package handler

import (
	"net/http"
	"strconv"

	"github.com/gin-gonic/gin"

	"github.com/user-management-system/internal/auth"
	"github.com/user-management-system/internal/domain"
	"github.com/user-management-system/internal/service"
)

// UserHandler handles user management requests
type UserHandler struct {
	userService *service.UserService
}

// NewUserHandler creates a new UserHandler
func NewUserHandler(userService *service.UserService) *UserHandler {
	return &UserHandler{userService: userService}
}

func (h *UserHandler) CreateUser(c *gin.Context) {
	var req struct {
		Username string `json:"username" binding:"required"`
		Email    string `json:"email"`
		Password string `json:"password"`
		Nickname string `json:"nickname"`
	}

	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	user := &domain.User{
		Username: req.Username,
		Email:    domain.StrPtr(req.Email),
		Nickname: req.Nickname,
		Status:   domain.UserStatusActive,
	}

	if req.Password != "" {
		hashed, err := auth.HashPassword(req.Password)
		if err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to hash password"})
			return
		}
		user.Password = hashed
	}

	if err := h.userService.Create(c.Request.Context(), user); err != nil {
		handleError(c, err)
		return
	}

	c.JSON(http.StatusCreated, gin.H{
		"code":    0,
		"message": "success",
		"data":    toUserResponse(user),
	})
}

func (h *UserHandler) ListUsers(c *gin.Context) {
	cursor := c.Query("cursor")
	sizeStr := c.DefaultQuery("size", "")

	// Use cursor-based pagination when cursor is provided
	if cursor != "" || sizeStr != "" {
		var req service.ListCursorRequest
		if err := c.ShouldBindQuery(&req); err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}
		result, err := h.userService.ListCursor(c.Request.Context(), &req)
		if err != nil {
			handleError(c, err)
			return
		}
		c.JSON(http.StatusOK, gin.H{
			"code":    0,
			"message": "success",
			"data":    result,
		})
		return
	}

	// Fallback to legacy offset-based pagination
	offset, _ := strconv.ParseInt(c.DefaultQuery("offset", "0"), 10, 64)
	limit, _ := strconv.ParseInt(c.DefaultQuery("limit", "20"), 10, 64)

	users, total, err := h.userService.List(c.Request.Context(), int(offset), int(limit))
	if err != nil {
		handleError(c, err)
		return
	}

	userResponses := make([]*UserResponse, len(users))
	for i, u := range users {
		userResponses[i] = toUserResponse(u)
	}

	c.JSON(http.StatusOK, gin.H{
		"users":  userResponses,
		"total":  total,
		"offset": offset,
		"limit":  limit,
	})
}

func (h *UserHandler) GetUser(c *gin.Context) {
	id, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid user id"})
		return
	}

	user, err := h.userService.GetByID(c.Request.Context(), id)
	if err != nil {
		handleError(c, err)
		return
	}

	c.JSON(http.StatusOK, toUserResponse(user))
}

func (h *UserHandler) UpdateUser(c *gin.Context) {
	id, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid user id"})
		return
	}

	var req struct {
		Email    *string `json:"email"`
		Nickname *string `json:"nickname"`
	}

	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	user, err := h.userService.GetByID(c.Request.Context(), id)
	if err != nil {
		handleError(c, err)
		return
	}

	if req.Email != nil {
		user.Email = req.Email
	}
	if req.Nickname != nil {
		user.Nickname = *req.Nickname
	}

	if err := h.userService.Update(c.Request.Context(), user); err != nil {
		handleError(c, err)
		return
	}

	c.JSON(http.StatusOK, toUserResponse(user))
}

func (h *UserHandler) DeleteUser(c *gin.Context) {
	id, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid user id"})
		return
	}

	if err := h.userService.Delete(c.Request.Context(), id); err != nil {
		handleError(c, err)
		return
	}

	c.JSON(http.StatusOK, gin.H{"message": "user deleted"})
}

func (h *UserHandler) UpdatePassword(c *gin.Context) {
	id, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid user id"})
		return
	}

	var req struct {
		OldPassword string `json:"old_password" binding:"required"`
		NewPassword string `json:"new_password" binding:"required"`
	}

	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	if err := h.userService.ChangePassword(c.Request.Context(), id, req.OldPassword, req.NewPassword); err != nil {
		handleError(c, err)
		return
	}

	c.JSON(http.StatusOK, gin.H{"message": "密码修改成功"})
}

func (h *UserHandler) UpdateUserStatus(c *gin.Context) {
	id, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid user id"})
		return
	}

	var req struct {
		Status string `json:"status" binding:"required"`
	}

	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	var status domain.UserStatus
	switch req.Status {
	case "active", "1":
		status = domain.UserStatusActive
	case "inactive", "0":
		status = domain.UserStatusInactive
	case "locked", "2":
		status = domain.UserStatusLocked
	case "disabled", "3":
		status = domain.UserStatusDisabled
	default:
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid status"})
		return
	}

	if err := h.userService.UpdateStatus(c.Request.Context(), id, status); err != nil {
		handleError(c, err)
		return
	}

	c.JSON(http.StatusOK, gin.H{"message": "status updated"})
}

func (h *UserHandler) GetUserRoles(c *gin.Context) {
	id, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "invalid user id"})
		return
	}

	// Authorization: only self or admin can view user roles
	currentUserID := c.GetInt64("user_id")
	isAdmin := false
	if roles, ok := c.Get("user_roles"); ok {
		for _, role := range roles.([]*domain.Role) {
			if role.Code == "admin" {
				isAdmin = true
				break
			}
		}
	}
	if currentUserID != id && !isAdmin {
		c.JSON(http.StatusForbidden, gin.H{"code": 403, "message": "permission denied"})
		return
	}

	roles, err := h.userService.GetUserRoles(c.Request.Context(), id)
	if err != nil {
		handleError(c, err)
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"code":    0,
		"message": "success",
		"data":    roles,
	})
}

func (h *UserHandler) AssignRoles(c *gin.Context) {
	id, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "invalid user id"})
		return
	}

	var req struct {
		RoleIDs []int64 `json:"role_ids" binding:"required"`
	}

	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": err.Error()})
		return
	}

	if err := h.userService.AssignRoles(c.Request.Context(), id, req.RoleIDs); err != nil {
		handleError(c, err)
		return
	}

	c.JSON(http.StatusOK, gin.H{"code": 0, "message": "角色分配成功"})
}

func (h *UserHandler) BatchUpdateStatus(c *gin.Context) {
	var req service.BatchUpdateStatusRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": err.Error()})
		return
	}

	count, err := h.userService.BatchUpdateStatus(c.Request.Context(), &req)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "批量更新失败"})
		return
	}

	c.JSON(http.StatusOK, gin.H{"code": 0, "message": "更新成功", "data": gin.H{"count": count}})
}

func (h *UserHandler) BatchDelete(c *gin.Context) {
	var req service.BatchDeleteRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": err.Error()})
		return
	}

	count, err := h.userService.BatchDelete(c.Request.Context(), &req)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"code": 500, "message": "批量删除失败"})
		return
	}

	c.JSON(http.StatusOK, gin.H{"code": 0, "message": "删除成功", "data": gin.H{"count": count}})
}

func (h *UserHandler) ListAdmins(c *gin.Context) {
	admins, err := h.userService.ListAdmins(c.Request.Context())
	if err != nil {
		handleError(c, err)
		return
	}

	adminResponses := make([]*UserResponse, len(admins))
	for i, u := range admins {
		adminResponses[i] = toUserResponse(u)
	}

	c.JSON(http.StatusOK, gin.H{"code": 0, "message": "success", "data": adminResponses})
}

func (h *UserHandler) CreateAdmin(c *gin.Context) {
	var req struct {
		Username string `json:"username" binding:"required"`
		Password string `json:"password" binding:"required"`
		Email   string `json:"email"`
		Nickname string `json:"nickname"`
	}

	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": err.Error()})
		return
	}

	adminReq := &service.CreateAdminRequest{
		Username: req.Username,
		Password: req.Password,
		Email:   req.Email,
		Nickname: req.Nickname,
	}

	admin, err := h.userService.CreateAdmin(c.Request.Context(), adminReq)
	if err != nil {
		handleError(c, err)
		return
	}

	c.JSON(http.StatusCreated, gin.H{"code": 0, "message": "管理员创建成功", "data": toUserResponse(admin)})
}

func (h *UserHandler) DeleteAdmin(c *gin.Context) {
	id, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"code": 400, "message": "invalid user id"})
		return
	}

	currentUserID := c.GetInt64("user_id")
	if err := h.userService.DeleteAdmin(c.Request.Context(), id, currentUserID); err != nil {
		handleError(c, err)
		return
	}

	c.JSON(http.StatusOK, gin.H{"code": 0, "message": "管理员已移除"})
}

type UserResponse struct {
	ID       int64  `json:"id"`
	Username string `json:"username"`
	Email    string `json:"email,omitempty"`
	Nickname string `json:"nickname,omitempty"`
	Status   string `json:"status"`
}

func toUserResponse(u *domain.User) *UserResponse {
	email := ""
	if u.Email != nil {
		email = *u.Email
	}
	return &UserResponse{
		ID:       u.ID,
		Username: u.Username,
		Email:    email,
		Nickname: u.Nickname,
		Status:   strconv.FormatInt(int64(u.Status), 10),
	}
}
