#!/usr/bin/perl -l
use warnings;
use strict;
use feature qw/switch say/;

# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.

use Term::ReadKey qw/ReadMode ReadKey/;
use File::Temp qw/tempfile/;
use POSIX qw/ctermid/;

my $SVN = $ENV{SVN} || 'svn'; # passed unquoted to sh
my $VIM = 'vim';
my $STATUS = './STATUS';
my $BRANCHES = '^/subversion/branches';

my $YES = $ENV{YES}; # batch mode: eliminate prompts, add sleeps
my $WET_RUN = qw[false true][1]; # don't commit
my $DEBUG = qw[false true][0]; # 'set -x', etc

# derived values
my $SVNq;

$SVN .= " --non-interactive" if $YES or not defined ctermid;
$SVNq = "$SVN -q ";
$SVNq =~ s/-q// if $DEBUG eq 'true';

sub usage {
  my $basename = $0;
  $basename =~ s#.*/##;
  print <<EOF;
Run this from the root of your release branch (e.g., 1.6.x) working copy.

For each entry in STATUS, you will be prompted whether to merge it.

WARNING:
If you accept the prompt, $basename will revert all local changes and will
commit the merge immediately.

The 'svn' binary defined by the environment variable \$SVN, or otherwise the
'svn' found in \$PATH, will be used to manage the working copy.
EOF
}

sub prompt {
  local $\; # disable 'perl -l' effects
  print "Go ahead? ";

  # TODO: this part was written by trial-and-error
  ReadMode 'cbreak';
  my $answer = (ReadKey 0);
  print $answer, "\n";
  return ($answer =~ /^y/i) ? 1 : 0;
}

sub merge {
  my %entry = @_;

  my ($logmsg_fh, $logmsg_filename) = tempfile();
  my ($mergeargs, $pattern);

  my $backupfile = "backport_pl.$$.tmp";

  if ($entry{branch}) {
    # NOTE: This doesn't escape the branch into the pattern.
    $pattern = sprintf '\V\(%s branch(es)?\|branches\/%s\|Branch(es)?:\n *%s\)', $entry{branch}, $entry{branch}, $entry{branch};
    $mergeargs = "--reintegrate $BRANCHES/$entry{branch}";
    print $logmsg_fh "Reintegrate the $entry{header}:";
    print $logmsg_fh "";
  } elsif (@{$entry{revisions}}) {
    $pattern = '^ [*] \V' . 'r' . $entry{revisions}->[0];
    $mergeargs = join " ", (map { "-c$_" } @{$entry{revisions}}), '^/subversion/trunk';
    if (@{$entry{revisions}} > 1) {
      print $logmsg_fh "Merge the $entry{header} from trunk:";
      print $logmsg_fh "";
    } else {
      print $logmsg_fh "Merge r$entry{revisions}->[0] from trunk:";
      print $logmsg_fh "";
    }
  } else {
    die "Don't know how to call $entry{header}";
  }
  print $logmsg_fh $_ for @{$entry{entry}};
  close $logmsg_fh or die "Can't close $logmsg_filename: $!";

  my $script = <<"EOF";
#!/bin/sh
set -e
if $DEBUG; then
  set -x
fi
$SVN diff > $backupfile
$SVNq revert -R .
$SVNq up
$SVNq merge $mergeargs
$VIM -e -s -n -N -i NONE -u NONE -c '/$pattern/normal! dap' -c wq $STATUS
if $WET_RUN; then
  $SVNq commit -F $logmsg_filename
else
  echo "Committing:"
  $SVN status -q
  cat $logmsg_filename
fi
EOF

  $script .= <<"EOF" if $entry{branch};
reinteg_rev=\`$SVN info $STATUS | sed -ne 's/Last Changed Rev: //p'\`
if $WET_RUN; then
  # Sleep to avoid out-of-order commit notifications
  if [ -n "\$YES" ]; then sleep 15; fi
  $SVNq rm $BRANCHES/$entry{branch} -m "Remove the '$entry{branch}' branch, reintegrated in r\$reinteg_rev."
  if [ -n "\$YES" ]; then sleep 1; fi
else
  echo "Removing reintegrated '$entry{branch}' branch"
fi
EOF

  open SHELL, '|-', qw#/bin/sh# or die $!;
  print SHELL $script;
  close SHELL or warn "$0: sh($?): $!";

  unlink $backupfile if -z $backupfile;
  unlink $logmsg_filename unless $? or $!;
}

sub sanitize_branch {
  local $_ = shift;
  s#.*/##;
  s/^\s*//;
  s/\s*$//;
  return $_;
}

# TODO: may need to parse other headers too?
sub parse_entry {
  my @lines = @_;
  my (@revisions, @logsummary, $branch, @votes);
  # @lines = @_;

  # strip first three spaces
  $_[0] =~ s/^ \* /   /;
  s/^   // for @_;

  # revisions
  $branch = sanitize_branch $1 if $_[0] =~ /^(\S*) branch$/;
  while ($_[0] =~ /^r/) {
    while ($_[0] =~ s/^r(\d+)(?:$|[,; ]+)//) {
      push @revisions, $1;
    }
    shift;
  }

  # summary
  push @logsummary, shift until $_[0] =~ /^\s*\w+:/ or not defined $_[0];

  # votes
  unshift @votes, pop until $_[-1] =~ /^\s*Votes:/ or not defined $_[-1];
  pop;

  # branch
  while (@_) {
    shift and next unless $_[0] =~ s/^\s*Branch(es)?:\s*//;
    $branch = sanitize_branch (shift || shift || die "Branch header found without value");
  }

  # Compute a header.
  my $header;
  $header = "r$revisions[0] group" if @revisions;
  $header = "$branch branch" if $branch;
  warn "No header for [@lines]" unless $header;

  return (
    revisions => [@revisions],
    logsummary => [@logsummary],
    branch => $branch,
    header => $header,
    votes => [@votes],
    entry => [@lines],
  );
}

sub handle_entry {
  my %entry = parse_entry @_;
  my @vetoes = grep { /^  -1:/ } @{$entry{votes}};

  if ($YES) {
    merge %entry unless @vetoes;
  } else {
    print "";
    print "\n>>> The $entry{header}:";
    print join ", ", map { "r$_" } @{$entry{revisions}};
    print "$BRANCHES/$entry{branch}" if $entry{branch};
    print "";
    print for @{$entry{logsummary}};
    print "";
    print for @{$entry{votes}};
    print "";
    print "Vetoes found!" if @vetoes;

    merge %entry if prompt;
  }

  # TODO: merge() changes ./STATUS, which we're reading below, but
  #       on my system the loop in main() doesn't seem to care.

  1;
}

sub main {
  usage, exit 0 if @ARGV;

  open STATUS, "<", $STATUS or (usage, exit 1);

  # Because we use the ':normal' command in Vim...
  die "A vim with the +ex_extra feature is required"
      if `${VIM} --version` !~ /[+]ex_extra/;

  # ### TODO: need to run 'revert' here
  # ### TODO: both here and in merge(), unlink files that previous merges added
  die "Local mods to STATUS file $STATUS" if `$SVN status -q $STATUS`;

  # Skip most of the file
  while (<STATUS>) {
    last if /^Approved changes/;
  }
  while (<STATUS>) {
    last unless /^=+$/;
  }
  $/ = ""; # paragraph mode

  while (<STATUS>) {
    my @lines = split /\n/;

    given ($lines[0]) {
      # Section header
      when (/^[A-Z].*:$/i) {
        print "\n\n=== $lines[0]" unless $YES;
      }
      # Separator after section header
      when (/^=+$/i) {
        break;
      }
      # Backport entry?
      when (/^ \*/) {
        warn "Too many bullets in $lines[0]" and next
          if grep /^ \*/, @lines[1..$#lines];
        handle_entry @lines;
      }
      default {
        warn "Unknown entry '$lines[0]' at $ARGV:$.\n";
      }
    }
  }
}

&main