// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using Microsoft.AspNetCore.Builder.Extensions;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;
 
namespace Microsoft.AspNetCore.Builder;
 
/// <summary>
/// Extension methods for <see cref="IApplicationBuilder"/>.
/// </summary>
public static class UsePathBaseExtensions
{
    /// <summary>
    /// Adds a middleware that extracts the specified path base from request path and postpend it to the request path base.
    /// </summary>
    /// <param name="app">The <see cref="IApplicationBuilder"/> instance.</param>
    /// <param name="pathBase">The path base to extract.</param>
    /// <returns>The <see cref="IApplicationBuilder"/> instance.</returns>
    public static IApplicationBuilder UsePathBase(this IApplicationBuilder app, PathString pathBase)
    {
        ArgumentNullException.ThrowIfNull(app);
 
        // Strip trailing slashes
        pathBase = new PathString(pathBase.Value?.TrimEnd('/'));
        if (!pathBase.HasValue)
        {
            return app;
        }
 
        // Only use this path if there's a global router (in the 'WebApplication' case).
        if (app.Properties.TryGetValue(RerouteHelper.GlobalRouteBuilderKey, out var routeBuilder) && routeBuilder is not null)
        {
            return app.Use(next =>
            {
                var newNext = RerouteHelper.Reroute(app, routeBuilder, next);
                return new UsePathBaseMiddleware(newNext, pathBase).Invoke;
            });
        }
 
        return app.UseMiddleware<UsePathBaseMiddleware>(pathBase);
    }
}