BEGIN;

CREATE MATERIALIZED VIEW course_summary AS 
WITH courses_users AS (
SELECT 
	c.id AS course_id,
	c.title AS course_name,
	COUNT(DISTINCT user_id) AS unique_users
FROM courses c
LEFT join enrollments e ON c.id = e.course_id 
GROUP BY c.id, c.title
), 
courses_views AS (
    SELECT 
        l.course_id, 
        COUNT(DISTINCT l.id) AS lessons_count,
        COUNT(lv.id) AS total_views,
        MAX(lv.viewed_at) AS last_viewed_at,
        MIN(lv.viewed_at) AS first_viewed_at
    FROM lessons l
    JOIN lesson_views lv ON l.id = lv.lesson_id 
    GROUP BY l.course_id
)
SELECT 
	cu.course_id,
	cu.course_name,
	cu.unique_users,
	cv.lessons_count,
	cv.total_views,
	ROUND(cv.total_views::DECIMAL / NULLIF(cu.unique_users, 0), 2) AS avg_views_per_user,
	cv.first_viewed_at,
	cv.last_viewed_at
FROM courses_users cu
LEFT JOIN courses_views cv USING(course_id)
ORDER BY cu.course_id;

COMMIT;