// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System;
using System.Net.Http;
using System.Threading.Tasks;
using Microsoft.Extensions.Http.Resilience.Internal;
using Microsoft.Shared.Diagnostics;
using Polly;
 
namespace Microsoft.Extensions.Http.Resilience.Routing.Internal;
 
/// <summary>
/// Adds routing support to an inner strategy.
/// </summary>
internal sealed class RoutingResilienceStrategy : ResilienceStrategy
{
    private readonly Func<RequestRoutingStrategy>? _provider;
 
    public RoutingResilienceStrategy(Func<RequestRoutingStrategy>? provider)
    {
        _provider = provider;
    }
 
    protected override async ValueTask<Outcome<TResult>> ExecuteCore<TResult, TState>(
        Func<ResilienceContext, TState, ValueTask<Outcome<TResult>>> callback,
        ResilienceContext context,
        TState state)
    {
        HttpRequestMessage? request = context.GetRequestMessage();
 
        if (request is null)
        {
            Throw.InvalidOperationException("The HTTP request message was not found in the resilience context.");
        }
 
        if (_provider is null)
        {
            return await callback(context, state).ConfigureAwait(context.ContinueOnCapturedContext);
        }
 
        using var strategy = _provider();
 
        // if there are not routes we cannot continue
        if (!strategy.TryGetNextRoute(out var route))
        {
            Throw.InvalidOperationException("The routing strategy did not provide any route URL on the first attempt.");
        }
 
        context.Properties.Set(ResilienceKeys.RoutingStrategy, strategy);
 
        // for primary request, use retrieved route
        request.RequestUri = request.RequestUri!.ReplaceHost(route!);
 
        return await callback(context, state).ConfigureAwait(context.ContinueOnCapturedContext);
    }
}