namespace GoogleSheetsScheduleImport;

/// <summary>
/// Collapses duplicate site-wide rows (same event name, date, time) that appear in every location column
/// (e.g. CURFEW shaded across all rooms) into a single line with no location — still under
/// <c>General Schedule</c>, which the parser maps to <see cref="Core.Entities.EventDefinition.GeneralSchedule"/>.
/// </summary>
public static class GlobalEventDeduplicator
{
    private static readonly HashSet<string> BuiltinSiteWideNames = new(StringComparer.OrdinalIgnoreCase)
    {
        "CURFEW"
    };

    /// <summary>
    /// First occurrence in row/column order is kept; location is cleared so the import line is not room-specific.
    /// </summary>
    public static List<ParsedOccurrenceLine> Deduplicate(
        IReadOnlyList<ParsedOccurrenceLine> lines,
        IReadOnlyCollection<string>? extraSiteWideNames = null)
    {
        var siteWide = new HashSet<string>(BuiltinSiteWideNames, StringComparer.OrdinalIgnoreCase);
        if (extraSiteWideNames != null)
        {
            foreach (var n in extraSiteWideNames)
            {
                if (!string.IsNullOrWhiteSpace(n))
                    siteWide.Add(n.Trim());
            }
        }

        var seen = new HashSet<(string Name, string Month, int Day, string Time)>();
        var ordered = lines.OrderBy(l => l.SourceRowStart).ThenBy(l => l.SourceCol).ToList();
        var result = new List<ParsedOccurrenceLine>(ordered.Count);

        foreach (var line in ordered)
        {
            var name = TextNormalization.ForEmitLine(line.Name);
            if (string.IsNullOrEmpty(name) || !siteWide.Contains(name))
            {
                result.Add(line);
                continue;
            }

            var key = (name, line.Month, line.Day, line.TimeRange);
            if (!seen.Add(key))
                continue;

            result.Add(line with { Location = string.Empty, Name = name });
        }

        return result;
    }
}