-- Modules under an exam-prep unit (table name unit_modules avoids sqlc/LMS collision with public.modules).
CREATE TABLE exam_prep.unit_modules (
    id BIGSERIAL PRIMARY KEY,
    unit_id BIGINT NOT NULL REFERENCES exam_prep.units (id) ON DELETE CASCADE,
    name VARCHAR(255) NOT NULL,
    description TEXT,
    thumbnail TEXT,
    icon TEXT,
    sort_order INTEGER NOT NULL DEFAULT 0,
    created_at TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMPTZ
);

CREATE INDEX idx_exam_prep_unit_modules_unit_id ON exam_prep.unit_modules (unit_id);
CREATE INDEX idx_exam_prep_unit_modules_unit_sort ON exam_prep.unit_modules (unit_id, sort_order, id);