local p = {}
local TwitterSnowflake = require('Module:TwitterSnowflake')
local CiteWeb = require('Module:Cite web')['']

local err_msgs_t = {															-- a sequence of snowflake date error messages; all must be terminated with a semicolon (;)
	' <kbd>&#124;date=</kbd> / <kbd>&#124;number=</kbd> mismatch;',				-- [1]
	' <kbd>&#124;date=</kbd> required;',										-- [2]
	' Invalid <kbd>&#124;number=</kbd>;',										-- [3]
	' Missing or empty <kbd>&#124;number=</kbd>;',								-- [4]
	' Missing or empty <kbd>&#124;user=</kbd>;'									-- [5]

--[[--------------------------< M A I N >----------------------------------------------------------------------

p.main = function(frame)
	return p[''](frame)

--[[--------------------------< S U P P R E S S _ U R L _ I N _ T I T L E >------------------------------------

This function searches for and suppresses urls in |title=, |script-title=, and |trans-title= parameters so that
((cite web)) won't emit 'External link in |title=' error messages when rendered In the redering, urls are correctly
formed as they were in the original tweet.  The function looks for valid schemes and then wraps them in
<nowiki>..</nowiki> tags.


local function suppress_url_in_title (frame, title)
	local schemes = {															-- schemes commonly found in tweets

	if title then																-- when there is a title, suppress any urls with known schemes; abandon else
		for _, scheme in ipairs (schemes) do									-- spin through the list of schemes looking for a match
			title = title:gsub (scheme, frame:callParserFunction ('#tag', {'nowiki', scheme}));	-- replace the scheme with its nowiki'd form (a strip marker)

	return title;																-- done; return <title> modified or not

--[[--------------------------< D A T E _ N U M B E R _ U R L _ G E T >----------------------------------------

extract |date= and |number= parameter values if present.  Extract date from |number= and compare to |date=.

contruct |url= for ((cite web)) from the base url and |number= and |user=

returns nothing; adds date, number, url to <cite_args_t>; adds error message(s) to <errors_t>.


local function date_number_url_get (args_t, cite_args_t, errors_t)
	local err_msg_index;

	cite_args_t.url = 'https://twitter.com/';									-- initialize with minimal base url because ((cite web)) requires |url=
	if not args_t.user then
		table.insert (errors_t, err_msgs_t[5]);									-- error: missing or empty |user=

	if not args_t.date and not args_t.number then
		err_msg_index = 4;														-- error: missing or empty |number=
	elseif tonumber (args_t.number) then										-- |number= without |date=? use number
			cite_args_t.date = TwitterSnowflake.snowflakeToDate ({ args = {id_str = args_t.number} });	-- sets cite_args_t.date post-date or to 'November 4, 2010' when tweet posted before that date
			cite_args_t.number = args_t.number;

			if args_t.user then													-- |number= appears to have a valid value; if |user= has a value
				cite_args_t.url = cite_args_t.url .. args_t.user .. '/status/' .. args_t.number;	-- construct |url= for ((cite web))
	elseif args_t.number then													-- |number= with a value that can't be converted to a number; invalid
		err_msg_index = 3;														-- error: invalid number (couldn't convert to number)
	elseif not args_t.number then												-- |date= without |number= use date
		cite_args_t.date = args_t.date;											-- |date= has a value, use it
		err_msg_index = 4;														-- error: missing or empty |number=

	if err_msg_index then
		table.insert (errors_t, err_msgs_t[err_msg_index]);						-- invalid number or missing necessary parameters so abandon

	err_msg_index = TwitterSnowflake.datecheck ({ args = {						-- returns error message index number on error; nil else
		id_str	= args_t.number or '',
		date	= args_t.date or '',
		error1	= 1,															-- these numbers are indexes into <err_msgs_t> to override snowflake default error messages
		error2  = 2,															-- done this way to avoid long string comparison looking for
		error3	= 3																-- the undated-pre-twitter-epoch-post message

	if	2 == err_msg_index then													-- when no date and posted before twitter epoch
		cite_args_t.date = nil;													-- suppress default date because ((cite tweet)) should not claim in its own voice that the undated post was posted 2010-11-04
	table.insert (errors_t, err_msgs_t[err_msg_index]);							-- add error message

--[[--------------------------< p[''] >------------------------------------------------------------------------

construct parameter set for ((cite web)) from ((cite tweet)) parameters;  do some error checking


p[''] = function(frame)
	local args_t = require ('Module:Arguments').getArgs (frame);

	local cite_args_t = {
		title = suppress_url_in_title (frame, args_t.title),
		['script-title'] = suppress_url_in_title (frame, args_t['script-title']),
		['trans-title'] = suppress_url_in_title (frame, args_t['trans-title']),
		language = args_t.language,
		last1 = args_t.last1 or args_t.last,
		first1 = args_t.first1 or args_t.first,
		author1 = args_t.author1 or args_t.author,
		['author-link'] = args_t['author-link'] or args_t.authorlink,
		others = args_t.retweet and ('Retweeted by ' .. args_t.retweet),
		via = args_t.link == 'no' and 'Twitter' or '[[Twitter]]',
		type = 'Tweet',
		location = args_t.location,												-- why |location=?  tweets are online; there is no publication place
		['access-date'] = args_t['access-date'] or args_t.accessdate,
		['archive-date'] = args_t['archive-date'] or args_t.archivedate,
		['archive-url'] = args_t['archive-url'] or args_t.archiveurl,
		['url-status'] = args_t['url-status'],
		quote = args_t.quote,
		ref = args_t.ref,
		df = args_t.df,
		mode = args_t.mode

	local errors_t = {'<span class="cs1-visible-error citation-comment"> <kbd>(([[Template:Cite tweet|Cite tweet]]))</kbd>:'};		-- initialize sequence of error messages with style tag
	date_number_url_get (args_t, cite_args_t, errors_t);						-- add |date=, |number=, |url= to <cite_args_t>

	local author = ((cite_args_t.last1 and cite_args_t.first1) and cite_args_t.last1 .. ', ' .. cite_args_t.first1) or	-- concatenate |last= with |first= for |author-mask=
		(cite_args_t.last1 and cite_args_t.last1) or							-- only |last= for |author-mask=
		(cite_args_t.author1 and cite_args_t.author1:gsub('^%(%((.+)%)%)$', '%1'));	-- |author= or |author1= stripped of accept-as-written markup for |author-mask=

	if author and args_t.user then
		cite_args_t['author-mask'] = author .. ' [@' .. (args_t.user or '') .. ']'	-- concatenate <author> and |user= into |author-mask=
	elseif args_t.user then
		cite_args_t.author1 = '((' .. args_t.user .. '))';						-- just the user name for cs1|2 metadata
		cite_args_t['author-mask'] = '@' .. args_t.user;						-- make a mask for display
	else																		-- here when neither <author> nor |user=
		cite_args_t.author1 = nil;												-- so unset

	frame.args = cite_args_t;													-- overwrite frame arguments
	local rendering = CiteWeb (frame);											-- render the template

---------- error messaging ----------
	if errors_t[2] then															-- errors_t[2] nil when no errors
		if rendering:find ('cs1-visible-error', 1, true) then					-- rendered ((cite web)) with errors will have this string
			errors_t[1] = errors_t[1]:gsub ('> <', '>; <');						-- insert semicolon to terminate cs1|2 error message string

		errors_t[#errors_t] = errors_t[#errors_t]:gsub (';$',' ([[Template:Cite_tweet#Error_detection|help]])');	-- replace trailing semicolon with help link
		table.insert (errors_t, '</span>');										-- close style span tag
		if mw.title.getCurrentTitle():inNamespace (0) then						-- mainspace only
			table.insert (errors_t, '[[Category:Cite tweet templates with errors]]');	-- add error category

		rendering = rendering .. table.concat (errors_t);						-- append error messaging, help links and catagories
	return rendering;

return p