using System;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

namespace GB5Shared.Deployment
{
    /// <summary>
    /// Registers the GB5 deployment-tier abstraction. Call in Program.cs:
    ///   builder.Services.AddGB5Environment(builder.Configuration);
    /// Bind the "GB5" section from appsettings.json or environment variables
    /// (e.g. GB5__Environment=Dev|QC|Live) — there is no safe default in production,
    /// so an unconfigured tier fails fast at boot rather than silently resolving as Dev.
    /// </summary>
    public static class GB5EnvironmentServiceExtensions
    {
        public static IServiceCollection AddGB5Environment(this IServiceCollection services, IConfiguration configuration)
        {
            var section = configuration.GetSection(GB5EnvironmentOptions.SectionName);

            if (!section.Exists() || string.IsNullOrWhiteSpace(section["Environment"]))
                throw new InvalidOperationException(
                    $"{GB5EnvironmentOptions.SectionName}:Environment must be set to Dev, QC, or Live.");

            if (!Enum.TryParse<GB5Tier>(section["Environment"], ignoreCase: true, out _))
                throw new InvalidOperationException(
                    $"{GB5EnvironmentOptions.SectionName}:Environment value '{section["Environment"]}' is not a valid GB5Tier (Dev, QC, Live).");

            services.Configure<GB5EnvironmentOptions>(section);
            services.AddSingleton<IGB5Environment, GB5Environment>();

            return services;
        }
    }
}