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package RT::Interface::REST;
use strict;
use warnings;
use RT;

use base 'Exporter';
our @EXPORT = qw(expand_list form_parse form_compose vpush vsplit);

sub custom_field_spec {
    my $self    = shift;
    my $capture = shift;

    my $CF_char = '[\sa-z0-9_ :()/-]';
    my $CF_name = $CF_char . '+';
    $CF_name = '(' . $CF_name . ')' if $capture;

    my $new_style = 'CF\.\{'.$CF_name.'\}';
    my $old_style = 'C(?:ustom)?F(?:ield)?-'.$CF_name;

    return '(?i:' . join('|', $new_style, $old_style) . ')';
}

sub field_spec {
    my $self    = shift;
    my $capture = shift;

    my $field = '[a-z][a-z0-9_-]*';
    $field = '(' . $field . ')' if $capture;

    my $custom_field = __PACKAGE__->custom_field_spec($capture);

    return '(?i:' . join('|', $field, $custom_field) . ')';
}

# WARN: this code is duplicated in bin/rt.in,
# change both functions at once
sub expand_list {
    my ($list) = @_;

    my @elts;
    foreach (split /\s*,\s*/, $list) {
        push @elts, /^(\d+)-(\d+)$/? ($1..$2): $_;
    }

    return map $_->[0], # schwartzian transform
        sort {
            defined $a->[1] && defined $b->[1]?
                # both numbers
                $a->[1] <=> $b->[1]
                :!defined $a->[1] && !defined $b->[1]?
                    # both letters
                    $a->[2] cmp $b->[2]
                    # mix, number must be first
                    :defined $a->[1]? -1: 1
        }
        map [ $_, (defined( /^(\d+)$/ )? $1: undef), lc($_) ],
        @elts;
}

# Returns a reference to an array of parsed forms.
sub form_parse {
    my $state = 0;
    my @forms = ();
    my @lines = split /\n/, $_[0];
    my ($c, $o, $k, $e) = ("", [], {}, "");
    my $field = __PACKAGE__->field_spec;

    LINE:
    while (@lines) {
        my $line = shift @lines;

        next LINE if $line eq '';

        if ($line eq '--') {
            # We reached the end of one form. We'll ignore it if it was
            # empty, and store it otherwise, errors and all.
            if ($e || $c || @$o) {
                push @forms, [ $c, $o, $k, $e ];
                $c = ""; $o = []; $k = {}; $e = "";
            }
            $state = 0;
        }
        elsif ($state != -1) {
            if ($state == 0 && $line =~ /^#/) {
                # Read an optional block of comments (only) at the start
                # of the form.
                $state = 1;
                $c = $line;
                while (@lines && $lines[0] =~ /^#/) {
                    $c .= "\n".shift @lines;
                }
                $c .= "\n";
            }
            elsif ($state <= 1 && $line =~ /^($field):(?:\s+(.*))?$/i) {
                # Read a field: value specification.
                my $f  = $1;
                my @v  = ($2);
                $v[0] = '' unless defined $v[0];

                # Read continuation lines, if any.
                while (@lines && ($lines[0] eq '' || $lines[0] =~ /^\s+/)) {
                    push @v, shift @lines;
                }
                pop @v while (@v && $v[-1] eq '');

                # Strip longest common leading indent from text.
                my $ws = ("");
                foreach my $ls (map {/^(\s+)/} @v[1..$#v]) {
                    $ws = $ls if (!$ws || length($ls) < length($ws));
                }
                s/^$ws// foreach @v;

                shift @v while (@v && $v[0] eq '');

                push(@$o, $f) unless exists $k->{$f};
                vpush($k, $f, join("\n", @v));

                $state = 1;
            }
            elsif ($line =~ /^#/) {
                # We've found a syntax error, so we'll reconstruct the
                # form parsed thus far, and add an error marker. (>>)
                $state = -1;
                $e = form_compose([[ "", $o, $k, "" ]]);
                $e.= $line =~ /^>>/ ? "$line\n" : ">> $line\n";
            }
        }
        else {
            # We saw a syntax error earlier, so we'll accumulate the
            # contents of this form until the end.
            $e .= "$line\n";
        }
    }
    push(@forms, [ $c, $o, $k, $e ]) if ($e || $c || @$o);

    foreach my $l (keys %$k) {
        $k->{$l} = vsplit($k->{$l}) if (ref $k->{$l} eq 'ARRAY');
    }

    return \@forms;
}

# Returns text representing a set of forms.
sub form_compose {
    my ($forms) = @_;
    my (@text);

    foreach my $form (@$forms) {
        my ($c, $o, $k, $e) = @$form;
        my $text = "";

        if ($c) {
            $c =~ s/\n*$/\n/;
            $text = "$c\n";
        }
        if ($e) {
            $text .= $e;
        }
        elsif ($o) {
            my (@lines);

            foreach my $key (@$o) {
                my ($line, $sp);
                my @values = (ref $k->{$key} eq 'ARRAY') ?
                               @{ $k->{$key} } :
                                  $k->{$key};

                $sp = " "x(length("$key: "));
                $sp = " "x4 if length($sp) > 16;

                foreach my $v (@values) {
                    $v = '' unless defined $v;
                    if ( $v =~ /\n/) {
                        $v =~ s/^/$sp/gm;
                        $v =~ s/^$sp//;

                        if ($line) {
                            push @lines, "$line\n\n";
                            $line = "";
                        }
                        elsif (@lines && $lines[-1] !~ /\n\n$/) {
                            $lines[-1] .= "\n";
                        }
                        push @lines, "$key: $v\n\n";
                    }
                    elsif ($line &&
                           length($line)+length($v)-rindex($line, "\n") >= 70)
                    {
                        $line .= ",\n$sp$v";
                    }
                    else {
                        $line = $line ? "$line, $v" : "$key: $v";
                    }
                }

                $line = "$key:" unless @values;
                if ($line) {
                    if ($line =~ /\n/) {
                        if (@lines && $lines[-1] !~ /\n\n$/) {
                            $lines[-1] .= "\n";
                        }
                        $line .= "\n";
                    }
                    push @lines, "$line\n";
                }
            }

            $text .= join "", @lines;
        }
        else {
            chomp $text;
        }
        push @text, $text;
    }

    return join "\n--\n\n", @text;
}

# Add a value to a (possibly multi-valued) hash key.
sub vpush {
    my ($hash, $key, $val) = @_;
    my @val = ref $val eq 'ARRAY' ? @$val : $val;

    if (exists $hash->{$key}) {
        unless (ref $hash->{$key} eq 'ARRAY') {
            my @v = $hash->{$key} ne '' ? $hash->{$key} : ();
            $hash->{$key} = \@v;
        }
        push @{ $hash->{$key} }, @val;
    }
    else {
        $hash->{$key} = $val;
    }
}

# "Normalise" a hash key that's known to be multi-valued.
sub vsplit {
    my ($val) = @_;
    my @words;

    foreach my $line (map {split /\n/} (ref $val eq 'ARRAY') ? @$val : ($val||''))
    {
        # XXX: This should become a real parser, ? la Text::ParseWords.
        $line =~ s/^\s+//;
        $line =~ s/\s+$//;
        push @words, split /\s*,\s*/, $line;
    }

    return \@words;
}

RT::Base->_ImportOverlays();

1;

=head1 NAME

  RT::Interface::REST - helper functions for the REST interface.

=head1 SYNOPSIS

  Only the REST should use this module.
