using System;

using System.Text.RegularExpressions;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("=== Icelandic Date Parser Test ===\n");

        // Test cases from your examples

        var testCases = new[]

        {

            "Umferðarslys 19.ágúst 2024",

            "Umferðarslys 07.sept.2020", 

            "Frítímaslys 14. nóvember 2024",

            "Sjúklingatryggingaatburður 14.11.2025",

            "Umferðarslys 13.5.2024",

            "Vinnuslys þann 8. desember 2024",

            "Sjúklingatryggingaratvik í kjölfar frítímaslyss 21. mars 2025",

            "Frítímaslys 30.12.2024",

            "Læknamistök 13-15. febrúar 2025",

            "Læknamistök 13 til 15. febrúar 2025",

            "Umferðarslys 25. apríl 2024",

            "Vinnuslys 17.sept.2022",

            "Sjúklingatryggingaratburður janúar 2021 til janúar 2023",

            // Additional test cases for abbreviations

            "Vinnuslys 17.des.2022",

            "Frítímaslys 14.nóv.2024",

            "Umferðarslys 07.sep.2020",

            // Test case with no date

            "Almenn sjúklingatrygging"

        };

        foreach (var testCase in testCases)

        {

            var result = IcelandicDateParser.ExtractDateFromProjectName(testCase);

            Console.WriteLine($"Input: {testCase}");

            Console.WriteLine($"Result: {(result?.ToString("yyyy-MM-dd") ?? "null")}");

            Console.WriteLine();

        }

        // Validation tests

        Console.WriteLine("=== Expected Results Validation ===");

        ValidateTest("Umferðarslys 19.ágúst 2024", new DateTime(2024, 8, 19));

        ValidateTest("Læknamistök 13-15. febrúar 2025", new DateTime(2025, 2, 13));

        ValidateTest("Sjúklingatryggingaratburður janúar 2021 til janúar 2023", new DateTime(2021, 1, 1));

        ValidateTest("Vinnuslys 17.des.2022", new DateTime(2022, 12, 17));

        ValidateTest("Almenn sjúklingatrygging", null);

    }

    private static void ValidateTest(string input, DateTime? expected)

    {

        var result = IcelandicDateParser.ExtractDateFromProjectName(input);

        bool isCorrect = (result == expected);

        string status = isCorrect ? "✓ PASS" : "✗ FAIL";

        Console.WriteLine($"{status} - {input}");

        Console.WriteLine($"  Expected: {expected?.ToString("yyyy-MM-dd") ?? "null"}");

        Console.WriteLine($"  Got:      {result?.ToString("yyyy-MM-dd") ?? "null"}");

        Console.WriteLine();

    }

}

​

public static class IcelandicDateParser

{

    private static readonly Dictionary<string, int> IcelandicMonths = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase)

    {

        { "janúar", 1 },

        { "jan", 1 },

        { "febrúar", 2 },

        { "feb", 2 },

        { "mars", 3 },

        { "mar", 3 },

        { "apríl", 4 },

        { "apr", 4 },

        { "maí", 5 },

        { "júní", 6 },

        { "jún", 6 },

        { "júlí", 7 },

        { "júl", 7 },

        { "ágúst", 8 },

        { "ágú", 8 },

        { "september", 9 },

        { "sept", 9 },

        { "sep", 9 },

        { "október", 10 },

        { "okt", 10 },

        { "nóvember", 11 },

        { "nóv", 11 },

        { "desember", 12 },

        { "des", 12 }

    };

​

    public static DateTime? ExtractDateFromProjectName(string projectName)

    {

        if (string.IsNullOrWhiteSpace(projectName))

            return null;

​

        // Pattern 3: Day-Day. Month Year (e.g., "13-15. febrúar 2025") - use first date

        var pattern3 = @"(\d{1,2})-(\d{1,2})\.\s*(\w+)\s+(\d{4})";

        var match3 = Regex.Match(projectName, pattern3);

        if (match3.Success)

        {

            if (int.TryParse(match3.Groups[1].Value, out int day) &&

                int.TryParse(match3.Groups[4].Value, out int year))

            {

                int month = GetMonthNumber(match3.Groups[3].Value);

                if (month > 0)

                {

                    try

                    {

                        return new DateTime(year, month, day);

                    }

                    catch (ArgumentOutOfRangeException)

                    {

                        return null;

                    }

                }

            }

        }

​

        // Pattern 4: Day til Day. Month Year (e.g., "13 til 15. febrúar 2025") - use first date

        var pattern4 = @"(\d{1,2})\s+til\s+(\d{1,2})\.\s*(\w+)\s+(\d{4})";

        var match4 = Regex.Match(projectName, pattern4);

        if (match4.Success)

        {

            if (int.TryParse(match4.Groups[1].Value, out int day) &&

                int.TryParse(match4.Groups[4].Value, out int year))

            {

                int month = GetMonthNumber(match4.Groups[3].Value);

                if (month > 0)

                {

                    try

                    {

                        return new DateTime(year, month, day);

                    }

                    catch (ArgumentOutOfRangeException)

                    {

                        return null;

                    }

                }

            }

        }

​

        // Pattern 5: Month Year til Month Year (e.g., "janúar 2021 til janúar 2023") - use first date

        var pattern5 = @"(\w+)\s+(\d{4})\s+til\s+\w+\s+\d{4}";

        var match5 = Regex.Match(projectName, pattern5);

        if (match5.Success)

        {

            if (int.TryParse(match5.Groups[2].Value, out int year))

            {

                int month = GetMonthNumber(match5.Groups[1].Value);

                if (month > 0)

                {

                    try

                    {

                        return new DateTime(year, month, 1); // First day of month

                    }

                    catch (ArgumentOutOfRangeException)

                    {

                        return null;

                    }

                }

            }

        }

​

        // Pattern 1: Day.Month.Year (e.g., "19.ágúst 2024", "14.11.2025", "07.sept.2020")

        var pattern1 = @"(\d{1,2})\.(\w+)\.?(\d{4})";

        var match1 = Regex.Match(projectName, pattern1);

        if (match1.Success)

        {

            if (int.TryParse(match1.Groups[1].Value, out int day) &&

                int.TryParse(match1.Groups[3].Value, out int year))

            {

                string monthStr = match1.Groups[2].Value.TrimEnd('.');

                int month = GetMonthNumber(monthStr);

                if (month > 0)

                {

                    try

                    {

                        return new DateTime(year, month, day);

                    }

                    catch (ArgumentOutOfRangeException)

                    {

                        return null;

                    }

                }

            }

        }

​

        // Pattern 2: Day. Month Year (e.g., "14. nóvember 2024", "8. desember 2024")

        var pattern2 = @"(\d{1,2})\.\s*(\w+)\s+(\d{4})";

        var match2 = Regex.Match(projectName, pattern2);

        if (match2.Success)

        {

            if (int.TryParse(match2.Groups[1].Value, out int day) &&

                int.TryParse(match2.Groups[3].Value, out int year))

            {

                int month = GetMonthNumber(match2.Groups[2].Value);

                if (month > 0)

                {

                    try

                    {

                        return new DateTime(year, month, day);

                    }

                    catch (ArgumentOutOfRangeException)

                    {

                        return null;

                    }

                }

            }

        }

​

        // Pattern 6: Month Year (e.g., "desember 2021") - use first day of month

        var pattern6 = @"(\w+)\s+(\d{4})";

        var match6 = Regex.Match(projectName, pattern6);

        if (match6.Success)

        {

            if (int.TryParse(match6.Groups[2].Value, out int year))

            {

                int month = GetMonthNumber(match6.Groups[1].Value);

                if (month > 0)

                {

                    try

                    {

                        return new DateTime(year, month, 1); // First day of month

                    }

                    catch (ArgumentOutOfRangeException)

                    {

                        return null;

                    }

                }

            }

        }

​

        return null;

    }

​

    private static int GetMonthNumber(string monthString)

    {

        // Try to parse as number first

        if (int.TryParse(monthString, out int monthNum) && monthNum >= 1 && monthNum <= 12)

        {

            return monthNum;

        }

​

        // Try to match Icelandic month name

        if (IcelandicMonths.TryGetValue(monthString, out int month))

        {

            return month;

        }

​

        return 0; // Invalid month

    }

}