// <copyright>

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

// </copyright>



namespace Microsoft.ApplicationServer.Http.Dispatcher

{

    using System;

    using System.Collections.Generic;

    using System.Net.Http;

    using Microsoft.ApplicationServer.Http.Description;

    using Microsoft.Server.Common;



    /// <summary>

    /// A <see cref="HttpOperationHandler"/> that matches an input <see cref="Uri"/> against a 

    /// given <see cref="UriTemplate"/> and outputs <see cref="UriTemplate"/> variable

    /// values as strings.

    /// </summary>

    public class UriTemplateHandler : HttpOperationHandler

    {

        /// <summary>

        /// Initializes a new instance of a <see cref="UriTemplateHandler"/> with the

        /// given <paramref name="baseAddress"/> and <paramref name="uriTemplate"/>.

        /// </summary>

        /// <param name="baseAddress">

        /// The base address to use when matching a <see cref="Uri"/> against the given <paramref name="uriTemplate"/>

        /// </param> 

        /// <param name="uriTemplate">

        /// The <see cref="UriTemplate"/> to match against input <see cref="Uri">Uris</see>.

        /// </param>

        public UriTemplateHandler(Uri baseAddress, UriTemplate uriTemplate)

        {

            if (baseAddress == null)

            {

                throw Fx.Exception.ArgumentNull("baseAddress");

            }



            if (uriTemplate == null)

            {

                throw Fx.Exception.ArgumentNull("uriTemplate");

            }



            this.BaseAddress = baseAddress;

            this.UriTemplate = uriTemplate;

        }



        /// <summary>

        /// Gets the base address to use when matching a <see cref="Uri"/> against the <cref name="UriTemplate"/>.

        /// </summary>

        public Uri BaseAddress { get; private set; }



        /// <summary>

        /// Gets the <see cref="UriTemplate"/> to match against input <see cref="Uri"/> instances.

        /// </summary>

        public UriTemplate UriTemplate { get; private set; }



        /// <summary>

        /// Retrieves the collection of <see cref="HttpParameter"/> instances describing the

        /// input values for this <see cref="UriTemplateHandler"/>.

        /// </summary>

        /// <remarks>

        /// The <see cref="UriTemplateHandler"/> always returns a single input of

        /// <see cref="HttpParameter.RequestMessage"/>.

        /// </remarks>

        /// <returns>A collection that consists of just the <see cref="HttpParameter.RequestMessage"/>.</returns>

        protected override sealed IEnumerable<HttpParameter> OnGetInputParameters()

        {

            return new HttpParameter[] { HttpParameter.RequestMessage };

        }



        /// <summary>

        /// Retrieves the collection of <see cref="HttpParameter"/> instances describing the

        /// output values of this <see cref="UriTemplateHandler"/>.

        /// </summary>

        /// <remarks>

        /// The <see cref="UriTemplateHandler"/> always returns output <see cref="HttpParameter"/> 

        /// instances in which the <see cref="HttpParameter.Name"/> is the <see cref="UriTemplateHandler.UriTemplate"/>

        /// variable and the <see cref="HttpParameter.ParameterType"/> is of type <see cref="String"/>.

        /// </remarks>

        /// <returns>The collection of <see cref="HttpParameter"/> instances.</returns>

        protected override sealed IEnumerable<HttpParameter> OnGetOutputParameters()

        {

            int numberOfVariables = this.UriTemplate.PathSegmentVariableNames.Count + this.UriTemplate.QueryValueVariableNames.Count;

            

            HttpParameter[] parameters = new HttpParameter[numberOfVariables];

            int i = 0;



            foreach (string name in this.UriTemplate.PathSegmentVariableNames)

            {

                parameters[i] = new HttpParameter(name, TypeHelper.StringType);

                i++;

            }



            foreach (string name in this.UriTemplate.QueryValueVariableNames)

            {

                parameters[i] = new HttpParameter(name, TypeHelper.StringType);

                i++;

            }



            return parameters;

        }



        /// <summary>

        /// Called to execute this <see cref="UriTemplateHandler"/>.

        /// </summary>

        /// <param name="input">

        /// The input values to handle, corresponding to the <see cref="HttpParameter"/> 

        /// returned by <see cref="OnGetInputParameters"/>

        /// </param>

        /// <returns>

        /// The <see cref="UriTemplate"/> variable values from matching the <see cref="UriTemplate"/>

        /// agains the request <see cref="Uri"/>.

        /// </returns>

        protected override sealed object[] OnHandle(object[] input)

        {

            Fx.Assert(input != null, "The 'input' parameter should not be null.");

            Fx.Assert(input.Length == 1, "There should be one element in the 'input' array");



            HttpRequestMessage requestMessage = input[0] as HttpRequestMessage;

            if (requestMessage == null)

            {

                throw Fx.Exception.ArgumentNull(HttpParameter.RequestMessage.Name);

            }



            Uri uri = requestMessage.RequestUri;

            int numberOfParameters = this.OutputParameters.Count;

            object[] output = new object[numberOfParameters];

            if (uri != null)

            {

                UriTemplateMatch match = this.UriTemplate.Match(this.BaseAddress, uri);



                if (match == null)

                {

                    throw Fx.Exception.AsError(

                        new InvalidOperationException(

                            Http.SR.UriTemplateDoesNotMatchUri(

                                uri.ToString(),

                                this.UriTemplate.ToString())));

                }

                

                for (int i = 0; i < numberOfParameters; i++)

                {

                    output[i] = match.BoundVariables[i];

                }

            }



            return output;

        }

    }

}