using IntelligenceApi.Engines.Franchisee;
using IntelligenceApi.Engines.Franchisor;
using IntelligenceApi.Engines.General;

namespace IntelligenceApi.Engines;

/// <summary>
/// Routes incoming spend distribution requests to the correct engine
/// based on clientCategory.
///
/// ADDING A NEW ENGINE:
///   1. Create a folder under Engines/ (e.g. Engines/FoodFranchisee/)
///   2. Implement ISpendDistributionEngine
///   3. Register in Program.cs
///   4. Add the category string to the routing table below
///
/// The General engine is the fallback for any unrecognised category,
/// ensuring existing clients are never broken by new category additions.
/// </summary>
public sealed class EngineRouter
{
    private readonly GeneralEngine _general;
    private readonly FranchiseeEngine _franchisee;
    private readonly FranchisorEngine _franchisor;
    private readonly ILogger<EngineRouter> _logger;

    public EngineRouter(
        GeneralEngine general,
        FranchiseeEngine franchisee,
        FranchisorEngine franchisor,
        ILogger<EngineRouter> logger)
    {
        _general    = general;
        _franchisee = franchisee;
        _franchisor = franchisor;
        _logger     = logger;
    }

    public ISpendDistributionEngine Resolve(string? clientCategory)
    {
        var engine = (clientCategory ?? "General").Trim() switch
        {
            // ── Exact category matches ──────────────────────────────
            "General"        => (ISpendDistributionEngine)_general,
            "Franchisee"     => _franchisee,
            "Franchisor"     => _franchisor,

            // ── Future sub-categories route to their parent stub
            //    until a dedicated engine is built.
            //    e.g. "FoodFranchisee" => _foodFranchisee (not yet registered)
            //    falls through to Franchisee as the nearest match.
            var c when c.EndsWith("Franchisee", StringComparison.OrdinalIgnoreCase)
                     => _franchisee,
            var c when c.EndsWith("Franchisor", StringComparison.OrdinalIgnoreCase)
                     => _franchisor,

            // ── Unknown / unrecognised — safe fallback ──────────────
            var c => LogAndFallback(c)
        };

        _logger.LogInformation(
            "[EngineRouter] Category={Category} → Engine={Engine}",
            clientCategory, engine.EngineName);

        return engine;
    }

    private ISpendDistributionEngine LogAndFallback(string category)
    {
        _logger.LogWarning(
            "[EngineRouter] Unrecognised category '{Category}' — falling back to GeneralEngine",
            category);
        return _general;
    }
}