Neopyter keymap

-- <leader>jn – .ipynb → .ju.py via jupytext, then turn lone "#" lines into blank lines
map("n", "<leader>jn", function()
  vim.cmd("silent update")

  local infile = vim.fn.expand("%:p")
  if vim.fn.fnamemodify(infile, ":e") ~= "ipynb" then
    vim.notify("Current buffer is not an .ipynb", vim.log.levels.WARN)
    return
  end

  local outpath = vim.fn.expand("%:r") .. ".ju.py"

  local function run(args, on_ok, on_err)
    if vim.system then
      vim.system(args, { text = true }, function(res)
        vim.schedule(function()
          if res.code == 0 then
            on_ok()
          else
            on_err(res.stderr or "")
          end
        end)
      end)
    else
      vim.fn.jobstart(args, {
        stdout_buffered = true,
        stderr_buffered = true,
        on_exit = function(_, code)
          vim.schedule(function()
            if code == 0 then
              on_ok()
            else
              on_err("")
            end
          end)
        end,
      })
    end
  end

  local function open_and_strip()
    -- Create/load the buffer for the new file WITHOUT depending on the current window
    local buf = vim.fn.bufadd(outpath)
    vim.fn.bufload(buf)

    -- Make sure it's editable (preview/floating windows can set nomodifiable)
    vim.bo[buf].readonly = false
    vim.bo[buf].modifiable = true

    -- Do the substitution INSIDE that buffer's context
    vim.api.nvim_buf_call(buf, function()
      -- Turn lines that are just "#" (with optional spaces) into blank lines.
      -- This keeps the newline; it does NOT delete the line.
      vim.cmd([[silent keeppatterns %s/^\s*#\s*$//e]])
      -- Optionally save the result:
      vim.cmd("silent write")
    end)

    -- Show the converted file
    vim.api.nvim_set_current_buf(buf)
    vim.notify("Converted → " .. outpath .. " and stripped lone '#' lines", vim.log.levels.INFO)
  end

  if vim.fn.executable("jupytext") == 1 then
    run({ "jupytext", "--to", "py:percent", "--output", outpath, infile }, open_and_strip, function(err)
      vim.notify("jupytext failed: " .. err, vim.log.levels.ERROR)
    end)
  elseif vim.fn.executable("jupyter") == 1 then
    -- Fallback: plain script via nbconvert if jupytext isn't available
    run({ "jupyter", "nbconvert", "--to", "script", "--output", outpath, infile }, open_and_strip, function(err)
      vim.notify("nbconvert failed: " .. err, vim.log.levels.ERROR)
    end)
  else
    vim.notify("Neither `jupytext` nor `jupyter nbconvert` found in PATH", vim.log.levels.ERROR)
  end
end, { desc = "Convert .ipynb → .ju.py and blank-out lone '#' lines" })