Module:City

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

local p = {}

function p.qCode(place)
	-- recover a q-code based on place name, also if one can link to a page on commons return such link
	local item, link = nil, nil

    -- === STEP 1: if "place" is empty than return nothing ==============
	if (not place) or (place == "") then
		return item, link
	end
	
  -- === STEP 2: Check if "place"  holds a q-code or matches any of the hardwired names  ==============
	if string.match(place, "^Q%d+$") then
		return place, link -- place string contains a q-code
	else
		-- if multiple calls to {{City}} from a single file, than mw.loadData should load [[Module:City/data]] only once
		local LookupTable = mw.loadData("Module:City/data")
		item = LookupTable[mw.ustring.lower(place)]
		if item then
			return item, link
		end
	end

	-- === STEP 3: Check if {{{1}}} matches existing template, gallery or category and if so provide the link  ===
	if #place>=3 and #place<40 then
		local page = mw.title.new( place, '' )
		if page and page.exists then
			item = mw.wikibase.getEntityIdForTitle( place )
			link = "[[" .. place .. "]]"
			if item then
				return item, link
			end
		end
		
		page = mw.title.new( place, 'category' )
		if page and page.exists then
			item = mw.wikibase.getEntityIdForTitle( 'Category:' .. place )
			link = "[[:Category:" .. place .. "|" .. place .. "]]"
			if item then
				entity = mw.wikibase.getEntityObject(item)
				if entity then 
					local s = entity:getBestStatements( 'P31' )
					if s[1] and s[1].mainsnak.datavalue.value.id=="Q4167836" then 
						-- if "instance of "(P31) = "Wikimedia category" (Q4167836)
						s = entity:getBestStatements( 'P301' ) -- category's main topic 
						if s[1] then -- if property "category's main topic" (P301) is set
							item = s[1].mainsnak.datavalue.value.id 
						else
							item = nil
						end
					end
				end
			end
		end 
	end
	return item, link
end

function p._city(place, lang, link)
	if (not place) or (place == "") then
		return "" --if "place" is empty than do nothing
	end
	
	if string.match(place, "[%{%{|%[%[].+[%}%}|%]%]]") then
		return place --  if "place" already has a link and if so than skip the rest of the template
	end
	
    -- Check if we can recover a q-code 
	local item, linkStr = p.qCode(place)
	if item then
		local wikidata = require("Module:Wikidata label")
		return wikidata._getLabel(item, lang, link)
	elseif linkStr then
		return linkStr -- no q-code but we matched one of the galleries or categories
	end

	-- return as is
	return place
end

function p.city(frame)
	local args = frame.args
	if not (args.lang and mw.language.isSupportedLanguage(args.lang)) then 
		args.lang = frame:callParserFunction( "int", "lang" ) -- get user's chosen language 
	end
	if (not args.link) or (mw.text.trim(args.link) == "") then
		args.link = "wikipedia"
	end
	args.place = mw.text.trim(args.place or '')
	return p._city(args.place, args.lang, args.link)
end

return p