CREATE TABLE ybirk.core_user (
    user_id Int32,
    name String,
    age Int32,
    email String,
    registration_date Date
)
ENGINE = MergeTree
ORDER BY user_id;

CREATE TABLE ybirk.core_course (
    course_id Int32,
    title String,
    category String
)
ENGINE = MergeTree
ORDER BY course_id;

CREATE TABLE ybirk.core_lesson (
    lesson_id Int32,
    title String,
    duration_min Int32,
    course_id Int32
)
ENGINE = MergeTree
ORDER BY lesson_id;

CREATE TABLE ybirk.core_fact_lesson_views (
    user_id Int32, 
    lesson_id Int32,
    course_id Int32,
    viewed_at DateTime64(3)
)
ENGINE = MergeTree
ORDER BY user_id;

CREATE TABLE ybirk.core_enrollments (
    id Int32,
    user_id Int32,
    course_id Int32,
    enrolled_at Date
)
ENGINE = MergeTree
ORDER BY user_id;

----------------------------------

CREATE TABLE ybirk.inactive_users_summary
(
user_id UInt32,
name String,
email String,
age UInt8,
registered_courses_count UInt32,
registration_date DateTime64(3, 'UTC')
)
ENGINE = AggregatingMergeTree
ORDER BY (user_id);


CREATE TABLE ybirk.lesson_popularity_summary
(
    lesson_id     UInt32,
    lesson_title  String,
    course_id     UInt32,
    course_title  String,
    total_views   UInt32,
    unique_users  UInt32,
    first_view    DateTime64(3, 'UTC'),
    last_view     DateTime64(3, 'UTC')
)
ENGINE = AggregatingMergeTree
ORDER BY (lesson_id, course_id);


CREATE TABLE ybirk.course_completion_rate
(
    user_id          UInt32,
    user_name        String,
    course_id        UInt32,
    course_title     String,
    lessons_in_course UInt32,
    lessons_viewed    UInt32,
    completion_rate   Float32
)
ENGINE = AggregatingMergeTree
ORDER BY (user_id, course_id);

-------------------------------------------

CREATE MATERIALIZED VIEW ybirk.mv_lesson_popularity_summary
TO ybirk.lesson_popularity_summary
AS
SELECT
    flv.lesson_id AS lesson_id,
    l.title AS lesson_title,
    flv.course_id AS course_id,
    c.title AS course_title,
    count() AS total_views,
    uniqExact(flv.user_id) AS unique_users,
    min(flv.viewed_at) AS first_view,
    max(flv.viewed_at) AS last_view
FROM ybirk.core_fact_lesson_views AS flv
JOIN ybirk.core_lesson  AS l ON flv.lesson_id = l.lesson_id
JOIN ybirk.core_course  AS c ON flv.course_id = c.course_id
GROUP BY
    flv.lesson_id,
    l.title,
    flv.course_id,
    c.title;

CREATE MATERIALIZED VIEW ybirk.mv_inactive_users_summary
TO ybirk.inactive_users_summary
AS
SELECT
    u.user_id AS user_id,
    u.name AS name,
    u.email AS email,
    u.age AS age,
    countDistinct(e.course_id) AS registered_courses_count,
    u.registration_date AS registration_date
FROM ybirk.core_user AS u
LEFT JOIN ybirk.core_enrollments AS e ON u.user_id = e.user_id
WHERE u.user_id NOT IN (
    SELECT DISTINCT user_id
    FROM ybirk.core_fact_lesson_views
)
GROUP BY
    u.user_id,
    u.name,
    u.email,
    u.age,
    u.registration_date;

CREATE MATERIALIZED VIEW ybirk.mv_course_completion_rate
TO ybirk.course_completion_rate
AS
SELECT
    u.user_id AS user_id,
    u.name AS user_name,
    c.course_id AS course_id,
    c.title AS course_title,
    countDistinct(l.lesson_id) AS lessons_in_course,
    countDistinct(flv.lesson_id) AS lessons_viewed,
    if(countDistinct(l.lesson_id) = 0,0,
       round(countDistinct(flv.lesson_id) * 1.0 / countDistinct(l.lesson_id),2)
    ) AS completion_rate
FROM ybirk.core_enrollments AS e
JOIN ybirk.core_user      AS u ON e.user_id   = u.user_id
JOIN ybirk.core_course    AS c ON e.course_id = c.course_id
JOIN ybirk.core_lesson    AS l ON c.course_id = l.course_id
LEFT JOIN ybirk.core_fact_lesson_views AS flv
       ON flv.user_id   = e.user_id
      AND flv.course_id = e.course_id
GROUP BY
    u.user_id,
    u.name,
    c.course_id,
    c.title;

----------------------------------------------

INSERT INTO ybirk.core_user (user_id, name, age, email, registration_date) VALUES
(1, 'Alice', 25, 'alice@mail.com', '2023-01-10'),
(2, 'Bob', 30, 'bob@gmail.com', '2023-02-05'),
(3, 'Charlie', 22, 'charlie@mail.com', '2023-02-20'),
(4, 'Diana', 28, 'diana@mail.com', '2023-03-01'),
(5, 'Ethan', 35, 'ethan@gmail.com', '2023-03-10');

INSERT INTO ybirk.core_course (course_id, title, category) VALUES
(1, 'SQL для начинающих', 'data'),
(2, 'Python для анализа данных', 'programming'),
(3, 'BI с нуля', 'business');

INSERT INTO ybirk.core_lesson (lesson_id, course_id, title, duration_min) VALUES
(1, 1, 'SELECT и FROM', 10),
(2, 1, 'JOIN', 15),
(3, 2, 'Pandas', 20),
(4, 3, 'Основы BI', 12),
(5, 3, 'Метрики и дашборды', 18);

INSERT INTO ybirk.core_fact_lesson_views (user_id, lesson_id, course_id, viewed_at) VALUES
(1, 1, 1, '2023-01-16 10:00:00'),
(1, 2, 1, '2023-01-16 10:15:00'),
(2, 1, 1, '2023-01-21 09:00:00'),
(3, 3, 2, '2023-03-06 12:00:00'),
(4, 4, 3, '2023-04-02 10:00:00'),
(4, 5, 3, '2023-04-03 10:00:00');

INSERT INTO ybirk.core_enrollments (id, user_id, course_id, enrolled_at) VALUES
(1, 1, 1, '2023-01-15'),
(2, 1, 2, '2023-02-01'),
(3, 2, 1, '2023-01-20'),
(4, 3, 2, '2023-03-05'),
(5, 4, 3, '2023-04-01');