Preview quiver diagrams in pandoc HTML and LaTeX

quiver.lua

-- Install: save the file in $(pandoc data dir)/filters
-- pandoc --filter quiver.lua
-- call this filter before any cross-referencing filters like xnos or crossref

-- Markdown syntax:
-- :::{.quiver #eq:label}
-- <paste LateX Output from q.uiver.app <including the link>
-- :::
-- Reference with -@eq:label for just the number without eq. prefix.

function Div(div)
  if div.classes[1] == 'quiver' then
    local content = div.content[1].content
    if (content[3].text:match "https://q%.uiver%.app/.+") then
        link = content[3].text
        if FORMAT:match 'html' then
            return pandoc.Div({pandoc.Div(
         {pandoc.RawBlock(FORMAT,
            '<iframe class="quiver-embed" src="' .. link ..
            '&embed" width="488" height="332" border: none"></iframe>')},
         {class='quiver', style='display: flex; justify-content: center;'}),
        pandoc.Para({pandoc.Math('DisplayMath', ''),
        pandoc.Str('{#' .. div.identifier .. '}')}),
        }
        )
        elseif FORMAT:match 'latex' then
            local math = content[5].text:gsub("%$%$", "")
            return pandoc.Para({
                pandoc.Math('DisplayMath', math),
                pandoc.Str('{#' .. div.identifier .. '}'),
            })
        else
            print("WARNING unknown quiver format:" .. FORMAT)
            return div
        end
    else
        print("WARNING: Quiver div without a quiver link!")
        return div
    end
  else
    return div
  end
end