using Microsoft.Extensions.Logging;
using StellaOps.Provcache.Entities;
using System.Collections.Concurrent;
using System.Text.Json;

namespace StellaOps.Provcache;

/// <summary>
/// In-memory implementation of the revocation ledger for testing and non-persistent scenarios.
/// For production use, inject a PostgreSQL-backed implementation from StellaOps.Provcache.Postgres.
/// </summary>
public sealed class InMemoryRevocationLedger : IRevocationLedger
{
    private readonly ConcurrentDictionary<long, RevocationEntry> _entries = new();
    private readonly ILogger<InMemoryRevocationLedger> _logger;
    private long _currentSeqNo;

    public InMemoryRevocationLedger(ILogger<InMemoryRevocationLedger> logger)
    {
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    /// <inheritdoc />
    public Task<RevocationEntry> RecordAsync(
        RevocationEntry entry,
        CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(entry);

        var seqNo = Interlocked.Increment(ref _currentSeqNo);
        var recordedEntry = entry with { SeqNo = seqNo };
        
        _entries[seqNo] = recordedEntry;

        _logger.LogInformation(
            "Recorded revocation {RevocationId} of type {Type} for key {Key}, invalidated {Count} entries",
            entry.RevocationId, entry.RevocationType, entry.RevokedKey, entry.EntriesInvalidated);

        return Task.FromResult(recordedEntry);
    }

    /// <inheritdoc />
    public Task<IReadOnlyList<RevocationEntry>> GetEntriesSinceAsync(
        long sinceSeqNo,
        int limit = 1000,
        CancellationToken cancellationToken = default)
    {
        var entries = _entries.Values
            .Where(e => e.SeqNo > sinceSeqNo)
            .OrderBy(e => e.SeqNo)
            .Take(limit)
            .ToList();

        return Task.FromResult<IReadOnlyList<RevocationEntry>>(entries);
    }

    /// <inheritdoc />
    public Task<IReadOnlyList<RevocationEntry>> GetEntriesByTypeAsync(
        string revocationType,
        DateTimeOffset? since = null,
        int limit = 1000,
        CancellationToken cancellationToken = default)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(revocationType);

        var query = _entries.Values
            .Where(e => e.RevocationType == revocationType);

        if (since.HasValue)
        {
            query = query.Where(e => e.RevokedAt > since.Value);
        }

        var entries = query
            .OrderBy(e => e.SeqNo)
            .Take(limit)
            .ToList();

        return Task.FromResult<IReadOnlyList<RevocationEntry>>(entries);
    }

    /// <inheritdoc />
    public Task<long> GetLatestSeqNoAsync(CancellationToken cancellationToken = default)
    {
        return Task.FromResult(Interlocked.Read(ref _currentSeqNo));
    }

    /// <inheritdoc />
    public Task<IReadOnlyList<RevocationEntry>> GetRevocationsForKeyAsync(
        string revokedKey,
        CancellationToken cancellationToken = default)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(revokedKey);

        var entries = _entries.Values
            .Where(e => e.RevokedKey == revokedKey)
            .OrderBy(e => e.SeqNo)
            .ToList();

        return Task.FromResult<IReadOnlyList<RevocationEntry>>(entries);
    }

    /// <inheritdoc />
    public Task<RevocationLedgerStats> GetStatsAsync(CancellationToken cancellationToken = default)
    {
        var allEntries = _entries.Values.ToList();
        var totalEntries = allEntries.Count;
        var latestSeqNo = Interlocked.Read(ref _currentSeqNo);
        var totalInvalidated = allEntries.Sum(e => (long)e.EntriesInvalidated);

        var entriesByType = allEntries
            .GroupBy(e => e.RevocationType)
            .ToDictionary(g => g.Key, g => (long)g.Count());

        var oldestEntry = allEntries.MinBy(e => e.SeqNo)?.RevokedAt;
        var newestEntry = allEntries.MaxBy(e => e.SeqNo)?.RevokedAt;

        return Task.FromResult(new RevocationLedgerStats
        {
            TotalEntries = totalEntries,
            LatestSeqNo = latestSeqNo,
            EntriesByType = entriesByType,
            TotalEntriesInvalidated = totalInvalidated,
            OldestEntryAt = oldestEntry,
            NewestEntryAt = newestEntry
        });
    }

    /// <summary>
    /// Clears all entries (for testing).
    /// </summary>
    public void Clear()
    {
        _entries.Clear();
        Interlocked.Exchange(ref _currentSeqNo, 0);
    }
}