feat: filter and search by tag

internal/storage/sqlite.go

@@ -155,7 +155,13 @@ func (s *SQLiteStorage) Search(query string) []*note.Note {
         SELECT id, path, title, content, updated_at, size, published
         FROM notes
         WHERE lower(content) LIKE lower(?)
-    `, pattern)
+        OR id IN (
+            SELECT nt.note_id
+            FROM note_tags nt
+            JOIN tags t ON t.id = nt.tag_id
+            WHERE lower(t.name) LIKE lower(?)
+        )
+    `, pattern, pattern)
 	if err != nil {
 		return []*note.Note{}
 	}

internal/storage/sqlite_test.go

@@ -187,3 +187,27 @@ func TestSQLiteStorage_Tags(t *testing.T) {
 		t.Fatalf("expected remaining tag rust, got %+v", tags)
 	}
 }
+
+func TestSQLiteStorage_SearchByTag(t *testing.T) {
+	st := newSQLiteStorage(t)
+
+	ts := time.Date(2026, 2, 3, 12, 0, 0, 0, time.UTC)
+	if err := st.Create(sampleNote("n1", "notes/alpha.md", "Alpha", "no match", ts)); err != nil {
+		t.Fatalf("create note: %v", err)
+	}
+	if err := st.Create(sampleNote("n2", "notes/beta.md", "Beta", "content", ts)); err != nil {
+		t.Fatalf("create note: %v", err)
+	}
+
+	if err := st.AddTag("n2", "Go"); err != nil {
+		t.Fatalf("add tag: %v", err)
+	}
+
+	results := st.Search("go")
+	if len(results) != 1 {
+		t.Fatalf("expected 1 result, got %d", len(results))
+	}
+	if results[0].ID != "n2" {
+		t.Fatalf("expected tag match to be n2")
+	}
+}

internal/storage/storage.go

@@ -67,13 +67,25 @@ func (ns *NoteStorage) Search(query string) []*note.Note {
 	for _, note := range ns.Index {
 		lowContent := strings.ToLower(string(note.Content))
 		lowQuery := strings.ToLower(query)
-		if strings.Contains(lowContent, lowQuery) {
+		if strings.Contains(lowContent, lowQuery) || tagsContain(note.Tags, lowQuery) {
 			results = append(results, note)
 		}
 	}
 	return results
 }
 
+func tagsContain(tags []string, query string) bool {
+	if query == "" {
+		return false
+	}
+	for _, tag := range tags {
+		if strings.Contains(strings.ToLower(tag), query) {
+			return true
+		}
+	}
+	return false
+}
+
 func (ns *NoteStorage) AddTag(noteID, tag string) error {
 	n, ok := ns.Index[noteID]
 	if !ok {

internal/storage/storage_test.go

@@ -51,3 +51,20 @@ func TestNoteStorageGetUpdate(t *testing.T) {
 		t.Errorf("Updating a note should reflect it in storage. Wanted '%s', got '%s'\n", n1.Content, nn2.Content)
 	}
 }
+
+func TestNoteStorageSearch_Tags(t *testing.T) {
+	ns = NewNoteStorage()
+
+	n := note.NewNote()
+	n.Path = "note3.md"
+	n.ID = note.GenerateNoteID(n.Path)
+	n.Content = "no tag here"
+	n.Tags = []string{"devops", "go"}
+
+	ns.Create(n)
+
+	results := ns.Search("go")
+	if len(results) != 1 {
+		t.Fatalf("expected 1 result, got %d", len(results))
+	}
+}

internal/web/handler.go

@@ -54,6 +54,7 @@ type ViewState struct {
 	RenderedNote template.HTML
 	SortBy       string
 	SearchTerm   string
+	TagFilter    string
 	LastActive   string
 }
 
@@ -79,6 +80,7 @@ func (h *Handler) buildViewState(r *http.Request) (*ViewState, error) {
 	}
 
 	searchTerm := query.Get("search")
+	tagFilter := query.Get("tag")
 
 	// Get notes from service
 	var notes []*note.Note
@@ -111,10 +113,15 @@ func (h *Handler) buildViewState(r *http.Request) (*ViewState, error) {
 		}
 	}
 
+	if tagFilter != "" {
+		notes = filterNotesByTag(notes, tagFilter)
+	}
+
 	return &ViewState{
 		Notes:      notes,
 		SortBy:     sortBy,
 		SearchTerm: searchTerm,
+		TagFilter:  tagFilter,
 	}, nil
 }
 
@@ -166,6 +173,24 @@ func (h *Handler) handleNotes(w http.ResponseWriter, r *http.Request) {
 	h.templates.Render(w, "index", state)
 }
 
+func filterNotesByTag(notes []*note.Note, tag string) []*note.Note {
+	tag = strings.ToLower(strings.TrimSpace(tag))
+	if tag == "" {
+		return notes
+	}
+
+	filtered := make([]*note.Note, 0, len(notes))
+	for _, n := range notes {
+		for _, t := range n.Tags {
+			if strings.EqualFold(t, tag) {
+				filtered = append(filtered, n)
+				break
+			}
+		}
+	}
+	return filtered
+}
+
 func (h *Handler) handleTags(w http.ResponseWriter, r *http.Request) {
 	if r.Method != http.MethodPost {
 		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)

internal/web/handler_test.go

@@ -277,3 +277,31 @@ func TestHandlerTags_Remove(t *testing.T) {
 		t.Fatalf("expected tag to be removed, got %+v", n.Tags)
 	}
 }
+
+func TestHandlerRoot_TagFilter(t *testing.T) {
+	env := newTestEnv(t)
+
+	if err := env.storage.AddTag("a1", "go"); err != nil {
+		t.Fatalf("seed tag: %v", err)
+	}
+	if err := env.storage.AddTag("b2", "rust"); err != nil {
+		t.Fatalf("seed tag: %v", err)
+	}
+
+	req := httptest.NewRequest(http.MethodGet, "/?tag=go", nil)
+	rec := httptest.NewRecorder()
+
+	env.handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected status 200, got %d", rec.Code)
+	}
+
+	body := rec.Body.String()
+	if strings.Contains(body, noteMarker("b2")) {
+		t.Fatalf("expected non-matching note to be excluded")
+	}
+	if !strings.Contains(body, noteMarker("a1")) {
+		t.Fatalf("expected matching note to be included")
+	}
+}

internal/web/static/css/main.css

@@ -170,6 +170,7 @@
   }
 
   .last-modified {
+    text-align: right;
     font-size: 0.75em;
     opacity: 0.7;
   }
@@ -290,20 +291,36 @@
     gap: 0.4em;
   }
 
+  .tag-chip {
+    display: inline-flex;
+    align-items: center;
+    gap: 0.35em;
+    background: var(--background2);
+    border: 1px solid var(--border-color);
+    border-radius: 999px;
+    padding: 0.2em 0.45em;
+  }
+
+  .tag-link {
+    color: var(--url);
+    font-size: 0.8em;
+  }
+
   .tag-remove-form {
     display: inline;
   }
 
-  .tag {
-    background: var(--background2);
-    padding: 0.25em 0.6em;
-    border-radius: 4px;
-    color: var(--url);
-    font-size: 0.8em;
-    white-space: nowrap;
-    border: 1px solid var(--border-color);
+  .tag-remove {
+    border: 0;
+    background: var(--background3);
+    color: var(--text1);
+    width: 1.4em;
+    height: 1.4em;
+    border-radius: 999px;
+    line-height: 1;
   }
-  .tag:hover {
+
+  .tag-remove:hover {
     background: var(--background-hover);
     cursor: pointer;
   }

internal/web/templates/metadata.tmpl

@@ -11,9 +11,12 @@
     </form>
     <div class="meta-tags">
       {{ range .Note.Tags }}
-      <form method="POST" action="/notes/{{ $.Note.ID }}/tags/{{ . }}" class="tag-remove-form">
-        <button type="submit" class="tag">{{ . }} ×</button>
+      <span class="tag-chip">
+        <a class="tag-link" href="/?tag={{ . | urlquery }}">{{ . }}</a>
+        <form method="POST" action="/notes/{{ $.Note.ID }}/tags/{{ . | urlquery }}" class="tag-remove-form">
+          <button type="submit" class="tag-remove" aria-label="Remove tag {{ . }}">×</button>
         </form>
+      </span>
       {{ end }}
     </div>
   </section>

internal/web/templates/noteList.tmpl

@@ -23,6 +23,7 @@
 
 {{ define "renderSearch" }}
 {{ if ne .SearchTerm "" }}<h2>Matching results for query '{{ .SearchTerm }}'</h2>{{ end }}
+{{ if ne .TagFilter "" }}<h2>Filtered by tag '{{ .TagFilter }}'</h2>{{ end }}
   <ul class="search-results">
     {{ range .Notes }}
     <li {{ if eq .ID $.LastActive }}class="active-note"{{ end }}>