Module:Get cell

-- This module serves to calculate a table cell out of the values of other cells
-- Documentation: https://en.wikipedia.org/wiki/Module:Calculated_cell
-- Authors: Sophivorus
-- License: GNU General Public License 3 or later (http://www.gnu.org/licenses/gpl-3.0.html)
local CalculatedCell = {}

local WikitextParser = require( 'Module:WikitextParser' )

local function getError( key )
	local messages = {
		['no-table-id'] = 'No table id given',
		['page-not-found'] = 'Page not found',
		['table-not-found'] = 'Table not found'
	}
	local frame = mw.getCurrentFrame()
	local message = frame.args[ key ] or messages[ key ]
	return mw.html.create( 'span' ):addClass( 'error' ):wikitext( message )
end

function CalculatedCell.main( frame )

	-- Get the template parameters
	local params = frame:getParent().args

	-- Get the page wikitext
	local pageTitle = mw.title.getCurrentTitle()
	local page = params[3]
	if page then
		pageTitle = mw.title.new( page )
	end
	if not pageTitle then
		return getError( 'page-not-found' )
	end
	local pageWikitext = pageTitle:getContent()

	-- Get the table data
	local tableId = params[2]
	if not tableId then
		return getError( 'no-table-id' )
	end
	local tableWikitext = WikitextParser.getTableById( pageWikitext, tableId )
	local tableData = WikitextParser.getTableData( tableWikitext )

	-- Replace any placeholders (A1, B2, etc) in the given expression for the real values
	local expression = params[1]
	if not expression then
		return
	end
	local lang = mw.language.getContentLanguage()
	local rowLetter, rowNumber, rowData, cellNumber, cellValue
	for placeholder in string.gmatch( expression, '[A-Z]+[0-9]+' ) do
		rowLetter = string.match( placeholder, '[A-Z]+' )
		rowNumber = string.find( 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', rowLetter )
		rowData = tableData[ rowNumber ]
		cellNumber = tonumber( string.match( placeholder, '[0-9]+' ) )
		cellValue = rowData[ cellNumber ]
		cellValue = lang:parseFormattedNumber( cellValue )
		expression = string.gsub( expression, placeholder, cellValue )
	end

	return frame:callParserFunction( '#expr', expression )
end

return CalculatedCell