multibib.lua

--[[
multibib – create multiple bibliographies

Copyright © 2018-2022 Albert Krewinkel

Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
]]

-- --citeproc was added in 2.11, so we never use the old pandoc-citeproc
PANDOC_VERSION:must_be_at_least '2.11'

local List = require 'pandoc.List'
local utils = require 'pandoc.utils'
local stringify = utils.stringify
local run_json_filter = utils.run_json_filter

--- get the type of meta object
local metatype = pandoc.utils.type or
  function (v)
    local metatag = type(v) == 'table' and v.t and v.t:gsub('^Meta', '')
    return metatag and metatag ~= 'Map' and metatag or type(v)
  end

--- Collection of all cites in the document
local all_cites = {}

--- Document meta value
local doc_meta = pandoc.Meta{}

--- Div used by citeproc to insert the bibliography.
local refs_div = pandoc.Div({}, pandoc.Attr('refs'))

--- 'references' metadata for each topic
local topic_refs = {}

-- Div filled by citeproc with properties set according to
-- the output format and the attributes of cs:bibliography
local refs_div_with_properties

-- Whether utils.citeproc() supports a 'quiet' argument
-- (it doesn't yet, but perhaps it will, in which case this
-- will use the appropriate pandoc version check)
local supports_quiet_arg = true

--- Run citeproc on a pandoc document
local function citeproc(doc, quiet)
  -- utils.citeproc() was added in 2.19.1
  if utils.citeproc and supports_quiet_arg then
    -- Built-in Lua function
    return utils.citeproc(doc, quiet)
  else
    -- Use pandoc as a citeproc processor
    local path = PANDOC_STATE.resource_path
    local opts = {'--from=json', '--to=json', '--citeproc',
                  '--resource-path=' .. table.concat(path, ':'),
                  quiet and '--quiet' or nil}
    return run_json_filter(doc, 'pandoc', opts)
  end
end

--- Resolve citations in the document by combining all bibliographies
-- before running citeproc on the full document.
local function resolve_doc_citations (doc)
  -- combine all bibliographies and references
  local meta = doc.meta
  local bibconf = meta.bibliography
  meta.bibliography = pandoc.MetaList { bibconf }
  for name, value in pairs(meta) do
    if name:match('^bibliography_') then
      table.insert(meta.bibliography, value)
    end
  end
  local refconf = meta.references
  meta.references = pandoc.MetaList{}
  if metatype(refconf) == 'table' then
    for topic, refs in pairs(refconf) do
      -- save topic references for meta_for_citeproc()
      topic_refs[topic] = refs
      for _, ref in ipairs(refs) do
        table.insert(meta.references, ref)
      end
    end
  end
  -- add refs div to catch the created bibliography
  table.insert(doc.blocks, refs_div)
  -- resolve all citations
  doc = citeproc(doc)
  -- remove catch-all bibliography and keep it for future use
  refs_div_with_properties = table.remove(doc.blocks)
  -- restore bibliography and references to original values
  doc.meta.bibliography = bibconf
  doc.meta.references = refconf
  return doc
end

--- Explicitly create a new meta object with all fields relevant for citeproc.
local function meta_for_citeproc (bibliography, topic)
  -- We could just indiscriminately copy all meta fields, but let's be
  -- explicit about what's important.
  local fields = {
    'bibliography', 'references', 'csl', 'citation-style',
    'link-citations', 'citation-abbreviations', 'lang',
    'suppress-bibliography', 'reference-section-title',
    'notes-after-punctuation', 'nocite', 'link-bibliography'
  }
  local new_meta = pandoc.Meta{}
  for _, field in ipairs(fields) do
    local value = doc_meta[field]
    -- replace 'references' with the topic references
    if field == 'references' and metatype(value) == 'table' and topic then
      value = topic_refs[topic]
    end
    new_meta[field] = value
  end
  new_meta.bibliography = bibliography
  return new_meta
end

-- list of ref-xxx identifiers that have already been output
local identifiers = List()

-- ignore duplicate references (the first definition will win)
local function ignore_duplicates(blocks)
  local new_blocks = pandoc.Blocks{}
  for _, block in ipairs(blocks) do
    local identifier = block.attr.identifier
    if not identifiers:includes(identifier) then
      local new_block = pandoc.walk_block(block, {Span=_span})
      new_blocks:insert(new_block)
      identifiers:insert(identifier)
    end
  end

  return new_blocks
end

local function remove_duplicates(classes)
  local seen = {}
  return classes:filter(function(x)
      if seen[x] then
        return false
      else
        seen[x] = true
        return true
      end
  end)
end

--- Create a bibliography for a given topic. This acts on all divs whose
-- ID starts with "refs", followed by nothing but underscores and
-- alphanumeric characters.
local function create_topic_bibliography (div)
  local name = div.identifier:match('^refs[-_]?([-_%w]*)$')
  local bibfile = name and doc_meta['bibliography_' .. name]
  if not bibfile then
    return nil
  end
  local tmp_blocks = {pandoc.Para(all_cites), refs_div}
  local tmp_meta = meta_for_citeproc(bibfile, name)
  local tmp_doc = pandoc.Pandoc(tmp_blocks, tmp_meta)
  local res = citeproc(tmp_doc, true)
  -- First block of the result contains the dummy paragraph, second is
  -- the refs Div filled by citeproc.
  div.content = ignore_duplicates(res.blocks[2].content)
  -- Set the classes and attributes as citeproc did it on refs_div
  div.classes = remove_duplicates(refs_div_with_properties.classes)
  div.attributes = refs_div_with_properties.attributes
  return div
end

-- renumber numbered references and their citations
-- (this logic should probably be in a separate filter; it's too
-- dependent on the CSL, although it should do no harm)

-- map from reference id to its new label
local ref_map = List()

-- ref counter
local ref_counter = 1

local function collect_numbered_refs(div)
  if div.attr.classes:includes('csl-entry') then
    local identifier = div.attr.identifier
    local content = div.content
    -- expect single Para with a Span (depending on style) possibly containing
    -- the citation number (only do anything if it does)
    if (#div.content > 0 and #div.content[1].content > 0 and
        div.content[1].content[1].tag == 'Span') then
      local span = div.content[1].content[1]
      local content = span.content
      if #content > 0 then
        local text = content[1].text
        local pre, num, post = content[1].text:match("^(%p*)(%d+)(%p*)$")
        if pre and num and post then
          local ident = identifier:gsub('^ref%-', '')
          local label = string.format('%s%d%s', pre, ref_counter, post)
          content[1] = pandoc.Str(label)
          ref_map[ident] = label
          ref_counter = ref_counter + 1
          return div
        end
      end
    end
  end
end

local function renumber_cites(cite)
  -- only consider cites with single citations
  if #cite.citations == 1 then
    local id = cite.citations[1].id
    local label = ref_map[id]
    -- only change the content if the label is defined
    if label then
      cite.content = label
      return cite
    end
  end
end

return {
  {
    -- Collect all citations and the doc's Meta value for other filters.
    Cite = function (c) all_cites[#all_cites + 1] = c end,
    Meta = function (m) doc_meta = m end,
  },
  { Pandoc = resolve_doc_citations },
  { Div = create_topic_bibliography },

  -- These should probably be handled via a separate filter.
  { Div = collect_numbered_refs },
  { Cite = renumber_cites }
}