-- Restaurant Database Management System
--
-- Instructions:
-- 1. Create all required tables.
-- 2. Design appropriate PRIMARY KEY and FOREIGN KEY relationships.
-- 3. Add suitable constraints based on the requirements.
-- 4. Insert initial mock data.
-- 5. Insert at least 3 menu items.
-- 6. The script should be executable from start to finish without errors.
DROP TABLE IF EXISTS order_details;
DROP TABLE IF EXISTS orders;
DROP TABLE IF EXISTS menu_items;
DROP TABLE IF EXISTS users;
-- =======================================================
-- USER TABLE
-- =======================================================
--
-- Represents customers using the system.
--
-- Required information:
-- - Unique identifier
-- - Username
-- - Password
-- - Email (optional)
--
-- Requirements:
-- - Each user must have a unique identifier.
-- - Usernames must be unique.
-- - Username and password are required.
-- - Passwords should not be stored in plain text.
--
-- CREATE TABLE ...
CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    username VARCHAR(50) UNIQUE NOT NULL,
    password VARCHAR(255) NOT NULL,
    email VARCHAR(100)
);
-- =======================================================
-- MENU ITEM TABLE
-- =======================================================
--
-- Represents available food and drink items.
--
-- Required information:
-- - Unique identifier
-- - Name
-- - Description (optional)
-- - Price
-- - Category (optional)
--
-- Requirements:
-- - Each menu item must have a unique identifier.
-- - Name is required.
-- - Price must always be positive.
--
-- CREATE TABLE ...
CREATE TABLE menu_items (
    id SERIAL PRIMARY KEY,
    name VARCHAR(100) NOT NULL,
    description TEXT,
    price DECIMAL(10, 2) NOT NULL CHECK (price > 0),
    category VARCHAR(50)
);
-- =======================================================
-- ORDER TABLE
-- =======================================================
--
-- Represents orders placed by customers.
--
-- Required information:
-- - Unique identifier
-- - Reference to customer
-- - Creation date and time
-- - Total price
--
-- Requirements:
-- - Each order must belong to exactly one user.
-- - A user can have multiple orders.
-- - The relationship between User and Order must be implemented.
--
-- Note:
-- Avoid using reserved SQL keywords as table names.
-- Consider using a name such as "orders" or "customer_orders".
--
-- CREATE TABLE ...
CREATE TABLE orders (
    id SERIAL PRIMARY KEY,
    user_id INTEGER NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    total_price DECIMAL(10, 2) NOT NULL,

    CONSTRAINT fk_user
                    FOREIGN KEY (user_id)
                    REFERENCES users(id)
                    ON DELETE CASCADE
);
-- =======================================================
-- ORDER DETAIL TABLE
-- =======================================================
--
-- Represents items inside an order.
--
-- Required information:
-- - Unique identifier
-- - Reference to an order
-- - Reference to a menu item
-- - Quantity
-- - Item price at purchase time
--
-- Requirements:
-- - Each detail record must belong to one order.
-- - Each detail record must reference one menu item.
-- - Quantity must always be greater than zero.
-- - Store the item's price at the moment of purchase.
--
-- CREATE TABLE ...
CREATE TABLE order_details (
    id SERIAL PRIMARY KEY,
    order_id INTEGER NOT NULL,
    menu_item_id INTEGER NOT NULL,
    quantity INTEGER NOT NULL CHECK (quantity > 0),
    unit_price DECIMAL(10, 2) NOT NULL,

    CONSTRAINT fk_order
        FOREIGN KEY (order_id)
        REFERENCES orders(id)
        ON DELETE CASCADE,

    CONSTRAINT fk_menu_item
        FOREIGN KEY (menu_item_id)
        REFERENCES menu_items(id)
);
-- =======================================================
-- INITIAL MENU DATA
-- =======================================================
--
-- Insert at least 3 food or drink items.
--
-- Example categories:
-- - Pizza
-- - Burger
-- - Pasta
-- - Drink
--
-- INSERT INTO ...
INSERT INTO menu_items(name, description, price, category) VALUES ('Margherita Pizza', 'Classic pizza with tomato and mozzarella', 12.99, 'Pizza'),
                                                                  ('Pepperoni Pizza', 'Pizza with pepperoni and cheese', 14.99, 'Pizza'),
                                                                  ('Cheeseburger', 'Beef burger with cheddar cheese', 10.99, 'Burger'),
                                                                  ('Spaghetti Carbonara', 'Pasta with eggs, cheese, and pancetta', 13.99, 'Pasta'),
                                                                  ('Coca-Cola', 'Classic carbonated soft drink', 3.99, 'Drink'),
                                                                  ('Sparkling Water', 'Natural sparkling mineral water', 2.99, 'Drink');
-- =======================================================
-- OPTIONAL TEST DATA
-- =======================================================
--
-- You may insert sample users and orders for testing.
-- This section is optional.
--
-- INSERT INTO ...



-- =======================================================
-- VERIFICATION QUERIES
-- =======================================================
--
-- Uncomment these queries to verify your database.
--
-- SELECT * FROM ...;
-- SELECT * FROM ...;
-- SELECT * FROM ...;
-- SELECT * FROM ...;