feat(chat): added chat interface and connection to ollama (#10)

Co-authored-by: Sharang Parnerkar <parnerkarsharang@gmail.com>
Reviewed-on: #10

src/models/chat.rs

@@ -11,6 +11,19 @@ pub enum ChatRole {
     System,
 }
 
+/// Namespace for grouping chat sessions in the sidebar.
+///
+/// Sessions are visually separated in the chat sidebar by namespace,
+/// with `News` sessions appearing under a dedicated "News Chats" header.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize, Default)]
+pub enum ChatNamespace {
+    /// General user-initiated chat conversations.
+    #[default]
+    General,
+    /// Chats originating from news article follow-ups on the dashboard.
+    News,
+}
+
 /// The type of file attached to a chat message.
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 pub enum AttachmentKind {
@@ -36,36 +49,59 @@ pub struct Attachment {
     pub size_bytes: u64,
 }
 
-/// A single message in a chat conversation.
+/// A persisted chat session stored in MongoDB.
+///
+/// Messages are stored separately in the `chat_messages` collection
+/// and loaded on demand when the user opens a session.
 ///
 /// # Fields
 ///
-/// * `id` - Unique message identifier
+/// * `id` - MongoDB document ID (hex string)
+/// * `user_sub` - Keycloak subject ID (session owner)
+/// * `title` - Display title (auto-generated or user-renamed)
+/// * `namespace` - Grouping for sidebar sections
+/// * `provider` - LLM provider used (e.g. "ollama", "openai")
+/// * `model` - Model ID used (e.g. "llama3.1:8b")
+/// * `created_at` - ISO 8601 creation timestamp
+/// * `updated_at` - ISO 8601 last-activity timestamp
+/// * `article_url` - Source article URL (for News namespace sessions)
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct ChatSession {
+    #[serde(default, alias = "_id", skip_serializing_if = "String::is_empty")]
+    pub id: String,
+    pub user_sub: String,
+    pub title: String,
+    #[serde(default)]
+    pub namespace: ChatNamespace,
+    pub provider: String,
+    pub model: String,
+    pub created_at: String,
+    pub updated_at: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub article_url: Option<String>,
+}
+
+/// A single persisted message within a chat session.
+///
+/// Stored in the `chat_messages` MongoDB collection, linked to a
+/// `ChatSession` via `session_id`.
+///
+/// # Fields
+///
+/// * `id` - MongoDB document ID (hex string)
+/// * `session_id` - Foreign key to `ChatSession.id`
 /// * `role` - Who sent this message
-/// * `content` - The message text content
-/// * `attachments` - Optional file attachments
-/// * `timestamp` - ISO 8601 timestamp string
+/// * `content` - Message text content (may contain markdown)
+/// * `attachments` - File attachments (Phase 2, currently empty)
+/// * `timestamp` - ISO 8601 timestamp
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 pub struct ChatMessage {
+    #[serde(default, alias = "_id", skip_serializing_if = "String::is_empty")]
     pub id: String,
+    pub session_id: String,
     pub role: ChatRole,
     pub content: String,
+    #[serde(default)]
     pub attachments: Vec<Attachment>,
     pub timestamp: String,
 }
-
-/// A chat session containing a conversation history.
-///
-/// # Fields
-///
-/// * `id` - Unique session identifier
-/// * `title` - Display title (usually derived from first message)
-/// * `messages` - Ordered list of messages in the session
-/// * `created_at` - ISO 8601 creation timestamp
-#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
-pub struct ChatSession {
-    pub id: String,
-    pub title: String,
-    pub messages: Vec<ChatMessage>,
-    pub created_at: String,
-}