add filter by book to user search route

app/views/user.py

@@ -1,6 +1,7 @@
 from flask import Blueprint, render_template, request, flash, redirect, url_for, jsonify
 from flask_login import login_required
 from app.controllers import create_pagination
+from sqlalchemy import not_
 
 from app import models as m, db
 from app import forms as f
@@ -92,8 +93,18 @@ def search():
     if not q:
         return jsonify({"message": "q parameter is required"}), 422
 
-    users = m.User.query.order_by(m.User.username).filter(m.User.username.like(f"{q}%"))
-    users = users.limit(configuration.MAX_SEARCH_RESULTS)
-    users = [{"username": user.username, "id": user.id} for user in users.all()]
+    book_id = request.args.get("book_id", type=str, default=None)
+
+    query_user = m.User.query
+    query_user = query_user.order_by(m.User.username)
+
+    query_user = query_user.filter(m.User.username.ilike(f"{q}%"))
+    if book_id:
+        book_contributors = m.BookContributor.query.filter_by(book_id=book_id).all()
+        user_ids = [contributor.user_id for contributor in book_contributors]
+        query_user = query_user.filter(not_(m.User.id.in_(user_ids)))
+    query_user = query_user.limit(configuration.MAX_SEARCH_RESULTS)
+
+    users = [{"username": user.username, "id": user.id} for user in query_user.all()]
 
     return jsonify({"users": users})