Add support for lazy loading (#1)

* Add support for lazy loading

* Newline

* Link to rubygems

* Remove debug logging

CHANGELOG

@@ -0,0 +1,6 @@
+# 0.0.3
+* Added support for lazy data loading via `lazy` attribute.
+* Performance improvement for placeholder calculation
+
+# 0.0.2
+* First working release

README.md

@@ -4,7 +4,7 @@ A plugin for Jekyll to search for all posts and rank them by relevance. Relevanc
 
 ## Installation
 
-Install the plugin via `bundler` in the latest version:
+Install the plugin via `bundler` from [rubygems](https://rubygems.org/gems/jekyll_ranked_search) in the latest version:
 
 ```shell
 bundle add jekyll_ranked_search
@@ -27,10 +27,31 @@ In your template, add the following lines:
 <script type="module" src="/js/search.js"></script>
 
 <!-- Place this line where you want to render the search box -->
-<search-box></search-box>
+<search-box
+  lazy="true"></search-box>
 ```
 
 You only need to add the `<script>` tag once. It is recommended to add it to the header. The search box will fill 100% of the width of its parent container. The `<search-box>` tag is a [WebComponent](-97https://www.webcomponents.org) that uses [Lit](https://lit.dev) and follows W3C standards and are available in all [modern browswers](https://caniuse.com/custom-elementsv1).
 
 ## Configuration
-No configuration is currently possible.
+
+### Search box
+The following settings can be set on the `<search-box>` component on the frontend.
+
+|Parameter|Description                                    |Type     |Default  |Possible Values                             |
+|---------|-----------------------------------------------|---------|---------|--------------------------------------------|
+| `lazy`  | Lazy load results on first focus of search box| Boolean | `false` | `false` ,`true` (see important note below) |
+
+Example:
+
+```html
+<search-box
+  lazy="true"></search-box>
+```
+
+**Important** The presence of a boolean attribute is interpreted as `true`. Therefore, if you wish to set it to false, remove the attribute completely instead of setting it to `false`.
+
+### Jekyll
+The following values can be set in the `_config.yml` file in the Jekyll folder.
+
+*Currently none*

lib/search.js

@@ -4,16 +4,38 @@ import 'https://cdn.jsdelivr.net/npm/@github/relative-time-element';
 
 class SearchBox extends LitElement {
   static properties = {
-    _data: {state: true, type: Array},
+    _isLoading: {state: true, type: Boolean},
+    _data: {state: false, type: Array},
     _results : {state: true, type: Array},
     _open: {state: true, type: Boolean},
+    _placeholder: {state: true, type: String},
+
+    // Lazy loading
+    lazy: {type: Boolean, attribute: true},
   };
 
+  /**
+   * Constructor. Sets up default values.
+   */
   constructor() {
     super();
+
+    // No data initially loaded
     this._data = [];
+
+    // Results are initially empty
     this._results = [];
+
+    // Start in closed state, show no results
     this._open = false;
+
+    // Default to not loading
+    this._isLoading = false;
+
+    // Disable lazy loading by default
+    this.lazy = false;
+
+    this._placeholder = "Search...";
   }
 
   static styles = css`
@@ -77,16 +99,17 @@ class SearchBox extends LitElement {
 
   connectedCallback() {
     super.connectedCallback();
-    this.loadData();
+
+    // Load data if lazy loading is disabled
+    if (!this.lazy) {
+      this.loadData();
+    }
 
     document.addEventListener('click', (event) => {
       if (!event.composedPath().includes(this) && this._open) {
           this.toggle();
       }
-  });
-
-    // Register arrow keys
-
+    });
   }
 
   toggle() {
@@ -104,12 +127,20 @@ class SearchBox extends LitElement {
   }
 
   async loadData() {
+    // Set state during loading
+    this._isLoading = true;
+    this.updatePlaceholder();
+
     const response = await fetch("/search.json");
     const jsonData = await response.json();
     jsonData.word2doc = new Map(Object.entries(jsonData.word2doc));
     jsonData.bow = new Map(Object.entries(jsonData.bow));
     jsonData.tfidf = new Map(Object.entries(jsonData.tfidf));
     this._data = jsonData;
+
+    // Cleanup state
+    this._isLoading = false;
+    this.updatePlaceholder();
   }
 
   disconnectedCallback() {
@@ -158,7 +189,6 @@ class SearchBox extends LitElement {
     for (const tokenId of tokenIds.slice(1)) {
       // Find document candidates
       const docCandidates = new Set(this._data.word2doc.get(tokenId.toString()));
-      // console.log("intersection", docCandidates, docs);
       docs = new Set([...docs].filter((x) => docCandidates.has(x)));
     }
 
@@ -182,21 +212,33 @@ class SearchBox extends LitElement {
     this._open = true;
   }
 
-  placeholder() {
+  updatePlaceholder() {
+    if (this._isLoading) {
+      this._placeholder = "Loading...";
+      return;
+    }
     if (this._data && this._data.docs && this._data.docs.length > 0) {
       let plural = "";
       if (this._data.docs.length !== 1) {
         plural = "s";
       }
-      return "Search in " + this._data.docs.length + ` post${plural}...`;
-    } else {
-      return "Loading...";
+      this._placeholder = "Search in " + this._data.docs.length + ` post${plural}...`;
+      return;
+    }
+  }
+
+  /**
+   * Event triggered on search box focus.
+   */
+  focus(_) {
+    if (this.lazy && this._data.length === 0 && !this._isLoading) {
+      this.loadData();
     }
   }
 
   render() {
     return html`<div>
-      <input id="q" type="text" placeholder="${this.placeholder()}" @keyup="${this.search}" @click=${this.openIfResults}>
+      <input id="q" type="text" placeholder="${this._placeholder}" @keyup="${this.search}" @click=${this.openIfResults} @focus=${this.focus}>
       ${this._open ? html`
         <div id="results">
           ${this._results.map((result) => html`