package Mojo::Date;
use Mojo::Base -base;
use overload bool => sub {1}, '""' => sub { shift->to_string }, fallback => 1;

use Time::Local qw(timegm);

has epoch => sub {time};

my $RFC3339_RE = qr/
  ^(\d+)-(\d+)-(\d+)\D+(\d+):(\d+):(\d+(?:\.\d+)?)   # Date and time
  (?:Z|([+-])(\d+):(\d+))?$                          # Offset
/xi;

my @DAYS   = qw(Sun Mon Tue Wed Thu Fri Sat);
my @MONTHS = qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec);
my %MONTHS;
@MONTHS{@MONTHS} = (0 .. 11);

sub new { @_ > 1 ? shift->SUPER::new->parse(@_) : shift->SUPER::new }

sub parse {
  my ($self, $date) = @_;

  # epoch (784111777)
  return $self->epoch($date) if $date =~ /^\d+$|^\d+\.\d+$/;

  # RFC 822/1123 (Sun, 06 Nov 1994 08:49:37 GMT)
  # RFC 850/1036 (Sunday, 06-Nov-94 08:49:37 GMT)
  my $offset = 0;
  my ($day, $month, $year, $h, $m, $s);
  if ($date =~ /^\w+\W+(\d+)\W+(\w+)\W+(\d+)\W+(\d+):(\d+):(\d+)\W*\w+$/) {
    ($day, $month, $year, $h, $m, $s) = ($1, $MONTHS{$2}, $3, $4, $5, $6);
  }

  # RFC 3339 (1994-11-06T08:49:37Z)
  elsif ($date =~ $RFC3339_RE) {
    ($year, $month, $day, $h, $m, $s) = ($1, $2 - 1, $3, $4, $5, $6);
    $offset = (($8 * 3600) + ($9 * 60)) * ($7 eq '+' ? -1 : 1) if $7;
  }

  # ANSI C asctime() (Sun Nov  6 08:49:37 1994)
  elsif ($date =~ /^\w+\s+(\w+)\s+(\d+)\s+(\d+):(\d+):(\d+)\s+(\d+)$/) {
    ($month, $day, $h, $m, $s, $year) = ($MONTHS{$1}, $2, $3, $4, $5, $6);
  }

  # Invalid
  else { return $self->epoch(undef) }

  my $epoch = eval { timegm $s, $m, $h, $day, $month, $year };
  return $self->epoch((defined $epoch && ($epoch += $offset) >= 0) ? $epoch : undef);
}

sub to_datetime {

  # RFC 3339 (1994-11-06T08:49:37Z)
  my ($s, $m, $h, $day, $month, $year) = gmtime(my $epoch = shift->epoch);
  my $str = sprintf '%04d-%02d-%02dT%02d:%02d:%02d', $year + 1900, $month + 1, $day, $h, $m, $s;
  return $str . ($epoch =~ /(\.\d+)$/ ? $1 : '') . 'Z';
}

sub to_string {

  # RFC 7231 (Sun, 06 Nov 1994 08:49:37 GMT)
  my ($s, $m, $h, $mday, $month, $year, $wday) = gmtime shift->epoch;
  return sprintf '%s, %02d %s %04d %02d:%02d:%02d GMT', $DAYS[$wday], $mday, $MONTHS[$month], $year + 1900, $h, $m, $s;
}

1;

=encoding utf8

=head1 NAME

Mojo::Date - HTTP date

=head1 SYNOPSIS

  use Mojo::Date;

  # Parse
  my $date = Mojo::Date->new('Sun, 06 Nov 1994 08:49:37 GMT');
  say $date->epoch;

  # Build
  my $date = Mojo::Date->new(time + 60);
  say "$date";

=head1 DESCRIPTION

L<Mojo::Date> implements HTTP date and time functions, based on L<RFC 7230|https://tools.ietf.org/html/rfc7230>, L<RFC
7231|https://tools.ietf.org/html/rfc7231> and L<RFC 3339|https://tools.ietf.org/html/rfc3339>.

=head1 ATTRIBUTES

L<Mojo::Date> implements the following attributes.

=head2 epoch

  my $epoch = $date->epoch;
  $date     = $date->epoch(784111777);

Epoch seconds, defaults to the current time.

=head1 METHODS

L<Mojo::Date> inherits all methods from L<Mojo::Base> and implements the following new ones.

=head2 new

  my $date = Mojo::Date->new;
  my $date = Mojo::Date->new('Sun Nov  6 08:49:37 1994');

Construct a new L<Mojo::Date> object and L</"parse"> date if necessary.

=head2 parse

  $date = $date->parse('Sun Nov  6 08:49:37 1994');

Parse date.

  # Epoch
  say Mojo::Date->new('784111777')->epoch;
  say Mojo::Date->new('784111777.21')->epoch;

  # RFC 822/1123
  say Mojo::Date->new('Sun, 06 Nov 1994 08:49:37 GMT')->epoch;

  # RFC 850/1036
  say Mojo::Date->new('Sunday, 06-Nov-94 08:49:37 GMT')->epoch;

  # Ansi C asctime()
  say Mojo::Date->new('Sun Nov  6 08:49:37 1994')->epoch;

  # RFC 3339
  say Mojo::Date->new('1994-11-06T08:49:37Z')->epoch;
  say Mojo::Date->new('1994-11-06T08:49:37')->epoch;
  say Mojo::Date->new('1994-11-06T08:49:37.21Z')->epoch;
  say Mojo::Date->new('1994-11-06T08:49:37+01:00')->epoch;
  say Mojo::Date->new('1994-11-06T08:49:37-01:00')->epoch;

=head2 to_datetime

  my $str = $date->to_datetime;

Render L<RFC 3339|https://tools.ietf.org/html/rfc3339> date and time.

  # "1994-11-06T08:49:37Z"
  Mojo::Date->new(784111777)->to_datetime;

  # "1994-11-06T08:49:37.21Z"
  Mojo::Date->new(784111777.21)->to_datetime;

=head2 to_string

  my $str = $date->to_string;

Render date suitable for HTTP messages.

  # "Sun, 06 Nov 1994 08:49:37 GMT"
  Mojo::Date->new(784111777)->to_string;

=head1 OPERATORS

L<Mojo::Date> overloads the following operators.

=head2 bool

  my $bool = !!$date;

Always true.

=head2 stringify

  my $str = "$date";

Alias for L</"to_string">.

=head1 SEE ALSO

L<Mojolicious>, L<Mojolicious::Guides>, L<https://mojolicious.org>.

=cut