MrzValidator.cs

using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
 
namespace NeuroAccess.Nfc.TravelDocuments
{
    public enum MrzLayout
    {
        Td1 = 0,
 
        Td2 = 1,
 
        Td3 = 2
    }
 
    public sealed class MrzValidationResult
    {
        internal MrzValidationResult(
            bool IsParsed,
            MrzLayout? Layout,
            string NormalizedMrz,
            DocumentInformation? DocumentInformation,
            bool DocumentNumberCheckPassed,
            bool DateOfBirthCheckPassed,
            bool ExpiryCheckPassed,
            bool CompositeCheckPassed,
            int RequiredCheckCount,
            int PassedRequiredCheckCount,
            string? FailureReason)
        {
            this.IsParsed = IsParsed;
            this.Layout = Layout;
            this.NormalizedMrz = NormalizedMrz;
            this.DocumentInformation = DocumentInformation;
            this.DocumentNumberCheckPassed = DocumentNumberCheckPassed;
            this.DateOfBirthCheckPassed = DateOfBirthCheckPassed;
            this.ExpiryCheckPassed = ExpiryCheckPassed;
            this.CompositeCheckPassed = CompositeCheckPassed;
            this.RequiredCheckCount = RequiredCheckCount;
            this.PassedRequiredCheckCount = PassedRequiredCheckCount;
            this.FailureReason = FailureReason;
        }
 
        public bool IsParsed { get; }
 
        public MrzLayout? Layout { get; }
 
        public string NormalizedMrz { get; }
 
        public DocumentInformation? DocumentInformation { get; }
 
        public bool DocumentNumberCheckPassed { get; }
 
        public bool DateOfBirthCheckPassed { get; }
 
        public bool ExpiryCheckPassed { get; }
 
        public bool CompositeCheckPassed { get; }
 
        public int RequiredCheckCount { get; }
 
        public int PassedRequiredCheckCount { get; }
 
        public string? FailureReason { get; }
    }
 
    public static class MrzValidator
    {
        private static readonly IReadOnlyDictionary<char, char> CheckDigitConfusions = new Dictionary<char, char>
        {
            { 'O', '0' },
            { 'Q', '0' },
            { 'I', '1' },
            { 'L', '1' },
            { 'Z', '2' },
            { 'S', '5' },
            { 'B', '8' },
            { 'G', '6' },
            { '<', '0' }
        };
 
        private static readonly Regex Td2MrzNumber9CharsPlus = new(@"^(?'DocType'.{1,2})<(?'Issuer'[A-Z<]{3})(?'PID'[^<]+(<[^<]+)*)<<(?'SID'[^<]+(<[^<]+)*)<*\n(?'Nr1'.{9})<(?'Nationality'[A-Z<]{3})(?'Birth'.{6})(?'BirthCheck'\d)(?'Gender'[MF<])(?'Expires'.{6})(?'ExpiryCheck'\d)(?'Tail'.{7})(?'OverallCheck'\d)$", RegexOptions.Multiline);
        private static readonly Regex Td2MrzNumber9Chars = new(@"^(?'DocType'.{1,2})<(?'Issuer'[A-Z<]{3})(?'PID'[^<]+(<[^<]+)*)<<(?'SID'[^<]+(<[^<]+)*)<*\n(?'Nr'.{9})(?'NrCheck'\d)(?'Nationality'[A-Z<]{3})(?'Birth'.{6})(?'BirthCheck'\d)(?'Gender'[MF<])(?'Expires'.{6})(?'ExpiryCheck'\d)(?'Optional'.{7})(?'OverallCheck'\d)$", RegexOptions.Multiline);
        private static readonly Regex Td1MrzNumber9CharsPlus = new(@"^(?'DocType'.{1,2})<(?'Issuer'[A-Z<]{3})(?'Nr1'.{9})<(?'Nr2'.{3})(?'NrCheck'\d)(?'Optional1'.{11})\n(?'Birth'.{6})(?'BirthCheck'\d)(?'Gender'[MF<])(?'Expires'.{6})(?'ExpiryCheck'\d)(?'Nationality'[A-Z<]{3})(?'Optional2'.{11})(?'OverallCheck'\d)\n(?'PID'[^<]+(<[^<]+)*)<<(?'SID'[^<]+(<[^<]+)*).*$", RegexOptions.Multiline);
        private static readonly Regex Td1MrzNumber9Chars = new(@"^(?'DocType'.{1,2})<(?'Issuer'[A-Z<]{3})(?'Nr'.{9})(?'NrCheck'.)(?'Optional1'.{15})\n(?'Birth'[^<]{6})(?'BirthCheck'\d)(?'Gender'[MF<])(?'Expires'[^<]{6})(?'ExpiryCheck'\d)(?'Nationality'[A-Z<]{3})(?'Optional2'.{11})(?'OverallCheck'\d)\n(?'PID'[^<]+(<[^<]+)*)<<(?'SID'[^<]+(<[^<]+)*).*$", RegexOptions.Multiline);
        private static readonly Regex Td3MrzNumber9Chars = new(@"^(?'DocType'.{1,2})<(?'Issuer'[A-Z<]{3})(?'PID'[^<]+(<[^<]+)*)<<(?'SID'[^<]+(<[^<]+)*)<*\n(?'Nr'.{9})(?'NrCheck'\d)(?'Nationality'[A-Z<]{3})(?'Birth'[^<]{6})(?'BirthCheck'\d)(?'Gender'[MF<])(?'Expires'[^<]{6})(?'ExpiryCheck'\d)(?'Optional'.{14})(?'OptionalCheck'\d)(?'OverallCheck'\d)$", RegexOptions.Multiline);
 
        private static readonly ParserDefinition[] OrderedPatterns =
        [
            new ParserDefinition(MrzLayout.Td2, Td2MrzNumber9CharsPlus, AssembleTd2Info2),
            new ParserDefinition(MrzLayout.Td2, Td2MrzNumber9Chars, AssembleTd2Info1),
            new ParserDefinition(MrzLayout.Td3, Td3MrzNumber9Chars, AssembleTd3Info1),
            new ParserDefinition(MrzLayout.Td1, Td1MrzNumber9CharsPlus, AssembleTd1Info2),
            new ParserDefinition(MrzLayout.Td1, Td1MrzNumber9Chars, AssembleTd1Info1)
        ];
 
        public static bool TryParse(string Mrz, [NotNullWhen(true)] out DocumentInformation? Info)
        {
            MrzValidationResult Validation = Validate(Mrz);
            Info = Validation.DocumentInformation;
            return Validation.IsParsed;
        }
 
        public static MrzValidationResult Validate(string Mrz)
        {
            ArgumentNullException.ThrowIfNull(Mrz);
 
            string NormalizedMrz = NormalizeMrz(Mrz);
            string[] Lines = SplitLines(NormalizedMrz);
            MrzLayout? Layout = TryDetectLayout(Lines);
            int RequiredCheckCount = Layout.HasValue ? GetRequiredCheckCount(Layout.Value) : 0;
            int PassedRequiredCheckCount = 0;
            bool DocumentNumberCheckPassed = false;
            bool DateOfBirthCheckPassed = false;
            bool ExpiryCheckPassed = false;
            bool CompositeCheckPassed = false;
 
            if (Layout.HasValue)
            {
                PassedRequiredCheckCount = CountPassedRequiredChecks(
                    Layout.Value,
                    Lines,
                    out DocumentNumberCheckPassed,
                    out DateOfBirthCheckPassed,
                    out ExpiryCheckPassed,
                    out CompositeCheckPassed);
            }
 
            DocumentInformation? ParsedInformation;
            MrzLayout? ParsedLayout;
            if (Layout.HasValue)
            {
                if (TryParseStandard(Layout.Value, Lines, out ParsedInformation)
                    && IsSemanticallyValid(Layout.Value, ParsedInformation))
                {
                    return new MrzValidationResult(
                        true,
                        Layout,
                        NormalizedMrz,
                        ParsedInformation,
                        DocumentNumberCheckPassed,
                        DateOfBirthCheckPassed,
                        ExpiryCheckPassed,
                        CompositeCheckPassed,
                        RequiredCheckCount,
                        PassedRequiredCheckCount,
                        null);
                }
 
                if (TryParseFallback(NormalizedMrz, Layout, out ParsedInformation, out ParsedLayout)
                    && ParsedLayout.HasValue
                    && IsSemanticallyValid(ParsedLayout.Value, ParsedInformation))
                {
                    return new MrzValidationResult(
                        true,
                        ParsedLayout,
                        NormalizedMrz,
                        ParsedInformation,
                        DocumentNumberCheckPassed,
                        DateOfBirthCheckPassed,
                        ExpiryCheckPassed,
                        CompositeCheckPassed,
                        RequiredCheckCount,
                        PassedRequiredCheckCount,
                        null);
                }
 
                return new MrzValidationResult(
                    false,
                    Layout,
                    NormalizedMrz,
                    null,
                    DocumentNumberCheckPassed,
                    DateOfBirthCheckPassed,
                    ExpiryCheckPassed,
                    CompositeCheckPassed,
                    RequiredCheckCount,
                    PassedRequiredCheckCount,
                    "StrictLayoutValidationFailed");
            }
 
            if (TryParseFallback(NormalizedMrz, null, out ParsedInformation, out ParsedLayout)
                && ParsedLayout.HasValue
                && IsSemanticallyValid(ParsedLayout.Value, ParsedInformation))
            {
                return new MrzValidationResult(
                    true,
                    ParsedLayout,
                    NormalizedMrz,
                    ParsedInformation,
                    DocumentNumberCheckPassed,
                    DateOfBirthCheckPassed,
                    ExpiryCheckPassed,
                    CompositeCheckPassed,
                    RequiredCheckCount,
                    PassedRequiredCheckCount,
                    null);
            }
 
            return new MrzValidationResult(
                false,
                Layout,
                NormalizedMrz,
                null,
                DocumentNumberCheckPassed,
                DateOfBirthCheckPassed,
                ExpiryCheckPassed,
                CompositeCheckPassed,
                RequiredCheckCount,
                PassedRequiredCheckCount,
                Layout.HasValue ? "ValidationFailed" : "LayoutNotRecognized");
        }
 
        public static char CalculateCheckDigit(string Value)
        {
            string CheckDigit = CalculateCheckDigitText(Value);
            return CheckDigit.Length == 1 ? CheckDigit[0] : '\0';
        }
 
        private static bool TryParseFallback(
            string NormalizedMrz,
            MrzLayout? ExpectedLayout,
            [NotNullWhen(true)] out DocumentInformation? Info,
            out MrzLayout? Layout)
        {
            foreach (ParserDefinition Definition in OrderedPatterns)
            {
                if (ExpectedLayout.HasValue && Definition.Layout != ExpectedLayout.Value)
                    continue;
 
                Match Match = Definition.Pattern.Match(NormalizedMrz);
                if (!Match.Success)
                    continue;
 
                DocumentInformation? Candidate = Definition.Factory(Match);
                if (Candidate is null)
                    continue;
 
                Layout = Definition.Layout;
                Info = Candidate;
                return true;
            }
 
            Info = null;
            Layout = null;
            return false;
        }
 
        private static bool IsSemanticallyValid(MrzLayout Layout, DocumentInformation Info)
        {
            return Layout switch
            {
                MrzLayout.Td1 => IsSemanticallyValidTd1(Info),
                MrzLayout.Td2 => IsSemanticallyValidTd2(Info),
                MrzLayout.Td3 => IsSemanticallyValidTd3(Info),
                _ => false
            };
        }
 
        private static bool IsSemanticallyValidTd1(DocumentInformation Info)
        {
            return HasValidDocumentType(Info.DocumentType)
                && HasValidCountryCode(Info.IssuingState)
                && HasValidDocumentNumber(Info.DocumentNumber)
                && HasValidMrzDate(Info.DateOfBirth)
                && HasValidGender(Info.Gender)
                && HasValidMrzDate(Info.ExpiryDate)
                && HasValidCountryCode(Info.Nationality)
                && HasValidIdentifiers(Info.PrimaryIdentifier, Info.SecondaryIdentifier)
                && HasValidMrzInformation(Info.MRZ_Information);
        }
 
        private static bool IsSemanticallyValidTd2(DocumentInformation Info)
        {
            return HasValidDocumentType(Info.DocumentType)
                && HasValidCountryCode(Info.IssuingState)
                && HasValidDocumentNumber(Info.DocumentNumber)
                && HasValidCountryCode(Info.Nationality)
                && HasValidMrzDate(Info.DateOfBirth)
                && HasValidGender(Info.Gender)
                && HasValidMrzDate(Info.ExpiryDate)
                && HasValidIdentifiers(Info.PrimaryIdentifier, Info.SecondaryIdentifier)
                && HasValidMrzInformation(Info.MRZ_Information);
        }
 
        private static bool IsSemanticallyValidTd3(DocumentInformation Info)
        {
            return HasValidDocumentType(Info.DocumentType)
                && HasValidCountryCode(Info.IssuingState)
                && HasValidDocumentNumber(Info.DocumentNumber)
                && HasValidCountryCode(Info.Nationality)
                && HasValidMrzDate(Info.DateOfBirth)
                && HasValidGender(Info.Gender)
                && HasValidMrzDate(Info.ExpiryDate)
                && HasValidIdentifiers(Info.PrimaryIdentifier, Info.SecondaryIdentifier)
                && HasValidMrzInformation(Info.MRZ_Information);
        }
 
        private static bool HasValidDocumentType(string? Value)
        {
            return !string.IsNullOrWhiteSpace(Value)
                && Value.Length <= 2
                && Value.All(static Character => Character is >= 'A' and <= 'Z');
        }
 
        private static bool HasValidCountryCode(string? Value)
        {
            return !string.IsNullOrWhiteSpace(Value)
                && Value.Length == 3
                && Value.All(static Character => Character is >= 'A' and <= 'Z');
        }
 
        private static bool HasValidDocumentNumber(string? Value)
        {
            return !string.IsNullOrWhiteSpace(Value)
                && Value.All(static Character => (Character is >= 'A' and <= 'Z') || (Character is >= '0' and <= '9'));
        }
 
        private static bool HasValidGender(string? Value)
        {
            return Value is "M" or "F" or "<";
        }
 
        private static bool HasValidMrzDate(string? Value)
        {
            if (string.IsNullOrWhiteSpace(Value) || Value.Length != 6 || !Value.All(static Character => Character is >= '0' and <= '9'))
                return false;
 
            if (Value == "000000")
                return false;
 
            int Month = int.Parse(Value.Substring(2, 2), System.Globalization.CultureInfo.InvariantCulture);
            int Day = int.Parse(Value.Substring(4, 2), System.Globalization.CultureInfo.InvariantCulture);
            if (Month < 1 || Month > 12)
                return false;
            if (Day < 1)
                return false;
 
            int MaxDay = Month switch
            {
                4 or 6 or 9 or 11 => 30,
                2 => 29,
                _ => 31
            };
 
            return Day <= MaxDay;
        }
 
        private static bool HasValidIdentifiers(string[]? PrimaryIdentifier, string[]? SecondaryIdentifier)
        {
            return HasValidIdentifierParts(PrimaryIdentifier, true)
                && HasValidIdentifierParts(SecondaryIdentifier, false);
        }
 
        private static bool HasValidIdentifierParts(string[]? Parts, bool Required)
        {
            if (Parts is null || Parts.Length == 0)
                return !Required;
 
            bool HasContent = false;
            foreach (string Part in Parts)
            {
                if (string.IsNullOrWhiteSpace(Part))
                    continue;
 
                if (!Part.All(static Character => Character is >= 'A' and <= 'Z'))
                    return false;
 
                HasContent = true;
            }
 
            return Required ? HasContent : true;
        }
 
        private static bool HasValidMrzInformation(string? Value)
        {
            return !string.IsNullOrWhiteSpace(Value)
                && Value.All(static Character => (Character is >= 'A' and <= 'Z') || (Character is >= '0' and <= '9') || Character == '<');
        }
 
        private static bool TryParseStandard(
            MrzLayout Layout,
            string[] Lines,
            [NotNullWhen(true)] out DocumentInformation? Info)
        {
            switch (Layout)
            {
                case MrzLayout.Td1:
                    return TryParseTd1Standard(Lines, out Info);
 
                case MrzLayout.Td2:
                    return TryParseTd2Standard(Lines, out Info);
 
                case MrzLayout.Td3:
                    return TryParseTd3Standard(Lines, out Info);
 
                default:
                    Info = null;
                    return false;
            }
        }
 
        private static bool TryParseTd1Standard(string[] Lines, [NotNullWhen(true)] out DocumentInformation? Info)
        {
            if (Lines.Length != 3 || Lines[0].Length != 30 || Lines[1].Length != 30 || Lines[2].Length != 30)
            {
                Info = null;
                return false;
            }
 
            string Line1 = Lines[0];
            string Line2 = Lines[1];
            string Line3 = Lines[2];
            if (Line1[14] == '<')
            {
                Info = null;
                return false;
            }
 
            string DocumentNumber = Line1.Substring(5, 9);
            if (!IsCheckDigitValid(DocumentNumber, Line1[14]))
            {
                Info = null;
                return false;
            }
 
            string DateOfBirth = Line2.Substring(0, 6);
            if (!IsCheckDigitValid(DateOfBirth, Line2[6]))
            {
                Info = null;
                return false;
            }
 
            string ExpiryDate = Line2.Substring(8, 6);
            if (!IsCheckDigitValid(ExpiryDate, Line2[14]))
            {
                Info = null;
                return false;
            }
 
            string Composite = Line1.Substring(5, 10) + Line1.Substring(15, 15) + Line2.Substring(0, 7) + Line2.Substring(8, 7) + Line2.Substring(18, 11);
            if (!IsCheckDigitValid(Composite, Line2[29]))
            {
                Info = null;
                return false;
            }
 
            Info = new DocumentInformation
            {
                DocumentType = ExtractDocumentType(Line1.Substring(0, 2)),
                IssuingState = Line1.Substring(2, 3),
                DocumentNumber = DocumentNumber.Replace("<", string.Empty),
                DateOfBirth = DateOfBirth,
                Gender = Line2.Substring(7, 1),
                ExpiryDate = ExpiryDate,
                Nationality = Line2.Substring(15, 3),
                OptionalData = (Line1.Substring(15, 15) + Line2.Substring(18, 11)).Replace("<", string.Empty),
                MRZ_Information = DocumentNumber + Line1[14] + DateOfBirth + Line2[6] + ExpiryDate + Line2[14]
            };
            PopulateNames(Info, Line3);
            return true;
        }
 
        private static bool TryParseTd2Standard(string[] Lines, [NotNullWhen(true)] out DocumentInformation? Info)
        {
            if (Lines.Length != 2 || Lines[0].Length != 36 || Lines[1].Length != 36)
            {
                Info = null;
                return false;
            }
 
            string Line1 = Lines[0];
            string Line2 = Lines[1];
            string DocumentNumber = Line2.Substring(0, 9);
            string DateOfBirth = Line2.Substring(13, 6);
            string ExpiryDate = Line2.Substring(21, 6);
            if (!IsCheckDigitValid(DocumentNumber, Line2[9])
                || !IsCheckDigitValid(DateOfBirth, Line2[19])
                || !IsCheckDigitValid(ExpiryDate, Line2[27]))
            {
                Info = null;
                return false;
            }
 
            string Composite = Line2.Substring(0, 10) + Line2.Substring(13, 7) + Line2.Substring(21, 7) + Line2.Substring(28, 7);
            if (!IsCheckDigitValid(Composite, Line2[35]))
            {
                Info = null;
                return false;
            }
 
            Info = new DocumentInformation
            {
                DocumentType = ExtractDocumentType(Line1.Substring(0, 2)),
                IssuingState = Line1.Substring(2, 3),
                DocumentNumber = DocumentNumber.Replace("<", string.Empty),
                Nationality = Line2.Substring(10, 3),
                DateOfBirth = DateOfBirth,
                Gender = Line2.Substring(20, 1),
                ExpiryDate = ExpiryDate,
                OptionalData = Line2.Substring(28, 7).Replace("<", string.Empty),
                MRZ_Information = DocumentNumber + Line2[9] + DateOfBirth + Line2[19] + ExpiryDate + Line2[27]
            };
            PopulateNames(Info, Line1.Substring(5));
            return true;
        }
 
        private static bool TryParseTd3Standard(string[] Lines, [NotNullWhen(true)] out DocumentInformation? Info)
        {
            if (Lines.Length != 2 || Lines[0].Length != 44 || Lines[1].Length != 44)
            {
                Info = null;
                return false;
            }
 
            string Line1 = Lines[0];
            string Line2 = Lines[1];
            string DocumentNumber = Line2.Substring(0, 9);
            string DateOfBirth = Line2.Substring(13, 6);
            string ExpiryDate = Line2.Substring(21, 6);
            string OptionalData = Line2.Substring(28, 14);
            if (!IsCheckDigitValid(DocumentNumber, Line2[9])
                || !IsCheckDigitValid(DateOfBirth, Line2[19])
                || !IsCheckDigitValid(ExpiryDate, Line2[27])
                || !IsCheckDigitValid(OptionalData, Line2[42]))
            {
                Info = null;
                return false;
            }
 
            string Composite = Line2.Substring(0, 10) + Line2.Substring(13, 7) + Line2.Substring(21, 7) + Line2.Substring(28, 15);
            if (!IsCheckDigitValid(Composite, Line2[43]))
            {
                Info = null;
                return false;
            }
 
            Info = new DocumentInformation
            {
                DocumentType = ExtractDocumentType(Line1.Substring(0, 2)),
                IssuingState = Line1.Substring(2, 3),
                DocumentNumber = DocumentNumber.Replace("<", string.Empty),
                Nationality = Line2.Substring(10, 3),
                DateOfBirth = DateOfBirth,
                Gender = Line2.Substring(20, 1),
                ExpiryDate = ExpiryDate,
                OptionalData = OptionalData.Replace("<", string.Empty),
                MRZ_Information = DocumentNumber + Line2[9] + DateOfBirth + Line2[19] + ExpiryDate + Line2[27]
            };
            PopulateNames(Info, Line1.Substring(5));
            return true;
        }
 
        private static int CountPassedRequiredChecks(
            MrzLayout Layout,
            string[] Lines,
            out bool DocumentNumberCheckPassed,
            out bool DateOfBirthCheckPassed,
            out bool ExpiryCheckPassed,
            out bool CompositeCheckPassed)
        {
            switch (Layout)
            {
                case MrzLayout.Td1:
                    DocumentNumberCheckPassed = Lines.Length >= 1 && Lines[0].Length >= 15 && IsCheckDigitValid(Lines[0].Substring(5, 9), Lines[0][14]);
                    DateOfBirthCheckPassed = Lines.Length >= 2 && Lines[1].Length >= 7 && IsCheckDigitValid(Lines[1].Substring(0, 6), Lines[1][6]);
                    ExpiryCheckPassed = Lines.Length >= 2 && Lines[1].Length >= 15 && IsCheckDigitValid(Lines[1].Substring(8, 6), Lines[1][14]);
                    CompositeCheckPassed = Lines.Length >= 2 && Lines[0].Length == 30 && Lines[1].Length == 30
                        && IsCheckDigitValid(Lines[0].Substring(5, 10) + Lines[0].Substring(15, 15) + Lines[1].Substring(0, 7) + Lines[1].Substring(8, 7) + Lines[1].Substring(18, 11), Lines[1][29]);
                    break;
 
                case MrzLayout.Td2:
                    DocumentNumberCheckPassed = Lines.Length >= 2 && Lines[1].Length >= 10 && IsCheckDigitValid(Lines[1].Substring(0, 9), Lines[1][9]);
                    DateOfBirthCheckPassed = Lines.Length >= 2 && Lines[1].Length >= 20 && IsCheckDigitValid(Lines[1].Substring(13, 6), Lines[1][19]);
                    ExpiryCheckPassed = Lines.Length >= 2 && Lines[1].Length >= 28 && IsCheckDigitValid(Lines[1].Substring(21, 6), Lines[1][27]);
                    CompositeCheckPassed = Lines.Length >= 2 && Lines[1].Length == 36
                        && IsCheckDigitValid(Lines[1].Substring(0, 10) + Lines[1].Substring(13, 7) + Lines[1].Substring(21, 7) + Lines[1].Substring(28, 7), Lines[1][35]);
                    break;
 
                default:
                    DocumentNumberCheckPassed = Lines.Length >= 2 && Lines[1].Length >= 10 && IsCheckDigitValid(Lines[1].Substring(0, 9), Lines[1][9]);
                    DateOfBirthCheckPassed = Lines.Length >= 2 && Lines[1].Length >= 20 && IsCheckDigitValid(Lines[1].Substring(13, 6), Lines[1][19]);
                    ExpiryCheckPassed = Lines.Length >= 2 && Lines[1].Length >= 28 && IsCheckDigitValid(Lines[1].Substring(21, 6), Lines[1][27]);
                    CompositeCheckPassed = Lines.Length >= 2 && Lines[1].Length == 44
                        && IsCheckDigitValid(Lines[1].Substring(0, 10) + Lines[1].Substring(13, 7) + Lines[1].Substring(21, 7) + Lines[1].Substring(28, 15), Lines[1][43]);
                    break;
            }
 
            int Count = 0;
            if (DocumentNumberCheckPassed)
                Count++;
            if (DateOfBirthCheckPassed)
                Count++;
            if (ExpiryCheckPassed)
                Count++;
            if (CompositeCheckPassed)
                Count++;
            return Count;
        }
 
        private static int GetRequiredCheckCount(MrzLayout Layout)
        {
            return Layout switch
            {
                MrzLayout.Td1 => 4,
                MrzLayout.Td2 => 4,
                MrzLayout.Td3 => 4,
                _ => 0
            };
        }
 
        private static MrzLayout? TryDetectLayout(string[] Lines)
        {
            if (Lines.Length == 3 && Lines.All(static Line => Line.Length == 30))
                return MrzLayout.Td1;
            if (Lines.Length == 2 && Lines.All(static Line => Line.Length == 36))
                return MrzLayout.Td2;
            if (Lines.Length == 2 && Lines.All(static Line => Line.Length == 44))
                return MrzLayout.Td3;
            return null;
        }
 
        private static string NormalizeMrz(string Mrz)
        {
            StringBuilder Builder = new StringBuilder(Mrz.Length);
            foreach (char Character in Mrz.ToUpperInvariant())
            {
                if (Character == '\r')
                    continue;
                if (Character == '\n')
                {
                    Builder.Append('\n');
                    continue;
                }
 
                Builder.Append(NormalizeMrzCharacter(Character));
            }
 
            string[] RawLines = Builder.ToString()
                .Split('\n', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
            if (RawLines.Length == 1)
            {
                string Flat = RawLines[0];
                switch (Flat.Length)
                {
                    case 90:
                        return string.Join("\n", [Flat.Substring(0, 30), Flat.Substring(30, 30), Flat.Substring(60, 30)]);
 
                    case 72:
                        return string.Join("\n", [Flat.Substring(0, 36), Flat.Substring(36, 36)]);
 
                    case 88:
                        return string.Join("\n", [Flat.Substring(0, 44), Flat.Substring(44, 44)]);
                }
            }
 
            return string.Join("\n", RawLines);
        }
 
        private static string[] SplitLines(string NormalizedMrz)
        {
            if (string.IsNullOrWhiteSpace(NormalizedMrz))
                return [];
 
            return NormalizedMrz.Split('\n', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
        }
 
        private static char NormalizeMrzCharacter(char Character)
        {
            if (char.IsWhiteSpace(Character))
                return '<';
            if (Character == '<' || Character == '«' || Character == '‹' || Character == '›')
                return '<';
            if ((Character >= 'A' && Character <= 'Z') || (Character >= '0' && Character <= '9'))
                return Character;
            return Character;
        }
 
        private static bool IsCheckDigitValid(string Field, char ExpectedCheckDigit)
        {
            return NormalizeCheckDigitChar(ExpectedCheckDigit) == CalculateCheckDigit(Field);
        }
 
        private static char NormalizeCheckDigitChar(char Character)
        {
            char Normalized = NormalizeMrzCharacter(char.ToUpperInvariant(Character));
            if (Normalized >= '0' && Normalized <= '9')
                return Normalized;
            return CheckDigitConfusions.TryGetValue(Normalized, out char Replacement) ? Replacement : '\0';
        }
 
        private static string CalculateCheckDigitText(string Value)
        {
            int Sum = 0;
            int Index = 0;
            foreach (char Character in Value)
            {
                int CharacterValue = GetMrzCharacterValue(Character);
                if (CharacterValue < 0)
                    return string.Empty;
 
                Sum += CharacterValue * Weights[Index++ % 3];
            }
 
            return new string((char)('0' + (Sum % 10)), 1);
        }
 
        private static int GetMrzCharacterValue(char Character)
        {
            if (Character >= '0' && Character <= '9')
                return Character - '0';
            if (Character >= 'A' && Character <= 'Z')
                return (Character - 'A') + 10;
            if (Character == '<')
                return 0;
            return -1;
        }
 
        private static string ExtractDocumentType(string Value)
        {
            return Value.Replace("<", string.Empty);
        }
 
        private static void PopulateNames(DocumentInformation Info, string Value)
        {
            string[] Parts = Value.TrimEnd('<').Split("<<", 2, StringSplitOptions.None);
            Info.PrimaryIdentifier = SplitIdentifierPart(Parts[0]);
            Info.SecondaryIdentifier = Parts.Length > 1 ? SplitIdentifierPart(Parts[1]) : [];
        }
 
        private static string[] SplitIdentifierPart(string Value)
        {
            return Value.Split('<', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
        }
 
        private static DocumentInformation? AssembleTd2Info2(Match Match)
        {
            if (!TryParseTd2OverflowTail(
                Match.Groups["Nr1"].Value,
                Match.Groups["Tail"].Value,
                Match.Groups["Birth"].Value,
                Match.Groups["BirthCheck"].Value,
                Match.Groups["Expires"].Value,
                Match.Groups["ExpiryCheck"].Value,
                Match.Groups["OverallCheck"].Value,
                out string? DocumentNumberSuffix,
                out string? NumberCheck,
                out string? OptionalData))
                return null;
 
            DocumentInformation Result = AssembleInfo(Match);
            Result.DocumentNumber = Match.Groups["Nr1"].Value + DocumentNumberSuffix;
            Result.OptionalData = OptionalData;
            return CalcTd2OverflowMrzInfo(Result, Match, NumberCheck, OptionalData) ? Result : null;
        }
 
        private static DocumentInformation? AssembleTd1Info2(Match Match)
        {
            DocumentInformation Result = AssembleInfo(Match);
            Result.DocumentNumber = Match.Groups["Nr1"].Value + Match.Groups["Nr2"].Value;
            return CalcTd1MrzInfo(Result, Match) ? Result : null;
        }
 
        private static DocumentInformation? AssembleTd1Info1(Match Match)
        {
            DocumentInformation Result = AssembleInfo(Match);
            Result.DocumentNumber = Match.Groups["Nr"].Value;
            return CalcTd1MrzInfo(Result, Match) ? Result : null;
        }
 
        private static DocumentInformation? AssembleTd2Info1(Match Match)
        {
            DocumentInformation Result = AssembleInfo(Match);
            Result.DocumentNumber = Match.Groups["Nr"].Value;
            return CalcMrzInfo(Result, Match, MrzLayout.Td2) ? Result : null;
        }
 
        private static DocumentInformation? AssembleTd3Info1(Match Match)
        {
            DocumentInformation Result = AssembleInfo(Match);
            Result.DocumentNumber = Match.Groups["Nr"].Value;
            return CalcMrzInfo(Result, Match, MrzLayout.Td3) ? Result : null;
        }
 
        private static bool CalcTd1MrzInfo(DocumentInformation Info, Match Match)
        {
            if (Info.DocumentNumber is null || Info.DateOfBirth is null || Info.ExpiryDate is null)
                return false;
 
            string NumberCheck = Match.Groups["NrCheck"].Value;
            if (NumberCheck != CalculateCheckDigitText(Info.DocumentNumber))
                return false;
 
            string BirthCheck = Match.Groups["BirthCheck"].Value;
            if (BirthCheck != CalculateCheckDigitText(Info.DateOfBirth))
                return false;
 
            string ExpiryCheck = Match.Groups["ExpiryCheck"].Value;
            if (ExpiryCheck != CalculateCheckDigitText(Info.ExpiryDate))
                return false;
 
            string OptionalLine1 = Match.Groups["Optional1"].Value;
            string OptionalLine2 = Match.Groups["Optional2"].Value;
            string OverallCheck = Match.Groups["OverallCheck"].Value;
            string Composite = Info.DocumentNumber + NumberCheck + OptionalLine1 + Info.DateOfBirth + BirthCheck + Info.ExpiryDate + ExpiryCheck + OptionalLine2;
            if (OverallCheck != CalculateCheckDigitText(Composite))
                return false;
 
            Info.OptionalData = (OptionalLine1 + OptionalLine2).Replace("<", string.Empty);
            Info.MRZ_Information = Info.DocumentNumber + NumberCheck + Info.DateOfBirth + BirthCheck + Info.ExpiryDate + ExpiryCheck;
            Info.DocumentNumber = Info.DocumentNumber.Replace("<", string.Empty);
            return true;
        }
 
        private static bool CalcTd2OverflowMrzInfo(DocumentInformation Info, Match Match, string NumberCheck, string OptionalData)
        {
            if (Info.DocumentNumber is null || Info.DateOfBirth is null || Info.ExpiryDate is null)
                return false;
 
            if (NumberCheck != CalculateCheckDigitText(Info.DocumentNumber))
                return false;
 
            string BirthCheck = Match.Groups["BirthCheck"].Value;
            if (BirthCheck != CalculateCheckDigitText(Info.DateOfBirth))
                return false;
 
            string ExpiryCheck = Match.Groups["ExpiryCheck"].Value;
            if (ExpiryCheck != CalculateCheckDigitText(Info.ExpiryDate))
                return false;
 
            string Composite = Info.DocumentNumber + NumberCheck + Info.DateOfBirth + BirthCheck + Info.ExpiryDate + ExpiryCheck + OptionalData;
            if (Match.Groups["OverallCheck"].Value != CalculateCheckDigitText(Composite))
                return false;
 
            Info.OptionalData = OptionalData.Replace("<", string.Empty);
            Info.MRZ_Information = Info.DocumentNumber + NumberCheck + Info.DateOfBirth + BirthCheck + Info.ExpiryDate + ExpiryCheck;
            Info.DocumentNumber = Info.DocumentNumber.Replace("<", string.Empty);
            return true;
        }
 
        private static bool CalcMrzInfo(DocumentInformation Info, Match Match, MrzLayout Layout)
        {
            if (Info.DocumentNumber is null || Info.DateOfBirth is null || Info.ExpiryDate is null)
                return false;
 
            string NumberCheck = Match.Groups["NrCheck"].Value;
            if (NumberCheck != CalculateCheckDigitText(Info.DocumentNumber))
                return false;
 
            string BirthCheck = Match.Groups["BirthCheck"].Value;
            if (BirthCheck != CalculateCheckDigitText(Info.DateOfBirth))
                return false;
 
            string ExpiryCheck = Match.Groups["ExpiryCheck"].Value;
            if (ExpiryCheck != CalculateCheckDigitText(Info.ExpiryDate))
                return false;
 
            string OptionalValue = Match.Groups["Optional"].Value;
            if (Layout == MrzLayout.Td3)
            {
                if (!Match.Groups["OptionalCheck"].Success)
                    return false;
 
                string OptionalCheck = Match.Groups["OptionalCheck"].Value;
                if (OptionalCheck != CalculateCheckDigitText(OptionalValue))
                    return false;
            }
 
            if (Match.Groups["OverallCheck"].Success)
            {
                string Composite = Layout switch
                {
                    MrzLayout.Td2 => Info.DocumentNumber + NumberCheck + Info.DateOfBirth + BirthCheck + Info.ExpiryDate + ExpiryCheck + OptionalValue,
                    MrzLayout.Td3 => Info.DocumentNumber + NumberCheck + Info.DateOfBirth + BirthCheck + Info.ExpiryDate + ExpiryCheck + OptionalValue + Match.Groups["OptionalCheck"].Value,
                    _ => string.Empty
                };
 
                if (Match.Groups["OverallCheck"].Value != CalculateCheckDigitText(Composite))
                    return false;
            }
 
            Info.OptionalData = OptionalValue.Replace("<", string.Empty);
            Info.MRZ_Information = Info.DocumentNumber + NumberCheck + Info.DateOfBirth + BirthCheck + Info.ExpiryDate + ExpiryCheck;
            Info.DocumentNumber = Info.DocumentNumber.Replace("<", string.Empty);
            return true;
        }
 
        private static DocumentInformation AssembleInfo(Match Match)
        {
            DocumentInformation Result = new DocumentInformation
            {
                DocumentType = ExtractDocumentType(Match.Groups["DocType"].Value),
                IssuingState = Match.Groups["Issuer"].Value,
                Nationality = Match.Groups["Nationality"].Value,
                Gender = Match.Groups["Gender"].Value,
                DocumentNumber = Match.Groups["Nr"].Value,
                DateOfBirth = Match.Groups["Birth"].Value,
                ExpiryDate = Match.Groups["Expires"].Value,
                OptionalData = Match.Groups["Optional"].Value
            };
            Result.PrimaryIdentifier = SplitIdentifierPart(Match.Groups["PID"].Value);
            Result.SecondaryIdentifier = SplitIdentifierPart(Match.Groups["SID"].Value);
            return Result;
        }
 
        private static bool TryParseTd2OverflowTail(
            string DocumentNumberPrefix,
            string Tail,
            string DateOfBirth,
            string BirthCheck,
            string ExpiryDate,
            string ExpiryCheck,
            string OverallCheck,
            [NotNullWhen(true)] out string? DocumentNumberSuffix,
            [NotNullWhen(true)] out string? NumberCheck,
            [NotNullWhen(true)] out string? OptionalData)
        {
            for (int CheckDigitIndex = 0; CheckDigitIndex < Tail.Length; CheckDigitIndex++)
            {
                string CandidateSuffix = Tail.Substring(0, CheckDigitIndex);
                string CandidateNumberCheck = Tail.Substring(CheckDigitIndex, 1);
                string CandidateOptionalData = Tail.Substring(CheckDigitIndex + 1);
                string CandidateDocumentNumber = DocumentNumberPrefix + CandidateSuffix;
 
                if (CandidateNumberCheck != CalculateCheckDigitText(CandidateDocumentNumber))
                    continue;
 
                string Composite = CandidateDocumentNumber
                    + CandidateNumberCheck
                    + DateOfBirth
                    + BirthCheck
                    + ExpiryDate
                    + ExpiryCheck
                    + CandidateOptionalData;
                if (OverallCheck != CalculateCheckDigitText(Composite))
                    continue;
 
                DocumentNumberSuffix = CandidateSuffix;
                NumberCheck = CandidateNumberCheck;
                OptionalData = CandidateOptionalData;
                return true;
            }
 
            DocumentNumberSuffix = null;
            NumberCheck = null;
            OptionalData = null;
            return false;
        }
 
        private static readonly int[] Weights = [7, 3, 1];
 
        private delegate DocumentInformation? DocumentInformationFromMatch(Match Match);
 
        private readonly record struct ParserDefinition(
            MrzLayout Layout,
            Regex Pattern,
            DocumentInformationFromMatch Factory);
    }
}