# Copyright (C) 2021 all contributors <meta@public-inbox.org>
# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>

# common reader code for IMAP and NNTP (and maybe JMAP)
package PublicInbox::NetReader;
use strict;
use v5.10.1;
use parent qw(Exporter);

# TODO: trim this down, this is huge
our @EXPORT = qw(uri_new uri_scheme uri_section
		mic_for nn_new nn_for
		imap_url nntp_url);

# avoid exposing deprecated "snews" to users.
my %SCHEME_MAP = ('snews' => 'nntps');

sub uri_scheme ($) {
	my ($uri) = @_;
	my $scheme = $uri->scheme;
	$SCHEME_MAP{$scheme} // $scheme;
}

# returns the git config section name, e.g [imap "imaps://user@example.com"]
# without the mailbox, so we can share connections between different inboxes
sub uri_section ($) {
	my ($uri) = @_;
	uri_scheme($uri) . '://' . $uri->authority;
}

sub auth_anon_cb { '' }; # for Mail::IMAPClient::Authcallback

sub mic_for { # mic = Mail::IMAPClient
	my ($self, $url, $mic_args) = @_;
	require PublicInbox::URIimap;
	my $uri = PublicInbox::URIimap->new($url);
	require PublicInbox::GitCredential;
	my $cred = bless {
		url => $url,
		protocol => $uri->scheme,
		host => $uri->host,
		username => $uri->user,
		password => $uri->password,
	}, 'PublicInbox::GitCredential';
	my $common = $mic_args->{uri_section($uri)} // {};
	# IMAPClient and Net::Netrc both mishandles `0', so we pass `127.0.0.1'
	my $host = $cred->{host};
	$host = '127.0.0.1' if $host eq '0';
	my $mic_arg = {
		Port => $uri->port,
		Server => $host,
		Ssl => $uri->scheme eq 'imaps',
		Keepalive => 1, # SO_KEEPALIVE
		%$common, # may set Starttls, Compress, Debug ....
	};
	require PublicInbox::IMAPClient;
	my $mic = PublicInbox::IMAPClient->new(%$mic_arg) or
		die "E: <$url> new: $@\n";

	# default to using STARTTLS if it's available, but allow
	# it to be disabled since I usually connect to localhost
	if (!$mic_arg->{Ssl} && !defined($mic_arg->{Starttls}) &&
			$mic->has_capability('STARTTLS') &&
			$mic->can('starttls')) {
		$mic->starttls or die "E: <$url> STARTTLS: $@\n";
	}

	# do we even need credentials?
	if (!defined($cred->{username}) &&
			$mic->has_capability('AUTH=ANONYMOUS')) {
		$cred = undef;
	}
	if ($cred) {
		$cred->check_netrc unless defined $cred->{password};
		$cred->fill; # may prompt user here
		$mic->User($mic_arg->{User} = $cred->{username});
		$mic->Password($mic_arg->{Password} = $cred->{password});
	} else { # AUTH=ANONYMOUS
		$mic->Authmechanism($mic_arg->{Authmechanism} = 'ANONYMOUS');
		$mic->Authcallback($mic_arg->{Authcallback} = \&auth_anon_cb);
	}
	if ($mic->login && $mic->IsAuthenticated) {
		# success! keep IMAPClient->new arg in case we get disconnected
		$self->{mic_arg}->{uri_section($uri)} = $mic_arg;
	} else {
		warn "E: <$url> LOGIN: $@\n";
		$mic = undef;
	}
	$cred->run($mic ? 'approve' : 'reject') if $cred;
	$mic;
}

sub uri_new {
	my ($url) = @_;
	require URI;

	# URI::snews exists, URI::nntps does not, so use URI::snews
	$url =~ s!\Anntps://!snews://!i;
	URI->new($url);
}

# Net::NNTP doesn't support CAPABILITIES, yet
sub try_starttls ($) {
	my ($host) = @_;
	return if $host =~ /\.onion\z/s;
	return if $host =~ /\A127\.[0-9]+\.[0-9]+\.[0-9]+\z/s;
	return if $host eq '::1';
	1;
}

sub nn_new ($$$) {
	my ($nn_arg, $nntp_opt, $url) = @_;
	my $nn = Net::NNTP->new(%$nn_arg) or die "E: <$url> new: $!\n";

	# default to using STARTTLS if it's available, but allow
	# it to be disabled for localhost/VPN users
	if (!$nn_arg->{SSL} && $nn->can('starttls')) {
		if (!defined($nntp_opt->{starttls}) &&
				try_starttls($nn_arg->{Host})) {
			# soft fail by default
			$nn->starttls or warn <<"";
W: <$url> STARTTLS tried and failed (not requested)

		} elsif ($nntp_opt->{starttls}) {
			# hard fail if explicitly configured
			$nn->starttls or die <<"";
E: <$url> STARTTLS requested and failed

		}
	} elsif ($nntp_opt->{starttls}) {
		$nn->can('starttls') or
			die "E: <$url> Net::NNTP too old for STARTTLS\n";
		$nn->starttls or die <<"";
E: <$url> STARTTLS requested and failed

	}
	$nn;
}

sub nn_for ($$$) { # nn = Net::NNTP
	my ($self, $url, $nn_args) = @_;
	my $uri = uri_new($url);
	my $sec = uri_section($uri);
	my $nntp_opt = $self->{nntp_opt}->{$sec} //= {};
	my $host = $uri->host;
	# Net::NNTP and Net::Netrc both mishandle `0', so we pass `127.0.0.1'
	$host = '127.0.0.1' if $host eq '0';
	my $cred;
	my ($u, $p);
	if (defined(my $ui = $uri->userinfo)) {
		require PublicInbox::GitCredential;
		$cred = bless {
			url => $sec,
			protocol => uri_scheme($uri),
			host => $host,
		}, 'PublicInbox::GitCredential';
		($u, $p) = split(/:/, $ui, 2);
		($cred->{username}, $cred->{password}) = ($u, $p);
		$cred->check_netrc unless defined $p;
	}
	my $common = $nn_args->{$sec} // {};
	my $nn_arg = {
		Port => $uri->port,
		Host => $host,
		SSL => $uri->secure, # snews == nntps
		%$common, # may Debug ....
	};
	my $nn = nn_new($nn_arg, $nntp_opt, $url);

	if ($cred) {
		$cred->fill; # may prompt user here
		if ($nn->authinfo($u, $p)) {
			push @{$nntp_opt->{-postconn}}, [ 'authinfo', $u, $p ];
		} else {
			warn "E: <$url> AUTHINFO $u XXXX failed\n";
			$nn = undef;
		}
	}

	if ($nntp_opt->{compress}) {
		# https://rt.cpan.org/Ticket/Display.html?id=129967
		if ($nn->can('compress')) {
			if ($nn->compress) {
				push @{$nntp_opt->{-postconn}}, [ 'compress' ];
			} else {
				warn "W: <$url> COMPRESS failed\n";
			}
		} else {
			delete $nntp_opt->{compress};
			warn <<"";
W: <$url> COMPRESS not supported by Net::NNTP
W: see PI-LINK-3ba330c2c8b2134b2884b85642df14aa2a76622b for updates

		}
	}

	$self->{nn_arg}->{$sec} = $nn_arg;
	$cred->run($nn ? 'approve' : 'reject') if $cred;
	$nn;
}

sub imap_url {
	my ($url) = @_;
	require PublicInbox::URIimap;
	my $uri = PublicInbox::URIimap->new($url);
	$uri ? $uri->canonical->as_string : undef;
}

my %IS_NNTP = (news => 1, snews => 1, nntp => 1);
sub nntp_url {
	my ($url) = @_;
	my $uri = uri_new($url);
	return unless $uri && $IS_NNTP{$uri->scheme} && $uri->group;
	$url = $uri->canonical->as_string;
	# nntps is IANA registered, snews is deprecated
	$url =~ s!\Asnews://!nntps://!;
	$url;
}

1;