package Mojo::Content;
use Mojo::Base 'Mojo::EventEmitter';

use Carp                qw(croak);
use Compress::Raw::Zlib qw(WANT_GZIP Z_STREAM_END);
use Mojo::Headers;
use Mojo::SSE    qw(build_event parse_event);
use Scalar::Util qw(looks_like_number);

has [qw(auto_decompress auto_relax relaxed skip_body)];
has headers           => sub { Mojo::Headers->new };
has max_buffer_size   => sub { $ENV{MOJO_MAX_BUFFER_SIZE}   || 262144 };
has max_leftover_size => sub { $ENV{MOJO_MAX_LEFTOVER_SIZE} || 262144 };

my $BOUNDARY_RE = qr!multipart.*boundary\s*=\s*(?:"([^"]+)"|([\w'(),.:?\-+/]+))!i;

sub body_contains { croak 'Method "body_contains" not implemented by subclass' }
sub body_size     { croak 'Method "body_size" not implemented by subclass' }

sub boundary { (shift->headers->content_type // '') =~ $BOUNDARY_RE ? $1 // $2 : undef }

sub charset {
  my $type = shift->headers->content_type // '';
  return $type =~ /charset\s*=\s*"?([^"\s;]+)"?/i ? $1 : undef;
}

sub clone {
  my $self = shift;
  return undef if $self->is_dynamic;
  return $self->new(headers => $self->headers->clone);
}

sub generate_body_chunk {
  my ($self, $offset) = @_;

  $self->emit(drain => $offset) unless length($self->{body_buffer} //= '');
  return delete $self->{body_buffer} if length $self->{body_buffer};
  return ''                          if $self->{eof};

  my $len = $self->headers->content_length;
  return looks_like_number $len && $len == $offset ? '' : undef;
}

sub get_body_chunk { croak 'Method "get_body_chunk" not implemented by subclass' }

sub get_header_chunk { substr shift->_headers->{header_buffer}, shift, 131072 }

sub header_size { length shift->_headers->{header_buffer} }

sub headers_contain { index(shift->_headers->{header_buffer}, shift) >= 0 }

sub is_chunked { !!shift->headers->transfer_encoding }

sub is_compressed { lc(shift->headers->content_encoding // '') eq 'gzip' }

sub is_dynamic { !!$_[0]{dynamic} }

sub is_finished { (shift->{state} // '') eq 'finished' }

sub is_limit_exceeded { !!shift->{limit} }

sub is_multipart {undef}

sub is_parsing_body { (shift->{state} // '') eq 'body' }

sub is_sse { (shift->headers->content_type // '') eq 'text/event-stream' }

sub leftovers { shift->{buffer} }

sub parse {
  my $self = shift;

  # Headers
  $self->_parse_until_body(@_);
  return $self if $self->{state} eq 'headers';

  # Chunked content
  $self->{real_size} //= 0;
  if ($self->is_chunked) {
    $self->_parse_chunked;
    $self->{state} = 'finished' if ($self->{chunk_state} // '') eq 'finished';
  }

  # SSE
  elsif ($self->is_sse) { $self->_parse_sse }

  # Not chunked, pass through to second buffer
  else {
    $self->{real_size} += length $self->{pre_buffer};
    my $limit = $self->is_finished && length($self->{buffer}) > $self->max_leftover_size;
    $self->{buffer} .= $self->{pre_buffer} unless $limit;
    $self->{pre_buffer} = '';
  }

  # No content
  if ($self->skip_body) {
    $self->{state} = 'finished';
    return $self;
  }

  # Relaxed parsing
  my $headers = $self->headers;
  my $len     = $headers->content_length // '';
  if ($self->auto_relax && !length $len) {
    my $connection = lc($headers->connection // '');
    $self->relaxed(1) if $connection eq 'close' || !$connection;
  }

  # Chunked or relaxed content
  if ($self->is_chunked || $self->relaxed) {
    $self->_decompress($self->{buffer} //= '');
    $self->{size} += length $self->{buffer};
    $self->{buffer} = '';
    return $self;
  }

  # Normal content
  $len = 0 unless looks_like_number $len;
  if ((my $need = $len - ($self->{size} ||= 0)) > 0) {
    my $len   = length $self->{buffer};
    my $chunk = substr $self->{buffer}, 0, $need > $len ? $len : $need, '';
    $self->_decompress($chunk);
    $self->{size} += length $chunk;
  }
  $self->{state} = 'finished' if $len <= $self->progress;

  return $self;
}

sub parse_body {
  my $self = shift;
  $self->{state} = 'body';
  return $self->parse(@_);
}

sub progress {
  my $self = shift;
  return 0 unless my $state = $self->{state};
  return 0 unless $state eq 'body' || $state eq 'finished';
  return $self->{raw_size} - ($self->{header_size} || 0);
}

sub write {
  my ($self, $chunk, $cb) = @_;

  $self->{dynamic} = 1;
  $self->{body_buffer} .= $chunk if defined $chunk;
  $self->once(drain => $cb)      if $cb;
  $self->{eof} = 1               if defined $chunk && !length $chunk;

  return $self;
}

sub write_chunk {
  my ($self, $chunk, $cb) = @_;

  $self->headers->transfer_encoding('chunked') unless $self->{chunked};
  @{$self}{qw(chunked dynamic)} = (1, 1);

  $self->{body_buffer} .= $self->_build_chunk($chunk) if defined $chunk;
  $self->once(drain => $cb)                           if $cb;
  $self->{eof} = 1                                    if defined $chunk && !length $chunk;

  return $self;
}

sub write_sse {
  my ($self, $event, $cb) = @_;

  $self->headers->content_type('text/event-stream') unless $self->{sse};
  $self->{sse} = 1;

  return $self->write unless defined $event;
  return $self->write(build_event($event), $cb);
}

sub _build_chunk {
  my ($self, $chunk) = @_;

  # End
  return "\x0d\x0a0\x0d\x0a\x0d\x0a" unless length $chunk;

  # First chunk has no leading CRLF
  my $crlf = $self->{chunks}++ ? "\x0d\x0a" : '';
  return $crlf . sprintf('%x', length $chunk) . "\x0d\x0a$chunk";
}

sub _decompress {
  my ($self, $chunk) = @_;

  # No compression
  return $self->emit(read => $chunk) unless $self->auto_decompress && $self->is_compressed;

  # Decompress
  $self->{post_buffer} .= $chunk;
  my $gz     = $self->{gz} //= Compress::Raw::Zlib::Inflate->new(WindowBits => WANT_GZIP);
  my $status = $gz->inflate(\$self->{post_buffer}, my $out);
  $self->emit(read => $out) if defined $out;

  # Replace Content-Encoding with Content-Length
  $self->headers->content_length($gz->total_out)->remove('Content-Encoding') if $status == Z_STREAM_END;

  # Check buffer size
  @$self{qw(state limit)} = ('finished', 1) if length($self->{post_buffer} // '') > $self->max_buffer_size;
}

sub _headers {
  my $self = shift;
  return $self if defined $self->{header_buffer};
  my $headers = $self->headers->to_string;
  $self->{header_buffer} = $headers ? "$headers\x0d\x0a\x0d\x0a" : "\x0d\x0a";
  return $self;
}

sub _parse_chunked {
  my $self = shift;

  # Trailing headers
  return $self->_parse_chunked_trailing_headers if ($self->{chunk_state} // '') eq 'trailing_headers';

  while (my $len = length $self->{pre_buffer}) {

    # Start new chunk (ignore the chunk extension)
    unless ($self->{chunk_len}) {
      last unless $self->{pre_buffer} =~ s/^(?:\x0d?\x0a)?([0-9a-fA-F]+).*\x0a//;
      next if $self->{chunk_len} = hex $1;

      # Last chunk
      $self->{chunk_state} = 'trailing_headers';
      last;
    }

    # Remove as much as possible from payload
    $len = $self->{chunk_len} if $self->{chunk_len} < $len;
    $self->{buffer} .= substr $self->{pre_buffer}, 0, $len, '';
    $self->{real_size} += $len;
    $self->{chunk_len} -= $len;
  }

  # Trailing headers
  $self->_parse_chunked_trailing_headers if ($self->{chunk_state} // '') eq 'trailing_headers';

  # Check buffer size
  @$self{qw(state limit)} = ('finished', 1) if length($self->{pre_buffer} // '') > $self->max_buffer_size;
}

sub _parse_chunked_trailing_headers {
  my $self = shift;

  my $headers = $self->headers->parse(delete $self->{pre_buffer});
  return unless $headers->is_finished;
  $self->{chunk_state} = 'finished';

  # Take care of leftover and replace Transfer-Encoding with Content-Length
  $self->{buffer} .= $headers->leftovers;
  $headers->remove('Transfer-Encoding');
  $headers->content_length($self->{real_size}) unless $headers->content_length;
}

sub _parse_headers {
  my $self = shift;

  my $headers = $self->headers->parse(delete $self->{pre_buffer});
  return unless $headers->is_finished;
  $self->{state} = 'body';

  # Take care of leftovers
  my $leftovers = $self->{pre_buffer} = $headers->leftovers;
  $self->{header_size} = $self->{raw_size} - length $leftovers;
}

sub _parse_sse {
  my $self = shift;

  # Connection established
  $self->emit('sse') unless $self->{sse};
  $self->{sse} = 1;

  # Parse SSE
  while (my $event = parse_event(\$self->{pre_buffer})) { $self->emit(sse => $event) }

  # Check buffer size
  @$self{qw(state limit)} = ('finished', 1) if length($self->{pre_buffer} // '') > $self->max_buffer_size;
}

sub _parse_until_body {
  my ($self, $chunk) = @_;

  $self->{raw_size} += length($chunk //= '');
  $self->{pre_buffer} .= $chunk;
  $self->_parse_headers if ($self->{state} ||= 'headers') eq 'headers';
  $self->emit('body')   if $self->{state} ne 'headers' && !$self->{body}++;
}

1;

=encoding utf8

=head1 NAME

Mojo::Content - HTTP content base class

=head1 SYNOPSIS

  package Mojo::Content::MyContent;
  use Mojo::Base 'Mojo::Content';

  sub body_contains  {...}
  sub body_size      {...}
  sub get_body_chunk {...}

=head1 DESCRIPTION

L<Mojo::Content> is an abstract base class for HTTP content containers, based on L<RFC
7230|https://tools.ietf.org/html/rfc7230> and L<RFC 7231|https://tools.ietf.org/html/rfc7231>, like
L<Mojo::Content::MultiPart> and L<Mojo::Content::Single>.

=head1 EVENTS

L<Mojo::Content> inherits all events from L<Mojo::EventEmitter> and can emit the following new ones.

=head2 body

  $content->on(body => sub ($content) {...});

Emitted once all headers have been parsed and the body starts.

  $content->on(body => sub ($content) {
    $content->auto_upgrade(0) if $content->headers->header('X-No-MultiPart');
  });

=head2 drain

  $content->on(drain => sub ($content, $offset) {...});

Emitted once all data has been written.

  $content->on(drain => sub ($content) {
    $content->write_chunk(time);
  });

=head2 read

  $content->on(read => sub ($content, $bytes) {...});

Emitted when a new chunk of content arrives.

  $content->on(read => sub ($content, $bytes) {
    say "Streaming: $bytes";
  });

=head2 sse

  $content->on(sse => sub ($content, $event) {...});

Emitted when a new Server-Sent Event (SSE) connection has been established and for each new event that arrives. Note
that this event is B<EXPERIMENTAL> and may change without warning!

  $content->on(sse => sub ($content, $event) {
    if ($event) { say "Type: $event->{type}, Data: $event->{data}" }
    else        { say "SSE connection established" }
  });

=head1 ATTRIBUTES

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

=head2 auto_decompress

  my $bool = $content->auto_decompress;
  $content = $content->auto_decompress($bool);

Decompress content automatically if L</"is_compressed"> is true.

=head2 auto_relax

  my $bool = $content->auto_relax;
  $content = $content->auto_relax($bool);

Try to detect when relaxed parsing is necessary.

=head2 headers

  my $headers = $content->headers;
  $content    = $content->headers(Mojo::Headers->new);

Content headers, defaults to a L<Mojo::Headers> object.

=head2 max_buffer_size

  my $size = $content->max_buffer_size;
  $content = $content->max_buffer_size(1024);

Maximum size in bytes of buffer for content parser, defaults to the value of the C<MOJO_MAX_BUFFER_SIZE> environment
variable or C<262144> (256KiB).

=head2 max_leftover_size

  my $size = $content->max_leftover_size;
  $content = $content->max_leftover_size(1024);

Maximum size in bytes of buffer for pipelined HTTP requests, defaults to the value of the C<MOJO_MAX_LEFTOVER_SIZE>
environment variable or C<262144> (256KiB).

=head2 relaxed

  my $bool = $content->relaxed;
  $content = $content->relaxed($bool);

Activate relaxed parsing for responses that are terminated with a connection close.

=head2 skip_body

  my $bool = $content->skip_body;
  $content = $content->skip_body($bool);

Skip body parsing and finish after headers.

=head1 METHODS

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

=head2 body_contains

  my $bool = $content->body_contains('foo bar baz');

Check if content contains a specific string. Meant to be overloaded in a subclass.

=head2 body_size

  my $size = $content->body_size;

Content size in bytes. Meant to be overloaded in a subclass.

=head2 boundary

  my $boundary = $content->boundary;

Extract multipart boundary from C<Content-Type> header.

=head2 charset

  my $charset = $content->charset;

Extract charset from C<Content-Type> header.

=head2 clone

  my $clone = $content->clone;

Return a new L<Mojo::Content> object cloned from this content if possible, otherwise return C<undef>.

=head2 generate_body_chunk

  my $bytes = $content->generate_body_chunk(0);

Generate dynamic content.

=head2 get_body_chunk

  my $bytes = $content->get_body_chunk(0);

Get a chunk of content starting from a specific position. Meant to be overloaded in a subclass.

=head2 get_header_chunk

  my $bytes = $content->get_header_chunk(13);

Get a chunk of the headers starting from a specific position. Note that this method finalizes the content.

=head2 header_size

  my $size = $content->header_size;

Size of headers in bytes. Note that this method finalizes the content.

=head2 headers_contain

  my $bool = $content->headers_contain('foo bar baz');

Check if headers contain a specific string. Note that this method finalizes the content.

=head2 is_chunked

  my $bool = $content->is_chunked;

Check if C<Transfer-Encoding> header indicates chunked transfer encoding.

=head2 is_compressed

  my $bool = $content->is_compressed;

Check C<Content-Encoding> header for C<gzip> value.

=head2 is_dynamic

  my $bool = $content->is_dynamic;

Check if content will be dynamically generated, which prevents L</"clone"> from working.

=head2 is_finished

  my $bool = $content->is_finished;

Check if parser is finished.

=head2 is_limit_exceeded

  my $bool = $content->is_limit_exceeded;

Check if buffer has exceeded L</"max_buffer_size">.

=head2 is_multipart

  my $bool = $content->is_multipart;

False, this is not a L<Mojo::Content::MultiPart> object.

=head2 is_parsing_body

  my $bool = $content->is_parsing_body;

Check if body parsing started yet.

=head2 is_sse

  my $bool = $content->is_sse;

Check if C<Content-Type> header indicates Server-Sent Events (SSE). Note that this method is B<EXPERIMENTAL> and may
change without warning!

=head2 leftovers

  my $bytes = $content->leftovers;

Get leftover data from content parser.

=head2 parse

  $content
    = $content->parse("Content-Length: 12\x0d\x0a\x0d\x0aHello World!");

Parse content chunk.

=head2 parse_body

  $content = $content->parse_body('Hi!');

Parse body chunk and skip headers.

=head2 progress

  my $size = $content->progress;

Size of content already received from message in bytes.

=head2 write

  $content = $content->write;
  $content = $content->write('');
  $content = $content->write($bytes);
  $content = $content->write($bytes => sub {...});

Write dynamic content non-blocking, the optional drain callback will be executed once all data has been written.
Calling this method without a chunk of data will finalize the L</"headers"> and allow for dynamic content to be written
later. You can write an empty chunk of data at any time to end the stream.

  # Make sure previous chunk of data has been written before continuing
  $content->write('He' => sub ($content) {
    $content->write('llo!' => sub ($content) {
      $content->write('');
    });
  });

=head2 write_chunk

  $content = $content->write_chunk;
  $content = $content->write_chunk('');
  $content = $content->write_chunk($bytes);
  $content = $content->write_chunk($bytes => sub {...});

Write dynamic content non-blocking with chunked transfer encoding, the optional drain callback will be executed once
all data has been written. Calling this method without a chunk of data will finalize the L</"headers"> and allow for
dynamic content to be written later. You can write an empty chunk of data at any time to end the stream.

  # Make sure previous chunk of data has been written before continuing
  $content->write_chunk('He' => sub ($content) {
    $content->write_chunk('llo!' => sub ($content) {
      $content->write_chunk('');
    });
  });

=head2 write_sse

  $content = $content->write_sse;
  $content = $content->write_sse($event);
  $content = $content->write_sse($event => sub {...});

Write Server-Sent Event (SSE) non-blocking, the optional drain callback will be executed once all data has been
written. Calling this method without an event will finalize the response headers and allow for events to be written
later. Note that this method is B<EXPERIMENTAL> and may change without warning!

=head1 SEE ALSO

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

=cut