# Copyright (C) 2016-2021 all contributors <meta@public-inbox.org>
# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>

# used for displaying help texts and other non-mail content
package PublicInbox::WwwText;
use strict;
use v5.10.1;
use PublicInbox::Linkify;
use PublicInbox::WwwStream;
use PublicInbox::Hval qw(ascii_html prurl);
use URI::Escape qw(uri_escape_utf8);
use PublicInbox::GzipFilter qw(gzf_maybe);
our $QP_URL = 'https://xapian.org/docs/queryparser.html';
our $WIKI_URL = 'https://en.wikipedia.org/wiki';
my $hl = eval {
	require PublicInbox::HlMod;
	PublicInbox::HlMod->new
};

# /$INBOX/_/text/$KEY/ # KEY may contain slashes
# For now, "help" is the only supported $KEY
sub get_text {
	my ($ctx, $key) = @_;
	my $code = 200;

	$key //= 'help'; # this 302s to _/text/help/

	# get the raw text the same way we get mboxrds
	my $raw = ($key =~ s!/raw\z!!);
	my $have_tslash = ($key =~ s!/\z!!) if !$raw;

	my $txt = '';
	my $hdr = [ 'Content-Type', 'text/plain', 'Content-Length', undef ];
	if (!_default_text($ctx, $key, $hdr, \$txt)) {
		$code = 404;
		$txt = "404 Not Found ($key)\n";
	}
	my $env = $ctx->{env};
	if ($raw) {
		if ($code == 200) {
			my $gzf = gzf_maybe($hdr, $env);
			$txt = $gzf->translate($txt);
			$txt .= $gzf->zflush;
		}
		$hdr->[3] = length($txt);
		return [ $code, $hdr, [ $txt ] ]
	}

	# enforce trailing slash for "wget -r" compatibility
	if (!$have_tslash && $code == 200) {
		my $url = $ctx->{ibx}->base_url($env);
		$url .= "_/text/$key/";

		return [ 302, [ 'Content-Type', 'text/plain',
				'Location', $url ],
			[ "Redirecting to $url\n" ] ];
	}

	# Follow git commit message conventions,
	# first line is the Subject/title
	my ($title) = ($txt =~ /\A([^\n]*)/s);
	$ctx->{-title_html} = ascii_html($title);
	my $nslash = ($key =~ tr!/!/!);
	$ctx->{-upfx} = '../../../' . ('../' x $nslash);
	my $l = PublicInbox::Linkify->new;
	$l->linkify_1($txt);
	if ($hl) {
		$hl->do_hl_text(\$txt);
	} else {
		$txt = ascii_html($txt);
	}
	$txt = '<pre>' . $l->linkify_2($txt) . '</pre>';
	PublicInbox::WwwStream::html_oneshot($ctx, $code, \$txt);
}

sub _srch_prefix ($$) {
	my ($srch, $txt) = @_;
	my $pad = 0;
	my $htxt = '';
	my $help = $srch->help;
	my $i;
	for ($i = 0; $i < @$help; $i += 2) {
		my $pfx = $help->[$i];
		my $n = length($pfx);
		$pad = $n if $n > $pad;
		$htxt .= $pfx . "\0";
		$htxt .= $help->[$i + 1];
		$htxt .= "\f\n";
	}
	$pad += 2;
	my $padding = ' ' x ($pad + 8);
	$htxt =~ s/^/$padding/gms;
	$htxt =~ s/^$padding(\S+)\0/"        $1".
				(' ' x ($pad - length($1)))/egms;
	$htxt =~ s/\f\n/\n/gs;
	$$txt .= $htxt;
	1;
}

sub _colors_help ($$) {
	my ($ctx, $txt) = @_;
	my $ibx = $ctx->{ibx};
	my $env = $ctx->{env};
	my $base_url = $ibx->base_url($env);
	$$txt .= "color customization for $base_url\n";
	$$txt .= <<EOF;

public-inbox provides a stable set of CSS classes for users to
customize colors for highlighting diffs and code.

Users of browsers such as dillo, Firefox, or some browser
extensions may start by downloading the following sample CSS file
to control the colors they see:

	${base_url}userContent.css

CSS sample
----------
```css
EOF
	$$txt .= PublicInbox::UserContent::sample($ibx, $env) . "```\n";
}

# git-config section names are quoted in the config file, so escape them
sub dq_escape ($) {
	my ($name) = @_;
	$name =~ s/\\/\\\\/g;
	$name =~ s/"/\\"/g;
	$name;
}

sub _coderepo_config ($$) {
	my ($ctx, $txt) = @_;
	my $cr = $ctx->{ibx}->{coderepo} // return;
	# note: this doesn't preserve cgitrc layout, since we parse cgitrc
	# and drop the original structure
	$$txt .= "\tcoderepo = $_\n" for @$cr;
	$$txt .= <<'EOF';

; `coderepo' entries allows blob reconstruction via patch emails if
; the inbox is indexed with Xapian.  `@@ <from-range> <to-range> @@'
; line number ranges in `[PATCH]' emails link to /$INBOX_NAME/$OID/s/,
; an HTTP endpoint which reconstructs git blobs via git-apply(1).
EOF
	my $pi_cfg = $ctx->{www}->{pi_cfg};
	for my $cr_name (@$cr) {
		my $urls = $pi_cfg->get_all("coderepo.$cr_name.cgiturl");
		my $path = "/path/to/$cr_name";
		$cr_name = dq_escape($cr_name);

		$$txt .= qq([coderepo "$cr_name"]\n);
		if ($urls && scalar(@$urls)) {
			$$txt .= "\t; ";
			$$txt .= join(" ||\n\t;\t", map {;
				my $dst = $path;
				if ($path !~ m![a-z0-9_/\.\-]!i) {
					$dst = '"'.dq_escape($dst).'"';
				}
				qq(git clone $_ $dst);
			} @$urls);
			$$txt .= "\n";
		}
		$$txt .= "\tdir = $path\n";
		$$txt .= "\tcgiturl = https://example.com/";
		$$txt .= uri_escape_utf8($cr_name, '^A-Za-z0-9\-\._~/')."\n";
	}
}

# n.b. this is a perfect candidate for memoization
sub inbox_config ($$$) {
	my ($ctx, $hdr, $txt) = @_;
	my $ibx = $ctx->{ibx};
	push @$hdr, 'Content-Disposition', 'inline; filename=inbox.config';
	my $name = dq_escape($ibx->{name});
	my $inboxdir = '/path/to/top-level-inbox';
	my $base_url = $ibx->base_url($ctx->{env});
	$$txt .= <<EOS;
; Example public-inbox config snippet for a mirror of
; $base_url
; See public-inbox-config(5) manpage for more details:
; https://public-inbox.org/public-inbox-config.html
[publicinbox "$name"]
	inboxdir = $inboxdir
	; note: public-inbox before v1.2.0 used `mainrepo' instead of
	; `inboxdir', both remain supported after 1.2
	mainrepo = $inboxdir
	url = https://example.com/$name/
	url = http://example.onion/$name/
EOS
	for my $k (qw(address listid infourl watchheader)) {
		defined(my $v = $ibx->{$k}) or next;
		$$txt .= "\t$k = $_\n" for @$v;
	}
	if (my $altid = $ibx->{altid}) {
		my $altid_map = $ibx->altid_map;
		$$txt .= <<EOF;
	; altid DBs may be used to provide numeric article ID lookup from
	; old, pre-existing sources.  You can recreate them via curl(1),
	; gzip(1), and sqlite3(1) as documented:
EOF
		for (sort keys %$altid_map) {
			$$txt .= "\t;\tcurl -d '' $base_url$_.sql.gz | \\\n" .
				"\t;\tgzip -dc | \\\n" .
				"\t;\tsqlite3 $inboxdir/$_.sqlite3\n";
			$$txt .= "\taltid = serial:$_:file=$_.sqlite3\n";
		}
	}

	for my $k (qw(filter newsgroup obfuscate replyto)) {
		defined(my $v = $ibx->{$k}) or next;
		$$txt .= "\t$k = $v\n";
	}
	$$txt .= "\tnntpmirror = $_\n" for (@{$ibx->nntp_url});
	_coderepo_config($ctx, $txt);
	1;
}

# n.b. this is a perfect candidate for memoization
sub extindex_config ($$$) {
	my ($ctx, $hdr, $txt) = @_;
	my $ibx = $ctx->{ibx};
	push @$hdr, 'Content-Disposition', 'inline; filename=extindex.config';
	my $name = dq_escape($ibx->{name});
	my $base_url = $ibx->base_url($ctx->{env});
	$$txt .= <<EOS;
; Example public-inbox config snippet for the external index (extindex) at:
; $base_url
; See public-inbox-config(5)manpage for more details:
; https://public-inbox.org/public-inbox-config.html
[extindex "$name"]
	topdir = /path/to/extindex-topdir
	url = https://example.com/$name/
	url = http://example.onion/$name/
EOS
	for my $k (qw(infourl)) {
		defined(my $v = $ibx->{$k}) or next;
		$$txt .= "\t$k = $v\n";
	}
	_coderepo_config($ctx, $txt);
	1;
}

sub coderepos_raw ($$) {
	my ($ctx, $top_url) = @_;
	my $cr = $ctx->{ibx}->{coderepo} // return ();
	my $cfg = $ctx->{www}->{pi_cfg};
	my @ret;
	for my $cr_name (@$cr) {
		$ret[0] //= <<EOF;
code repositories for project(s) associated with this inbox:
EOF
		my $urls = $cfg->get_all("coderepo.$cr_name.cgiturl");
		if ($urls) {
			for (@$urls) {
				# relative or absolute URL?, prefix relative
				# "foo.git" with appropriate number of "../"
				my $u = m!\A(?:[a-z\+]+:)?//!i ? $_ :
					$top_url.$_;
				$ret[0] .= "\n\t" . prurl($ctx->{env}, $u);
			}
		} else {
			$ret[0] .= qq[\n\t$cr_name.git (no URL configured)];
		}
	}
	@ret; # may be empty, this sub is called as an arg for join()
}

sub _mirror_help ($$) {
	my ($ctx, $txt) = @_;
	my $ibx = $ctx->{ibx};
	my $base_url = $ibx->base_url($ctx->{env});
	chop $base_url; # no trailing slash for "git clone"
	my $dir = (split(m!/!, $base_url))[-1];
	my %seen = ($base_url => 1);
	my $top_url = $base_url;
	$top_url =~ s!/[^/]+\z!/!;
	$$txt .= "public-inbox mirroring instructions\n\n";
	if ($ibx->can('cloneurl')) { # PublicInbox::Inbox
		$$txt .= "This inbox may be cloned and mirrored by anyone:\n";
		my @urls;
		my $max = $ibx->max_git_epoch;
		# TODO: some of these URLs may be too long and we may need to
		# do something like code_footer() above, but these are local
		# admin-defined
		if (defined($max)) { # v2
			for my $i (0..$max) {
				# old epochs my be deleted:
				-d "$ibx->{inboxdir}/git/$i.git" or next;
				my $url = "$base_url/$i";
				$seen{$url} = 1;
				push @urls, "$url $dir/git/$i.git";
			}
			my $nr = scalar(@urls);
			if ($nr > 1) {
				$$txt .= "\n\t";
				$$txt .= "# this inbox consists of $nr epochs:";
				$urls[0] .= " # oldest";
				$urls[-1] .= " # newest";
			}
		} else { # v1
			push @urls, $base_url;
		}
		# FIXME: epoch splits can be different in other repositories,
		# use the "cloneurl" file as-is for now:
		for my $u (@{$ibx->cloneurl}) {
			next if $seen{$u}++;
			push @urls, $u;
		}
		$$txt .= "\n";
		$$txt .= join('', map { "\tgit clone --mirror $_\n" } @urls);
		if (my $addrs = $ibx->{address}) {
			$addrs = join(' ', @$addrs) if ref($addrs) eq 'ARRAY';
			my $v = defined $max ? '-V2' : '-V1';
			$$txt .= <<EOF;

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init $v $ibx->{name} $dir/ $base_url \\
		$addrs
	public-inbox-index $dir
EOF
		}
	} else { # PublicInbox::ExtSearch
		$$txt .= <<EOM;
This is an extindex which is an amalgamation of several public-inboxes.
Each public-inbox needs to be mirrored individually.
EOM
		my $v = $ctx->{www}->{pi_cfg}->{lc('publicInbox.wwwListing')};
		if (($v // '') =~ /\A(?:all|match=domain)\z/) {
			$$txt .= <<EOM;
A list of them is available at $top_url
EOM
		}
	}
	my $cfg_link = "$base_url/_/text/config/raw";
	$$txt .= <<EOF;

Example config snippet for mirrors: $cfg_link
EOF
	if ($ibx->can('nntp_url')) {
		my $nntp = $ibx->nntp_url;
		if (scalar @$nntp) {
			$$txt .= "\n";
			$$txt .= @$nntp == 1 ? 'Newsgroup' : 'Newsgroups are';
			$$txt .= ' available over NNTP:';
			$$txt .= "\n\t" . join("\n\t", @$nntp) . "\n";
		}
	}
	if ($$txt =~ m!\b[^:]+://\w+\.onion/!) {
		$$txt .= <<EOM

note: .onion URLs require Tor: https://www.torproject.org/

EOM
	}
	my $code_url = prurl($ctx->{env}, $PublicInbox::WwwStream::CODE_URL);
	$$txt .= join("\n\n",
		coderepos_raw($ctx, $top_url), # may be empty
		"AGPL code for this site:\n\tgit clone $code_url");
	1;
}

sub _default_text ($$$$) {
	my ($ctx, $key, $hdr, $txt) = @_;
	if ($key eq 'mirror') {
		return _mirror_help($ctx, $txt);
	} elsif ($key eq 'color') {
		return _colors_help($ctx, $txt);
	} elsif ($key eq 'config') {
		return $ctx->{ibx}->can('cloneurl') ?
			inbox_config($ctx, $hdr, $txt) :
			extindex_config($ctx, $hdr, $txt);
	}

	return if $key ne 'help'; # TODO more keys?

	my $ibx = $ctx->{ibx};
	my $base_url = $ibx->base_url($ctx->{env});
	$$txt .= "public-inbox help for $base_url\n";
	$$txt .= <<EOF;

overview
--------

    public-inbox uses Message-ID identifiers in URLs.
    One may look up messages by substituting Message-IDs
    (without the leading '<' or trailing '>') into the URL.
    Forward slash ('/') characters in the Message-IDs
    need to be escaped as "%2F" (without quotes).

    Thus, it is possible to retrieve any message by its
    Message-ID by going to:

	$base_url<Message-ID>/

	(without the '<' or '>')

    Message-IDs are described at:

	$WIKI_URL/Message-ID

EOF

	# n.b. we use the Xapian DB for any regeneratable,
	# order-of-arrival-independent data.
	my $srch = $ibx->isrch;
	if ($srch) {
		$$txt .= <<EOF;
search
------

    This public-inbox has search functionality provided by Xapian.

    It supports typical AND, OR, NOT, '+', '-' queries present
    in other search engines.

    We also support search prefixes to limit the scope of the
    search to certain fields.

    Prefixes supported in this installation include:

EOF
		_srch_prefix($srch, $txt);

		$$txt .= <<EOF;

    Most prefixes are probabilistic, meaning they support stemming
    and wildcards ('*').  Ranges (such as 'd:') and boolean prefixes
    do not support stemming or wildcards.
    The upstream Xapian query parser documentation fully explains
    the query syntax:

	$QP_URL

EOF
	} # $srch
	my $over = $ibx->over;
	if ($over) {
		$$txt .= <<EOF;
message threading
-----------------

    Message threading is enabled for this public-inbox,
    additional endpoints for message threads are available:

    * $base_url<Message-ID>/T/#u

      Loads the thread belonging to the given <Message-ID>
      in flat chronological order.  The "#u" anchor
      focuses the browser on the given <Message-ID>.

    * $base_url<Message-ID>/t/#u

      Loads the thread belonging to the given <Message-ID>
      in threaded order with nesting.  For deep threads,
      this requires a wide display or horizontal scrolling.

    Both of these HTML endpoints are suitable for offline reading
    using the thread overview at the bottom of each page.

    Users of feed readers may follow a particular thread using:

    * $base_url<Message-ID>/t.atom

      Which loads the thread in Atom Syndication Standard
      described at Wikipedia and RFC4287:

	$WIKI_URL/Atom_(standard)
	https://tools.ietf.org/html/rfc4287

      Atom Threading Extensions (RFC4685) is supported:

	https://tools.ietf.org/html/rfc4685

    Finally, the gzipped mbox for a thread is available for
    downloading and importing into your favorite mail client:

    * $base_url<Message-ID>/t.mbox.gz

    We use the mboxrd variant of the mbox format described
    at:

	$WIKI_URL/Mbox

EOF
	} # $over

	$$txt .= <<EOF;
contact
-------

    This help text is maintained by public-inbox developers
    reachable via plain-text email at: meta\@public-inbox.org
    Their inbox is archived at: https://public-inbox.org/meta/

EOF
	# TODO: support admin contact info in ~/.public-inbox/config
	1;
}

1;