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

namespace SharepointToolbox.Services.Export;

/// <summary>
/// Exports DuplicateGroup list to CSV. Each duplicate item becomes one row;
/// the Group column ties copies together and a Copies column gives the group size.
/// Header row is built at write-time so culture switches are honoured.
/// </summary>
public class DuplicatesCsvExportService
{
    public async Task WriteAsync(
        IReadOnlyList<DuplicateGroup> groups,
        string filePath,
        CancellationToken ct)
    {
        var T = TranslationSource.Instance;
        var sb = new StringBuilder();

        // Summary
        sb.AppendLine($"\"{T["report.title.duplicates_short"]}\"");
        sb.AppendLine($"\"{T["report.text.duplicate_groups_found"]}\",\"{groups.Count}\"");
        sb.AppendLine($"\"{T["report.text.generated"]}\",\"{DateTime.Now:yyyy-MM-dd HH:mm:ss}\"");
        sb.AppendLine();

        // Header
        sb.AppendLine(string.Join(",", new[]
        {
            Csv(T["report.col.number"]),
            Csv("Group"),
            Csv(T["report.text.copies"]),
            Csv(T["report.col.name"]),
            Csv(T["report.col.library"]),
            Csv(T["report.col.path"]),
            Csv(T["report.col.size_bytes"]),
            Csv(T["report.col.created"]),
            Csv(T["report.col.modified"]),
        }));

        // Rows
        foreach (var g in groups)
        {
            int i = 0;
            foreach (var item in g.Items)
            {
                i++;
                sb.AppendLine(string.Join(",", new[]
                {
                    Csv(i.ToString()),
                    Csv(g.Name),
                    Csv(g.Items.Count.ToString()),
                    Csv(item.Name),
                    Csv(item.Library),
                    Csv(item.Path),
                    Csv(item.SizeBytes?.ToString() ?? string.Empty),
                    Csv(item.Created?.ToString("yyyy-MM-dd") ?? string.Empty),
                    Csv(item.Modified?.ToString("yyyy-MM-dd") ?? string.Empty),
                }));
            }
        }

        await File.WriteAllTextAsync(filePath, sb.ToString(),
            new UTF8Encoding(encoderShouldEmitUTF8Identifier: true), ct);
    }

    private static string Csv(string value)
    {
        if (string.IsNullOrEmpty(value)) return "\"\"";
        return $"\"{value.Replace("\"", "\"\"")}\"";
    }
}