CREATE SEQUENCE global_id_seq START WITH 1000000 INCREMENT BY 1;

CREATE OR REPLACE FUNCTION random_between_two()
RETURNS VARCHAR AS $$
BEGIN
    IF random() < 0.5 THEN
        RETURN 'A';
    ELSE
        RETURN 'B';
    END IF;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION random_between_days()
RETURNS INTEGER AS $$
BEGIN
    RETURN floor(random() * 5 + 1)::INTEGER;
END;
$$ LANGUAGE plpgsql;

CREATE TABLE IF NOT EXISTS Uhrzeit ( 
  ID SERIAL PRIMARY KEY,
  anfangszeit TIME NOT NULL,
  endzeit TIME NOT NULL
);

CREATE TABLE IF NOT EXISTS Veranstaltung( 
  name VARCHAR(3) PRIMARY KEY,
  ort VARCHAR(1) DEFAULT random_between_two(),
  raum INTEGER NOT NULL,
  dauer INTEGER NOT NULL,
  used_in_plan INTEGER DEFAULT 0
);

CREATE TABLE IF NOT EXISTS Veranstalter(
  ID INTEGER PRIMARY KEY DEFAULT nextval('global_id_seq'), 
  name VARCHAR(30),
  email VARCHAR(30),
  passwort VARCHAR(30),
  arbeitszeit INTEGER DEFAULT 0,
  admin BOOLEAN NOT NULL DEFAULT FALSE
);

CREATE TABLE IF NOT EXISTS StundeImPlan (
  uhrzeit INTEGER REFERENCES Uhrzeit(ID),
  tag INTEGER NOT NULL,
  veranstaltung VARCHAR(3) REFERENCES Veranstaltung(name),
  veranstalter INTEGER REFERENCES Veranstalter(ID),
  PRIMARY KEY(uhrzeit, tag)
);

CREATE TABLE IF NOT EXISTS Krank(
  ID SERIAL PRIMARY KEY,
  stundeImPlan_uhrzeit INTEGER,
  stundeImPlan_tag INTEGER,
  veranstalter INTEGER REFERENCES Veranstalter(ID),
  krank BOOLEAN DEFAULT FALSE,
  FOREIGN KEY (stundeImPlan_uhrzeit, stundeImPlan_tag) REFERENCES StundeImPlan(uhrzeit, tag)
);

-- Function to delete StundeImPlan when Veranstaltung is deleted
CREATE OR REPLACE FUNCTION delete_stundeimplan_for_veranstaltung()
RETURNS TRIGGER AS $$
BEGIN
    DELETE FROM StundeImPlan WHERE veranstaltung = OLD.name;
    RETURN OLD;
END;
$$ LANGUAGE plpgsql;

-- Trigger to call the above function
CREATE TRIGGER trg_delete_stundeimplan_for_veranstaltung
AFTER DELETE ON Veranstaltung
FOR EACH ROW
EXECUTE FUNCTION delete_stundeimplan_for_veranstaltung();

-- Function to update StundeImPlan when Veranstalter is deleted
CREATE OR REPLACE FUNCTION update_stundeimplan_for_veranstalter()
RETURNS TRIGGER AS $$
DECLARE
    new_veranstalter_id INTEGER;
BEGIN
    SELECT ID INTO new_veranstalter_id
    FROM Veranstalter
    WHERE arbeitszeit < 18
    ORDER BY arbeitszeit ASC
    LIMIT 1;

    IF new_veranstalter_id IS NOT NULL THEN
        UPDATE StundeImPlan
        SET veranstalter = new_veranstalter_id
        WHERE veranstalter = OLD.ID;
    END IF;

    RETURN OLD;
END;
$$ LANGUAGE plpgsql;

-- Trigger to call the above function
CREATE TRIGGER trg_update_stundeimplan_for_veranstalter
AFTER DELETE ON Veranstalter
FOR EACH ROW
EXECUTE FUNCTION update_stundeimplan_for_veranstalter();

-- Function to update arbeitszeit of Veranstalter when assigned to StundeImPlan
CREATE OR REPLACE FUNCTION update_arbeitszeit_for_veranstalter()
RETURNS TRIGGER AS $$
BEGIN
    UPDATE Veranstalter
    SET arbeitszeit = arbeitszeit + (SELECT dauer FROM Veranstaltung WHERE name = NEW.veranstaltung)
    WHERE ID = NEW.veranstalter;
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

-- Trigger to call the above function
CREATE TRIGGER trg_update_arbeitszeit_for_veranstalter
AFTER INSERT ON StundeImPlan
FOR EACH ROW
EXECUTE FUNCTION update_arbeitszeit_for_veranstalter();

-- Function to generate the plan
CREATE OR REPLACE FUNCTION generate_plan()
RETURNS TRIGGER AS $$
DECLARE
    v_row RECORD;
    u_row RECORD;
    available_veranstalter RECORD;
    random_day INTEGER;
BEGIN
    -- Loop through each available time slot
    FOR u_row IN SELECT * FROM Uhrzeit LOOP
        -- Loop through each available Veranstaltung
        FOR v_row IN SELECT * FROM Veranstaltung WHERE used_in_plan = 0 LOOP
            -- Find an available Veranstalter
            SELECT * INTO available_veranstalter
            FROM Veranstalter
            WHERE arbeitszeit + v_row.dauer <= 18
            ORDER BY arbeitszeit ASC
            LIMIT 1;

            IF FOUND THEN
                -- Check if there is already an event scheduled for this tag and uhrzeit combination
                
                random_day = random_between_days();
                IF NOT EXISTS (
                    SELECT 1
                    FROM StundeImPlan
                    WHERE uhrzeit = u_row.ID AND tag = random_day
                ) THEN
                    -- If an available Veranstalter is found, insert into StundeImPlan
                    INSERT INTO StundeImPlan (uhrzeit, tag, veranstaltung, veranstalter)
                    VALUES (u_row.ID, random_day, v_row.name, available_veranstalter.ID);

                    -- Update the used_in_plan flag and arbeitszeit
                    UPDATE Veranstaltung SET used_in_plan = used_in_plan + 1 WHERE name = v_row.name;
                    UPDATE Veranstalter SET arbeitszeit = arbeitszeit + v_row.dauer WHERE ID = available_veranstalter.ID;
                END IF;
            END IF;
        END LOOP;
    END LOOP;
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER trg_generate_plan
AFTER INSERT ON Veranstaltung
FOR EACH STATEMENT
EXECUTE FUNCTION generate_plan();

CREATE OR REPLACE FUNCTION handle_krank_insert()
RETURNS TRIGGER AS $$
DECLARE
    new_veranstalter_id INTEGER;
    v_name VARCHAR(3);
BEGIN
    -- Find a new veranstalter for the same stundeImPlan
    SELECT veranstaltung.name INTO v_name
    FROM Veranstaltung
    WHERE name = (SELECT veranstaltung FROM StundeImPlan WHERE uhrzeit = NEW.stundeImPlan_uhrzeit AND tag = NEW.stundeImPlan_tag);

    WITH PreviousHour AS (
        SELECT sp.veranstalter, v.ort
        FROM StundeImPlan sp
        JOIN Veranstaltung v ON sp.veranstaltung = v.name
        WHERE sp.uhrzeit = NEW.stundeImPlan_uhrzeit - 1
          AND sp.tag = NEW.stundeImPlan_tag
    )
    SELECT ID INTO new_veranstalter_id
    FROM Veranstalter v
    JOIN StundeImPlan sp ON v.ID = sp.veranstalter
    JOIN Veranstaltung va ON sp.veranstaltung = va.name
    LEFT JOIN PreviousHour ph ON sp.uhrzeit = NEW.stundeImPlan_uhrzeit AND sp.tag = NEW.stundeImPlan_tag - 1
    WHERE arbeitszeit + (SELECT dauer FROM Veranstaltung WHERE name = v_name) <= 18
      AND NOT EXISTS (
          SELECT 1
          FROM Krank k
          WHERE k.veranstalter = v.ID
            AND k.stundeImPlan_uhrzeit = NEW.stundeImPlan_uhrzeit
            AND k.stundeImPlan_tag = NEW.stundeImPlan_tag
      )
      AND (ph.veranstalter IS NULL OR v.ID <> ph.veranstalter OR va.ort = ph.ort)
    ORDER BY arbeitszeit ASC
    LIMIT 1;

    SELECT ID INTO new_veranstalter_id
    FROM Veranstalter v
    WHERE arbeitszeit + (SELECT dauer FROM Veranstaltung WHERE name = v_name) <= 18
      AND NOT EXISTS (
        SELECT 1
        FROM Krank k
        WHERE k.veranstalter = v.ID
        AND k.stundeImPlan_uhrzeit = NEW.stundeImPlan_uhrzeit
        AND k.stundeImPlan_tag = NEW.stundeImPlan_tag
    );


    UPDATE Veranstalter
    SET arbeitszeit = arbeitszeit + (SELECT dauer FROM Veranstaltung WHERE name = v_name)
    WHERE ID = new_veranstalter_id;

    -- Update the StundeImPlan with the replacement or NULL
    UPDATE StundeImPlan
    SET veranstalter = COALESCE(new_veranstalter_id, NULL)
    WHERE uhrzeit = NEW.stundeImPlan_uhrzeit AND tag = NEW.stundeImPlan_tag;

    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER trg_handle_krank_insert
AFTER INSERT ON Krank
FOR EACH ROW
EXECUTE FUNCTION handle_krank_insert();

INSERT INTO Uhrzeit (anfangszeit, endzeit) VALUES 
    ('08:00:00', '10:00:00'), 
    ('10:00:00', '12:00:00'), 
    ('12:00:00', '14:00:00'), 
    ('14:00:00', '16:00:00'), 
    ('16:00:00', '18:00:00'); 

INSERT INTO Veranstalter (name, email, passwort, admin) VALUES
('Davids', 'admin@example.com', 'password123', TRUE),
('Dalitz', 'user1@example.com', 'password1', FALSE),
('Tipp', 'user2@example.com', 'password2', FALSE),
('Quix', 'user3@example.com', 'password3', FALSE),
('Nietsche', 'user4@example.com', 'password4', FALSE),
('Ueberholz', 'user5@example.com', 'password5', FALSE),
('Rethmann', 'user6@example.com', 'password6', FALSE),
('Pohle-Fröhlich', 'user7@example.com', 'password7', FALSE),
('Stockmann', 'user8@example.com', 'password8', FALSE),
('Gref', 'user9@example.com', 'password9', FALSE),
('Naroska', 'user10@example.com', 'password10', FALSE),
('Grothe', 'user11@example.com', 'supersicherespasswort123', FALSE);


INSERT INTO Veranstaltung (ort, raum, name, dauer) VALUES 
('A', '101', 'GDI', 2),
('B', '202', 'ALD', 4),
('A', '103', 'ITS', 2),
('B', '204', 'BSY', 4),
('A', '105', 'PE1', 2),
('B', '206', 'THI', 4),
('A', '107', 'DBS', 2),
('B', '208', 'WEB', 2),
('A', '109', 'BVA', 2),
('B', '210', 'MA1', 2);