move collection and extraction of articles into their own file; add custom response cache

internal/model/sqlite/articles.go

@@ -85,3 +85,25 @@ func (m *ArticleModel) Insert(a *model.Article) error {
     _, err = m.DB.Exec(stmt, lastId, a.Title, a.Author, a.Content)
     return err
 }
+
+// TODO docstring
+func (m *ArticleModel) Update(a *model.Article) error {
+    // begin transaction 
+    _, err := m.DB.Begin()
+    if err != nil { return err }
+
+    // insert article
+    stmt := `UPDATE articles 
+             SET title = ?, sourceUrl = ?, author = ?, content = ?, publishDate = ?, fetchDate = ?
+             WHERE id = ?
+    `
+    _, err = m.DB.Exec(stmt, a.Title, a.SourceUrl, a.Author, a.Content, a.PublishDate, a.FetchDate, a.Identifier)
+    if err != nil { return err }
+
+    // insert into fts_articles for full-text search
+    stmt = `INSERT INTO fts_articles (id, content)
+             VALUES (?, ? || '\n' || ? || '\n' || ?)
+    `
+    _, err = m.DB.Exec(stmt, a.Identifier, a.Title, a.Author, a.Content)
+    return err
+}