package handlers

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

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

// CreateExamPrepModule godoc
// @Summary Create exam-prep module
// @Tags exam-prep
// @Param unitId path int true "Unit ID"
// @Param body body domain.CreateExamPrepModuleInput true "Module"
// @Router /api/v1/exam-prep/units/{unitId}/modules [post]
func (h *Handler) CreateExamPrepModule(c *fiber.Ctx) error {
	unitID, err := strconv.ParseInt(c.Params("unitId"), 10, 64)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid unit id",
			Error:   err.Error(),
		})
	}
	var req domain.CreateExamPrepModuleInput
	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.CreateModule(c.Context(), unitID, 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 create module",
			Error:   err.Error(),
		})
	}
	return c.Status(fiber.StatusCreated).JSON(domain.Response{
		Message:    "Module created successfully",
		Data:       out,
		Success:    true,
		StatusCode: fiber.StatusCreated,
	})
}

// ListExamPrepModulesByUnit godoc
// @Summary List exam-prep modules for a unit
// @Tags exam-prep
// @Param unitId path int true "Unit ID"
// @Router /api/v1/exam-prep/units/{unitId}/modules [get]
func (h *Handler) ListExamPrepModulesByUnit(c *fiber.Ctx) error {
	unitID, err := strconv.ParseInt(c.Params("unitId"), 10, 64)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid unit id",
			Error:   err.Error(),
		})
	}
	limit, _ := strconv.Atoi(c.Query("limit", "20"))
	offset, _ := strconv.Atoi(c.Query("offset", "0"))
	items, total, err := h.examPrepSvc.ListModulesByUnit(c.Context(), unitID, int32(limit), int32(offset))
	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 list modules",
			Error:   err.Error(),
		})
	}
	if err := h.applyExamPrepAccessModules(c.Context(), c, items); err != nil {
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to build module list",
			Error:   err.Error(),
		})
	}
	return c.JSON(domain.Response{
		Message: "Modules retrieved successfully",
		Data: fiber.Map{
			"modules":     items,
			"total_count": total,
			"limit":       limit,
			"offset":      offset,
		},
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// ReorderExamPrepModulesInUnit godoc
// @Summary Reorder modules within a unit
// @Tags exam-prep
// @Param unitId path int true "Unit ID"
// @Param body body domain.ReorderIDsRequest true "ordered_ids"
// @Router /api/v1/exam-prep/units/{unitId}/modules/reorder [put]
func (h *Handler) ReorderExamPrepModulesInUnit(c *fiber.Ctx) error {
	unitID, err := strconv.ParseInt(c.Params("unitId"), 10, 64)
	if err != nil {
		return c.Status(fiber.StatusBadRequest).JSON(domain.ErrorResponse{
			Message: "Invalid unit 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 modules)",
			Error:   "missing ordered_ids",
		})
	}
	if err := h.examPrepSvc.ReorderModulesInUnit(c.Context(), unitID, req.OrderedIDs); err != nil {
		if errors.Is(err, examprep.ErrUnitNotFound) {
			return c.Status(fiber.StatusNotFound).JSON(domain.ErrorResponse{
				Message: "Unit 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 modules",
			Error:   err.Error(),
		})
	}
	return c.JSON(domain.Response{
		Message:    "Modules reordered successfully",
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// GetExamPrepModuleByID godoc
// @Summary Get exam-prep module by ID
// @Tags exam-prep
// @Router /api/v1/exam-prep/modules/{id} [get]
func (h *Handler) GetExamPrepModuleByID(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 module id",
			Error:   err.Error(),
		})
	}
	out, err := h.examPrepSvc.GetModuleByID(c.Context(), id)
	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 get module",
			Error:   err.Error(),
		})
	}
	if err := h.applyExamPrepAccessModule(c.Context(), c, &out); err != nil {
		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{
			Message: "Failed to build module",
			Error:   err.Error(),
		})
	}
	return c.JSON(domain.Response{
		Message:    "Module retrieved successfully",
		Data:       out,
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// UpdateExamPrepModule godoc
// @Summary Update exam-prep module
// @Tags exam-prep
// @Router /api/v1/exam-prep/modules/{id} [put]
func (h *Handler) UpdateExamPrepModule(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 module id",
			Error:   err.Error(),
		})
	}
	var req domain.UpdateExamPrepModuleInput
	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.UpdateModule(c.Context(), id, 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 update module",
			Error:   err.Error(),
		})
	}
	return c.JSON(domain.Response{
		Message:    "Module updated successfully",
		Data:       out,
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}

// DeleteExamPrepModule godoc
// @Summary Delete exam-prep module
// @Tags exam-prep
// @Router /api/v1/exam-prep/modules/{id} [delete]
func (h *Handler) DeleteExamPrepModule(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 module id",
			Error:   err.Error(),
		})
	}
	if err := h.examPrepSvc.DeleteModule(c.Context(), id); 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 delete module",
			Error:   err.Error(),
		})
	}
	return c.JSON(domain.Response{
		Message:    "Module deleted successfully",
		Success:    true,
		StatusCode: fiber.StatusOK,
	})
}