using System.Data;
using System.Text.Json;
using ProtoBuf.Data;
using ZstdSharp;

if (args.Length == 0)
{
    Console.WriteLine("Usage: CacheConverter <cache-directory>");
    Console.WriteLine("Example: dotnet run -- ../../CACHED_DB_FILES");
    return 1;
}

var cacheDir = args[0];
if (!Directory.Exists(cacheDir))
{
    Console.WriteLine($"Error: Directory not found: {cacheDir}");
    return 1;
}

var jsonFiles = Directory.GetFiles(cacheDir, "*.json.zstd");
Console.WriteLine($"Found {jsonFiles.Length} JSON files to convert");

long totalOriginalSize = 0;
long totalNewSize = 0;

foreach (var jsonFile in jsonFiles)
{
    var baseName = Path.GetFileName(jsonFile).Replace(".json.zstd", "");
    var outputFile = Path.Combine(cacheDir, $"{baseName}.pb.zstd");

    Console.Write($"Converting {baseName}... ");

    try
    {
        var originalSize = new FileInfo(jsonFile).Length;
        totalOriginalSize += originalSize;

        // Read and decompress JSON
        using var inputFs = new FileStream(jsonFile, FileMode.Open, FileAccess.Read, FileShare.Read, 256 * 1024, FileOptions.SequentialScan);
        using var decompressStream = new DecompressionStream(inputFs);
        using var bufferedInput = new BufferedStream(decompressStream, 256 * 1024);

        // Parse JSON array into list of dictionaries
        var jsonOptions = new JsonSerializerOptions { PropertyNameCaseInsensitive = true };
        var records = JsonSerializer.Deserialize<List<Dictionary<string, JsonElement>>>(bufferedInput, jsonOptions)
            ?? throw new InvalidDataException("Failed to parse JSON array");

        if (records.Count == 0)
        {
            Console.WriteLine("SKIP (empty)");
            continue;
        }

        // Create DataTable from records
        var dataTable = CreateDataTable(records);

        // Write protobuf with zstd compression
        using var outputFs = new FileStream(outputFile, FileMode.Create, FileAccess.Write, FileShare.None, 256 * 1024);
        using var compressStream = new CompressionStream(outputFs, level: 3);
        using var reader = dataTable.CreateDataReader();
        DataSerializer.Serialize(compressStream, reader);
        compressStream.Flush();

        var newSize = new FileInfo(outputFile).Length;
        totalNewSize += newSize;

        var ratio = (double)newSize / originalSize * 100;
        Console.WriteLine($"OK ({originalSize:N0} -> {newSize:N0} bytes, {ratio:F1}%)");
    }
    catch (Exception ex)
    {
        Console.WriteLine($"ERROR: {ex.Message}");
    }
}

Console.WriteLine();
if (totalOriginalSize > 0)
{
    Console.WriteLine($"Total: {totalOriginalSize:N0} -> {totalNewSize:N0} bytes ({(double)totalNewSize / totalOriginalSize * 100:F1}%)");
}
else
{
    Console.WriteLine("No files were converted.");
}
return 0;

static DataTable CreateDataTable(List<Dictionary<string, JsonElement>> records)
{
    var dt = new DataTable();
    var firstRecord = records[0];

    // Infer column types from first record
    foreach (var (key, value) in firstRecord)
    {
        var colType = InferType(value);
        dt.Columns.Add(key, colType);
    }

    // Add all rows
    foreach (var record in records)
    {
        var row = dt.NewRow();
        foreach (DataColumn col in dt.Columns)
        {
            if (record.TryGetValue(col.ColumnName, out var value))
            {
                row[col] = ConvertValue(value, col.DataType);
            }
            else
            {
                row[col] = DBNull.Value;
            }
        }
        dt.Rows.Add(row);
    }

    return dt;
}

static Type InferType(JsonElement element) => element.ValueKind switch
{
    JsonValueKind.String when element.GetString() is string s && DateTime.TryParse(s, out _) => typeof(DateTime),
    JsonValueKind.String => typeof(string),
    JsonValueKind.Number when element.TryGetInt64(out _) => typeof(long),
    JsonValueKind.Number => typeof(decimal),
    JsonValueKind.True or JsonValueKind.False => typeof(bool),
    JsonValueKind.Null => typeof(string), // Default nullable to string
    _ => typeof(string)
};

static object ConvertValue(JsonElement element, Type targetType)
{
    if (element.ValueKind == JsonValueKind.Null)
        return DBNull.Value;

    if (targetType == typeof(string))
        return (object?)element.GetString() ?? DBNull.Value;

    if (targetType == typeof(DateTime))
    {
        var str = element.GetString();
        if (str != null && DateTime.TryParse(str, out var dt))
            return dt;
        return DBNull.Value;
    }

    if (targetType == typeof(long))
        return element.GetInt64();

    if (targetType == typeof(decimal))
        return element.GetDecimal();

    if (targetType == typeof(bool))
        return element.GetBoolean();

    return (object?)element.GetString() ?? DBNull.Value;
}