using System;

using System.Collections.Generic;

using System.Linq;

using System.Reactive;

using System.Reflection;

using System.Reactive.Linq;

using System.Text;

using ReactiveUI;

using Splat;

namespace ReactiveUI

{

public static class ViewLocator

{

public static IViewLocator Current {

get {

var ret = Locator.Current.GetService<IViewLocator>();

if (ret == null) {

throw new Exception("Could not find a default ViewLocator. This should never happen, your dependency resolver is broken");

}

return ret;

}

}

}

class DefaultViewLocator : IViewLocator, IEnableLogger

{

public Func<string, string> ViewModelToViewFunc { get; set; }

public DefaultViewLocator(Func<string, string> viewModelToViewFunc = null)

{

ViewModelToViewFunc = viewModelToViewFunc ??

(vm => interfaceifyTypeName(vm.Replace("ViewModel", "View")));

}

/// <summary>

/// Returns the View associated with a ViewModel, deriving the name of

/// the Type via ViewModelToViewFunc, then discovering it via

/// ServiceLocator.

/// </summary>

/// <param name="viewModel">The ViewModel for which to find the

/// associated View.</param>

/// <returns>The View for the ViewModel.</returns>

public IViewFor ResolveView<T>(T viewModel, string contract = null)

where T : class

{

// Given IFooBarViewModel (whose name we derive from T), we'll look

// for a few things:

// * IFooBarView that implements IViewFor

// * IViewFor<IFooBarViewModel>

// * IViewFor<FooBarViewModel> (the original behavior in RxUI 3.1)

var attrs = viewModel.GetType().GetTypeInfo().GetCustomAttributes(typeof (ViewContractAttribute), true);

if (attrs.Any()) {

contract = contract ?? ((ViewContractAttribute) attrs.First()).Contract;

}

// IFooBarView that implements IViewFor (or custom ViewModelToViewFunc)

var typeToFind = ViewModelToViewFunc(viewModel.GetType().AssemblyQualifiedName);

var ret = attemptToResolveView(Reflection.ReallyFindType(typeToFind, false), contract);

if (ret != null) return ret;

// IViewFor<FooBarViewModel> (the original behavior in RxUI 3.1)

var viewType = typeof (IViewFor<>);

return attemptToResolveView(viewType.MakeGenericType(viewModel.GetType()), contract);

}

IViewFor attemptToResolveView(Type type, string contract)

{

if (type == null) return null;

var ret = default(IViewFor);

try {

ret = (IViewFor)Locator.Current.GetService(type, contract);

} catch (Exception ex) {

this.Log().ErrorException("Failed to instantiate view: " + type.FullName, ex);

throw;

}

return ret;

}

static string interfaceifyTypeName(string typeName)

{

var idxComma = typeName.IndexOf( ',' );

var idxPeriod = typeName.LastIndexOf( '.', idxComma - 1 );

return typeName.Insert( idxPeriod+1, "I" );

}

}

}