using System.Collections.Immutable;
using System.Text.Json.Nodes;
using MongoDB.Bson;
using MongoDB.Driver;
using StellaOps.Graph.Indexer.Infrastructure;

namespace StellaOps.Graph.Indexer.Analytics;

public sealed class MongoGraphSnapshotProvider : IGraphSnapshotProvider
{
    private readonly IMongoCollection<BsonDocument> _snapshots;
    private readonly IMongoCollection<BsonDocument> _progress;
    private readonly MongoGraphSnapshotProviderOptions _options;

    public MongoGraphSnapshotProvider(IMongoDatabase database, MongoGraphSnapshotProviderOptions? options = null)
    {
        ArgumentNullException.ThrowIfNull(database);
        _options = options ?? new MongoGraphSnapshotProviderOptions();
        _snapshots = database.GetCollection<BsonDocument>(_options.SnapshotCollectionName);
        _progress = database.GetCollection<BsonDocument>(_options.ProgressCollectionName);
    }

    public async Task<IReadOnlyList<GraphAnalyticsSnapshot>> GetPendingSnapshotsAsync(CancellationToken cancellationToken)
    {
        cancellationToken.ThrowIfCancellationRequested();

        var processedIds = await _progress
            .Find(FilterDefinition<BsonDocument>.Empty)
            .Project(doc => doc["snapshot_id"].AsString)
            .ToListAsync(cancellationToken)
            .ConfigureAwait(false);

        var filter = Builders<BsonDocument>.Filter.Nin("snapshot_id", processedIds);
        var snapshots = await _snapshots
            .Find(filter)
            .Limit(_options.MaxBatch)
            .Sort(Builders<BsonDocument>.Sort.Descending("generated_at"))
            .ToListAsync(cancellationToken)
            .ConfigureAwait(false);

        var result = new List<GraphAnalyticsSnapshot>(snapshots.Count);
        foreach (var snapshot in snapshots)
        {
            var tenant = snapshot.GetValue("tenant", string.Empty).AsString;
            var snapshotId = snapshot.GetValue("snapshot_id", string.Empty).AsString;
            var generatedAt = snapshot.TryGetValue("generated_at", out var generated)
                              && generated.BsonType == BsonType.DateTime
                ? DateTime.SpecifyKind(generated.ToUniversalTime(), DateTimeKind.Utc)
                : DateTimeOffset.UtcNow;

            var nodes = snapshot.TryGetValue("nodes", out var nodesValue) && nodesValue is BsonArray nodesArray
                ? BsonJsonConverter.ToJsonArray(nodesArray).Select(n => (JsonObject)n!).ToImmutableArray()
                : ImmutableArray<JsonObject>.Empty;

            var edges = snapshot.TryGetValue("edges", out var edgesValue) && edgesValue is BsonArray edgesArray
                ? BsonJsonConverter.ToJsonArray(edgesArray).Select(n => (JsonObject)n!).ToImmutableArray()
                : ImmutableArray<JsonObject>.Empty;

            result.Add(new GraphAnalyticsSnapshot(tenant, snapshotId, generatedAt, nodes, edges));
        }

        return result;
    }

    public async Task MarkProcessedAsync(string tenant, string snapshotId, CancellationToken cancellationToken)
    {
        cancellationToken.ThrowIfCancellationRequested();

        var filter = Builders<BsonDocument>.Filter.Eq("snapshot_id", snapshotId)
                     & Builders<BsonDocument>.Filter.Eq("tenant", tenant);

        var update = Builders<BsonDocument>.Update.Set("snapshot_id", snapshotId)
            .Set("tenant", tenant)
            .SetOnInsert("processed_at", DateTimeOffset.UtcNow.UtcDateTime);

        await _progress.UpdateOneAsync(filter, update, new UpdateOptions { IsUpsert = true }, cancellationToken)
            .ConfigureAwait(false);
    }
}