JsonLdContext.cs

using System;
using System.Collections.Generic;
 
namespace Waher.Content.Semantic
{
    internal class JsonLdContext
    {
        private readonly Dictionary<string, object> context;
 
        public JsonLdContext()
            : this(null, null)
        {
        }
 
        public JsonLdContext(Dictionary<string, object> Context, Uri BaseUri)
        {
            this.context = new Dictionary<string, object>();
 
            if (!(Context is null))
            {
                foreach (KeyValuePair<string, object> P in Context)
                {
                    string Name = this.GetFullyQualifiedName(P.Key);
                    this.context[Name] = P.Value;
                    this.SetProperty(Name, P.Value, BaseUri);
                }
            }
        }
 
        private void SetProperty(string Name, object Value, Uri BaseUri)
        {
            switch (Name)
            {
                case "@id":
                    this.Id = this.ToUri(Value, BaseUri);
                    break;
 
                case "@type":
                    this.Type = this.ToUri(Value, BaseUri);
                    break;
 
                case "@base":
                    this.Base = this.ToUri(Value, BaseUri);
                    break;
 
                case "@version":
                    if (Value is double d)
                        this.Version = d;
                    break;
 
                case "@vocab":
                    this.Vocabulary = this.ToUri(Value, BaseUri);
                    break;
            }
        }
 
        private string GetFullyQualifiedName(string Name)
        {
            int i = Name.IndexOf(':');
            if (i >= 0)
            {
                string Prefix = Name.Substring(0, i);
 
                if (this.TryGetStringValue(Prefix, out string PrefixUrl))
                    return PrefixUrl + Name.Substring(i + 1);
            }
 
            return Name;
        }
 
        private Uri ToUri(object Value, Uri BaseUri)
        {
            if (Value is string s)
            {
                s = this.GetFullyQualifiedName(s);
                BaseUri = this.Base ?? BaseUri;
 
                if (BaseUri is null)
                {
                    if (Uri.TryCreate(s, UriKind.Absolute, out Uri ParsedUri))
                        return ParsedUri;
                }
                else
                {
                    if (Uri.TryCreate(BaseUri, s, out Uri ParsedUri))
                        return ParsedUri;
                }
            }
 
            return null;
        }
 
        public Uri Id { get; private set; }
 
        public Uri Type { get; private set; }
 
        public Uri Base { get; private set; }
 
        public double Version { get; private set; }
 
        public Uri Vocabulary { get; private set; }
 
        public object this[string Name]
        {
            get
            {
                if (this.context.TryGetValue(Name, out object Value))
                    return Value;
                else
                    return null;
            }
        }
 
        public bool TryGetStringValue(string Name, out string StringValue)
        {
            if (this.context.TryGetValue(Name, out object Value) && Value is string s)
            {
                StringValue = s;
                return true;
            }
            else
            {
                StringValue = null;
                return false;
            }
        }
 
        public bool TryGetObjectValue(string Name, out object Value)
        {
            return this.context.TryGetValue(Name, out Value);
        }
 
        public void Append(JsonLdContext Context, Uri BaseUri)
        {
            foreach (KeyValuePair<string, object> P in Context.context)
            {
                string Name = this.GetFullyQualifiedName(P.Key);
                object Value = P.Value;
 
                if (this.context.TryGetValue(Name, out object Prev) &&
                    Prev is string PrevString &&
                    Uri.TryCreate(BaseUri, PrevString, out Uri PrevUri) &&
                    Uri.TryCreate(PrevUri, P.Value?.ToString(), out Uri NewUri))
                {
                    Value = NewUri.AbsoluteUri;
                }
 
                this.context[Name] = Value;
                this.SetProperty(Name, Value, BaseUri);
            }
        }
 
        public void Append(JsonLdContext Context)
        {
            foreach (KeyValuePair<string, object> P in Context.context)
                this.context[P.Key] = P.Value;
        }
    }
}