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

namespace AltBot.ServiceDefaults;

// Adds common .NET Aspire services: service discovery, resilience, health checks, and OpenTelemetry.
// This project should be referenced by each service project in your solution.
// To learn more about using this project, see https://aka.ms/dotnet/aspire/service-defaults
public static class StartupExtensions
{
    private const string HealthEndpointPath = "/health";
    private const string AlivenessEndpointPath = "/alive";

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

        builder.AddDefaultHealthChecks();

        builder.Services.AddExceptionHandler<HaltExceptionHandler>();
        builder.Services.AddExceptionHandler<GlobalExceptionHandler>();

        builder.Services.AddServiceDiscovery();

        builder.Services.ConfigureHttpClientDefaults(http =>
        {
            // Turn on resilience by default
            http.AddStandardResilienceHandler();

            // Turn on service discovery by default
            http.AddServiceDiscovery();
        });
        
        return builder;
    }

    private static TBuilder ConfigureSerilog<TBuilder>(this TBuilder builder) where TBuilder : IHostApplicationBuilder
    {
        // Create Serilog logger configuration
        var loggerConfiguration = new LoggerConfiguration()
            .ReadFrom.Configuration(builder.Configuration)
            .MinimumLevel.Information()
            .MinimumLevel.Override("Microsoft", LogEventLevel.Warning)
            .MinimumLevel.Override("System", LogEventLevel.Warning)
            .Enrich.FromLogContext()
            .Enrich.WithEnvironmentName()
            .Enrich.WithThreadId();

        // Add console sink in development
        if (builder.Environment.IsDevelopment())
        {
            loggerConfiguration
                .WriteTo.Console()
                .WriteTo.Debug();
        }
        else
        {
            loggerConfiguration
                .WriteTo.Console();
        }

        // Create logger
        Log.Logger = loggerConfiguration.CreateLogger();

        // Configure application to use Serilog
        builder.Logging.AddSerilog(dispose: true);

        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 =>
                        // Exclude health check requests from 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()
            // Add a default liveness check to ensure app is responsive
            .AddCheck("self", () => HealthCheckResult.Healthy(), ["live"]);

        return builder;
    }

    public static WebApplication MapDefaultEndpoints(this WebApplication app)
    {
        // Adding health checks endpoints to applications in non-development environments has security implications.
        // See https://aka.ms/dotnet/aspire/healthchecks for details before enabling these endpoints in non-development environments.
        if (app.Environment.IsDevelopment())
        {
            // All health checks must pass for app to be considered ready to accept traffic after starting
            app.MapHealthChecks(HealthEndpointPath);

            // Only health checks tagged with the "live" tag must pass for app to be considered alive
            app.MapHealthChecks(AlivenessEndpointPath, new HealthCheckOptions
            {
                Predicate = r => r.Tags.Contains("live")
            });
        }

        return app;
    }
}