IMPLEMENTATION MODULE Parser;

FROM SYSTEM IMPORT TSIZE;

FROM MemUtils IMPORT MemZero;
FROM Storage IMPORT ALLOCATE, REALLOCATE;

FROM Lexer IMPORT LexerKind, LexerToken, lexer_current, lexer_lex;

(* Calls lexer_lex() but skips the comments. *)
PROCEDURE transpiler_lex(lexer: PLexer): LexerToken;
VAR
  result: LexerToken;
BEGIN
  result := lexer_lex(lexer);

  WHILE result.kind = lexerKindComment DO
    result := lexer_lex(lexer)
  END;

  RETURN result
END transpiler_lex;
PROCEDURE parse_type_fields(lexer: PLexer): PAstFieldDeclaration;
VAR
  token: LexerToken;
  field_declarations: PAstFieldDeclaration;
  field_count: CARDINAL;
  current_field: PAstFieldDeclaration;
BEGIN
  ALLOCATE(field_declarations, TSIZE(AstFieldDeclaration));
  token := transpiler_lex(lexer);
  field_count := 0;

  WHILE token.kind <> lexerKindEnd DO
    INC(field_count);
	REALLOCATE(field_declarations, TSIZE(AstFieldDeclaration) * (field_count + 1));
    current_field := field_declarations;
    INC(current_field , TSIZE(AstFieldDeclaration) * (field_count - 1));

    token := transpiler_lex(lexer);

    current_field^.field_name := token.identifierKind;

    token := transpiler_lex(lexer);
    current_field^.field_type := parse_type_expression(lexer);
    token := transpiler_lex(lexer);

    IF token.kind = lexerKindSemicolon THEN
      token := transpiler_lex(lexer)
    END
  END;
  INC(current_field, TSIZE(AstFieldDeclaration));
  MemZero(current_field, TSIZE(AstFieldDeclaration));

  RETURN field_declarations
END parse_type_fields;
PROCEDURE parse_record_type(lexer: PLexer): PAstTypeExpression;
VAR
  result: PAstTypeExpression;
BEGIN
  NEW(result);
  result^.kind := astTypeExpressionKindRecord;
  result^.fields := parse_type_fields(lexer);

  RETURN result
END parse_record_type;
PROCEDURE parse_pointer_type(lexer: PLexer): PAstTypeExpression;
VAR
  token: LexerToken;
  result: PAstTypeExpression;
BEGIN
  NEW(result);
  result^.kind := astTypeExpressionKindPointer;

  token := lexer_current(lexer);

  IF token.kind = lexerKindPointer THEN
    token := transpiler_lex(lexer)
  END;
  token := lexer_current(lexer);
  result^.target := parse_type_expression(lexer);

  RETURN result
END parse_pointer_type;
PROCEDURE parse_array_type(lexer: PLexer): PAstTypeExpression;
VAR
  token: LexerToken;
  buffer: ARRAY[1..20] OF CHAR;
  result: PAstTypeExpression;
BEGIN
  NEW(result);
  result^.kind := astTypeExpressionKindArray;
  result^.length := 0;

  token := lexer_current(lexer);

  IF token.kind = lexerKindArray THEN
    token := transpiler_lex(lexer)
  END;
  IF token.kind <> lexerKindOf THEN
    token := transpiler_lex(lexer);

    result^.length := token.integerKind;

    token := transpiler_lex(lexer);
  END;
  token := transpiler_lex(lexer);
  result^.base := parse_type_expression(lexer);

  RETURN result
END parse_array_type;
PROCEDURE parse_enumeration_type(lexer: PLexer): PAstTypeExpression;
VAR
  token: LexerToken;
  result: PAstTypeExpression;
  current_case: PIdentifier;
  case_count: CARDINAL;
BEGIN
  NEW(result);
  result^.kind := astTypeExpressionKindEnumeration;

  case_count := 1;
  ALLOCATE(result^.cases, TSIZE(Identifier) * 2);
  token := transpiler_lex(lexer);
  current_case := result^.cases;
  current_case^ := token.identifierKind;

  token := transpiler_lex(lexer);

  WHILE token.kind = lexerKindComma DO
    token := transpiler_lex(lexer);

    INC(case_count);
    REALLOCATE(result^.cases, TSIZE(Identifier) * (case_count + 1));
    current_case := result^.cases;
	INC(current_case, TSIZE(Identifier) * (case_count - 1));
	current_case^ := token.identifierKind;

    token := transpiler_lex(lexer)
  END;
  INC(current_case, TSIZE(Identifier));
  MemZero(current_case, TSIZE(Identifier));

  RETURN result
END parse_enumeration_type;
PROCEDURE parse_named_type(lexer: PLexer): PAstTypeExpression;
VAR
  token: LexerToken;
  result: PAstTypeExpression;
BEGIN
  token := lexer_current(lexer);
  NEW(result);

  result^.kind := astTypeExpressionKindNamed;
  result^.name := token.identifierKind;

  RETURN result
END parse_named_type;
PROCEDURE parse_procedure_type(lexer: PLexer): PAstTypeExpression;
VAR
  token: LexerToken;
  result: PAstTypeExpression;
  current_parameter: PPAstTypeExpression;
  parameter_count: CARDINAL;
BEGIN
  parameter_count := 0;
  NEW(result);
  result^.kind := astTypeExpressionKindProcedure;

  ALLOCATE(result^.parameters, 1);

  token := transpiler_lex(lexer);
  token := transpiler_lex(lexer);

  WHILE token.kind <> lexerKindRightParen DO
    INC(parameter_count);
    REALLOCATE(result^.parameters, TSIZE(PAstTypeExpression) * (parameter_count + 1));
    current_parameter := result^.parameters;
	INC(current_parameter, TSIZE(PAstTypeExpression) * (parameter_count - 1));

    current_parameter^ := parse_type_expression(lexer);

    token := transpiler_lex(lexer);
    IF token.kind = lexerKindComma THEN
      token := transpiler_lex(lexer)
    END
  END;
  current_parameter := result^.parameters;
  INC(current_parameter, TSIZE(PAstTypeExpression) * parameter_count);
  current_parameter^ := NIL;

  RETURN result
END parse_procedure_type;
PROCEDURE parse_type_expression(lexer: PLexer): PAstTypeExpression;
VAR
  token: LexerToken;
  result: PAstTypeExpression;
BEGIN
  result := NIL;
  token := lexer_current(lexer);

  IF token.kind = lexerKindRecord THEN
    result := parse_record_type(lexer)
  END;
  IF token.kind = lexerKindLeftParen THEN
    result := parse_enumeration_type(lexer)
  END;
  IF (token.kind = lexerKindArray) OR (token.kind = lexerKindLeftSquare) THEN
    result := parse_array_type(lexer)
  END;
  IF token.kind = lexerKindHat THEN
    result := parse_pointer_type(lexer)
  END;
  IF token.kind = lexerKindProc THEN
    result := parse_procedure_type(lexer)
  END;
  IF token.kind = lexerKindIdentifier THEN
    result := parse_named_type(lexer)
  END;
  RETURN result
END parse_type_expression;
PROCEDURE parse_type_declaration(lexer: PLexer): PAstTypeDeclaration;
VAR
  token: LexerToken;
  result: PAstTypeDeclaration;
BEGIN
  token := lexer_current(lexer);

  NEW(result);
  result^.identifier := token.identifierKind;

  token := transpiler_lex(lexer);
  token := transpiler_lex(lexer);

  result^.type_expression := parse_type_expression(lexer);
  token := transpiler_lex(lexer);

  RETURN result
END parse_type_declaration;
PROCEDURE parse_type_part(lexer: PLexer): PPAstTypeDeclaration;
VAR
  token: LexerToken;
  result: PPAstTypeDeclaration;
  current_declaration: PPAstTypeDeclaration;
  declaration_count: CARDINAL;
BEGIN
  token := lexer_current(lexer);

  ALLOCATE(result, TSIZE(PAstTypeDeclaration));
  current_declaration := result;
  declaration_count := 0;

  IF token.kind = lexerKindType THEN
    token := transpiler_lex(lexer);

    WHILE token.kind = lexerKindIdentifier DO
      INC(declaration_count);

      REALLOCATE(result, TSIZE(PAstTypeDeclaration) * (declaration_count + 1));
      current_declaration := result;
      INC(current_declaration, TSIZE(PAstTypeDeclaration) * (declaration_count - 1));

      current_declaration^ := parse_type_declaration(lexer);
      token := transpiler_lex(lexer)
    END
  END;
  IF declaration_count <> 0 THEN
    INC(current_declaration, TSIZE(PAstTypeDeclaration))
  END;
  current_declaration^ := NIL;

  RETURN result
END parse_type_part;
PROCEDURE parse_variable_declaration(lexer: PLexer): PAstVariableDeclaration;
VAR
  token: LexerToken;
  result: PAstVariableDeclaration;
BEGIN
  NEW(result);

  token := lexer_current(lexer);
  result^.variable_name := token.identifierKind;

  token := transpiler_lex(lexer);

  token := transpiler_lex(lexer);
  result^.variable_type := parse_type_expression(lexer);

  token := transpiler_lex(lexer);
  RETURN result
END parse_variable_declaration;
PROCEDURE parse_variable_part(lexer: PLexer): PPAstVariableDeclaration;
VAR
  token: LexerToken;
  result: PPAstVariableDeclaration;
  current_declaration: PPAstVariableDeclaration;
  declaration_count: CARDINAL;
BEGIN
  token := lexer_current(lexer);

  ALLOCATE(result, TSIZE(PAstVariableDeclaration));
  current_declaration := result;
  declaration_count := 0;

  IF token.kind = lexerKindVar THEN
    token := transpiler_lex(lexer);

    WHILE token.kind = lexerKindIdentifier DO
      INC(declaration_count);

      REALLOCATE(result, TSIZE(PAstVariableDeclaration) * (declaration_count + 1));
      current_declaration := result;
      INC(current_declaration, TSIZE(PAstVariableDeclaration) * (declaration_count - 1));

      current_declaration^ := parse_variable_declaration(lexer);
      token := transpiler_lex(lexer)
    END
  END;
  IF declaration_count <> 0 THEN
    INC(current_declaration, TSIZE(PAstVariableDeclaration))
  END;
  current_declaration^ := NIL;

  RETURN result
END parse_variable_part;
PROCEDURE parse_constant_declaration(lexer: PLexer): PAstConstantDeclaration;
VAR
  token: LexerToken;
  result: PAstConstantDeclaration;
BEGIN
  NEW(result);

  token := lexer_current(lexer);
  result^.constant_name := token.identifierKind;

  token := transpiler_lex(lexer);

  token := transpiler_lex(lexer);
  result^.constant_value := token.integerKind;

  token := transpiler_lex(lexer);

  RETURN result
END parse_constant_declaration;
PROCEDURE parse_constant_part(lexer: PLexer): PPAstConstantDeclaration;
VAR
  token: LexerToken;
  result: PPAstConstantDeclaration;
  current_declaration: PPAstConstantDeclaration;
  declaration_count: CARDINAL;
BEGIN
  token := lexer_current(lexer);

  ALLOCATE(result, TSIZE(PAstConstantDeclaration));
  current_declaration := result;
  declaration_count := 0;

  IF token.kind = lexerKindConst THEN
    token := transpiler_lex(lexer);

    WHILE token.kind = lexerKindIdentifier DO
      INC(declaration_count);

      REALLOCATE(result, TSIZE(PAstConstantDeclaration) * (declaration_count + 1));
      current_declaration := result;
      INC(current_declaration, TSIZE(PAstConstantDeclaration) * (declaration_count - 1));

      current_declaration^ := parse_constant_declaration(lexer);
      token := transpiler_lex(lexer)
    END
  END;
  IF declaration_count <> 0 THEN
    INC(current_declaration, TSIZE(PAstConstantDeclaration))
  END;
  current_declaration^ := NIL;

  RETURN result
END parse_constant_part;
PROCEDURE parse_import_statement(lexer: PLexer): PAstImportStatement;
VAR
  result: PAstImportStatement;
  token: LexerToken;
  symbol_count: CARDINAL;
  current_symbol: PIdentifier;
BEGIN
  NEW(result);
  symbol_count := 1;

  token := transpiler_lex(lexer);
  result^.package := token.identifierKind;

  token := transpiler_lex(lexer);
  ALLOCATE(result^.symbols, TSIZE(Identifier) * 2);

  current_symbol := result^.symbols;

  token := transpiler_lex(lexer);
  current_symbol^ := token.identifierKind;

  token := transpiler_lex(lexer);
  WHILE token.kind <> lexerKindSemicolon DO
    token := transpiler_lex(lexer);
    INC(symbol_count);

    REALLOCATE(result^.symbols, TSIZE(Identifier) * (symbol_count + 1));
    current_symbol := result^.symbols;
	INC(current_symbol, TSIZE(Identifier) * (symbol_count - 1));

    current_symbol^ := token.identifierKind;
    token := transpiler_lex(lexer)
  END;
  INC(current_symbol, TSIZE(Identifier));
  MemZero(current_symbol, TSIZE(Identifier));

  token := transpiler_lex(lexer);

  RETURN result
END parse_import_statement;
PROCEDURE parse_import_part(lexer: PLexer): PPAstImportStatement;
VAR
  token: LexerToken;
  import_statement: PPAstImportStatement;
  result: PPAstImportStatement;
  import_count: CARDINAL;
BEGIN
  token := lexer_current(lexer);
  ALLOCATE(result, TSIZE(PAstImportStatement));
  import_statement := result;
  import_count := 0;

  WHILE token.kind = lexerKindFrom DO
    INC(import_count);

    REALLOCATE(result, TSIZE(PAstImportStatement) * (import_count + 1));
    import_statement := result;
    INC(import_statement, TSIZE(PAstImportStatement) * (import_count - 1));

    import_statement^ := parse_import_statement(lexer);
    token := lexer_current(lexer)
  END;
  IF import_count > 0 THEN
    INC(import_statement, TSIZE(PAstImportStatement))
  END;
  import_statement^ := NIL;

  RETURN result
END parse_import_part;
PROCEDURE parse_literal(lexer: PLexer): PAstLiteral;
VAR
  literal: PAstLiteral;
  token: LexerToken;
BEGIN
  literal := NIL;
  token := lexer_current(lexer);

  IF token.kind = lexerKindInteger THEN
    NEW(literal);

    literal^.kind := astLiteralKindInteger;
    literal^.integer := token.integerKind;
  END;
  IF token.kind = lexerKindCharacter THEN
    NEW(literal);

    literal^.kind := astLiteralKindString;
    literal^.string := token.stringKind;
  END;
  IF token.kind = lexerKindNull THEN
    NEW(literal);

    literal^.kind := astLiteralKindNull;
  END;
  IF literal <> NIL THEN
    token := transpiler_lex(lexer)
  END;

  RETURN literal
END parse_literal;
PROCEDURE parse_factor(lexer: PLexer): PAstExpression;
VAR
  next_token: LexerToken;
  result: PAstExpression;
  literal: PAstLiteral;
BEGIN
  result := NIL;
  next_token := lexer_current(lexer);

  literal := parse_literal(lexer);

  IF (result = NIL) AND (literal <> NIL) THEN
    NEW(result);

    result^.kind := astExpressionKindLiteral;
    result^.literal := literal;
  END;
  IF (result = NIL) AND (next_token.kind = lexerKindMinus) THEN
    NEW(result);
    next_token := transpiler_lex(lexer);

    result^.kind := astExpressionKindUnary;
    result^.unary_operator := astUnaryOperatorMinus;
    result^.unary_operand := parse_factor(lexer)
  END;
  IF (result = NIL) AND (next_token.kind = lexerKindTilde) THEN
    NEW(result);
    next_token := transpiler_lex(lexer);

    result^.kind := astExpressionKindUnary;
    result^.unary_operator := astUnaryOperatorNot;
    result^.unary_operand := parse_factor(lexer)
  END;
  IF (result = NIL) AND (next_token.kind = lexerKindIdentifier) THEN
    NEW(result);
 
    result^.kind := astExpressionKindIdentifier;
    result^.identifier := next_token.identifierKind;
 
    next_token := transpiler_lex(lexer)
  END;

  RETURN result
END parse_factor;
PROCEDURE parse_designator(lexer: PLexer): PAstExpression;
VAR
  next_token: LexerToken;
  inner_expression: PAstExpression;
  designator: PAstExpression;
  handled: BOOLEAN;
BEGIN
  designator := parse_factor(lexer);
  handled := designator <> NIL;
  next_token := lexer_current(lexer);

  WHILE handled DO
    inner_expression := designator;
    handled := FALSE;

    IF ~handled AND (next_token.kind = lexerKindHat) THEN
      NEW(designator);

      designator^.kind := astExpressionKindDereference;
      designator^.reference := inner_expression;

      next_token := transpiler_lex(lexer);
      handled := TRUE
    END;
    IF ~handled AND (next_token.kind = lexerKindLeftSquare) THEN
      NEW(designator);
      next_token := transpiler_lex(lexer);

      designator^.kind := astExpressionKindArrayAccess;
      designator^.array := inner_expression;
      designator^.index := parse_designator(lexer);

      next_token := transpiler_lex(lexer);
      handled := TRUE
    END;
    IF ~handled AND (next_token.kind = lexerKindDot) THEN
      NEW(designator);
      next_token := transpiler_lex(lexer);

      designator^.kind := astExpressionKindFieldAccess;
      designator^.aggregate := inner_expression;
      designator^.field := next_token.identifierKind;

      next_token := transpiler_lex(lexer);
      handled := TRUE
    END
  END;

  RETURN designator
END parse_designator;
END Parser.