feat: add summary and search commands (#54)

* feat: add summary and search commands

Signed-off-by: Frost Ming <me@frostming.com>

* fix formats

Signed-off-by: Frost Ming <me@frostming.com>

* fix: clean up

Signed-off-by: Frost Ming <me@frostming.com>

handlers/summary/messages.py

@@ -0,0 +1,164 @@
+import os
+import sqlite3
+from dataclasses import dataclass
+from datetime import datetime, timedelta, timezone
+
+
+@dataclass(frozen=True)
+class ChatMessage:
+    chat_id: int
+    message_id: int
+    content: str
+    user_id: int
+    user_name: str
+    timestamp: datetime
+
+
+@dataclass(frozen=True)
+class StatsEntry:
+    date: str
+    message_count: int
+
+
+class MessageStore:
+    def __init__(self, db_file: str):
+        parent_folder = os.path.dirname(db_file)
+        if not os.path.exists(parent_folder):
+            os.makedirs(parent_folder)
+        self._db_file = db_file
+        self._init_db()
+
+    def connect(self) -> sqlite3.Connection:
+        """Create a new database connection."""
+        return sqlite3.connect(self._db_file)
+
+    def _init_db(self):
+        with self.connect() as conn:
+            conn.execute(
+                """
+                CREATE TABLE IF NOT EXISTS messages (
+                    chat_id INTEGER,
+                    message_id INTEGER,
+                    content TEXT,
+                    user_id INTEGER,
+                    user_name TEXT,
+                    timestamp TEXT,
+                    PRIMARY KEY (chat_id, message_id)
+                );
+            """
+            )
+            conn.execute(
+                """
+                CREATE INDEX IF NOT EXISTS idx_chat_timestamp ON messages (chat_id, timestamp);
+            """
+            )
+            conn.commit()
+
+    def add_message(
+        self, message: ChatMessage, conn: sqlite3.Connection | None = None
+    ) -> None:
+        need_close = False
+        if conn is None:
+            conn = self.connect()
+            need_close = True
+        try:
+            conn.execute(
+                """
+                INSERT OR REPLACE INTO messages (chat_id, message_id, content, user_id, user_name, timestamp)
+                VALUES (?, ?, ?, ?, ?, ?);
+                """,
+                (
+                    message.chat_id,
+                    message.message_id,
+                    message.content,
+                    message.user_id,
+                    message.user_name,
+                    message.timestamp.isoformat(),
+                ),
+            )
+            self._clean_old_messages(message.chat_id, conn)
+            conn.commit()
+        finally:
+            if need_close:
+                conn.close()
+
+    def get_messages_since(self, chat_id: int, since: datetime) -> list[ChatMessage]:
+        with self.connect() as conn:
+            cursor = conn.cursor()
+            cursor.execute(
+                """
+                SELECT chat_id, message_id, content, user_id, user_name, timestamp
+                FROM messages
+            WHERE chat_id = ? AND timestamp >= ?
+            ORDER BY timestamp ASC;
+        """,
+                (chat_id, since.isoformat()),
+            )
+            rows = cursor.fetchall()
+        return [
+            ChatMessage(
+                chat_id=row[0],
+                message_id=row[1],
+                content=row[2],
+                user_id=row[3],
+                user_name=row[4],
+                timestamp=datetime.fromisoformat(row[5]),
+            )
+            for row in rows
+        ]
+
+    def get_stats(self, chat_id: int) -> list[StatsEntry]:
+        with self.connect() as conn:
+            self._clean_old_messages(chat_id, conn)
+            cursor = conn.cursor()
+            cursor.execute(
+                """
+                SELECT DATE(timestamp), COUNT(*)
+                FROM messages
+                WHERE chat_id = ?
+            GROUP BY DATE(timestamp)
+            ORDER BY DATE(timestamp) ASC;
+        """,
+                (chat_id,),
+            )
+            rows = cursor.fetchall()
+        return [StatsEntry(date=row[0], message_count=row[1]) for row in rows]
+
+    def search_messages(
+        self, chat_id: int, keyword: str, limit: int = 10
+    ) -> list[ChatMessage]:
+        # TODO: Fuzzy search with full-text search or similar
+        with self.connect() as conn:
+            cursor = conn.cursor()
+            cursor.execute(
+                """
+                SELECT chat_id, message_id, content, user_id, user_name, timestamp
+                FROM messages
+                WHERE chat_id = ? AND content LIKE ?
+                ORDER BY timestamp DESC
+                LIMIT ?;
+            """,
+                (chat_id, f"%{keyword}%", limit),
+            )
+            rows = cursor.fetchall()
+        return [
+            ChatMessage(
+                chat_id=row[0],
+                message_id=row[1],
+                content=row[2],
+                user_id=row[3],
+                user_name=row[4],
+                timestamp=datetime.fromisoformat(row[5]),
+            )
+            for row in rows
+        ]
+
+    def _clean_old_messages(
+        self, chat_id: int, conn: sqlite3.Connection, days: int = 7
+    ) -> None:
+        cursor = conn.cursor()
+        threshold_date = datetime.now(tz=timezone.utc) - timedelta(days=days)
+        cursor.execute(
+            "DELETE FROM messages WHERE chat_id = ? AND timestamp < ?;",
+            (chat_id, threshold_date.isoformat()),
+        )