Use caching for postlist (#5)

* caching

* Update cachingUtils.php

* .

.gitignore

@@ -5,3 +5,5 @@ html
 vendor
 assets/styles/*.css
 assets/styles/*.css.map
+tmp/*.json
+tmp/*.php

README.md

@@ -107,13 +107,8 @@ Then create a pull request from `updates-from-upstream` branch to `main` branch
 
 ## Future Plans
 
-### Caching Markdown files for performance in local env
-
-Caching for page and post Markdowns in local environment will be added, so that the local dev env is always fast to 
-navigate between urls, regardless of how many markdowns are there.
-
 ### Pagination for posts
 
 I am a fan of continuous scrolling and not numbered pages. We can implement continuous scrolling on the homepage but 
 I can't imagine if it can be helpful for sites with less than 100 posts. Even after 100 posts, it should not 
-be a big problem for the page to be rendered. I am open for suggestions though.  
+be a big problem for the page to be rendered. I am open for suggestions though.  

index.php

@@ -7,7 +7,7 @@
 
 require_once 'layout/header.php';
 
-$posts = get_all_posts();
+$posts = updateAndGetCachedPostList();
 
 echo "<div id='posts'>";
 foreach ($posts as $post) {

post.php

@@ -14,7 +14,7 @@
 
 // Iterate through all posts and find the one with the same slug
 // Not the most performant but once deployed they will all be static websites.
-$post = current(array_filter(get_all_posts(), function ($post) {
+$post = current(array_filter(updateAndGetCachedPostList(), function ($post) {
     return $post->slug == $_GET['slug'];
 }));
 
@@ -23,7 +23,7 @@
     exit_with_not_found();
 }
 
-$tpl = get_markdown($post->filename);
+$tpl = get_markdown('posts/' . $post->filename);
 
 $page_meta->title = $tpl->meta->title ?? null;
 $page_meta->type = "article";

system/Types.php

@@ -5,6 +5,9 @@ class Post {
     public string $desc;
     public string $slug;
     public string $filename;
+
+    // When was the file modified last
+    public int $lastModified;
 }
 
 class PageMeta

system/bootstrap.php

@@ -5,6 +5,7 @@
 
 require_once(__DIR__ . "/../vendor/autoload.php");
 require_once(__DIR__ . '/Types.php');
+require_once(__DIR__ . '/cachingUtils.php');
 
 $config = json_decode(file_get_contents(__DIR__ . "/../config.json"));
 
@@ -33,31 +34,6 @@ function get_markdown($path): ConvertedMarkdown
     return convert_markdown($path);
 }
 
-/**
- * Generate and return all posts as an array
- * @return Post[]
- * @throws CommonMarkException
- */
-function get_all_posts(): array
-{
-    $posts = [];
-    $files = glob('posts/*.md');
-    rsort($files);
-    foreach ($files as $key => $post_file_path) {
-        $tpl = get_markdown($post_file_path);
-
-        $postObj = new Post();
-        $postObj->title = $tpl->meta->title;
-        $postObj->desc = $tpl->meta->desc;
-        $postObj->slug = $tpl->meta->slug;
-        $postObj->filename = $post_file_path;
-
-        $posts[] = $postObj;
-    }
-
-    return $posts;
-}
-
 /**
  * Show not found page
  * @return void

system/cachingUtils.php

@@ -0,0 +1,88 @@
+<?php
+function findMostRecentlyUpdatedFile($dir) {
+    $latestFile = "";
+    $latestTime = 0;
+
+    foreach (scandir($dir) as $file) {
+        // Avoid directories and only check files
+        if (is_file($dir . '/' . $file)) {
+            $fileTime = filemtime($dir . '/' . $file);
+            if ($fileTime > $latestTime) {
+                $latestTime = $fileTime;
+                $latestFile = $file;
+            }
+        }
+    }
+
+    return $latestTime;
+}
+
+/*
+ * TODO: This function needs refactoring, should be a class, and needs tests.
+ * @return Post[]
+ */
+function updateAndGetCachedPostList(): array
+{
+    $cachePath = __DIR__ . '/../tmp/posts.json';
+    $postsDir = __DIR__ . '/../posts/';
+
+    /* @var Post[] $cachedPosts */
+    $cachedPosts = [];
+    if (file_exists($cachePath)) {
+        $cachedPostsJson = file_get_contents($cachePath);
+        $cachedPosts = json_decode($cachedPostsJson);
+    }
+
+    $cacheModified = false; // Flag to track modifications
+
+    // Iterate through each post in the directory
+    $postFiles = scandir($postsDir);
+    foreach ($postFiles as $postFile) {
+        if (is_file($postsDir . $postFile)) {
+            $lastModified = filemtime($postsDir . $postFile);
+
+            // Check if post is in cache and if its lastModified is outdated
+            $shouldUpdateCache = true;
+            foreach ($cachedPosts as &$cachedPost) {
+                if ($cachedPost->filename === $postFile && $cachedPost->lastModified >= $lastModified) {
+                    $shouldUpdateCache = false;
+                    break;
+                }
+            }
+
+            // If post is outdated or not in cache, update its data
+            if ($shouldUpdateCache) {
+                $tpl = get_markdown($postsDir . $postFile);
+
+                $postObj = new stdClass();
+                $postObj->title = $tpl->meta->title;
+                $postObj->desc = $tpl->meta->desc;
+                $postObj->slug = $tpl->meta->slug;
+                $postObj->filename = $postFile;
+                $postObj->lastModified = $lastModified;
+
+                // Replace or append the post in the cache array
+                $found = false;
+                foreach ($cachedPosts as &$cachedPost) {
+                    if ($cachedPost->filename === $postFile) {
+                        $cachedPost = $postObj;
+                        $found = true;
+                        break;
+                    }
+                }
+                if (!$found) {
+                    $cachedPosts[] = $postObj;
+                }
+
+                $cacheModified = true; // Mark that the cache has been modified
+            }
+        }
+    }
+
+    // Only save the updated cache if it was modified
+    if ($cacheModified) {
+        file_put_contents($cachePath, json_encode($cachedPosts, JSON_PRETTY_PRINT));
+    }
+
+    return $cachedPosts;
+}