CREATE MATERIALIZED VIEW conversion_funnel AS

-- CTE какое кол-во человек записалось на курс 
WITH 

enrolled_users AS (
	SELECT 
		course_id,
		COUNT(*) AS enrolled
	FROM pet_enrollments pe
	GROUP BY course_id
),

-- СТЕ на начавших смотреть курс
started_users AS (
	SELECT 
		pc.id AS course_id,
		COUNT(DISTINCT plv.user_id) AS started
	FROM pet_courses pc
	LEFT JOIN pet_lessons pl 
		ON pc.id = pl.course_id
	LEFT JOIN pet_lesson_views plv
		ON plv.lesson_id = pl.id
	GROUP BY pc.id
),


--СТЕ на кол-во просмотров курса и прогресс по курсу
user_progress AS (
	SELECT
		pc.id AS course_id,
		plv.user_id,
		COUNT(DISTINCT lesson_id) AS count_views,
		count_lesson_in_course.count_lesson_in_course AS count_lesson_in_course,
		COUNT(DISTINCT lesson_id) * 1.0 / count_lesson_in_course AS progress
	
	FROM pet_courses pc

	LEFT JOIN pet_lessons pl 
		ON pl.course_id = pc.id

	LEFT JOIN pet_lesson_views plv 
		ON plv.lesson_id = pl.id

	LEFT JOIN (
		SELECT 
			pl.course_id,
			COUNT(*) AS count_lesson_in_course
		FROM pet_lessons pl
		GROUP BY pl.course_id
	) AS count_lesson_in_course
		ON count_lesson_in_course.course_id = pc.id


	GROUP BY pc.id, plv.user_id, count_lesson_in_course
	
),

main_table AS (
	SELECT 
		pc.id AS course_id,
		pc.title AS course_title,
		'registered' AS stage_name,
		0 AS stage_order,
		(SELECT COUNT(*) FROM pet_users pu) AS users_count,
		ROUND(100, 2) || '%' AS conversion_from_previous,
		ROUND(100, 2) || '%' AS conversion_from_start
		
	FROM pet_courses pc
		
	UNION ALL
		
	SELECT 
		pc.id AS course_id,
		pc.title AS course_title,
		'enrolled' AS stage_name,
		1 AS stage_order,
		enrolled_users.enrolled,
		ROUND(enrolled_users.enrolled * 100.0 / (SELECT COUNT(*) FROM pet_users pu), 2) || '%' AS conversion_from_previous,
		ROUND(enrolled_users.enrolled * 100.0 / (SELECT COUNT(*) FROM pet_users pu), 2) || '%' AS conversion_from_start

	FROM pet_courses pc
	LEFT JOIN enrolled_users
		ON enrolled_users.course_id = pc.id
	
	
	UNION ALL
		
	SELECT 
		pc.id AS course_id,
		pc.title AS course_title,
		'started' AS stage_name,
		2 AS stage_order,
		started_users.started,
		ROUND(started_users.started * 100.0 / enrolled_users.enrolled, 2) || '%' AS conversion_from_previous,
		ROUND(started_users.started * 100.0 / (SELECT COUNT(*) FROM pet_users pu), 2) || '%' AS conversion_from_start

	FROM pet_courses pc
	LEFT JOIN started_users
		ON started_users.course_id = pc.id	
	LEFT JOIN enrolled_users
		ON enrolled_users.course_id = pc.id
		
	UNION ALL
		
	SELECT 
		pc.id AS course_id,
		pc.title AS course_title,
		'mid_progress' AS stage_name,
		3 AS stage_order,
		(	SELECT COUNT(*) FROM user_progress
			WHERE user_progress.course_id = pc.id AND user_progress.progress >= 0.5
		),
		ROUND((	SELECT COUNT(*) FROM user_progress
				WHERE user_progress.course_id = pc.id AND user_progress.progress >= 0.5) * 100.0 / started_users.started, 2) || '%' AS conversion_from_previous,
		ROUND((	SELECT COUNT(*) FROM user_progress
				WHERE user_progress.course_id = pc.id AND user_progress.progress >= 0.5) * 100.0 / (SELECT COUNT(*) FROM pet_users pu), 2) || '%' AS conversion_from_start
		
	FROM pet_courses pc
	LEFT JOIN started_users
		ON started_users.course_id = pc.id	
		
		UNION ALL
		
	SELECT 
		pc.id AS course_id,
		pc.title AS course_title,
		'completed' AS stage_name,
		4 AS stage_order,
		(	SELECT COUNT(*) FROM user_progress
			WHERE user_progress.course_id = pc.id AND user_progress.progress >= 1),
		ROUND((	SELECT COUNT(*) FROM user_progress 
				WHERE user_progress.course_id = pc.id AND user_progress.progress >= 1) * 100.0 / 
			(	SELECT COUNT(*) FROM user_progress
				WHERE user_progress.course_id = pc.id AND user_progress.progress >= 0.5), 2) || '%' AS conversion_from_previous,
		ROUND((	SELECT COUNT(*) FROM user_progress 
				WHERE user_progress.course_id = pc.id AND user_progress.progress >= 1) * 100.0 / 
				(SELECT COUNT(*) FROM pet_users pu), 2) || '%' AS conversion_from_start
	FROM pet_courses pc
	
	ORDER BY course_id, stage_order
)
-- main select
SELECT 
	course_id,
	course_title,
	stage_name,
	users_count,
	conversion_from_previous,
	conversion_from_start
	
FROM main_table;