package handlers

import (
	"Yimaru-Backend/internal/domain"
	"Yimaru-Backend/internal/services/examprep"
	"errors"
	"strconv"

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

// CreateExamPrepLesson godoc
// @Summary Create exam-prep lesson (under a unit module)
// @Tags exam-prep
// @Param moduleId path int true "Exam prep unit module ID"
// @Param body body domain.CreateExamPrepLessonInput true "Lesson"
// @Router /api/v1/exam-prep/modules/{moduleId}/lessons [post]
func (h *Handler) CreateExamPrepLesson(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.CreateExamPrepLessonInput
	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.examPrepSvc.CreateLesson(c.Context(), moduleID, req)
	if err != nil {
		if errors.Is(err, examprep.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(),
		})
	}
	return c.Status(fiber.StatusCreated).JSON(domain.Response{
		Message:    "Lesson created successfully",
		Data:       les,
		Success:    true,
		StatusCode: fiber.StatusCreated,
	})
}

// ListExamPrepLessonsByUnitModule godoc
// @Summary List exam-prep lessons for a unit module
// @Tags exam-prep
// @Param moduleId path int true "Exam prep unit module ID"
// @Param limit query int false "Page size" default(20)
// @Param offset query int false "Offset" default(0)
// @Router /api/v1/exam-prep/modules/{moduleId}/lessons [get]
func (h *Handler) ListExamPrepLessonsByUnitModule(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"))
	items, total, err := h.examPrepSvc.ListLessonsByUnitModule(c.Context(), moduleID, int32(limit), int32(offset))
	if err != nil {
		if errors.Is(err, examprep.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(),
		})
	}
	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,
	})
}

// ReorderExamPrepLessonsInUnitModule godoc
// @Summary Reorder lessons within an exam-prep unit module
// @Tags exam-prep
// @Router /api/v1/exam-prep/modules/{moduleId}/lessons/reorder [put]
func (h *Handler) ReorderExamPrepLessonsInUnitModule(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.ReorderIDsRequest
	if err := c.BodyParser(&req); err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid request body",
			Error:   err.Error(),
		})
	}
	if req.OrderedIDs == nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "ordered_ids is required (use an empty array if there are no lessons)",
			Error:   "missing ordered_ids",
		})
	}
	if err := h.examPrepSvc.ReorderLessonsInUnitModule(c.Context(), moduleID, req.OrderedIDs); err != nil {
		if errors.Is(err, examprep.ErrModuleNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Module not found",
				Error:   err.Error(),
			})
		}
		if errors.Is(err, domain.ErrReorderInvalidIDSet) {
			return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
				Message: err.Error(),
				Error:   "INVALID_REORDER",
			})
		}
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to reorder lessons",
			Error:   err.Error(),
		})
	}
	return c.JSON(domain.Response{
		Message:    "Lessons reordered successfully",
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// GetExamPrepLessonByID godoc
// @Summary Get exam-prep lesson by ID
// @Tags exam-prep
// @Router /api/v1/exam-prep/lessons/{id} [get]
func (h *Handler) GetExamPrepLessonByID(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.examPrepSvc.GetLessonByID(c.Context(), id)
	if err != nil {
		if errors.Is(err, examprep.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 get lesson",
			Error:   err.Error(),
		})
	}
	return c.JSON(domain.Response{
		Message:    "Lesson retrieved successfully",
		Data:       les,
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// UpdateExamPrepLesson godoc
// @Summary Update exam-prep lesson
// @Tags exam-prep
// @Router /api/v1/exam-prep/lessons/{id} [put]
func (h *Handler) UpdateExamPrepLesson(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.UpdateExamPrepLessonInput
	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.examPrepSvc.UpdateLesson(c.Context(), id, req)
	if err != nil {
		if errors.Is(err, examprep.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(),
		})
	}
	return c.JSON(domain.Response{
		Message:    "Lesson updated successfully",
		Data:       les,
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// DeleteExamPrepLesson godoc
// @Summary Delete exam-prep lesson
// @Tags exam-prep
// @Router /api/v1/exam-prep/lessons/{id} [delete]
func (h *Handler) DeleteExamPrepLesson(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.examPrepSvc.DeleteLesson(c.Context(), id); err != nil {
		if errors.Is(err, examprep.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(),
		})
	}
	return c.JSON(domain.Response{
		Message:    "Lesson deleted successfully",
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}