alef-backend-java 0.16.21

// Custom serializer for sealed interface with unwrapped variants — emits
// the discriminator tag alongside the inner record's fields (flat object).
class {{ class_name }}Serializer extends StdSerializer<{{ class_name }}> {
    private static final com.fasterxml.jackson.databind.ObjectMapper MAPPER =
        new com.fasterxml.jackson.databind.ObjectMapper()
            .registerModule(new com.fasterxml.jackson.datatype.jdk8.Jdk8Module())
            .setPropertyNamingStrategy(com.fasterxml.jackson.databind.PropertyNamingStrategies.SNAKE_CASE)
            .setSerializationInclusion(com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL);

    {{ class_name }}Serializer() {
        super({{ class_name }}.class);
    }

    @Override
    public void serialize({{ class_name }} value, JsonGenerator gen, SerializerProvider provider)
            throws java.io.IOException {
        String tag;
        Object inner;
        {%- for variant in variants %}
        {% if loop.index0 > 0 %}else {% endif %}if (value instanceof {{ class_name }}.{{ variant.name }} v) {
            tag = "{{ variant.discriminator }}";
            {%- if variant.is_unit %}
            inner = null;
            {%- elif variant.is_tuple %}
            inner = v.value();
            {%- else %}
            inner = v;
            {%- endif %}
        }
        {%- endfor %}
        else {
            throw new com.fasterxml.jackson.databind.JsonMappingException(gen,
                "Unknown {{ class_name }} variant: " + value.getClass().getName());
        }

        gen.writeStartObject();
        gen.writeStringField("{{ tag_field }}", tag);
        if (inner != null) {
            com.fasterxml.jackson.databind.JsonNode tree = MAPPER.valueToTree(inner);
            if (tree.isObject()) {
                java.util.Iterator<java.util.Map.Entry<String, com.fasterxml.jackson.databind.JsonNode>> it =
                    tree.fields();
                while (it.hasNext()) {
                    java.util.Map.Entry<String, com.fasterxml.jackson.databind.JsonNode> e = it.next();
                    gen.writeFieldName(e.getKey());
                    gen.writeTree(e.getValue());
                }
            }
        }
        gen.writeEndObject();
    }
}