--- /dev/null
+# Copyright (C) 2020-2021 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+
+# -h/--help support for lei
+package PublicInbox::LeiHelp;
+use strict;
+use v5.10.1;
+use Text::Wrap qw(wrap);
+
+my %NOHELP = map { $_ => 1 } qw(mua-cmd mfolder);
+
+sub call {
+ my ($self, $errmsg, $CMD, $OPTDESC) = @_;
+ my $cmd = $self->{cmd} // 'COMMAND';
+ my @info = @{$CMD->{$cmd} // [ '...', '...' ]};
+ my @top = ($cmd, shift(@info) // ());
+ my $cmd_desc = shift(@info);
+ $cmd_desc = $cmd_desc->($self) if ref($cmd_desc) eq 'CODE';
+ $cmd_desc =~ s/default: /default:\xa0/;
+ my @opt_desc;
+ my $lpad = 2;
+ for my $sw (grep { !ref } @info) { # ("prio=s", "z", $GLP_PASS)
+ my $desc = $OPTDESC->{"$cmd\t$sw"} // $OPTDESC->{$sw} // next;
+ my $arg_vals = '';
+ ($arg_vals, $desc) = @$desc if ref($desc) eq 'ARRAY';
+
+ # lower-case is a keyword (e.g. `content', `oid'),
+ # ALL_CAPS is a string description (e.g. `PATH')
+ if ($desc !~ /default/ && $arg_vals =~ /\b([a-z]+)[,\|]/) {
+ $desc .= " (default:\xa0`$1')";
+ } else {
+ $desc =~ s/default: /default:\xa0/;
+ }
+ my (@vals, @s, @l);
+ my $x = $sw;
+ if ($x =~ s/!\z//) { # solve! => --no-solve
+ $x =~ s/(\A|\|)/$1no-/g
+ } elsif ($x =~ s/\+\z//) { # verbose|v+
+ } elsif ($x =~ s/:.+//) { # optional args: $x = "mid:s"
+ @vals = (' [', undef, ']');
+ } elsif ($x =~ s/=.+//) { # required arg: $x = "type=s"
+ @vals = (' ', undef);
+ } # else: no args $x = 'thread|t'
+
+ # we support underscore options from public-inbox-* commands;
+ # but they've never been documented and will likely go away.
+ # $x = help|h
+ for (grep { !/_/ && !$NOHELP{$_} } split(/\|/, $x)) {
+ length($_) > 1 ? push(@l, "--$_") : push(@s, "-$_");
+ }
+ if (!scalar(@vals)) { # no args 'thread|t'
+ } elsif ($arg_vals =~ s/\A([A-Z_]+)\b//) { # "NAME"
+ $vals[1] = $1;
+ } else {
+ $vals[1] = uc(substr($l[0], 2)); # "--type" => "TYPE"
+ }
+ if ($arg_vals =~ /([,\|])/) {
+ my $sep = $1;
+ my @allow = split(/\Q$sep\E/, $arg_vals);
+ my $must = $sep eq '|' ? 'Must' : 'Can';
+ @allow = map { length $_ ? "`$_'" : () } @allow;
+ my $last = pop @allow;
+ $desc .= "\n$must be one of: " .
+ join(', ', @allow) . " or $last";
+ }
+ my $lhs = join(', ', @s, @l) . join('', @vals);
+ if ($x =~ /\|\z/) { # "stdin|" or "clear|"
+ $lhs =~ s/\A--/- , --/;
+ } else {
+ $lhs =~ s/\A--/ --/; # pad if no short options
+ }
+ $lpad = length($lhs) if length($lhs) > $lpad;
+ push @opt_desc, $lhs, $desc;
+ }
+ my $msg = $errmsg ? "E: $errmsg\n" : '';
+ $msg .= <<EOF;
+usage: lei @top
+$cmd_desc
+
+EOF
+ $lpad += 2;
+ local $Text::Wrap::columns = 78 - $lpad;
+ # local $Text::Wrap::break = ; # don't break on nbsp (\xa0)
+ my $padding = ' ' x ($lpad + 2);
+ while (my ($lhs, $rhs) = splice(@opt_desc, 0, 2)) {
+ $msg .= ' '.pack("A$lpad", $lhs);
+ $rhs = wrap('', '', $rhs);
+ $rhs =~ s/\n/\n$padding/sg; # LHS pad continuation lines
+ $msg .= $rhs;
+ $msg .= "\n";
+ }
+ my $fd = $errmsg ? 2 : 1;
+ $self->start_pager if -t $self->{$fd};
+ $msg =~ s/\xa0/ /gs; # convert NBSP to SP
+ print { $self->{$fd} } $msg;
+ $self->x_it($errmsg ? (1 << 8) : 0); # stderr => failure
+ undef;
+}
+
+1;