{% macro tnaPageSiteTitleDisplay(pageTitle, siteTitle, maxTitleLength, separator, ellipsis) %}
  {#-
      Truncate any pageTitle that would cause the length of the <title> to exceed 70 characters
      See https://html-validate.org/rules/long-title.html
  -#}

  {# 1. Define inputs and default values #}
  {%- set pageTitle = pageTitle or '' -%}
  {%- set siteTitle = siteTitle or 'The National Archives' -%}
  {%- set separator = separator or ' - ' -%}
  {%- set ellipsis = ellipsis or '…' -%}
  {%- set maxLength = maxTitleLength or 70 -%}

  {# 2. Reusable macro for smart truncation #}
  {%- macro smartTruncate(str, budget, ellipsis) -%}
    {%- if (str | length) <= budget -%}
      {{- str -}}
    {%- else -%}
      {%- set ellipsisLength = ellipsis | length -%}
      {%- set targetLength = budget - ellipsisLength -%}
      {%- if targetLength < 0 -%}{%- set targetLength = 0 -%}{%- endif -%}
      {%- set sliced = str[:targetLength] -%}
      {%- set lastSpace = sliced.rfind(' ') -%}
      {# Only clip to last space if it leaves enough room for meaningful word text #}
      {%- if lastSpace > (ellipsisLength + 1) -%}
        {{- sliced[:lastSpace] | trim }}{{ ellipsis }}
      {%- else -%}
        {{- sliced | trim }}{{ ellipsis }}
      {%- endif -%}
    {%- endif -%}
  {%- endmacro -%}

  {# 3. Check if the ENTIRE combined title fits without any truncation #}
  {%- set fullCombined = (pageTitle + separator + siteTitle) if pageTitle else siteTitle -%}
  {%- if (fullCombined | length) <= maxLength -%}
    {# Everything fits completely—output raw with zero truncation! #}
    {{- fullCombined -}}
  {%- else -%}
    {# 4. If it overflows, handle based on whether pageTitle exists #}
    {%- if pageTitle -%}
      {# Both exist: dynamically allocate space (fair share with redistribution) #}
      {%- set separatorLen = separator | length -%}
      {%- set availableLength = maxLength - separatorLen -%}
      {%- set halfBudget = (availableLength / 2) | int -%}

      {# If siteTitle is short, let pageTitle use its leftover budget #}
      {%- set siteBudget = halfBudget -%}
      {%- if (siteTitle | length) < halfBudget -%}
        {%- set siteBudget = siteTitle | length -%}
      {%- endif -%}

      {%- set remainingForPage = availableLength - siteBudget -%}

      {%- set truncatedSiteTitle = smartTruncate(siteTitle, siteBudget, ellipsis) -%}
      {%- set truncatedPageTitle = smartTruncate(pageTitle, remainingForPage, ellipsis) -%}

      {{- truncatedPageTitle -}}{{ separator }}{{- truncatedSiteTitle -}}
    {%- else -%}
      {# Only siteTitle exists: it gets the full maxLength budget #}
      {{- smartTruncate(siteTitle, maxLength, ellipsis) -}}
    {%- endif -%}
  {%- endif -%}
{% endmacro %}