-- Initial schema for courses, modules, and lessons
CREATE TABLE courses (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    title TEXT NOT NULL,
    description TEXT,
    instructor_id UUID NOT NULL,
    start_date TIMESTAMPTZ,
    end_date TIMESTAMPTZ,
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

CREATE TABLE modules (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    course_id UUID NOT NULL REFERENCES courses(id) ON DELETE CASCADE,
    title TEXT NOT NULL,
    position INT NOT NULL,
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

CREATE TABLE lessons (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    module_id UUID NOT NULL REFERENCES modules(id) ON DELETE CASCADE,
    title TEXT NOT NULL,
    content_type TEXT NOT NULL,
    content_url TEXT,
    position INT NOT NULL,
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

CREATE TABLE audit_logs (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id UUID NOT NULL,
    action TEXT NOT NULL,
    entity_type TEXT NOT NULL,
    entity_id UUID NOT NULL,
    changes JSONB NOT NULL,
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

-- Trigger to update updated_at
CREATE OR REPLACE FUNCTION update_updated_at_column()
RETURNS TRIGGER AS $$
BEGIN
    NEW.updated_at = NOW();
    RETURN NEW;
END;
$$ language 'plpgsql';

CREATE TRIGGER update_courses_updated_at BEFORE UPDATE ON courses FOR EACH ROW EXECUTE PROCEDURE update_updated_at_column();