#!/usr/bin/env perl

# blaze-edit - edits a blog post or a page in a BlazeBlogger repository
# Copyright (C) 2008-2011 Jaromir Hradilek

# 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, version 3 of the License.
#
# This program  is  distributed  in the hope  that it will  be useful,  but
# WITHOUT  ANY WARRANTY;  without  even the implied  warranty of MERCHANTA-
# BILITY  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 <http://www.gnu.org/licenses/>.

use strict;
use warnings;
use Digest::MD5;
use File::Basename;
use File::Copy;
use File::Path;
use File::Spec::Functions;
use Getopt::Long;

# General script information:
use constant NAME    => basename($0, '.pl');        # Script name.
use constant VERSION => '1.2.0';                    # Script version.

# General script settings:
our $blogdir = '.';                                 # Repository location.
our $editor  = '';                                  # Editor to use.
our $force   = 0;                                   # Force raw file?
our $process = 1;                                   # Use processor?
our $verbose = 1;                                   # Verbosity level.

# Global variables:
our $conf    = {};                                  # Configuration.

# Set up the __WARN__ signal handler:
$SIG{__WARN__} = sub {
  print STDERR NAME . ": " . (shift);
};

# Display an error message, and terminate the script:
sub exit_with_error {
  my $message      = shift || 'An error has occurred.';
  my $return_value = shift || 1;

  # Display the error message:
  print STDERR NAME . ": $message\n";

  # Terminate the script:
  exit $return_value;
}

# Display a warning message:
sub display_warning {
  my $message = shift || 'A warning was requested.';

  # Display the warning message:
  print STDERR "$message\n";

  # Return success:
  return 1;
}

# Display usage information:
sub display_help {
  my $NAME = NAME;

  # Display the usage:
  print << "END_HELP";
Usage: $NAME [-fpqCPV] [-b DIRECTORY] [-E EDITOR] ID
       $NAME -h|-v

  -b, --blogdir DIRECTORY     specify a directory in which the BlazeBlogger
                              repository is placed
  -E, --editor EDITOR         specify an external text editor
  -p, --page                  edit a page
  -P, --post                  edit a blog post
  -f, --force                 create an empty source file in case it does
                              not already exist
  -C, --no-processor          disable processing the blog post or page with
                              an external application
  -q, --quiet                 do not display unnecessary messages
  -V, --verbose               display all messages
  -h, --help                  display this help and exit
  -v, --version               display version information and exit
END_HELP

  # Return success:
  return 1;
}

# Display version information:
sub display_version {
  my ($NAME, $VERSION) = (NAME, VERSION);

  # Display the version:
  print << "END_VERSION";
$NAME $VERSION

Copyright (C) 2008-2011 Jaromir Hradilek
This program is free software; see the source for copying conditions. It 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 PAR-
TICULAR PURPOSE.
END_VERSION

  # Return success:
  return 1;
}

# Translate a date to the YYYY-MM-DD form:
sub date_to_string {
  my @date = localtime(shift);
  return sprintf("%d-%02d-%02d", ($date[5] + 1900), ++$date[4], $date[3]);
}

# Read data from the INI file:
sub read_ini {
  my $file    = shift || die 'Missing argument';

  # Initialize required variables:
  my $hash    = {};
  my $section = 'default';

  # Open the file for reading:
  open(INI, "$file") or return 0;

  # Process each line:
  while (my $line = <INI>) {
    # Parse the line:
    if ($line =~ /^\s*\[([^\]]+)\]\s*$/) {
      # Change the section:
      $section = $1;
    }
    elsif ($line =~ /^\s*(\S+)\s*=\s*(\S.*)$/) {
      # Add the option to the hash:
      $hash->{$section}->{$1} = $2;
    }
  }

  # Close the file:
  close(INI);

  # Return the result:
  return $hash;
}

# Write data to the INI file:
sub write_ini {
  my $file = shift || 'Missing argument';
  my $hash = shift || 'Missing argument';

  # Open the file for writing:
  open(INI, ">$file") or return 0;

  # Process each section:
  foreach my $section (sort(keys(%$hash))) {
    # Write the section header to the file:
    print INI "[$section]\n";

    # Process each option in the section:
    foreach my $option (sort(keys(%{$hash->{$section}}))) {
      # Write the option and its value to the file:
      print INI "  $option = $hash->{$section}->{$option}\n";
    }
  }

  # Close the file:
  close(INI);

  # Return success:
  return 1;
}

# Read the content of the configuration file:
sub read_conf {
  # Prepare the file name:
  my $file = catfile($blogdir, '.blaze', 'config');

  # Parse the file:
  if (my $conf = read_ini($file)) {
    # Return the result:
    return $conf;
  }
  else {
    # Report failure:
    display_warning("Unable to read the configuration.");

    # Return an empty configuration:
    return {};
  }
}

# Make proper URL from the string while stripping all forbidden characters:
sub make_url {
  my $url = shift || return '';

  # Strip forbidden characters:
  $url =~ s/[^\w\s\-]//g;

  # Strip trailing spaces:
  $url =~ s/\s+$//;

  # Substitute spaces:
  $url =~ s/\s+/-/g;

  # Return the result:
  return $url;
}

# Look for erroneous or missing header data:
sub check_header {
  my $data = shift || die 'Missing argument';
  my $id   = shift || die 'Missing argument';
  my $type = shift || die 'Missing argument';

  # Check whether the title is specified:
  unless ($data->{header}->{title}) {
    # Display the appropriate warning:
    display_warning("Missing title in the $type with ID $id.");
  }

  # Check whether the author is specified:
  unless ($data->{header}->{author} || $type eq 'page') {
    # Report the missing author:
    display_warning("Missing author in the $type with ID $id.");
  }

  # Check whether the date is specified:
  if (my $date = $data->{header}->{date}) {
    # Check whether the format is valid:
    unless ($date =~ /\d{4}-[01]\d-[0-3]\d/) {
      # Report the invalid date:
      display_warning("Invalid date in the $type with ID $id.");
    }
  }
  else {
    # Report the missing date:
    display_warning("Missing date in the $type with ID $id.");
  }

  # Check whether the tags are specified:
  if (my $tags = $data->{header}->{tags}) {
    # Make all tags lower case:
    $tags = lc($tags);

    # Strip superfluous characters:
    $tags =~ s/\s{2,}/ /g;
    $tags =~ s/\s+$//;
    $tags =~ s/^,+|,+$//g;

    # Remove duplicates:
    my %temp = map { $_, 1 } split(/,+\s*/, $tags);

    # Make sure none of the tags will have an empty URL:
    foreach my $tag (keys %temp) {
      # Derive the URL from the tag name:
      my $tag_url = make_url($tag);

      # Make sure the result is not empty:
      unless ($tag_url) {
        # Report the missing tag URL:
        display_warning("Unable to derive a URL from the tag `$tag'. " .
                        "Please use ASCII characters only.");
      }
    }
  }

  # Check whether the URL is specified:
  if (my $url = $data->{header}->{url}) {
    # Check whether it contains forbidden characters:
    if ($url =~ /[^\w\-]/) {
      # Report the invalid URL:
      display_warning("Invalid URL in the $type with ID $id." .
                      ($url ? "" : " It will be derived from the title."));
    }
  }

  # Make sure the URL can be derived from the title if necessary:
  unless ($data->{header}->{url}) {
    # Derive the URL from the post or page title:
    my $title = $data->{header}->{title} || '';
    my $url   = make_url(lc($title));

    # Check whether the URL is not empty:
    unless ($url) {
      # Report the missing URL:
      display_warning("Unable to derive the URL in the $type with ID $id. " .
                      "Please specify it yourself.");
    }
  }

  # Return success:
  return 1;
}

# Create a single file from a record:
sub read_record {
  my $file = shift || die 'Missing argument';
  my $id   = shift || die 'Missing argument';
  my $type = shift || 'post';

  # Prepare the record file names:
  my $head_file = catfile($blogdir, '.blaze', "${type}s", 'head', $id);
  my $body_file = catfile($blogdir, '.blaze', "${type}s", 'body', $id);
  my $raw_file  = catfile($blogdir, '.blaze', "${type}s", 'raw',  $id);

  # If the processor is enabled, make sure the raw file exists:
  if ($process && ! -e $raw_file) {
    exit_with_error("The raw file does not exist. Use `--force' to create " .
                    "a new one, or `--no-processor' to disable the " .
                    "processor.", 1)
      unless $force;
  }

  # Parse the record header data:
  my $data = read_ini($head_file) or return 0;

  # Collect the data for the file header:
  my $author   = $data->{header}->{author}   || '';
  my $title    = $data->{header}->{title}    || '';
  my $date     = $data->{header}->{date}     || '';
  my $keywords = $data->{header}->{keywords} || '';
  my $tags     = $data->{header}->{tags}     || '';
  my $url      = $data->{header}->{url}      || '';

  # Declare other necessary variables:
  my $head;

  # Prepare the temporary file header:
  if ($type eq 'post') {
    # Use the variant for a blog post:
    $head = << "END_POST_HEADER";
# This and the following lines beginning with '#' are the blog post header.
# Please take your time and replace these options with desired values. Just
# remember that the date has to be in the YYYY-MM-DD form, tags are a comma
# separated list of categories the post (pages ignore these) belong to, and
# the url,  if provided, should consist of alphanumeric characters, hyphens
# and underscores only.  Specifying your own url  is especially recommended
# in case you use non-ASCII characters in your blog post title.
#
#   title:    $title
#   author:   $author
#   date:     $date
#   keywords: $keywords
#   tags:     $tags
#   url:      $url
#
# The header ends here. The rest is the content of your blog post.
END_POST_HEADER
  }
  else {
    # Use the variant for a page:
    $head = << "END_PAGE_HEADER";
# This and the following lines beginning with '#' are the page header. Ple-
# ase take your time and replace these  options with  desired  values. Just
# remember that the date has to be in the YYYY-MM-DD form, and the  url, if
# provided, should  consist of alphanumeric characters,  hyphens and under-
# scores only. Specifying your own url  is especially  recommended  in case
# you use non-ASCII characters in your page title.
#
#   title:    $title
#   date:     $date
#   keywords: $keywords
#   url:      $url
#
# The header ends here. The rest is the content of your page.
END_PAGE_HEADER
  }

  # Open the file for writing:
  if (open(FOUT, ">$file")) {
    # Write the header:
    print FOUT $head;

    # Skip this part when forced to create empty raw file:
    unless ($process && ! -e $raw_file && $force) {
      # Open the record for the reading:
      open(FIN, ($process ? $raw_file : $body_file)) or return 0;

      # Add the content of the record body to the file:
      while (my $line = <FIN>) {
        print FOUT $line;
      }

      # Close the record:
      close(FIN);
    }

    # Close the file:
    close(FOUT);

    # Return success:
    return 1;
  }
  else {
    # Report failure:
    display_warning("Unable to create the temporary file.");

    # Return failure:
    return 0;
  }
}

# Create a record from the single file:
sub save_record {
  my $file = shift || die 'Missing argument';
  my $id   = shift || die 'Missing argument';
  my $type = shift || 'post';
  my $data = shift || {};

  # Initialize required variables:
  my $line = '';

  # Prepare the record directory names:
  my $head_dir  = catdir($blogdir, '.blaze', "${type}s", 'head');
  my $body_dir  = catdir($blogdir, '.blaze', "${type}s", 'body');
  my $raw_dir   = catdir($blogdir, '.blaze', "${type}s", 'raw');

  # Prepare the record file names:
  my $head      = catfile($head_dir, $id);
  my $body      = catfile($body_dir, $id);
  my $raw       = catfile($raw_dir,  $id);

  # Prepare the temporary file names:
  my $temp_head = catfile($blogdir, '.blaze', 'temp.head');
  my $temp_body = catfile($blogdir, '.blaze', 'temp.body');
  my $temp_raw  = catfile($blogdir, '.blaze', 'temp.raw');

  # Read required data from the configuration:
  my $processor = $conf->{core}->{processor};

  # Check whether the processor is enabled:
  if ($process) {
    # Substitute placeholders with actual file names:
    $processor  =~ s/%in%/$temp_raw/ig;
    $processor  =~ s/%out%/$temp_body/ig;
  }

  # Open the input file for reading:
  open(FIN, "$file") or return 0;

  # Parse the file header:
  while ($line = <FIN>) {
    # The header ends with the first line not beginning with "#":
    last unless $line =~ /^#/;

    # Collect data for the record header:
    if ($line =~ /(title|author|date|keywords|tags|url):\s*(\S.*)$/) {
      $data->{header}->{$1} = $2;
    }
  }

  # Fix erroneous or missing header data:
  check_header($data, $id, $type);

  # Write the record header to the temporary file:
  write_ini($temp_head, $data) or return 0;

  # Open the proper output file:
  open(FOUT, '>' . ($process ? $temp_raw : $temp_body)) or return 0;

  # Write the last read line to the output file:
  print FOUT $line if $line;

  # Add the rest of the file content to the output file:
  while ($line = <FIN>) {
    print FOUT $line;
  }

  # Close all opened files:
  close(FIN);
  close(FOUT);

  # Check whether the processor is enabled:
  if ($process) {
    # Process the raw input file:
    unless (system("$processor") == 0) {
      # Report failure and exit:
      exit_with_error("Unable to run `$processor'.", 1);
    }

    # Make sure the raw record directory exists:
    unless (-d $raw_dir) {
      # Create the target directory tree:
      eval { mkpath($raw_dir, 0); };

      # Make sure the directory creation was successful:
      exit_with_error("Creating the directory tree: $@", 13) if $@;
    }

    # Create the raw record file:
    move($temp_raw, $raw) or return 0;
  }

  # Make sure the record body and header directories exist:
  unless (-d $head_dir && -d $body_dir) {
    # Create the target directory tree:
    eval { mkpath([$head_dir, $body_dir], 0); };

    # Make sure the directory creation was successful:
    exit_with_error("Creating the directory tree: $@", 13) if $@;
  }

  # Create the record body and header files:
  move($temp_body, $body) or return 0;
  move($temp_head, $head) or return 0;

  # Return success:
  return 1;
}

# Edit a record in the repository:
sub edit_record {
  my $id   = shift || die 'Missing argument';
  my $type = shift || 'post';

  # Initialize required variables:
  my ($before, $after);

  # Prepare the temporary file name:
  my $temp = catfile($blogdir, '.blaze', 'temp');

  # Decide which editor to use:
  my $edit = $editor || $conf->{core}->{editor} || $ENV{EDITOR} || 'vi';

  # Create the temporary file:
  unless (read_record($temp, $id, $type)) {
    # Report failure:
    display_warning("Unable to read the $type with ID $id.");

    # Return failure:
    return 0;
  }

  # Open the file for reading:
  if (open(FILE, "$temp")) {
    # Set the input/output handler to "binmode":
    binmode(FILE);

    # Count the checksum:
    $before = Digest::MD5->new->addfile(*FILE)->hexdigest;

    # Close the file:
    close(FILE);
  }

  # Open the temporary file in the external editor:
  unless (system("$edit $temp") == 0) {
    # Report failure:
    display_warning("Unable to run `$edit'.");

    # Return failure:
    return 0;
  }

  # Open the file for reading:
  if (open(FILE, "$temp")) {
    # Set the input/output handler to "binmode":
    binmode(FILE);

    # Count the checksum:
    $after = Digest::MD5->new->addfile(*FILE)->hexdigest;

    # Close the file:
    close(FILE);

    # Compare the checksums:
    if ($before eq $after) {
      # Report abortion:
      display_warning("The file has not been changed: aborting.");

      # Return success:
      exit 0;
    }
  }

  # Save the record:
  unless (save_record($temp, $id, $type)) {
    # Report failure:
    display_warning("Unable to write the $type with ID $id.");

    # Return failure:
    return 0
  }

  # Remove the temporary file:
  unlink $temp;

  # Return success:
  return 1;
}

# Add the event to the log:
sub add_to_log {
  my $text = shift || 'Something miraculous has just happened!';

  # Prepare the log file name:
  my $file = catfile($blogdir, '.blaze', 'log');

  # Open the log file for appending:
  open(LOG, ">>$file") or return 0;

  # Write the event to the file:
  print LOG localtime(time) . " - $text\n";

  # Close the file:
  close(LOG);

  # Return success:
  return 1;
}

# Set default options:
my $type = 'post';                                  # Type: post or page.

# Set up the option parser:
Getopt::Long::Configure('no_auto_abbrev', 'no_ignore_case', 'bundling');

# Process command line options:
GetOptions(
  'help|h'         => sub { display_help();    exit 0; },
  'version|v'      => sub { display_version(); exit 0; },
  'page|pages|p'   => sub { $type    = 'page'; },
  'post|posts|P'   => sub { $type    = 'post'; },
  'force|f'        => sub { $force   = 1;      },
  'no-processor|C' => sub { $process = 0;      },
  'quiet|q'        => sub { $verbose = 0;      },
  'verbose|V'      => sub { $verbose = 1;      },
  'blogdir|b=s'    => sub { $blogdir = $_[1];  },
  'editor|E=s'     => sub { $editor  = $_[1];  },
);

# Check superfluous options:
exit_with_error("Wrong number of options.", 22) if (scalar(@ARGV) != 1);

# Check whether the repository is present, no matter how naive this method
# actually is:
exit_with_error("Not a BlazeBlogger repository! Try `blaze-init' first.",1)
  unless (-d catdir($blogdir, '.blaze'));

# Read the configuration file:
$conf = read_conf();

# Check whether the processor is enabled in the configuration:
if ($process && (my $processor = $conf->{core}->{processor})) {
  # Make sure the processor specification is valid:
  exit_with_error("Invalid core.processor option.", 1)
    unless ($processor =~ /%in%/i && $processor =~ /%out%/i);
}
else {
  # Disable the processor:
  $process = 0;
}

# Edit the record:
edit_record($ARGV[0], $type)
  or exit_with_error("Cannot edit the $type in the repository.", 13);

# Log the event:
add_to_log("Edited the $type with ID $ARGV[0].")
  or display_warning("Unable to log the event.");

# Report success:
print "Your changes have been successfully saved.\n" if $verbose;

# Return success:
exit 0;

__END__

=head1 NAME

blaze-edit - edits a blog post or a page in a BlazeBlogger repository

=head1 SYNOPSIS

B<blaze-edit> [B<-fpqCPV>] [B<-b> I<directory>] [B<-E> I<editor>] I<id>

B<blaze-edit> B<-h>|B<-v>

=head1 DESCRIPTION

B<blaze-edit> opens an existing blog post or a page with the specified
I<id> in an external text editor. Note that there are several special forms
and placeholders that can be used in the text and that will be replaced
with a proper data when the blog is generated.

=head2 Special Forms

=over

=item B<< <!-- break --> >>

A mark to delimit a blog post synopsis.

=back

=head2 Placeholders

=over

=item B<%root%>

A relative path to the root directory of the blog.

=item B<%home%>

A relative path to the index page of the blog.

=item B<%page[>I<id>B<]%>

A relative path to a page with the supplied I<id>.

=item B<%post[>I<id>I<]%>

A relative path to a blog post with the supplied I<id>.

=item B<%tag[>I<name>B<]%>

A relative path to a tag with the supplied I<name>.

=back

=head1 OPTIONS

=over

=item B<-b> I<directory>, B<--blogdir> I<directory>

Allows you to specify a I<directory> in which the BlazeBlogger repository
is placed. The default option is a current working directory.

=item B<-E> I<editor>, B<--editor> I<editor>

Allows you to specify an external text I<editor>. When supplied, this
option overrides the relevant configuration option.

=item B<-p>, B<--page>

Tells B<blaze-edit> to edit a page or pages.

=item B<-P>, B<--post>

Tells B<blaze-edit> to edit a blog post or blog posts. This is the default
option.

=item B<-f>, B<--force>

Tells B<blaze-edit> to create an empty source file in case it does not
already exist. If the B<core.processor> option is enabled, this file is
used as the input to be processed by the selected application.

=item B<-C>, B<--no-processor>

Disables processing a blog post or page with an external application.

=item B<-q>, B<--quiet>

Disables displaying of unnecessary messages.

=item B<-V>, B<--verbose>

Enables displaying of all messages. This is the default option.

=item B<-h>, B<--help>

Displays usage information and exits.

=item B<-v>, B<--version>

Displays version information and exits.

=back

=head1 ENVIRONMENT

=over

=item B<EDITOR>

Unless the B<core.editor> option is set, BlazeBlogger tries to use
system-wide settings to decide which editor to use.

=back

=head1 EXAMPLE USAGE

Edit a blog post in an external text editor:

  ~]$ blaze-edit 10

Edit a page in an external text editor:

  ~]$ blaze-edit -p 4

Edit a page in B<nano>:

  ~]$ blaze-edit -p 2 -E nano

=head1 SEE ALSO

B<blaze-config>(1), B<blaze-add>(1), B<blaze-list>(1)

=head1 BUGS

To report a bug or to send a patch, please, add a new issue to the bug
tracker at <http://code.google.com/p/blazeblogger/issues/>, or visit the
discussion group at <http://groups.google.com/group/blazeblogger/>.

=head1 COPYRIGHT

Copyright (C) 2008-2011 Jaromir Hradilek

This program is free software; see the source for copying conditions. It 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.

=cut
