using System;
using System.Collections.Generic;
using System.IO;
using System.IO.Compression;
using System.Text;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using StellaOps.Signals.Models;

namespace StellaOps.Signals.Parsing;

internal static class RuntimeFactsNdjsonReader
{
    private static readonly JsonSerializerOptions SerializerOptions = new(JsonSerializerDefaults.Web);

    public static async Task<List<RuntimeFactEvent>> ReadAsync(
        Stream input,
        bool gzipEncoded,
        CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(input);

        Stream effectiveStream = input;
        if (gzipEncoded)
        {
            effectiveStream = new GZipStream(input, CompressionMode.Decompress, leaveOpen: true);
        }

        using var reader = new StreamReader(effectiveStream, Encoding.UTF8, detectEncodingFromByteOrderMarks: true, leaveOpen: !gzipEncoded);

        var events = new List<RuntimeFactEvent>();
        string? line;
        while ((line = await reader.ReadLineAsync(cancellationToken).ConfigureAwait(false)) != null)
        {
            if (string.IsNullOrWhiteSpace(line))
            {
                continue;
            }

            var evt = JsonSerializer.Deserialize<RuntimeFactEvent>(line, SerializerOptions);
            if (evt is null || string.IsNullOrWhiteSpace(evt.SymbolId))
            {
                continue;
            }

            events.Add(evt);
        }

        return events;
    }
}