class Whatsapp::FacebookApiClient
  BASE_URI = 'https://graph.facebook.com'.freeze
  # Base webhook fields resent on every subscribe so Meta won't reset to defaults. `calls` is added by callers only when voice is enabled.
  WEBHOOK_DEFAULT_FIELDS = %w[messages smb_message_echoes].freeze

  def initialize(access_token = nil)
    @access_token = access_token
    @api_version = GlobalConfigService.load('WHATSAPP_API_VERSION', 'v22.0')
  end

  def exchange_code_for_token(code)
    response = HTTParty.get(
      "#{BASE_URI}/#{@api_version}/oauth/access_token",
      query: {
        client_id: GlobalConfigService.load('WHATSAPP_APP_ID', ''),
        client_secret: GlobalConfigService.load('WHATSAPP_APP_SECRET', ''),
        code: code
      }
    )

    handle_response(response, 'Token exchange failed')
  end

  def fetch_phone_numbers(waba_id)
    response = HTTParty.get(
      "#{BASE_URI}/#{@api_version}/#{waba_id}/phone_numbers",
      query: { access_token: @access_token }
    )

    handle_response(response, 'WABA phone numbers fetch failed')
  end

  def debug_token(input_token)
    response = HTTParty.get(
      "#{BASE_URI}/#{@api_version}/debug_token",
      query: {
        input_token: input_token,
        access_token: build_app_access_token
      }
    )

    handle_response(response, 'Token validation failed')
  end

  def register_phone_number(phone_number_id, pin)
    response = HTTParty.post(
      "#{BASE_URI}/#{@api_version}/#{phone_number_id}/register",
      headers: request_headers,
      body: { messaging_product: 'whatsapp', pin: pin.to_s }.to_json
    )

    handle_response(response, 'Phone registration failed')
  end

  def phone_number_verified?(phone_number_id)
    response = HTTParty.get(
      "#{BASE_URI}/#{@api_version}/#{phone_number_id}",
      headers: request_headers
    )

    data = handle_response(response, 'Phone status check failed')
    data['code_verification_status'] == 'VERIFIED'
  end

  def subscribe_phone_number_webhook(waba_id, phone_number_id, callback_url, verify_token, subscribed_fields: nil)
    # Subscribe app to WABA first — Meta requires it before any callback override (issue #13097).
    # subscribed_fields (incl. `calls` when voice is enabled) is declared here; the phone-level POST has no such field.
    subscribe_app_to_waba(waba_id, subscribed_fields: subscribed_fields || WEBHOOK_DEFAULT_FIELDS)

    # Phone-level override takes precedence over WABA-level, so numbers on one WABA can route to different URLs.
    override_phone_number_callback(phone_number_id, callback_url, verify_token)
  end

  def subscribe_app_to_waba(waba_id, subscribed_fields: WEBHOOK_DEFAULT_FIELDS)
    response = HTTParty.post(
      "#{BASE_URI}/#{@api_version}/#{waba_id}/subscribed_apps",
      headers: request_headers,
      body: { subscribed_fields: subscribed_fields }.to_json
    )

    handle_response(response, 'App subscription to WABA failed')
  end

  def override_phone_number_callback(phone_number_id, callback_url, verify_token)
    response = HTTParty.post(
      "#{BASE_URI}/#{@api_version}/#{phone_number_id}",
      headers: request_headers,
      body: {
        webhook_configuration: {
          override_callback_uri: callback_url,
          verify_token: verify_token
        }
      }.to_json
    )

    handle_response(response, 'Phone number webhook callback override failed')
  end

  def clear_phone_number_callback_override(phone_number_id)
    response = HTTParty.post(
      "#{BASE_URI}/#{@api_version}/#{phone_number_id}",
      headers: request_headers,
      body: {
        webhook_configuration: {
          override_callback_uri: ''
        }
      }.to_json
    )

    handle_response(response, 'Phone number webhook callback clear failed')
  end

  # Fully removes this app's WABA subscription (last inbox deleted) so Meta stops delivering webhooks.
  def unsubscribe_app_from_waba(waba_id)
    response = HTTParty.delete(
      "#{BASE_URI}/#{@api_version}/#{waba_id}/subscribed_apps",
      headers: request_headers
    )

    handle_response(response, 'WABA app unsubscription failed')
  end

  private

  def request_headers
    {
      'Authorization' => "Bearer #{@access_token}",
      'Content-Type' => 'application/json'
    }
  end

  def build_app_access_token
    app_id = GlobalConfigService.load('WHATSAPP_APP_ID', '')
    app_secret = GlobalConfigService.load('WHATSAPP_APP_SECRET', '')
    "#{app_id}|#{app_secret}"
  end

  def handle_response(response, error_message)
    raise "#{error_message}: #{response.body}" unless response.success?

    response.parsed_response
  end
end