CREATE TYPE node_type AS ENUM ('marker', 'restaurant');
CREATE EXTENSION postgis;

CREATE TABLE nodes(
	id SERIAL PRIMARY KEY,
	name VARCHAR(100) NOT NULL,
	node_type NODE_TYPE NOT NULL,
	coordinates GEOMETRY(POINT,4326) NOT NULL
);

CREATE OR REPLACE FUNCTION check_linked_restaurants()
RETURNS TRIGGER AS $$
BEGIN
    -- Check if the node is being updated from 'restaurant' to a different type
    IF OLD.node_type = 'restaurant' AND NEW.node_type <> 'restaurant' THEN
        -- Check if the node still has linked restaurants
        IF EXISTS (SELECT 1 FROM restaurants WHERE node_id = OLD.id) THEN
            RAISE EXCEPTION 'Cannot change node type from "restaurant" as it still has linked restaurants';
        END IF;
    END IF;
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER check_linked_restaurants_trigger
BEFORE UPDATE OF node_type ON nodes
FOR EACH ROW
EXECUTE FUNCTION check_linked_restaurants();


CREATE TABLE restaurants(
	id SERIAL PRIMARY KEY,
	node_id INTEGER REFERENCES nodes(id) NOT NULL,
	address VARCHAR(30) NOT NULL,
	price SMALLINT CHECK ( price >= 0 AND price <= 10 ) NOT NULL
);

CREATE FUNCTION check_node_type()
RETURNS TRIGGER AS $$
BEGIN
	-- Check if the node referenced by the foreign key is of type 'restaurant'
    IF (SELECT node_type FROM nodes WHERE id = NEW.node_id) <> 'restaurant' THEN
        RAISE EXCEPTION 'The referenced node has not type "restaurant"';
    END IF;
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER enforce_node_type
BEFORE INSERT OR UPDATE ON restaurants
FOR EACH ROW
EXECUTE FUNCTION check_node_type();

CREATE TABLE images(
	id SERIAL PRIMARY KEY,
	url VARCHAR(50) NOT NULL
);

CREATE TABLE users(
	id SERIAL PRIMARY KEY,
	name VARCHAR(20) NOT NULL,
	uuid UUID NOT NULL,
	avatar_id INTEGER REFERENCES images(id),

	UNIQUE(uuid)
);

CREATE TABLE restaurant_ratings(
	id SERIAL PRIMARY KEY,
	restaurant_id INTEGER REFERENCES restaurants(id) NOT NULL,
	user_id INTEGER REFERENCES users(id) NOT NULL,
	note VARCHAR(100) NOT NULL DEFAULT ''
);

CREATE TABLE meals(
	id SERIAL PRIMARY KEY,
	restaurant_rating_id INTEGER REFERENCES restaurant_ratings(id) NOT NULL,
	user_id INTEGER REFERENCES users(id) NOT NULL,
	name VARCHAR(30) NOT NULL,
	rating SMALLINT CHECK ( rating >= 0 AND rating <= 10 ) NOT NULL,
	price DECIMAL(12,2) CHECK (price >= 0) NOT NULL,
	price_currency VARCHAR(1) CHECK (TRIM(price_currency) <> '') NOT NULL,
	note VARCHAR(100) NOT NULL DEFAULT '',
	date DATE NOT NULL
);

CREATE TABLE meal_images(
	image_id INTEGER NOT NULL,
	meal_id INTEGER NOT NULL,
	CONSTRAINT image_id_constraint FOREIGN KEY (image_id) REFERENCES images(id),
	CONSTRAINT meal_id_constraint FOREIGN KEY (meal_id) REFERENCES meals(id),
	PRIMARY KEY(image_id,meal_id)
);