# frozen_string_literal: true

require 'resolv'

class ClientsController < ApplicationController
  before_action :parse_api_key_header, except: [:show_public_ipv4]
  before_action :authenticate_client, except: [:show_public_ipv4]
  before_action :authorize_perm_r, only: [:show_ipv4]
  before_action :authorize_perm_w, only: %i[update_ipv4 destroy_ipv4]
  before_action :authorize_perm_x, only: %i[create update index show destroy]
  before_action :client_authorized, except: [:show_public_ipv4]

  # URL Methods
  # POST /admin/client
  def create
    client_params = params.permit(:name, :description, :permission, :public_ip)
    return head(405) unless client_params.key?(:name)

    client = Client.find_by name: client_params[:name]
    status_code = client ? 200 : 201

    # create new client or update existing
    if client.nil?
      client ||= Client.new_client(client_params)
    else
      # return 406 if request is trying to remove perm_x from last admin account to prevent lockout
      # TODO: move this into the model (update)
      return head(406) if removing_last_admin?(client, client_params)

      client.update_client(client_params)
    end

    api_key = client.gen_api_key
    client.save
    json_response({ name: client.name, api_key: api_key }, status_code)
  end

  # PUT /admin/client
  def update
    client_params = params.permit(:name, :description, :permission, :public_ip)
    return head(405) unless client_params.key?(:name)

    client = Client.find_by name: client_params[:name]
    return head(404) unless client

    # return 406 if request is trying to remove perm_x from last admin account to prevent lockout
    # TODO: move this into the model (update)
    return head(406) if removing_last_admin?(client, client_params)

    # update client
    client.update_client(client_params)

    client.save
    head(200)
  end

  # GET /admin/clients
  def index
    clients = []
    Client.find_each do |client|
      clients.append admin_read_object(client)
    end
    json_response(clients)
  end

  # GET /admin/clients/:name
  def show
    # return 404 if requested client does not exist
    client = Client.find_by name: params[:name]
    return head(404) if client.nil?

    json_response(admin_read_object(client))
  end

  # DELETE /admin/clients/:name
  def destroy
    client = Client.find_by(name: params[:name])

    # return 404 if requested client does not exist
    return head(404) unless client

    # return 406 if request is trying to remove last admin account to prevent lockout
    # TODO: move this into the model (delete)
    return head(406) if client.admin? && Client.number_of_admins <= 1

    client.delete

    head(200)
  end

  # PUT /client
  def update_ipv4
    ipv4 = request_ip

    # return 406 if body with invalid ipv4 is present
    # TODO: move this into the model (update)
    return head(406) unless ipv4

    @requesting_client.ipv4 = ipv4
    @requesting_client.save
    json_response(client_read_object(@requesting_client))
  end

  # DELETE /client
  def destroy_ipv4
    prev_data = client_read_object(@requesting_client)
    @requesting_client.ipv4 = ''
    @requesting_client.save
    json_response(prev_data)
  end

  # GET /clients/:id
  def show_ipv4
    # return 404 if requested client does not exist
    client = Client.find_by name: params[:name]
    return head(404) if client.nil?

    json_response(client_read_object(client))
  end

  # GET /public/:id
  def show_public_ipv4
    # check if client exist and is public else return 401 (don't leak existence)
    client = Client.find_by name: params[:name]
    return head(401) if client.nil? || !client.public_ip

    json_response(client_read_object(client))
  end

  private

  # helper methods

  # respond with json object and status
  def json_response(object, status = :ok)
    render json: object, status: status
  end

  # checks if request is trying to remove the last admin
  def removing_last_admin?(client, params)
    return false unless params[:permission].is_a?(String)

    client.admin? && !Client.parse_perm_string(params[:permission])[:x] && Client.number_of_admins <= 1
  end

  def client_read_object(client)
    {
      name: client.name,
      ipv4: client.ipv4
    }
  end

  def admin_read_object(client)
    {
      name: client.name,
      description: client.description,
      permission: client.permission,
      public_ip: client.public_ip,
      ipv4: client.ipv4
    }
  end

  def request_ip
    ipv4_params = params.permit(:ipv4)
    if ipv4_params.key?(:ipv4)
      return nil unless ipv4_params[:ipv4].match(Resolv::IPv4::Regex)

      ipv4_params[:ipv4]
    else
      request.remote_ip
    end
  end

  # before_action methods

  # check if the api is valid and has the appropriate prefix
  def parse_api_key_header
    # TODO: move api_key checks and formatting to helper class
    # check if api key is present and can be split into 3 parts: <prefix>.<name_id>.<api_key>
    # NOTE: .compact is more for got measure than really necessary, but this ensures no nil values in the array
    api_key_header = request.headers[RynDNS::Application::API_KEY_HEADER].split('.').compact unless
      request.headers[RynDNS::Application::API_KEY_HEADER].nil?
    return head(401) if api_key_header.nil? || api_key_header.length < 3

    prefix, @name_id, @api_key = api_key_header
    # check if prefix matches (do this securely to prevent timing attacks on the prefix)
    return head(403) unless ActiveSupport::SecurityUtils.secure_compare(prefix,
                                                                        RynDNS::Application::API_KEY_PREFIX)
  end

  # authenticate the client with the supplied api key
  def authenticate_client
    # load the request client else return 403
    @requesting_client = Client.find_by name_id: @name_id
    return head(403) unless @requesting_client

    # compare api_key with hash value else return 403
    return head(403) unless @requesting_client.api_key == @api_key
  end

  # check if requesting client has read permission
  def authorize_perm_r
    @authorized = @requesting_client.read?
  end

  # check if requesting client has write permission
  def authorize_perm_w
    @authorized = @requesting_client.write?
  end

  # check if requesting client has admin permission
  def authorize_perm_x
    @authorized = @requesting_client.admin?
  end

  # check if request is authorized
  def client_authorized
    return head(403) unless @authorized
  end
end