New: First integration of a LDP Client (coscine/issues#1792)

src/Metadata/LDPWrapper/CoscineLDPWrapper.cs

+using Coscine.Configuration;
+using Coscine.Metadata.Util;
+using System;
+using System.IO;
+using System.Linq;
+using System.Net.Http;
+using System.Net.Http.Headers;
+using System.Threading.Tasks;
+using VDS.RDF;
+using VDS.RDF.Parsing;
+using VDS.RDF.Writing;
+
+namespace Coscine.Metadata.LDPWrapper
+{
+    /// <summary>
+    /// WIP Implementation of an implementation which interacts with Linked Data Platforms
+    /// </summary>
+    public class CoscineLDPWrapper : ILDPWrapper
+    {
+        // Will be documented when fully implemented
+#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
+
+        private readonly IConfiguration _configuration;
+        private readonly HttpClient _httpClient;
+        private readonly string _endpoint;
+
+        public string? JWT { get; set; }
+
+        public CoscineLDPWrapper(IConfiguration configuration, HttpClient httpClient, bool wrapperUse = true, string? jwt = null)
+        {
+            _configuration = configuration;
+            _httpClient = httpClient;
+            _endpoint = wrapperUse
+                ? _configuration.GetString("coscine/local/ldpwrapper/url", "http://localhost:5000/") 
+                : _configuration.GetString("coscine/local/trellis/url", "http://localhost:8253/");
+            JWT = jwt;
+        }
+
+        public async Task<string?> Add(string container, string identifier, IGraph? body = null)
+        {
+            var message = new HttpRequestMessage()
+            {
+                Method = HttpMethod.Post,
+                RequestUri = new Uri($"{_endpoint}{container}")
+            };
+
+            if (body != null)
+            {
+                message.Content = new StringContent(VDS.RDF.Writing.StringWriter.Write(body, new CompressingTurtleWriter()));
+                message.Content.Headers.ContentType = new MediaTypeHeaderValue("text/turtle");
+            }
+
+            message.Headers.Add("Accept", "text/turtle");
+            message.Headers.Add("Link", "<http://www.w3.org/ns/ldp#Resource>; rel=\"type\"");
+            message.Headers.Add("Slug", identifier);
+
+            return ParseIdentifier(
+                await FireRequest(message)
+            );
+        }
+
+        public async Task<string?> Create(string identifier, IGraph? body = null)
+        {
+            var message = new HttpRequestMessage()
+            {
+                Method = HttpMethod.Post,
+                RequestUri = new Uri($"{_endpoint}")
+            };
+
+            if (body != null)
+            {
+                message.Content = new StringContent(VDS.RDF.Writing.StringWriter.Write(body, new CompressingTurtleWriter()));
+                message.Content.Headers.ContentType = new MediaTypeHeaderValue("text/turtle");
+            }
+
+            message.Headers.Add("Accept", "text/turtle");
+            message.Headers.Add("Link", "<http://www.w3.org/ns/ldp#BasicContainer>; rel=\"type\"");
+            message.Headers.Add("Slug", identifier);
+
+            return ParseIdentifier(
+                await FireRequest(message)
+            );
+        }
+
+        public Task<bool> Delete(string identifier)
+        {
+            throw new NotImplementedException();
+        }
+
+        public async Task<IGraph?> Get(string identifier)
+        {
+            var message = new HttpRequestMessage()
+            {
+                Method = HttpMethod.Get,
+                RequestUri = new Uri($"{_endpoint}{identifier}")
+            };
+
+            message.Headers.Add("Accept", "text/turtle");
+
+            return await ParseGraph(
+                await FireRequest(message)
+            );
+        }
+
+        public async Task<bool> Exists(string identifier)
+        {
+            var message = new HttpRequestMessage()
+            {
+                Method = HttpMethod.Get,
+                RequestUri = new Uri($"{_endpoint}{identifier}")
+            };
+
+            message.Headers.Add("Accept", "text/turtle");
+
+            return (await FireRequest(message)).IsSuccessStatusCode;
+        }
+
+        public async Task<bool> SetAuthorization(string identifier, IGraph? body = null)
+        {
+            return await Update(identifier + "/?ext=acl", body, LinkType.Authorization);
+        }
+
+        public async Task<bool> Update(string identifier, IGraph? body = null, LinkType? linkType = null)
+        {
+            var message = new HttpRequestMessage()
+            {
+                Method = HttpMethod.Put,
+                RequestUri = new Uri($"{_endpoint}{identifier}")
+            };
+
+            if (body != null)
+            {
+                message.Content = new StringContent(VDS.RDF.Writing.StringWriter.Write(body, new CompressingTurtleWriter()));
+                message.Content.Headers.ContentType = new MediaTypeHeaderValue("text/turtle");
+            }
+
+            message.Headers.Add("Accept", "text/turtle");
+
+            if (linkType != null)
+            {
+                switch (linkType)
+                {
+                    case LinkType.Container:
+                        message.Headers.Add("Link", "<http://www.w3.org/ns/ldp#BasicContainer>; rel=\"type\"");
+                        break;
+                    case LinkType.Resource:
+                        message.Headers.Add("Link", "<http://www.w3.org/ns/ldp#Resource>; rel=\"type\"");
+                        break;
+                    case LinkType.Authorization:
+                        message.Headers.Add("Link", "<http://www.w3.org/ns/auth/acl#Authorization>; rel=\"type\"");
+                        break;
+                }
+            }
+
+            return (await FireRequest(message)).IsSuccessStatusCode;
+        }
+
+        private async Task<HttpResponseMessage> FireRequest(HttpRequestMessage message)
+        {
+            if (JWT != null)
+            {
+                message.Headers.Add("Authorization", $"Bearer {JWT}");
+            }
+
+            return await _httpClient.SendAsync(message);
+        }
+
+        private async Task<IGraph?> ParseGraph(HttpResponseMessage response)
+        {
+            var graphString = await response.Content.ReadAsStringAsync();
+
+            try
+            {
+                var graph = new Graph();
+                var ttlparser = new TurtleParser();
+                ttlparser.Load(graph, new StringReader(graphString));
+
+                return graph;
+            } 
+            catch
+            {
+                return null;
+            }
+        }
+
+        private string? ParseIdentifier(HttpResponseMessage response)
+        {
+            return response.Headers.GetValues("location").FirstOrDefault();
+        }
+
+#pragma warning restore CS1591 // Missing XML comment for publicly visible type or member
+    }
+}
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