From 9f9a5d6aa541437a2459de1bf12f7bd9e8ef37ab Mon Sep 17 00:00:00 2001
From: tdro <tdro@noreply.example.com>
Date: Fri, 2 Sep 2022 04:15:06 -0400
Subject: static/js/pager: Add fragment intersection observer

To release URL fragments
---
 assets/js/index.js | 35 +++++++++++++++++++++++++++++------
 static/js/pager.ts | 34 ++++++++++++++++++++++++++++++----
 2 files changed, 59 insertions(+), 10 deletions(-)

diff --git a/assets/js/index.js b/assets/js/index.js
index a0c608f..b4f0bcb 100644
--- a/assets/js/index.js
+++ b/assets/js/index.js
@@ -12,18 +12,20 @@
     const settings1 = {
         pager: {}
     };
-    const url1 = self.location.href.split("#")[0];
+    const url1 = self.location.href.split("#")[0].split("?")[0];
     const scrollRestore = (settings, url)=>{
         if (history.scrollRestoration) history.scrollRestoration = "manual";
         if (localStorage["settings"]) {
             settings = JSON.parse(localStorage["settings"]);
         }
-        if (self.location.hash.length > 0) {
+        const fragment = document.getElementById(location.hash.slice(1));
+        const fragmentInURL = self.location.hash.length > 0;
+        if (fragmentInURL && document.body.contains(fragment)) {
             settings["pager"][url] = self.pageYOffset;
             localStorage["settings"] = JSON.stringify(settings);
-            document.getElementById(location.hash.slice(1)).scrollIntoView();
+            fragment.scrollIntoView();
             self.addEventListener("load", function() {
-                document.getElementById(location.hash.slice(1)).scrollIntoView();
+                fragment.scrollIntoView();
             });
             return;
         }
@@ -50,8 +52,29 @@
             history.go(-1);
         }
     };
+    const fragmentClear = (entries)=>{
+        for(let entry = 0; entry < entries.length; entry++){
+            if (self.location.hash) {
+                self.history.pushState(null, "", url1);
+            }
+        }
+    };
+    const fragmentRelease = (fragmentCallback)=>{
+        try {
+            const fragmentObserver = new IntersectionObserver(fragmentCallback, {
+                threshold: 1.0
+            });
+            const fragments = document.querySelectorAll("[id]");
+            for(let fragment = 0; fragment < fragments.length; fragment++){
+                fragmentObserver.observe(fragments[fragment]);
+            }
+        } catch (error) {
+            console.log("The intersection observer is not supported", error);
+        }
+    };
     self.addEventListener("DOMContentLoaded", function() {
         scrollRestore(settings1, url1);
+        fragmentRelease(fragmentClear);
         self.addEventListener("click", function(event) {
             const up = document.getElementById("top");
             const back = document.getElementById("back");
@@ -498,8 +521,8 @@
                 if (days <= 60) {
                     return element.textContent = relative.format(-1 * days, "day");
                 }
-            } catch (err) {
-                console.error("Error: Unable to resolve relative time format!", err);
+            } catch (error) {
+                console.error("Error: Unable to resolve relative time format!", error);
             }
         });
     };
diff --git a/static/js/pager.ts b/static/js/pager.ts
index 0de2ec1..68708cc 100644
--- a/static/js/pager.ts
+++ b/static/js/pager.ts
@@ -9,19 +9,21 @@
 
   const settings = { pager: {} };
 
-  const url = self.location.href.split("#")[0];
+  const url = self.location.href.split("#")[0].split("?")[0];
 
   const scrollRestore = (settings, url) => {
     if (history.scrollRestoration) history.scrollRestoration = "manual";
     if (localStorage["settings"]) {
       settings = JSON.parse(localStorage["settings"]);
     }
-    if (self.location.hash.length > 0) {
+    const fragment = document.getElementById(location.hash.slice(1));
+    const fragmentInURL = self.location.hash.length > 0;
+    if (fragmentInURL && document.body.contains(fragment)) {
       settings["pager"][url] = self.pageYOffset;
       localStorage["settings"] = JSON.stringify(settings);
-      document.getElementById(location.hash.slice(1)).scrollIntoView();
+      fragment.scrollIntoView();
       self.addEventListener("load", function () {
-        document.getElementById(location.hash.slice(1)).scrollIntoView();
+        fragment.scrollIntoView();
       });
       return;
     }
@@ -51,8 +53,32 @@
     }
   };
 
+  const fragmentClear = (entries) => {
+    for (let entry = 0; entry < entries.length; entry++) {
+      if (self.location.hash) {
+        self.history.pushState(null, "", url);
+      }
+    }
+  };
+
+  const fragmentRelease = (fragmentCallback) => {
+    try {
+      const fragmentObserver = new IntersectionObserver(fragmentCallback, {
+        threshold: 1.0,
+      });
+      const fragments = document.querySelectorAll("[id]");
+
+      for (let fragment = 0; fragment < fragments.length; fragment++) {
+        fragmentObserver.observe(fragments[fragment]);
+      }
+    } catch (error) {
+      console.log("The intersection observer is not supported", error);
+    }
+  };
+
   self.addEventListener("DOMContentLoaded", function () {
     scrollRestore(settings, url);
+    fragmentRelease(fragmentClear);
     self.addEventListener("click", function (event) {
       const up = document.getElementById("top");
       const back = document.getElementById("back");
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