using System.Collections.Concurrent;

namespace w4c_workflows.Services;

/// <summary>
/// In-memory lease service for lite/self-hosted mode where Redis is not available.
/// Uses a ConcurrentDictionary with TTL tracking. Not distributed — only works
/// for a single-process deployment (which is the lite mode use case).
/// </summary>
public sealed class InMemoryLeaseService : ILeaseService
{
    private record Lease(string Owner, DateTime ExpiresAt);

    private readonly ConcurrentDictionary<string, Lease> _leases = new();

    public Task<bool> AcquireAsync(string tenantId, string runId, string owner, TimeSpan ttl)
    {
        var key = $"{tenantId}:{runId}";
        var lease = new Lease(owner, DateTime.UtcNow + ttl);
        return Task.FromResult(_leases.TryAdd(key, lease));
    }

    public Task<bool> RenewAsync(string tenantId, string runId, string owner, TimeSpan ttl)
    {
        var key = $"{tenantId}:{runId}";
        if (!_leases.TryGetValue(key, out var current) || current.Owner != owner)
            return Task.FromResult(false);
        _leases[key] = new Lease(owner, DateTime.UtcNow + ttl);
        return Task.FromResult(true);
    }

    public Task<bool> ReleaseAsync(string tenantId, string runId, string owner)
    {
        var key = $"{tenantId}:{runId}";
        // Remove only if the owner still matches (compare-and-delete).
        return Task.FromResult(_leases.TryRemove(key, out var lease) && lease.Owner == owner);
    }
}