using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using AI.Models.SpecialMessages;

namespace AI.Utils
{
    /// <summary>
    /// CSV 文件解析与预览表格构建
    /// </summary>
    public static class CsvPreviewHelper
    {
        /// <summary>
        /// 从 CSV 文件路径读取并构建预览表格消息，最多显示指定行数。
        /// </summary>
        /// <param name="path">CSV 文件路径</param>
        /// <param name="maxPreviewRows">最多预览行数，默认 20</param>
        /// <param name="title">表格标题，默认「散点文件预览」</param>
        /// <returns>成功返回 TableDataMessage，失败返回 null</returns>
        public static TableDataMessage? TryBuildCsvPreviewTable(string path, int maxPreviewRows = 20, string title = "散点文件预览")
        {
            if (string.IsNullOrWhiteSpace(path) || !File.Exists(path))
                return null;

            string[] lines;
            try
            {
                lines = File.ReadAllLines(path, Encoding.UTF8);
            }
            catch
            {
                try
                {
                    lines = File.ReadAllLines(path);
                }
                catch
                {
                    return null;
                }
            }

            if (lines.Length == 0)
            {
                return null;
            }

            var columnNames = ParseCsvLine(lines[0]);
            if (columnNames.Count == 0)
            {
                return null;
            }

            var table = new TableDataMessage
            {
                Title = title,
                MaxPreviewRows = maxPreviewRows,
            };

            var dataRows = new List<IEnumerable<string>>();
            for (int i = 1; i < lines.Length && dataRows.Count < maxPreviewRows; i++)
            {
                var cells = ParseCsvLine(lines[i]);
                while (cells.Count < columnNames.Count)
                {
                    cells.Add(string.Empty);
                }

                if (cells.Count > columnNames.Count)
                {
                    cells = cells.Take(columnNames.Count).ToList();
                }
                dataRows.Add(cells);
            }

            int totalRowCount = lines.Length - 1;
            table.SetData(columnNames, dataRows, totalRowCount);
            return table;
        }

        /// <summary>
        /// 简单解析 CSV 行：按逗号拆分，去除首尾空白，不处理引号内逗号。
        /// </summary>
        public static List<string> ParseCsvLine(string line)
        {
            if (string.IsNullOrEmpty(line))
                return new List<string>();
            return line.Split(',').Select(c => c.Trim()).ToList();
        }
    }
}