#!/bin/env perl

=head1 NAME

dist_surveyor - determine exactly what dist versions are installed

=head1 VERSION

version 0.001

=head1 SYNOPSIS

  dist_surveyor [options] /some/perl/lib/dir

=head1 DESCRIPTION

This utility examines all the modules installed within the specified perl
library directory and uses the metacpan API to work out what versions of what
distributions could have provided those modules. It then works out which of
those candidate distributions is the most likely one.

It is fairly robust and copes well with edge cases like installation of
non-released versions from git repos and local modifications.

Distributions are written to stdout. Progress and issues are reported to stderr.

It can take a long time to run for the first time on a directory with a
large number of modules and candidate distributions.  The data fetched from
metacpan is cached so future runs are much faster.  (The system this code was
tested on took about 60 minutes to process around 500 distributions with no
cached data, and under 10 minutes for later runs that could reuse the cached
data. The cache file ended up about 40MB in size.)

=head1 OPTIONS

    --verbose    Show more detailed progress

    --debug      Show much more information

    --match R    Ignore modules that don't match regex R (unanchored)

    --perlver V  Ignore modules that are shipped with perl version V

    --remnants   Include old distribution versions that have left old modules behind

    --uncached   Don't use or update the persistent cache

    --makecpan D Create a CPAN repository in directory D

    --output S   List of field names to output, separate by spaces.
                 
    --format S   Printf format string with a %s for each field in --output

=head2 --makecpan

Creates a CPAN repository in the specified directory by fetching the selected
distributions into authors/id/... and writing the index files into modules/...

If the directory already exists then selected distributions that already exist
are not refetched, any distributions that already exist but aren't selected by
this run are left in place.

New package distribution information is merged into the modules/02packages index file.

Some additional files are written into a dist_surveyor subdirectory:

=head3 dist_surveyor/token_packages.txt

This file lists one unique 'token package' per distribution. It's very useful
to speed up re-running a full install after some distributions have failed.

=head1 USAGE

Run a survey and create a mini-CPAN repository containing the distributions:

    dist_surveyor --makecpan my_cpan /some/perl/lib/dir > installed_dists.txt

It's important to give the correct perl lib directory path.

It's important to check the results related to any modules that generated
warnings during the run.

Install those distributions into a new library:

    cpanm --mirror file:$PWD/my_cpan [--mirror-only] -l new_lib < installed_dists.txt

That will always reinstall all the listed distributions. If some distributions
fail to install (typically due to test failures) then it's I<much> faster to use the
'token package list' on later runs:

    cpanm --mirror file:$PWD/my_cpan [--mirror-only] -l new_lib < my_cpan/dist_surveyor/token_packages.txt

Using package name allows cpanm to skip those that it knows are already installed.

When using dist_surveyor to migrate perl versions, use the old perl to run
dist_surveyor and the new perl to run cpanm.

=head1 BUGS

Probably.

=head1 TODO

    * Polish up, refactor, add tests etc. Including making Dist::Surveyor a proper
        module that exports functions (or uses methods) and changing dist_surveyor
        to use that interface.

    * Auto-detect when directory given isn't the root of a perl library dir tree.
        E.g. by matching file names to module names

    * Add support for matching Foo.pm.PL files (e.g. FCGI and common::sense)

    * For installed modules get the file modification time (last commit time)
        and use it to eliminate candidate dists that were released after that time.

    * Consider factoring in release status ('authorized') so rogue releases
        that ship copies of many other modules (like Net-Braintree-0.1.1)
        are given a lower priority.

    * Sort out ExtUtils::Perllocal::Parser situation
        Avoid hard-coded %distro_key_mod_names related to perllocal.pod where the
        dist name doesn't match the key module name.
        Or maybe just remove use of distro_key_mod_names and perllocal entirely?

    * Optimise use of metacpan. Check caching. Use ElasticSearch.pm.

    * Fully handle merging of pre-existing --makecpan directory data files.

    * Consider factoring install date in the output ordering. May help with edge cases
        where a package P is installed via distros A then B. If A is reinstalled after B
        then the reinstalled P will be from A but should be from B. (I don't know of any
        cases, but it's certainly a possibility. The LWP breakup and Class::MOP spring to
        mind as possible candidates.)

=cut

use strict;
use warnings;

$| = 1;

require Dist::Surveyor;

# XXX nasty quick hack conversion from script to module
# TODO refactor to give Dist::Surveyor a reasonable simple API
# and use that here
Dist::Surveyor::main(@ARGV);

exit 0;