using System.Globalization;
using System.Text.RegularExpressions;
using Core.Parsers.EventOccurrence;

namespace GoogleSheetsScheduleImport;

/// <summary>
/// Parses time labels from the first column of schedule grids.
/// </summary>
public static class TimeCellParser
{
    private static readonly Regex ClockRegex = new(
        @"^(?<h>\d{1,2})(?::(?<m>\d{2}))?\s*(?<ap>a\.?m\.?|p\.?m\.?|AM|PM|am|pm)\s*$",
        RegexOptions.Compiled | RegexOptions.IgnoreCase);

    public static bool TryParse(string? cellText, out TimeOnly time)
    {
        time = default;
        if (string.IsNullOrWhiteSpace(cellText))
            return false;
        var t = cellText.Trim();
        if (t.Equals("NOON", StringComparison.OrdinalIgnoreCase))
        {
            time = new TimeOnly(12, 0);
            return true;
        }

        var m = ClockRegex.Match(t);
        if (m.Success)
        {
            var h = int.Parse(m.Groups["h"].Value, CultureInfo.InvariantCulture);
            var minute = m.Groups["m"].Success ? int.Parse(m.Groups["m"].Value, CultureInfo.InvariantCulture) : 0;
            var apStr = m.Groups["ap"].Value;
            var isPm = apStr.Contains('P', StringComparison.OrdinalIgnoreCase);
            var isAm = apStr.Contains('A', StringComparison.OrdinalIgnoreCase);
            if (isPm && h < 12) h += 12;
            if (isAm && h == 12) h = 0;
            time = new TimeOnly(h, minute);
            return true;
        }

        // Fallback: use core TimeParser if string already looks like parsed format
        try
        {
            time = TimeParser.Parse(t);
            return true;
        }
        catch (FormatException)
        {
            return false;
        }
    }
}