--Активность пользователей

--CREATE MATERIALIZED VIEW user_activity_summary AS

--CTE кол-во курсов на которые записан пользователь
WITH enrollment_count AS (
	SELECT 
		pe.user_id,
		COUNT(*) AS enrollment_count
	FROM pet_enrollments pe 
	GROUP BY pe.user_id
),
--CTE просмотренные уникальные уроки пользователем (кол-во)
viewed_lessons_count AS (
	SELECT 
		plv.user_id,
		DENSE_RANK() OVER(
			PARTITION BY plv.user_id
			ORDER BY plv.lesson_id
		) AS viewed_lessons_count
	FROM  pet_lesson_views plv 
),

--CTE дата и время последнего просмотра урока
last_view AS (
	SELECT 
		plv.user_id,
		LAST_VALUE(plv.viewed_at) OVER (
			PARTITION BY plv.user_id
			ORDER BY plv.viewed_at
			ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING 
		) AS last_view
	FROM pet_lesson_views plv
),

--CTE дата и время первого просмотра урока
first_view AS (
	SELECT 
		plv.user_id,
		FIRST_VALUE(plv.viewed_at) OVER (
			PARTITION BY plv.user_id
			ORDER BY plv.viewed_at 
		) AS first_view
	FROM pet_lesson_views plv
),

--CTE кол-во курсов доступных пользователю
lesson_user_all_open AS (
	SELECT 
		pe.user_id,
		pe.course_id,
		COUNT(*) AS lesson_user_all_open
	FROM pet_enrollments pe
	LEFT JOIN pet_lessons pl ON pl.course_id = pe.course_id
	GROUP BY pe.user_id, pe.course_id
	ORDER BY user_id, course_id
)

SELECT 
	pu.id AS user_id, 
	pu.name AS name,
	ec.enrollment_count AS enrollment_count,
	MAX(vlc.viewed_lessons_count) AS viewed_lessons_count,
	last_view,
	first_view,
	ROUND(MAX(vlc.viewed_lessons_count) * 100.0 / lesson_user_all.lesson_user_all_open2, 2) || '%' AS engagement_rate
	
FROM pet_users pu 
LEFT JOIN enrollment_count ec ON pu.id = ec.user_id
LEFT JOIN viewed_lessons_count vlc ON pu.id = vlc.user_id 
LEFT JOIN last_view lv ON pu.id = lv.user_id
LEFT JOIN first_view fv ON pu.id = fv.user_id
LEFT JOIN (
	SELECT 
		user_id, 
		SUM(luao.lesson_user_all_open) AS lesson_user_all_open2
	FROM lesson_user_all_open luao
	GROUP BY user_id
) AS lesson_user_all ON lesson_user_all.user_id = pu.id

GROUP BY pu.id, ec.enrollment_count, last_view, first_view, lesson_user_all.lesson_user_all_open2
ORDER BY pu.id;