Collection.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace JSONstat.Models;

/// <summary>
/// A JSON-stat collection response: a set of referenced or embedded items.
/// Source: <c>../wiki/response-classes.md</c>.
/// </summary>
public sealed class Collection
{
    /// <summary>JSON-stat version.</summary>
    public string? Version { get; set; } = "2.0";

    /// <summary>The response class (always <see cref="ResponseClass.Collection"/>).</summary>
    public ResponseClass Class { get; set; } = ResponseClass.Collection;

    /// <summary>URL of the collection.</summary>
    public string? Href { get; set; }

    /// <summary>Short descriptive text.</summary>
    public string? Label { get; set; }

    /// <summary>Update time (ISO 8601).</summary>
    public string? Updated { get; set; }

    /// <summary>The link relations; <see cref="Link.Item"/> lists the collection items.</summary>
    public Link? Link { get; set; }

    /// <summary>Provider-specific extension.</summary>
    public JsonElement? Extension { get; set; }

    /// <summary>Provider-specific extension properties not modelled explicitly.</summary>
    [JsonExtensionData]
    public IDictionary<string, JsonElement>? ExtensionData { get; set; }

    /// <summary>Embedded datasets found in <c>link.item</c> (populated on parse).</summary>
    [JsonIgnore]
    internal List<Dataset> EmbeddedDatasets { get; } = new List<Dataset>();

    /// <summary>The collection items.</summary>
    [JsonIgnore]
    public IReadOnlyList<LinkItem> Items => Link?.Item ?? Array.Empty<LinkItem>();

    /// <summary>Gets the item at <paramref name="index"/>, or <c>null</c>.</summary>
    public LinkItem? Item(int index)
    {
        var items = Items;
        return index >= 0 && index < items.Count ? items[index] : null;
    }

    /// <summary>Gets the items of a given class.</summary>
    public IReadOnlyList<LinkItem> ItemsOf(ResponseClass filter) =>
        Items.Where(i => i.Class == filter).ToArray();
}