feat(datasync): add JsonZstdFileSource for reading zstd-compressed JSON files

NEW/src/JdeScoping.DataSync/Etl/Sources/JsonZstdFileSource.cs

@@ -0,0 +1,63 @@
+using System.Data;
+using JdeScoping.DataSync.Etl.Contracts;
+using JdeScoping.DataSync.Etl.Models;
+using ZstdSharp;
+
+namespace JdeScoping.DataSync.Etl.Sources;
+
+/// <summary>
+/// Import source that reads from a zstd-compressed JSON array file.
+/// </summary>
+public sealed class JsonZstdFileSource : IImportSource
+{
+    private readonly string _filePath;
+    private readonly JsonColumnSchema[] _schema;
+    private FileStream? _fileStream;
+    private DecompressionStream? _decompressionStream;
+    private JsonStreamingDataReader? _reader;
+
+    public string SourceName => $"JsonZstd:{Path.GetFileName(_filePath)}";
+
+    public JsonZstdFileSource(string filePath, JsonColumnSchema[] schema)
+    {
+        if (string.IsNullOrWhiteSpace(filePath))
+            throw new ArgumentException("File path cannot be null or empty.", nameof(filePath));
+
+        if (!File.Exists(filePath))
+            throw new FileNotFoundException($"Cache file not found: {filePath}", filePath);
+
+        _filePath = filePath;
+        _schema = schema ?? throw new ArgumentNullException(nameof(schema));
+    }
+
+    public Task<IDataReader> ReadDataAsync(CancellationToken cancellationToken = default)
+    {
+        _fileStream = new FileStream(_filePath, FileMode.Open, FileAccess.Read, FileShare.Read,
+            bufferSize: 65536, useAsync: true);
+        _decompressionStream = new DecompressionStream(_fileStream);
+        _reader = new JsonStreamingDataReader(_decompressionStream, _schema);
+
+        return Task.FromResult<IDataReader>(_reader);
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        if (_reader != null)
+        {
+            _reader.Dispose();
+            _reader = null;
+        }
+
+        if (_decompressionStream != null)
+        {
+            await _decompressionStream.DisposeAsync();
+            _decompressionStream = null;
+        }
+
+        if (_fileStream != null)
+        {
+            await _fileStream.DisposeAsync();
+            _fileStream = null;
+        }
+    }
+}