From 2622c5b501d9beca3f2b02b80987759833cb4410 Mon Sep 17 00:00:00 2001
From: Paul Traylor <paul.traylor@linecorp.com>
Date: Wed, 26 Feb 2020 10:37:09 +0900
Subject: [PATCH] [INTERNAL] Helper to rewrite query string for paginated lists

---
 promgen/templates/promgen/pagination.html     |  7 ++++---
 .../templates/promgen/pagination_short.html   |  4 ++--
 promgen/templatetags/promgen.py               | 21 +++++++++++++++++++
 3 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/promgen/templates/promgen/pagination.html b/promgen/templates/promgen/pagination.html
index 1f6fb1d69..9f9c39ec5 100644
--- a/promgen/templates/promgen/pagination.html
+++ b/promgen/templates/promgen/pagination.html
@@ -1,8 +1,9 @@
+{% load promgen %}
 <nav aria-label="Page navigation">
     {% if page_obj.has_other_pages %}
     <ul class="pagination">
         {% if page_obj.has_previous %}
-        <li><a href="?page={{ page_obj.previous_page_number }}">&laquo;</a></li>
+        <li><a href="?{% qs_replace 'page' page_obj.previous_page_number %}">&laquo;</a></li>
         {% else %}
         <li class="disabled"><span>&laquo;</span></li>
         {% endif %}
@@ -10,11 +11,11 @@
         {% if page_obj.number == i %}
         <li class="active"><span>{{ i }} <span class="sr-only">(current)</span></span></li>
         {% else %}
-        <li><a href="?page={{ i }}">{{ i }}</a></li>
+        <li><a href="?{% qs_replace 'page' i %}">{{ i }}</a></li>
         {% endif %}
         {% endfor %}
         {% if page_obj.has_next %}
-        <li><a href="?page={{ page_obj.next_page_number }}">&raquo;</a></li>
+        <li><a href="?{% qs_replace 'page' page_obj.next_page_number %}">&raquo;</a></li>
         {% else %}
         <li class="disabled"><span>&raquo;</span></li>
         {% endif %}
diff --git a/promgen/templates/promgen/pagination_short.html b/promgen/templates/promgen/pagination_short.html
index f0ca90035..0157b909d 100644
--- a/promgen/templates/promgen/pagination_short.html
+++ b/promgen/templates/promgen/pagination_short.html
@@ -3,7 +3,7 @@
     {% if page_obj.has_other_pages %}
     <ul class="pagination">
         {% if page_obj.has_previous %}
-        <li><a href="?page={{ page_obj.previous_page_number }}">&laquo;</a></li>
+        <li><a href="?{% qs_replace 'page' page_obj.previous_page_number %}">&laquo;</a></li>
         {% else %}
         <li class="disabled"><span>&laquo;</span></li>
         {% endif %}
@@ -13,7 +13,7 @@
         </li>
 
         {% if page_obj.has_next %}
-        <li><a href="?page={{ page_obj.next_page_number }}">&raquo;</a></li>
+        <li><a href="?{% qs_replace 'page' page_obj.next_page_number %}">&raquo;</a></li>
         {% else %}
         <li class="disabled"><span>&raquo;</span></li>
         {% endif %}
diff --git a/promgen/templatetags/promgen.py b/promgen/templatetags/promgen.py
index e2bb92ea6..843763ffc 100644
--- a/promgen/templatetags/promgen.py
+++ b/promgen/templatetags/promgen.py
@@ -201,3 +201,24 @@ def to_tag():
         yield "</ol>"
 
     return mark_safe("".join(to_tag()))
+
+
+@register.simple_tag(takes_context=True)
+def qs_replace(context, k, v):
+    """
+    Query string handler for paginators
+
+    Assuming we have a query string like ?page=1&search=foo, there are several cases
+    in which we want to replace only the page key, while leaving the rest alone.
+    This tag allows us to replace individual values (like the current page) while
+    carrying over other values (like a search string)
+
+    Example:
+    {% qs_replace 'page' page_obj.next_page_number %}
+    """
+    dict_ = context["request"].GET.copy()
+    if v:
+        dict_[k] = v
+    else:
+        dict_.pop(k, None)
+    return dict_.urlencode()