awesome-uiwidgets/AwesomeUIWidgets/Assets/Scripts/ChatRoom/preview_data.cs

using System.Collections.Generic;
using JetBrains.Annotations;
using UIWidgetsSample;

namespace ChatComponents
{
    public class PreviewData : Equatable
    {
        /// Link description (usually og:description meta tag)
        public readonly string description;

        /// See [PreviewDataImage]
        public readonly PreviewDataImage image;

        /// Remote resource URL
        public readonly string link;

        /// Link title (usually og:title meta tag)
        public readonly string title;

        /// Creates preview data.
        public PreviewData(
            string description = null,
            [CanBeNull] PreviewDataImage image = null,
            string link = null,
            string title = null
        )
        {
            this.description = description;
            this.image = image;
            this.link = link;
            this.title = title;
        }

        /// Equatable props
        public override List<object> props => new List<object>
            {description, image, link, title};

        /// Creates preview data from a map (decoded JSON).
        public static PreviewData fromJson(Dictionary<string, object> json)
        {
            return new PreviewData(
                json["description"] as string,
                json["image"] == null
                    ? null
                    : PreviewDataImage.fromJson(json["image"] as Dictionary<string, object>),
                json["link"] as string,
                json["title"] as string
            );
        }

        /// Converts preview data to the map representation, encodable to JSON.
        public Dictionary<string, object> toJson()
        {
            return new Dictionary<string, object>
            {
                {"description", description},
                {"image", image?.toJson()},
                {"link", link},
                {"title", title}
            };
        }

        /// Creates a copy of the preview data with an updated data.
        /// Null values will nullify existing values.
        private PreviewData copyWith(
            string description = null,
            PreviewDataImage image = null,
            string link = null,
            string title = null
        )
        {
            return new PreviewData(
                description,
                image,
                link,
                title
            );
        }
    }

    /// A utility class that forces image"s width and height to be stored
    /// alongside the url.
    /// 
    /// See https://github.com/flyerhq/flutter_link_previewer
    public class PreviewDataImage : Equatable
    {
        /// Image height in pixels
        public readonly float height;

        /// Remote image URL
        public readonly string url;

        /// Image width in pixels
        public readonly float width;

        /// Creates preview data image.
        public PreviewDataImage(
            float height,
            string url,
            float width)
        {
            this.height = height;
            this.url = url;
            this.width = width;
        }

        /// Equatable props

        public override List<object> props => new List<object>
            {height, url, width};

        /// Creates preview data image from a map (decoded JSON).
        public static PreviewDataImage fromJson(Dictionary<string, object> json)
        {
            return new PreviewDataImage(
                json["height"] is float ? (float) json["height"] : 0,
                json["url"] as string,
                json["width"] is float ? (float) json["width"] : 0
            );
        }

        /// Converts preview data image to the map representation, encodable to JSON.
        public Dictionary<string, object> toJson()
        {
            return new Dictionary<string, object>
            {
                {"height", height},
                {"url", url},
                {"width", width}
            };
        }
    }
}