qdr.app.studiou.orders2printpack/App/Extensions/CsvParserUtility.cs

using System.Text;
using System.Reflection;
using System.Globalization;

namespace qdr.app.studiou.orders2printpack.Extensions
{
    [AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
    public class CsvColumnAttribute : Attribute
    {
        public string Name { get; }
        public int Index { get; set; }

        public CsvColumnAttribute(string name)
        {
            Name = name;
            Index = -1; // Default to -1 to indicate that index is not set
        }
    }

    public class CsvParser
    {
        public static IEnumerable<TClass> Parse<TClass>(string filePath, bool hasHeaderRow = true, string delimiter = ",")
            where TClass : new()
        {
            using (var reader = new StreamReader(filePath))
            {
                var properties = typeof(TClass).GetProperties()
                    .Where(p => p.GetCustomAttribute<CsvColumnAttribute>() != null)
                    .ToList();

                string[]? headers = null;
                if (hasHeaderRow)
                {
                    var headerLine = reader.ReadLine();
                    headers = ParseCsvLine(headerLine, delimiter);
                }

                while (!reader.EndOfStream)
                {
                    var line = reader.ReadLine();
                    var values = ParseCsvLine(line, delimiter);

                    if (values == null || values.Length == 0)
                        continue;

                    var item = new TClass();

                    foreach (var prop in properties)
                    {
                        var attr = prop.GetCustomAttribute<CsvColumnAttribute>();
                        int? index = attr?.Index;

                        if ((index == null || index == -1) && headers != null)
                        {
                            index = Array.IndexOf(headers, attr?.Name);
                        }

                        if (index != null && index != -1 && index < values.Length)
                        {
                            SetPropertyValue(item, prop, values[index.Value]);
                        }
                    }

                    yield return item;
                }
            }
        }

        public static void Save<TClass>(IEnumerable<TClass> data, string filePath, bool includeHeader = true, string delimiter = ",")
        {
            var properties = typeof(TClass).GetProperties()
                .Where(p => p.GetCustomAttribute<CsvColumnAttribute>() != null)
                .OrderBy(p => p?.GetCustomAttribute<CsvColumnAttribute>()?.Index)
                .ToList();

            using (var writer = new StreamWriter(filePath, false, Encoding.UTF8))
            {
                // Write header
                if (includeHeader)
                {
                    var headerLine = string.Join(delimiter.ToString(), properties.Select(p => QuoteField(p?.GetCustomAttribute<CsvColumnAttribute>()?.Name)));
                    writer.WriteLine(headerLine);
                }

                // Write data
                foreach (var item in data)
                {
                    var line = new StringBuilder();
                    foreach (var prop in properties)
                    {
                        if (line.Length > 0)
                            line.Append(delimiter);

                        var value = prop.GetValue(item);
                        line.Append(QuoteField(FormatValue(value)));
                    }
                    writer.WriteLine(line.ToString());
                }
            }
        }

        /// <summary>
        /// Parses a single CSV line, handling quoted values and delimiters within quotes.
        /// </summary>
        /// <param name="line">The CSV line to parse.</param>
        /// <param name="delimiter">The delimiter used in the CSV line.</param>
        /// <returns>An array of field values.</returns>
        private static string[]? ParseCsvLine(string? line, string delimiter)
        {
            if (string.IsNullOrEmpty(line))
                return null;

            var result = new List<string>();
            var currentField = new StringBuilder();
            bool inQuotes = false;

            for (int i = 0; i < line.Length; i++)
            {
                if (inQuotes)
                {
                    if (line[i] == '"' && (i + 1 == line.Length || line[i + 1] != '"'))
                    {
                        // End of quoted field
                        inQuotes = false;
                    }
                    else if (line[i] == '"' && i + 1 < line.Length && line[i + 1] == '"')
                    {
                        // Escaped quote
                        currentField.Append('"');
                        i++; // Skip next quote
                    }
                    else
                    {
                        currentField.Append(line[i]);
                    }
                }
                else
                {
                    if (line[i] == '"')
                    {
                        inQuotes = true;
                    }
                    else if (line.Substring(i).StartsWith(delimiter))
                    {
                        result.Add(currentField.ToString().Trim());
                        currentField.Clear();
                        i += delimiter.Length - 1; // Skip the rest of the delimiter
                    }
                    else
                    {
                        currentField.Append(line[i]);
                    }
                }
            }

            result.Add(currentField.ToString().Trim());
            return result.ToArray();
        }

        private static void SetPropertyValue(object obj, PropertyInfo prop, string value)
        {
            if (string.IsNullOrWhiteSpace(value))
                return;

            try
            {
                object convertedValue;
                if (prop.PropertyType == typeof(string))
                {
                    convertedValue = value;
                }
                else if (prop.PropertyType == typeof(int))
                {
                    convertedValue = int.Parse(value);
                }
                else if (prop.PropertyType == typeof(double))
                {
                    convertedValue = double.Parse(value, CultureInfo.InvariantCulture);
                }
                else if (prop.PropertyType == typeof(DateTime))
                {
                    convertedValue = DateTime.Parse(value);
                }
                else if (prop.PropertyType == typeof(bool))
                {
                    convertedValue = bool.Parse(value);
                }
                else
                {
                    convertedValue = Convert.ChangeType(value, prop.PropertyType);
                }

                prop.SetValue(obj, convertedValue);
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Error setting property {prop.Name}: {ex.Message}");
            }
        }

        private static string? FormatValue(object? value)
        {
            if (value == null)
                return string.Empty;

            if (value is DateTime dateTime)
                return dateTime.ToString("yyyy-MM-dd HH:mm:ss");

            if (value is IFormattable formattable)
                return formattable.ToString(null, CultureInfo.InvariantCulture);

            return value?.ToString();
        }

        private static string EscapeField(string? field)
        {
            if (string.IsNullOrEmpty(field))
                return string.Empty;

            bool needsQuoting = field.Contains(',') || field.Contains('"') || field.Contains('\n');
            if (!needsQuoting)
                return field;

            return QuoteField(field);
        }
        private static string QuoteField(string? field)
        {
            if (string.IsNullOrEmpty(field))
                return "\"\"";

            return $"\"{field.Replace("\"", "\"\"")}\"";
        }
    }
}