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-- Functions to access Wikidata for Module:Convert.
 
local function collection()
	-- Return a table to hold items.
	return {
		n = 0,
		add = function (self, item)
			self.n = self.n + 1
			self[self.n] = item
		end,
		join = function (self, sep)
			return table.concat(self, sep)
		end,
	}
end
 
local function strip_to_nil(text)
	-- If text is a non-empty string, return its trimmed content,
	-- otherwise return nothing (empty string or not a string).
	if type(text) == 'string' then
		return text:match('(%S.-)%s*$')
	end
end
 
local function make_unit(units, parms, uid)
	-- Return a unit code for convert or nil if unit unknown.
	-- If necessary, add a dummy unit to parms so convert will use it
	-- for the input without attempting a conversion since nothing
	-- useful is available (for example, with unit volt).
	local unit = units[uid]
	if type(unit) ~= 'table' then
		return nil
	end
	local ucode = unit.ucode
	if ucode and not unit.si then
		return ucode                -- a unit known to convert
	end
	parms.opt_ignore_error = true
	ucode = ucode or unit._ucode    -- must be a non-empty string
	local ukey, utable
	if unit.si then
		local base = units[unit.si]
		ukey = base.symbol          -- must be a non-empty string
		local n1 = base.name1
		local n2 = base.name2
		if not n1 then
			n1 = ukey
			n2 = n2 or n1           -- do not append 's'
		end
		utable = {
			_symbol = ukey,
			_name1 = n1,
			_name2 = n2,
			link = unit.link or base.link,
			utype = n1,
			prefixes = 1,
		}
	else
		ukey = ucode
		utable = {
			symbol = ucode,         -- must be a non-empty string
			name1 = unit.name1,     -- if nil, uses symbol
			name2 = unit.name2,     -- if nil, uses name1..'s'
			link = unit.link,       -- if nil, uses name1
			utype = unit.name1 or ucode,
		}
	end
	utable.scale = 1
	utable.default = ''
	utable.defkey = ''
	utable.linkey = ''
	utable.bad_mcode = ''
	parms.unittable = { [ukey] = utable }
	return ucode
end
 
local function get_statements(qid, pid)
	-- Get item for qid and return a list of statements for property pid.
	-- Statements are in Wikidata's order except that those with preferred
	-- rank are first, then normal rank. Any other rank is ignored.
	-- qid is nil for the current page's item, or is an item id (expensive).
	local result, n = {}, 0
	local entity = mw.wikibase.getEntity(qid)
	if type(entity) == 'table' then
		local statements = (entity.claims or {})[pid]
		if type(statements) == 'table' then
			for _, rank in ipairs({ 'preferred', 'normal' }) do
				for _, statement in ipairs(statements) do
					if type(statement) == 'table' and rank == statement.rank then
						n = n + 1
						result[n] = statement
					end
				end
			end
		end
	end
	return result
end
 
local function input_from_property(tdata, parms, qid, pid)
	-- Given that pid is a Wikidata property identifier like 'P123',
	-- return amount, ucode (two strings) for the item/property,
	-- or return nothing.
	for _, statement in ipairs(get_statements(qid, pid)) do
		if statement.mainsnak and statement.mainsnak.datatype == 'quantity' then
			local value = (statement.mainsnak.datavalue or {}).value
			if value then
				local amount = value.amount
				if amount then
					amount = tostring(amount)  -- in case amount is ever a number
					if amount:sub(1, 1) == '+' then
						amount = amount:sub(2)
					end
					local unit = value.unit
					if type(unit) == 'string' then
						unit = unit:match('Q%d+$')  -- unit qid is at end of URL
						local ucode = make_unit(tdata.wikidata_units, parms, unit)
						if ucode then
							return amount, ucode
						end
					end
				end
			end
		end
	end
end
 
local function input_from_text(tdata, parms, text)
	-- Given string should be of form "<value><space><unit>".
	-- Return value, ucode (two strings), or return nothing.
	text = text:gsub('&nbsp;', ' '):gsub('  +', ' ')
	local pos = text:find(' ', 1, true)
	if pos then
		-- Leave checking of value to convert which can handle fractions.
		local value = text:sub(1, pos - 1)
		local uid = text:sub(pos + 1)
		local ucode = make_unit(tdata.wikidata_units, parms, uid)
		return value, ucode or uid
	end
end
 
local function adjustparameters(tdata, parms, index)
	-- For Module:Convert, adjust parms (a table of {{convert}} parameters).
	-- Return true if successful or return false, t where t is an error message table.
	-- This is intended mainly for use in infoboxes where the input might be
	--    <value><space><unit>    or
	--    <wikidata-property-id>  (uses an optional qid item id)
	-- If successful, insert value and unit in parms, before given index.
	local amount, ucode
	local text = parms.input  -- should be a trimmed, non-empty string
	local qid = strip_to_nil(parms.qid)
	local pid = text:match('^P%d+$')
	if pid then
		parms.input_text = ''  -- output an empty string if an error occurs
		amount, ucode = input_from_property(tdata, parms, qid, pid)
	else
		amount, ucode = input_from_text(tdata, parms, text)
	end
	if amount and ucode then
		table.insert(parms, index, ucode)
		table.insert(parms, index, amount)
		return true
	end
	return false, pid and { 'cvt_no_output' } or { 'cvt_bad_input', text }
end
 
--------------------------------------------------------------------------------
--- List units and check syntax of definitions ---------------------------------
--------------------------------------------------------------------------------
local specifications = {
	-- seq = sequence in which fields are displayed
	base = {
		title = 'SI base units',
		fields = {
			symbol = { seq = 2, mandatory = true },
			name1  = { seq = 3, mandatory = true },
			name2  = { seq = 4 },
			link   = { seq = 5 },
		},
		noteseq = 6,
		header = '{| class="wikitable"\n!si !!symbol !!name1 !!name2 !!link !!note',
		item = '|-\n|%s ||%s ||%s ||%s ||%s ||%s',
		footer = '|}',
	},
	alias = {
		title = 'Aliases for convert',
		fields = {
			ucode  = { seq = 2, mandatory = true },
			si     = { seq = 3 },
		},
		noteseq = 4,
		header = '{| class="wikitable"\n!alias !!ucode !!base !!note',
		item = '|-\n|%s ||%s ||%s ||%s',
		footer = '|}',
	},
	known = {
		title = 'Units known to convert',
		fields = {
			ucode  = { seq = 2, mandatory = true },
			label  = { seq = 3, mandatory = true },
		},
		noteseq = 4,
		header = '{| class="wikitable"\n!qid !!ucode !!label !!note',
		item = '|-\n|%s ||%s ||%s ||%s',
		footer = '|}',
	},
	unknown = {
		title = 'Units not known to convert',
		fields = {
			_ucode = { seq = 2, mandatory = true },
			si     = { seq = 3 },
			name1  = { seq = 4 },
			name2  = { seq = 5 },
			link   = { seq = 6 },
			label  = { seq = 7, mandatory = true },
		},
		noteseq = 8,
		header = '{| class="wikitable"\n!qid !!_ucode !!base !!name1 !!name2 !!link !!label !!note',
		item = '|-\n|%s ||%s ||%s ||%s ||%s ||%s ||%s ||%s',
		footer = '|}',
	},
}
 
local function listunits(tdata, ulookup)
	-- For Module:Convert, make wikitext to list the built-in Wikidata units.
	-- Return true, wikitext if successful or return false, t where t is an
	-- error message table. Currently, an error return never occurs.
	-- The syntax of each unit definition is checked and a note is added if
	-- a problem is detected.
	local function safe_cells(t)
		-- This is not currently needed, but in case definitions ever use wikitext
		-- like '[[kilogram|kg]]', escape the text so it works in a table cell.
		local result = {}
		for i, v in ipairs(t) do
			if v:find('|', 1, true) then
				v = v:gsub('(%[%[[^%[%]]-)|(.-%]%])', '%1\0%2')  -- replace pipe in piped link with a zero byte
				v = v:gsub('|', '&#124;')                        -- escape '|'
				v = v:gsub('%z', '|')                            -- restore pipe in piped link
			end
			result[i] = v:gsub('{', '&#123;')                    -- escape '{'
		end
		return unpack(result)
	end
	local wdunits = tdata.wikidata_units
	local speckeys = { 'base', 'alias', 'unknown', 'known' }
	for _, sid in ipairs(speckeys) do
		specifications[sid].units = collection()
	end
	local keys, n = {}, 0
	for k, v in pairs(wdunits) do
		n = n + 1
		keys[n] = k
	end
	table.sort(keys)
	local note_count = 0
	for _, key in ipairs(keys) do
		local unit = wdunits[key]
		local ktext, sid
		if key:match('^Q%d+$') then
			ktext = '[[d:' .. key .. '|' .. key .. ']]'
			if unit.ucode then
				sid = 'known'
			else
				sid = 'unknown'
			end
		elseif unit.ucode then
			ktext = key
			sid = 'alias'
		else
			ktext = key
			sid = 'base'
		end
		local result = { ktext }
		local spec = specifications[sid]
		local fields = spec.fields
		local note = collection()
		for k, v in pairs(unit) do
			if fields[k] then
				local seq = fields[k].seq
				if result[seq] then
					note:add('duplicate ' .. k)  -- cannot happen since keys are unique
				else
					result[seq] = v
				end
			else
				note:add('invalid ' .. k)
			end
		end
		for k, v in pairs(fields) do
			local value = result[v.seq]
			if value then
				if k == 'si' and not wdunits[value] then
					note:add('need si ' .. value)
				end
				if k == 'label' then
					local wdl = mw.wikibase.label(key)
					if wdl ~= value then
						note:add('label changed to ' .. tostring(wdl))
					end
				end
			else
				result[v.seq] = ''
				if v.mandatory then
					note:add('missing ' .. k)
				end
			end
		end
		local text
		if note.n > 0 then
			note_count = note_count + 1
			text = '*' .. note:join('<br />')
		end
		result[spec.noteseq] = text or ''
		spec.units:add(result)
	end
	local results = collection()
	if note_count > 0 then
		local text = note_count .. (note_count == 1 and ' note' or ' notes')
		results:add("'''Search for * to see " .. text .. "'''\n")
	end
	for _, sid in ipairs(speckeys) do
		local spec = specifications[sid]
		results:add("'''" .. spec.title .. "'''")
		results:add(spec.header)
		local fmt = spec.item
		for _, unit in ipairs(spec.units) do
			results:add(string.format(fmt, safe_cells(unit)))
		end
		results:add(spec.footer)
	end
	return true, results:join('\n')
end
 
return { _adjustparameters = adjustparameters, _listunits = listunits }

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