CanonSharp/CanonSharp.Pascal/Parser/GrammarParser.cs

using CanonSharp.Combinator.Abstractions;
using CanonSharp.Combinator.Extensions;
using static CanonSharp.Combinator.ParserBuilder;
using CanonSharp.Pascal.Scanner;
using CanonSharp.Pascal.SyntaxTree;

namespace CanonSharp.Pascal.Parser;

public sealed class GrammarParser : GrammarParserBuilder
{
    public Program Parse(IEnumerable<LexicalToken> tokens)
    {
        IParseResult<LexicalToken, Program> result = ProgramParser().Parse(new LexicalTokenReadState(tokens));

        return result.Value;
    }

    public static IParser<LexicalToken, SyntaxNodeBase> FactorParser()
    {
        // factor -> - factor | + factor
        IParser<LexicalToken, SyntaxNodeBase> minusParser =
            from _ in Operator("-")
            from node in FactorParser()
            select new UnaryOperatorNode(UnaryOperatorType.Minus, node);

        IParser<LexicalToken, SyntaxNodeBase> plusParser =
            from _ in Operator("+")
            from node in FactorParser()
            select new UnaryOperatorNode(UnaryOperatorType.Plus, node);

        IParser<LexicalToken, SyntaxNodeBase> notParser =
            from _ in Keyword("not")
            from node in FactorParser()
            select new UnaryOperatorNode(UnaryOperatorType.Not, node);

        IParser<LexicalToken, SyntaxNodeBase> parenthesisParser =
            from _1 in Delimiter("(")
            from node in ExpressionParser()
            from _2 in Delimiter(")")
            select node;

        IParser<LexicalToken, SyntaxNodeBase> procedureCallParser =
            from identifier in IdentifierParser()
            from _ in Delimiter("(")
            from expressions in ExpressionParser().SeparatedBy(Delimiter(","))
            from _1 in Delimiter(")")
            select new ProcedureCallNode(identifier, expressions);

        return Choice(
            TrueParser(),
            FalseParser(),
            NumberParser(),
            minusParser,
            plusParser,
            notParser,
            procedureCallParser,
            VariableParser(),
            parenthesisParser
        );
    }

    private static IParser<LexicalToken, SyntaxNodeBase> TermRecursively(SyntaxNodeBase left)
    {
        // MultiplyOperator -> * | / | div | mod | and
        IParser<LexicalToken, BinaryOperatorType> multiplyOperator = Choice(
            from _ in Operator("*")
            select BinaryOperatorType.Multiply,
            from _ in Operator("/")
            select BinaryOperatorType.Divide,
            from _ in Keyword("div")
            select BinaryOperatorType.IntegerDivide,
            from _ in Keyword("mod")
            select BinaryOperatorType.Mod,
            from _ in Keyword("and")
            select BinaryOperatorType.And);

        return multiplyOperator.Next(op =>
        {
            return FactorParser().Map(right => new BinaryOperatorNode(op, left, right))
                .Bind(TermRecursively);
        }, left);
    }

    public static IParser<LexicalToken, SyntaxNodeBase> TermParser()
    {
        // Term -> Factor | Term MultiplyOperator Factor
        // 消除左递归为
        // Term -> Factor Term'
        // Term' -> MultiplyOperator Factor Term' | ε
        return FactorParser().Bind(TermRecursively);
    }

    private static IParser<LexicalToken, SyntaxNodeBase> SimpleExpressionRecursively(SyntaxNodeBase left)
    {
        // AddOperator -> + | - | or
        IParser<LexicalToken, BinaryOperatorType> addOperator = Choice(
            from _ in Operator("+")
            select BinaryOperatorType.Add,
            from _ in Operator("-")
            select BinaryOperatorType.Subtract,
            from _ in Keyword("or")
            select BinaryOperatorType.Or);

        return addOperator.Next(op =>
        {
            return TermParser().Map(right => new BinaryOperatorNode(op, left, right))
                .Bind(SimpleExpressionRecursively);
        }, left);
    }

    public static IParser<LexicalToken, SyntaxNodeBase> SimpleExpressionParser()
    {
        // SimpleExpression -> Term | SimpleExpression AddOperator Term
        // 消除左递归为
        // SimpleExpression -> Term SimpleExpression'
        // SimpleExpression' -> AddOperator Term SimpleExpression' | ε
        return TermParser().Bind(SimpleExpressionRecursively);
    }

    public static IParser<LexicalToken, SyntaxNodeBase> ExpressionParser()
    {
        // RelationOperator -> = | <> | < | <= | > | >=
        IParser<LexicalToken, BinaryOperatorType> relationOperator = Choice(
            from _ in Operator("=")
            select BinaryOperatorType.Equal,
            from _ in Operator("<>")
            select BinaryOperatorType.NotEqual,
            from _ in Operator("<")
            select BinaryOperatorType.Less,
            from _ in Operator("<=")
            select BinaryOperatorType.LessEqual,
            from _ in Operator(">")
            select BinaryOperatorType.Greater,
            from _ in Operator(">=")
            select BinaryOperatorType.GreaterEqual);

        // Expression -> SimpleExpression | SimpleExpression RelationOperator SimpleExpression
        return Choice(
            from left in SimpleExpressionParser()
            from op in relationOperator
            from right in SimpleExpressionParser()
            select new BinaryOperatorNode(op, left, right),
            SimpleExpressionParser()
        );
    }

    /// <summary>
    /// ExpressionList Parser
    /// ExpressionList -> Expression | ExpressionList , Expression
    /// </summary>
    /// <returns></returns>
    public static IParser<LexicalToken, IEnumerable<SyntaxNodeBase>> ExpressionsParser()
        => ExpressionParser().SeparatedBy1(Delimiter(","));

    public static IParser<LexicalToken, VariableNode> VariableParser()
    {
        return Choice(
            from token in IdentifierParser()
            from _ in Delimiter("[")
            from expressions in ExpressionsParser()
            from _1 in Delimiter("]")
            select new VariableNode(token, expressions),
            from token in IdentifierParser()
            select new VariableNode(token)
        );
    }

    public static IParser<LexicalToken, IfNode> IfParser()
    {
        IParser<LexicalToken, IfNode> commonPart = from _ in Keyword("if")
            from condition in ExpressionParser()
            from _1 in Keyword("then")
            from statement in StatementParser()
            select new IfNode(condition, statement);

        return Choice(
            from common in commonPart
            from _ in Keyword("else")
            from elseStatement in StatementParser()
            select new IfNode(common.Condition, common.Statement, elseStatement),
            commonPart
        );
    }

    public static IParser<LexicalToken, ForNode> ForParser()
    {
        return from _ in Keyword("for")
            from identifier in IdentifierParser()
            from _1 in Operator(":=")
            from left in ExpressionParser()
            from _2 in Keyword("to")
            from right in ExpressionParser()
            from _3 in Keyword("do")
            from statement in StatementParser()
            select new ForNode(identifier, left, right, statement);
    }

    public static IParser<LexicalToken, WhileNode> WhileParser()
    {
        return from _ in Keyword("while")
            from condition in ExpressionParser()
            from _1 in Keyword("do")
            from statement in StatementParser()
            select new WhileNode(condition, statement);
    }

    public static IParser<LexicalToken, ProcedureCallNode> ProcedureCallParser()
    {
        return Choice(
            from identifier in IdentifierParser()
            from _ in Delimiter("(")
            from expressions in ExpressionParser().SeparatedBy(Delimiter(","))
            from _1 in Delimiter(")")
            select new ProcedureCallNode(identifier, expressions),
            from identifier in IdentifierParser()
            select new ProcedureCallNode(identifier, [])
        );
    }

    public static IParser<LexicalToken, SyntaxNodeBase> StatementParser()
    {
        return Choice<LexicalToken, SyntaxNodeBase>(
            from variable in VariableParser()
            from _ in Operator(":=")
            from expression in ExpressionParser()
            select new AssignNode(variable, expression),
            ProcedureCallParser(),
            IfParser(),
            ForParser(),
            WhileParser(),
            CompoundStatementParser()
        );
    }

    public static IParser<LexicalToken, BlockNode> CompoundStatementParser()
    {
        return from _1 in Keyword("begin")
            from statements in StatementParser().SeparatedOrEndBy(Delimiter(";"))
            from _2 in Keyword("end")
            select new BlockNode(statements);
    }

    public static IParser<LexicalToken, SyntaxNodeBase> ConstValueParser()
    {
        return Choice(
            from _ in Operator("-")
            from num in NumberParser()
            select new UnaryOperatorNode(UnaryOperatorType.Minus, num),
            from _ in Operator("+")
            from num in NumberParser()
            select new UnaryOperatorNode(UnaryOperatorType.Plus, num),
            NumberParser(),
            CharParser(),
            TrueParser(),
            FalseParser()
        );
    }

    public static IParser<LexicalToken, SyntaxNodeBase> ConstDeclarationParser()
    {
        return from identifier in Satisfy<LexicalToken>(token =>
                token.TokenType == LexicalTokenType.Identifier)
            from _ in Operator("=")
            from node in ConstValueParser()
            select new ConstantNode(identifier, node);
    }

    public static IParser<LexicalToken, BlockNode> ConstDeclarationsParser()
    {
        return (from _ in Keyword("const")
            from tokens in ConstDeclarationParser().SeparatedOrEndBy1(Delimiter(";"))
            select new BlockNode(tokens)).Try(new BlockNode([]));
    }

    public static IParser<LexicalToken, TypeNode> ArrayTypeParser()
    {
        IParser<LexicalToken, IEnumerable<ArrayRange>> arrayRangeParser = (
            from left in IntegerParser()
            from _ in Delimiter("..")
            from right in IntegerParser()
            select new ArrayRange(left.Value, right.Value)).SeparatedBy1(Delimiter(","));

        return from _ in Keyword("array")
            from _1 in Delimiter("[")
            from ranges in arrayRangeParser
            from _2 in Delimiter("]")
            from _3 in Keyword("of")
            from typeToken in BasicTypeParser()
            select new TypeNode(typeToken, ranges);
    }

    public static IParser<LexicalToken, SyntaxNodeBase> TypeParser()
    {
        return Choice(ArrayTypeParser(),
            from token in BasicTypeParser()
            select new TypeNode(token));
    }

    public static IParser<LexicalToken, VariableDeclarationNode> VariableDeclarationParser()
    {
        return from tokens in Satisfy<LexicalToken>(
                token => token.TokenType == LexicalTokenType.Identifier).SeparatedBy1(Delimiter(","))
            from _1 in Delimiter(":")
            from type in TypeParser()
            select new VariableDeclarationNode(tokens, type.Convert<TypeNode>());
    }

    public static IParser<LexicalToken, BlockNode> VariableDeclarationsParser()
    {
        return (from _ in Keyword("var")
            from nodes in VariableDeclarationParser().SeparatedOrEndBy1(Delimiter(";"))
            select new BlockNode(nodes)).Try(new BlockNode([]));
    }

    public static IParser<LexicalToken, IEnumerable<Parameter>> ParameterParser()
    {
        return Choice(
            from _ in Keyword("var")
            from tokens in IdentifierParser().SeparatedBy1(Delimiter(","))
            from _1 in Delimiter(":")
            from typeToken in TypeParser()
            select tokens.Select(x => new Parameter(true, x, typeToken)),
            from tokens in IdentifierParser().SeparatedBy1(Delimiter(","))
            from _ in Delimiter(":")
            from typeToken in TypeParser()
            select tokens.Select(x => new Parameter(false, x, typeToken))
        );
    }

    public static IParser<LexicalToken, IEnumerable<Parameter>> FormalParameterParser()
    {
        return (from _ in Delimiter("(")
            from parameters in ParameterParser().SeparatedBy(Delimiter(";"))
            from _1 in Delimiter(")")
            select parameters.Aggregate(new List<Parameter>(), (result, array) =>
            {
                result.AddRange(array);
                return result;
            })).Try([]);
    }

    public static IParser<LexicalToken, SubprogramHead> SubprogramHeadParser()
    {
        return Choice(
            from _ in Keyword("procedure")
            from identifier in IdentifierParser()
            from parameters in FormalParameterParser()
            select new SubprogramHead(identifier, parameters),
            from _ in Keyword("function")
            from identifier in IdentifierParser()
            from parameters in FormalParameterParser()
            from _1 in Delimiter(":")
            from typeToken in TypeParser()
            select new SubprogramHead(identifier, parameters, typeToken)
        );
    }

    public static IParser<LexicalToken, SubprogramBody> SubprogramBodyParser()
    {
        return from constant in ConstDeclarationsParser()
            from variables in VariableDeclarationsParser()
            from block in CompoundStatementParser()
            select new SubprogramBody(constant, variables, block);
    }

    public static IParser<LexicalToken, Subprogram> SubprogramParser()
    {
        return from head in SubprogramHeadParser()
            from _ in Delimiter(";")
            from body in SubprogramBodyParser()
            select new Subprogram(head, body);
    }

    public static IParser<LexicalToken, ProgramBody> ProgramBodyParser()
    {
        return from constant in ConstDeclarationsParser()
            from variables in VariableDeclarationsParser()
            from subprograms in SubprogramParser().SeparatedOrEndBy(Delimiter(";"))
                .Map(x => new BlockNode(x))
            from block in CompoundStatementParser()
            select new ProgramBody(constant, variables, subprograms, block);
    }

    public static IParser<LexicalToken, ProgramHead> ProgramHeadParser()
    {
        return from _ in Keyword("program")
            from token in Satisfy<LexicalToken>(token => token.TokenType == LexicalTokenType.Identifier)
            select new ProgramHead(token);
    }

    public static IParser<LexicalToken, Program> ProgramParser()
    {
        return from head in ProgramHeadParser()
            from _1 in Delimiter(";")
            from body in ProgramBodyParser()
            from _2 in Delimiter(".")
            select new Program(head, body);
    }
}