Module:Gaps

local p = {}

local getArgs

function p.main(frame)
 if not getArgs then
  getArgs = require('Module:Arguments').getArgs
 end
 local args = getArgs(frame, {wrappers = 'Template:Gaps'})

 local ret = mw.html.create('span')
  :css({['white-space'] = 'nowrap',
    ['font-size'] = args.size})

 if args.lhs then
  ret:wikitext(args.lhs .. ' = ')
 end

 local gap = string.lower(args.gap or '')
 
 local gapSize, gapUnit = string.match(gap,'([%d%.]+)%s*([ep][mnx])')
 
 local acceptedUnits = { em = 'em', en = 'en', px = 'px' }
 
 gapUnit = acceptedUnits[gapUnit]
 
 if gapSize and gapUnit then
  gap = gapSize..gapUnit
 else
  gap = '0.25em'
 end
 
 for k,v in ipairs(args) do
  if k == 1 then
   ret:wikitext(v)
  else
   ret:tag('span')
    :css('margin-left',gap)
    :wikitext(v)
  end
 end

 if args.e then
  ret
   :tag('span')
    :css({['margin-left'] = '0.27em',
      ['margin-right']= '0.27em'})
    :wikitext('×')
   :done()
   :wikitext(args.base or '10')
   :tag('span')
    :css('display','none')
    :wikitext('^')
   :done()
   :tag('sup')
    -- the double parentheses here are not redundant.
    -- they keep the second return value from being passed
    :wikitext((mw.ustring.gsub(args.e,'-','−')))
   :done()
 end

 if args.u then
  ret:wikitext(' ' .. args.u)
 end

 return ret
end

return p