using System.Linq;

using System.Threading.Tasks;

using JSONAPI.Documents;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

namespace JSONAPI.Json

{

/// <summary>

/// Default implementation of IResourceLinkageFormatter

/// </summary>

public class ResourceLinkageFormatter : IResourceLinkageFormatter

{

public Task Serialize(IResourceLinkage linkage, JsonWriter writer)

{

if (linkage.IsToMany)

{

writer.WriteStartArray();

foreach (var resourceIdentifier in linkage.Identifiers)

{

WriteResourceIdentifier(resourceIdentifier, writer);

}

writer.WriteEndArray();

}

else

{

var initialIdentifier = linkage.Identifiers.FirstOrDefault();

if (initialIdentifier == null)

writer.WriteNull();

else

{

WriteResourceIdentifier(initialIdentifier, writer);

}

}

return Task.FromResult(0);

}

private void WriteResourceIdentifier(IResourceIdentifier resourceIdentifier, JsonWriter writer)

{

writer.WriteStartObject();

writer.WritePropertyName("type");

writer.WriteValue(resourceIdentifier.Type);

writer.WritePropertyName("id");

writer.WriteValue(resourceIdentifier.Id);

writer.WriteEndObject();

}

public Task<IResourceLinkage> Deserialize(JsonReader reader, string currentPath)

{

IResourceLinkage linkage;

if (reader.TokenType == JsonToken.StartArray)

{

var array = JToken.ReadFrom(reader);

var resourceIdentifiers = array.Select(t => ReadResourceIdentifier(t, currentPath)).ToArray();

linkage = new ToManyResourceLinkage(resourceIdentifiers);

}

else if (reader.TokenType == JsonToken.StartObject)

{

var obj = JToken.ReadFrom(reader);

var resourceIdentifier = ReadResourceIdentifier(obj, currentPath);

linkage = new ToOneResourceLinkage(resourceIdentifier);

}

else if (reader.TokenType == JsonToken.Null)

{

linkage = new ToOneResourceLinkage(null);

}

else

{

throw new DeserializationException("Invalid linkage for relationship",

"Expected an array, object, or null for linkage, but got " + reader.TokenType, currentPath);

}

return Task.FromResult(linkage);

}

private IResourceIdentifier ReadResourceIdentifier(JToken t, string currentPath)

{

var jobject = t as JObject;

if (jobject == null)

throw new DeserializationException("Invalid resource identifier", "Resource identifiers must be an object.", currentPath);

var typeToken = jobject["type"];

if (typeToken == null)

throw new DeserializationException("Resource identifier missing type", "The `type` key is missing.", currentPath);

if (typeToken.Type != JTokenType.String)

throw new DeserializationException("Resource identifier type invalid",

"Expected a string value for `type` but encountered " + typeToken.Type, currentPath + "/type");

var type = typeToken.Value<string>();

if (string.IsNullOrWhiteSpace(type))

throw new DeserializationException("Resource identifier type empty", "The `type` key cannot be empty or whitespace.", currentPath + "/type");

var idToken = jobject["id"];

if (idToken == null)

throw new DeserializationException("Resource identifier missing id", "The `id` key is missing.", currentPath);

if (idToken.Type != JTokenType.String)

throw new DeserializationException("Resource identifier id invalid",

"Expected a string value for `id` but encountered " + idToken.Type, currentPath + "/id");

var id = idToken.Value<string>();

if (string.IsNullOrWhiteSpace(id))

throw new DeserializationException("Resource identifier id empty", "The `id` key cannot be empty or whitespace.", currentPath + "/id");

return new ResourceIdentifier(type, id);

}

}

}