From 8d30b1626b6c53b7ea32105c00a065ed3c32f3dd Mon Sep 17 00:00:00 2001
From: jackfiled <xcrenchangjun@outlook.com>
Date: Sat, 9 Mar 2024 23:57:43 +0800
Subject: [PATCH] add: Terminator and Expression

---
 Canon.Core/Enums/GrammarEnums.cs       |  37 +++++++
 Canon.Core/GrammarParser/Expression.cs |  78 ++++++++++++++
 Canon.Core/GrammarParser/Terminator.cs | 137 +++++++++++++++++++++++++
 3 files changed, 252 insertions(+)
 create mode 100644 Canon.Core/Enums/GrammarEnums.cs
 create mode 100644 Canon.Core/GrammarParser/Expression.cs
 create mode 100644 Canon.Core/GrammarParser/Terminator.cs

diff --git a/Canon.Core/Enums/GrammarEnums.cs b/Canon.Core/Enums/GrammarEnums.cs
new file mode 100644
index 0000000..e438969
--- /dev/null
+++ b/Canon.Core/Enums/GrammarEnums.cs
@@ -0,0 +1,37 @@
+namespace Canon.Core.Enums;
+
+public enum NonTerminatorType
+{
+    ProgramStruct,
+    ProgramHead,
+    ProgramBody,
+    IdentifierList,
+    ConstDeclarations,
+    VarDeclarations,
+    SubprogramDeclarations,
+    CompoundStatement,
+    ConstDeclaration,
+    ConstValue,
+    VarDeclaration,
+    Type,
+    BasicType,
+    Range,
+    Subprogram,
+    SubprogramHead,
+    SubprogramBody,
+    FormalParameter,
+    ParameterList,
+    Parameter,
+    VarParameter,
+    ValueParameter,
+    StatementList,
+    Statement,
+    Variable,
+    Expression,
+    ProcedureCall,
+    ElsePart,
+    ExpressionList,
+    SimpleExpression,
+    Term,
+    Factor
+}
diff --git a/Canon.Core/GrammarParser/Expression.cs b/Canon.Core/GrammarParser/Expression.cs
new file mode 100644
index 0000000..096163f
--- /dev/null
+++ b/Canon.Core/GrammarParser/Expression.cs
@@ -0,0 +1,78 @@
+namespace Canon.Core.GrammarParser;
+
+/// <summary>
+/// An expression in the LR, like 'program_struct -> ~program_head ; program_body.'
+/// The '~' is the shift position now.
+/// </summary>
+public class Expression : IEquatable<Expression>
+{
+    public required NonTerminator Left { get; init; }
+
+    public required Terminator LookAhead { get; init; }
+
+    public required List<TerminatorBase> Right { get; init; }
+
+    public int Pos { get; set; }
+
+    public bool Equals(Expression? other)
+    {
+        if (other is null)
+        {
+            return false;
+        }
+
+        if (Right.Count != other.Right.Count)
+        {
+            return false;
+        }
+
+        for (int i = 0; i < Right.Count; i++)
+        {
+            if (Right[i].IsTerminated != other.Right[i].IsTerminated)
+            {
+                return false;
+            }
+
+            if (!Right[i].Equals(other.Right[i]))
+            {
+                return false;
+            }
+        }
+
+        return Left == other.Left
+               && LookAhead == other.LookAhead;
+    }
+
+    public override bool Equals(object? obj)
+    {
+        if (obj is not Expression other)
+        {
+            return false;
+        }
+
+        return Equals(other);
+    }
+
+    public override int GetHashCode()
+    {
+        int hash = Left.GetHashCode();
+        hash ^= LookAhead.GetHashCode();
+
+        foreach (TerminatorBase terminator in Right)
+        {
+            hash ^= terminator.GetHashCode();
+        }
+
+        return hash;
+    }
+
+    public static bool operator ==(Expression a, Expression b)
+    {
+        return a.Equals(b);
+    }
+
+    public static bool operator !=(Expression a, Expression b)
+    {
+        return !a.Equals(b);
+    }
+}
diff --git a/Canon.Core/GrammarParser/Terminator.cs b/Canon.Core/GrammarParser/Terminator.cs
new file mode 100644
index 0000000..0ff1257
--- /dev/null
+++ b/Canon.Core/GrammarParser/Terminator.cs
@@ -0,0 +1,137 @@
+using Canon.Core.Enums;
+
+namespace Canon.Core.GrammarParser;
+
+public abstract class TerminatorBase
+{
+    public abstract bool IsTerminated { get; }
+}
+
+/// <summary>
+/// A terminator in grammar and it always represents a semantic token.
+/// </summary>
+public class Terminator : TerminatorBase, IEquatable<Terminator>
+{
+    public override bool IsTerminated => true;
+
+    private readonly bool _isKeyword;
+
+    private readonly KeywordType _keywordType;
+    private readonly DelimiterType _delimiterType;
+
+    public Terminator(KeywordType keywordType)
+    {
+        _isKeyword = true;
+        _keywordType = keywordType;
+    }
+
+    public Terminator(DelimiterType delimiterType)
+    {
+        _isKeyword = false;
+        _delimiterType = delimiterType;
+    }
+
+    public override int GetHashCode()
+    {
+        if (_isKeyword)
+        {
+            return _keywordType.GetHashCode();
+        }
+        else
+        {
+            return _delimiterType.GetHashCode();
+        }
+    }
+
+    public bool Equals(Terminator? other)
+    {
+        if (other is null)
+        {
+            return false;
+        }
+
+        if (_isKeyword != other._isKeyword)
+        {
+            return false;
+        }
+
+        if (_isKeyword)
+        {
+            return _keywordType == other._keywordType;
+        }
+        else
+        {
+            return _delimiterType == other._delimiterType;
+        }
+    }
+
+    public override bool Equals(object? obj)
+    {
+        if (obj is not Terminator other)
+        {
+            return false;
+        }
+
+        return Equals(other);
+    }
+
+    public static bool operator ==(Terminator a, Terminator b)
+    {
+        return a.Equals(b);
+    }
+
+    public static bool operator !=(Terminator a, Terminator b)
+    {
+        return !a.Equals(b);
+    }
+}
+
+/// <summary>
+/// A non-terminator in grammar like the 'ProgramStruct'.
+/// </summary>
+public class NonTerminator : TerminatorBase, IEquatable<NonTerminator>
+{
+    public override bool IsTerminated => false;
+
+    private readonly NonTerminatorType _type;
+
+    public NonTerminator(NonTerminatorType type)
+    {
+        _type = type;
+    }
+
+    public override int GetHashCode()
+    {
+        return _type.GetHashCode();
+    }
+
+    public bool Equals(NonTerminator? other)
+    {
+        if (other is null)
+        {
+            return false;
+        }
+
+        return _type == other._type;
+    }
+
+    public override bool Equals(object? obj)
+    {
+        if (obj is not NonTerminator other)
+        {
+            return false;
+        }
+
+        return Equals(other);
+    }
+
+    public static bool operator ==(NonTerminator a, NonTerminator b)
+    {
+        return a.Equals(b);
+    }
+
+    public static bool operator !=(NonTerminator a, NonTerminator b)
+    {
+        return !a.Equals(b);
+    }
+}