using System.Collections.Immutable;
using System.Text;
using Dpz.Core.SourceGenerator.Models;

namespace Dpz.Core.SourceGenerator;

/// <summary>
/// 根据服务注册元数据生成 Microsoft.Extensions.DependencyInjection 注册源码。
/// </summary>
internal static class ServiceRegistrationSourceBuilder
{
    internal static string Generate(ImmutableArray<ServiceRegistration> registrations)
    {
        var source = new StringBuilder();
        source.AppendLine("// <auto-generated />");
        source.AppendLine("#nullable enable");
        source.AppendLine();
        source.AppendLine("namespace Dpz.Core.Service;");
        source.AppendLine();
        source.AppendLine("internal static partial class GeneratedServiceRegistration");
        source.AppendLine("{");
        source.AppendLine(
            "    internal static global::Microsoft.Extensions.DependencyInjection.IServiceCollection AddGeneratedRepositoryServices("
        );
        source.AppendLine(
            "        this global::Microsoft.Extensions.DependencyInjection.IServiceCollection services"
        );
        source.AppendLine("    )");
        source.AppendLine("    {");

        foreach (var registration in registrations)
        {
            if (registration.Kind == RegistrationKind.HttpClient)
            {
                AppendHttpClientRegistration(source, registration);
                continue;
            }

            AppendServiceRegistration(source, registration);
        }

        source.AppendLine();
        source.AppendLine("        return services;");
        source.AppendLine("    }");
        source.AppendLine("}");
        return source.ToString();
    }

    private static void AppendServiceRegistration(
        StringBuilder source,
        ServiceRegistration registration
    )
    {
        if (registration.RequiresDecorator)
        {
            AppendLifetimeRegistration(
                source,
                registration.Lifetime,
                registration.ImplementationType
            );
            AppendLifetimeRegistration(
                source,
                registration.Lifetime,
                registration.ServiceType,
                registration.DecoratorType
            );
            return;
        }

        AppendLifetimeRegistration(
            source,
            registration.Lifetime,
            registration.ServiceType,
            registration.ImplementationType
        );
    }

    private static void AppendHttpClientRegistration(
        StringBuilder source,
        ServiceRegistration registration
    )
    {
        if (registration.RequiresDecorator)
        {
            source.Append(
                "        global::Microsoft.Extensions.DependencyInjection.HttpClientFactoryServiceCollectionExtensions.AddHttpClient<"
            );
            source.Append(registration.ImplementationType);
            AppendHttpClientOptions(source, registration);
            source.Append(
                "        global::Microsoft.Extensions.DependencyInjection.ServiceCollectionServiceExtensions.AddTransient<"
            );
            source.Append(registration.ServiceType);
            source.Append(", ");
            source.Append(registration.DecoratorType);
            source.AppendLine(">(services);");
            return;
        }

        source.Append(
            "        global::Microsoft.Extensions.DependencyInjection.HttpClientFactoryServiceCollectionExtensions.AddHttpClient<"
        );
        source.Append(registration.ServiceType);
        source.Append(", ");
        source.Append(registration.ImplementationType);
        AppendHttpClientOptions(source, registration);
    }

    private static void AppendLifetimeRegistration(
        StringBuilder source,
        ServiceLifetime lifetime,
        string serviceType
    )
    {
        source.Append(
            "        global::Microsoft.Extensions.DependencyInjection.ServiceCollectionServiceExtensions."
        );
        source.Append(GetLifetimeMethodName(lifetime));
        source.Append("<");
        source.Append(serviceType);
        source.AppendLine(">(services);");
    }

    private static void AppendLifetimeRegistration(
        StringBuilder source,
        ServiceLifetime lifetime,
        string serviceType,
        string implementationType
    )
    {
        source.Append(
            "        global::Microsoft.Extensions.DependencyInjection.ServiceCollectionServiceExtensions."
        );
        source.Append(GetLifetimeMethodName(lifetime));
        source.Append("<");
        source.Append(serviceType);
        source.Append(", ");
        source.Append(implementationType);
        source.AppendLine(">(services);");
    }

    private static void AppendHttpClientOptions(
        StringBuilder source,
        ServiceRegistration registration
    )
    {
        source.AppendLine(">(services, static (_, client) =>");
        source.AppendLine("        {");
        source.Append("            client.BaseAddress = new global::System.Uri(");
        source.Append(SymbolDisplay.ToCSharpStringLiteral(registration.BaseAddress!));
        source.AppendLine(");");

        if (registration.TimeoutSeconds > 0)
        {
            source.Append("            client.Timeout = global::System.TimeSpan.FromSeconds(");
            source.Append(registration.TimeoutSeconds);
            source.AppendLine(");");
        }

        source.AppendLine("        });");
    }

    private static string GetLifetimeMethodName(ServiceLifetime lifetime)
    {
        return lifetime == ServiceLifetime.Singleton ? "AddSingleton"
            : lifetime == ServiceLifetime.Transient ? "AddTransient"
            : "AddScoped";
    }
}