DEFINITION MODULE Parser;

FROM Common IMPORT Identifier, PIdentifier, ShortString;
FROM Lexer IMPORT PLexer;

TYPE
  AstLiteralKind = (
    astLiteralKindInteger,
    astLiteralKindString,
    astLiteralKindNull
  );
  AstLiteral = RECORD
    CASE kind: AstLiteralKind OF
      astLiteralKindInteger: integer: INTEGER |
      astLiteralKindString: string: ShortString |
      astLiteralKindNull:
    END
  END;
  PAstLiteral = POINTER TO AstLiteral;

  AstUnaryOperator = (
    astUnaryOperatorNot,
    astUnaryOperatorMinus
  );

  AstExpressionKind = (
    astExpressionKindLiteral,
    astExpressionKindIdentifier,
    astExpressionKindArrayAccess,
    astExpressionKindDereference,
    astExpressionKindFieldAccess,
    astExpressionKindUnary
  );
  AstExpression = RECORD 
    CASE kind: AstExpressionKind OF
      astExpressionKindLiteral: literal: PAstLiteral |
      astExpressionKindIdentifier: identifier: Identifier |
      astExpressionKindDereference: reference: PAstExpression |
      astExpressionKindArrayAccess:
        array: PAstExpression;
        index: PAstExpression |
      astExpressionKindFieldAccess:
        aggregate: PAstExpression;
        field: Identifier |
      astExpressionKindUnary:
        unary_operator: AstUnaryOperator;
        unary_operand: PAstExpression
    END
  END;
  PAstExpression = POINTER TO AstExpression;
  PPAstExpression = POINTER TO PAstExpression;

  AstImportStatement = RECORD
    package: Identifier;
    symbols: PIdentifier
  END;
  PAstImportStatement = POINTER TO AstImportStatement;
  PPAstImportStatement = POINTER TO PAstImportStatement;

  AstConstantDeclaration = RECORD
    constant_name: Identifier;
    constant_value: INTEGER
  END;
  PAstConstantDeclaration = POINTER TO AstConstantDeclaration;
  PPAstConstantDeclaration = POINTER TO PAstConstantDeclaration;

  AstFieldDeclaration = RECORD
    field_name: Identifier;
    field_type: PAstTypeExpression
  END;
  PAstFieldDeclaration = POINTER TO AstFieldDeclaration;

  AstTypeExpressionKind = (
    astTypeExpressionKindNamed,
    astTypeExpressionKindRecord,
    astTypeExpressionKindEnumeration,
    astTypeExpressionKindArray,
    astTypeExpressionKindPointer,
    astTypeExpressionKindProcedure
  );
  AstTypeExpression = RECORD
    CASE kind: AstTypeExpressionKind OF
      astTypeExpressionKindNamed: name: Identifier |
      astTypeExpressionKindEnumeration: cases: PIdentifier |
      astTypeExpressionKindPointer: target: PAstTypeExpression |
      astTypeExpressionKindRecord: fields: PAstFieldDeclaration |
      astTypeExpressionKindArray:
        base: PAstTypeExpression;
        length: CARDINAL |
      astTypeExpressionKindProcedure: parameters: PPAstTypeExpression
    END
  END;
  PAstTypeExpression = POINTER TO AstTypeExpression;
  PPAstTypeExpression = POINTER TO PAstTypeExpression;

  AstTypeDeclaration = RECORD
    identifier: Identifier;
    type_expression: PAstTypeExpression
  END;
  PAstTypeDeclaration = POINTER TO AstTypeDeclaration;
  PPAstTypeDeclaration = POINTER TO PAstTypeDeclaration;

  AstVariableDeclaration = RECORD
    variable_name: Identifier;
    variable_type: PAstTypeExpression
  END;
  PAstVariableDeclaration = POINTER TO AstVariableDeclaration;
  PPAstVariableDeclaration = POINTER TO PAstVariableDeclaration;

  AstModule = RECORD
    imports: PPAstImportStatement;
    constants: PPAstConstantDeclaration;
    types: PPAstTypeDeclaration;
    variables: PPAstVariableDeclaration
  END;
  PAstModule = POINTER TO AstModule;

PROCEDURE parse_type_expression(lexer: PLexer): PAstTypeExpression;
PROCEDURE parse_type_part(lexer: PLexer): PPAstTypeDeclaration;
PROCEDURE parse_variable_part(lexer: PLexer): PPAstVariableDeclaration;
PROCEDURE parse_constant_part(lexer: PLexer): PPAstConstantDeclaration;
PROCEDURE parse_import_part(lexer: PLexer): PPAstImportStatement;
PROCEDURE parse_designator(lexer: PLexer): PAstExpression;

END Parser.