script.liquid

{% assign metafield_namespace = options.metafield_namespace__required %}
{% assign metafield_key = options.metafield_key__required %}

{% assign customer = shop.customers[review.reviewer.external_id] %}

{% if event.preview %}
  {% capture customer_json %}
    {
      "admin_graphql_api_id": "gid://shopify/Customer/1234567890",
      "metafields": [
        {
          "namespace": {{ metafield_namespace | json }},
          "key": {{ metafield_key | json }},
          "value": 0
        }
      ]
    }
  {% endcapture %}

  {% assign customer = customer_json | parse_json %}
{% endif %}

{% if customer %}
  {% assign current_review_count = customer.metafields[metafield_namespace][metafield_key].value | default: 0 %}
  {% assign next_review_count = current_review_count | plus: 1 %}
  {% assign next_review_count_as_string = next_review_count | append: "" %}
  {% assign tag = options.tags_to_apply_for_review_counts__keyval[next_review_count_as_string] %}

  {% action "shopify" %}
    mutation {
      metafieldsSet(
        metafields: [
          {
            ownerId: {{ customer.admin_graphql_api_id | json }}
            namespace: {{ metafield_namespace | json }}
            key: {{ metafield_key | json }}
            value: {{ next_review_count_as_string | json }}
            type: "number_integer"
          }
        ]
      ) {
        metafields {
          id
          namespace
          key
          type
          value
          owner {
            ... on Customer {
              id
            }
          }
        }
        userErrors {
          code
          field
          message
        }
      }
      {% if tag != blank %}
        tagsAdd(
          id: {{ customer.admin_graphql_api_id | json }}
          tags: {{ tag | json }}
        ) {
          node {
            id
          }
          userErrors {
            field
            message
          }
        }
      {% endif %}
    }
  {% endaction %}
{% endif %}