using System.IO;
using System.Text;
using SharepointToolbox.Core.Models;

namespace SharepointToolbox.Services.Export;

/// <summary>
/// Exports SearchResult list to a UTF-8 BOM CSV file.
/// Header matches the column order in SearchHtmlExportService for consistency.
/// </summary>
public class SearchCsvExportService
{
    public string BuildCsv(IReadOnlyList<SearchResult> results)
    {
        var sb = new StringBuilder();

        // Header
        sb.AppendLine("File Name,Extension,Path,Created,Created By,Modified,Modified By,Size (bytes)");

        foreach (var r in results)
        {
            sb.AppendLine(string.Join(",",
                Csv(IfEmpty(System.IO.Path.GetFileName(r.Path), r.Title)),
                Csv(r.FileExtension),
                Csv(r.Path),
                r.Created.HasValue      ? Csv(r.Created.Value.ToString("yyyy-MM-dd"))      : string.Empty,
                Csv(r.Author),
                r.LastModified.HasValue ? Csv(r.LastModified.Value.ToString("yyyy-MM-dd")) : string.Empty,
                Csv(r.ModifiedBy),
                r.SizeBytes.ToString()));
        }

        return sb.ToString();
    }

    public async Task WriteAsync(IReadOnlyList<SearchResult> results, string filePath, CancellationToken ct)
    {
        var csv = BuildCsv(results);
        await System.IO.File.WriteAllTextAsync(filePath, csv, new UTF8Encoding(encoderShouldEmitUTF8Identifier: true), ct);
    }

    private static string Csv(string value)
    {
        if (string.IsNullOrEmpty(value)) return string.Empty;
        if (value.Contains(',') || value.Contains('"') || value.Contains('\n'))
            return $"\"{value.Replace("\"", "\"\"")}\"";
        return value;
    }

    private static string IfEmpty(string? value, string fallback = "")
        => string.IsNullOrEmpty(value) ? fallback : value!;
}