use base ("Understand::Codecheck");
use strict;
use constant ERR1 => "Else If with no following Else";

sub register_tr_text {
  my $check = shift;
  $check->add_tr_text(ERR1);

}


sub name {
  return "14.10 All if ... else if constructs shall be terminated with an else clause";
}

sub description {
  return "14.10 (Required) All if ... else if constructs shall be terminated with an else clause.";
}

sub detailed_description {
  return <<"END_DESC";
This rule applies whenever an if statement is followed by one or more else if statements; the final 
else if shall be followed by an else statement. In the case of a simple if statement then the else "
statement need not be included.
The requirement for a final else statement is defensive programming. The else statement shall 
either take appropriate action or contain a suitable comment as to why no action is taken. This is 
consistent with the requirement to have a final default clause in a switch statement (15.3).
For example this code is a simple if statement:
  if ( x < 0 ) 
  { 
     log_error(3); 
     x = 0; 
  }                 /* else not needed */
whereas the following code demonstrates an if, else if construct
  if ( x < 0 ) 
  { 
      log_error(3); 
      x = 0; 
  } 
  else if ( y < 0 ) 
  { 
      x = 3; 
  }
  else                 /* this else clause is required, even if the     */ 
  {                    /* programmer expects this will never be reached */ 
     /* no change in value of x */ 
  }
END_DESC
}

sub test_language {
  my $language = shift;
  return $language eq "C++";
}

sub test_entity {
  return 1;
}

sub test_global {
  return 0;
}


sub check {
  my $check = shift;
  my $file = shift;
  return unless $file->kind->check("file ~unresolved ~unknown");

  # create lexer once for file
  my $lexer = $file->lexer();
  return unless $lexer;

  # loop through functions defined in the file
  foreach my $ref ($file->filerefs("define","function",1)) {
      my $func = $ref->ent();
      my ($begin,$end) = getFunctionDefnLines($func);
      next if (!$begin);

      do_one_function($check,$file,$func,$lexer,$begin,$end);
  }
}


# Check one function.
sub do_one_function {
    my ($check,$file,$func,$lexer,$begin,$end) = @_;

    setupLexemes($lexer,$begin,$end);
    my $lexeme = nextLexeme();
    while ($lexeme && $lexeme->text() ne "{") {
  $lexeme = nextLexeme();
    }
    handle_statement($check,$file,$func);
}


# Begin with current lexeme at the first token of the statement, end
# with current lexeme at the first token past the end of the statement.
sub handle_statement {
    my ($check,$file,$func) = @_;
    my $lexeme = currentLexeme() or return;
    my $text = $lexeme->text();
    my $stmtLine=$lexeme->line_begin();
    my $debug=0;
	
	
    $check->violation($func,$file,$lexeme->line_begin(),$lexeme->column_begin(),"$stmtLine: Start Statement - $text") if $debug;
    # handle 'for', 'if', 'switch', 'while' statement
    if ($lexeme->token eq "Keyword" && ($text eq "for" || $text eq "if" || $text eq "switch" || $text eq "while")) {
      while ($lexeme && $lexeme->text() ne "("){
        $lexeme = nextLexeme() ;
      }
      return unless $lexeme;
      my $paren=1;
      while ($paren && ($lexeme = nextLexeme())) {
        $text = $lexeme->text();
        if ($text eq "(" && $lexeme->token eq "Punctuation") {
        ++$paren;
        }elsif ($text eq ")" && $lexeme->token eq "Punctuation") {
        --$paren;
        }	
      }	
      nextLexeme();
      handle_statement($check,$file,$func);
    }elsif ($text =~ /case|default/ && $lexeme->token eq "Keyword") {
		while ($lexeme && !($lexeme->text() eq ":" && $lexeme->token eq "Operator")) {
        $lexeme = nextLexeme();
      }
	$lexeme = nextLexeme();
	}elsif ($text eq "do" && $lexeme->token eq "Keyword") {
      # handle 'do' statement
      nextLexeme();
      handle_statement($check,$file,$func);
      handle_statement($check,$file,$func); # while (...);
    }elsif ($text eq "{" && $lexeme->token eq "Punctuation") {
      # handle compound statement
      $lexeme = nextLexeme();
      while ($lexeme && !($lexeme->text() eq "}" && $lexeme->token eq "Punctuation")) {
        handle_statement($check,$file,$func);
        $lexeme = currentLexeme();
      }
      nextLexeme();
    }elsif ($text eq "else" && $lexeme->token eq "Keyword") {
      $lexeme = nextLexeme();
      if($lexeme->text() eq "if" && $lexeme->token eq "Keyword"){    
        # handle 'else if'
        handle_statement($check,$file,$func);
        $lexeme = currentLexeme();
        if (!$lexeme || !( $lexeme->text() eq "else" && $lexeme->token eq "Keyword")) {
            $lexeme = lastLexeme() if !$lexeme;
            $check->violation($func,$file,$lexeme->line_begin(),$lexeme->column_begin(),ERR1);
        }
      }else{
        #handle else statements
        handle_statement($check,$file,$func);
      }
    }else {
      while ($lexeme && !($lexeme->text() =~ /;|}/ && $lexeme->token eq "Punctuation")) {
        $lexeme = nextLexeme();
      }
      nextLexeme();
     
    }
     $check->violation($func,$file,$lexeme->line_begin(),$lexeme->column_begin(),"$stmtLine: End Statement") if $lexeme && $debug;
}


# Pass a function entity. Return an array of:
#   the begin line
#   the end line
#   the defn file entity
# Return undef if this info cannot be provided.
sub getFunctionDefnLines {
    my $func = shift;
    my $begin_ref = $func->ref("definein");
    my $end_ref = $func->ref("end");
    return undef if (!$begin_ref || !$end_ref);
    return ($begin_ref->line(), $end_ref->line(), $begin_ref->file());
}


# Setup the global lexemes array once per function, to use
# the nextLexeme() sub.
my @lexemes=();
my $lexeme_pos=0;
sub setupLexemes {
    my $lexer = shift;
    my $begin = shift;
    my $end = shift;
    @lexemes = $lexer->lexemes($begin,$end);
    $lexeme_pos = 0;
}

# Return the current lexeme.
sub currentLexeme {
    return $lexemes[$lexeme_pos-1] if $lexeme_pos < $#lexemes;
    return undef;
}

# Return the last lexeme.
sub lastLexeme {
    return $lexemes[$#lexemes-1]
}

# Return the next interesting lexeme or undef when all lexemes
# are used.
sub nextLexeme {
    while ($lexeme_pos < $#lexemes) {
      my $lexeme = $lexemes[$lexeme_pos++];
      next if ($lexeme->token() =~ m/Comment|Whitespace|Newline/);
      return $lexeme;
    };
    return undef;
}