// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Diagnostics.CodeAnalysis;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc.Routing;

namespace Microsoft.AspNetCore.Mvc
{
    /// <summary>
    /// Defines the contract for the helper to build URLs for ASP.NET MVC within an application.
    /// </summary>
    public interface IUrlHelper
    {
        /// <summary>
        /// Gets the <see cref="ActionContext"/> for the current request.
        /// </summary>
        ActionContext ActionContext { get; }

        /// <summary>
        /// Generates a URL with an absolute path for an action method, which contains the action
        /// name, controller name, route values, protocol to use, host name, and fragment specified by
        /// <see cref="UrlActionContext"/>. Generates an absolute URL if <see cref="UrlActionContext.Protocol"/> and
        /// <see cref="UrlActionContext.Host"/> are non-<c>null</c>. See the remarks section for important security information.
        /// </summary>
        /// <param name="actionContext">The context object for the generated URLs for an action method.</param>
        /// <returns>The generated URL.</returns>
        /// <remarks>
        /// <para>
        /// The value of <see cref="UrlActionContext.Host" /> should be a trusted value. Relying on the value of the current request
        /// can allow untrusted input to influence the resulting URI unless the <c>Host</c> header has been validated.
        /// See the deployment documentation for instructions on how to properly validate the <c>Host</c> header in
        /// your deployment environment.
        /// </para>
        /// </remarks>
        string? Action(UrlActionContext actionContext);

        /// <summary>
        /// Converts a virtual (relative, starting with ~/) path to an application absolute path.
        /// </summary>
        /// <remarks>
        /// If the specified content path does not start with the tilde (~) character,
        /// this method returns <paramref name="contentPath"/> unchanged.
        /// </remarks>
        /// <param name="contentPath">The virtual path of the content.</param>
        /// <returns>The application absolute path.</returns>
        [return: NotNullIfNotNull("contentPath")]
        string? Content(string? contentPath);

        /// <summary>
        /// Returns a value that indicates whether the URL is local. A URL is considered local if it does not have a
        /// host / authority part and it has an absolute path. URLs using virtual paths ('~/') are also local.
        /// </summary>
        /// <param name="url">The URL.</param>
        /// <returns><c>true</c> if the URL is local; otherwise, <c>false</c>.</returns>
        /// <example>
        /// <para>
        /// For example, the following URLs are considered local:
        /// <code>
        /// /Views/Default/Index.html
        /// ~/Index.html
        /// </code>
        /// </para>
        /// <para>
        /// The following URLs are non-local:
        /// <code>
        /// ../Index.html
        /// http://www.contoso.com/
        /// http://localhost/Index.html
        /// </code>
        /// </para>
        /// </example>
        bool IsLocalUrl([NotNullWhen(true)] string? url);

        /// <summary>
        /// Generates a URL with an absolute path, which contains the route name, route values, protocol to use, host
        /// name, and fragment specified by <see cref="UrlRouteContext"/>. Generates an absolute URL if
        /// <see cref="UrlActionContext.Protocol"/> and <see cref="UrlActionContext.Host"/> are non-<c>null</c>.
        /// See the remarks section for important security information.
        /// </summary>
        /// <param name="routeContext">The context object for the generated URLs for a route.</param>
        /// <returns>The generated URL.</returns>
        /// <remarks>
        /// <para>
        /// The value of <see cref="UrlRouteContext.Host" /> should be a trusted value. Relying on the value of the current request
        /// can allow untrusted input to influence the resulting URI unless the <c>Host</c> header has been validated.
        /// See the deployment documentation for instructions on how to properly validate the <c>Host</c> header in
        /// your deployment environment.
        /// </para>
        /// </remarks>
        string? RouteUrl(UrlRouteContext routeContext);

        /// <summary>
        /// Generates an absolute URL for the specified <paramref name="routeName"/> and route
        /// <paramref name="values"/>, which contains the protocol (such as "http" or "https") and host name from the
        /// current request. See the remarks section for important security information.
        /// </summary>
        /// <param name="routeName">The name of the route that is used to generate URL.</param>
        /// <param name="values">An object that contains route values.</param>
        /// <returns>The generated absolute URL.</returns>
        /// <remarks>
        /// <para>
        /// This method uses the value of <see cref="HttpRequest.Host"/> to populate the host section of the generated URI.
        /// Relying on the value of the current request can allow untrusted input to influence the resulting URI unless
        /// the <c>Host</c> header has been validated. See the deployment documentation for instructions on how to properly
        /// validate the <c>Host</c> header in your deployment environment.
        /// </para>
        /// </remarks>
        string? Link(string? routeName, object? values);
    }
}
