Pandoc: Separate table of contents for each section - pandoc

Question

I am converting Markdown to HTML with Pandoc. With --toc, Pandoc generates a table of contents and inserts it under the first H1 heading (of which there is only one).
I would like it to have a separate, additional table of contents for each subheading. More specifically, I would like a small local table of contents under each H3.
Can Pandoc do that, and if yes, how?

Answer 1

I received an answer on the pandoc-discuss mailing list in the form of a Lua filter.
Quoting from the author of the solution:
Warning: Assumes that all chapters are heading level 2 — change the chapter_level and toc_level variables to match!
Warning: Assumes that each section/chapter has a unique identifier!
local chapter_level = 2
local toc_level = 3
local headings = {}
local current_chapter = nil
local function collect_headings (head)
if head.level == chapter_level then
local id = head.identifier
current_chapter = {
chapter = id,
toc = {},
}
headings[id] = current_chapter
elseif head.level == toc_level then
if current_chapter then
local toc = current_chapter.toc
toc[#toc+1] = head
end
end
return nil
end
local function build_toc (heads)
local toc = {}
for _,head in ipairs(heads) do
local entry = {
pandoc.Plain{
pandoc.Link(
head.content:clone(), -- text
'#' .. head.identifier, -- target
"", -- empty title
pandoc.Attr(
"", -- empty identifier
{'local-toc-link'} -- class
)
)
}
}
toc[#toc+1] = entry
end
return pandoc.Div(
{ pandoc.BulletList(toc) },
pandoc.Attr( "", {'local-toc'} )
)
end
local function insert_toc (head)
if head.level == chapter_level then
local id = head.identifier
if headings[id] then
local toc = build_toc(
headings[id].toc
)
return {head,toc}
end
end
return nil
end
return {
{ Header = collect_headings },
{ Header = insert_toc },
}