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# Configuration parser for Sourceyard                -*- perl -*-
# Copyright (C) 2017 Sergey Poznyakoff <gray@gnu.org>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

package Config::Tree;

use strict;
use warnings;
use Carp;
use Config::Tree::Locus;
use Config::Tree::Node qw(:sort);
use Config::Tree::Node::Section;
use Config::Tree::Node::Value;
use Data::Dumper;

require Exporter;
our @ISA = qw(Exporter);
our %EXPORT_TAGS = ( 'sort' => [ qw(NO_SORT SORT_NATURAL SORT_PATH) ] );
our @EXPORT_OK = qw(NO_SORT SORT_NATURAL SORT_PATH);
    
our $VERSION = "1.00";

=head1 NAME

Config::Tree - generalized configuration file parser

=head1 SYNOPSIS

    my $cfg = new Config::Tree($filename, %opts);
    $cfg->parse() or die;

    if ($cfg->is_set('core', 'variable')) {
       ...
    }

    my $x = $cfg->get('file', 'locking');

    $cfg->set('file', 'locking', 'true');

    $cfg->unset('file', 'locking');

=head1 DESCRIPTION

Configuration file handling. Features:

=over 4

=item 1
    
Handles I<git>-format configuration files.    

=item 2

Table-driven syntax checking and validation.

=item 3

Optional caching facility allows for faster loading. This is especially
useful for big configurations.

=item 4

Built-in B<lint> facility.

=item 5

Location tracking.

=item 6

Dump facility. The parsed configuration can be output to the given file
handler in a standardized form.

=item 7

Both random access and iteration over all settings is possible.

=back

=head1 METHODS    
    
=head2 $cfg = new Config::Tree($filename, %opts);

Creates new configuration object for file B<$filename>.  Valid
options are:

=over 4

=item B<debug> => I<NUM>

Sets debug verbosity level.    

=item B<ci> => B<0> | B<1>

If B<1>, enables case-insensitive keyword matching.  Default is B<0>,
i.e. the keywords are case-sensitive.    

=item B<parameters> => \%hash

Defines the syntax table.  See below for a description of B<%hash>.
    
=back    

=head3 Syntax hash

The hash passed via the B<parameters> keyword defines the keywords and
sections allowed within a configuration file.  In a simplest case, a
keyword is described as

    name => 1

This means that B<name> is a valid keyword, but does not imply anything
more about it or its value.  A more complex declaration is possible, in
which the value is a hash reference, containing one or more of the following
keywords:

=over 4

=item mandatory => 0 | 1

Whether or not this setting is mandatory.

=item default => I<VALUE>

Default value for the setting. It is assigned when entire configuration file
has been parsed, if that particular setting did not occur in it. If I<VALUE>
is a code, it will be invoked as a method each time the value is accessed.

Default values must be pure Perl values (not the values that should appear
in the configuration file). They are not processed using the B<check>
callbacks.    
    
=item array => 0 | 1

If B<1>, the value of the setting is an array.  Each subsequent occurrence
of the statement appends its value to the end of the array.

=item re => I<regexp>

Defines a regular expression to which must be matched by the value of the
setting, otherwise a syntax error will be reported.

=item select => I<coderef>

Points to a function to be called to decide whether to apply this hash to
a particular configuration setting.  The function is called as

    $self->$coderef($node, @path)

where $node is the B<Config::Tree::Node::Value> object (use
B<$vref-E<gt>value>, to obtain the actual value), and B<@path> is its patname.
    
=item check => I<coderef>

Defines a code which will be called after parsing the statement in order to
verify its value.  The I<coderef> is called as

    $self->$coderef($valref, $prev_value, $locus)

where B<$valref> is a reference to its value, and B<$prev_value> is the
value of the previous instance of this setting.  The function must return non-0
if the value is OK for that setting.  In that case, it is allowed to modify
the value, referenced by B<$valref>.  If the value is erroneous, the function
must issue an appropriate error message using B<$cfg-E<gt>error>, and return 0.
    
=back    

To define a section, use the B<section> keyword, e.g.:

    core => {
        section => {
            pidfile => {
               mandatory => 1
            },
            verbose => {
               re => qr/^(?:on|off)/i
            }
        }
    }

This says that a section B<[core]> can have two variables: B<pidfile>, which
is mandatory, and B<verbose>, whose value must be B<on>, or B<off> (case-    
insensitive).

To allow for arbitrary keywords, use B<*>.  For example, the following
declares the B<[code]> section, which must have the B<pidfile> setting
and is allowed to have any other settings as well.    
 
    code => {
       section => {
           pidfile => { mandatory => 1 },
           '*' => 1
       }
    }

Everything said above applies to the B<'*'> as well.  E.g. the following
example declares the B<[code]> section, which must have the B<pidfile>
setting and is allowed to have I<subsections> with arbitrary settings.

    code => {
       section => {
           pidfile = { mandatory => 1 },
           '*' => {
               section => {
                   '*' => 1
               }
           }
       }
    }

The special entry

    '*' => '*'

means "any settings and any subsections".

=cut

sub new {
    my $class = shift;
    local %_ = @_;
    my $self = bless { _order => 0 }, $class;
    my $v;
    my $err;

    $self->{_debug} = delete $_{debug} || 0;
    $self->{_ci} = delete $_{ci} || 0;

    if (defined($v = delete $_{parameters})) {
	if (ref($v) eq 'HASH') {
	    $self->{_parameters} = $v;
	} else {
	    carp "parameters must refer to a HASH";
	    ++$err;
	}
    }

    if (keys(%_)) {
	foreach my $k (keys %_) {
	    carp "unknown parameter $k"
	}
	++$err;
    }
    croak "can't create configuration instance" if $err;
    $self->reset;
    return $self;
}

sub reset {
    my $self = shift;
    $self->{_error_count} = 0;
    delete $self->{_tree};
}

=head2 $cfg->error($message)

=head2 $cfg->error($message, locus => $loc)

Prints the B<$message> on STDERR.  If B<locus> is given, its value must
be a reference to a valid B<Config::Tree::Locus>(3) object.  In that
case, the object will be formatted first, then followed by a ": " and the
B<$message>.    
    
=cut
    
sub error {
    my $self = shift;
    my $err = shift;
    local %_ = @_;
    print STDERR "$_{locus}: " if $_{locus};
    print STDERR "$err\n";
}

=head2 $cfg->debug($lev, @msg)

If B<$lev> is greater than or equal to the B<debug> value used when
creating B<$cfg>, outputs on standard error the strings from @msg,
separating them with a single space character.

Otherwise, does nothing.    

=cut    

sub debug {
    my $self = shift;
    my $lev = shift;
    return unless $self->{_debug} >= $lev;
    $self->error("DEBUG: " . join(' ', @_));
}

sub _fixup {
    my ($self, $section, $params, @path) = @_;

    while (my ($k, $d) = each %{$params}) {
	next unless ref($d) eq 'HASH';

	if (exists($d->{default}) && !$section->has_key($k)) {
	    my $n;
	    my $dfl = ref($d->{default}) eq 'CODE'
		        ? sub { $self->${ \ $d->{default} } }
	                : $d->{default};
	    if (exists($d->{section})) {
		$n = new Config::Tree::Node::Section(
		               default => 1,
		               subtree => $dfl
		     );
	    } else {
		$n = new Config::Tree::Node::Value(
		               default => 1,
		               value => $dfl
		     );
	    }
	    $section->subtree($k => $n);
	}
		
	if (exists($d->{section})) {
	    if ($k eq '*') {
		if (keys(%{$section->subtree})) {
		    while (my ($name, $vref) = each %{$section->subtree}) {
			if (my $sel = $d->{select}) {
			    if ($self->$sel($vref, @path, $name)) {
				next;
			    }
			} elsif ($vref->is_section) {
			    $self->_fixup($vref, $d->{section}, @path, $name);
			}
		    }
		} else {
		    my $node = new Config::Tree::Node::Section;
		    $self->_fixup($node, $d->{section}, @path, $k);
		    if ($node->keys > 0) {
			# If the newly created node contains any subnodes
			# after fixup, they were created because syntax
			# contained mandatory variables with default values.
			# Treat sections containing such variables as
			# mandatory and report them.
			my %h;
			foreach my $p (map {
			                   pop @{$_->[0]};
					   join(' ', (@path, $k, @{$_->[0]}))
				       } $node->flatten(sort => SORT_PATH)) {
			    unless ($h{$p}) {
				$self->error("no section matches mandatory [$p]");
				$self->{_error_count}++;
				$h{$p} = 1;
			    }
			}
		    }
		}
	    } else {
		my $node;
		
		unless ($node = $section->subtree($k)) {
		    $node = new Config::Tree::Node::Section;
		}
		if ((!exists($d->{select})
		     || $self->${ \ $d->{select} }($node, @path, $k))) {
		    $self->_fixup($node, $d->{section}, @path, $k);
		}
		if ($node->keys > 0) {
		    $section->subtree($k => $node);
		}
	    }
	}

	if ($d->{mandatory} && !$section->has_key($k)) {
	    $self->error(exists($d->{section})
			     ? "mandatory section ["
			        . join(' ', @path, $k)
				. "] not present"
		             : "mandatory variable \""
			        . join('.', @path, $k)
			        . "\" not set",
			 locus => $section->locus);
 	    $self->{_error_count}++;
	}	    
    }
}

=head2 $cfg->parse(...)

Parses the configuration file and stores the data in the object.  Returns
true on success and false on failure.  Eventual errors in the configuration
are reported using B<error>.

=cut

sub parse {
    my ($self) = @_;
    croak "call to abstract method"
}

sub getnode {
    my $self = shift;
    
    my $node = $self->{_tree} or return undef;
    for (@_) {
	$node = $node->subtree($self->{_ci} ? lc($_) : $_)
	    or return undef;
    }
    return $node;
}

=head2 $var = $cfg->get(@path);

Returns the B<Config::Tree::Node::Value>(3) corresponding to the
configuration variable represented by its I<path>, or B<undef> if the
variable is not set.  The path is a list of configuration variables leading
to the value in question.  For example, the following statement:

    pidfile = /var/run/x.pid

has the path

    ( 'pidfile' )

The path of the B<pidfile> statement in section B<core>, e.g.:

    [core]
        pidfile = /var/run/x.pid

is

    ( 'core', 'pidfile' )

Similarly, the path of the B<file> setting in the following configuration
file:    

    [item foo]
        file = bar
    
is
    ( 'item', 'foo', 'bar' )

=cut    

sub get {
    my $self = shift;
    croak "no variable to get" unless @_;
    my $node = $self->getnode(@_) or return undef;
    my $value = $node->value;
    if (ref($value) eq 'ARRAY') {
	return wantarray ? @$value : $value;
    } elsif (ref($value) eq 'HASH') {
	return wantarray ? %$value : $value;
    }
    return $value;
}

=head2 $cfg->is_set(@path)

Returns true if the configuration variable addressed by B<@path> is
set.    
    
=cut

sub is_set {
    my $self = shift;
    return defined $self->getnode(@_);
}

=head2 $cfg->is_section(@path)

Returns true if the configuration section addressed by B<@path> is
set.

=cut

sub is_section {
    my $self = shift;
    my $node = $self->getnode(@_);
    return defined($node) && $node->is_section;
}

=head2 $cfg->is_variable(@path)

Returns true if the configuration setting addressed by B<@path>
is set and is a variable.

=cut

sub is_variable {
    my $self = shift;
    my $node = $self->getnode(@_);
    return defined($node) && $node->is_value;
}

sub tree {
    my $self = shift;
    return $self->{_tree} //= new Config::Tree::Node::Section(locus => new Config::Tree::Locus);
}

sub _get_section_synt {
    my ($self, $kw, $name) = @_;

    if (defined($kw)) {
	if (ref($kw) eq 'HASH') {
	    my $synt;
	    if (exists($kw->{$name})) {
		$synt = $kw->{$name};
	    } elsif (exists($kw->{'*'})) {
		$synt = $kw->{'*'};
		if ($synt eq '*') {
		    return { '*' => '*' };
		}
	    } 
	    if (defined($synt)
		&& ref($synt) eq 'HASH'
		&& exists($synt->{section})) {
		return $synt->{section};
	    }
	}
    }
    return
}

=head2 add_node($path, $node)

=cut

sub add_node {
    my ($self, $path, $node) = @_;

    unless (ref($path) eq 'ARRAY') {
	$path = [ split(/\./, $path) ]
    }

    my $kw = $self->{_parameters} // { '*' => '*' };
    my $tree = $self->tree;
    my $pn = $#{$path};
    my $name;
    my $locus = $node->locus;
    for (my $i = 0; $i < $pn; $i++) {
	$name = ${$path}[$i];
	
	unless ($tree->is_section) {
	    $self->error(join('.', @{$path}[0..$i]) . ": not a section");
	    $self->{_error_count}++;
	    return;
	}

	$kw = $self->_get_section_synt($kw, $name);
	unless ($kw) {
	    $self->error(join('.', @{$path}[0..$i]) . ": unknown section");
	    $self->{_error_count}++;
	    return;
	}

	if (my $subtree = $tree->subtree($name)) {
	    $tree = $subtree;
	} else {
	    $tree = $tree->subtree(
		$name => new Config::Tree::Node::Section(
		    order => $self->{_order}++,
		    locus => $locus->clone)
		);
	}
    }

    $name = ${$path}[-1];

    my $x = $kw->{$name} // $kw->{'*'};
    if (!defined($x)) {
	$self->error("keyword \"$name\" is unknown", locus => $locus);
	$self->{_error_count}++;
	return;
    }

    if ($node->is_section) {
	if ($tree->has_key($name)) {
	    $tree->locus->add_locus($locus);
	    $tree->subtree($name)->merge($node);
	} else {
	    $tree->subtree($name => $node);
	}
	return $node;
    }

    my $v = $node->value;

    if (ref($x) eq 'HASH') {
	if (exists($x->{section})) {
	    $self->error('"'.join('.', @{$path})."\" must be a section",
			 locus => $locus);
	    $self->{_error_count}++;
	    return;
	}

	my $errstr;
	my $prev_val;
	if ($tree->has_key($name)) {
	    # FIXME: is_value?
	    $prev_val = $tree->subtree($name)->value;
	}
	if (exists($x->{re})) {
	    if ($v !~ /$x->{re}/) {
		$self->error("invalid value for $name",
			     locus => $locus);
		$self->{_error_count}++;
		return;
	    }
	}

	if (my $ck = $x->{check}) {
	    unless ($self->$ck(\$v, $prev_val, $locus)) {
		$self->{_error_count}++;
		return;
	    }
	}

	if ($x->{array}) {
	    if (!defined($prev_val)) {
		$v = [ $v ];
	    } else {
		$v = [ @{$prev_val}, $v ];
	    }
	}
    }

    $tree->locus->add_locus($locus->clone);

    my $newnode;
    if ($newnode = $tree->subtree($name)) {
	$newnode->locus->add_locus($locus);
    } else {
	$newnode = $tree->subtree($name => $node);
    }
    $newnode->order($self->{order}++);
    $newnode->value($v);
    return $newnode;
}

sub add_value {
    my ($self, $path, $value, $locus) = @_;
    $self->add_node($path, new Config::Tree::Node::Value(value => $value,
							 locus => $locus));
}

sub commit {
    my ($self) = @_;
    # FIXME
    $self->_fixup($self->tree, $self->{_parameters})
	if exists $self->{_parameters};
    return $self->{_error_count} == 0;
}

=head2 $cfg->set(@path, $value)

Sets the configuration variable B<@path> to B<$value>.    

=cut

sub set {
    my $self = shift;
    my $node = $self->tree;
   
    while ($#_ > 1) {
	croak "not a section" unless $node->is_section; 
	my $arg = shift;
	if (my $n = $node->subtree($arg)) {
	    $node = $n;
	} else {
	    $node = $node->subtree(
		         $arg => new Config::Tree::Node::Section
		    );
	}
    }
    
    my $v = $node->subtree($_[0]) ||
	    $node->subtree($_[0] => new Config::Tree::Node::Value(
			              order => $self->{_order}++
			            ));
			   
    $v->value($_[1]);
    $v->default(0);
    return $v;
}

=head2 cfg->unset(@path)

Unsets the configuration variable.
    
=cut

sub unset {
    my $self = shift;

    my $node = $self->{_tree} or return;
    my @path;
    
    for (@_) {
	return unless $node->is_section && $node->has_key($_);
	push @path, [ $node, $_ ];
	$node = $node->subtree($_);
    }

    while (1) {
	my $loc = pop @path;
	$loc->[0]->delete($loc->[1]);
	last unless ($loc->[0]->keys == 0);
    }
}    

=head2 @array = $cfg->names_of(@path)

If B<@path> refers to an existing configuration section, returns a list
of names of variables and subsections defined within that section.  E.g.,
if you have

    [item foo]
       x = 1
    [item bar]
       x = 1
    [item baz]
       y = 2

the call

    $cfg->names_of('item')

will return

    ( 'foo', 'bar', 'baz' )
    
=cut    

sub names_of {
    my $self = shift;
    my $node = $self->getnode(@_);
    return () unless defined($node) && $node->is_section;
    return $node->keys;
}

=head2 @array = $cfg->flatten()

=head2 @array = $cfg->flatten(sort => $sort)    

Returns a I<flattened> representation of the configuration, as a
list of pairs B<[ $path, $value ]>, where B<$path> is a reference
to the variable pathname, and B<$value> is a
B<Config::Tree::Node::Value> object.

The I<$sort> argument controls the ordering of the entries in the returned
B<@array>.  It is either a code reference suitable to pass to the Perl B<sort>
function, or one of the following constants:

=over 4

=item NO_SORT

Don't sort the array.  Statements will be placed in an apparently random
order.

=item SORT_NATURAL

Preserve relative positions of the statements.  Entries in the array will
be in the same order as they appeared in the configuration file.  This is
the default.

=item SORT_PATH

Sort by pathname.

=back

These constants are not exported by default.  You can either import the
ones you need, or use the B<:sort> keyword to import them all, e.g.:

    use Config::Tree qw(:sort);
    @array = $cfg->flatten(sort => SORT_PATH);
    
=cut

sub flatten {
    my $self = shift;
    $self->tree->flatten(@_);
}       

=head2 $h = $cfg->as_hash

=head2 $h = $cfg->as_hash($map)    

Returns parse tree converted to a hash reference. If B<$map> is supplied,
it must be a reference to a function. For each I<$key>/I<$value>
pair, this function will be called as:

    ($newkey, $newvalue) = &{$map}($what, $key, $value)

where B<$what> is C<section> or C<value>, depending on the type of the
hash entry being processed. Upon successful return, B<$newvalue> will be
inserted in the hash slot for the key B<$newkey>.

If B<$what> is C<section>, B<$value> is always a reference to an empty
hash (since the parse tree is traversed in pre-order fashion). In that
case, the B<$map> function is supposed to do whatever initialization that
is necessary for the new subtree and return as B<$newvalue> either B<$value>
itself, or a reference to a hash available inside the B<$value>. For
example:

    sub map {
        my ($what, $name, $val) = @_;
        if ($name eq 'section') {
            $val->{section} = {};
            $val = $val->{section};
        }
        ($name, $val);
    }
    
=cut

sub as_hash {
    my $self = shift;
    my $map = shift // sub { shift; @_ };
    my $hroot = {};
    my @ar;
    
    push @ar, [ '', $self->tree, $hroot ];
    while (my $elt = shift @ar) {
	if ($elt->[1]->is_section) {
	    my $hr0 = {};
	    my ($name, $hr) = &{$map}('section', $elt->[0], $hr0);
	    $elt->[2]{$name} = $hr0;
	    while (my ($kw, $val) = each %{$elt->[1]->subtree}) {
		push @ar, [ $kw, $val, $hr ];
	    }
	} else {
	    my ($name, $value) = &{$map}('value', $elt->[0], $elt->[1]->value);
	    $elt->[2]{$name} = $value;
	}
    }
    return $hroot->{''};
}

sub __lint {
    my ($self, $syntax, $node, @path) = @_;

    $syntax = {} unless ref($syntax) eq 'HASH';
    if (exists($syntax->{section})) {
	return unless $node->is_section;
    } else {
	return if $node->is_section;
    }

    if (exists($syntax->{select}) &&
	!$self->${ \ $syntax->{select} }($node, @path)) {
	return;
    }

    if ($node->is_section) {
	$self->_lint($syntax->{section}, $node, @path);
    } else {
	my $val = $node->value;
	my %opts = ( locus => $node->locus );
		     
	if (ref($val) eq 'ARRAY') {
	    if ($syntax->{array}) {
		my @ar;
		foreach my $v (@$val) {
		    if (exists($syntax->{re})) {
			if ($v !~ /$syntax->{re}/) {
			    $self->error("invalid value for $path[-1]", %opts);
			    $self->{_error_count}++;
			    next;
			}
		    }
		    if (my $ck = $syntax->{check}) {
			unless ($self->$ck(\$v, @ar ? $ar[-1] : undef,
					   $node->locus)) { 
			    $self->{_error_count}++;
			    next;
			}
		    }
		    push @ar, $v;
		}
		$node->value(\@ar);
		return;
	    } else {
		$val = pop(@$val);
	    }
	}
	
	if (exists($syntax->{re})) {
	    if ($val !~ /$syntax->{re}/) {
		$self->error("invalid value for $path[-1]", %opts);
		$self->{_error_count}++;
		return;
	    }
	}

	if (my $ck = $syntax->{check}) {
	    unless ($self->$ck(\$val, undef, $node->locus)) {
 		$self->{_error_count}++;
		return;
	    }
	}

	$node->value($val);
    }
}

sub _lint {
    my ($self, $syntab, $node, @path) = @_;
    
    while (my ($var, $value) = each %{$node->subtree}) {
	if (exists($syntab->{$var})) {
	    $self->__lint($syntab->{$var}, $value, @path, $var);
	} elsif (exists($syntab->{'*'})) {
	    $self->__lint($syntab->{'*'}, $value, @path, $var);
	} elsif ($value->is_section) {
	    next;
	} else {
	    $self->error("keyword \"$var\" is unknown",
			 locus => $value->locus);
 	    $self->{_error_count}++;
	}
    }
}

=head2 $cfg->lint(\%synt)

Checks the syntax according to the syntax table B<%synt>.  On success,
applies eventual default values and returns true.  On errors, reports
them using B<error> and returns false.

This method provides a way to delay syntax checking for a later time,
which is useful, e.g. if some parts of the parser are loaded as modules
after calling B<parse>.    
    
=cut

sub lint {
    my ($self, $synt) = @_;

#    $synt->{'*'} = { section => { '*' => 1 }} ;
    $self->_lint($synt, $self->tree);
    $self->_fixup($self->tree, $synt);
    return $self->{_error_count} == 0;
}

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