using StellaOps.AirGap.Controller.Domain;
using StellaOps.AirGap.Controller.Stores;
using StellaOps.AirGap.Time.Models;
using StellaOps.AirGap.Time.Services;

namespace StellaOps.AirGap.Controller.Services;

public sealed class AirGapStateService
{
    private readonly IAirGapStateStore _store;
    private readonly StalenessCalculator _stalenessCalculator;

    public AirGapStateService(IAirGapStateStore store, StalenessCalculator stalenessCalculator)
    {
        _store = store;
        _stalenessCalculator = stalenessCalculator;
    }

    public async Task<AirGapState> SealAsync(
        string tenantId,
        string policyHash,
        TimeAnchor timeAnchor,
        StalenessBudget budget,
        DateTimeOffset nowUtc,
        CancellationToken cancellationToken = default)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(policyHash);
        budget.Validate();

        var newState = new AirGapState
        {
            TenantId = tenantId,
            Sealed = true,
            PolicyHash = policyHash,
            TimeAnchor = timeAnchor,
            StalenessBudget = budget,
            LastTransitionAt = nowUtc
        };

        await _store.SetAsync(newState, cancellationToken);
        return newState;
    }

    public async Task<AirGapState> UnsealAsync(
        string tenantId,
        DateTimeOffset nowUtc,
        CancellationToken cancellationToken = default)
    {
        var current = await _store.GetAsync(tenantId, cancellationToken);
        var newState = current with
        {
            Sealed = false,
            LastTransitionAt = nowUtc
        };
        await _store.SetAsync(newState, cancellationToken);
        return newState;
    }

    public async Task<AirGapStatus> GetStatusAsync(
        string tenantId,
        DateTimeOffset nowUtc,
        CancellationToken cancellationToken = default)
    {
        var state = await _store.GetAsync(tenantId, cancellationToken);
        var staleness = _stalenessCalculator.Evaluate(state.TimeAnchor, state.StalenessBudget, nowUtc);
        return new AirGapStatus(state, staleness, nowUtc);
    }
}

public sealed record AirGapStatus(AirGapState State, StalenessEvaluation Staleness, DateTimeOffset EvaluatedAt);