add extensions

_extensions/pandoc-ext/abstract-section/_extension.yaml

@@ -0,0 +1,6 @@
+name: abstract-section
+author: Albert Krewinkel
+version: 1.0.0
+contributes:
+  filters:
+    - abstract-section.lua

_extensions/pandoc-ext/abstract-section/abstract-section.lua

@@ -0,0 +1,59 @@
+--[[
+abstract-to-meta – move an "abstract" section into document metadata
+
+Copyright: © 2017–2021 Albert Krewinkel
+License:   MIT – see LICENSE file for details
+]]
+local abstract = {}
+
+--- Extract abstract from a list of blocks.
+function abstract_from_blocklist (blocks)
+  local body_blocks = {}
+  local looking_at_abstract = false
+
+  for _, block in ipairs(blocks) do
+    if block.t == 'Header' and block.level == 1 then
+      if block.identifier == 'abstract' then
+        looking_at_abstract = true
+      else
+        looking_at_abstract = false
+        body_blocks[#body_blocks + 1] = block
+      end
+    elseif looking_at_abstract then
+      if block.t == 'HorizontalRule' then
+        looking_at_abstract = false
+      else
+        abstract[#abstract + 1] = block
+      end
+    else
+      body_blocks[#body_blocks + 1] = block
+    end
+  end
+
+  return body_blocks
+end
+
+if PANDOC_VERSION >= {2,9,2} then
+  -- Check all block lists with pandoc 2.9.2 or later
+  return {{
+      Blocks = abstract_from_blocklist,
+      Meta = function (meta)
+        if not meta.abstract and #abstract > 0 then
+          meta.abstract = pandoc.MetaBlocks(abstract)
+        end
+        return meta
+      end
+  }}
+else
+  -- otherwise, just check the top-level block-list
+  return {{
+      Pandoc = function (doc)
+        local meta = doc.meta
+        local other_blocks = abstract_from_blocklist(doc.blocks)
+        if not meta.abstract and #abstract > 0 then
+          meta.abstract = pandoc.MetaBlocks(abstract)
+        end
+        return pandoc.Pandoc(other_blocks, meta)
+      end,
+  }}
+end