NAME
    Stepford - A vaguely Rake/Make/Cake-like thing for Perl - create steps
    and let a planner run them

VERSION
    version 0.002002

SYNOPSIS
        package My::Step::MakeSomething;

        use autodie;
        use Moose;

        has input_file => (
            traits   => ['StepDependency'],
            is       => 'ro',
            required => 1,
        );

        has output_file => (
            traits  => ['StepProduction'],
            is      => 'ro',
            default => '/path/to/file',
        );

        with 'StepFord::Role::Step::FileGenerator';

        sub run {
            my $self = shift;

            open my $input_fh,  '<', $self->input_file();
            open my $output_fh, '>', $self->output_file();
            while (<$input_fh>) {
                chomp;
                print {$output_fh} $_ * 2, "\n";
            }
            close $input_fh;
            close $output_fh;
        }

        package My::Runner;

        use Stepford::Planner;

        my $planner = Stepford::Planner->new(
            step_namespaces => 'My::Step',
            logger          => $log_dispatch_object,    # optional
            jobs            => 4,                       # optional
        );

        # Runs all the steps needed to get to the final_steps.
        $planner->run(
            final_steps => 'My::Step::MakeSomething',
        );

DESCRIPTION
    NOTE: This is alpha code. You have been warned!

    Stepford provides a framework for running a set of steps that are
    dependent on other steps. At a high level, this is a lot like Make,
    Rake, etc. However, the actual implementation is fairly different.
    Currently, there is no DSL, no Stepfile, etc.

    With Stepford, each step is represented by a class you create. That
    class should consume either the StepFord::Role::Step::FileGenerator role
    (if it generates files) or the StepFord::Role::Step step (if it
    doesn't).

    Steps declare both their dependencies (required inputs) and productions
    (outputs) as attributes. These attributes should be given either the
    "StepDependency" or "StepProduction" trait as appropriate.

    The Stepford::Planner class analyzes the dependencies and productions
    for each step to figure out what steps it needs to run in order to
    satisfy the dependencies of the final steps you specify.

    Each step can specify a "last_run_time()" method (or get one from the
    StepFord::Role::Step::FileGenerator role). The planner uses this to skip
    steps that are up to date.

    See Stepford::Planner, Stepford::Role::Step, and
    StepFord::Role::Step::FileGenerator for more details.

CONCEPTS AND DESIGN
    In order to understand how Stepford works you must understand a few key
    concepts.

    First off, we have steps. A step is simply a self-contained unit of
    work, like generating a file, populating a database, etc. There are no
    restrictions on what steps can do. The only restriction is that they are
    expected to declare their dependencies and/or productions (more on these
    below).

    Each step is a Moose class. Each step class should represent a concrete
    action, not a higher-level concept. In other words, the class name
    should be something like "CopyFooBarFilesToProduction", not "CopyFiles".
    If you have several steps that all share similar logic, you can use a
    role to share that logic between classes.

    Each step must declare its dependencies and/or productions as regular
    Moose attributes. These attributes can contain any type of value. They
    are simply data. Note, however, that if you want to run steps in
    parallel, then the dependencies (and therefore productions) must be
    serializable data types (so no DBI handles, etc.).

    A dependency is simply a value that a given step expects to get from
    another step (they can also be supplied to the planner manully).

    The flip side of a dependency is a production. This is a value that the
    step will generate as needed.

    Steps are run by a Stepford::Planner object. To create this object, you
    give it a list of step namespaces and the class(es) of the final step(s)
    you want to run. The planner looks at the final steps' dependencies and
    uses this information to figure out what other steps to run. It looks
    for steps with productions that satisfy these dependencies and adds any
    matching steps to the execution plan. It does this iteratively for each
    step it adds to the plan until the dependencies are satisfied for every
    step.

    The planner detects cyclic dependencies (A requires B requires C
    requires B) and throws an error. It also detects when a step has a
    dependency that cannot be satisfied by the production of any other step.

    Note that the matching of production to dependency is done solely by
    name. It's up to you to ensure that the output of a production is
    something that satisfies the dependency (in terms of the value's type,
    content, etc.).

    If multiple classes have a production of the same name, then the first
    class that Stepford sees "wins". This can be useful if you want to
    override a step for testing, for example. See the documentation of the
    Stepford::Planner class's "new()" method for more details on step
    namespaces.

    It is not possible for a class to have an attribute that is
    simultaneously a dependency and a production. This would be a natural
    design for a step that transformed a data value, but it makes dependency
    resolution impossible. However, nothing stops you from having two
    attributes that each produce the same value. For example, the attributes
    could both reference a path on disk and the step's "run()" method could
    alter the content of that file in place.

    It is not currently possible for a class to have optional dependencies.
    This may be added in the future if it turns out to be useful.

FUTURE FEATURES
    There are several very obvious things that should be added to this
    framework:

    *   Dry runs

VERSIONING POLICY
    This module uses semantic versioning as described by
    <http://semver.org/>. Version numbers can be read as X.YYYZZZ, where X
    is the major number, YYY is the minor number, and ZZZ is the patch
    number.

SUPPORT
    Please report all issues with this code using the GitHub issue tracker
    at <https://github.com/maxmind/Stepford/issues>.

AUTHOR
    Dave Rolsky <drolsky@maxmind.com>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2014 by MaxMind, Inc..

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.

