using System.Collections.Generic;

using System.Linq;

using System.Linq.Expressions;

using System.Reflection;

namespace JSONAPI.Core

{

/// <summary>

/// Utility for converting an property expression into a dot-separated path string

/// </summary>

public class PathVisitor : ExpressionVisitor

{

private readonly IResourceTypeRegistry _resourceTypeRegistry;

/// <summary>

/// Creates a new PathVisitor

/// </summary>

/// <param name="resourceTypeRegistry"></param>

public PathVisitor(IResourceTypeRegistry resourceTypeRegistry)

{

_resourceTypeRegistry = resourceTypeRegistry;

}

private readonly Stack<string> _segments = new Stack<string>();

public string Path { get { return string.Join(".", _segments.ToArray()); } }

protected override Expression VisitMethodCall(MethodCallExpression node)

{

if (node.Method.Name == "Select")

{

Visit(node.Arguments[1]);

Visit(node.Arguments[0]);

}

return node;

}

protected override Expression VisitMember(MemberExpression node)

{

var property = node.Member as PropertyInfo;

if (property == null) return node;

var registration = _resourceTypeRegistry.GetRegistrationForType(property.DeclaringType);

if (registration == null || registration.Relationships == null) return node;

var relationship = registration.Relationships.FirstOrDefault(r => r.Property == property);

if (relationship == null) return node;

_segments.Push(relationship.JsonKey);

return base.VisitMember(node);

}

}

}