using System.Collections.Immutable;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
using StellaOps.PolicyDsl;
using StellaOps.Policy.Engine.Evaluation;

namespace StellaOps.Policy.Engine.Services;

internal sealed partial class PolicyEvaluationService
{
    private readonly PolicyEvaluator _evaluator;
    private readonly PathScopeMetrics _pathMetrics;
    private readonly ILogger<PolicyEvaluationService> _logger;

    public PolicyEvaluationService()
        : this(new PathScopeMetrics(), NullLogger<PolicyEvaluationService>.Instance, new PolicyEvaluator())
    {
    }

    public PolicyEvaluationService(PathScopeMetrics pathMetrics, ILogger<PolicyEvaluationService> logger, PolicyEvaluator evaluator)
    {
        _pathMetrics = pathMetrics ?? throw new ArgumentNullException(nameof(pathMetrics));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
        _evaluator = evaluator ?? throw new ArgumentNullException(nameof(evaluator));
    }

    internal Evaluation.PolicyEvaluationResult Evaluate(PolicyIrDocument document, Evaluation.PolicyEvaluationContext context)
    {
        if (document is null)
        {
            throw new ArgumentNullException(nameof(document));
        }

        if (context is null)
        {
            throw new ArgumentNullException(nameof(context));
        }

        var request = new Evaluation.PolicyEvaluationRequest(document, context);
        return _evaluator.Evaluate(request);
    }

    // PathScopeSimulationService partial class relies on _pathMetrics.
}