IMPLEMENTATION MODULE Transpiler;

FROM FIO IMPORT WriteNBytes, StdOut;
FROM SYSTEM IMPORT ADR, ADDRESS;

FROM Terminal IMPORT Write, WriteLn, WriteString;
FROM Lexer IMPORT Lexer, LexerToken, LexerCurrent, LexerLex, LexerKind;

TYPE
  TranspilerContext = RECORD
  END;
  PTranspilerContext = POINTER TO TranspilerContext;

(* Calls LexerLex() but skips the comments. *)
PROCEDURE TranspilerLex(ALexer: PLexer): LexerToken;
VAR
  Result: LexerToken;
BEGIN
  Result := LexerLex(ALexer);

  WHILE Result.Kind = lexerKindComment DO
    Result := LexerLex(ALexer)
  END;

  RETURN Result
END TranspilerLex;

(* Write a semicolon followed by a newline. *)
PROCEDURE WriteSemicolon();
BEGIN
  WriteString(';');
  WriteLn()
END WriteSemicolon;

PROCEDURE TranspileImport(AContext: PTranspilerContext; ALexer: PLexer);
VAR
  Token: LexerToken;
  WrittenBytes: CARDINAL;
BEGIN
  WriteString('FROM ');
  Token := TranspilerLex(ALexer);

  WrittenBytes := WriteNBytes(StdOut, ADDRESS(ALexer^.Current - ALexer^.Start), ALexer^.Start);

  Token := TranspilerLex(ALexer);
  WriteString(' IMPORT ');

  Token := TranspilerLex(ALexer);
  WrittenBytes := WriteNBytes(StdOut, ADDRESS(ALexer^.Current - ALexer^.Start), ALexer^.Start);

  Token := TranspilerLex(ALexer);
  WHILE Token.Kind <> lexerKindSemicolon DO
    WriteString(', ');
    Token := TranspilerLex(ALexer);
    WrittenBytes := WriteNBytes(StdOut, ADDRESS(ALexer^.Current - ALexer^.Start), ALexer^.Start);
    Token := TranspilerLex(ALexer)
  END;
  WriteSemicolon();
  Token := TranspilerLex(ALexer)
END TranspileImport;

PROCEDURE TranspileImportPart(AContext: PTranspilerContext; ALexer: PLexer);
VAR
  Token: LexerToken;
BEGIN
  Token := LexerCurrent(ALexer);

  WHILE Token.Kind = lexerKindFrom DO
    TranspileImport(AContext, ALexer);
    Token := LexerCurrent(ALexer)
  END;
  WriteLn()
END TranspileImportPart;

PROCEDURE TranspileConstant(AContext: PTranspilerContext; ALexer: PLexer);
VAR
  Token: LexerToken;
  WrittenBytes: CARDINAL;
BEGIN
  WriteString('  ');
  Token := LexerCurrent(ALexer);
  WrittenBytes := WriteNBytes(StdOut, ADDRESS(ALexer^.Current - ALexer^.Start), ALexer^.Start);

  Token := TranspilerLex(ALexer);
  WriteString(' = ');

  Token := TranspilerLex(ALexer);
  WrittenBytes := WriteNBytes(StdOut, ADDRESS(ALexer^.Current - ALexer^.Start), ALexer^.Start);

  Token := TranspilerLex(ALexer);
  WriteSemicolon()
END TranspileConstant;

PROCEDURE TranspileConstantPart(AContext: PTranspilerContext; ALexer: PLexer);
VAR
  Token: LexerToken;
BEGIN
  Token := LexerCurrent(ALexer);

  IF Token.Kind = lexerKindConst THEN
    WriteString('CONST');
    WriteLn();
    Token := TranspilerLex(ALexer);

    WHILE Token.Kind = lexerKindIdentifier DO
      TranspileConstant(AContext, ALexer);
      Token := TranspilerLex(ALexer)
    END;
    WriteLn()
  END
END TranspileConstantPart;

PROCEDURE TranspileModule(AContext: PTranspilerContext; ALexer: PLexer);
VAR
  Token: LexerToken;
  WrittenBytes: CARDINAL;
BEGIN
  Token := TranspilerLex(ALexer);

  IF Token.Kind = lexerKindDefinition THEN
    WriteString('DEFINITION ');
    Token := TranspilerLex(ALexer);
  ELSIF Token.Kind = lexerKindImplementation THEN
    WriteString('IMPLEMENTATION ');
    Token := TranspilerLex(ALexer)
  END;
  WriteString('MODULE ');

  (* Write the module name and end the line with a semicolon and newline. *)
  Token := TranspilerLex(ALexer);
  WrittenBytes := WriteNBytes(StdOut, ADDRESS(ALexer^.Current - ALexer^.Start), ALexer^.Start);

  Token := TranspilerLex(ALexer);
  WriteSemicolon();
  WriteLn();

  (* Write the module body. *)
  Token := TranspilerLex(ALexer);
  TranspileImportPart(AContext, ALexer);
  TranspileConstantPart(AContext, ALexer);

  Token := LexerCurrent(ALexer);
  WHILE Token.Kind <> lexerKindEof DO
    WrittenBytes := WriteNBytes(StdOut, ADDRESS(ALexer^.Current - ALexer^.Start), ALexer^.Start);
    WriteLn();

    Token := TranspilerLex(ALexer)
  END
END TranspileModule;

PROCEDURE Transpile(ALexer: PLexer);
VAR
  Token: LexerToken;
  WrittenBytes: CARDINAL;
  Context: TranspilerContext;
BEGIN
  TranspileModule(ADR(Context), ALexer)
END Transpile;

END Transpiler.