namespace Salmon.Web;

public class TimespanHelper
{
    //https://stackoverflow.com/questions/16689468/how-to-produce-human-readable-strings-to-represent-a-timespan (@rene)
    public static string GetReadableTimespan(TimeSpan ts)
    {
        // formats and its cutoffs based on totalseconds
        var cutoff = new SortedList<long, string> {
            {59, "{3:S}" },
            {60, "{2:M}" },
            {60*60-1, "{2:M}, {3:S}"},
            {60*60, "{1:H}"},
            {24*60*60-1, "{1:H}, {2:M}"},
            {24*60*60, "{0:D}"},
            {Int64.MaxValue , "{0:D}, {1:H}"}
        };

        // find nearest best match
        var find = cutoff.Keys.ToList()
                      .BinarySearch((long)ts.TotalSeconds);
        // negative values indicate a nearest match
        var near = find < 0 ? Math.Abs(find) - 1 : find;
        // use custom formatter to get the string
        return String.Format(
            new HMSFormatter(),
            cutoff[cutoff.Keys[near]],
            ts.Days,
            ts.Hours,
            ts.Minutes,
            ts.Seconds);
    }

    // formatter for forms of
    // seconds/hours/day
    public class HMSFormatter : ICustomFormatter, IFormatProvider
    {
        // list of Formats, with a P customformat for pluralization
        static Dictionary<string, string> timeformats = new Dictionary<string, string> {
        {"S", "{0:P:seconds:second}"},
        {"M", "{0:P:minutes:minute}"},
        {"H","{0:P:hours:hour}"},
        {"D", "{0:P:days:day}"}
    };

        public string Format(string format, object arg, IFormatProvider formatProvider)
        {
            return String.Format(new PluralFormatter(), timeformats[format], arg);
        }

        public object GetFormat(Type formatType)
        {
            return formatType == typeof(ICustomFormatter) ? this : null;
        }
    }

    // formats a numeric value based on a format P:Plural:Singular
    public class PluralFormatter : ICustomFormatter, IFormatProvider
    {

        public string Format(string format, object arg, IFormatProvider formatProvider)
        {
            if (arg != null)
            {
                var parts = format.Split(':'); // ["P", "Plural", "Singular"]

                if (parts[0] == "P") // correct format?
                {
                    // which index postion to use
                    int partIndex = (arg.ToString() == "1") ? 2 : 1;
                    // pick string (safe guard for array bounds) and format
                    return String.Format("{0} {1}", arg, (parts.Length > partIndex ? parts[partIndex] : ""));
                }
            }
            return String.Format(format, arg);
        }

        public object GetFormat(Type formatType)
        {
            return formatType == typeof(ICustomFormatter) ? this : null;
        }
    }
}