parser_impl.cpp

//##################################################################################################
//  ALib C++ Library
//
//  Copyright 2013-2025 A-Worx GmbH, Germany
//  Published under 'Boost Software License' (a free software license, see LICENSE.txt)
//##################################################################################################
#include "alib_precompile.hpp"
#if !defined(ALIB_C20_MODULES) || ((ALIB_C20_MODULES != 0) && (ALIB_C20_MODULES != 1))
#   error "Symbol ALIB_C20_MODULES has to be given to the compiler as either 0 or 1"
#endif
#if ALIB_C20_MODULES
    module;
#endif
//========================================= Global Fragment ========================================
#include "alib/expressions/expressions.prepro.hpp"
#include "ALib.Monomem.StdContainers.H"
//============================================== Module ============================================
#if ALIB_C20_MODULES
    module ALib.Expressions.Impl;
    import   ALib.Expressions;
#else
#   include "ALib.Expressions.Impl.H"
#endif
//========================================== Implementation ========================================
namespace alib {  namespace expressions { namespace detail {
 
//##################################################################################################
// Parser
//##################################################################################################
 
ParserImpl::ParserImpl( Compiler& pCompiler, MonoAllocator& allocator )
: compileTimeAllocator(allocator)
, compiler            (pCompiler)
, unaryOperators      (allocator)
, binaryOperators     (allocator) {
    // characters to be known
    syntaxTokens [u8'(']= true;
    syntaxTokens [u8')']= true;
    syntaxTokens [u8',']= true;
    operatorChars[u8'?']= true;
    operatorChars[u8':']= true;
 
    // define unary ops
    for( auto& op : compiler.UnaryOperators ) {
        ALIB_ASSERT_ERROR( !unaryOperators.Contains(op), "EXPR",
                           "Doubly defined unary operator symbol '{}'.", op )
 
        unaryOperators.EmplaceUnique(op);
        for( auto it : op )
            operatorChars[it]= true;
    }
 
    for( auto& op : compiler.AlphabeticUnaryOperatorAliases ) {
        ALIB_ASSERT_ERROR( !unaryOperators.Contains(op.first), "EXPR",
                           "Doubly defined unary operator symbol '{}'.", op.first )
 
        unaryOperators.EmplaceUnique(op.first);
        if( !isalpha( op.first.CharAtStart() ) )
            for( auto it : op.first )
                operatorChars[it]= true;
    }
 
 
    for( auto& op : compiler.BinaryOperators ) {
        ALIB_ASSERT_ERROR( !binaryOperators.Contains(op.first), "EXPR",
                           "Doubly defined binary operator symbol '{}'.", op.first )
        if( op.first == A_CHAR("[]") ) {
            syntaxTokens[u8'[']= true;
            syntaxTokens[u8']']= true;
        } else {
            binaryOperators.EmplaceUnique(op.first);
            for( auto it : op.first )
                operatorChars[it]= true;
    }   }
 
    for( auto& op : compiler.AlphabeticBinaryOperatorAliases ) {
        ALIB_ASSERT_ERROR( !binaryOperators.Contains(op.first), "EXPR",
                           "Doubly defined binary operator symbol '{}'.", op.first )
 
        ALIB_DBG( auto originalOp= )
        compiler.BinaryOperators.Find( op.second );
        ALIB_ASSERT_ERROR( originalOp != compiler.BinaryOperators.end(), "EXPR",
                           "Alias '{}' defined for unknown operator '{}'.",
                           op.first, op.second )
 
        binaryOperators.EmplaceUnique(op.first);
        if( !isalpha( op.first.CharAtStart() ) )
            for( auto it : op.first )
                operatorChars[it]= true;
}   }
 
//##################################################################################################
//  Lexer
//##################################################################################################
void ParserImpl::NextToken() {
    scanner.TrimStart();
    tokPosition= expression.Length() - scanner.Length();
 
    if( scanner.IsEmpty() ) {
        token= Tokens::EOT;
        return;
    }
 
    character first= scanner.CharAtStart<NC>();
 
  //----------------------------------------- Syntax Tokens ----------------------------------------
    if( syntaxTokens[first]  ) {
        token= Tokens(first);
        scanner.ConsumeChar();
        return;
    }
 
  //--------------------------------------- Symbolic operators -------------------------------------
  // read up to 3 operator characters
    if( operatorChars[first] ) {
        integer operatorLength= 1;
        scanner.ConsumeChar();
        if( operatorChars[scanner.CharAtStart() ] ) {
            scanner.ConsumeChar();
            ++operatorLength;
 
            if( operatorChars[scanner.CharAtStart() ] ) {
                scanner.ConsumeChar();
                ++operatorLength;
        }   }
 
        token= Tokens::SymbolicOp;
        tokString= String( expression.Buffer() + tokPosition, operatorLength );
 
        // special treatment for Elvis with spaces "? :"
        if(    tokString == A_CHAR("?") && compiler.BinaryOperators.Contains( A_CHAR("?:") )   ) {
            // patch existing token and return
            Substring backup= scanner;
            if( scanner.TrimStart().CharAtStart() == ':' ) {
                tokString= A_CHAR("?:");
                scanner.ConsumeChar();
            }
            else
                scanner= backup;
        }
        return;
    }
 
  //-------------------------------------- alphabetic operators ------------------------------------
    if( isalpha( first ) ) {
        integer len= 1;
        while( len < scanner.Length() && ( isalpha( scanner[len] ) || scanner[len] == '_' ) )
            ++len;
        tokString= scanner.Substring<NC>( 0, len );
        auto hashCode=  tokString.HashcodeIgnoreCase();
 
        // unary
        {
            decltype(unaryOperators)::Iterator it;
            if(    (it= unaryOperators .Find( tokString, hashCode )) != unaryOperators.end()
                && (    HasBits(compiler.CfgCompilation, Compilation::AlphabeticOperatorsIgnoreCase)
                     || tokString.Equals<NC>( it.Value() ) ) )
            {
                scanner.ConsumeChars<NC>( tokString.Length() );
                token= Tokens::AlphaUnOp;
                return;
        }   }
 
        // binary
        {
            decltype(binaryOperators)::Iterator it;
            if(    (it= binaryOperators .Find( tokString, hashCode )) != binaryOperators.end()
                && (    HasBits(compiler.CfgCompilation, Compilation::AlphabeticOperatorsIgnoreCase)
                     || tokString.Equals<NC>( it.Value() ) ) )
            {
                scanner.ConsumeChars<NC>( tokString.Length() );
                token= Tokens::AlphaBinOp;
                return;
        }   }
 
    }
 
  //------------------------------------------ Identifiers -----------------------------------------
    if( isalpha( first ) || first == '_' ) {
        integer endOfIdent= 0;
        character next= 0;
        while(      ++endOfIdent < scanner.Length()
                && (    isalnum( next= scanner[endOfIdent] )
                     || next == '_'                         ) );
 
        token= Tokens::Identifier;
        tokString= String( expression.Buffer() + tokPosition, endOfIdent );
        scanner.ConsumeChars<NC>( endOfIdent );
        return;
    }
 
  //-------------------------------------------- numbers -------------------------------------------
    if( isdigit( first ) ) {
        integer endOfDecPart= 0;
        character next= 0;
        while(      ++endOfDecPart < scanner.Length()
                && (   isdigit( next= scanner[endOfDecPart] )
                     || ( HasBits(numberFormat->Flags, NumberFormatFlags::ReadGroupChars) && next== numberFormat->ThousandsGroupChar ) )
             );
 
 
        // float number
        if(    next == numberFormat->DecimalPointChar
            || next == 'e'
            || next == 'E'
            || scanner.Substring( endOfDecPart ).StartsWith( numberFormat->ExponentSeparator ) )
 
        {
            auto oldStart= scanner.Buffer();
            double value;
            scanner.ConsumeFloat( value, numberFormat );
            token   = Tokens::LitFloat;
            tokFloat= value;
 
            String numberParsed( oldStart, scanner.Buffer() - oldStart );
            tokLiteralHint=        numberParsed.IndexOf('e') > 0
                                || numberParsed.IndexOf('E') > 0
                                || numberParsed.IndexOf( numberFormat->ExponentSeparator ) > 0
                            ? ASTLiteral::NFHint::Scientific
                            : ASTLiteral::NFHint::NONE;
        }
 
        // integer number
        else {
            tokLiteralHint= ASTLiteral::NFHint::NONE;
            if(         numberFormat->HexLiteralPrefix.IsNotEmpty()
                && scanner.StartsWith( numberFormat->HexLiteralPrefix ) )   tokLiteralHint= ASTLiteral::NFHint::Hexadecimal;
            else if(    numberFormat->OctLiteralPrefix.IsNotEmpty()
                && scanner.StartsWith( numberFormat->OctLiteralPrefix ) )   tokLiteralHint= ASTLiteral::NFHint::Octal;
            else if(    numberFormat->BinLiteralPrefix.IsNotEmpty()
                && scanner.StartsWith( numberFormat->BinLiteralPrefix ) )   tokLiteralHint= ASTLiteral::NFHint::Binary;
 
            integer value;
            scanner.ConsumeInt( value, numberFormat );
            token= Tokens::LitInteger;
            tokInteger= value;
        }
 
        return;
    }
 
  //-------------------------------------------- Strings -------------------------------------------
    if( first == '"' ) {
        bool lastWasSlash= false;
        scanner.ConsumeChar<NC>();
        character next;
        while( (next= scanner.ConsumeChar()) != '\0' ) {
            if( next == '\\' )                  { lastWasSlash= true;   continue;   }
            if( next == '\"' && !lastWasSlash ) break;
            lastWasSlash= false;
        }
 
        if( next != '"' ) {
            Exception e( ALIB_CALLER_NULLED, Exceptions::SyntaxErrorExpectation,
                         EXPRESSIONS.GetResource("EE4")                                   );
            e.Add      ( ALIB_CALLER_NULLED, Exceptions::ExpressionInfo,
                         expression, expression.Length() - scanner.Length() );
            throw e;
        }
 
        String quoted( expression.Buffer() + tokPosition + 1,
                       expression.Length() - scanner.Length() - tokPosition -2 );
        token    = Tokens::LitString;
        tokString.Allocate(compileTimeAllocator, String1K(quoted) << Escape( lang::Switch::Off ) );
        return;
    }
 
  //--------------------------------------- unrecognized token -------------------------------------
    Exception e( ALIB_CALLER_NULLED, Exceptions::SyntaxError );
    e.Add      ( ALIB_CALLER_NULLED, Exceptions::ExpressionInfo, expression, expression.Length() - scanner.Length() );
    throw e;
}
 
 
 
//##################################################################################################
// Parser
//##################################################################################################
#define Start               parseConditional
 
detail::AST* ParserImpl::Parse( const String& exprString, NumberFormat* nf ) {
    if( exprString.IsEmpty() )
        throw Exception( ALIB_CALLER, Exceptions::EmptyExpressionString );
 
    expression  = exprString;
    numberFormat= nf;
    ASTs        = compileTimeAllocator().New<StdVectorMA<AST*>>( compileTimeAllocator );
    ASTs->reserve(20);
 
    // load first token
    scanner=    expression;
    NextToken();
 
//ALIB_DBG( lexer.DbgListTokens(); )
 
    AST* ast= Start();
 
 
    // if tokens remain, an "operator" would be expected
    if( token != Tokens::EOT ) {
        Exception e( ALIB_CALLER_NULLED, Exceptions::SyntaxErrorExpectation, EXPRESSIONS.GetResource("EE5") );
        e.Add      ( ALIB_CALLER_NULLED, Exceptions::ExpressionInfo, expression, tokPosition );
        throw e;
    }
 
    return ast;
}
 
 
AST* ParserImpl::parseConditional() {
    // parse lhs as simple
    push( parseBinary() ); // Q
 
    integer qmPosition= tokPosition;
 
 
    if( token == Tokens::SymbolicOp && tokString == A_CHAR("?") ) {
        NextToken();
        push( Start() ); // T
 
        // expect colon
        if( token != Tokens::SymbolicOp || tokString != A_CHAR(":") ) {
            Exception e( ALIB_CALLER_NULLED, Exceptions::SyntaxErrorExpectation, EXPRESSIONS.GetResource("EE6") );
            e.Add      ( ALIB_CALLER_NULLED, Exceptions::ExpressionInfo, expression, tokPosition );
            throw e;
        }
        integer colonPosition= tokPosition;
 
        NextToken();
 
        AST* F= Start();
        AST* T= pop();
        AST* Q= pop();
        return compileTimeAllocator().New<ASTConditional>(Q, T, F, qmPosition, colonPosition );
    }
 
    // was no conditional
    return pop();
}
 
AST* ParserImpl::parseBinary() {
    // parse lhs as simple
    push( parseSimple() );
 
    // parse
    integer position= tokPosition;
    String binOp;
    for( ;; ) {
        binOp= getBinaryOp();
        if( binOp.IsNull() )
            return pop();
 
        // rhs is braced? -> lhs becomes <lhs op rhs> and we start over
        if( token == Tokens::BraceOpen ) {
            replace( compileTimeAllocator().New<ASTBinaryOp>(binOp, top(), parseSimple(), position ) );
            position= tokPosition;
            continue;
        }
        break;
    }
 
    // check if tokens remain
    if( token == Tokens::EOT ) {
        Exception e( ALIB_CALLER_NULLED, Exceptions::SyntaxErrorExpectation, EXPRESSIONS.GetResource("EE7") );
        e.Add      ( ALIB_CALLER_NULLED, Exceptions::ExpressionInfo, expression, tokPosition );
        throw e;
    }
 
    AST* lhs= top();
    AST* rhs= push( parseBinary() );
 
    int             binOpPrecedence= compiler.GetBinaryOperatorPrecedence( binOp );
    AST*            replace        = rhs;
    ASTBinaryOp*    parent         = nullptr;
    while(    replace->NodeType == AST::Types::BinaryOp
           && compiler.GetBinaryOperatorPrecedence(dynamic_cast<ASTBinaryOp*>(replace)->Operator) <= binOpPrecedence )
    {
        parent = dynamic_cast<ASTBinaryOp*>(replace);
        replace= parent->Lhs;
    }
 
    pop();
    pop();
    if( parent == nullptr )
        return compileTimeAllocator().New<ASTBinaryOp>( binOp, lhs, rhs, position );
 
    // insert binary at lhs of deepest equal-level binary found.
    // Its current lhs becomes its new lhs-child's rhs.
    parent->Lhs=  compileTimeAllocator().New<ASTBinaryOp>( binOp, lhs, parent->Lhs, position );
    return rhs;
}
 
AST* ParserImpl::parseSimple() {
    //  '('  expr  ')'   (brackets)
    if( token == Tokens::BraceOpen ) {
        NextToken();
        push( Start() );
 
        if( token != Tokens::BraceClose ) {
            Exception e( ALIB_CALLER_NULLED, Exceptions::SyntaxErrorExpectation, EXPRESSIONS.GetResource("EE1"));
            e.Add      ( ALIB_CALLER_NULLED, Exceptions::ExpressionInfo, expression, tokPosition );
            throw e;
        }
        NextToken();
        replace( parseSubscript( top() ) );
        return pop();
    }
 
    //  unary operator
    integer position= tokPosition;
    {
        String unOp= getUnaryOp();
        if( unOp.IsNotNull() ) {
            push( compileTimeAllocator().New<ASTUnaryOp>(unOp, parseSimple(), position ) );
            replace( parseSubscript( top() ) );
            return pop();
    }   }
 
    // terminals
    if( token == Tokens::LitInteger ) { push(compileTimeAllocator().New<ASTLiteral>(tokInteger, position, tokLiteralHint )             ); NextToken(); replace( parseSubscript(top()) ); return pop(); }
    if( token == Tokens::LitFloat   ) { push(compileTimeAllocator().New<ASTLiteral>(tokFloat  , position, tokLiteralHint )             ); NextToken(); replace( parseSubscript(top()) ); return pop(); }
    if( token == Tokens::LitString  ) { push(compileTimeAllocator().New<ASTLiteral>(String(compileTimeAllocator, tokString), position )); NextToken(); replace( parseSubscript(top()) ); return pop(); }
 
    // allow bin op's names here! This is tricky but right!
    if( token == Tokens::Identifier || token == Tokens::AlphaBinOp ) {
        String name= tokString;
        NextToken();
 
        // function
        if( token == Tokens::BraceOpen ) {
            ASTFunction* astFunction= compileTimeAllocator().New<ASTFunction>( name, position, compileTimeAllocator );
            push( astFunction );
            for(;;) {
                NextToken();
                if( token == Tokens::BraceClose ) {
                    NextToken();
                    return pop();
                }
                astFunction->Arguments.emplace_back( Start() );
 
                if( token == Tokens::Comma )
                    continue;
 
                if( token != Tokens::BraceClose ) {
                    Exception e( ALIB_CALLER_NULLED, Exceptions::SyntaxErrorExpectation, EXPRESSIONS.GetResource("EE2") );
                    e.Add      ( ALIB_CALLER_NULLED, Exceptions::ExpressionInfo, expression, tokPosition );
                    throw e;
                }
 
                NextToken();
                replace( parseSubscript( astFunction ) );
                return pop();
        }   }
 
        // identifier
        replace( parseSubscript( push(compileTimeAllocator().New<ASTIdentifier>( String(compileTimeAllocator, name), position ) ) ) );
        return pop();
    }
 
  //--------------------------------------------- ERRORS -------------------------------------------
    if( token == Tokens::EOT ) {
        Exception e( ALIB_CALLER_NULLED, Exceptions::SyntaxErrorExpectation, EXPRESSIONS.GetResource("EE20") );
        e.Add      ( ALIB_CALLER_NULLED, Exceptions::ExpressionInfo, expression, tokPosition );
        throw e;
    }
 
    if( token == Tokens::BraceClose ) {
        Exception e( ALIB_CALLER_NULLED, Exceptions::SyntaxErrorExpectation, EXPRESSIONS.GetResource("EE21") );
        e.Add      ( ALIB_CALLER_NULLED, Exceptions::ExpressionInfo, expression, tokPosition );
        throw e;
    }
 
    if( token == Tokens::SubscriptOpen || token == Tokens::SubscriptClose ) {
        Exception e( ALIB_CALLER_NULLED, Exceptions::SyntaxErrorExpectation, EXPRESSIONS.GetResource("EE22") );
        e.Add      ( ALIB_CALLER_NULLED, Exceptions::ExpressionInfo, expression, tokPosition );
        throw e;
    }
 
    if( token == Tokens::Comma ) {
        Exception e( ALIB_CALLER_NULLED, Exceptions::SyntaxErrorExpectation, EXPRESSIONS.GetResource("EE23") );
        e.Add      ( ALIB_CALLER_NULLED, Exceptions::ExpressionInfo, expression, tokPosition );
        throw e;
    }
 
    ALIB_ERROR( "EXPR", "Internal error. This should never happen." )
    return nullptr;
}
 
AST* ParserImpl::parseSubscript( AST *function ) {
    if(    !HasBits( compiler.CfgCompilation, Compilation::AllowSubscriptOperator )
        || token != Tokens::SubscriptOpen )
        return function;
 
    integer position= tokPosition;
 
    NextToken();
 
    push( Start() );
 
    if( token != Tokens::SubscriptClose ) {
        Exception e( ALIB_CALLER_NULLED, Exceptions::SyntaxErrorExpectation, EXPRESSIONS.GetResource("EE3") );
        e.Add      ( ALIB_CALLER_NULLED, Exceptions::ExpressionInfo, expression, tokPosition );
        throw e;
    }
 
    // success
    NextToken();
    return compileTimeAllocator().New<ASTBinaryOp>( A_CHAR("[]"), function, pop(), position );
}
 
 
//##################################################################################################
// Helpers
//##################################################################################################
 
 
String ParserImpl::getUnaryOp() {
    if( token == Tokens::SymbolicOp ) {
        // symbolic unary ops may be nested. Hence, we find one by one from the actual token and consume the
        // token only if all is consumed.
        for( integer partialRead= 1 ; partialRead <= tokString.Length()    ; ++partialRead ) {
            Substring key= Substring( tokString.Buffer(), partialRead );
            if( unaryOperators.Contains( key ) ) {
                if( partialRead == tokString.Length() )
                    NextToken();
                else {
                    tokString= String( tokString.Buffer() + partialRead,
                                       tokString.Length() - partialRead );
                    tokPosition+= partialRead;
                }
                return key;
        }   }
        Exception e( ALIB_CALLER_NULLED, Exceptions::UnknownUnaryOperatorSymbol, tokString );
        e.Add      ( ALIB_CALLER_NULLED, Exceptions::ExpressionInfo, expression, tokPosition );
        throw e;
    }
    else if ( token == Tokens::AlphaUnOp ) {
        String alphabeticOperator= tokString;
        NextToken();
        return alphabeticOperator;
    }
 
    return NULL_STRING;
}
 
String ParserImpl::getBinaryOp() {
    if ( token == Tokens::SymbolicOp ) {
        // ignore ternary
        if ( tokString == A_CHAR( "?" ) || tokString == A_CHAR( ":" ) )
            return NULL_STRING;
 
        // binary ops may be longer and concatenated with unaries. So we consume as much as possible
        // but are happy with less than available
        for ( integer partialRead = tokString.Length(); partialRead > 0; --partialRead ) {
            Substring key = Substring( tokString.Buffer(), partialRead );
            if ( binaryOperators.Contains( key ) ) {
                if ( partialRead == tokString.Length() )
                    NextToken();
                else {
                    tokString = String( tokString.Buffer() + partialRead,
                                        tokString.Length() - partialRead );
                    tokPosition += partialRead;
                }
                return key;
        }   }
 
        Exception e( ALIB_CALLER_NULLED, Exceptions::UnknownBinaryOperatorSymbol, tokString );
        e.Add( ALIB_CALLER_NULLED, Exceptions::ExpressionInfo, expression, tokPosition );
        throw e;
    }
    else if ( token == Tokens::AlphaBinOp ) {
        String alphabeticOperator= tokString;
        NextToken();
        return alphabeticOperator;
    }
 
    return NULL_STRING;
}
 
 
#undef Start
 
}}} // namespace [alib::expressions::detail]