docs/_includes/sidenav.html

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{%- comment -%}
==============================================================================
Extract the active nav IDs.
==============================================================================
{%- endcomment -%}

{%- assign active_nav_ids = site.array -%}
{%- assign parent_id = page.nav-parent_id -%}

{%- for i in (1..10) -%}
  {%- if parent_id -%}
    {%- assign active_nav_ids = active_nav_ids | push: parent_id -%}
    {%- assign current = (site.pages_by_language[page.language] | where: "nav-id" , parent_id | sort: "nav-pos") -%}
    {%- if current.size > 0 -%}
      {%- assign parent_id = current[0].nav-parent_id -%}
    {%- else -%}
      {%- break -%}
    {%- endif -%}
  {%- else -%}
    {%- break -%}
  {%- endif -%}
{%- endfor -%}

{%- if page.language == "en" -%}
  {%- capture baseurl_i18n -%}{{ site.baseurl }}{%- endcapture -%}
{%- else if page.language == "zh" -%}
  {%- capture baseurl_i18n -%}{{ site.baseurl }}/{{ page.language }}{%- endcapture -%}
{%- endif -%}

{%- comment -%}
==============================================================================
Build the nested list from nav-id and nav-parent_id relations.
==============================================================================
This builds a nested list from all pages. The fields used to determine the
structure are:

- 'nav-id' => ID of this page. Other pages can use this ID as their
  parent ID.
- 'nav-parent_id' => ID of the parent. This page will be listed under
  the page with id 'nav-parent_id'.

Level 0 is made up of all pages, which have nav-parent_id set to 'root'.

The 'title' of the page is used as the default link text. You can
override this via 'nav-title'. The relative position per navigational
level is determined by 'nav-pos'.
{%- endcomment -%}

{%- assign elementsPosStack = site.array -%}
{%- assign posStack = site.array -%}

{%- assign elements = site.array -%}
{%- assign all_pages_by_nav_parent = (site.pages_by_language[page.language] | where_exp: "item", "item.nav-parent_id != nil" | group_by: "nav-parent_id") -%}
{%- assign children = (all_pages_by_nav_parent | where: "name" , "root") -%}
{%- assign children = (children[0].items | sort: "nav-pos") -%}
{%- if children.size > 0 -%}
  {%- assign elements = elements | push: children -%}
{%- endif -%}

{%- assign elementsPos = 0 -%}
{%- assign pos = 0 -%}

<div class="sidenav-logo">
  <p><a href="{{ baseurl_i18n }}/"><img class="bottom" alt="Apache Flink" src="{{ site.baseurl }}/page/img/navbar-brand-logo.png"></a> v{{ site.version_title }}</p>
</div>
<ul id="sidenav">
{%- for i in (1..10000) -%}
  {%- if pos >= elements[elementsPos].size -%}
    {%- if elementsPos == 0 -%}
      {%- break -%}
    {%- else -%}
      {%- assign elementsPos = elementsPosStack | last -%}
      {%- assign pos = posStack | last %}
</ul></div></li>
      {%- assign elementsPosStack = elementsPosStack | pop -%}
      {%- assign posStack = posStack | pop -%}
    {%- endif -%}
  {%- else -%}
    {%- assign this = elements[elementsPos][pos] -%}

    {%- if this.url == page.url -%}
      {%- assign active = true -%}
    {%- elsif this.nav-id and active_nav_ids contains this.nav-id -%}
      {%- assign active = true -%}
    {%- elsif this.always-expand -%}
      {%- assign active = true -%}
    {%- else -%}
      {%- assign active = false -%}
    {%- endif -%}

    {%- capture title -%}{%- if this.nav-title -%}{{ this.nav-title }}{%- else -%}{{ this.title }}{%- endif -%}{%- endcapture -%}
    {%- capture target -%}"{{ site.baseurl }}{{ this.url }}"{%- if active %} class="active"{%- endif -%}{%- endcapture -%}
    {%- capture overview_target -%}"{{ site.baseurl }}{{ this.url }}"{%- if this.url == page.url -%} class="active"{%- endif -%}{%- endcapture -%}

    {% if this.section-break %}<hr class="section-break"></hr>{% endif -%}

    {%- assign pos = pos | plus: 1 -%}
    {%- if this.nav-id -%}
      {%- assign children = (all_pages_by_nav_parent | where: "name" , this.nav-id) -%}
      {%- if children.size > 0 -%}
        {%- assign children = (children[0].items | sort: "nav-pos") -%}
        {%- capture collapse_target -%}"#collapse-{{ i }}" data-toggle="collapse"{%- if active -%} class="active"{%- endif -%}{%- endcapture -%}
        {%- capture expand -%}<i class="fa fa-caret-down pull-right" aria-hidden="true" style="padding-top: 4px"></i>{%- endcapture %}
<li><a href={{ collapse_target }}>{{ title }}{{ expand }}</a><div class="collapse{% if active %} in{% endif %}" id="collapse-{{ i }}"><ul>
        {%- if this.nav-show_overview %}
<li><a href={{ overview_target }}>
            {%- if page.is_default_language %}Overview{% else %}概览{% endif %}</a></li>
        {%- endif -%}
        {%- assign elements = elements | push: children -%}
        {%- assign elementsPosStack = elementsPosStack | push: elementsPos -%}
        {%- assign posStack = posStack | push: pos -%}

        {%- assign elementsPos = elements.size | minus: 1 -%}
        {%- assign pos = 0 -%}
      {%- else %}
<li><a href={{ target }}>{{ title }}</a></li>
      {%- endif -%}
    {%- else %}
<li><a href={{ target }}>{{ title }}</a></li>
    {%- endif -%}
  {%- endif -%}
{%- endfor %}
  <li class="divider"></li>
  <li><a href="{{ site.javadocs_baseurl }}/api/java"><i class="fa fa-external-link title" aria-hidden="true"></i> Javadocs</a></li>
  <li><a href="http://flink.apache.org"><i class="fa fa-external-link title" aria-hidden="true"></i> Project Page</a></li>
</ul>

<div class="sidenav-search-box">
  <form class="navbar-form" role="search" action="{{site.baseurl}}/search-results.html">
    <div class="form-group">
      <input type="text" class="form-control" size="16px" name="q" placeholder="Search">
    </div>
    <button type="submit" class="btn btn-default">Go</button>
  </form>
</div>

<div class="sidenav-versions">
  <div class="dropdown">
    <button class="btn btn-default dropdown-toggle" type="button" data-toggle="dropdown">
      {%- if page.is_default_language -%}
        Pick Docs Version
      {%- else -%}
        选择文档版本
      {%- endif -%}
    <span class="caret"></span></button>
    <ul class="dropdown-menu">
      {%- for d in site.previous_docs %}
      <li><a href="{{ d[1] }}">v{{ d[0] }}</a></li>
      {%- endfor %}
    </ul>
  </div>
</div>

<!--
<div class="sidenav-languages">
  {%- if page.is_default_language -%}
    <a href="{{ site.baseurl }}/zh{{ page.url }}">
      <button type="submit" class="btn btn-default">中文版</button>
    </a>
  {%- else -%}
    <a href="{{ site.baseurl }}{{ page.url | remove_first: 'zh/' }}">
      <button type="submit" class="btn btn-default">English</button>
    </a>
  {%- endif %}
</div>
-->