2 files changed, 105 insertions, 0 deletions
diff --git a/backend/app/db/__init__.py b/backend/app/db/__init__.py
new file mode 100644
index 0000000..a6e0ed0
--- /dev/null
+++ b/backend/app/db/__init__.py
@@ -0,0 +1 @@
+"""SQLite persistence package."""
diff --git a/backend/app/db/watchlist.py b/backend/app/db/watchlist.py
new file mode 100644
index 0000000..238cf35
--- /dev/null
+++ b/backend/app/db/watchlist.py
@@ -0,0 +1,104 @@
+"""SQLite watchlist persistence for one local default profile."""
+from __future__ import annotations
+
+import sqlite3
+from datetime import datetime, timezone
+from pathlib import Path
+
+DEFAULT_DB_PATH = Path(__file__).resolve().parents[2] / "data" / "prism.db"
+WATCHLIST_LIMIT = 10
+
+
+class WatchlistFullError(ValueError):
+    """Raised when the local watchlist already has the maximum number of symbols."""
+
+
+def normalize_symbol(symbol: str) -> str:
+    cleaned = str(symbol or "").strip().upper()
+    if not cleaned:
+        raise ValueError("symbol is required")
+    if len(cleaned) > 16:
+        raise ValueError("symbol is too long")
+    return cleaned
+
+
+def connect(db_path: Path | str = DEFAULT_DB_PATH) -> sqlite3.Connection:
+    path = Path(db_path)
+    path.parent.mkdir(parents=True, exist_ok=True)
+    conn = sqlite3.connect(path)
+    conn.row_factory = sqlite3.Row
+    return conn
+
+
+def init_db(db_path: Path | str = DEFAULT_DB_PATH) -> None:
+    with connect(db_path) as conn:
+        conn.execute(
+            """
+            CREATE TABLE IF NOT EXISTS profiles (
+                id INTEGER PRIMARY KEY,
+                name TEXT UNIQUE NOT NULL
+            )
+            """
+        )
+        conn.execute(
+            """
+            CREATE TABLE IF NOT EXISTS watchlist (
+                profile_id INTEGER NOT NULL,
+                symbol TEXT NOT NULL,
+                created_at TEXT NOT NULL,
+                UNIQUE(profile_id, symbol),
+                FOREIGN KEY(profile_id) REFERENCES profiles(id)
+            )
+            """
+        )
+        conn.execute("INSERT OR IGNORE INTO profiles(name) VALUES (?)", ("default",))
+
+
+def get_default_profile_id(conn: sqlite3.Connection) -> int:
+    row = conn.execute("SELECT id FROM profiles WHERE name = ?", ("default",)).fetchone()
+    if row is None:
+        conn.execute("INSERT INTO profiles(name) VALUES (?)", ("default",))
+        row = conn.execute("SELECT id FROM profiles WHERE name = ?", ("default",)).fetchone()
+    return int(row["id"])
+
+
+def list_symbols(db_path: Path | str = DEFAULT_DB_PATH) -> list[dict[str, str]]:
+    init_db(db_path)
+    with connect(db_path) as conn:
+        profile_id = get_default_profile_id(conn)
+        rows = conn.execute(
+            "SELECT symbol, created_at FROM watchlist WHERE profile_id = ? ORDER BY created_at ASC",
+            (profile_id,),
+        ).fetchall()
+    return [{"symbol": row["symbol"], "created_at": row["created_at"]} for row in rows]
+
+
+def add_symbol(symbol: str, db_path: Path | str = DEFAULT_DB_PATH) -> dict[str, str]:
+    sym = normalize_symbol(symbol)
+    init_db(db_path)
+    with connect(db_path) as conn:
+        profile_id = get_default_profile_id(conn)
+        existing = conn.execute(
+            "SELECT symbol, created_at FROM watchlist WHERE profile_id = ? AND symbol = ?",
+            (profile_id, sym),
+        ).fetchone()
+        if existing:
+            return {"symbol": existing["symbol"], "created_at": existing["created_at"]}
+        count = conn.execute("SELECT COUNT(*) AS c FROM watchlist WHERE profile_id = ?", (profile_id,)).fetchone()["c"]
+        if int(count) >= WATCHLIST_LIMIT:
+            raise WatchlistFullError("watchlist limit reached")
+        created_at = datetime.now(timezone.utc).isoformat()
+        conn.execute(
+            "INSERT INTO watchlist(profile_id, symbol, created_at) VALUES (?, ?, ?)",
+            (profile_id, sym, created_at),
+        )
+    return {"symbol": sym, "created_at": created_at}
+
+
+def remove_symbol(symbol: str, db_path: Path | str = DEFAULT_DB_PATH) -> bool:
+    sym = normalize_symbol(symbol)
+    init_db(db_path)
+    with connect(db_path) as conn:
+        profile_id = get_default_profile_id(conn)
+        cur = conn.execute("DELETE FROM watchlist WHERE profile_id = ? AND symbol = ?", (profile_id, sym))
+        return cur.rowcount > 0