-- Этап 1. Инициализация проекта
-- Задание 1: Создай схемы

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

-- Задание 2: Создай raw-таблицы

CREATE TABLE raw.users (
	id int,
	name varchar(15),
	age int,
	email varchar(30),
	registration_date DATE
)
DISTRIBUTED BY (id);

CREATE TABLE raw.courses (
	id int,
	title text,
	category varchar(30),
	created_at DATE
)
DISTRIBUTED BY (id);

CREATE TABLE raw.lessons (
	id int,
	course_id int,
	title text,
	duration_min int
)
DISTRIBUTED BY (id);

CREATE TABLE raw.enrollments (
	id int,
	user_id int,
	course_id int,
	enrolled_at DATE
)
DISTRIBUTED BY (id);

CREATE TABLE raw.lesson_views (
	id int,
	user_id int,
	lesson_id int,
	viewed_at timestamp
)
DISTRIBUTED BY (id);

-- Этап 2. Загрузка данных (эмуляция Airflow)
-- Задание 3: Выгрузить данные из PostgreSQL и Загрузить CSV в Greenplum


-- Экспортировал данные из PostgreSQL в CSV-файлы и загрузил их в Greenplum

-- Этап 3. Слой Core — обогащённые данные
-- Задание 4: Измерения (dimension tables)

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

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

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

-- Опционально: измерение времени
CREATE TABLE core.dim_date (
    date DATE PRIMARY KEY,
    year INT,
    month INT,
    day INT,
    weekday TEXT
);

-- Задание 5: Факт (fact table)

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
);

-- Задание 6: ETL переброса данных из raw в core

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

INSERT INTO core.dim_lesson (lesson_id, title, duration_min, course_id) -- ok
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) --заполнить из нескольких таблиц с помощью join
SELECT DISTINCT
	lv.user_id::INT,
	lv.lesson_id::INT,
	le.course_id::INT,
	lv.viewed_at::TIMESTAMP
FROM raw.lesson_views AS lv
JOIN raw.lessons AS le ON lv.lesson_id = le.id;

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

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

INSERT INTO core.dim_date (date, year, month, day, weekday)
SELECT DISTINCT
	d::DATE,
	EXTRACT(YEAR FROM d)::INT,
	EXTRACT(MONTH FROM d)::INT,
	EXTRACT(DAY FROM d)::INT,
	TO_CHAR(d, 'Day')::TEXT
FROM ( 
	SELECT registration_date AS d FROM raw.users
	UNION
	SELECT enrolled_at FROM raw.enrollments
	UNION
	SELECT viewed_at FROM raw.lesson_views
) all_dates
WHERE d IS NOT NULL;

-- Надо сделать, чтобы вместо номера месяца выводилось название месяца

ALTER TABLE core.dim_date
ALTER COLUMN month TYPE text;

UPDATE core.dim_date 
SET month = TO_CHAR(date, 'Month');

-- Этап 4: Подготовка витрин в Greenplum
-- Задание 7: Витрина dm.lesson_popularity_summary

CREATE MATERIALIZED VIEW dm.lesson_popularity_summary AS
SELECT 
	dl.lesson_id,
	dl.title AS lesson_title,
	dl.course_id,
	dc.title AS course_title,
	COUNT(flv.user_id) 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.fact_lesson_views AS flv
JOIN core.dim_lesson AS dl ON flv.lesson_id = dl.lesson_id
JOIN core.dim_course AS dc ON dl.course_id = dc.course_id
GROUP BY dl.lesson_id, dl.title, dl.course_id, dc.title
ORDER BY dl.lesson_id ASC;

-- Задание 8: Витрина dm.inactive_users_summary

CREATE MATERIALIZED VIEW dm.inactive_users_summary AS
SELECT
	du.user_id,
	du.name AS user_name,
	du.email,
	du.age,
	COUNT(e.course_id) AS enrollments_count,
	du.registration_date
FROM core.dim_user AS du
LEFT JOIN core.enrollments AS e ON du.user_id = e.user_id
LEFT JOIN core.fact_lesson_views AS flv ON du.user_id = flv.user_id
WHERE flv.user_id IS NULL
GROUP BY du.user_id, du.name, du.email, du.age, du.registration_date;

-- Задание 9: Витрина dm.course_completion_rate

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

-- 🧪 Этап 5. Проверка
-- Задание 10: Проверь витрины

SELECT * FROM dm.lesson_popularity_summary LIMIT 10;
SELECT * FROM dm.inactive_users_summary LIMIT 10;
SELECT * FROM dm.course_completion_rate ORDER BY user_id ASC LIMIT 10;