const { Op } = require("sequelize");
const sequelize = require("../../config/db.config");
const R = require("../../utils/response.util");
const { paginate } = require("../../utils/paginate.util");

const Course = require("../../models/courses/courses.mdl");
const Unit = require("../../models/courses/units.mdl");
const Lesson = require("../../models/courses/lessons.mdl");
const LessonPage = require("../../models/courses/lesson-page.mdl");
const mdl_Users = require("../../models/users/users.mdl");

const notDeleted = { deletedAt: null };

// ─── Helpers ──────────────────────────────────────────────────────────────────

const auditByFields = ["createdBy", "updatedBy", "deletedBy"];
const adminExclude = [];

// ─── COURSE ───────────────────────────────────────────────────────────────────

exports.getCourses = async (req, res) => {
  try {
    const result = await paginate(Course, req, {
      excludeAttributes: adminExclude,
      auditOptions: { mdl_Users, parentAlias: "Course" },
      context: "list",
      findOptions: { where: { ...notDeleted } },
    });
    return R.success(res, "Courses retrieved.", result);
  } catch (err) {
    console.error("[COURSE][GET ALL]", err);
    return R.error(res, "Could not retrieve courses.", 500);
  }
};

exports.getCourse = async (req, res) => {
  try {
    const { courseId } = req.params;

    const course = await Course.findOne({
      where: { course_id: courseId, ...notDeleted },
      include: [
        {
          model: Unit,
          as: "units",
          where: notDeleted,
          required: false,
          order_index: [["order", "ASC"]],
        },
      ],
      order_index: [[{ model: Unit, as: "units" }, "order_index", "ASC"]],
    });

    if (!course) return R.error(res, "Course not found.", 404);

    return R.success(res, "Course retrieved.", { data: course });
  } catch (err) {
    console.error("[COURSE][GET ONE]", err);
    return R.error(res, "Could not retrieve course.", 500);
  }
};

exports.createCourse = async (req, res) => {
  try {
    const { title, description, order_index } = req.body;
    if (!title) return R.error(res, "Title is required.", 400);

    const course = await Course.create({
      title,
      description: description ?? null,
      order_index: order_index ?? 0,
      createdBy: req.body.createdBy ?? null,
    });

    return R.success(res, "Course created.", { data: course }, 201);
  } catch (err) {
    console.error("[COURSE][CREATE]", err);
    return R.error(res, "Could not create course.", 500);
  }
};

exports.updateCourse = async (req, res) => {
  try {
    const { courseId } = req.params;

    const course = await Course.findOne({ where: { course_id: courseId, ...notDeleted } });
    if (!course) return R.error(res, "Course not found.", 404);

    const { title, description, order_index } = req.body;

    if (title !== undefined) course.title = title;
    if (description !== undefined) course.description = description;
    if (order_index !== undefined) course.order_index = order_index;
    course.updatedBy = req.body.updatedBy ?? null;

    await course.save();

    return R.success(res, "Course updated.", { data: course });
  } catch (err) {
    console.error("[COURSE][UPDATE]", err);
    return R.error(res, "Could not update course.", 500);
  }
};

exports.deleteCourse = async (req, res) => {
  try {
    const { courseId } = req.params;

    const course = await Course.findOne({ where: { course_id: courseId, ...notDeleted } });
    if (!course) return R.error(res, "Course not found.", 404);

    await course.update({ deletedBy: req.body.deletedBy ?? null });
    await course.destroy();

    return R.success(res, "Course deleted.");
  } catch (err) {
    console.error("[COURSE][DELETE]", err);
    return R.error(res, "Could not delete course.", 500);
  }
};

// ─── UNIT ─────────────────────────────────────────────────────────────────────

exports.getUnits = async (req, res) => {
  try {
    const { courseId } = req.params;

    const course = await Course.findOne({ where: { course_id: courseId, ...notDeleted } });
    if (!course) return R.error(res, "Course not found.", 404);

    const result = await paginate(Unit, req, {
      excludeAttributes: adminExclude,
      auditOptions: { mdl_Users, parentAlias: "Unit" },
      context: "list",
      findOptions: {
        where: { course_id: courseId, ...notDeleted },
        order: [["order_index", "ASC"]],
      },
    });

    return R.success(res, "Units retrieved.", result);
  } catch (err) {
    console.error("[UNIT][GET ALL]", err);
    return R.error(res, "Could not retrieve units.", 500);
  }
};

exports.getUnit = async (req, res) => {
  try {
    const { courseId, unitId } = req.params;

    const unit = await Unit.findOne({
      where: { unit_id: unitId, course_id: courseId, ...notDeleted },
      include: [
        {
          model: Lesson,
          as: "lessons",
          where: notDeleted,
          required: false,
          order: [["order_index", "ASC"]],
        },
      ],
      order: [[{ model: Lesson, as: "lessons" }, "order_index", "ASC"]],
    });

    if (!unit) return R.error(res, "Unit not found.", 404);

    return R.success(res, "Unit retrieved.", { data: unit });
  } catch (err) {
    console.error("[UNIT][GET ONE]", err);
    return R.error(res, "Could not retrieve unit.", 500);
  }
};

exports.createUnit = async (req, res) => {
  try {
    const { courseId } = req.params;
    const { title, description, order_index } = req.body;

    if (!title) return R.error(res, "Title is required.", 400);

    const course = await Course.findOne({ where: { course_id: courseId, ...notDeleted } });
    if (!course) return R.error(res, "Course not found.", 404);

    const unit = await Unit.create({
      course_id: courseId,
      title,
      description: description ?? null,
      order_index: order_index ?? 0,
      createdBy: req.body.createdBy ?? null,
    });

    return R.success(res, "Unit created.", { data: unit }, 201);
  } catch (err) {
    console.error("[UNIT][CREATE]", err);
    return R.error(res, "Could not create unit.", 500);
  }
};

exports.updateUnit = async (req, res) => {
  try {
    const { courseId, unitId } = req.params;

    const unit = await Unit.findOne({
      where: { unit_id: unitId, course_id: courseId, ...notDeleted },
    });
    if (!unit) return R.error(res, "Unit not found.", 404);

    const { title, description, order_index } = req.body;

    if (title !== undefined) unit.title = title;
    if (description !== undefined) unit.description = description;
    if (order !== undefined) unit.order = order;
    unit.updatedBy = req.body.updatedBy ?? null;

    await unit.save();

    return R.success(res, "Unit updated.", { data: unit });
  } catch (err) {
    console.error("[UNIT][UPDATE]", err);
    return R.error(res, "Could not update unit.", 500);
  }
};

exports.deleteUnit = async (req, res) => {
  try {
    const { courseId, unitId } = req.params;

    const unit = await Unit.findOne({
      where: { unit_id: unitId, course_id: courseId, ...notDeleted },
    });
    if (!unit) return R.error(res, "Unit not found.", 404);

    await unit.update({ deletedBy: req.body.deletedBy ?? null });
    await unit.destroy();

    return R.success(res, "Unit deleted.");
  } catch (err) {
    console.error("[UNIT][DELETE]", err);
    return R.error(res, "Could not delete unit.", 500);
  }
};

// ─── LESSON ───────────────────────────────────────────────────────────────────

exports.getLessons = async (req, res) => {
  try {
    const { courseId, unitId } = req.params;

    const unit = await Unit.findOne({
      where: { unit_id: unitId, course_id: courseId, ...notDeleted },
    });
    if (!unit) return R.error(res, "Unit not found.", 404);

    const result = await paginate(Lesson, req, {
      excludeAttributes: adminExclude,
      auditOptions: { mdl_Users, parentAlias: "Lesson" },
      context: "list",
      findOptions: {
        where: { unit_id: unitId, ...notDeleted },
        order: [["order_index", "ASC"]],
      },
    });

    return R.success(res, "Lessons retrieved.", result);
  } catch (err) {
    console.error("[LESSON][GET ALL]", err);
    return R.error(res, "Could not retrieve lessons.", 500);
  }
};

exports.getLesson = async (req, res) => {
  try {
    const { courseId, unitId, lessonId } = req.params;

    const lesson = await Lesson.findOne({
      where: { lesson_id: lessonId, unit_id: unitId, ...notDeleted },
      include: [
        {
          model: LessonPage,
          as: "page",
          required: false,
        },
        {
          model: Unit,
          as: "unit",
          where: { course_id: courseId, ...notDeleted },
        },
      ],
    });

    if (!lesson) return R.error(res, "Lesson not found.", 404);

    return R.success(res, "Lesson retrieved.", { data: lesson });
  } catch (err) {
    console.error("[LESSON][GET ONE]", err);
    return R.error(res, "Could not retrieve lesson.", 500);
  }
};

exports.createLesson = async (req, res) => {
  try {
    const { courseId, unitId } = req.params;
    const { title, description, order_index } = req.body;

    if (!title) return R.error(res, "Title is required.", 400);

    const unit = await Unit.findOne({
      where: { unit_id: unitId, course_id: courseId, ...notDeleted },
    });
    if (!unit) return R.error(res, "Unit not found.", 404);

    const lesson = await Lesson.create({
      unit_id: unitId,
      title,
      description: description ?? null,
      order_index: order_index ?? 0,
      createdBy: req.body.createdBy ?? null,
    });

    // ── Auto-create an empty page for this lesson ─────────────────────────────
    await LessonPage.create({
      lesson_id: lesson.lesson_id,
      blocks: [],
      createdBy: req.body.createdBy ?? null,
    });

    return R.success(res, "Lesson created.", { data: lesson }, 201);
  } catch (err) {
    console.error("[LESSON][CREATE]", err);
    return R.error(res, "Could not create lesson.", 500);
  }
};

exports.updateLesson = async (req, res) => {
  try {
    const { courseId, unitId, lessonId } = req.params;

    const lesson = await Lesson.findOne({
      where: {
        lesson_id: lessonId,
        unit_id: unitId,
        ...notDeleted,
      },
      include: [{
        model: Unit,
        as: "unit",
        where: { course_id: courseId, ...notDeleted },
      }],
    });
    if (!lesson) return R.error(res, "Lesson not found.", 404);

    const { title, description, order_index } = req.body;

    if (title !== undefined) lesson.title = title;
    if (description !== undefined) lesson.description = description;
    if (order_index !== undefined) lesson.order_index = order_index;
    lesson.updatedBy = req.body.updatedBy ?? null;

    await lesson.save();

    return R.success(res, "Lesson updated.", { data: lesson });
  } catch (err) {
    console.error("[LESSON][UPDATE]", err);
    return R.error(res, "Could not update lesson.", 500);
  }
};

exports.deleteLesson = async (req, res) => {
  try {
    const { courseId, unitId, lessonId } = req.params;

    const lesson = await Lesson.findOne({
      where: { lesson_id: lessonId, unit_id: unitId, ...notDeleted },
      include: [{
        model: Unit,
        as: "unit",
        where: { course_id: courseId, ...notDeleted },
      }],
    });
    if (!lesson) return R.error(res, "Lesson not found.", 404);

    await lesson.update({ deletedBy: req.body.deletedBy ?? null });
    await lesson.destroy();

    return R.success(res, "Lesson deleted.");
  } catch (err) {
    console.error("[LESSON][DELETE]", err);
    return R.error(res, "Could not delete lesson.", 500);
  }
};

// ─── LESSON PAGE ──────────────────────────────────────────────────────────────

exports.getLessonPage = async (req, res) => {
  try {
    const { lessonId } = req.params;

    const page = await LessonPage.findOne({
      where: { lesson_id: lessonId },
    });

    if (!page) return R.error(res, "Lesson page not found.", 404);

    return R.success(res, "Lesson page retrieved.", { data: page });
  } catch (err) {
    console.error("[LESSON PAGE][GET]", err);
    return R.error(res, "Could not retrieve lesson page.", 500);
  }
};

exports.upsertLessonPage = async (req, res) => {
  try {
    const { lessonId } = req.params;
    const { blocks }   = req.body;

    if (!Array.isArray(blocks)) return R.error(res, "blocks must be an array.", 400);

    const lesson = await Lesson.findOne({ where: { lesson_id: lessonId, ...notDeleted } });
    if (!lesson) return R.error(res, "Lesson not found.", 404);

    const [page, created] = await LessonPage.upsert({
      lesson_id: lessonId,
      blocks,
      updatedBy: req.body.updatedBy ?? null,
      createdBy: req.body.updatedBy ?? null,
    }, {
      returning: true,
    });

    return R.success(
      res,
      created ? "Lesson page created." : "Lesson page updated.",
      { data: page },
      created ? 201 : 200,
    );
  } catch (err) {
    console.error("[LESSON PAGE][UPSERT]", err);
    return R.error(res, "Could not save lesson page.", 500);
  }
};