SF-3184 Add USJ conversion support to and from USX

src/SIL.Converters.Usj/IUsj.cs

@@ -0,0 +1,27 @@
+using System.Collections;
+
+namespace SIL.Converters.Usj
+{
+    /// <summary>
+    /// An interface for Unified Scripture JSON (USJ) types.
+    /// </summary>
+    public interface IUsj
+    {
+        /// <summary>
+        /// The JSON representation of scripture contents from USFM/USX.
+        /// </summary>
+        /// <value>This will either be a <see cref="UsjMarker"/> or <see cref="string"/>.</value>
+        /// <remarks>Nullable. The contents will be laid out in order.</remarks>
+        ArrayList Content { get; set; }
+
+        /// <summary>
+        /// The USJ spec type.
+        /// </summary>
+        string Type { get; set; }
+
+        /// <summary>
+        /// The USJ spec version.
+        /// </summary>
+        string Version { get; set; }
+    }
+}

src/SIL.Converters.Usj/LowerCaseNamingStrategy.cs

@@ -0,0 +1,13 @@
+using Newtonsoft.Json.Serialization;
+
+namespace SIL.Converters.Usj
+{
+    /// <summary>
+    /// Ensures that the JSON properties for the USJ data model are in lower case.
+    /// </summary>
+    internal class LowerCaseNamingStrategy : NamingStrategy
+    {
+        /// <inheritdoc />
+        protected override string ResolvePropertyName(string name) => name.ToLowerInvariant();
+    }
+}

src/SIL.Converters.Usj/SIL.Converters.Usj.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netstandard2.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
+  </ItemGroup>
+
+</Project>

src/SIL.Converters.Usj/Usj.cs

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+namespace SIL.Converters.Usj
+{
+    /// <summary>
+    /// Unified Scripture JSON (USJ) - The JSON variant of USFM and USX data models.
+    /// These types follow this schema: <c>https://github.com/usfm-bible/tcdocs/blob/usj/grammar/usj.js</c>
+    /// </summary>
+    public class Usj : UsjBase, IUsj
+    {
+        /// <summary>
+        /// The supported USJ spec type.
+        /// </summary>
+        public const string UsjType = "USJ";
+
+        /// <summary>
+        /// The supported USJ spec version.
+        /// </summary>
+        public const string UsjVersion = "3.1";
+
+        /// <summary>
+        /// The USJ spec version.
+        /// </summary>
+        public string Version { get; set; }
+    }
+}

src/SIL.Converters.Usj/UsjBase.cs

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+using System.Collections;
+using System.Collections.Generic;
+using Newtonsoft.Json;
+
+namespace SIL.Converters.Usj
+{
+    /// <summary>
+    /// Elements shared between <see cref="Usj"/> and <see cref="UsjMarker"/>.
+    /// </summary>
+    [JsonObject(NamingStrategyType = typeof(LowerCaseNamingStrategy), ItemNullValueHandling = NullValueHandling.Ignore)]
+    public abstract class UsjBase
+    {
+        /// <summary>
+        /// For <see cref="Usj"/>, this is the USJ spec type.
+        /// For <see cref="UsjMarker"/>, this is the kind/category of node or element this is,
+        /// corresponding the USFM marker and USX node.
+        /// </summary>
+        /// <example><c>para</c>, <c>verse</c>, <c>char</c>.</example>
+        public string Type { get; set; }
+
+        /// <summary>
+        /// The JSON representation of scripture contents from USFM/USX.
+        /// </summary>
+        /// <value>This will either be a <see cref="UsjMarker"/> or <see cref="string"/>.</value>
+        /// <remarks>Nullable. The contents will be laid out in order.</remarks>
+        [JsonConverter(typeof(UsjContentConverter))]
+        public ArrayList Content { get; set; }
+
+        /// <summary>
+        /// Additional attributes that are not a part of the USJ specification.
+        /// This is only used for <see cref="UsjMarker"/>.
+        /// </summary>
+        /// <remarks>
+        /// These are typically <c>closed</c>, <c>colspan</c>, etc.
+        /// </remarks>
+        [JsonExtensionData]
+        public Dictionary<string, object> AdditionalData { get; } = new Dictionary<string, object>();
+    }
+}

src/SIL.Converters.Usj/UsjContentConverter.cs

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+using System;
+using System.Collections;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace SIL.Converters.Usj
+{
+    /// <summary>
+    /// Converts the contents of the Content <see cref="ArrayList"/> to and from JSON, preserving
+    /// the two supported content types: <see cref="string"/> and <see cref="UsjMarker"/>.
+    /// </summary>
+    public class UsjContentConverter : JsonConverter<ArrayList>
+    {
+        /// <inheritdoc />
+        public override ArrayList ReadJson(
+            JsonReader reader,
+            Type objectType,
+            ArrayList existingValue,
+            bool hasExistingValue,
+            JsonSerializer serializer
+        )
+        {
+            var jArray = JArray.Load(reader);
+            var list = new ArrayList();
+
+            foreach (JToken item in jArray)
+            {
+                if (item.Type == JTokenType.String)
+                {
+                    list.Add(item.ToString());
+                }
+                else
+                {
+                    var usjMarker = item.ToObject<UsjMarker>();
+                    list.Add(usjMarker);
+                }
+            }
+
+            return list;
+        }
+
+        /// <inheritdoc />
+        public override void WriteJson(JsonWriter writer, ArrayList value, JsonSerializer serializer)
+        {
+            JArray jArray = new JArray();
+            foreach (object item in value)
+            {
+                if (item is string str)
+                {
+                    jArray.Add(str);
+                }
+                else if (item is UsjMarker usjMarker)
+                {
+                    jArray.Add(JToken.FromObject(usjMarker));
+                }
+            }
+
+            jArray.WriteTo(writer);
+        }
+    }
+}

src/SIL.Converters.Usj/UsjMarker.cs

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+namespace SIL.Converters.Usj
+{
+    /// <summary>
+    /// A Scripture Marker and its contents.
+    /// </summary>
+    public class UsjMarker : UsjBase
+    {
+        /// <summary>
+        /// The corresponding marker in USFM or style in USX.
+        /// </summary>
+        /// <example><c>p</c>, <c>v</c>, <c>nd</c>.</example>
+        public string Marker { get; set; }
+
+        /// <summary>
+        /// Indicates the Book-chapter-verse value in the paragraph based structure.
+        /// </summary>
+        /// <remarks>Nullable.</remarks>
+        public string Sid { get; set; }
+
+        /// <summary>
+        /// Milestone end ID, matches start ID (not currently included in USJ spec).
+        /// </summary>
+        /// <remarks>Nullable.</remarks>
+        public string Eid { get; set; }
+
+        /// <summary>
+        /// Chapter number or verse number.
+        /// </summary>
+        /// <remarks>Nullable.</remarks>
+        public string Number { get; set; }
+
+        /// <summary>
+        /// The 3-letter book code in ID element.
+        /// </summary>
+        /// <remarks>Nullable.</remarks>
+        public string Code { get; set; }
+
+        /// <summary>
+        /// Alternate chapter number or verse number.
+        /// </summary>
+        /// <remarks>Nullable.</remarks>
+        public string AltNumber { get; set; }
+
+        /// <summary>
+        /// Published character of chapter or verse.
+        /// </summary>
+        /// <remarks>Nullable.</remarks>
+        public string PubNumber { get; set; }
+
+        /// <summary>
+        /// Caller character for footnotes and cross-refs.
+        /// </summary>
+        /// <remarks>Nullable.</remarks>
+        public string Caller { get; set; }
+
+        /// <summary>
+        /// Alignment of table cells.
+        /// </summary>
+        /// <remarks>Nullable.</remarks>
+        public string Align { get; set; }
+
+        /// <summary>
+        /// Category of extended study bible sections.
+        /// </summary>
+        /// <remarks>Nullable.</remarks>
+        public string Category { get; set; }
+    }
+}