Asn1Document.cs

using System;
using System.IO;
using System.Text;
using System.Collections.Generic;
using System.Globalization;
using Waher.Content.Asn1.Exceptions;
using Waher.Content.Asn1.Model;
using Waher.Content.Asn1.Model.Macro;
using Waher.Content.Asn1.Model.Restrictions;
using Waher.Content.Asn1.Model.Sets;
using Waher.Content.Asn1.Model.Types;
using Waher.Content.Asn1.Model.Values;
using System.Threading.Tasks;
 
namespace Waher.Content.Asn1
{
    public class Asn1Document
    {
        internal readonly Dictionary<string, Asn1Node> namedNodes = new Dictionary<string, Asn1Node>();
        internal readonly Dictionary<string, Asn1TypeDefinition> aliases = new Dictionary<string, Asn1TypeDefinition>();
        internal readonly Dictionary<string, Asn1FieldValueDefinition> values = new Dictionary<string, Asn1FieldValueDefinition>();
        internal int pos = 0;
        private readonly string text;
        private readonly string location;
        private readonly string[] importFolders;
        private readonly int len;
        private readonly int lenm1;
        private Asn1Definitions root;
        private int unnamedIndex = 1;
 
        private Asn1Document(string Text, string Location, string[] ImportFolders)
        {
            this.text = Text;
            this.location = Location;
            this.importFolders = ImportFolders;
            this.len = this.text.Length;
            this.lenm1 = this.len - 1;
        }
 
        public async Task<Asn1Document> CreateAsync(string Text, string Location, string[] ImportFolders)
        {
            Asn1Document Result = new Asn1Document(Text, Location, ImportFolders)
            {
                root = await this.ParseDefinitions()
            };
 
            return Result;
        }
 
        public Asn1Definitions Root => this.root;
 
        public string Text => this.text;
 
        public string Location => this.location;
 
        public string[] ImportFolders => this.importFolders;
 
        public static async Task<Asn1Document> FromFile(string FileName, string[] ImportFolders)
        {
            string Text = await Resources.ReadAllTextAsync(FileName);
            return new Asn1Document(Text, FileName, ImportFolders);
        }
 
        internal void SkipWhiteSpace()
        {
            char ch;
 
            while (this.pos < this.len)
            {
                ch = this.text[this.pos];
 
                if (ch <= ' ' || ch == (char)160)
                    this.pos++;
                else if (ch == '-' && this.pos < this.lenm1 && this.text[this.pos + 1] == '-')
                {
                    this.pos += 2;
 
                    while (this.pos < this.len)
                    {
                        ch = this.text[this.pos];
                        if (ch == '\r' || ch == '\n')
                            break;
 
                        if (ch == '-' && this.pos < this.len - 1 && this.text[this.pos + 1] == '-')
                        {
                            this.pos += 2;
                            break;
                        }
 
                        this.pos++;
                    }
                }
                else if (ch == '/' && this.pos < this.lenm1 && this.text[this.pos + 1] == '*')
                {
                    this.pos += 2;
 
                    while ((this.pos < this.len && this.text[this.pos] != '*') ||
                        (this.pos < this.lenm1 && this.text[this.pos + 1] != '/'))
                    {
                        this.pos++;
                    }
                }
                else
                    break;
            }
        }
 
        internal char NextChar()
        {
            if (this.pos < this.len)
                return this.text[this.pos++];
            else
                return (char)0;
        }
 
        internal char PeekNextChar()
        {
            if (this.pos < this.len)
                return this.text[this.pos];
            else
                return (char)0;
        }
 
        internal string NextToken()
        {
            this.SkipWhiteSpace();
 
            char ch = this.NextChar();
 
            if (char.IsLetter(ch) || char.IsDigit(ch) || ch == '-' || ch == '_')
            {
                int Start = this.pos - 1;
 
                while (this.pos < this.len && (char.IsLetter(ch = this.text[this.pos]) || char.IsDigit(ch) || ch == '-' || ch == '_'))
                    this.pos++;
 
                return this.text.Substring(Start, this.pos - Start);
            }
            else
            {
                switch (ch)
                {
                    case ':':
                        switch (this.PeekNextChar())
                        {
                            case ':':
                                this.pos++;
                                switch (this.PeekNextChar())
                                {
                                    case '=':
                                        this.pos++;
                                        return "::=";
 
                                    default:
                                        return "::";
                                }
 
                            default:
                                return new string(ch, 1);
                        }
 
                    case '.':
                        if (this.PeekNextChar() == '.')
                        {
                            this.pos++;
                            if (this.PeekNextChar() == '.')
                            {
                                this.pos++;
                                return "...";
                            }
                            else
                                return "..";
                        }
                        else
                            return ".";
 
                    case '[':
                        if (this.PeekNextChar() == '[')
                        {
                            this.pos++;
                            return "[[";
                        }
                        else
                            return "[";
 
                    case ']':
                        if (this.PeekNextChar() == ']')
                        {
                            this.pos++;
                            return "]]";
                        }
                        else
                            return "]";
 
                    default:
                        return new string(ch, 1);
                }
            }
        }
 
        internal string PeekNextToken()
        {
            this.SkipWhiteSpace();
 
            int Bak = this.pos;
            string s = this.NextToken();
            this.pos = Bak;
            return s;
        }
 
        internal void AssertNextToken(string ExpectedToken)
        {
            string s = this.NextToken();
            if (s != ExpectedToken)
                throw this.SyntaxError(ExpectedToken + " expected.");
        }
 
        internal Asn1SyntaxException SyntaxError(string Message)
        {
            return new Asn1SyntaxException(Message, this.text, this.pos);
        }
 
        private async Task<Asn1Definitions> ParseDefinitions()
        {
            string Identifier = this.ParseTypeNameIdentifier();
            string s = this.PeekNextToken();
            Asn1Oid Oid = null;
 
            if (s == "{")
            {
                Oid = this.ParseOid();
                s = this.PeekNextToken();
            }
 
            if (s != "DEFINITIONS")
                throw this.SyntaxError("DEFINITIONS expected.");
 
            this.pos += 11;
 
            Asn1Tags? Tags = null;
            bool Abstract = false;
 
            while (true)
            {
                switch (s = this.NextToken())
                {
                    case "AUTOMATIC":
                    case "IMPLICIT":
                    case "EXPLICIT":
                        if (Tags.HasValue)
                            throw this.SyntaxError("TAGS already specified.");
 
                        switch (s)
                        {
                            case "AUTOMATIC":
                                Tags = Asn1Tags.Automatic;
                                break;
 
                            case "IMPLICIT":
                                Tags = Asn1Tags.Implicit;
                                break;
 
                            case "EXPLICIT":
                                Tags = Asn1Tags.Explicit;
                                break;
                        }
 
                        this.AssertNextToken("TAGS");
                        break;
 
                    case "ABSTRACT-SYNTAX":
                        Abstract = true;
                        break;
 
                    case "::=":
                        s = null;
                        break;
 
                    default:
                        throw this.SyntaxError("::= expected.");
                }
 
                if (s is null)
                    break;
            }
 
            Asn1Module Body = await this.ParseModule();
 
            return new Asn1Definitions(Identifier, Oid, Tags, Abstract, Body, this);
        }
 
        private async Task<Asn1Module> ParseModule()
        {
            string s;
 
            this.AssertNextToken("BEGIN");
 
            List<Asn1Import> Imports = null;
            List<string> Exports = null;
 
            do
            {
                s = this.PeekNextToken();
 
                if (s == "IMPORTS")
                {
                    this.pos += 7;
 
                    if (Imports is null)
                        Imports = new List<Asn1Import>();
 
                    List<string> Identifiers = new List<string>();
 
                    do
                    {
                        string Identifier = this.ParseIdentifier();
                        string ModuleRef;
 
                        s = this.PeekNextToken();
 
                        if (s == "FROM")
                        {
                            this.pos += 4;
                            Identifiers.Add(Identifier);
                            ModuleRef = this.ParseTypeNameIdentifier();
 
                            Imports.Add(new Asn1Import(Identifiers.ToArray(), ModuleRef, this));
                            Identifiers.Clear();
 
                            s = this.PeekNextToken();
                            if (s != ";")
                                continue;
                        }
                        else if (s == ".")
                        {
                            this.pos++;
                            ModuleRef = Identifier;
                            Identifier = this.ParseIdentifier();
                            Imports.Add(new Asn1Import(new string[] { ModuleRef }, Identifier, this));
                            s = this.PeekNextToken();
                        }
                        else
                            Identifiers.Add(Identifier);
 
                        if (s == ",")
                        {
                            this.pos++;
                            continue;
                        }
                        else if (s == ";")
                        {
                            this.pos++;
                            break;
                        }
                        else
                            throw this.SyntaxError("Unexpected token.");
                    }
                    while (true);
 
                    if (Identifiers.Count > 0)
                        Imports.Add(new Asn1Import(Identifiers.ToArray(), string.Empty, this));
 
                    foreach (Asn1Import Import in Imports)
                    {
                        Asn1Document Doc = await Import.LoadDocument();
 
                        foreach (string Identifier in Import.Identifiers)
                        {
                            if (!Doc.namedNodes.TryGetValue(Identifier, out Asn1Node ImportedNode))
                                throw this.SyntaxError(Identifier + " not found in " + Import.Module);
 
                            this.namedNodes[Identifier] = ImportedNode;
 
                            if (Doc.aliases.TryGetValue(Identifier, out Asn1TypeDefinition TypeDef))
                                this.aliases[Identifier] = TypeDef;
 
                            if (Doc.values.TryGetValue(Identifier, out Asn1FieldValueDefinition ValueDef))
                                this.values[Identifier] = ValueDef;
                        }
                    }
                }
                else if (s == "EXPORTS")
                {
                    this.pos += 7;
 
                    if (Exports is null)
                        Exports = new List<string>();
 
                    do
                    {
                        string Identifier = this.ParseIdentifier();
                        Exports.Add(Identifier);
 
                        s = this.PeekNextToken();
 
                        if (s == ",")
                        {
                            this.pos++;
                            continue;
                        }
                        else if (s == ";")
                        {
                            this.pos++;
                            break;
                        }
                        else
                            throw this.SyntaxError("; expected");
                    }
                    while (true);
                }
                else
                    break;
            }
            while (true);
 
            List<Asn1Node> Items = new List<Asn1Node>();
 
            while ((s = this.PeekNextToken()) != "END")
            {
                if (string.IsNullOrEmpty(s))
                    throw this.SyntaxError("END expected.");
 
                Asn1Node Node = this.ParseStatement();
                Items.Add(Node);
 
                if (Node is INamedNode NamedNode)
                    this.namedNodes[NamedNode.Name] = Node;
            }
 
            this.pos += 3;
 
            return new Asn1Module(Imports?.ToArray(), Exports?.ToArray(), Items.ToArray());
        }
 
        private Asn1Node ParseStatement()
        {
            string s = this.PeekNextToken();
            if (string.IsNullOrEmpty(s))
                throw this.SyntaxError("Unexpected end of file.");
 
            char ch = s[0];
            string s2;
 
            if (char.IsLetter(ch))
            {
                int PosBak = this.pos;
 
                this.pos += s.Length;
                s2 = this.PeekNextToken();
 
                if (s2 == "::=")
                {
                    if (!char.IsUpper(ch))   // !Type = XML notation
                        throw this.SyntaxError("XML notation not supported.");
 
                    this.pos += s2.Length;
 
                    s2 = this.PeekNextToken();
                }
                else if (s2 == "MACRO")
                {
                    this.pos += 5;
                    this.AssertNextToken("::=");
                    this.AssertNextToken("BEGIN");
                    this.AssertNextToken("TYPE");
                    this.AssertNextToken("NOTATION");
                    this.AssertNextToken("::=");
 
                    UserDefinedItem TypeNotation = this.ParseUserDefinedOptions("VALUE");
 
                    this.AssertNextToken("VALUE");
                    this.AssertNextToken("NOTATION");
                    this.AssertNextToken("::=");
 
                    UserDefinedItem ValueNotation = this.ParseUserDefinedOptions("END");
                    List<SupportingSyntax> SupportingSyntax = new List<SupportingSyntax>();
 
                    while (this.PeekNextToken() != "END")
                    {
                        string Name = this.ParseIdentifier();
                        this.AssertNextToken("::=");
                        SupportingSyntax.Add(new SupportingSyntax(Name, this.ParseUserDefinedOptions("END")));
                    }
 
                    this.AssertNextToken("END");
 
                    return new Asn1Macro(s, TypeNotation, ValueNotation, SupportingSyntax.ToArray(), this);
                }
                else if (this.namedNodes.TryGetValue(s2, out Asn1Node Node) &&
                    Node is Asn1Macro Macro)
                {
                    this.pos += s2.Length;
 
                    Asn1Value Value = Macro.ParseValue(this);
                    Asn1FieldValueDefinition ValueDef = new Asn1FieldValueDefinition(s, Macro.GetValueType(), Value, this);
 
                    this.values[s] = ValueDef;
 
                    return ValueDef;
                }
                else
                {
                    if (char.IsUpper(ch))   // Type or macro
                    {
                        s2 = s;
                        s = "unnamed" + (this.unnamedIndex++).ToString();
                        ch = 'u';
                        this.pos = PosBak;
                    }
                }
 
                int? Tag = null;
                TagClass? Class = null;
 
                if (s2 == "[")
                {
                    this.pos++;
                    s2 = this.NextToken();
 
                    if (s2 == "TAG")
                    {
                        this.AssertNextToken(":");
                        s2 = this.NextToken();
                    }
 
                    switch (s2)
                    {
                        case "APPLICATION":
                            Class = TagClass.Application;
                            s2 = this.NextToken();
                            break;
 
                        case "PRIVATE":
                            Class = TagClass.Private;
                            s2 = this.NextToken();
                            break;
 
                        case "UNIVERSAL":
                            Class = TagClass.Universal;
                            s2 = this.NextToken();
                            break;
                    }
 
                    if (!int.TryParse(s2, out int i))
                        throw this.SyntaxError("Tag expected.");
 
                    if (Class.HasValue)
                        i |= ((int)Class) << 6;
 
                    Tag = i;
 
                    this.AssertNextToken("]");
 
                    s2 = this.PeekNextToken();
                }
 
                if (char.IsUpper(ch))   // Type
                {
                    Asn1Type Definition;
 
                    if (this.namedNodes.TryGetValue(s2, out Asn1Node Node) &&
                        Node is Asn1Macro Macro)
                    {
                        this.pos += s2.Length;
                        Definition = Macro.ParseType(this);
                    }
                    else
                        Definition = this.ParseType(s, true);
 
                    Asn1TypeDefinition TypeDef = new Asn1TypeDefinition(s, Tag, Definition);
 
                    if (!Definition.ConstructedType)
                        this.aliases[s] = TypeDef;
 
                    return TypeDef;
                }
                else                    // name
                {
                    if (!IsTypeIdentifier(s2))
                        throw this.SyntaxError("Type name expected.");
 
                    Asn1Type Type = this.ParseType(s, false);
 
                    if (this.PeekNextToken() == "::=")
                    {
                        this.pos += 3;
                        Asn1Value Value = this.ParseValue();
                        Asn1FieldValueDefinition ValueDef = new Asn1FieldValueDefinition(s, Type, Value, this);
 
                        this.values[s] = ValueDef;
 
                        return ValueDef;
                    }
                    else
                        return new Asn1FieldDefinition(s, Tag, Type);
                }
            }
            else if (s == "...")
            {
                this.pos += 3;
                return new Asn1Extension();
            }
            else
                throw this.SyntaxError("Identifier expected.");
        }
 
        private UserDefinedItem ParseUserDefinedOptions(string EndKeyWord)
        {
            UserDefinedItem Item = this.ParseUserDefinedOption(EndKeyWord);
            List<UserDefinedItem> Options = null;
 
            while (this.PeekNextToken() == "|")
            {
                this.pos++;
 
                if (Options is null)
                    Options = new List<UserDefinedItem>();
 
                Options.Add(Item);
                Item = this.ParseUserDefinedOption(EndKeyWord);
            }
 
            if (Options is null)
                return Item;
            else
            {
                Options.Add(Item);
                return new UserDefinedOptions(Options.ToArray());
            }
        }
 
        private UserDefinedItem ParseUserDefinedOption(string EndKeyWord)
        {
            UserDefinedItem Item = null;
            List<UserDefinedItem> Items = new List<UserDefinedItem>();
            string s;
            int PosBak = this.pos;
 
            while ((s = this.PeekNextToken()) != EndKeyWord && s != "::=" && s != "|")
            {
                if (!(Item is null))
                {
                    if (Items is null)
                        Items = new List<UserDefinedItem>();
 
                    Items.Add(Item);
                }
 
                PosBak = this.pos;
                Item = this.ParseUserDefinedItem();
            }
 
            if (Item is null)
                throw this.SyntaxError("Items expected.");
 
            if (s == "::=")
            {
                if (Items is null)
                    throw this.SyntaxError("Items expected.");
 
                this.pos = PosBak;
                if (Items.Count == 1)
                    return Items[0];
            }
            else if (Items is null)
                return Item;
            else
                Items.Add(Item);
 
            return new UserDefinedOption(Items.ToArray());
        }
 
        private UserDefinedItem ParseUserDefinedItem()
        {
            string s = this.PeekNextToken();
 
            if (s == "\"")
            {
                if (!(this.ParseValue() is Asn1StringValue Label))
                    throw this.SyntaxError("String label expected.");
 
                return new UserDefinedLiteral(Label.Value);
            }
 
            if (!IsIdentifier(s))
                throw this.SyntaxError("Identifier or literal expected.");
 
            this.pos += s.Length;
 
            if (this.PeekNextToken() == "(")
            {
                this.pos++;
 
                string Name = this.ParseIdentifier();
                if (this.PeekNextToken() == ")")
                {
                    this.pos++;
                    return new UserDefinedSpecifiedPart(s, string.Empty, new Asn1TypeReference(Name, this));
                }
                else
                {
                    Asn1Type Type = this.ParseType(Name, false);
 
                    this.AssertNextToken(")");
 
                    return new UserDefinedSpecifiedPart(s, Name, Type);
                }
            }
            else
                return new UserDefinedPart(s);
        }
 
        private Asn1Restriction ParseRestriction()
        {
            this.AssertNextToken("(");
            Asn1Restriction Result = this.ParseOrs();
            this.AssertNextToken(")");
 
            return Result;
        }
 
        private Asn1Restriction ParseOrs()
        {
            Asn1Restriction Result = this.ParseAnds();
 
            string s = this.PeekNextToken();
 
            while (s == "|")
            {
                this.pos++;
                Result = new Asn1Or(Result, this.ParseAnds());
                s = this.PeekNextToken();
            }
 
            return Result;
        }
 
        private Asn1Restriction ParseAnds()
        {
            Asn1Restriction Result = this.ParseRestrictionRule();
 
            string s = this.PeekNextToken();
 
            while (s == "^")
            {
                this.pos++;
                Result = new Asn1And(Result, this.ParseRestrictionRule());
                s = this.PeekNextToken();
            }
 
            return Result;
        }
 
        private Asn1Restriction ParseRestrictionRule()
        {
            string s = this.PeekNextToken();
 
            switch (s)
            {
                case "(":
                    this.pos++;
 
                    Asn1Restriction Result = this.ParseOrs();
                    this.AssertNextToken(")");
 
                    return Result;
 
                case "SIZE":
                    this.pos += 4;
                    return new Asn1Size(this.ParseSet());
 
                case "PATTERN":
                    this.pos += 7;
                    return new Asn1Pattern(this.ParseValue());
 
                case "FROM":
                    this.pos += 4;
                    return new Asn1From(this.ParseSet());
 
                case "CONTAINING":
                    this.pos += 10;
                    return new Asn1Containing(this.ParseValue());
 
                case "ENCODED":
                    this.pos += 7;
                    this.AssertNextToken("BY");
 
                    return new Asn1EncodedBy(this.ParseValue());
 
                case "WITH":
                    this.pos += 4;
                    this.AssertNextToken("COMPONENTS");
 
                    return new Asn1WithComponents(this.ParseValue());
 
                default:
                    return new Asn1InSet(this.ParseUnions());
            }
        }
 
        private Asn1Values ParseSet()
        {
            this.AssertNextToken("(");
            Asn1Values Result = this.ParseUnions();
            this.AssertNextToken(")");
 
            return Result;
        }
 
        private Asn1Values ParseUnions()
        {
            Asn1Values Result = this.ParseIntersections();
 
            string s = this.PeekNextToken();
 
            while (s == "|" || s == "UNION")
            {
                this.pos += s.Length;
                Result = new Asn1Union(Result, this.ParseIntersections());
                s = this.PeekNextToken();
            }
 
            return Result;
        }
 
        private Asn1Values ParseIntersections()
        {
            Asn1Values Result = this.ParseIntervals();
 
            string s = this.PeekNextToken();
 
            while (s == "^" || s == "INTERSECTION")
            {
                this.pos += s.Length;
                Result = new Asn1Union(Result, this.ParseIntervals());
                s = this.PeekNextToken();
            }
 
            return Result;
        }
 
        private Asn1Values ParseIntervals()
        {
            string s = this.PeekNextToken();
 
            if (s == "(")
            {
                this.pos++;
 
                Asn1Values Result = this.ParseUnions();
                this.AssertNextToken(")");
 
                return Result;
            }
            else if (s == "ALL")
            {
                this.pos += 3;
                return new Asn1All();
            }
            else
            {
                Asn1Value Value = this.ParseValue();
 
                if (this.PeekNextToken() == "..")
                {
                    this.pos += 2;
                    Asn1Value Value2 = this.ParseValue();
 
                    return new Asn1Interval(Value, Value2);
                }
                else
                    return new Asn1Element(Value);
            }
        }
 
        private string ParseIdentifier()
        {
            string s = this.NextToken();
 
            if (!IsIdentifier(s))
                throw this.SyntaxError("Identifier expected.");
 
            return s;
        }
 
        private string ParseTypeNameIdentifier()
        {
            string s = this.NextToken();
 
            if (!IsTypeIdentifier(s))
                throw this.SyntaxError("Type name identifier expected.");
 
            return s;
        }
 
        private static bool IsIdentifier(string s)
        {
            return !string.IsNullOrEmpty(s) && char.IsLetter(s[0]);
        }
 
        private static bool IsTypeIdentifier(string s)
        {
            char ch;
            return !string.IsNullOrEmpty(s) && char.IsLetter(ch = s[0]) && char.IsUpper(ch);
        }
 
        private static bool IsFieldIdentifier(string s)
        {
            char ch;
            return !string.IsNullOrEmpty(s) && char.IsLetter(ch = s[0]) && char.IsLower(ch);
        }
 
        private Asn1Oid ParseOid()
        {
            Asn1Node[] Values = this.ParseValues();
            return new Asn1Oid(Values);
        }
 
        internal Asn1Type ParseType(string Name, bool TypeDef)
        {
            bool Implicit = false;
 
            switch (this.PeekNextToken())
            {
                case "IMPLICIT":
                    this.pos += 8;
                    Implicit = true;
                    break;
            }
 
            Asn1Type Result = this.ParseDataType(Name, TypeDef);
            Result.Implicit = Implicit;
 
            string s2;
 
            while (true)
            {
                s2 = this.PeekNextToken();
 
                switch (s2)
                {
                    case "(":
                        Result.Restriction = this.ParseRestriction();
                        break;
 
                    case "{":
                        this.pos++;
 
                        List<Asn1NamedValue> NamedOptions = new List<Asn1NamedValue>();
 
                        while (true)
                        {
                            s2 = this.NextToken();
                            if (!IsFieldIdentifier(s2))
                                throw this.SyntaxError("Value name expected.");
 
                            if (this.PeekNextToken() == "(")
                            {
                                this.pos++;
 
                                NamedOptions.Add(new Asn1NamedValue(s2, this.ParseValue(), this));
 
                                if (this.NextToken() != ")")
                                    throw this.SyntaxError(") expected");
                            }
                            else
                                NamedOptions.Add(new Asn1NamedValue(s2, null, this));
 
                            s2 = this.NextToken();
 
                            if (s2 == ",")
                                continue;
                            else if (s2 == "}")
                            {
                                Result.NamedOptions = NamedOptions.ToArray();
                                break;
                            }
                            else
                                throw this.SyntaxError("Unexpected token.");
                        }
                        break;
 
                    case "OPTIONAL":
                        this.pos += 8;
                        Result.Optional = true;
                        break;
 
                    case "PRESENT":
                        this.pos += 7;
                        Result.Present = true;
                        break;
 
                    case "ABSENT":
                        this.pos += 6;
                        Result.Absent = true;
                        break;
 
                    case "DEFAULT":
                        this.pos += 7;
                        Result.Optional = true;
                        Result.Default = this.ParseValue();
                        break;
 
                    case "UNIQUE":
                        this.pos += 6;
                        Result.Unique = true;
                        break;
 
                    default:
                        return Result;
                }
            }
        }
 
        private Asn1Type ParseDataType(string Name, bool TypeDef)
        {
            string s = this.NextToken();
            if (string.IsNullOrEmpty(s))
                throw this.SyntaxError("Unexpected end of file.");
 
            switch (s)
            {
                case "ANY":
                    return new Asn1Any();
 
                case "BIT":
                    this.AssertNextToken("STRING");
                    return new Asn1BitString();
 
                case "BMPString":
                    return new Asn1BmpString();
 
                case "BOOLEAN":
                    return new Asn1Boolean();
 
                case "CHARACTER":
                    return new Asn1Character();
 
                case "CHOICE":
                    s = this.PeekNextToken();
 
                    if (s == "{")
                    {
                        Asn1Node[] Nodes = this.ParseList();
 
                        foreach (Asn1Node Node in Nodes)
                        {
                            if (Node is Asn1FieldDefinition FieldDef && !this.namedNodes.ContainsKey(FieldDef.Name))
                                this.namedNodes[FieldDef.Name] = FieldDef;
                        }
 
                        return new Asn1Choice(Name, TypeDef, Nodes);
                    }
                    else
                        throw this.SyntaxError("{ expected.");
 
                case "DATE":
                    return new Asn1Date();
 
                case "DATE-TIME":
                    return new Asn1DateTime();
 
                case "DURATION":
                    return new Asn1Duration();
 
                case "ENUMERATED":
                    s = this.PeekNextToken();
 
                    if (s == "{")
                    {
                        Asn1Node[] Nodes = this.ParseValues();
                        return new Asn1Enumeration(Name, TypeDef, Nodes);
                    }
                    else
                        throw this.SyntaxError("{ expected.");
 
                case "GeneralizedTime":
                    return new Asn1GeneralizedTime();
 
                case "GeneralString":
                    return new Asn1GeneralString();
 
                case "GraphicString":
                    return new Asn1GraphicString();
 
                case "IA5String":
                    return new Asn1Ia5String();
 
                case "INTEGER":
                    return new Asn1Integer();
 
                case "ISO646String":
                    return new Asn1Iso646String();
 
                case "NULL":
                    return new Asn1Null();
 
                case "NumericString":
                    return new Asn1NumericString();
 
                case "OBJECT":
                    this.AssertNextToken("IDENTIFIER");
                    return new Asn1ObjectIdentifier(false);
 
                case "OCTET":
                    this.AssertNextToken("STRING");
                    return new Asn1OctetString();
 
                case "PrintableString":
                    return new Asn1PrintableString();
 
                case "REAL":
                    return new Asn1Real();
 
                case "RELATIVE":
                    this.AssertNextToken("OID");
                    return new Asn1ObjectIdentifier(true);
 
                case "RELATIVE-OID":
                    return new Asn1ObjectIdentifier(true);
 
                case "SET":
                    s = this.PeekNextToken();
 
                    if (s == "{")
                    {
                        Asn1Node[] Nodes = this.ParseList();
                        return new Asn1Set(Name, TypeDef, Nodes);
                    }
                    else if (s == "(")
                    {
                        this.pos++;
 
                        Asn1Values Size = null;
 
                        while (true)
                        {
                            s = this.PeekNextToken();
 
                            if (s == "SIZE")
                            {
                                if (!(Size is null))
                                    throw this.SyntaxError("SIZE already specified.");
 
                                this.pos += 4;
                                Size = this.ParseSet();
                            }
                            else if (s == ")")
                            {
                                this.pos++;
                                break;
                            }
                            else
                                throw this.SyntaxError("Unexpected token.");
                        }
 
                        this.AssertNextToken("OF");
 
                        if (Size is null)
                            throw this.SyntaxError("SIZE expected.");
 
                        s = this.ParseTypeNameIdentifier();
 
                        return new Asn1SetOf(Size, s);
                    }
                    else
                        throw this.SyntaxError("{ expected.");
 
                case "SEQUENCE":
                    s = this.PeekNextToken();
 
                    if (s == "{")
                    {
                        Asn1Node[] Nodes = this.ParseList();
                        return new Asn1Sequence(Name, TypeDef, Nodes);
                    }
                    else
                    {
                        Asn1Values Size = null;
 
                        if (s == "(")
                        {
                            this.pos++;
 
                            while (true)
                            {
                                s = this.PeekNextToken();
 
                                if (s == "SIZE")
                                {
                                    if (!(Size is null))
                                        throw this.SyntaxError("SIZE already specified.");
 
                                    this.pos += 4;
                                    Size = this.ParseSet();
                                }
                                else if (s == ")")
                                {
                                    this.pos++;
                                    break;
                                }
                                else
                                    throw this.SyntaxError("Unexpected token.");
                            }
                        }
 
                        if (this.NextToken() != "OF")
                            throw this.SyntaxError("Unexpected token.");
 
                        return new Asn1SequenceOf(Name, TypeDef, Size, this.ParseType(Name, TypeDef));
                    }
 
                case "T61String":
                    return new Asn1T61String();
 
                case "TeletexString":
                    return new Asn1TeletexString();
 
                case "TIME-OF-DAY":
                    return new Asn1TimeOfDay();
 
                case "UniversalString":
                    return new Asn1UniversalString();
 
                case "UTCTime":
                    return new Asn1UtcTime();
 
                case "UTF8String":
                    return new Asn1Utf8String();
 
                case "VideotexString":
                    return new Asn1VideotexString();
 
                case "VisibleString":
                    return new Asn1VisibleString();
 
                case "ObjectDescriptor":
                case "EXTERNAL":
                case "EMBEDDED":
                case "CLASS":
                case "COMPONENTS":
                case "INSTANCE":
                case "OID-IRI":
                    throw this.SyntaxError("Token not implemented.");
 
                default:
                    if (char.IsUpper(s[0]))
                        return new Asn1TypeReference(s, this);
                    else
                        throw this.SyntaxError("Type name expected.");
            }
        }
 
        private Asn1Node[] ParseList()
        {
            this.AssertNextToken("{");
 
            List<Asn1Node> Items = new List<Asn1Node>();
 
            while (true)
            {
                Items.Add(this.ParseStatement());
 
                switch (this.PeekNextToken())
                {
                    case ",":
                        this.pos++;
                        continue;
 
                    case "}":
                        this.pos++;
                        return Items.ToArray();
 
                    default:
                        throw this.SyntaxError(", or } expected.");
                }
            }
        }
 
        private Asn1Node[] ParseValues()
        {
            this.AssertNextToken("{");
 
            List<Asn1Node> Items = new List<Asn1Node>();
 
            while (true)
            {
                Items.Add(this.ParseValue());
 
                switch (this.PeekNextToken())
                {
                    case ",":
                        this.pos++;
                        continue;
 
                    case "}":
                        this.pos++;
                        return Items.ToArray();
 
                    case "(":
                        this.pos++;
                        Asn1Value Value = this.ParseValue();
                        this.AssertNextToken(")");
 
                        int LastIndex = Items.Count - 1;
 
                        if (Items[LastIndex] is Asn1ValueReference Ref)
                            Items[LastIndex] = new Asn1NamedValue(Ref.Identifier, Value, this);
                        else
                            throw this.SyntaxError("Invalid value reference.");
                        break;
 
                    default:
                        throw this.SyntaxError(", or } expected.");
                }
            }
        }
 
        internal Asn1Value ParseValue()
        {
            return this.ParseValue(true);
        }
 
        private Asn1Value ParseValue(bool AllowNamed)
        {
            string s = this.PeekNextToken();
            if (string.IsNullOrEmpty(s))
                throw this.SyntaxError("Expected value.");
 
            switch (s)
            {
                case "FALSE":
                    this.pos += 5;
                    return new Asn1BooleanValue(false);
 
                case "MAX":
                    this.pos += 3;
                    return new Asn1Max();
 
                case "MIN":
                    this.pos += 3;
                    return new Asn1Min();
 
                case "TRUE":
                    this.pos += 4;
                    return new Asn1BooleanValue(true);
 
                case "INF":
                    this.pos += 3;
                    return new Asn1FloatingPointValue(double.PositiveInfinity);
 
                case "NaN":
                    this.pos += 3;
                    return new Asn1FloatingPointValue(double.NaN);
 
                case "...":
                    this.pos += 3;
                    return new Asn1Extension();
 
                case "\"":
                    int Start = ++this.pos;
                    char ch;
 
                    while (this.pos < this.len && this.text[this.pos] != '"')
                        this.pos++;
 
                    if (this.pos >= this.len)
                        throw this.SyntaxError("\" expected.");
 
                    s = this.text.Substring(Start, this.pos - Start);
                    this.pos++;
 
                    return new Asn1StringValue(s);
 
                case "'":
                    Start = ++this.pos;
 
                    while (this.pos < this.len && this.text[this.pos] != '\'')
                        this.pos++;
 
                    if (this.pos >= this.len)
                        throw this.SyntaxError("' expected.");
 
                    s = this.text.Substring(Start, this.pos - Start);
                    this.pos++;
 
                    switch (this.NextToken())
                    {
                        case "H":
                        case "h":
                            this.pos++;
                            if (long.TryParse(s, NumberStyles.HexNumber, null, out long l))
                                return new Asn1IntegerValue(l);
                            else
                                throw this.SyntaxError("Invalid hexadecimal string.");
 
                        case "D":
                        case "d":
                            this.pos++;
                            if (long.TryParse(s, out l))
                                return new Asn1IntegerValue(l);
                            else
                                throw this.SyntaxError("Invalid decimal string.");
 
                        case "B":
                        case "b":
                            this.pos++;
                            if (TryParseBinary(s, out l))
                                return new Asn1IntegerValue(l);
                            else
                                throw this.SyntaxError("Invalid binary string.");
 
                        case "O":
                        case "o":
                            this.pos++;
                            if (TryParseOctal(s, out l))
                                return new Asn1IntegerValue(l);
                            else
                                throw this.SyntaxError("Invalid octal string.");
 
                        default:
                            throw this.SyntaxError("Unexpected token.");
                    }
 
                case "{":
                    this.pos++;
 
                    List<Asn1Value> Items = new List<Asn1Value>();
                    bool Oid = false;
 
                    while (true)
                    {
                        Asn1Value Value = this.ParseValue();
 
                        s = this.PeekNextToken();
 
                        switch (s)
                        {
                            case ",":
                                this.pos++;
                                Items.Add(Value);
                                break;
 
                            case "}":
                                this.pos++;
                                Items.Add(Value);
 
                                if (Oid)
                                    return new Asn1Oid(Items.ToArray());
                                else
                                    return new Asn1Array(Items.ToArray());
 
                            default:
                                if (Items.Count == 0)
                                    Oid = true;
 
                                if (Oid)
                                    Items.Add(Value);
                                else
                                    throw this.SyntaxError("Unexpected token.");
                                break;
                        }
                    }
 
                default:
                    if (char.IsLetter(s[0]))
                    {
                        this.pos += s.Length;
 
                        switch (this.PeekNextToken())
                        {
                            case ":":
                                if (!AllowNamed)
                                    throw this.SyntaxError("Value expected.");
 
                                this.pos++;
                                Asn1Value Value = this.ParseValue(false);
                                return new Asn1NamedValue(s, Value, this);
 
                            case "(":
                                Asn1Restriction Restriction = this.ParseRestriction();
 
                                if (Restriction is Asn1InSet Set && Set.Set is Asn1Element Element)
                                    return new Asn1NamedValue(s, Element.Element, this);
                                else
                                    return new Asn1RestrictedValueReference(s, Restriction, this);
 
                            default:
                                if (!char.IsUpper(s[0]))
                                    return new Asn1ValueReference(s, this);
                                else
                                    throw this.SyntaxError("Type references not permitted here.");
                        }
                    }
                    else
                    {
                        Start = this.pos;
 
                        bool Sign = s.StartsWith("-");
                        if (Sign)
                        {
                            s = s.Substring(1);
                            this.pos++;
                        }
 
                        if (ulong.TryParse(s, out ulong l))
                        {
                            this.pos += s.Length;
 
                            ch = this.PeekNextChar();
 
                            if ((ch == '.' && this.pos < this.lenm1 && this.text[this.pos + 1] != '.') ||
                                ch == 'e' || ch == 'E')
                            {
                                int? DecPos = null;
 
                                if (ch == '.')
                                {
                                    DecPos = this.pos++;
                                    while (this.pos < this.len && char.IsDigit(ch = this.text[this.pos]))
                                        this.pos++;
                                }
 
                                if (ch == 'e' || ch == 'E')
                                {
                                    this.pos++;
 
                                    if ((ch = this.PeekNextChar()) == '-' || ch == '+')
                                        this.pos++;
 
                                    while (this.pos < this.len && char.IsDigit(this.text[this.pos]))
                                        this.pos++;
                                }
 
                                s = this.text.Substring(Start, this.pos - Start);
 
                                string s2 = NumberFormatInfo.CurrentInfo.CurrencyDecimalSeparator;
                                if (DecPos.HasValue && s2 != ".")
                                    s = s.Replace(".", s2);
 
                                if (!double.TryParse(s, out double d))
                                    throw this.SyntaxError("Invalid floating-point number.");
 
                                return new Asn1FloatingPointValue(d);
                            }
 
                            if (l <= long.MaxValue)
                                return new Asn1IntegerValue(Sign ? -(long)l : (long)l);
                            else if (Sign)
                                throw this.SyntaxError("Number does not fit into a 64-bit signed integer.");
                            else
                                return new Asn1UnsignedIntegerValue(l);
                        }
                    }
                    break;
            }
 
            throw this.SyntaxError("Value expected.");
        }
 
        private static bool TryParseBinary(string s, out long l)
        {
            l = 0;
 
            foreach (char ch in s)
            {
                if (ch < '0' || ch > '1')
                    return false;
 
                long l2 = l;
                l <<= 1;
                if (l < l2)
                    return false;
 
                l |= (byte)(ch - '0');
            }
 
            return true;
        }
 
        private static bool TryParseOctal(string s, out long l)
        {
            l = 0;
 
            foreach (char ch in s)
            {
                if (ch < '0' || ch > '7')
                    return false;
 
                long l2 = l;
                l <<= 3;
                if (l < l2)
                    return false;
 
                l |= (byte)(ch - '0');
            }
 
            return true;
        }
 
        public string ExportCSharp(CSharpExportSettings Settings)
        {
            StringBuilder Output = new StringBuilder();
            this.ExportCSharp(Output, Settings);
            return Output.ToString();
        }
 
        public void ExportCSharp(StringBuilder Output, CSharpExportSettings Settings)
        {
            CSharpExportState State = new CSharpExportState(Settings);
 
            Output.AppendLine("using System;");
            Output.AppendLine("using System.Text;");
            Output.AppendLine("using System.Collections.Generic;");
            Output.AppendLine("using Waher.Content;");
            Output.AppendLine("using Waher.Content.Asn1;");
 
            this.root?.ExportCSharp(Output, State, 0, CSharpExportPass.Explicit);
        }
    }
}