First-class Solr fields and documents (rough draft)

gistfile1.cs

    public class SolrDocument {
        public readonly IReadOnlyCollection<SolrDocumentOrField> Fields;
        public readonly double? Boost;

        public SolrDocument(IReadOnlyCollection<SolrDocumentOrField> fields, double? boost) {
            Fields = fields;
            Boost = boost;
        }
    }

    public class SolrField {
        public readonly string Name;
        public readonly string Value;
        public readonly double? Boost;

        public SolrField(string name, string value, double? boost) {
            Name = name;
            Value = value;
            Boost = boost;
        }
    }

    public abstract class SolrDocumentOrField {
        private SolrDocumentOrField() {}

        public abstract T Match<T>(Func<SolrDocument, T> document, Func<SolrField, T> field);

        private class SolrDocumentOrField_Document: SolrDocumentOrField {
            private readonly SolrDocument document;

            public SolrDocumentOrField_Document(SolrDocument document) {
                this.document = document;
            }

            public override T Match<T>(Func<SolrDocument, T> document, Func<SolrField, T> field) {
                return document(this.document);
            }
        }

        private class SolrDocumentOrField_Field: SolrDocumentOrField {
            private readonly SolrField field;

            public SolrDocumentOrField_Field(SolrField field) {
                this.field = field;
            }

            public override T Match<T>(Func<SolrDocument, T> document, Func<SolrField, T> field) {
                return field(this.field);
            }
        }

        public static SolrDocumentOrField Document(SolrDocument document) {
            return new SolrDocumentOrField_Document(document);
        }

        public static SolrDocumentOrField Field(SolrField field) {
            return new SolrDocumentOrField_Field(field);
        }
    }