#!/usr/bin/perl
#
# gen-changelog
#
# Copyright © 2020-2022 Guillem Jover <guillem@debian.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 2 of the License, 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 <https://www.gnu.org/licenses/>.
#

use strict;
use warnings;

use lib qw(scripts);

use List::Util qw(uniq);
use Text::Wrap;
use Dpkg::IPC;
use Dpkg::Index;

my @sections = qw(
    main
    arch
    port
    perl-mod
    make-mod
    doc
    code-int
    build-sys
    pkg
    test
    l10n
);

my %sections = (
    arch => {
        title => 'Architecture support',
        match => qr/^arch: /,
    },
    port => {
        title => 'Portability',
        type => 'porting',
    },
    'perl-mod' => {
        title => 'Perl modules',
        match => qr/^(?:Test|Dpkg|Dselect).*[,:] /,
        keep => 1,
    },
    'make-mod' => {
        title => 'Make fragments',
        match => qr{^scripts/mk: },
    },
    doc => {
        title => 'Documentation',
        match => qr/^(?:doc|man)[,:] /,
        keep => 1,
    },
    'code-int' => {
        title => 'Code internals',
        type => 'internal',
        match => qr/^(?:lib(?:compat|dpkg)?|src|scripts|perl|utils): /,
        keep => 1,
    },
    'build-sys' => {
        title => 'Build system',
        match => qr/^build: /,
    },
    pkg => {
        title => 'Packaging',
        match => qr/^debian: /,
    },
    test => {
        title => 'Test suite',
        match => qr/^(?:test|t): /,
    },
    l10n => {
        title => 'Localization',
        match => qr/^po: /,
        sort => 1,
    },
);

my @metafields = qw(
    Thanks-to
    Co-Author
    Based-on-patch-by
    Improved-by
    Prompted-by
    Reported-by
    Required-by
    Analysis-by
    Requested-by
    Suggested-by
    Spotted-by
    Naming-by
    Ref
);

my %metafield = (
    'Co-Author' => 'Co-authored by',
    'Based-on-patch-by' => 'Based on a patch by',
    'Improved-by' => 'Improved by',
    'Prompted-by' => 'Prompted by',
    'Reported-by' => 'Reported by',
    'Required-by' => 'Required by',
    'Analysis-by' => 'Analysis by',
    'Requested-by' => 'Requested by',
    'Suggested-by' => 'Suggested by',
    'Spotted-by' => 'Spotted by',
    'Naming-by' => 'Naming by',
    'Thanks-to' => 'Thanks to',
    'Ref' => 'See',
);

my %mappings = (
    'u-a' => 'update-alternatives',
    's-s-d' => 'start-stop-daemon',
    'dpkg-m-h' => 'dpkg-maintscript-helper',
);

my $log_format =
    'Commit: %H%n' .
    'Author: %aN%n' .
    'AuthorEmail: %aE%n' .
    'Committer: %cN%n' .
    'CommitterEmail: %cE%n' .
    'Title: %s%n' .
    '%(trailers:only,unfold)%N';

my $tag_prev = $ARGV[0];
my $tag_next = $ARGV[1] // "";

$tag_prev //= qx(git describe --abbrev=0);
chomp $tag_prev;

my $fh_gitlog;

spawn(
    exec => [
        qw(git log --first-parent), "--format=tformat:$log_format",
        "$tag_prev..$tag_next"
    ],
    to_pipe => \$fh_gitlog,
);

my $log = Dpkg::Index->new(
    get_key_func => sub { return $_[0]->{Commit} },
    item_opts => {
        keep_duplicate => 1,
        allow_duplicate => 1,
    },
);
$log->parse($fh_gitlog, 'git log');

my %entries;
my %groups;
my @groups;

# Analyze the commits and select which group and section to place them in.
foreach my $id (reverse $log->get_keys()) {
    my $commit = $log->get_by_key($id);
    my $title = $commit->{Title};
    my $group = $commit->{Committer};
    my $changelog = $commit->{'Changelog'};
    my $sectmatch = 'main';

    # Skip irrelevant commits.
    if ($title =~ m/^(?:Bump version to|Release) /) {
        next;
    }
    if ($title =~ m/^po: Regenerate/) {
        next;
    }

    if (defined $changelog) {
        # Skip silent commits.
        next if $changelog =~ m/(?:silent|skip|ignore)/;

        # Include the entire commit body for verbose commits.
        if ($changelog =~ m/(?:verbose|full)/) {
            my $body = qx(git show -s --pretty=tformat:%b $id);
            $commit->{Title} .= "\n$body";
        }

        if ($changelog =~ m{s/([^/]+)/([^/]+)/}) {
            $commit->{Fixup} = {
                old => $1,
                new => $2,
            };
        }
    }

    # Decide into what section the commit should go.
    foreach my $sectname (keys %sections) {
        my $section = $sections{$sectname};

        if ((exists $section->{match} and $title =~ m/$section->{match}/) or
            (exists $section->{type} and defined $changelog and
             $changelog =~ m/$section->{type}/)) {
            $sectmatch = $sectname;
            last;
        }
    }

    # Add the group entries in order, with l10n ones at the end.
    if (not exists $entries{$group}) {
        push @groups, $group;
    }

    push @{$entries{$group}{$sectmatch}}, $commit;
}

# Go over the groups and their sections and format them.
foreach my $groupname (@groups) {
    print "\n";
    print "  [ $groupname ]\n";

    foreach my $sectname (@sections) {
        my $section = $sections{$sectname};

        next unless exists $entries{$groupname}{$sectname};
        next if @{$entries{$groupname}{$sectname}} == 0;

        if (exists $sections{$sectname}->{title}) {
            print "  * $sections{$sectname}->{title}:\n";
        }
        my @entries;
        foreach my $commit (@{$entries{$groupname}{$sectname}}) {
            my $title = $commit->{Title} =~ s/\.$//r . '.';

            # Remove the title prefix if needed.
            if (exists $section->{match} and not exists $section->{keep}) {
                $title =~ s/$section->{match}//;
            }

            # Metafields.
            if ($commit->{Author} ne $commit->{Committer}) {
                $commit->{'Thanks-to'} = "$commit->{Author} <$commit->{AuthorEmail}>";
            }
            foreach my $metafield (@metafields) {
                next unless exists $commit->{$metafield};

                my $values = $commit->{$metafield};
                $values = [ $values ] if ref $values ne 'ARRAY';

                foreach my $value (@{$values}) {
                    $title .= "\n$metafield{$metafield} $value.";
                }
            }
            # Handle the Closes metafield last.
            if (exists $commit->{Closes}) {
                $title .= " Closes: $commit->{Closes}";
            }

            # Handle fixups from git notes.
            if (exists $commit->{Fixup}) {
                $title =~ s/\Q$commit->{Fixup}{old}\E/$commit->{Fixup}{new}/m;
            }

            # Handle mappings.
            foreach my $mapping (keys %mappings) {
                $title =~ s/$mapping/$mappings{$mapping}/g;
            }

            # Select prefix formatting.
            my ($entry_tab, $body_tab);
            if (not exists $sections{$sectname}->{title}) {
                $entry_tab = '  * ';
                $body_tab  = '    ';
            } else {
                $entry_tab = '    - ';
                $body_tab  = '      ';
            }

            local $Text::Wrap::columns = 80;
            local $Text::Wrap::unexpand = 0;
            local $Text::Wrap::huge = 'overflow';
            local $Text::Wrap::break = qr/(?<!Closes:)\s/;
            push @entries, wrap($entry_tab, $body_tab, $title) . "\n";
        }

        if ($sections{$sectname}->{sort}) {
            @entries = uniq(sort @entries);
        }

        print @entries;
    }
}