package handlers

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

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

// CreateExamPrepUnit godoc
// @Summary Create exam-prep unit
// @Description Unit under a catalog course (e.g. chapter title). Optional sort_order assigns position within that catalog course (siblings at or after that index are shifted); omit to append after the current highest sort_order in the catalog course.
// @Tags exam-prep
// @Accept json
// @Produce json
// @Param catalogCourseId path int true "Catalog course ID"
// @Param body body domain.CreateExamPrepUnitInput true "Unit"
// @Success 201 {object} domain.Response
// @Router /api/v1/exam-prep/catalog-courses/{catalogCourseId}/units [post]
func (h *Handler) CreateExamPrepUnit(c *fiber.Ctx) error {
	catalogCourseID, err := strconv.ParseInt(c.Params("catalogCourseId"), 10, 64)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid catalog course id",
			Error:   err.Error(),
		})
	}
	var req domain.CreateExamPrepUnitInput
	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),
		})
	}
	out, err := h.examPrepSvc.CreateUnit(c.Context(), catalogCourseID, req)
	if err != nil {
		if errors.Is(err, examprep.ErrCatalogCourseNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Catalog course not found",
				Error:   err.Error(),
			})
		}
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to create unit",
			Error:   err.Error(),
		})
	}
	return c.Status(fiber.StatusCreated).JSON(domain.Response{
		Message:    "Unit created successfully",
		Data:       out,
		Success:    true,
		StatusCode: fiber.StatusCreated,
	})
}

// ListExamPrepUnitsByCatalogCourse godoc
// @Summary List exam-prep units for a catalog course
// @Tags exam-prep
// @Param catalogCourseId path int true "Catalog course ID"
// @Param limit query int false "Page size" default(20)
// @Param offset query int false "Offset" default(0)
// @Success 200 {object} domain.Response
// @Router /api/v1/exam-prep/catalog-courses/{catalogCourseId}/units [get]
func (h *Handler) ListExamPrepUnitsByCatalogCourse(c *fiber.Ctx) error {
	catalogCourseID, err := strconv.ParseInt(c.Params("catalogCourseId"), 10, 64)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid catalog course id",
			Error:   err.Error(),
		})
	}
	limit, _ := strconv.Atoi(c.Query("limit", "20"))
	offset, _ := strconv.Atoi(c.Query("offset", "0"))
	items, total, err := h.examPrepSvc.ListUnitsByCatalogCourse(c.Context(), catalogCourseID, int32(limit), int32(offset))
	if err != nil {
		if errors.Is(err, examprep.ErrCatalogCourseNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Catalog course not found",
				Error:   err.Error(),
			})
		}
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to list units",
			Error:   err.Error(),
		})
	}
	return c.JSON(domain.Response{
		Message: "Units retrieved successfully",
		Data: fiber.Map{
			"units":       items,
			"total_count": total,
			"limit":       limit,
			"offset":      offset,
		},
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// ReorderExamPrepUnitsInCatalogCourse godoc
// @Summary Reorder units within a catalog course
// @Tags exam-prep
// @Param catalogCourseId path int true "Catalog course ID"
// @Param body body domain.ReorderIDsRequest true "ordered_ids: every unit id in this catalog course, new order"
// @Router /api/v1/exam-prep/catalog-courses/{catalogCourseId}/units/reorder [put]
func (h *Handler) ReorderExamPrepUnitsInCatalogCourse(c *fiber.Ctx) error {
	catalogCourseID, err := strconv.ParseInt(c.Params("catalogCourseId"), 10, 64)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid catalog course 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 units)",
			Error:   "missing ordered_ids",
		})
	}
	if err := h.examPrepSvc.ReorderUnitsInCatalogCourse(c.Context(), catalogCourseID, req.OrderedIDs); err != nil {
		if errors.Is(err, examprep.ErrCatalogCourseNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Catalog course 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 units",
			Error:   err.Error(),
		})
	}
	return c.JSON(domain.Response{
		Message:    "Units reordered successfully",
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// GetExamPrepUnitByID godoc
// @Summary Get exam-prep unit by ID
// @Tags exam-prep
// @Param id path int true "Unit ID"
// @Router /api/v1/exam-prep/units/{id} [get]
func (h *Handler) GetExamPrepUnitByID(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 unit id",
			Error:   err.Error(),
		})
	}
	out, err := h.examPrepSvc.GetUnitByID(c.Context(), id)
	if err != nil {
		if errors.Is(err, examprep.ErrUnitNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Unit not found",
				Error:   err.Error(),
			})
		}
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to get unit",
			Error:   err.Error(),
		})
	}
	return c.JSON(domain.Response{
		Message:    "Unit retrieved successfully",
		Data:       out,
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// UpdateExamPrepUnit godoc
// @Summary Update exam-prep unit
// @Tags exam-prep
// @Param id path int true "Unit ID"
// @Param body body domain.UpdateExamPrepUnitInput true "Fields to update"
// @Router /api/v1/exam-prep/units/{id} [put]
func (h *Handler) UpdateExamPrepUnit(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 unit id",
			Error:   err.Error(),
		})
	}
	var req domain.UpdateExamPrepUnitInput
	if err := c.BodyParser(&req); err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid request body",
			Error:   err.Error(),
		})
	}
	out, err := h.examPrepSvc.UpdateUnit(c.Context(), id, req)
	if err != nil {
		if errors.Is(err, examprep.ErrUnitNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Unit not found",
				Error:   err.Error(),
			})
		}
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to update unit",
			Error:   err.Error(),
		})
	}
	return c.JSON(domain.Response{
		Message:    "Unit updated successfully",
		Data:       out,
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// DeleteExamPrepUnit godoc
// @Summary Delete exam-prep unit
// @Tags exam-prep
// @Param id path int true "Unit ID"
// @Router /api/v1/exam-prep/units/{id} [delete]
func (h *Handler) DeleteExamPrepUnit(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 unit id",
			Error:   err.Error(),
		})
	}
	if err := h.examPrepSvc.DeleteUnit(c.Context(), id); err != nil {
		if errors.Is(err, examprep.ErrUnitNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Unit not found",
				Error:   err.Error(),
			})
		}
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to delete unit",
			Error:   err.Error(),
		})
	}
	return c.JSON(domain.Response{
		Message:    "Unit deleted successfully",
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}