using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Diagnostics.HealthChecks;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Diagnostics.HealthChecks;
using Microsoft.Extensions.Logging;
using OpenTelemetry;
using OpenTelemetry.Metrics;
using OpenTelemetry.Trace;

namespace Microsoft.Extensions.Hosting;

public static class Extensions
{
    private const string HealthEndpointPath = "/health";
    private const string AlivenessEndpointPath = "/alive";

    public static TBuilder AddServiceDefaults<TBuilder>(this TBuilder builder)
        where TBuilder : IHostApplicationBuilder
    {
        builder.ConfigureOpenTelemetry();

        builder.AddDefaultHealthChecks();

        builder.Services.AddServiceDiscovery();

        builder.Services.ConfigureHttpClientDefaults(http =>
        {
            http.AddStandardResilienceHandler();
            http.ConfigureHttpClient(httpClient =>
            {
                httpClient.DefaultRequestHeaders.UserAgent.ParseAdd("MSearch");
            });
        });

        return builder;
    }

    public static TBuilder ConfigureOpenTelemetry<TBuilder>(this TBuilder builder)
        where TBuilder : IHostApplicationBuilder
    {
        builder.Logging.AddOpenTelemetry(logging =>
        {
            logging.IncludeFormattedMessage = true;
            logging.IncludeScopes = true;
        });

        builder
            .Services.AddOpenTelemetry()
            .WithMetrics(metrics =>
                metrics.AddAspNetCoreInstrumentation().AddHttpClientInstrumentation().AddRuntimeInstrumentation()
            )
            .WithTracing(tracing =>
                tracing
                    .AddSource(builder.Environment.ApplicationName)
                    .AddAspNetCoreInstrumentation(tracing =>
                        tracing.Filter = context =>
                            !context.Request.Path.StartsWithSegments(HealthEndpointPath)
                            && !context.Request.Path.StartsWithSegments(AlivenessEndpointPath)
                    )
                    .AddHttpClientInstrumentation()
            );

        builder.AddOpenTelemetryExporters();

        return builder;
    }

    private static TBuilder AddOpenTelemetryExporters<TBuilder>(this TBuilder builder)
        where TBuilder : IHostApplicationBuilder
    {
        var useOtlpExporter = !string.IsNullOrWhiteSpace(builder.Configuration["OTEL_EXPORTER_OTLP_ENDPOINT"]);

        if (useOtlpExporter)
        {
            builder.Services.AddOpenTelemetry().UseOtlpExporter();
        }

        return builder;
    }

    public static TBuilder AddDefaultHealthChecks<TBuilder>(this TBuilder builder)
        where TBuilder : IHostApplicationBuilder
    {
        builder.Services.AddHealthChecks().AddCheck("self", () => HealthCheckResult.Healthy(), ["live"]);

        return builder;
    }

    public static WebApplication MapDefaultEndpoints(this WebApplication app)
    {
        app.MapHealthChecks(HealthEndpointPath);

        app.MapHealthChecks(AlivenessEndpointPath, new HealthCheckOptions { Predicate = r => r.Tags.Contains("live") });

        return app;
    }
}