citation-backlinks.lua

-- Todo: even with link-citations and link-fields turned off, citation-backlinks still adds a single backlink to each reference in the final bibliography div.

--- citation-backlinks.lua – adds citation backlinks to the bibliography
---
--- Copyright: © 2023 John MacFarlane and Albert Krewinkel and Bernardo Vasconcelos
--- License: MIT – see LICENSE for details

-- Makes sure users know if their pandoc version is too old for this
-- filter.
PANDOC_VERSION:must_be_at_least '2.17'

-- cites is a table mapping citation item identifiers
-- to an array of cite identifiers
local cites = {}

-- counter for cite identifiers
local cite_number = 1

local function with_label(s, el)
  if FORMAT == "latex" then
    -- return {pandoc.RawInline("latex", "\\pagelabel{" .. s .. "}"), el}
    return {pandoc.RawInline("latex", "\\label{" .. s .. "}"), el}
  end
  if FORMAT == "typst" then
    return {el, pandoc.RawInline("typst", " #label(\"" .. s .. "\")")}
  end
  if FORMAT == "docx" or FORMAT == "html" then
    return {el}
  end
end

function Cite(el)
  local cite_id = "cite_" .. cite_number
  cite_number = cite_number + 1
  for _,citation in ipairs(el.citations) do
    if cites[citation.id] then
      table.insert(cites[citation.id], cite_id)
    else
      cites[citation.id] = {cite_id}
    end
  end
  if FORMAT == "typst" then
    return pandoc.Span(with_label(cite_id, el))
  else
    return pandoc.Span(with_label(cite_id, el), pandoc.Attr(cite_id))
  end
end

function append_inline(blocks, inlines)
  local last = blocks[#blocks]
  if last.t == 'Para' or last.t == 'Plain' then
    -- append to last block
    last.content:extend(inlines)
  else
    -- append as additional block
    blocks[#blocks + 1] = pandoc.Plain(inlines)
  end
  return blocks
end

function Div(el)
  local citation_id = el.identifier:match("ref%-(.+)")
  local tex_return_link = pandoc.RawInline("latex", "\\Acrobatmenu{GoBack}{$\\hookleftarrow$}")

  if citation_id then
    local backlinks = pandoc.Inlines{pandoc.Space(), pandoc.Str("[")}
    if FORMAT == "latex" then
      -- quarto.doc.include_text("in-header", [[ \newcommand\pagelabel{\phantomsection\label} ]])
      table.insert(backlinks, tex_return_link)
    end

    for i,cite_id in ipairs(cites[citation_id] or {}) do
      local marker = pandoc.Str(i)
      if FORMAT == "latex" then
        marker = pandoc.RawInline("latex", "\\pageref{" .. cite_id .. "}")
      end
      if #backlinks > 2 then
        table.insert(backlinks, pandoc.Str(","))
        table.insert(backlinks, pandoc.Space())
      end
      table.insert(backlinks, pandoc.Link(marker, "#"..cite_id))
    end
    if #backlinks > 2 then
      append_inline(el.content, backlinks .. {pandoc.Str("]")})
    end
    return el
  end
end