site: implement search functionality

public/js/app.js

@@ -0,0 +1,97 @@
+function getCurrentWord(s, cursor) {
+  return s.substring(s.lastIndexOf(' ', cursor - 1) + 1, cursor);
+}
+
+function mySplice(s, idx, del, n) {
+  return s.substring(0, idx) + n + s.substring(idx + del);
+}
+
+function suggestionPosition(el) {
+  // el.parentNode is ul#tags-suggestion, which include a template. That's why
+  // a -1 is needed here.
+  const idx = [...el.parentNode.children].indexOf(el);
+  return idx <= 0 ? null : idx - 1;
+}
+
+function currentSuggestionElement(idx) {
+  if (idx === null)
+    return null;
+  return document.querySelector("#tags-suggestions").children[idx + 1];
+}
+
+document.addEventListener('alpine:init', () => {
+  Alpine.data('tagsSuggestions', () => ({
+    suggestions: [],
+    currentSuggestion: null,
+    inputCursor: 0,
+    query: '',
+
+    reset() {
+      this.suggestions = [];
+      this.currentSuggestion = null;
+      this.inputCursor = 0;
+      this.query = '';
+    },
+
+    async fetchSuggestions(evt) {
+      this.inputCursor = evt.target.selectionStart;
+      this.query = getCurrentWord(evt.target.value, this.inputCursor);
+      if (!this.query) {
+        this.reset();
+        return;
+      }
+
+      const params = new URLSearchParams({q: this.query});
+      const response = await fetch(`${endpoints.search}?${params}`);
+
+      if (!response.ok) {
+        this.reset();
+        return;
+      }
+
+      this.suggestions = await response.json();
+    },
+
+    completeSuggestion(evt) {
+      if (this.currentSuggestion === null)
+        return;
+
+      const value = this.$refs.tags.value;
+      const pos = this.inputCursor - this.query.length;
+      const tag = this.suggestions[this.currentSuggestion].display;
+
+      this.$refs.tags.value = mySplice(value, pos, this.query.length,
+        tag + ' ');
+      this.reset();
+      this.$refs.tags.focus();
+
+      // Don't switch focus if we're completing after a Tab press.
+      if (evt.type === "keydown" && evt.keyCode === 9)
+        evt.preventDefault();
+    },
+
+    selectCurrentSuggestion(evt) {
+      this.currentSuggestion = suggestionPosition(evt.currentTarget);
+      this.completeSuggestion(evt);
+    },
+
+    setCurrentSuggestion(evt, amount = 0) {
+      currentSuggestionElement(this.currentSuggestion)
+        ?.classList.remove("suggestion-hover");
+
+      if (evt === 'mouseenter')
+        this.currentSuggestion = suggestionPosition(evt.currentTarget);
+      else {
+        const len = this.suggestions.length;
+        let cur = this.currentSuggestion;
+
+        if (cur === null)
+          cur = amount > 0 ? -1 : amount < 0 ? len : 0;
+        this.currentSuggestion = (cur + amount + len) % len;
+      }
+
+      currentSuggestionElement(this.currentSuggestion)
+        ?.classList.add("suggestion-hover");
+    }
+  }));
+});