-- =====================================================
-- TABLE: education.courses
-- =====================================================
-- Proyecto: OrbiQuant IA (Trading Platform)
-- Módulo: OQI-002 - Education
-- Especificación: ET-EDU-001-database.md
-- =====================================================

CREATE TABLE education.courses (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),

  -- Información básica
  title VARCHAR(200) NOT NULL,
  slug VARCHAR(200) NOT NULL UNIQUE,
  short_description VARCHAR(500),
  full_description TEXT,

  -- Categorización
  category_id UUID NOT NULL REFERENCES education.categories(id) ON DELETE RESTRICT,
  difficulty_level education.difficulty_level NOT NULL DEFAULT 'beginner',

  -- Contenido
  thumbnail_url VARCHAR(500),
  trailer_url VARCHAR(500), -- Video de presentación

  -- Metadata educativa
  duration_minutes INTEGER, -- Duración estimada total
  prerequisites TEXT[], -- IDs de cursos prerequisitos
  learning_objectives TEXT[], -- Array de objetivos

  -- Instructor
  instructor_id UUID NOT NULL REFERENCES auth.users(id) ON DELETE RESTRICT,
  instructor_name VARCHAR(200), -- Denormalizado para performance

  -- Pricing (para futuras features)
  is_free BOOLEAN DEFAULT true,
  price_usd DECIMAL(10,2),

  -- Gamificación
  xp_reward INTEGER DEFAULT 0, -- XP al completar el curso

  -- Estado
  status education.course_status DEFAULT 'draft',
  published_at TIMESTAMPTZ,

  -- Estadísticas (denormalizadas)
  total_modules INTEGER DEFAULT 0,
  total_lessons INTEGER DEFAULT 0,
  total_enrollments INTEGER DEFAULT 0,
  avg_rating DECIMAL(3,2) DEFAULT 0.00,
  total_reviews INTEGER DEFAULT 0,

  -- Metadata
  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
  updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),

  CONSTRAINT valid_rating CHECK (avg_rating >= 0 AND avg_rating <= 5),
  CONSTRAINT valid_price CHECK (price_usd >= 0)
);

-- Índices
CREATE INDEX idx_courses_category ON education.courses(category_id);
CREATE INDEX idx_courses_slug ON education.courses(slug);
CREATE INDEX idx_courses_status ON education.courses(status);
CREATE INDEX idx_courses_difficulty ON education.courses(difficulty_level);
CREATE INDEX idx_courses_instructor ON education.courses(instructor_id);
CREATE INDEX idx_courses_published ON education.courses(published_at) WHERE status = 'published';

-- Comentarios
COMMENT ON TABLE education.courses IS 'Cursos del módulo educativo';
COMMENT ON COLUMN education.courses.instructor_name IS 'Denormalizado para performance en queries';
COMMENT ON COLUMN education.courses.prerequisites IS 'Array de UUIDs de cursos prerequisitos';
COMMENT ON COLUMN education.courses.learning_objectives IS 'Array de objetivos de aprendizaje';
COMMENT ON COLUMN education.courses.xp_reward IS 'XP otorgado al completar el curso';