//===================================================================================

// Microsoft patterns & practices

// Composite Application Guidance for Windows Presentation Foundation and Silverlight

//===================================================================================

// Copyright (c) Microsoft Corporation.  All rights reserved.

// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY

// OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT

// LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND

// FITNESS FOR A PARTICULAR PURPOSE.

//===================================================================================

// The example companies, organizations, products, domain names,

// e-mail addresses, logos, people, places, and events depicted

// herein are fictitious.  No association with any real company,

// organization, product, domain name, email address, logo, person,

// places, or events is intended or should be inferred.

//===================================================================================

using System;

using System.Collections.Generic;

using System.Linq;



namespace MVVM.Questionnaires.Framework

{

    /// <summary>

    /// Manages validation errors for an object, notifying when the error state changes.

    /// </summary>

    /// <typeparam name="T"></typeparam>

    public class ErrorsContainer<T>

    {

        private static readonly T[] noErrors = new T[0];

        private readonly Action<string> raiseErrorsChanged;

        private readonly Dictionary<string, List<T>> validationResults;



        /// <summary>

        /// Initializes a new instance of the <see cref="ErrorsContainer{T}"/> class.

        /// </summary>

        /// <param name="raiseErrorsChanged">The action that raises the <see cref="INotifyDataErrorInfo.ErrorsChanged"/>

        /// event.</param>

        public ErrorsContainer(Action<string> raiseErrorsChanged)

        {

            if (raiseErrorsChanged == null)

            {

                throw new ArgumentNullException("raiseErrorsChanged");

            }



            this.raiseErrorsChanged = raiseErrorsChanged;

            this.validationResults = new Dictionary<string, List<T>>();

        }



        /// <summary>

        /// Gets a value that indicates whether the object has validation errors. 

        /// </summary>

        public bool HasErrors

        {

            get

            {

                return this.validationResults.Count != 0;

            }

        }



        /// <summary>

        /// Gets the validation errors for a specified property.

        /// </summary>

        /// <param name="propertyName">The name of the property.</param>

        /// <returns>The validation errors of type <typeparamref name="T"/> for the property.</returns>

        public IEnumerable<T> GetErrors(string propertyName)

        {

            var localPropertyName = propertyName ?? string.Empty;

            List<T> currentValidationResults = null;

            if (this.validationResults.TryGetValue(localPropertyName, out currentValidationResults))

            {

                return currentValidationResults;

            }

            else

            {

                return noErrors;

            }

        }



        /// <summary>

        /// Sets the validation errors for the specified property.

        /// </summary>

        /// <remarks>

        /// If a change is detected then the errors changed event is raised.

        /// </remarks>

        /// <param name="propertyName">The name of the property.</param>

        /// <param name="newValidationResults">The new validation errors.</param>

        public void SetErrors(string propertyName, IEnumerable<T> newValidationResults)

        {

            var localPropertyName = propertyName ?? string.Empty;

            var hasCurrentValidationResults = this.validationResults.ContainsKey(localPropertyName);

            var hasNewValidationResults = newValidationResults != null && newValidationResults.Count() > 0;



            if (hasCurrentValidationResults || hasNewValidationResults)

            {

                if (hasNewValidationResults)

                {

                    this.validationResults[localPropertyName] = new List<T>(newValidationResults);

                    this.raiseErrorsChanged(localPropertyName);

                }

                else

                {

                    this.validationResults.Remove(localPropertyName);

                    this.raiseErrorsChanged(localPropertyName);

                }

            }

        }

    }

}