package Email::Simple::Header;

use strict;
use Carp ();

require Email::Simple;

$Email::Simple::Header::VERSION = '2.005';

=head1 NAME

Email::Simple::Header - the header of an Email::Simple message

=head1 SYNOPSIS

  my $email = Email::Simple->new($text);

  my $header = $email->head;
  print $header->as_string;

=head1 DESCRIPTION

This method implements the headers of an Email::Simple object.  It is a very
minimal interface, and is mostly for private consumption at the moment.

=head1 METHODS

=head2 new

  my $header = Email::Simple::Header->new($head, \%arg);

C<$head> is a string containing a valid email header, or a reference to such a
string.  If a reference is passed in, don't expect that it won't be altered.

Valid arguments are:

  crlf - the header's newline; defaults to CRLF

=cut

# We need to be able to:
#   * get all values by lc name
#   * produce all pairs, with case intact

sub new {
  my ($class, $head, $arg) = @_;

  my $head_ref = ref $head ? $head : \$head;

  my $self = { mycrlf => $arg->{crlf} || "\x0d\x0a", };

  my $headers = $class->_header_to_list($head_ref, $self->{mycrlf});

  #  for my $header (@$headers) {
  #    push @{ $self->{order} }, $header->[0];
  #    push @{ $self->{head}{ $header->[0] } }, $header->[1];
  #  }
  #
  #  $self->{header_names} = { map { lc $_ => $_ } keys %{ $self->{head} } };
  $self->{headers} = $headers;

  bless $self => $class;
}

sub _header_to_list {
  my ($self, $head, $mycrlf) = @_;

  my @headers;

  my $crlf = Email::Simple->__crlf_re;

  while ($$head =~ m/\G(.+?)$crlf/go) {
    local $_ = $1;
    if (s/^\s+// or not /^([^:]+):\s*(.*)/) {
      # This is a continuation line. We fold it onto the end of
      # the previous header.
      next if !@headers;  # Well, that sucks.  We're continuing nothing?

      $headers[-1] .= $headers[-1] ? " $_" : $_;
    } else {
      push @headers, $1, $2;
    }
  }

  return \@headers;
}

=head2 as_string

  my $string = $header->as_string(\%arg);

This returns a stringified version of the header.

=cut

# RFC 2822, 3.6:
# ...for the purposes of this standard, header fields SHOULD NOT be reordered
# when a message is transported or transformed.  More importantly, the trace
# header fields and resent header fields MUST NOT be reordered, and SHOULD be
# kept in blocks prepended to the message.

sub as_string {
  my ($self, $arg) = @_;
  $arg ||= {};

  my $header_str = '';

  my $headers = $self->{headers};

  my $fold_arg = {
    # at     => (exists $arg->{fold_at} ? $arg->{fold_at} : $self->default_fold_at),
    # indent => (exists $arg->{fold_indent} ? $arg->{fold_indent} : $self->default_fold_indent),
    at     => $self->_default_fold_at,
    indent => $self->_default_fold_indent,
  };

  for (my $i = 0; $i < @$headers; $i += 2) {
    my $header = "$headers->[$i]: $headers->[$i + 1]";

    $header_str .= lc $headers->[$i] eq 'content-type'
                 ? $header . $self->crlf
                 : $self->_fold($header, $fold_arg);
  }

  return $header_str;
}

=head2 header_names

This method returns the unique header names found in this header, in no
particular order.

=cut

sub header_names {
  my $headers = $_[0]->{headers};

  my %seen;
  grep  { !$seen{ lc $_ }++ }
    map { $headers->[ $_ * 2 ] } 0 .. int($#$headers / 2);
}

=head2 header_pairs

This method returns all the field/value pairs in the header, in the order that
they appear in the header.

=cut

sub header_pairs {
  my ($self) = @_;

  return @{ $self->{headers} };
}

=head2 header

  my $first_value = $header->header($field);
  my @all_values  = $header->header($field);

This method returns the value or values of the given header field.  If the
named field does not appear in the header, this method returns false.

=cut

sub header {
  my ($self, $field) = @_;

  my $headers  = $self->{headers};
  my $lc_field = lc $field;

  if (wantarray) {
    return map { @$headers[ $_ * 2 + 1 ] }
      grep { lc $headers->[ $_ * 2 ] eq $lc_field } 0 .. int($#$headers / 2);
  } else {
    for (0 .. int($#$headers / 2)) {
      return $headers->[ $_ * 2 + 1 ] if lc $headers->[ $_ * 2 ] eq $lc_field;
    }
    return;
  }
}

=head2 header_set

  $header->header_set($field => @values);

This method updates the value of the given header.  Existing headers have their
values set in place.  Additional headers are added at the end.  If no values
are given to set, the header will be removed from to the message entirely.

=cut

# Header fields are lines composed of a field name, followed by a colon (":"),
# followed by a field body, and terminated by CRLF.  A field name MUST be
# composed of printable US-ASCII characters (i.e., characters that have values
# between 33 and 126, inclusive), except colon.  A field body may be composed
# of any US-ASCII characters, except for CR and LF.

# However, a field body may contain CRLF when used in header "folding" and
# "unfolding" as described in section 2.2.3.

sub header_set {
  my ($self, $field, @data) = @_;

  # I hate this block. -- rjbs, 2006-10-06
  if ($Email::Simple::GROUCHY) {
    Carp::croak "field name contains illegal characters"
      unless $field =~ /^[\x21-\x39\x3b-\x7e]+$/;
    Carp::carp "field name is not limited to hyphens and alphanumerics"
      unless $field =~ /^[\w-]+$/;
  }

  my $headers = $self->{headers};

  my $lc_field = lc $field;
  my @indices = grep { lc $headers->[$_] eq $lc_field }
    map { $_ * 2 } 0 .. int($#$headers / 2);

  if (@indices > @data) {
    my $overage = @indices - @data;
    splice @{$headers}, $_, 2 for reverse @indices[ -$overage .. -1 ];
    pop @indices for (1 .. $overage);
  } elsif (@data > @indices) {
    my $underage = @data - @indices;
    for (1 .. $underage) {
      push @$headers, $field, undef;  # temporary value
      push @indices, $#$headers - 1;
    }
  }

  for (0 .. $#indices) {
    $headers->[ $indices[$_] + 1 ] = $data[$_];
  }

  return wantarray ? @data : $data[0];
}

=head2 crlf

This method returns the newline string used in the header.

=cut

sub crlf { $_[0]->{mycrlf} }

# =head2 fold
# 
#   my $folded = $header->fold($line, \%arg);
# 
# Given a header string, this method returns a folded version, if the string is
# long enough to warrant folding.  This method is used internally.
# 
# Valid arguments are:
# 
#   at      - fold lines to be no longer than this length, if possible
#             if given and false, never fold headers
#   indent  - indent lines with this string
# 
# =cut

sub _fold {
  my ($self, $line, $arg) = @_;
  $arg ||= {};

  $arg->{at} = $self->_default_fold_at unless exists $arg->{at};

  return $line . $self->crlf unless $arg->{at} and $arg->{at} > 0;

  my $limit  = ($arg->{at} || $self->_default_fold_at) - 1;

  return $line . $self->crlf if length $line <= $limit;

  $arg->{indent} = $self->_default_fold_indent unless exists $arg->{indent};

  my $indent = $arg->{indent} || $self->_default_fold_indent;

  # We know it will not contain any new lines at present
  my $folded = "";
  while ($line) {
    if ($line =~ s/^(.{0,$limit})(\s|\z)//) {
      $folded .= $1 . $self->crlf;
      $folded .= $indent if $line;
    } else {
      # Basically nothing we can do. :(
      $folded .= $line . $self->crlf;
      last;
    }
  }

  return $folded;
}

# =head2 default_fold_at
# 
# This method (provided for subclassing) returns the default length at which to
# try to fold header lines.  The default default is 78.
# 
# =cut

sub _default_fold_at { 78 }

# =head2 default_fold_indent
# 
# This method (provided for subclassing) returns the default string used to
# indent folded headers.  The default default is a single space.
# 
# =cut

sub _default_fold_indent { " " }

=head1 PERL EMAIL PROJECT

This module is maintained by the Perl Email Project

L<http://emailproject.perl.org/wiki/Email::Simple::Header>

=head1 COPYRIGHT AND LICENSE

Copyright 2006-2007 by Ricardo SIGNES

Copyright 2004 by Casey West

Copyright 2003 by Simon Cozens

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.

=cut

1;
