// 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 System.Linq;
using Microsoft.AspNetCore.Mvc.ApplicationModels;
using Microsoft.AspNetCore.Mvc.Infrastructure;
using Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure;
using Microsoft.AspNetCore.Mvc.Routing;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.DependencyInjection;

namespace Microsoft.AspNetCore.Builder;

/// <summary>
/// Contains extension methods for using Razor Pages with <see cref="IEndpointRouteBuilder"/>.
/// </summary>
public static class RazorPagesEndpointRouteBuilderExtensions
{
    /// <summary>
    /// Adds endpoints for Razor Pages to the <see cref="IEndpointRouteBuilder"/>.
    /// </summary>
    /// <param name="endpoints">The <see cref="IEndpointRouteBuilder"/>.</param>
    /// <returns>An <see cref="PageActionEndpointConventionBuilder"/> for endpoints associated with Razor Pages.</returns>
    public static PageActionEndpointConventionBuilder MapRazorPages(this IEndpointRouteBuilder endpoints)
    {
        ArgumentNullException.ThrowIfNull(endpoints);

        EnsureRazorPagesServices(endpoints);

        return GetOrCreateDataSource(endpoints).DefaultBuilder;
    }

    /// <summary>
    /// Adds a specialized <see cref="RouteEndpoint"/> to the <see cref="IEndpointRouteBuilder"/> that will match
    /// requests for non-file-names with the lowest possible priority. The request will be routed to a page endpoint that
    /// matches <paramref name="page"/>.
    /// </summary>
    /// <param name="endpoints">The <see cref="IEndpointRouteBuilder"/> to add the route to.</param>
    /// <param name="page">The page name.</param>
    /// <remarks>
    /// <para>
    /// <see cref="MapFallbackToPage(IEndpointRouteBuilder, string)"/> is intended to handle cases where URL path of
    /// the request does not contain a file name, and no other endpoint has matched. This is convenient for routing
    /// requests for dynamic content to a SPA framework, while also allowing requests for non-existent files to
    /// result in an HTTP 404.
    /// </para>
    /// <para>
    /// <see cref="MapFallbackToPage(IEndpointRouteBuilder, string)"/> registers an endpoint using the pattern
    /// <c>{*path:nonfile}</c>. The order of the registered endpoint will be <c>int.MaxValue</c>.
    /// </para>
    /// <para>
    /// <see cref="MapFallbackToPage(IEndpointRouteBuilder, string)"/> does not re-execute routing, and will
    /// not generate route values based on routes defined elsewhere. When using this overload, the <c>path</c> route value
    /// will be available.
    /// </para>
    /// </remarks>
    public static IEndpointConventionBuilder MapFallbackToPage(this IEndpointRouteBuilder endpoints, string page)
    {
        ArgumentNullException.ThrowIfNull(endpoints);
        ArgumentNullException.ThrowIfNull(page);

        PageConventionCollection.EnsureValidPageName(page, nameof(page));

        EnsureRazorPagesServices(endpoints);

        // Called for side-effect to make sure that the data source is registered.
        var pageDataSource = GetOrCreateDataSource(endpoints);
        pageDataSource.CreateInertEndpoints = true;
        RegisterInCache(endpoints.ServiceProvider, pageDataSource);

        // Maps a fallback endpoint with an empty delegate. This is OK because
        // we don't expect the delegate to run.
        var builder = endpoints.MapFallback(context => Task.CompletedTask);
        builder.Add(b =>
        {
            // MVC registers a policy that looks for this metadata.
            b.Metadata.Add(CreateDynamicPageMetadata(page, area: null));
            b.Metadata.Add(new PageEndpointDataSourceIdMetadata(pageDataSource.DataSourceId));
        });
        return builder;
    }

    /// <summary>
    /// Adds a specialized <see cref="RouteEndpoint"/> to the <see cref="IEndpointRouteBuilder"/> that will match
    /// requests for non-file-names with the lowest possible priority. The request will be routed to a page endpoint that
    /// matches <paramref name="page"/>.
    /// </summary>
    /// <param name="endpoints">The <see cref="IEndpointRouteBuilder"/> to add the route to.</param>
    /// <param name="pattern">The route pattern.</param>
    /// <param name="page">The action name.</param>
    /// <remarks>
    /// <para>
    /// <see cref="MapFallbackToPage(IEndpointRouteBuilder, string, string)"/> is intended to handle cases where URL path of
    /// the request does not contain a file name, and no other endpoint has matched. This is convenient for routing
    /// requests for dynamic content to a SPA framework, while also allowing requests for non-existent files to
    /// result in an HTTP 404.
    /// </para>
    /// <para>
    /// The order of the registered endpoint will be <c>int.MaxValue</c>.
    /// </para>
    /// <para>
    /// This overload will use the provided <paramref name="pattern"/> verbatim. Use the <c>:nonfile</c> route contraint
    /// to exclude requests for static files.
    /// </para>
    /// <para>
    /// <see cref="MapFallbackToPage(IEndpointRouteBuilder, string, string)"/> does not re-execute routing, and will
    /// not generate route values based on routes defined elsewhere. When using this overload, the route values provided by matching
    /// <paramref name="pattern"/> will be available.
    /// </para>
    /// </remarks>
    public static IEndpointConventionBuilder MapFallbackToPage(
        this IEndpointRouteBuilder endpoints,
        [StringSyntax("Route")] string pattern,
        string page)
    {
        ArgumentNullException.ThrowIfNull(endpoints);
        ArgumentNullException.ThrowIfNull(pattern);
        ArgumentNullException.ThrowIfNull(page);

        PageConventionCollection.EnsureValidPageName(page, nameof(page));

        EnsureRazorPagesServices(endpoints);

        // Called for side-effect to make sure that the data source is registered.
        var pageDataSource = GetOrCreateDataSource(endpoints);
        pageDataSource.CreateInertEndpoints = true;
        RegisterInCache(endpoints.ServiceProvider, pageDataSource);

        // Maps a fallback endpoint with an empty delegate. This is OK because
        // we don't expect the delegate to run.
        var builder = endpoints.MapFallback(pattern, context => Task.CompletedTask);
        builder.Add(b =>
        {
            // MVC registers a policy that looks for this metadata.
            b.Metadata.Add(CreateDynamicPageMetadata(page, area: null));
            b.Metadata.Add(new PageEndpointDataSourceIdMetadata(pageDataSource.DataSourceId));
        });
        return builder;
    }

    /// <summary>
    /// Adds a specialized <see cref="RouteEndpoint"/> to the <see cref="IEndpointRouteBuilder"/> that will match
    /// requests for non-file-names with the lowest possible priority. The request will be routed to a page endpoint that
    /// matches <paramref name="page"/>, and <paramref name="area"/>.
    /// </summary>
    /// <param name="endpoints">The <see cref="IEndpointRouteBuilder"/> to add the route to.</param>
    /// <param name="page">The action name.</param>
    /// <param name="area">The area name.</param>
    /// <remarks>
    /// <para>
    /// <see cref="MapFallbackToAreaPage(IEndpointRouteBuilder, string, string)"/> is intended to handle cases where URL path of
    /// the request does not contain a file name, and no other endpoint has matched. This is convenient for routing
    /// requests for dynamic content to a SPA framework, while also allowing requests for non-existent files to
    /// result in an HTTP 404.
    /// </para>
    /// <para>
    /// <see cref="MapFallbackToAreaPage(IEndpointRouteBuilder, string, string)"/> registers an endpoint using the pattern
    /// <c>{*path:nonfile}</c>. The order of the registered endpoint will be <c>int.MaxValue</c>.
    /// </para>
    /// <para>
    /// <see cref="MapFallbackToAreaPage(IEndpointRouteBuilder, string, string)"/> does not re-execute routing, and will
    /// not generate route values based on routes defined elsewhere. When using this overload, the <c>path</c> route value
    /// will be available.
    /// </para>
    /// </remarks>
    public static IEndpointConventionBuilder MapFallbackToAreaPage(
        this IEndpointRouteBuilder endpoints,
        string page,
        string area)
    {
        ArgumentNullException.ThrowIfNull(endpoints);
        ArgumentNullException.ThrowIfNull(page);

        PageConventionCollection.EnsureValidPageName(page, nameof(page));

        EnsureRazorPagesServices(endpoints);

        // Called for side-effect to make sure that the data source is registered.
        var pageDataSource = GetOrCreateDataSource(endpoints);
        pageDataSource.CreateInertEndpoints = true;
        RegisterInCache(endpoints.ServiceProvider, pageDataSource);

        // Maps a fallback endpoint with an empty delegate. This is OK because
        // we don't expect the delegate to run.
        var builder = endpoints.MapFallback(context => Task.CompletedTask);
        builder.Add(b =>
        {
            // MVC registers a policy that looks for this metadata.
            b.Metadata.Add(CreateDynamicPageMetadata(page, area));
            b.Metadata.Add(new PageEndpointDataSourceIdMetadata(pageDataSource.DataSourceId));
        });
        return builder;
    }

    /// <summary>
    /// Adds a specialized <see cref="RouteEndpoint"/> to the <see cref="IEndpointRouteBuilder"/> that will match
    /// requests for non-file-names with the lowest possible priority. The request will be routed to a page endpoint that
    /// matches <paramref name="page"/>, and <paramref name="area"/>.
    /// </summary>
    /// <param name="endpoints">The <see cref="IEndpointRouteBuilder"/> to add the route to.</param>
    /// <param name="pattern">The route pattern.</param>
    /// <param name="page">The action name.</param>
    /// <param name="area">The area name.</param>
    /// <remarks>
    /// <para>
    /// <see cref="MapFallbackToAreaPage(IEndpointRouteBuilder, string, string, string)"/> is intended to handle cases where URL path of
    /// the request does not contain a file name, and no other endpoint has matched. This is convenient for routing
    /// requests for dynamic content to a SPA framework, while also allowing requests for non-existent files to
    /// result in an HTTP 404.
    /// </para>
    /// <para>
    /// The order of the registered endpoint will be <c>int.MaxValue</c>.
    /// </para>
    /// <para>
    /// This overload will use the provided <paramref name="pattern"/> verbatim. Use the <c>:nonfile</c> route contraint
    /// to exclude requests for static files.
    /// </para>
    /// <para>
    /// <see cref="MapFallbackToAreaPage(IEndpointRouteBuilder, string, string, string)"/> does not re-execute routing, and will
    /// not generate route values based on routes defined elsewhere. When using this overload, the route values provided by matching
    /// <paramref name="pattern"/> will be available.
    /// </para>
    /// </remarks>
    public static IEndpointConventionBuilder MapFallbackToAreaPage(
        this IEndpointRouteBuilder endpoints,
        [StringSyntax("Route")] string pattern,
        string page,
        string area)
    {
        ArgumentNullException.ThrowIfNull(endpoints);
        ArgumentNullException.ThrowIfNull(pattern);
        ArgumentNullException.ThrowIfNull(page);

        PageConventionCollection.EnsureValidPageName(page, nameof(page));

        EnsureRazorPagesServices(endpoints);

        // Called for side-effect to make sure that the data source is registered.
        var pageDataSource = GetOrCreateDataSource(endpoints);
        pageDataSource.CreateInertEndpoints = true;
        RegisterInCache(endpoints.ServiceProvider, pageDataSource);

        // Maps a fallback endpoint with an empty delegate. This is OK because
        // we don't expect the delegate to run.
        var builder = endpoints.MapFallback(pattern, context => Task.CompletedTask);
        builder.Add(b =>
        {
            // MVC registers a policy that looks for this metadata.
            b.Metadata.Add(CreateDynamicPageMetadata(page, area));
            b.Metadata.Add(new PageEndpointDataSourceIdMetadata(pageDataSource.DataSourceId));
        });
        return builder;
    }

    /// <summary>
    /// Adds a specialized <see cref="RouteEndpoint"/> to the <see cref="IEndpointRouteBuilder"/> that will
    /// attempt to select a page using the route values produced by <typeparamref name="TTransformer"/>.
    /// </summary>
    /// <param name="endpoints">The <see cref="IEndpointRouteBuilder"/> to add the route to.</param>
    /// <param name="pattern">The URL pattern of the route.</param>
    /// <typeparam name="TTransformer">The type of a <see cref="DynamicRouteValueTransformer"/>.</typeparam>
    /// <remarks>
    /// <para>
    /// This method allows the registration of a <see cref="RouteEndpoint"/> and <see cref="DynamicRouteValueTransformer"/>
    /// that combine to dynamically select a page using custom logic.
    /// </para>
    /// <para>
    /// The instance of <typeparamref name="TTransformer"/> will be retrieved from the dependency injection container.
    /// Register <typeparamref name="TTransformer"/> with the desired service lifetime in <c>ConfigureServices</c>.
    /// </para>
    /// </remarks>
    public static void MapDynamicPageRoute<TTransformer>(this IEndpointRouteBuilder endpoints, [StringSyntax("Route")] string pattern)
        where TTransformer : DynamicRouteValueTransformer
    {
        MapDynamicPageRoute<TTransformer>(endpoints, pattern, state: null);
    }

    /// <summary>
    /// Adds a specialized <see cref="RouteEndpoint"/> to the <see cref="IEndpointRouteBuilder"/> that will
    /// attempt to select a page using the route values produced by <typeparamref name="TTransformer"/>.
    /// </summary>
    /// <param name="endpoints">The <see cref="IEndpointRouteBuilder"/> to add the route to.</param>
    /// <param name="pattern">The URL pattern of the route.</param>
    /// <param name="state">A state object to provide to the <typeparamref name="TTransformer" /> instance.</param>
    /// <typeparam name="TTransformer">The type of a <see cref="DynamicRouteValueTransformer"/>.</typeparam>
    /// <remarks>
    /// <para>
    /// This method allows the registration of a <see cref="RouteEndpoint"/> and <see cref="DynamicRouteValueTransformer"/>
    /// that combine to dynamically select a page using custom logic.
    /// </para>
    /// <para>
    /// The instance of <typeparamref name="TTransformer"/> will be retrieved from the dependency injection container.
    /// Register <typeparamref name="TTransformer"/> with the desired service lifetime in <c>ConfigureServices</c>.
    /// </para>
    /// </remarks>
    public static void MapDynamicPageRoute<TTransformer>(this IEndpointRouteBuilder endpoints, [StringSyntax("Route")] string pattern, object? state)
        where TTransformer : DynamicRouteValueTransformer
    {
        ArgumentNullException.ThrowIfNull(endpoints);
        ArgumentNullException.ThrowIfNull(pattern);

        EnsureRazorPagesServices(endpoints);

        // Called for side-effect to make sure that the data source is registered.
        var pageDataSource = GetOrCreateDataSource(endpoints);
        RegisterInCache(endpoints.ServiceProvider, pageDataSource);

        pageDataSource.AddDynamicPageEndpoint(endpoints, pattern, typeof(TTransformer), state);
    }

    /// <summary>
    /// Adds a specialized <see cref="RouteEndpoint"/> to the <see cref="IEndpointRouteBuilder"/> that will
    /// attempt to select a page using the route values produced by <typeparamref name="TTransformer"/>.
    /// </summary>
    /// <param name="endpoints">The <see cref="IEndpointRouteBuilder"/> to add the route to.</param>
    /// <param name="pattern">The URL pattern of the route.</param>
    /// <param name="state">A state object to provide to the <typeparamref name="TTransformer" /> instance.</param>
    /// <param name="order">The matching order for the dynamic route.</param>
    /// <typeparam name="TTransformer">The type of a <see cref="DynamicRouteValueTransformer"/>.</typeparam>
    /// <remarks>
    /// <para>
    /// This method allows the registration of a <see cref="RouteEndpoint"/> and <see cref="DynamicRouteValueTransformer"/>
    /// that combine to dynamically select a page using custom logic.
    /// </para>
    /// <para>
    /// The instance of <typeparamref name="TTransformer"/> will be retrieved from the dependency injection container.
    /// Register <typeparamref name="TTransformer"/> with the desired service lifetime in <c>ConfigureServices</c>.
    /// </para>
    /// </remarks>
    public static void MapDynamicPageRoute<TTransformer>(this IEndpointRouteBuilder endpoints, [StringSyntax("Route")] string pattern, object state, int order)
        where TTransformer : DynamicRouteValueTransformer
    {
        ArgumentNullException.ThrowIfNull(endpoints);
        ArgumentNullException.ThrowIfNull(pattern);

        EnsureRazorPagesServices(endpoints);

        // Called for side-effect to make sure that the data source is registered.
        var pageDataSource = GetOrCreateDataSource(endpoints);
        RegisterInCache(endpoints.ServiceProvider, pageDataSource);

        pageDataSource.AddDynamicPageEndpoint(endpoints, pattern, typeof(TTransformer), state, order);
    }

    private static DynamicPageMetadata CreateDynamicPageMetadata(string page, string? area)
    {
        return new DynamicPageMetadata(new RouteValueDictionary()
            {
                { "page", page },
                { "area", area }
            });
    }

    private static void EnsureRazorPagesServices(IEndpointRouteBuilder endpoints)
    {
        var marker = endpoints.ServiceProvider.GetService<PageActionEndpointDataSourceFactory>();
        if (marker == null)
        {
            throw new InvalidOperationException(Mvc.Core.Resources.FormatUnableToFindServices(
                nameof(IServiceCollection),
                "AddRazorPages",
                "ConfigureServices(...)"));
        }
    }

    private static PageActionEndpointDataSource GetOrCreateDataSource(IEndpointRouteBuilder endpoints)
    {
        var dataSource = endpoints.DataSources.OfType<PageActionEndpointDataSource>().FirstOrDefault();
        if (dataSource == null)
        {
            var orderProviderCache = endpoints.ServiceProvider.GetRequiredService<OrderedEndpointsSequenceProviderCache>();
            var factory = endpoints.ServiceProvider.GetRequiredService<PageActionEndpointDataSourceFactory>();
            dataSource = factory.Create(orderProviderCache.GetOrCreateOrderedEndpointsSequenceProvider(endpoints));
            endpoints.DataSources.Add(dataSource);
        }

        return dataSource;
    }

    private static void RegisterInCache(IServiceProvider serviceProvider, PageActionEndpointDataSource dataSource)
    {
        var cache = serviceProvider.GetRequiredService<DynamicPageEndpointSelectorCache>();
        cache.AddDataSource(dataSource);
    }
}
