data.html#bibcodes

But, this: 2015arXiv151206696F is apparently valid so apparently, the only things that really matter are length, 19 characters
and first four digits must be a year. This function makes these tests:
 length must be 19 characters
 characters in position
 1–4 must be digits and must represent a year in the range of 1000 – next year
 5 must be a letter
 6 must be letter, ampersand, or dot (ampersand cannot directly precede a dot; &. )
 7–8 must be letter, digit, ampersand, or dot (ampersand cannot directly precede a dot; &. )
 9–18 must be letter, digit, or dot
 19 must be a letter or dot

]]

local function bibcode (id, access)
 local handler = cfg.id\_handlers['BIBCODE'];
 local err\_type;
 local year;

 local text = external\_link\_id({link=handler.link, label=handler.label,
 prefix=handler.prefix, id=id, separator=handler.separator, encode=handler.encode,
 access=access});

 if 19 ~= id:len() then
 err\_type = 'length';
 else
 year = id:match ("^(%d%d%d%d)[%a][%a&%.][%a&%.%d][%a&%.%d][%a%d%.]+[%a%.]$") --
 if not year then -- if nil then no pattern match
 err\_type = 'value'; -- so value error
 else
 local next\_year = tonumber(os.date ('%Y'))+1; -- get the current year as a number and add one for next year
 year = tonumber (year); -- convert year portion of bibcode to a number
 if (1000 > year) or (year > next\_year) then
 err\_type = 'year'; -- year out of bounds
 end
 if id:find('&%.') then
 err\_type = 'journal'; -- journal abbreviation must not have '&.' (if it does its missing a letter)
 end
 end
 end

 if is\_set (err\_type) then -- if there was an error detected
 text = text .. ' ' .. set\_error( 'bad\_bibcode', {err\_type});
 end
 return text;
end

--[[--------------------------< B I O R X I V >-----------------------------------------------------------------

Format bioRxiv id and do simple error checking. BiorXiv ids are exactly 6 digits.
The bioRxiv id is the number following the last slash in the bioRxiv-issued DOI:
https://doi.org/10.1101/078733 -> 078733

]]

local function biorxiv(id)
 local handler = cfg.id\_handlers['BIORXIV'];
 local err\_cat = *; -- presume that bioRxiv id is valid*

 if nil == id:match("^%d%d%d%d%d%d$") then -- if bioRxiv id has anything but six digits
 err\_cat = ' ' .. set\_error( 'bad\_biorxiv'); -- set an error message
 end

 return external\_link\_id({link = handler.link, label = handler.label,
 prefix=handler.prefix,id=id,separator=handler.separator,
 encode=handler.encode, access=handler.access}) .. err\_cat;
end

--[[--------------------------< C I T E S E E R X >------------------------------------------------------------

CiteSeerX use their own notion of "doi" (not to be confused with the identifiers resolved via doi.org).

The description of the structure of this identifier can be found at Help\_talk:Citation\_Style\_1/Archive\_26#CiteSeerX\_id\_structure
]]

local function citeseerx (id)
 local handler = cfg.id\_handlers['CITESEERX'];
 local matched;

 local text = external\_link\_id({link=handler.link, label=handler.label,
 prefix=handler.prefix, id=id, separator=handler.separator, encode=handler.encode,
 access=handler.access});

 matched = id:match ("^10%.1%.1%.[1-9]%d?%d?%d?%.[1-9]%d?%d?%d?$");
 if not matched then
 text = text .. ' ' .. set\_error( 'bad\_citeseerx' );
 end
 return text;
end

--[[--------------------------< D O I >------------------------------------------------------------------------

Formats a DOI and checks for DOI errors.

DOI names contain two parts: prefix and suffix separated by a forward slash.
 Prefix: directory indicator '10.' followed by a registrant code
 Suffix: character string of any length chosen by the registrant

This function checks a DOI name for: prefix/suffix. If the doi name contains spaces or endashes, or, if it ends
with a period or a comma, this function will emit a bad\_doi error message.

DOI names are case-insensitive and can incorporate any printable Unicode characters so the test for spaces, endash,
and terminal punctuation may not be technically correct but it appears, that in practice these characters are rarely
if ever used in doi names.

]]

local function doi(id, inactive, access)
 local cat = ""
 local handler = cfg.id\_handlers['DOI'];

 local text;
 if is\_set(inactive) then
 local inactive\_year = inactive:match("%d%d%d%d") or *; -- try to get the year portion from the inactive date*
 if is\_set(inactive\_year) then
 table.insert( z.error\_categories, "Pages with DOIs inactive since " .. inactive\_year );
 else
 table.insert( z.error\_categories, "Pages with inactive DOIs" ); -- when inactive doesn't contain a recognizable year
 end
 inactive = " (" .. cfg.messages['inactive'] .. " " .. inactive .. ")"
 end
 text = external\_link\_id({link = handler.link, label = handler.label,
 prefix=handler.prefix,id=id,separator=handler.separator, encode=handler.encode, access=access}) .. (inactive or *)*

 if nil == id:match("^10%.[^%s–]-/[^%s–]-[^%.,]$") then -- doi must begin with '10.', must contain a fwd slash, must not contain spaces or endashes, and must not end with period or comma
 cat = ' ' .. set\_error( 'bad\_doi' );
 end

 return text .. cat
end

--[[--------------------------< H D L >------------------------------------------------------------------------

Formats an HDL with minor error checking.

HDL names contain two parts: prefix and suffix separated by a forward slash.
 Prefix: character string using any character in the UCS-2 character set except '/'
 Suffix: character string of any length using any character in the UCS-2 character set chosen by the registrant

This function checks a HDL name for: prefix/suffix. If the HDL name contains spaces, endashes, or, if it ends
with a period or a comma, this function will emit a bad\_hdl error message.

HDL names are case-insensitive and can incorporate any printable Unicode characters so the test for endashes and
terminal punctuation may not be technically correct but it appears, that in practice these characters are rarely
if ever used in HDLs.

]]

local function hdl(id, access)
 local handler = cfg.id\_handlers['HDL'];

 local text = external\_link\_id({link = handler.link, label = handler.label,
 prefix=handler.prefix,id=id,separator=handler.separator, encode=handler.encode, access=access})

 if nil == id:match("^[^%s–]-/[^%s–]-[^%.,]$") then -- hdl must contain a fwd slash, must not contain spaces, endashes, and must not end with period or comma
 text = text .. ' ' .. set\_error( 'bad\_hdl' );
 end
 return text;
end

--[[--------------------------< I S B N >----------------------------------------------------------------------

Determines whether an ISBN string is valid

]]

local function isbn( isbn\_str )
 if nil ~= isbn\_str:match("[^%s-0-9X]") then
 return false, 'invalid character'; -- fail if isbn\_str contains anything but digits, hyphens, or the uppercase X
 end
 isbn\_str = isbn\_str:gsub( "-", "" ):gsub( " ", "" ); -- remove hyphens and spaces
 local len = isbn\_str:len();

 if len ~= 10 and len ~= 13 then
 return false, 'length'; -- fail if incorrect length
 end

 if len == 10 then
 if isbn\_str:match( "^%d\*X?$" ) == nil then -- fail if isbn\_str has 'X' anywhere but last position
 return false, 'invalid form';
 end
 return is\_valid\_isxn(isbn\_str, 10), 'checksum';
 else
 if isbn\_str:match( "^%d+$" ) == nil then
 return false, 'invalid character'; -- fail if isbn13 is not all digits
 end
 if isbn\_str:match( "^97[89]%d\*$" ) == nil then
 return false, 'invalid prefix'; -- fail when isbn13 does not begin with 978 or 979
 end
 return is\_valid\_isxn\_13 (isbn\_str), 'checksum';
 end
end

--[[--------------------------< A M A Z O N >------------------------------------------------------------------

Formats a link to Amazon. Do simple error checking: asin must be mix of 10 numeric or uppercase alpha
characters. If a mix, first character must be uppercase alpha; if all numeric, asins must be 10-digit
isbn. If 10-digit isbn, add a maintenance category so a bot or awb script can replace |asin= with |isbn=.
Error message if not 10 characters, if not isbn10, if mixed and first character is a digit.

This function is positioned here because it calls isbn()

]]

local function asin(id, domain)
 local err\_cat = ""

 if not id:match("^[%d%u][%d%u][%d%u][%d%u][%d%u][%d%u][%d%u][%d%u][%d%u][%d%u]$") then
 err\_cat = ' ' .. set\_error ('bad\_asin'); -- asin is not a mix of 10 uppercase alpha and numeric characters
 else
 if id:match("^%d%d%d%d%d%d%d%d%d[%dX]$") then -- if 10-digit numeric (or 9 digits with terminal X)
 if isbn( id ) then -- see if asin value is isbn10
 add\_maint\_cat ('ASIN');
 elseif not is\_set (err\_cat) then
 err\_cat = ' ' .. set\_error ('bad\_asin'); -- asin is not isbn10
 end
 elseif not id:match("^%u[%d%u]+$") then
 err\_cat = ' ' .. set\_error ('bad\_asin'); -- asin doesn't begin with uppercase alpha
 end
 end
 if not is\_set(domain) then
 domain = "com";
 elseif in\_array (domain, {'jp', 'uk'}) then -- Japan, United Kingdom
 domain = "co." .. domain;
 elseif in\_array (domain, {'au', 'br', 'mx'}) then -- Australia, Brazil, Mexico
 domain = "com." .. domain;
 end
 local handler = cfg.id\_handlers['ASIN'];
 return external\_link\_id({link=handler.link,
 label=handler.label, prefix=handler.prefix .. domain .. "/dp/",
 id=id, encode=handler.encode, separator = handler.separator}) .. err\_cat;
end

--[[--------------------------< I S M N >----------------------------------------------------------------------

Determines whether an ISMN string is valid. Similar to isbn-13, ismn is 13 digits begining 979-0-... and uses the
same check digit calculations. See http://www.ismn-international.org/download/Web\_ISMN\_Users\_Manual\_2008-6.pdf
section 2, pages 9–12.

]]

local function ismn (id)
 local handler = cfg.id\_handlers['ISMN'];
 local text;
 local valid\_ismn = true;
 local id\_copy;

 id\_copy = id; -- save a copy because this testing is destructive
 id=id:gsub( "[%s-–]", "" ); -- strip spaces, hyphens, and endashes from the ismn

 if 13 ~= id:len() or id:match( "^9790%d\*$" ) == nil then -- ismn must be 13 digits and begin 9790
 valid\_ismn = false;
 else
 valid\_ismn=is\_valid\_isxn\_13 (id); -- validate ismn
 end

-- text = internal\_link\_id({link = handler.link, label = handler.label, -- use this (or external version) when there is some place to link to
-- prefix=handler.prefix,id=id,separator=handler.separator, encode=handler.encode})

 text = table.concat (
 {
 make\_wikilink (handler.link, handler.label),
 handler.separator,
 id\_copy
 }); -- because no place to link to yet

 if false == valid\_ismn then
 text = text .. ' ' .. set\_error( 'bad\_ismn' ) -- add an error message if the ismn is invalid
 end

 return text;
end

--[[--------------------------< I S S N >----------------------------------------------------------------------

Validate and format an issn. This code fixes the case where an editor has included an ISSN in the citation but
has separated the two groups of four digits with a space. When that condition occurred, the resulting link looked
like this:

This code now prevents that by inserting a hyphen at the issn midpoint. It also validates the issn for length
and makes sure that the checkdigit agrees with the calculated value. Incorrect length (8 digits), characters
other than 0-9 and X, or checkdigit / calculated value mismatch will all cause a check issn error message. The
issn is always displayed with a hyphen, even if the issn was given as a single group of 8 digits.

]]

local function issn(id, e)
 local issn\_copy = id; -- save a copy of unadulterated issn; use this version for display if issn does not validate
 local handler;
 local text;
 local valid\_issn = true;

 if e then
 handler = cfg.id\_handlers['EISSN'];
 else
 handler = cfg.id\_handlers['ISSN'];
 end

 id=id:gsub( "[%s-–]", "" ); -- strip spaces, hyphens, and endashes from the issn

 if 8 ~= id:len() or nil == id:match( "^%d\*X?$" ) then -- validate the issn: 8 digits long, containing only 0-9 or X in the last position
 valid\_issn=false; -- wrong length or improper character
 else
 valid\_issn=is\_valid\_isxn(id, 8); -- validate issn
 end

 if true == valid\_issn then
 id = string.sub( id, 1, 4 ) .. "-" .. string.sub( id, 5 ); -- if valid, display correctly formatted version
 else
 id = issn\_copy; -- if not valid, use the show the invalid issn with error message
 end

 text = external\_link\_id({link = handler.link, label = handler.label,
 prefix=handler.prefix,id=id,separator=handler.separator, encode=handler.encode})

 if false == valid\_issn then
 text = text .. ' ' .. set\_error( 'bad\_issn', e and 'e' or  *) -- add an error message if the issn is invalid*
 end

 return text
end

--[[--------------------------< J F M >-----------------------------------------------------------------------

A numerical identifier in the form nn.nnnn.nn

]]

local function jfm (id)
 local handler = cfg.id\_handlers['JFM'];
 local id\_num;
 local err\_cat = *;*

 id\_num = id:match ('^[Jj][Ff][Mm](.\*)$'); -- identifier with jfm prefix; extract identifier

 if is\_set (id\_num) then
 add\_maint\_cat ('jfm\_format');
 else -- plain number without mr prefix
 id\_num = id; -- if here id does not have prefix
 end

 if id\_num and id\_num:match('^%d%d%.%d%d%d%d%.%d%d$') then
 id = id\_num; -- jfm matches pattern
 else
 err\_cat = ' ' .. set\_error( 'bad\_jfm' ); -- set an error message
 end

 return external\_link\_id({link = handler.link, label = handler.label,
 prefix=handler.prefix,id=id,separator=handler.separator, encode=handler.encode}) .. err\_cat;
end

--[[--------------------------< L C C N >----------------------------------------------------------------------

Format LCCN link and do simple error checking. LCCN is a character string 8-12 characters long. The length of
the LCCN dictates the character type of the first 1-3 characters; the rightmost eight are always digits.
http://info-uri.info/registry/OAIHandler?verb=GetRecord&metadataPrefix=reg&identifier=info:lccn/

length = 8 then all digits
length = 9 then lccn[1] is lower case alpha
length = 10 then lccn[1] and lccn[2] are both lower case alpha or both digits
length = 11 then lccn[1] is lower case alpha, lccn[2] and lccn[3] are both lower case alpha or both digits
length = 12 then lccn[1] and lccn[2] are both lower case alpha

]]

local function lccn(lccn)
 local handler = cfg.id\_handlers['LCCN'];
 local err\_cat = *; -- presume that LCCN is valid*
 local id = lccn; -- local copy of the lccn

 id = normalize\_lccn (id); -- get canonical form (no whitespace, hyphens, forward slashes)
 local len = id:len(); -- get the length of the lccn

 if 8 == len then
 if id:match("[^%d]") then -- if LCCN has anything but digits (nil if only digits)
 err\_cat = ' ' .. set\_error( 'bad\_lccn' ); -- set an error message
 end
 elseif 9 == len then -- LCCN should be adddddddd
 if nil == id:match("%l%d%d%d%d%d%d%d%d") then -- does it match our pattern?
 err\_cat = ' ' .. set\_error( 'bad\_lccn' ); -- set an error message
 end
 elseif 10 == len then -- LCCN should be aadddddddd or dddddddddd
 if id:match("[^%d]") then -- if LCCN has anything but digits (nil if only digits) ...
 if nil == id:match("^%l%l%d%d%d%d%d%d%d%d") then -- ... see if it matches our pattern
 err\_cat = ' ' .. set\_error( 'bad\_lccn' ); -- no match, set an error message
 end
 end
 elseif 11 == len then -- LCCN should be aaadddddddd or adddddddddd
 if not (id:match("^%l%l%l%d%d%d%d%d%d%d%d") or id:match("^%l%d%d%d%d%d%d%d%d%d%d")) then -- see if it matches one of our patterns
 err\_cat = ' ' .. set\_error( 'bad\_lccn' ); -- no match, set an error message
 end
 elseif 12 == len then -- LCCN should be aadddddddddd
 if not id:match("^%l%l%d%d%d%d%d%d%d%d%d%d") then -- see if it matches our pattern
 err\_cat = ' ' .. set\_error( 'bad\_lccn' ); -- no match, set an error message
 end
 else
 err\_cat = ' ' .. set\_error( 'bad\_lccn' ); -- wrong length, set an error message
 end

 if not is\_set (err\_cat) and nil ~= lccn:find ('%s') then
 err\_cat = ' ' .. set\_error( 'bad\_lccn' ); -- lccn contains a space, set an error message
 end

 return external\_link\_id({link = handler.link, label = handler.label,
 prefix=handler.prefix,id=lccn,separator=handler.separator, encode=handler.encode}) .. err\_cat;
end

--[[--------------------------< M R >--------------------------------------------------------------------------

A seven digit number; if not seven digits, zero-fill leading digits to make seven digits.

]]

local function mr (id)
 local handler = cfg.id\_handlers['MR'];
 local id\_num;
 local id\_len;
 local err\_cat = *;*

 id\_num = id:match ('^[Mm][Rr](%d+)$'); -- identifier with mr prefix

 if is\_set (id\_num) then
 add\_maint\_cat ('mr\_format');
 else -- plain number without mr prefix
 id\_num = id:match ('^%d+$'); -- if here id is all digits
 end

 id\_len = id\_num and id\_num:len() or 0;
 if (7 >= id\_len) and (0 ~= id\_len) then
 id = string.rep ('0', 7-id\_len ) .. id\_num; -- zero-fill leading digits
 else
 err\_cat = ' ' .. set\_error( 'bad\_mr' ); -- set an error message
 end

 return external\_link\_id({link = handler.link, label = handler.label,
 prefix=handler.prefix,id=id,separator=handler.separator, encode=handler.encode}) .. err\_cat;
end

--[[--------------------------< O C L C >----------------------------------------------------------------------

Validate and format an oclc id. https://www.oclc.org/batchload/controlnumber.en.html

]]

local function oclc (id)
 local handler = cfg.id\_handlers['OCLC'];
 local number;
 local err\_msg = *; -- empty string for concatenation*

 if id:match('^ocm%d%d%d%d%d%d%d%d$') then -- ocm prefix and 8 digits; 001 field (12 characters)
 number = id:match('ocm(%d+)'); -- get the number
 elseif id:match('^ocn%d%d%d%d%d%d%d%d%d$') then -- ocn prefix and 9 digits; 001 field (12 characters)
 number = id:match('ocn(%d+)'); -- get the number
 elseif id:match('^on%d%d%d%d%d%d%d%d%d%d+$') then -- on prefix and 10 or more digits; 001 field (12 characters)
 number = id:match('^on(%d%d%d%d%d%d%d%d%d%d+)$'); -- get the number
 elseif id:match('^%(OCoLC%)[1-9]%d\*$') then -- (OCoLC) prefix and variable number digits; no leading zeros; 035 field
 number = id:match('%(OCoLC%)([1-9]%d\*)'); -- get the number
 if 9 < number:len() then
 number = nil; -- contrain to 1 to 9 digits; change this when oclc issues 10-digit numbers
 end
 elseif id:match('^%d+$') then -- no prefix
 number = id; -- get the number
 if 10 < number:len() then
 number = nil; -- contrain to 1 to 10 digits; change this when oclc issues 11-digit numbers
 end
 end

 if number then -- proper format
 id = number; -- exclude prefix, if any, from external link
 else
 err\_msg = ' ' .. set\_error( 'bad\_oclc' ) -- add an error message if the id is malformed
 end

 local text = external\_link\_id({link=handler.link, label=handler.label,
 prefix=handler.prefix, id=id, separator=handler.separator, encode=handler.encode}) .. err\_msg;

 return text;
end

--[[--------------------------< O P E N L I B R A R Y >--------------------------------------------------------

Formats an OpenLibrary link, and checks for associated errors.

]]

local function openlibrary(id, access)
 local code;
 local handler = cfg.id\_handlers['OL'];
 local ident;

 ident, code = id:gsub('^OL', *):match("^(%d+([AMW]))$"); -- optional OL prefix followed immediately by digits followed by 'A', 'M', or 'W'; remove OL prefix*

 if not is\_set (ident) then -- if malformed return an error
 return external\_link\_id({link=handler.link, label=handler.label,
 prefix=handler.prefix .. 'OL',
 id=id, separator=handler.separator, encode = handler.encode,
 access = access}) .. ' ' .. set\_error( 'bad\_ol' );
 end

 id = ident; -- use ident without the optional OL prefix (it has been removed)

 if ( code == "A" ) then
 return external\_link\_id({link=handler.link, label=handler.label,
 prefix=handler.prefix .. 'authors/OL',
 id=id, separator=handler.separator, encode = handler.encode,
 access = access})
 end

 if ( code == "M" ) then
 return external\_link\_id({link=handler.link, label=handler.label,
 prefix=handler.prefix .. 'books/OL',
 id=id, separator=handler.separator, encode = handler.encode,
 access = access})
 end

 if ( code == "W" ) then
 return external\_link\_id({link=handler.link, label=handler.label,
 prefix=handler.prefix .. 'works/OL',
 id=id, separator=handler.separator, encode = handler.encode,
 access = access})
 end
end

--[[--------------------------< P M C >------------------------------------------------------------------------

Format a PMC, do simple error checking, and check for embargoed articles.

The embargo parameter takes a date for a value. If the embargo date is in the future the PMC identifier will not
be linked to the article. If the embargo date is today or in the past, or if it is empty or omitted, then the
PMC identifier is linked to the article through the link at cfg.id\_handlers['PMC'].prefix.

PMC embargo date testing is done in function is\_embargoed () which is called earlier because when the citation
has |pmc=<value> but does not have a |url= then |title= is linked with the PMC link. Function is\_embargoed ()
returns the embargo date if the PMC article is still embargoed, otherwise it returns an empty string.

PMCs are sequential numbers beginning at 1 and counting up. This code checks the PMC to see that it contains only digits and is less
than test\_limit; the value in local variable test\_limit will need to be updated periodically as more PMCs are issued.

]]

local function pmc(id, embargo)
 local test\_limit = 6500000; -- update this value as PMCs approach
 local handler = cfg.id\_handlers['PMC'];
 local err\_cat = *; -- presume that PMC is valid*
 local id\_num;
 local text;

 id\_num = id:match ('^[Pp][Mm][Cc](%d+)$'); -- identifier with pmc prefix

 if is\_set (id\_num) then
 add\_maint\_cat ('pmc\_format');
 else -- plain number without pmc prefix
 id\_num = id:match ('^%d+$'); -- if here id is all digits
 end

 if is\_set (id\_num) then -- id\_num has a value so test it
 id\_num = tonumber(id\_num); -- convert id\_num to a number for range testing
 if 1 > id\_num or test\_limit < id\_num then -- if PMC is outside test limit boundaries
 err\_cat = ' ' .. set\_error( 'bad\_pmc' ); -- set an error message
 else
 id = tostring (id\_num); -- make sure id is a string
 end
 else -- when id format incorrect
 err\_cat = ' ' .. set\_error( 'bad\_pmc' ); -- set an error message
 end

 if is\_set (embargo) then -- is PMC is still embargoed?
 text = table.concat ( -- still embargoed so no external link
 {
 make\_wikilink (handler.link, handler.label),
 handler.separator,
 id,
 err\_cat
 });
 else
 text = external\_link\_id({link = handler.link, label = handler.label, -- no embargo date or embargo has expired, ok to link to article
 prefix=handler.prefix,id=id,separator=handler.separator, encode=handler.encode, access=handler.access}) .. err\_cat;
 end
 return text;
end

--[[--------------------------< P M I D >----------------------------------------------------------------------

Format PMID and do simple error checking. PMIDs are sequential numbers beginning at 1 and counting up. This
code checks the PMID to see that it contains only digits and is less than test\_limit; the value in local variable
test\_limit will need to be updated periodically as more PMIDs are issued.

]]

local function pmid(id)
 local test\_limit = 32000000; -- update this value as PMIDs approach
 local handler = cfg.id\_handlers['PMID'];
 local err\_cat = *; -- presume that PMID is valid*

 if id:match("[^%d]") then -- if PMID has anything but digits
 err\_cat = ' ' .. set\_error( 'bad\_pmid' ); -- set an error message
 else -- PMID is only digits
 local id\_num = tonumber(id); -- convert id to a number for range testing
 if 1 > id\_num or test\_limit < id\_num then -- if PMID is outside test limit boundaries
 err\_cat = ' ' .. set\_error( 'bad\_pmid' ); -- set an error message
 end
 end

 return external\_link\_id({link = handler.link, label = handler.label,
 prefix=handler.prefix,id=id,separator=handler.separator, encode=handler.encode}) .. err\_cat;
end

--[[--------------------------< S S R N >----------------------------------------------------------------------

Format an ssrn, do simple error checking

SSRNs are sequential numbers beginning at 100? and counting up. This code checks the ssrn to see that it is
only digits and is greater than 99 and less than test\_limit; the value in local variable test\_limit will need
to be updated periodically as more SSRNs are issued.

]]

local function ssrn (id)
 local test\_limit = 3500000; -- update this value as SSRNs approach
 local handler = cfg.id\_handlers['SSRN'];
 local err\_cat = *; -- presume that SSRN is valid*
 local id\_num;
 local text;

 id\_num = id:match ('^%d+$'); -- id must be all digits

 if is\_set (id\_num) then -- id\_num has a value so test it
 id\_num = tonumber(id\_num); -- convert id\_num to a number for range testing
 if 100 > id\_num or test\_limit < id\_num then -- if SSRN is outside test limit boundaries
 err\_cat = ' ' .. set\_error( 'bad\_ssrn' ); -- set an error message
 end
 else -- when id format incorrect
 err\_cat = ' ' .. set\_error( 'bad\_ssrn' ); -- set an error message
 end

 text = external\_link\_id({link = handler.link, label = handler.label,
 prefix=handler.prefix,id=id,separator=handler.separator, encode=handler.encode, access=handler.access}) .. err\_cat;

 return text;
end

--[[--------------------------< U S E N E T \_ I D >------------------------------------------------------------

Validate and format a usenet message id. Simple error checking, looks for 'id-left@id-right' not enclosed in
'<' and/or '>' angle brackets.

]]

local function usenet\_id (id)
 local handler = cfg.id\_handlers['USENETID'];

 local text = external\_link\_id({link = handler.link, label = handler.label,
 prefix=handler.prefix,id=id,separator=handler.separator, encode=handler.encode})

 if not id:match('^.+@.+$') or not id:match('^[^<].\*[^>]$')then -- doesn't have '@' or has one or first or last character is '< or '>'
 text = text .. ' ' .. set\_error( 'bad\_usenet\_id' ) -- add an error message if the message id is invalid
 end

 return text
end

--[[--------------------------< Z B L >-----------------------------------------------------------------------

A numerical identifier in the form nnnn.nnnnn - leading zeros in the first quartet optional

]]

local function zbl (id)
 local handler = cfg.id\_handlers['ZBL'];
 local id\_num;
 local err\_cat = *;*

 id\_num = id:match ('^[Zz][Bb][Ll](.\*)$'); -- identifier with zbl prefix; extract identifier

 if is\_set (id\_num) then
 add\_maint\_cat ('zbl\_format');
 else -- plain number without zbl prefix
 id\_num = id; -- if here id does not have prefix
 end

 if id\_num:match('^%d?%d?%d?%d%.%d%d%d%d%d$') then
 id = id\_num; -- id matches pattern
 else
 err\_cat = ' ' .. set\_error( 'bad\_zbl' ); -- set an error message
 end

 return external\_link\_id({link = handler.link, label = handler.label,
 prefix=handler.prefix,id=id,separator=handler.separator, encode=handler.encode}) .. err\_cat;
end

--============================<< I N T E R F A C E F U N C T I O N S >>==========================================

--[[--------------------------< B U I L D \_ I D \_ L I S T >--------------------------------------------------------

Takes a table of IDs created by extract\_ids() and turns it into a table of formatted ID outputs.

inputs:
 id\_list – table of identifiers built by extract\_ids()
 options – table of various template parameter values used to modify some manually handled identifiers

]]

local function build\_id\_list( id\_list, options )
 local new\_list, handler = {};

 local function fallback(k) return { \_\_index = function(t,i) return cfg.id\_handlers[k][i] end } end;

 for k, v in pairs( id\_list ) do -- k is uc identifier name as index to cfg.id\_handlers; e.g. cfg.id\_handlers['ISBN'], v is a table
 -- fallback to read-only cfg
 handler = setmetatable( { ['id'] = v, ['access'] = options.IdAccessLevels[k] }, fallback(k) );

 if handler.mode == 'external' then
 table.insert( new\_list, {handler.label, external\_link\_id( handler ) } );
 elseif handler.mode == 'internal' then
 table.insert( new\_list, {handler.label, internal\_link\_id( handler ) } );
 elseif handler.mode ~= 'manual' then
 error( cfg.messages['unknown\_ID\_mode'] );
 elseif k == 'ARXIV' then
 table.insert( new\_list, {handler.label, arxiv( v, options.Class ) } );
 elseif k == 'ASIN' then
 table.insert( new\_list, {handler.label, asin( v, options.ASINTLD ) } );
 elseif k == 'BIBCODE' then
 table.insert( new\_list, {handler.label, bibcode( v, handler.access ) } );
 elseif k == 'BIORXIV' then
 table.insert( new\_list, {handler.label, biorxiv( v ) } );
 elseif k == 'CITESEERX' then
 table.insert( new\_list, {handler.label, citeseerx( v ) } );
 elseif k == 'DOI' then
 table.insert( new\_list, {handler.label, doi( v, options.DoiBroken, handler.access ) } );
 elseif k == 'EISSN' then
 table.insert( new\_list, {handler.label, issn( v, true ) } ); -- true distinguishes eissn from issn
 elseif k == 'HDL' then
 table.insert( new\_list, {handler.label, hdl( v, handler.access ) } );
 elseif k == 'ISBN' then
 local ISBN = internal\_link\_id( handler );
 local check;
 local err\_type = *;*
 check, err\_type = isbn( v );
 if not check then
 if is\_set(options.IgnoreISBN) then -- ISBN is invalid; if |ignore-isbn-error= set
 add\_maint\_cat ('ignore\_isbn\_err'); -- ad a maint category
 else
 ISBN = ISBN .. set\_error( 'bad\_isbn', {err\_type}, false, " ", "" ); -- else display an error message
 end
 elseif is\_set(options.IgnoreISBN) then -- ISBN is OK; if |ignore-isbn-error= set
 add\_maint\_cat ('ignore\_isbn\_err'); -- because |ignore-isbn-error= unnecessary
 end
 table.insert( new\_list, {handler.label, ISBN } );
 elseif k == 'ISMN' then
 table.insert( new\_list, {handler.label, ismn( v ) } );
 elseif k == 'ISSN' then
 table.insert( new\_list, {handler.label, issn( v ) } );
 elseif k == 'JFM' then
 table.insert( new\_list, {handler.label, jfm( v ) } );
 elseif k == 'LCCN' then
 table.insert( new\_list, {handler.label, lccn( v ) } );
 elseif k == 'MR' then
 table.insert( new\_list, {handler.label, mr( v ) } );
 elseif k == 'OCLC' then
 table.insert( new\_list, {handler.label, oclc( v ) } );
 elseif k == 'OL' or k == 'OLA' then
 table.insert( new\_list, {handler.label, openlibrary( v, handler.access ) } );
 elseif k == 'PMC' then
 table.insert( new\_list, {handler.label, pmc( v, options.Embargo ) } );
 elseif k == 'PMID' then
 table.insert( new\_list, {handler.label, pmid( v ) } );
 elseif k == 'SSRN' then
 table.insert( new\_list, {handler.label, ssrn( v ) } );
 elseif k == 'USENETID' then
 table.insert( new\_list, {handler.label, usenet\_id( v ) } );
 elseif k == 'ZBL' then
 table.insert( new\_list, {handler.label, zbl( v ) } );
 else
 error( cfg.messages['unknown\_manual\_ID'] );
 end
 end

 local function comp( a, b ) -- used in following table.sort()
 return a[1]:lower() < b[1]:lower();
 end

 table.sort( new\_list, comp );
 for k, v in ipairs( new\_list ) do
 new\_list[k] = v[2];
 end

 return new\_list;
end

--[[--------------------------< E X T R A C T \_ I D S >------------------------------------------------------------

Populates ID table from arguments using configuration settings. Loops through cfg.id\_handlers and searches args for
any of the parameters listed in each cfg.id\_handlers['...'].parameters. If found, adds the parameter and value to
the identifier list. Emits redundant error message is more than one alias exists in args

]]

local function extract\_ids( args )
 local id\_list = {}; -- list of identifiers found in args
 for k, v in pairs( cfg.id\_handlers ) do -- k is uc identifier name as index to cfg.id\_handlers; e.g. cfg.id\_handlers['ISBN'], v is a table
 v = select\_one( args, v.parameters, 'redundant\_parameters' ); -- v.parameters is a table of aliases for k; here we pick one from args if present
 if is\_set(v) then id\_list[k] = v; end -- if found in args, add identifier to our list
 end
 return id\_list;
end

--[[--------------------------< E X T R A C T \_ I D \_ A C C E S S \_ L E V E L S >--------------------------------------

Fetches custom id access levels from arguments using configuration settings.
Parameters which have a predefined access level (e.g. arxiv) do not use this
function as they are directly rendered as free without using an additional parameter.

]]

local function extract\_id\_access\_levels( args, id\_list )
 local id\_accesses\_list = {};
 for k, v in pairs( cfg.id\_handlers ) do
 local access\_param = v.custom\_access;
 local k\_lower = string.lower(k);
 if is\_set(access\_param) then
 local access\_level = args[access\_param];
 if is\_set(access\_level) then
 if not in\_array (access\_level:lower(), cfg.keywords['id-access']) then
 table.insert( z.message\_tail, { set\_error( 'invalid\_param\_val', {access\_param, access\_level}, true ) } );
 access\_level = nil;
 end
 if not is\_set(id\_list[k]) then
 table.insert( z.message\_tail, { set\_error( 'param\_access\_requires\_param', {k\_lower}, true ) } );
 end
 if is\_set(access\_level) then
 access\_level = access\_level:lower();
 end
 id\_accesses\_list[k] = access\_level;
 end
 end
 end
 return id\_accesses\_list;
end

--[[--------------------------< S E T \_ S E L E C T E D \_ M O D U L E S >--------------------------------------

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

]]

local function set\_selected\_modules (cfg\_table\_ptr, utilities\_page\_ptr)
 cfg = cfg\_table\_ptr;

 is\_set = utilities\_page\_ptr.is\_set; -- import functions from select Module:Citation/CS1/Utilities module
 in\_array = utilities\_page\_ptr.in\_array;
 set\_error = utilities\_page\_ptr.set\_error;
 select\_one = utilities\_page\_ptr.select\_one;
 add\_maint\_cat = utilities\_page\_ptr.add\_maint\_cat;
 substitute = utilities\_page\_ptr.substitute;
 make\_wikilink = utilities\_page\_ptr.make\_wikilink;

 z = utilities\_page\_ptr.z; -- table of tables in Module:Citation/CS1/Utilities
end

return {
 build\_id\_list = build\_id\_list,
 extract\_ids = extract\_ids,
 extract\_id\_access\_levels = extract\_id\_access\_levels,
 is\_embargoed = is\_embargoed;
 set\_selected\_modules = set\_selected\_modules;
 }