// 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.Http.Features;
using Microsoft.AspNetCore.Mvc.Routing;

namespace Microsoft.AspNetCore.Routing;

/// <summary>
/// Extension methods for using <see cref="LinkGenerator"/> to generate links to Razor Pages.
/// </summary>
public static class PageLinkGeneratorExtensions
{
    /// <summary>
    /// Generates a URI with an absolute path based on the provided values.
    /// </summary>
    /// <param name="generator">The <see cref="LinkGenerator"/>.</param>
    /// <param name="httpContext">The <see cref="HttpContext"/> associated with the current request.</param>
    /// <param name="page">
    /// The page name. Used to resolve endpoints. Optional. If <c>null</c> is provided, the current page route value
    /// will be used.
    /// </param>
    /// <param name="handler">
    /// The page handler name. Used to resolve endpoints. Optional.
    /// </param>
    /// <param name="values">The route values. Optional. Used to resolve endpoints and expand parameters in the route template.</param>
    /// <param name="pathBase">
    /// An optional URI path base. Prepended to the path in the resulting URI. If not provided, the value of <see cref="HttpRequest.PathBase"/> will be used.
    /// </param>
    /// <param name="fragment">A URI fragment. Optional. Appended to the resulting URI.</param>
    /// <param name="options">
    /// An optional <see cref="LinkOptions"/>. Settings on provided object override the settings with matching
    /// names from <c>RouteOptions</c>.
    /// </param>
    /// <returns>A URI with an absolute path, or <c>null</c> if a URI cannot be created.</returns>
    [SuppressMessage("ApiDesign", "RS0026:Do not add multiple public overloads with optional parameters", Justification = "Required to maintain compatibility")]
    public static string? GetPathByPage(
        this LinkGenerator generator,
        HttpContext httpContext,
        string? page = default,
        string? handler = default,
        object? values = default,
        PathString? pathBase = default,
        FragmentString fragment = default,
        LinkOptions? options = default)
    {
        ArgumentNullException.ThrowIfNull(generator);
        ArgumentNullException.ThrowIfNull(httpContext);

        var address = CreateAddress(httpContext, page, handler, values);
        return generator.GetPathByAddress<RouteValuesAddress>(
            httpContext,
            address,
            address.ExplicitValues,
            address.AmbientValues,
            pathBase,
            fragment,
            options);
    }

    /// <summary>
    /// Generates a URI with an absolute path based on the provided values.
    /// </summary>
    /// <param name="generator">The <see cref="LinkGenerator"/>.</param>
    /// <param name="page">
    /// The page name. Used to resolve endpoints.
    /// </param>
    /// <param name="handler">
    /// The page handler name. Used to resolve endpoints. Optional.
    /// </param>
    /// <param name="values">The route values. Optional. Used to resolve endpoints and expand parameters in the route template.</param>
    /// <param name="pathBase">An optional URI path base. Prepended to the path in the resulting URI.</param>
    /// <param name="fragment">A URI fragment. Optional. Appended to the resulting URI.</param>
    /// <param name="options">
    /// An optional <see cref="LinkOptions"/>. Settings on provided object override the settings with matching
    /// names from <c>RouteOptions</c>.
    /// </param>
    /// <returns>A URI with an absolute path, or <c>null</c> if a URI cannot be created.</returns>
    [SuppressMessage("ApiDesign", "RS0026:Do not add multiple public overloads with optional parameters", Justification = "Required to maintain compatibility")]
    public static string? GetPathByPage(
        this LinkGenerator generator,
        string page,
        string? handler = default,
        object? values = default,
        PathString pathBase = default,
        FragmentString fragment = default,
        LinkOptions? options = default)
    {
        ArgumentNullException.ThrowIfNull(generator);
        ArgumentNullException.ThrowIfNull(page);

        var address = CreateAddress(httpContext: null, page, handler, values);
        return generator.GetPathByAddress(address, address.ExplicitValues, pathBase, fragment, options);
    }

    /// <summary>
    /// Generates an absolute URI based on the provided values.
    /// </summary>
    /// <param name="generator">The <see cref="LinkGenerator"/>.</param>
    /// <param name="httpContext">The <see cref="HttpContext"/> associated with the current request.</param>
    /// <param name="page">
    /// The page name. Used to resolve endpoints. Optional. If <c>null</c> is provided, the current page route value
    /// will be used.
    /// </param>
    /// <param name="handler">
    /// The page handler name. Used to resolve endpoints. Optional.
    /// </param>
    /// <param name="values">The route values. Optional. Used to resolve endpoints and expand parameters in the route template.</param>
    /// <param name="scheme">
    /// The URI scheme, applied to the resulting URI. Optional. If not provided, the value of <see cref="HttpRequest.Scheme"/> will be used.
    /// </param>
    /// <param name="host">
    /// The URI host/authority, applied to the resulting URI. Optional. If not provided, the value <see cref="HttpRequest.Host"/> will be used.
    /// </param>
    /// <param name="pathBase">
    /// An optional URI path base. Prepended to the path in the resulting URI. If not provided, the value of <see cref="HttpRequest.PathBase"/> will be used.
    /// </param>
    /// <param name="fragment">A URI fragment. Optional. Appended to the resulting URI.</param>
    /// <param name="options">
    /// An optional <see cref="LinkOptions"/>. Settings on provided object override the settings with matching
    /// names from <c>RouteOptions</c>.
    /// </param>
    /// <returns>A absolute URI, or <c>null</c> if a URI cannot be created.</returns>
    /// <remarks>
    /// <para>
    /// The value of <paramref name="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>
    [SuppressMessage("ApiDesign", "RS0026:Do not add multiple public overloads with optional parameters", Justification = "Required to maintain compatibility")]
    public static string? GetUriByPage(
        this LinkGenerator generator,
        HttpContext httpContext,
        string? page = default,
        string? handler = default,
        object? values = default,
        string? scheme = default,
        HostString? host = default,
        PathString? pathBase = default,
        FragmentString fragment = default,
        LinkOptions? options = default)
    {
        ArgumentNullException.ThrowIfNull(generator);
        ArgumentNullException.ThrowIfNull(httpContext);

        var address = CreateAddress(httpContext, page, handler, values);
        return generator.GetUriByAddress<RouteValuesAddress>(
            httpContext,
            address,
            address.ExplicitValues,
            address.AmbientValues,
            scheme,
            host,
            pathBase,
            fragment,
            options);
    }

    /// <summary>
    /// Generates an absolute URI based on the provided values.
    /// </summary>
    /// <param name="generator">The <see cref="LinkGenerator"/>.</param>
    /// <param name="page">The page name. Used to resolve endpoints.</param>
    /// <param name="handler">The page handler name. May be null.</param>
    /// <param name="values">The route values. May be null. Used to resolve endpoints and expand parameters in the route template.</param>
    /// <param name="scheme">The URI scheme, applied to the resulting URI.</param>
    /// <param name="host">The URI host/authority, applied to the resulting URI.</param>
    /// <param name="pathBase">An optional URI path base. Prepended to the path in the resulting URI.</param>
    /// <param name="fragment">A URI fragment. Optional. Appended to the resulting URI.</param>
    /// <param name="options">
    /// An optional <see cref="LinkOptions"/>. Settings on provided object override the settings with matching
    /// names from <c>RouteOptions</c>.
    /// </param>
    /// <returns>A absolute URI, or <c>null</c> if a URI cannot be created.</returns>
    /// <remarks>
    /// <para>
    /// The value of <paramref name="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>
    [SuppressMessage("ApiDesign", "RS0026:Do not add multiple public overloads with optional parameters", Justification = "Required to maintain compatibility")]
    public static string? GetUriByPage(
        this LinkGenerator generator,
        string page,
        string? handler,
        object? values,
        string scheme,
        HostString host,
        PathString pathBase = default,
        FragmentString fragment = default,
        LinkOptions? options = default)
    {
        ArgumentNullException.ThrowIfNull(generator);
        ArgumentNullException.ThrowIfNull(page);

        var address = CreateAddress(httpContext: null, page, handler, values);
        return generator.GetUriByAddress<RouteValuesAddress>(address, address.ExplicitValues, scheme, host, pathBase, fragment, options);
    }

    private static RouteValuesAddress CreateAddress(HttpContext? httpContext, string? page, string? handler, object? values)
    {
        var explicitValues = new RouteValueDictionary(values);
        var ambientValues = GetAmbientValues(httpContext);

        UrlHelperBase.NormalizeRouteValuesForPage(context: null, page, handler, explicitValues, ambientValues);

        return new RouteValuesAddress()
        {
            AmbientValues = ambientValues,
            ExplicitValues = explicitValues
        };
    }

    private static RouteValueDictionary? GetAmbientValues(HttpContext? httpContext)
    {
        return httpContext?.Features.Get<IRouteValuesFeature>()?.RouteValues;
    }
}
