Algorithm-Dependency
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package Algorithm::Dependency; # git description: v1.111-8-g2fb772e
# ABSTRACT: Base class for implementing various dependency trees
#pod =pod
#pod
#pod =head1 SYNOPSIS
#pod
#pod Typical Usage: Ordering based on dependency requirements
#pod
#pod use Algorithm::Dependency::Ordered;
#pod use Algorithm::Dependency::Source::HoA;
#pod
#pod my $deps = {
#pod core => [ ],
#pod a => [ 'core' ],
#pod b => [ 'a' ]
#pod this => [ ],
#pod that => [ ],
#pod };
#pod my $deps_source = Algorithm::Dependency::Source::HoA->new( $deps );
#pod
#pod my $dep = Algorithm::Dependency::Ordered->new(
#pod source => $deps_source,
#pod selected => [ 'this', 'that' ], # Items we have processed elsewhere or have already satisfied
#pod )
#pod or die 'Failed to set up dependency algorithm';
#pod
#pod my $also = $dep->schedule_all();
#pod # Returns: ['core', 'a', 'b'] -- ie: installation-order. Whereas using base
#pod # Algorithm::Dependency would return sorted ['a', 'b', 'core']
#pod
#pod my $also = $dep->schedule( 'b' );
#pod # Returns: ['core', 'a', 'b'] -- installation order, including ourselves
#pod
#pod my $also = $dep->depends( 'b' );
#pod # Returns: ['a', 'core'] -- sorted order, not including ourselves
#pod
#pod Base Classes
#pod
#pod use Algorithm::Dependency;
#pod use Algorithm::Dependency::Source::File;
#pod
#pod # Load the data from a simple text file
#pod my $data_source = Algorithm::Dependency::Source::File->new( 'foo.txt' );
#pod
#pod # Create the dependency object, and indicate the items that are already
#pod # selected/installed/etc in the database
#pod my $dep = Algorithm::Dependency->new(
#pod source => $data_source,
#pod selected => [ 'This', 'That' ]
#pod ) or die 'Failed to set up dependency algorithm';
#pod
#pod # For the item 'Foo', find out the other things we also have to select.
#pod # This WON'T include the item we selected, 'Foo'.
#pod my $also = $dep->depends( 'Foo' );
#pod print $also
#pod ? "By selecting 'Foo', you are also selecting the following items: "
#pod . join( ', ', @$also )
#pod : "Nothing else to select for 'Foo'";
#pod
#pod # Find out the order we need to act on the items in.
#pod # This WILL include the item we selected, 'Foo'.
#pod my $schedule = $dep->schedule( 'Foo' );
#pod
#pod =head1 DESCRIPTION
#pod
#pod Algorithm::Dependency is a framework for creating simple read-only
#pod dependency hierarchies, where you have a set of items that rely on other
#pod items in the set, and require actions on them as well.
#pod
#pod Despite the most visible of these being software installation systems like
#pod the CPAN installer, or Debian apt-get, they are useful in other situations.
#pod This module intentionally uses implementation-neutral words, to avoid
#pod confusion.
#pod
#pod =head2 Terminology
#pod
#pod The term C<ITEM> refers to a single entity, such as a single software
#pod package, in the overall set of possible entities. Internally, this is a
#pod fairly simple object. See L<Algorithm::Dependency::Item> for details.
#pod
#pod The term C<SELECT> means that a particular item, for your purposes, has
#pod already been acted up in the required way. For example, if the software
#pod package had already been installed, and didn't need to be re-installed,
lib/Algorithm/Dependency.pm view on Meta::CPAN
#pod the list of the names of the selected items.
#pod
#pod =cut
sub selected_list { sort keys %{$_[0]->{selected}} }
#pod =pod
#pod
#pod =head2 selected $name
#pod
#pod Given an item name, the C<selected> method will return true if the item is
#pod selected, false is not, or C<undef> if the item does not exist, or an error
#pod occurs.
#pod
#pod =cut
sub selected { $_[0]->{selected}->{$_[1]} }
#pod =pod
#pod
#pod =head2 item $name
#pod
#pod The C<item> method fetches and returns the item object, as specified by the
#pod name argument.
#pod
#pod Returns an L<Algorithm::Dependency::Item> object on success, or C<undef> if
#pod an item does not exist for the argument provided.
#pod
#pod =cut
sub item { $_[0]->{source}->item($_[1]) }
#####################################################################
# Main algorithm methods
#pod =pod
#pod
#pod =head2 depends $name1, ..., $nameN
#pod
#pod Given a list of one or more item names, the C<depends> method will return
#pod a reference to an array containing a list of the names of all the OTHER
#pod items that also have to be selected to meet dependencies.
#pod
#pod That is, if item A depends on B and C then the C<depends> method would
#pod return a reference to an array with B and C. ( C<[ 'B', 'C' ]> )
#pod
#pod If multiple item names are provided, the same applies. The list returned
#pod will not contain duplicates.
#pod
#pod The method returns a reference to an array of item names on success, a
#pod reference to an empty array if no other items are needed, or C<undef>
#pod on error.
#pod
#pod NOTE: The result of C<depends> is ordered by an internal C<sort>
#pod irrespective of the ordering provided by the dependency handler. Use
#pod L<Algorithm::Dependency::Ordered> and C<schedule> to use the most
#pod common ordering (process sequence)
#pod
#pod =cut
sub depends {
my $self = shift;
my @stack = @_ or return undef;
my @depends = ();
my %checked = ();
# Process the stack
while ( my $id = shift @stack ) {
# Does the id exist?
my $Item = $self->{source}->item($id)
or $self->{ignore_orphans} ? next : return undef;
# Skip if selected or checked
next if $checked{$id};
# Add its depends to the stack
push @stack, $Item->depends;
$checked{$id} = 1;
# Add anything to the final output that wasn't one of
# the original input.
unless ( scalar grep { $id eq $_ } @_ ) {
push @depends, $id;
}
}
# Remove any items already selected
my $s = $self->{selected};
return [ sort grep { ! $s->{$_} } @depends ];
}
#pod =pod
#pod
#pod =head2 schedule $name1, ..., $nameN
#pod
#pod Given a list of one or more item names, the C<depends> method will
#pod return, as a reference to an array, the ordered list of items you
#pod should act upon in whichever order this particular dependency handler
#pod uses - see L<Algorithm::Dependency::Ordered> for one that implements
#pod the most common ordering (process sequence).
#pod
#pod This would be the original names provided, plus those added to satisfy
#pod dependencies, in the preferred order of action. For the normal algorithm,
#pod where order it not important, this is alphabetical order. This makes it
#pod easier for someone watching a program operate on the items to determine
#pod how far you are through the task and makes any logs easier to read.
#pod
#pod If any of the names you provided in the arguments is already selected, it
#pod will not be included in the list.
#pod
#pod The method returns a reference to an array of item names on success, a
#pod reference to an empty array if no items need to be acted upon, or C<undef>
#pod on error.
#pod
#pod =cut
sub schedule {
my $self = shift;
my @items = @_ or return undef;
# Get their dependencies
my $depends = $self->depends( @items ) or return undef;
# Now return a combined list, removing any items already selected.
# We are allowed to return an empty list.
my $s = $self->{selected};
return [ sort grep { ! $s->{$_} } @items, @$depends ];
}
#pod =pod
#pod
#pod =head2 schedule_all;
#pod
#pod The C<schedule_all> method acts the same as the C<schedule> method, but
#pod returns a schedule that selected all the so-far unselected items.
#pod
#pod =cut
sub schedule_all {
my $self = shift;
$self->schedule( map { $_->id } $self->source->items );
}
1;
__END__
=pod
=encoding UTF-8
=head1 NAME
Algorithm::Dependency - Base class for implementing various dependency trees
=head1 VERSION
version 1.112
=head1 SYNOPSIS
Typical Usage: Ordering based on dependency requirements
use Algorithm::Dependency::Ordered;
use Algorithm::Dependency::Source::HoA;
my $deps = {
core => [ ],
a => [ 'core' ],
b => [ 'a' ]
this => [ ],
that => [ ],
};
my $deps_source = Algorithm::Dependency::Source::HoA->new( $deps );
my $dep = Algorithm::Dependency::Ordered->new(
source => $deps_source,
selected => [ 'this', 'that' ], # Items we have processed elsewhere or have already satisfied
)
or die 'Failed to set up dependency algorithm';
my $also = $dep->schedule_all();
# Returns: ['core', 'a', 'b'] -- ie: installation-order. Whereas using base
# Algorithm::Dependency would return sorted ['a', 'b', 'core']
my $also = $dep->schedule( 'b' );
# Returns: ['core', 'a', 'b'] -- installation order, including ourselves
my $also = $dep->depends( 'b' );
# Returns: ['a', 'core'] -- sorted order, not including ourselves
Base Classes
use Algorithm::Dependency;
use Algorithm::Dependency::Source::File;
# Load the data from a simple text file
my $data_source = Algorithm::Dependency::Source::File->new( 'foo.txt' );
# Create the dependency object, and indicate the items that are already
# selected/installed/etc in the database
my $dep = Algorithm::Dependency->new(
source => $data_source,
selected => [ 'This', 'That' ]
) or die 'Failed to set up dependency algorithm';
# For the item 'Foo', find out the other things we also have to select.
# This WON'T include the item we selected, 'Foo'.
my $also = $dep->depends( 'Foo' );
print $also
? "By selecting 'Foo', you are also selecting the following items: "
. join( ', ', @$also )
: "Nothing else to select for 'Foo'";
# Find out the order we need to act on the items in.
# This WILL include the item we selected, 'Foo'.
my $schedule = $dep->schedule( 'Foo' );
=head1 DESCRIPTION
Algorithm::Dependency is a framework for creating simple read-only
dependency hierarchies, where you have a set of items that rely on other
items in the set, and require actions on them as well.
Despite the most visible of these being software installation systems like
the CPAN installer, or Debian apt-get, they are useful in other situations.
This module intentionally uses implementation-neutral words, to avoid
confusion.
=head2 Terminology
The term C<ITEM> refers to a single entity, such as a single software
package, in the overall set of possible entities. Internally, this is a
fairly simple object. See L<Algorithm::Dependency::Item> for details.
The term C<SELECT> means that a particular item, for your purposes, has
already been acted up in the required way. For example, if the software
package had already been installed, and didn't need to be re-installed,
lib/Algorithm/Dependency.pm view on Meta::CPAN
in this list, we don't have to include it in the output of the C<schedule> or
C<depends> methods.
=item ignore_orphans => 1
Normally, the item source is expected to be largely perfect and error free.
An 'orphan' is an item name that appears as a dependency of another item, but
doesn't exist, or has been deleted.
By providing the C<ignore_orphans> flag, orphans are simply ignored. Without
the C<ignore_orphans> flag, an error will be returned if an orphan is found.
=back
The C<new> constructor returns a new Algorithm::Dependency object on success,
or C<undef> on error.
=head2 source
The C<source> method retrieves the L<Algorithm::Dependency::Source> object
for the algorithm context.
=head2 selected_list
The C<selected_list> method returns, as a list and in alphabetical order,
the list of the names of the selected items.
=head2 selected $name
Given an item name, the C<selected> method will return true if the item is
selected, false is not, or C<undef> if the item does not exist, or an error
occurs.
=head2 item $name
The C<item> method fetches and returns the item object, as specified by the
name argument.
Returns an L<Algorithm::Dependency::Item> object on success, or C<undef> if
an item does not exist for the argument provided.
=head2 depends $name1, ..., $nameN
Given a list of one or more item names, the C<depends> method will return
a reference to an array containing a list of the names of all the OTHER
items that also have to be selected to meet dependencies.
That is, if item A depends on B and C then the C<depends> method would
return a reference to an array with B and C. ( C<[ 'B', 'C' ]> )
If multiple item names are provided, the same applies. The list returned
will not contain duplicates.
The method returns a reference to an array of item names on success, a
reference to an empty array if no other items are needed, or C<undef>
on error.
NOTE: The result of C<depends> is ordered by an internal C<sort>
irrespective of the ordering provided by the dependency handler. Use
L<Algorithm::Dependency::Ordered> and C<schedule> to use the most
common ordering (process sequence)
=head2 schedule $name1, ..., $nameN
Given a list of one or more item names, the C<depends> method will
return, as a reference to an array, the ordered list of items you
should act upon in whichever order this particular dependency handler
uses - see L<Algorithm::Dependency::Ordered> for one that implements
the most common ordering (process sequence).
This would be the original names provided, plus those added to satisfy
dependencies, in the preferred order of action. For the normal algorithm,
where order it not important, this is alphabetical order. This makes it
easier for someone watching a program operate on the items to determine
how far you are through the task and makes any logs easier to read.
If any of the names you provided in the arguments is already selected, it
will not be included in the list.
The method returns a reference to an array of item names on success, a
reference to an empty array if no items need to be acted upon, or C<undef>
on error.
=head2 schedule_all;
The C<schedule_all> method acts the same as the C<schedule> method, but
returns a schedule that selected all the so-far unselected items.
=head1 TO DO
Add the C<check_source> method, to verify the integrity of the source.
Possibly add Algorithm::Dependency::Versions, to implement an ordered
dependency tree with versions, like for perl modules.
Currently readonly. Make the whole thing writable, so the module can be
used as the core of an actual dependency application, as opposed to just
being a tool.
=head1 SEE ALSO
L<Algorithm::Dependency::Ordered>, L<Algorithm::Dependency::Item>,
L<Algorithm::Dependency::Source>, L<Algorithm::Dependency::Source::File>
=head1 SUPPORT
Bugs may be submitted through L<the RT bug tracker|https://rt.cpan.org/Public/Dist/Display.html?Name=Algorithm-Dependency>
(or L<bug-Algorithm-Dependency@rt.cpan.org|mailto:bug-Algorithm-Dependency@rt.cpan.org>).
=head1 AUTHOR
Adam Kennedy <adamk@cpan.org>
=head1 CONTRIBUTORS
=for stopwords Adam Kennedy Karen Etheridge Mark Murawski
=over 4
=item *
Adam Kennedy <adam@ali.as>
=item *
Karen Etheridge <ether@cpan.org>
=item *
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