-- Витрина активности пользователей
CREATE MATERIALIZED VIEW user_activity_summary as
 with 
    lessons_cte as (
        select 
            user_id,
            count (*) as viewed_lessons_count,
            max(viewed_at) as last_view,
            min(viewed_at) as first_view
        from lesson_views
        group by user_id
    ),
    enrollments_cte as (
        select user_id, count(*) as enrollment_count
        from enrollments as e 
        group by user_id
    ),
    engagement_cte as (
        select user_id, count(*) as possible_lessons
        from lessons as l
        join enrollments as en on l.course_id = en.course_id
        group by user_id
    )   
    select 
        id as user_id, 
        name, 
        e.enrollment_count,
        l.viewed_lessons_count,
        l.last_view,
        l.first_view,
        round(l.viewed_lessons_count::decimal * 100 / en.possible_lessons, 2) as engagement_rate
    from users as u
    join lessons_cte as l on u.id = l.user_id
    join engagement_cte as en on u.id = en.user_id
    join enrollments_cte as e on u.id = e.user_id;