// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:front_end/src/base/errors.dart';
import 'package:front_end/src/fasta/fasta_codes.dart';
import 'package:front_end/src/fasta/scanner/error_token.dart';
import 'package:front_end/src/fasta/scanner/token.dart';
import 'package:front_end/src/fasta/scanner/token_constants.dart';

/**
 * The error codes used for errors detected by the scanner.
 */
class ScannerErrorCode extends ErrorCode {
  /**
   * Parameters:
   * 0: the illegal character
   */
  static const ScannerErrorCode ILLEGAL_CHARACTER =
      const ScannerErrorCode('ILLEGAL_CHARACTER', "Illegal character '{0}'.");

  static const ScannerErrorCode MISSING_DIGIT =
      const ScannerErrorCode('MISSING_DIGIT', "Decimal digit expected.");

  static const ScannerErrorCode MISSING_HEX_DIGIT = const ScannerErrorCode(
      'MISSING_HEX_DIGIT', "Hexidecimal digit expected.");

  static const ScannerErrorCode MISSING_QUOTE =
      const ScannerErrorCode('MISSING_QUOTE', "Expected quote (' or \").");

  /**
   * Parameters:
   * 0: the path of the file that cannot be read
   */
  static const ScannerErrorCode UNABLE_GET_CONTENT = const ScannerErrorCode(
      'UNABLE_GET_CONTENT', "Unable to get content of '{0}'.");

  static const ScannerErrorCode UNTERMINATED_MULTI_LINE_COMMENT =
      const ScannerErrorCode(
          'UNTERMINATED_MULTI_LINE_COMMENT',
          "Unterminated multi-line comment.",
          "Try terminating the comment with '*/', or "
          "removing any unbalanced occurances of '/*' (because comments nest in Dart).");

  static const ScannerErrorCode UNTERMINATED_STRING_LITERAL =
      const ScannerErrorCode(
          'UNTERMINATED_STRING_LITERAL', "Unterminated string literal.");

  /**
   * Initialize a newly created error code to have the given [name]. The message
   * associated with the error will be created from the given [message]
   * template. The correction associated with the error will be created from the
   * given [correction] template.
   */
  const ScannerErrorCode(String name, String message, [String correction])
      : super(name, message, correction);

  @override
  ErrorSeverity get errorSeverity => ErrorSeverity.ERROR;

  @override
  ErrorType get type => ErrorType.SYNTACTIC_ERROR;
}

/**
 * Used to report a scan error at the given offset.
 * The [errorCode] is the error code indicating the nature of the error.
 * The [arguments] are any arguments needed to complete the error message.
 */
typedef ReportError(
    ScannerErrorCode errorCode, int offset, List<Object> arguments);

/**
 *  Translates the given error [token] into an analyzer error and reports it
 *  using [reportError].
 */
void translateErrorToken(ErrorToken token, ReportError reportError) {
  int charOffset = token.charOffset;
  // TODO(paulberry,ahe): why is endOffset sometimes null?
  int endOffset = token.endOffset ?? charOffset;
  void _makeError(ScannerErrorCode errorCode, List<Object> arguments) {
    if (_isAtEnd(token, charOffset)) {
      // Analyzer never generates an error message past the end of the input,
      // since such an error would not be visible in an editor.
      // TODO(paulberry,ahe): would it make sense to replicate this behavior
      // in fasta, or move it elsewhere in analyzer?
      charOffset--;
    }
    reportError(errorCode, charOffset, arguments);
  }

  var errorCode = token.errorCode;
  switch (errorCode.analyzerCode) {
    case "UNTERMINATED_STRING_LITERAL":
      // TODO(paulberry,ahe): Fasta reports the error location as the entire
      // string; analyzer expects the end of the string.
      charOffset = endOffset;
      return _makeError(ScannerErrorCode.UNTERMINATED_STRING_LITERAL, null);

    case "UNTERMINATED_MULTI_LINE_COMMENT":
      // TODO(paulberry,ahe): Fasta reports the error location as the entire
      // comment; analyzer expects the end of the comment.
      charOffset = endOffset;
      return _makeError(ScannerErrorCode.UNTERMINATED_MULTI_LINE_COMMENT, null);

    case "MISSING_DIGIT":
      // TODO(paulberry,ahe): Fasta reports the error location as the entire
      // number; analyzer expects the end of the number.
      charOffset = endOffset - 1;
      return _makeError(ScannerErrorCode.MISSING_DIGIT, null);

    case "MISSING_HEX_DIGIT":
      // TODO(paulberry,ahe): Fasta reports the error location as the entire
      // number; analyzer expects the end of the number.
      charOffset = endOffset - 1;
      return _makeError(ScannerErrorCode.MISSING_HEX_DIGIT, null);

    case "ILLEGAL_CHARACTER":
      return _makeError(ScannerErrorCode.ILLEGAL_CHARACTER, [token.character]);

    default:
      if (errorCode == codeUnmatchedToken ||
          errorCode == codeUnexpectedDollarInString) {
        return null;
      }
      throw new UnimplementedError('$errorCode');
  }
}

/**
 * Determines whether the given [charOffset], which came from the non-EOF token
 * [token], represents the end of the input.
 */
bool _isAtEnd(Token token, int charOffset) {
  while (true) {
    // Skip to the next token.
    token = token.next;
    // If we've found an EOF token, its charOffset indicates where the end of
    // the input is.
    if (token.isEof) return token.charOffset == charOffset;
    // If we've found a non-error token, then we know there is additional input
    // text after [charOffset].
    if (token.info.kind != BAD_INPUT_TOKEN) return false;
    // Otherwise keep looking.
  }
}
