-- Copyright (c) 2026 Marc Wäckerlin. SPDX-License-Identifier: MIT
-- A folded block does not belong in a document nobody can click.
--
-- `<details>` with its `<summary>` is a fold of the browser: the reader opens
-- it when he wants it and sees a single line meanwhile. On paper there is
-- nothing to open, so the fold arrives unfolded — measured in one report, the
-- diagram sources behind it filled whole pages under the pictures they draw.
-- The block goes out with everything in it, the summary line included.

local OPEN = '<details'
local CLOSE = '</details>'

local function marker(block)
  return block.t == 'RawBlock' and block.format == 'html' and block.text or ''
end

function Blocks(blocks)
  local kept, depth = {}, 0
  for _, block in ipairs(blocks) do
    local raw = marker(block)
    local opens = raw:find(OPEN, 1, true)
    local closes = raw:find(CLOSE, 1, true)
    if opens then
      depth = depth + (closes and 0 or 1)
    elseif closes then
      depth = math.max(0, depth - 1)
    elseif depth == 0 then
      kept[#kept + 1] = block
    end
  end
  return kept
end