CREATE SCHEMA raw;    
CREATE SCHEMA core;     
CREATE SCHEMA dm;

CREATE TABLE raw.users (
    id INT,
    name VARCHAR(255),
    age INT,
    email VARCHAR(255),
    registration_date DATE
);

CREATE TABLE raw.courses (
    id INT,
    title VARCHAR(255),
    category VARCHAR(255),
    created_at DATE
);

CREATE TABLE raw.lessons (
    id INT,
    course_id INT,
    title VARCHAR(255),
    duration_min INT
);

CREATE TABLE raw.enrollments (
    id INT,
    user_id INT,
    course_id INT,
    enrolled_at DATE
);

CREATE TABLE raw.lesson_views (
    id INT,
    user_id INT,
    lesson_id INT,
    viewed_at TIMESTAMP
);

CREATE TABLE core.dim_user (
    user_id INT PRIMARY KEY,
    name TEXT,
    age INT,
    email TEXT,
    registration_date DATE
);

CREATE TABLE core.dim_course (
    course_id INT PRIMARY KEY,
    title TEXT,
    category TEXT
);

CREATE TABLE core.dim_lesson (
    lesson_id INT PRIMARY KEY,
    title TEXT,
    duration_min INT,
    course_id INT REFERENCES core.dim_course(course_id)
);

CREATE TABLE core.fact_lesson_views (
    user_id INT REFERENCES core.dim_user(user_id),
    lesson_id INT REFERENCES core.dim_lesson(lesson_id),
    course_id INT REFERENCES core.dim_course(course_id),
    viewed_at TIMESTAMP
);

CREATE TABLE core.enrollments (
    user_id INT REFERENCES core.dim_user(user_id),
    course_id INT REFERENCES core.dim_course(course_id),
    enrolled_at TIMESTAMP
);

INSERT INTO core.dim_user (user_id, name, age, email, registration_date)
SELECT DISTINCT 
    id::INT,
    name::TEXT,
    age::INT,
    email::TEXT,
    registration_date::DATE  
FROM raw.users;

INSERT INTO core.dim_course (course_id, title, category)
SELECT DISTINCT 
    id::INT,
    title::TEXT,
    category::TEXT
FROM raw.courses;

INSERT INTO core.dim_lesson (lesson_id, title, duration_min, course_id)
SELECT DISTINCT 
    id::INT,
    title::TEXT,
    duration_min::INT,
    course_id::INT
FROM raw.lessons;

INSERT INTO core.fact_lesson_views (user_id, lesson_id, course_id, viewed_at)
SELECT DISTINCT
    rw.user_id::INT,
    rw.lesson_id::INT,
    l.course_id::INT,
    rw.viewed_at::TIMESTAMP
FROM raw.lesson_views rw
JOIN raw.lessons l ON rw.lesson_id = l.id;


INSERT INTO core.enrollments (user_id, course_id, enrolled_at)
SELECT DISTINCT 
    user_id::INT,
    course_id::INT,
    enrolled_at::DATE
FROM raw.enrollments;

CREATE MATERIALIZED VIEW dm.dm_lesson_popularity_summary AS
SELECT 
    dl.lesson_id,
    dl.title AS lesson_title,
    dc.course_id,
    dc.title AS course_title,
    COUNT(*) AS total_views,
    COUNT(DISTINCT flv.user_id) AS unique_users,
    MIN(flv.viewed_at) AS first_view,
    MAX(flv.viewed_at) AS last_view
FROM core.dim_lesson dl
JOIN core.dim_course dc ON dc.course_id = dl.course_id
JOIN core.fact_lesson_views flv ON flv.lesson_id = dl.lesson_id
GROUP BY dl.lesson_id, dl.title, dc.course_id, dc.title;


/*

 Цель:
    Показать популярность каждого урока.

  Поля витрины:
    - lesson_id      — идентификатор урока
    - lesson_title   — название урока
    - course_id      — идентификатор курса
    - course_title   — название курса
    - total_views    — общее число просмотров урока
    - unique_users   — количество уникальных пользователей
    - first_view     — дата первого просмотра
    - last_view      — дата последнего просмотра

*/


CREATE MATERIALIZED VIEW dm.dm_inactive_users_summary AS
SELECT 
    du.user_id,
    du.name AS user_name,
    du.email,
    du.age,
    COUNT(DISTINCT e.course_id) AS enrollments_count,
    du.registration_date
FROM core.dim_user du
LEFT JOIN core.enrollments e ON e.user_id = du.user_id
WHERE NOT EXISTS (
    SELECT 1 
    FROM core.fact_lesson_views flv 
    WHERE flv.user_id = du.user_id
)
GROUP BY du.user_id, du.name, du.email, du.age, du.registration_date;

/*

Цель:
    Определить невовлечённых пользователей и потенциальный отток.

  Поля витрины:
    - user_id            — идентификатор пользователя
    - user_name          — имя
    - email              — почта
    - age                — возраст
    - enrollments_count  — количество курсов
    - registration_date  — дата регистрации

*/

CREATE MATERIALIZED VIEW dm.course_completion_rate AS
SELECT 
    du.user_id,
    du.name AS user_name,
    c.course_id,
    c.title AS course_title,
    COUNT(DISTINCT dl.lesson_id) AS lessons_in_course,
    COUNT(DISTINCT flv.lesson_id) AS lessons_viewed,
    ROUND(
        COUNT(DISTINCT flv.lesson_id) * 1.0 / 
        NULLIF(COUNT(DISTINCT dl.lesson_id), 0), 
        2
    ) AS completion_rate
FROM core.dim_user du
JOIN core.enrollments e ON du.user_id = e.user_id
JOIN core.dim_course c ON e.course_id = c.course_id
JOIN core.dim_lesson dl ON c.course_id = dl.course_id
LEFT JOIN core.fact_lesson_views flv ON dl.lesson_id = flv.lesson_id 
    AND flv.user_id = du.user_id
GROUP BY du.user_id, du.name, c.course_id, c.title
ORDER BY du.user_id, c.course_id;

/*

 Цель:
    Анализировать, насколько пользователи проходят курсы до конца.

  Поля витрины:
    - user_id            — идентификатор пользователя
    - user_name          — имя пользователя
    - course_id          — идентификатор курса
    - course_title       — название курса
    - total_lessons      — количество уроков в курсе
    - lessons_viewed     — число просмотренных уроков
    - completion_rate    — lessons_viewed / total_lessons

*/