ALTER TABLE users
ADD COLUMN IF NOT EXISTS profile_visibility VARCHAR(20) NOT NULL DEFAULT 'public'
CHECK (profile_visibility IN ('public', 'friends'));

CREATE TABLE IF NOT EXISTS friendships (
    id SERIAL PRIMARY KEY,
    requester_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    addressee_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    status VARCHAR(20) NOT NULL DEFAULT 'pending'
        CHECK (status IN ('pending', 'accepted')),
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    CHECK (requester_id <> addressee_id),
    UNIQUE (requester_id, addressee_id)
);

CREATE UNIQUE INDEX IF NOT EXISTS idx_friendships_pair
ON friendships (LEAST(requester_id, addressee_id), GREATEST(requester_id, addressee_id));