package handlers

import (
	"Yimaru-Backend/internal/domain"
	"Yimaru-Backend/internal/services/lessons"
	"Yimaru-Backend/internal/services/modules"
	"context"
	"errors"
	"strconv"

	"github.com/gofiber/fiber/v2"
)

// CreateLesson godoc
// @Summary Create lesson
// @Tags lessons
// @Accept json
// @Produce json
// @Param moduleId path int true "Module ID"
// @Param body body domain.CreateLessonInput true "Lesson"
// @Router /api/v1/modules/{moduleId}/lessons [post]
func (h *Handler) CreateLesson(c *fiber.Ctx) error {
	moduleID, err := strconv.ParseInt(c.Params("moduleId"), 10, 64)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid module id",
			Error:   err.Error(),
		})
	}
	var req domain.CreateLessonInput
	if err := c.BodyParser(&req); err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid request body",
			Error:   err.Error(),
		})
	}
	if valErrs, ok := h.validator.Validate(c, req); !ok {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Validation failed",
			Error:   firstValidationError(valErrs),
		})
	}
	les, err := h.lessonSvc.Create(c.Context(), moduleID, req)
	if err != nil {
		if errors.Is(err, modules.ErrModuleNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Module not found",
				Error:   err.Error(),
			})
		}
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to create lesson",
			Error:   err.Error(),
		})
	}
	actorID := c.Locals("user_id").(int64)
	actorRole := string(c.Locals("role").(domain.Role))
	ip := c.IP()
	ua := c.Get("User-Agent")
	rid := les.ID
	go h.activityLogSvc.RecordAction(context.Background(), &actorID, &actorRole, domain.ActionLessonCreated, domain.ResourceLesson, &rid, "Created lesson: "+les.Title, nil, &ip, &ua)

	return c.Status(fiber.StatusCreated).JSON(domain.Response{
		Message:    "Lesson created successfully",
		Data:       les,
		Success:    true,
		StatusCode: fiber.StatusCreated,
	})
}

// ListLessonsByModule godoc
// @Tags lessons
// @Param moduleId path int true "Module ID"
// @Param limit query int false "Page size" default(20)
// @Param offset query int false "Offset" default(0)
// @Router /api/v1/modules/{moduleId}/lessons [get]
func (h *Handler) ListLessonsByModule(c *fiber.Ctx) error {
	moduleID, err := strconv.ParseInt(c.Params("moduleId"), 10, 64)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid module id",
			Error:   err.Error(),
		})
	}
	limit, _ := strconv.Atoi(c.Query("limit", "20"))
	offset, _ := strconv.Atoi(c.Query("offset", "0"))
	publishedOnly := !h.canManageLessons(c)
	items, total, err := h.lessonSvc.ListByModule(c.Context(), moduleID, publishedOnly, int32(limit), int32(offset))
	if err != nil {
		if errors.Is(err, modules.ErrModuleNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Module not found",
				Error:   err.Error(),
			})
		}
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to list lessons",
			Error:   err.Error(),
		})
	}
	uid := c.Locals("user_id").(int64)
	role := c.Locals("role").(domain.Role)
	for i := range items {
		if err := h.lmsProgressSvc.ApplyAccessLesson(c.Context(), role, uid, &items[i]); err != nil {
			return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
				Message: "Failed to build lesson list",
				Error:   err.Error(),
			})
		}
	}
	return c.JSON(domain.Response{
		Message: "Lessons retrieved successfully",
		Data: fiber.Map{
			"lessons":     items,
			"total_count": total,
			"limit":       limit,
			"offset":      offset,
		},
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// GetLesson godoc
// @Tags lessons
// @Param id path int true "Lesson ID"
// @Router /api/v1/lessons/{id} [get]
func (h *Handler) GetLesson(c *fiber.Ctx) error {
	id, err := strconv.ParseInt(c.Params("id"), 10, 64)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid lesson id",
			Error:   err.Error(),
		})
	}
	les, err := h.lessonSvc.GetByID(c.Context(), id)
	if err != nil {
		if errors.Is(err, lessons.ErrLessonNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Lesson not found",
				Error:   err.Error(),
			})
		}
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to load lesson",
			Error:   err.Error(),
		})
	}
	if !les.VisibleToLearners() && !h.canManageLessons(c) {
		return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
			Message: "Lesson not found",
			Error:   lessons.ErrLessonNotFound.Error(),
		})
	}
	uid := c.Locals("user_id").(int64)
	role := c.Locals("role").(domain.Role)
	if err := h.lmsProgressSvc.ApplyAccessLesson(c.Context(), role, uid, &les); err != nil {
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to evaluate lesson access",
			Error:   err.Error(),
		})
	}
	if err := lmsBlockIfInaccessible(c, les.Access); err != nil {
		return err
	}
	return c.JSON(domain.Response{
		Message:    "Lesson retrieved successfully",
		Data:       les,
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// UpdateLesson godoc
// @Tags lessons
// @Param id path int true "Lesson ID"
// @Param body body domain.UpdateLessonInput true "Fields to update"
// @Router /api/v1/lessons/{id} [put]
func (h *Handler) UpdateLesson(c *fiber.Ctx) error {
	id, err := strconv.ParseInt(c.Params("id"), 10, 64)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid lesson id",
			Error:   err.Error(),
		})
	}
	var req domain.UpdateLessonInput
	if err := c.BodyParser(&req); err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid request body",
			Error:   err.Error(),
		})
	}
	les, err := h.lessonSvc.Update(c.Context(), id, req)
	if err != nil {
		if errors.Is(err, lessons.ErrLessonNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Lesson not found",
				Error:   err.Error(),
			})
		}
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to update lesson",
			Error:   err.Error(),
		})
	}
	actorID := c.Locals("user_id").(int64)
	actorRole := string(c.Locals("role").(domain.Role))
	ip := c.IP()
	ua := c.Get("User-Agent")
	rid := les.ID
	go h.activityLogSvc.RecordAction(context.Background(), &actorID, &actorRole, domain.ActionLessonUpdated, domain.ResourceLesson, &rid, "Updated lesson: "+les.Title, nil, &ip, &ua)

	return c.JSON(domain.Response{
		Message:    "Lesson updated successfully",
		Data:       les,
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// DeleteLesson godoc
// @Tags lessons
// @Param id path int true "Lesson ID"
// @Router /api/v1/lessons/{id} [delete]
func (h *Handler) DeleteLesson(c *fiber.Ctx) error {
	id, err := strconv.ParseInt(c.Params("id"), 10, 64)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid lesson id",
			Error:   err.Error(),
		})
	}
	if err := h.lessonSvc.Delete(c.Context(), id); err != nil {
		if errors.Is(err, lessons.ErrLessonNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Lesson not found",
				Error:   err.Error(),
			})
		}
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to delete lesson",
			Error:   err.Error(),
		})
	}
	actorID := c.Locals("user_id").(int64)
	actorRole := string(c.Locals("role").(domain.Role))
	ip := c.IP()
	ua := c.Get("User-Agent")
	go h.activityLogSvc.RecordAction(context.Background(), &actorID, &actorRole, domain.ActionLessonDeleted, domain.ResourceLesson, &id, "Deleted lesson", nil, &ip, &ua)

	return c.JSON(domain.Response{
		Message:    "Lesson deleted successfully",
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// CompleteLesson godoc
// @Summary Mark a lesson as completed
// @Description Records lesson completion; may cascade to module, course, and program progress for the authenticated user. Learners must meet sequential prerequisites; staff bypass checks.
// @Tags lessons
// @Param id path int true "Lesson ID"
// @Success 200 {object} domain.Response
// @Failure 403 {object} domain.ErrorResponse
// @Router /api/v1/lessons/{id}/complete [post]
func (h *Handler) CompleteLesson(c *fiber.Ctx) error {
	id, err := strconv.ParseInt(c.Params("id"), 10, 64)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid lesson id",
			Error:   err.Error(),
		})
	}
	les, err := h.lessonSvc.GetByID(c.Context(), id)
	if err != nil {
		if errors.Is(err, lessons.ErrLessonNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Lesson not found",
				Error:   err.Error(),
			})
		}
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to load lesson",
			Error:   err.Error(),
		})
	}
	role := c.Locals("role").(domain.Role)
	if role.IsCustomerLearnerRole() && !les.VisibleToLearners() {
		return c.Status(fiber.StatusForbidden).JSON(domain.ErrorResponse{
			Message: "Only published lessons can be completed",
			Error:   "LESSON_NOT_PUBLISHED",
		})
	}
	uid := c.Locals("user_id").(int64)
	if role.UsesLMSSequentialGating() {
		ok, reason, err := h.lmsProgressSvc.CanAccessLesson(c.Context(), uid, id)
		if err != nil {
			return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
				Message: "Failed to verify lesson access",
				Error:   err.Error(),
			})
		}
		if !ok {
			return c.Status(fiber.StatusForbidden).JSON(domain.ErrorResponse{
				Message: reason,
				Error:   "LMS_PREREQUISITE_NOT_MET",
			})
		}
	}
	if err := h.lmsProgressSvc.CompleteLessonForUser(c.Context(), uid, id); err != nil {
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to record lesson progress",
			Error:   err.Error(),
		})
	}
	return c.JSON(domain.Response{
		Message:    "Lesson marked complete",
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}