budget/app/controllers/users_controller.rb

class UsersController < ApplicationController
  require_unregistered_user only: %i[new create]

  before_action :set_user, only: %i[ show edit update destroy ]

  # GET /users or /users.json
  def index
    @users = User.all
  end

  # GET /users/1 or /users/1.json
  def show
  end

  # GET /users/new
  def new
    @user = User.new
  end

  # GET /users/1/edit
  def edit
  end

  # POST /users or /users.json
  def create
    @user = User.new(user_params)

    respond_to do |format|
      if ENV["REGISTRATION_ALLOWED"].blank?
        format.html { redirect_to new_session_url, alert: "Registration disabled." }
        format.json { render json: @user.errors, status: :unprocessable_entity }
      elsif @user.save
        @session = Session.new(session_params).save
        session[:current_user_id] = @session.user_id

        format.html { redirect_to user_url(@user), notice: "User was successfully created." }
        format.json { render :show, status: :created, location: @user }
      else
        format.html { render :new, status: :unprocessable_entity }
        format.json { render json: @user.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /users/1 or /users/1.json
  def update
    respond_to do |format|
      if @user.update(user_params)
        format.html { redirect_to user_url(@user), notice: "User was successfully updated." }
        format.json { render :show, status: :ok, location: @user }
      else
        format.html { render :edit, status: :unprocessable_entity }
        format.json { render json: @user.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /users/1 or /users/1.json
  def destroy
    @user.destroy!

    respond_to do |format|
      format.html { redirect_to users_url, notice: "User was successfully destroyed." }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_user
      @user = User.find(params[:id])
    end

    # Only allow a list of trusted parameters through.
    def user_params
      params.require(:user).permit(:email, :password, :password_confirmation)
    end

    def session_params
      user_params.slice(:email, :password)
    end
end