IMPLEMENTATION MODULE Transpiler;

FROM FIO IMPORT WriteNBytes, WriteLine, WriteChar, WriteString;
FROM SYSTEM IMPORT ADR, ADDRESS, TSIZE;

FROM NumberIO IMPORT IntToStr;
FROM Storage IMPORT ALLOCATE, REALLOCATE;
FROM MemUtils IMPORT MemCopy, MemZero;

FROM Common IMPORT Identifier, PIdentifier, ShortString;
FROM Lexer IMPORT Lexer, LexerToken, lexer_current, lexer_lex, LexerKind;
FROM Parser IMPORT AstModule, PAstModule, AstTypeExpressionKind,
  AstConstantDeclaration, PPAstConstantDeclaration,
  AstTypeDeclaration, PAstTypeDeclaration, PPAstTypeDeclaration,
  PAstVariableDeclaration, PPAstVariableDeclaration,
  PAstTypeExpression, PPAstTypeExpression, AstFieldDeclaration, PAstFieldDeclaration,
  parse_type_expression, parse_variable_part, parse_type_part;

(* 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;
(* Write a semicolon followed by a newline. *)
PROCEDURE write_semicolon(output: File);
BEGIN
  WriteChar(output, ';');
  WriteLine(output)
END write_semicolon;
PROCEDURE write_current(lexer: PLexer; output: File);
VAR
  written_bytes: CARDINAL;
BEGIN
  written_bytes := WriteNBytes(output, ADDRESS(lexer^.Current - lexer^.Start), lexer^.Start)
END write_current;
PROCEDURE transpile_import(context: PTranspilerContext);
VAR
  token: LexerToken;
BEGIN
  WriteString(context^.output, 'FROM ');
  token := transpiler_lex(context^.lexer);

  write_current(context^.lexer, context^.output);
  token := transpiler_lex(context^.lexer);
  WriteString(context^.output, ' IMPORT ');

  token := transpiler_lex(context^.lexer);
  write_current(context^.lexer, context^.output);

  token := transpiler_lex(context^.lexer);
  WHILE token.kind <> lexerKindSemicolon DO
    WriteString(context^.output, ', ');
    token := transpiler_lex(context^.lexer);
    write_current(context^.lexer, context^.output);
    token := transpiler_lex(context^.lexer)
  END;
  write_semicolon(context^.output);
  token := transpiler_lex(context^.lexer)
END transpile_import;
PROCEDURE transpile_import_part(context: PTranspilerContext);
VAR
  token: LexerToken;
BEGIN
  token := lexer_current(context^.lexer);

  WHILE token.kind = lexerKindFrom DO
    transpile_import(context);
    token := lexer_current(context^.lexer)
  END;
  WriteLine(context^.output)
END transpile_import_part;
PROCEDURE transpile_constant(context: PTranspilerContext);
VAR
  token: LexerToken;
BEGIN
  WriteString(context^.output, '  ');
  token := lexer_current(context^.lexer);
  write_current(context^.lexer, context^.output);

  token := transpiler_lex(context^.lexer);
  WriteString(context^.output, ' = ');

  token := transpiler_lex(context^.lexer);
  write_current(context^.lexer, context^.output);

  token := transpiler_lex(context^.lexer);
  write_semicolon(context^.output)
END transpile_constant;
PROCEDURE transpile_constant_part(context: PTranspilerContext): PPAstConstantDeclaration;
VAR
  token: LexerToken;
BEGIN
  token := lexer_current(context^.lexer);

  IF token.kind = lexerKindConst THEN
    WriteString(context^.output, 'CONST');
    WriteLine(context^.output);
    token := transpiler_lex(context^.lexer);

    WHILE token.kind = lexerKindIdentifier DO
      transpile_constant(context);
      token := transpiler_lex(context^.lexer)
    END
  END;
  RETURN NIL
END transpile_constant_part;
PROCEDURE transpile_module(context: PTranspilerContext): PAstModule;
VAR
  token: LexerToken;
  result: PAstModule;
BEGIN
  ALLOCATE(result, TSIZE(AstModule));
  token := transpiler_lex(context^.lexer);

  IF token.kind = lexerKindDefinition THEN
    WriteString(context^.output, 'DEFINITION ');
    token := transpiler_lex(context^.lexer)
  END;
  IF token.kind = lexerKindImplementation THEN
    WriteString(context^.output, 'IMPLEMENTATION ');
    token := transpiler_lex(context^.lexer)
  END;
  WriteString(context^.output, 'MODULE ');

  (* Write the module name and end the line with a semicolon and newline. *)
  IF token.kind <> lexerKindProgram THEN
    token := transpiler_lex(context^.lexer);
  END;
  transpile_module_name(context);

  token := transpiler_lex(context^.lexer);
  write_semicolon(context^.output);
  WriteLine(context^.output);

  (* Write the module body. *)
  token := transpiler_lex(context^.lexer);
  transpile_import_part(context);

  result^.constants := transpile_constant_part(context);
  result^.types := parse_type_part(context^.lexer);
  transpile_type_part(context, result^.types);

  result^.variables := parse_variable_part(context^.lexer);
  transpile_variable_part(context, result^.variables);

  transpile_procedure_part(context);
  transpile_statement_part(context);

  WriteString(context^.output, 'END ');
  transpile_module_name(context);

  token := transpiler_lex(context^.lexer);
  WriteChar(context^.output, '.');

  token := transpiler_lex(context^.lexer);
  WriteLine(context^.output);

  RETURN result
END transpile_module;
PROCEDURE transpile_type_fields(context: PTranspilerContext; fields: PAstFieldDeclaration);
VAR
  written_bytes: CARDINAL;
  current_field: PAstFieldDeclaration;
BEGIN
  current_field := fields;

  WHILE ORD(current_field^.field_name[1]) <> 0 DO
    WriteString(context^.output, '    ');
    written_bytes := WriteNBytes(context^.output, ORD(current_field^.field_name[1]), ADR(current_field^.field_name[2]));

    WriteString(context^.output, ': ');
    transpile_type_expression(context, current_field^.field_type);

    INC(current_field , TSIZE(AstFieldDeclaration));

    IF ORD(current_field^.field_name[1]) <> 0 THEN
      WriteChar(context^.output, ';')
    END;
    WriteLine(context^.output)
  END
END transpile_type_fields;
PROCEDURE transpile_record_type(context: PTranspilerContext; type_expression: PAstTypeExpression);
BEGIN
  WriteString(context^.output, 'RECORD');
  WriteLine(context^.output);
  transpile_type_fields(context, type_expression^.fields);
  WriteString(context^.output, '  END')
END transpile_record_type;
PROCEDURE transpile_pointer_type(context: PTranspilerContext; type_expression: PAstTypeExpression);
VAR
  token: LexerToken;
BEGIN
  WriteString(context^.output, 'POINTER TO ');

  transpile_type_expression(context, type_expression^.target)
END transpile_pointer_type;
PROCEDURE transpile_array_type(context: PTranspilerContext; type_expression: PAstTypeExpression);
VAR
  buffer: ARRAY[1..20] OF CHAR;
BEGIN
  WriteString(context^.output, 'ARRAY');

  IF type_expression^.length <> 0 THEN
    WriteString(context^.output, '[1..');

    IntToStr(type_expression^.length, 0, buffer);
	WriteString(context^.output, buffer);

    WriteChar(context^.output, ']')
  END;
  WriteString(context^.output, ' OF ');

  transpile_type_expression(context, type_expression^.base)
END transpile_array_type;
PROCEDURE transpile_enumeration_type(context: PTranspilerContext; type_expression: PAstTypeExpression);
VAR
  current_case: PIdentifier;
  written_bytes: CARDINAL;
BEGIN
  current_case := type_expression^.cases;

  WriteString(context^.output, '(');
  WriteLine(context^.output);
  WriteString(context^.output, '    ');
  written_bytes := WriteNBytes(context^.output, ORD(current_case^[1]), ADR(current_case^[2]));
  INC(current_case, TSIZE(Identifier));

  WHILE ORD(current_case^[1]) <> 0 DO
    WriteChar(context^.output, ',');
    WriteLine(context^.output);
    WriteString(context^.output, '    ');
    written_bytes := WriteNBytes(context^.output, ORD(current_case^[1]), ADR(current_case^[2]));

    INC(current_case, TSIZE(Identifier))
  END;
  WriteLine(context^.output);
  WriteString(context^.output, '  )')
END transpile_enumeration_type;
PROCEDURE transpile_named_type(context: PTranspilerContext; type_expression: PAstTypeExpression);
VAR
  written_bytes: CARDINAL;
BEGIN
  written_bytes := WriteNBytes(context^.output, ORD(type_expression^.name[1]), ADR(type_expression^.name[2]))
END transpile_named_type;
PROCEDURE transpile_procedure_type(context: PTranspilerContext; type_expression: PAstTypeExpression);
VAR
  result: PAstTypeExpression;
  current_parameter: PPAstTypeExpression;
  parameter_count: CARDINAL;
BEGIN
  WriteString(context^.output, 'PROCEDURE(');
  current_parameter := type_expression^.parameters;

  WHILE current_parameter^ <> NIL DO
    transpile_type_expression(context, current_parameter^);

	INC(current_parameter, TSIZE(PAstTypeExpression));

    IF current_parameter^ <> NIL THEN
      WriteString(context^.output, ', ')
    END
  END;
  WriteChar(context^.output, ')')
END transpile_procedure_type;
PROCEDURE transpile_type_expression(context: PTranspilerContext; type_expression: PAstTypeExpression);
BEGIN
  IF type_expression^.kind = astTypeExpressionKindRecord THEN
    transpile_record_type(context, type_expression)
  END;
  IF type_expression^.kind = astTypeExpressionKindEnumeration THEN
    transpile_enumeration_type(context, type_expression)
  END;
  IF type_expression^.kind = astTypeExpressionKindArray THEN
    transpile_array_type(context, type_expression)
  END;
  IF type_expression^.kind = astTypeExpressionKindPointer THEN
    transpile_pointer_type(context, type_expression)
  END;
  IF type_expression^.kind = astTypeExpressionKindProcedure THEN
    transpile_procedure_type(context, type_expression)
  END;
  IF type_expression^.kind = astTypeExpressionKindNamed THEN
    transpile_named_type(context, type_expression)
  END
END transpile_type_expression;
PROCEDURE transpile_type_declaration(context: PTranspilerContext; declaration: PAstTypeDeclaration);
VAR
  written_bytes: CARDINAL;
BEGIN
  WriteString(context^.output, '  ');

  written_bytes := WriteNBytes(context^.output, ORD(declaration^.identifier[1]), ADR(declaration^.identifier[2]));
  WriteString(context^.output, ' = ');

  transpile_type_expression(context, declaration^.type_expression);
  write_semicolon(context^.output)
END transpile_type_declaration;
PROCEDURE transpile_type_part(context: PTranspilerContext; declarations: PPAstTypeDeclaration);
VAR
  current_declaration: PPAstTypeDeclaration;
BEGIN
  IF declarations^ <> NIL THEN
    WriteString(context^.output, 'TYPE');
    WriteLine(context^.output);

    current_declaration := declarations;
    WHILE current_declaration^ <> NIL DO
      transpile_type_declaration(context, current_declaration^);

      INC(current_declaration, TSIZE(PAstTypeDeclaration))
    END;
    WriteLine(context^.output)
  END
END transpile_type_part;
PROCEDURE transpile_variable_declaration(context: PTranspilerContext; declaration: PAstVariableDeclaration);
VAR
  written_bytes: CARDINAL;
BEGIN
  WriteString(context^.output, '  ');
  written_bytes := WriteNBytes(context^.output, ORD(declaration^.variable_name[1]), ADR(declaration^.variable_name[2]));

  WriteString(context^.output, ': ');

  transpile_type_expression(context, declaration^.variable_type);
  write_semicolon(context^.output)
END transpile_variable_declaration;
PROCEDURE transpile_variable_part(context: PTranspilerContext; declarations: PPAstVariableDeclaration);
VAR
  current_declaration: PPAstVariableDeclaration;
BEGIN
  IF declarations^ <> NIL THEN
    WriteString(context^.output, 'VAR');
    WriteLine(context^.output);

    current_declaration := declarations;
    WHILE current_declaration^ <> NIL DO
      transpile_variable_declaration(context, current_declaration^);

      INC(current_declaration, TSIZE(PAstVariableDeclaration))
    END;
    WriteLine(context^.output)
  END
END transpile_variable_part;
PROCEDURE transpile_procedure_heading(context: PTranspilerContext): LexerToken;
VAR
  token: LexerToken;
  result: LexerToken;
  type_expression: PAstTypeExpression;
BEGIN
  WriteString(context^.output, 'PROCEDURE ');

  result := transpiler_lex(context^.lexer);
  write_current(context^.lexer, context^.output);

  token := transpiler_lex(context^.lexer);
  WriteChar(context^.output, '(');

  token := transpiler_lex(context^.lexer);
  WHILE token.kind <> lexerKindRightParen DO
    write_current(context^.lexer, context^.output);

    token := transpiler_lex(context^.lexer);
    WriteString(context^.output, ': ');
    token := transpiler_lex(context^.lexer);

    type_expression := parse_type_expression(context^.lexer);
	transpile_type_expression(context, type_expression);

    token := transpiler_lex(context^.lexer);
    IF (token.kind = lexerKindSemicolon) OR (token.kind = lexerKindComma) THEN
      WriteString(context^.output, '; ');
      token := transpiler_lex(context^.lexer)
    END
  END;
  WriteString(context^.output, ')');
  token := transpiler_lex(context^.lexer);

  (* Check for the return type and write it. *)
  IF token.kind = lexerKindArrow THEN
    WriteString(context^.output, ': ');
    token := transpiler_lex(context^.lexer);
    write_current(context^.lexer, context^.output);
    token := transpiler_lex(context^.lexer)
  END;
  token := transpiler_lex(context^.lexer);
  write_semicolon(context^.output);

  RETURN result
END transpile_procedure_heading;
PROCEDURE transpile_expression(context: PTranspilerContext; trailing_token: LexerKind);
VAR
  token: LexerToken;
  written_bytes: CARDINAL;
BEGIN
  token := transpiler_lex(context^.lexer);

  WHILE (token.kind <> trailing_token) AND (token.kind <> lexerKindEnd) DO
    written_bytes := 0;
    IF token.kind = lexerKindNull THEN
      WriteString(context^.output, 'NIL ');
      written_bytes := 1
    END;
    IF (token.kind = lexerKindBoolean) AND token.booleanKind THEN
      WriteString(context^.output, 'TRUE ');
      written_bytes := 1
    END;
    IF (token.kind = lexerKindBoolean) AND (~token.booleanKind) THEN
      WriteString(context^.output, 'FALSE ');
      written_bytes := 1
    END;
    IF token.kind = lexerKindOr THEN
      WriteString(context^.output, 'OR ');
      written_bytes := 1
    END;
    IF token.kind = lexerKindAnd THEN
      WriteString(context^.output, 'AND ');
      written_bytes := 1
    END;
    IF token.kind = lexerKindNot THEN
      WriteString(context^.output, 'NOT ');
      written_bytes := 1
    END;
    IF written_bytes = 0 THEN
      write_current(context^.lexer, context^.output);
      WriteChar(context^.output, ' ')
    END;
    token := transpiler_lex(context^.lexer)
  END
END transpile_expression;
PROCEDURE transpile_if_statement(context: PTranspilerContext);
VAR
  token: LexerToken;
BEGIN
  WriteString(context^.output, '  IF ');
  transpile_expression(context, lexerKindThen);

  WriteString(context^.output, 'THEN');
  WriteLine(context^.output);
  transpile_statements(context);
  WriteString(context^.output, '  END');
  token := transpiler_lex(context^.lexer)
END transpile_if_statement;
PROCEDURE transpile_while_statement(context: PTranspilerContext);
VAR
  token: LexerToken;
BEGIN
  WriteString(context^.output, '  WHILE ');
  transpile_expression(context, lexerKindDo);

  WriteString(context^.output, 'DO');
  WriteLine(context^.output);
  transpile_statements(context);
  WriteString(context^.output, '  END');
  token := transpiler_lex(context^.lexer)
END transpile_while_statement;
PROCEDURE transpile_assignment_statement(context: PTranspilerContext);
BEGIN
  WriteString(context^.output, ' := ');
  transpile_expression(context, lexerKindSemicolon);
END transpile_assignment_statement;
PROCEDURE transpile_call_statement(context: PTranspilerContext);
VAR
  token: LexerToken;
BEGIN
  WriteString(context^.output, '(');
  token := transpiler_lex(context^.lexer);

  WHILE (token.kind <> lexerKindSemicolon) AND (token.kind <> lexerKindEnd) DO
    write_current(context^.lexer, context^.output);
    token := transpiler_lex(context^.lexer)
  END
END transpile_call_statement;
PROCEDURE transpile_designator_expression(context: PTranspilerContext);
VAR
  token: LexerToken;
BEGIN
  WriteString(context^.output, '  ');
  write_current(context^.lexer, context^.output);
  token := transpiler_lex(context^.lexer);

  WHILE token.kind = lexerKindLeftSquare DO
    WriteChar(context^.output, '[');
    token := transpiler_lex(context^.lexer);
    WHILE token.kind <> lexerKindRightSquare DO
      write_current(context^.lexer, context^.output);
      token := transpiler_lex(context^.lexer)
    END;
    WriteChar(context^.output, ']');
    token := transpiler_lex(context^.lexer)
  END;
  IF token.kind = lexerKindHat THEN
    WriteChar(context^.output, '^');
    token := transpiler_lex(context^.lexer)
  END;
  IF token.kind = lexerKindDot THEN
    WriteChar(context^.output, '.');
    token := transpiler_lex(context^.lexer);
    write_current(context^.lexer, context^.output);
    token := transpiler_lex(context^.lexer)
  END;
  IF token.kind = lexerKindHat THEN
    WriteChar(context^.output, '^');
    token := transpiler_lex(context^.lexer)
  END;
  WHILE token.kind = lexerKindLeftSquare DO
    WriteChar(context^.output, '[');
    token := transpiler_lex(context^.lexer);
    WHILE token.kind <> lexerKindRightSquare DO
      write_current(context^.lexer, context^.output);
      token := transpiler_lex(context^.lexer)
    END;
    WriteChar(context^.output, ']');
    token := transpiler_lex(context^.lexer)
  END
END transpile_designator_expression;
PROCEDURE transpile_return_statement(context: PTranspilerContext);
VAR
  token: LexerToken;
BEGIN
  WriteString(context^.output, '  RETURN ');
  transpile_expression(context, lexerKindSemicolon)
END transpile_return_statement;
PROCEDURE transpile_statement(context: PTranspilerContext);
VAR
  token: LexerToken;
BEGIN
  token := transpiler_lex(context^.lexer);

  IF token.kind = lexerKindIf THEN
    transpile_if_statement(context)
  END;
  IF token.kind = lexerKindWhile THEN
    transpile_while_statement(context)
  END;
  IF token.kind = lexerKindReturn THEN
    transpile_return_statement(context)
  END;
  IF token.kind = lexerKindIdentifier THEN
    transpile_designator_expression(context);
    token := lexer_current(context^.lexer);

    IF token.kind = lexerKindAssignment THEN
      transpile_assignment_statement(context)
    END;
    IF token.kind = lexerKindLeftParen THEN
      transpile_call_statement(context)
    END
  END
END transpile_statement;
PROCEDURE transpile_statements(context: PTranspilerContext);
VAR
  token: LexerToken;
BEGIN
  token := lexer_current(context^.lexer);

  WHILE token.kind <> lexerKindEnd DO
    transpile_statement(context);
    token := lexer_current(context^.lexer);

    IF token.kind = lexerKindSemicolon THEN
      WriteChar(context^.output, ';')
    END;
    WriteLine(context^.output)
  END
END transpile_statements;
PROCEDURE transpile_statement_part(context: PTranspilerContext);
VAR
  token: LexerToken;
BEGIN
  token := lexer_current(context^.lexer);
  IF token.kind = lexerKindBegin THEN
    WriteString(context^.output, 'BEGIN');
    WriteLine(context^.output);
    transpile_statements(context)
  END
END transpile_statement_part;
PROCEDURE transpile_procedure_declaration(context: PTranspilerContext);
VAR
  token: LexerToken;
  seen_variables: PPAstVariableDeclaration;
  written_bytes: CARDINAL;
  seen_constants: PPAstConstantDeclaration;
BEGIN
  token := transpile_procedure_heading(context);
  seen_constants := transpile_constant_part(context);

  seen_variables := parse_variable_part(context^.lexer);
  transpile_variable_part(context, seen_variables);
  transpile_statement_part(context);

  WriteString(context^.output, 'END ');
  written_bytes := WriteNBytes(context^.output, ORD(token.identifierKind[1]), ADR(token.identifierKind[2]));

  token := transpiler_lex(context^.lexer);
  write_semicolon(context^.output);
  token := transpiler_lex(context^.lexer)
END transpile_procedure_declaration;
PROCEDURE transpile_procedure_part(context: PTranspilerContext);
VAR
  token: LexerToken;
BEGIN
  token := lexer_current(context^.lexer);

  WHILE token.kind = lexerKindProc DO
    transpile_procedure_declaration(context);
    token := lexer_current(context^.lexer);
    WriteLine(context^.output)
  END
END transpile_procedure_part;
PROCEDURE transpile_module_name(context: PTranspilerContext);
VAR
  counter: CARDINAL;
  last_slash: CARDINAL;
BEGIN
  counter := 1;
  last_slash := 0;

  WHILE (context^.input_name[counter] <> '.') AND (ORD(context^.input_name[counter]) <> 0) DO
    IF context^.input_name[counter] = '/' THEN
      last_slash := counter
    END;
	INC(counter)
  END;

  IF last_slash = 0 THEN
    counter := 1;
  END;
  IF last_slash <> 0 THEN
    counter := last_slash + 1;
  END;
  WHILE (context^.input_name[counter] <> '.') AND (ORD(context^.input_name[counter]) <> 0) DO
    WriteChar(context^.output, context^.input_name[counter]);
	INC(counter)
  END;
END transpile_module_name;
PROCEDURE transpile(lexer: PLexer; output: File; input_name: ShortString);
VAR
  token: LexerToken;
  context: TranspilerContext;
  ast_module: PAstModule;
BEGIN
  context.input_name := input_name;
  context.output := output;
  context.lexer := lexer;

  ast_module := transpile_module(ADR(context))
END transpile;
END Transpiler.