BEGIN;

CREATE MATERIALIZED VIEW user_activity_summary AS 
WITH users_views AS (
SELECT
	u.id AS user_id,
	u.name, 
	COUNT(DISTINCT lv.lesson_id) AS viewed_lessons_count,
	MAX(lv.viewed_at) AS last_view,
	MIN(lv.viewed_at) AS first_view
FROM users AS u
JOIN lesson_views AS lv on u.id = lv.user_id
GROUP BY u.id

),
users_engagement AS (
SELECT 
	e.user_id AS user_id,
	COUNT(DISTINCT l.id) AS lessons_cnt,
	COUNT(DISTINCT course_id) AS enrollment_count
FROM enrollments AS e
JOIN lessons AS l using(course_id)
GROUP BY e.user_id
)

SELECT 
	uv.user_id,
	uv.name,
	ue.enrollment_count,
	uv.viewed_lessons_count,
	uv.last_view,
	uv.first_view,
	ROUND(uv.viewed_lessons_count::DECIMAL / NULLIF(ue.lessons_cnt, 0) * 100, 2)  AS engagement_rate
FROM users_views AS uv
LEFT JOIN users_engagement AS ue using (user_id)
ORDER BY uv.user_id

COMMIT;