#!/bin/sh
#
# repair-with - run a file filter on a set of files,
#               replacing them if successful
#
# $Id$
#
# this script is a generalization of ./tidy-us
# which I used to tidy a directory of HTML files with

#--- auxiliaries ---#
#

me=`basename "$0"`

Erro()
{
  #echo $me: "$@" 1>&2
  echo "$@" 1>&2
}

ErroV()
{
  case "$opt_v" in
  yes)
    Erro "$@"
    ;;
  esac
}

Usage()
{
  cat 1>&2 <<ZZ

Usage:	$me [-0] [-v] [-c|-f] command file [file2 [...]]

	to run the given command as a filter on each provided file,
	replacing the file with the results if output is unequal to input.

Options:

  -h	display this help test, do nothing
  -c	the command argument is a /bin/sh command line expecting an argument
  -f	like -c, but it is a filter, expecting no argument
  -0	allow repairs when the result is an empty file
  -v	print progress messages

Examples:

  $me tac *
	# reverses the order of the lines in the matching files

  $me -c 'perl -ne "print reverse"' *
	# the same on systems without tac, but with Perl

  $me -c 'perl -0ne "print reverse"' *
	# also reverses the lines themselves

  $me -f 'tac | rev' *
	# id.

  $me -c 'tac | rev' *
	# fails: 'tac | rev' doesn't count on the filename argument

ZZ
}

IdenticalContent()
{
  cmp "$@" >/dev/null 2>&1
}

Execute()
# always called with 2 arguments
{
  f="$2"

  case "yes" in
  "$opt_c")
    ErroV "$@"
    eval $1 "$2" 2>&3
    ;;
  "$opt_f")
    ErroV "$1" '<' "$2"
    eval $1 \< "$2" 2>&3
    ;;
  *)
    ErroV "$@"
    "$@" 2>&3
  esac >"$f".repaired 3>"$f".err
}

Repair()
{
  f="$1"

  if [ ! -f "$f" ]
  then
    Erro "$f doesn't exist or isn't a plain file, skipped"
    return
  elif Execute "$cmd" "$f"
  then
    :
  else
    Erro "$f cannot be repaired"
    return
  fi

  if IdenticalContent "$f" "$f".repaired
  then
    # keep the original, with its file attributes and possibly hardlinks
    rm -f "$f".repaired
    Erro "$f doesn't need any repairs"
  elif [ "$opt_0" = no ] && IdenticalContent "$f".repaired /dev/null
  then
    Erro "$f becomes empty, not replacing"
  else
    mv "$f" "$f".unrepaired &&
    mv "$f".repaired "$f" &&
    ErroV "$f has been repaired" ||
    Erro "$f couldn't be replaced with the repaired version"
  fi

#  hdr2col -e 's/Parsing "(.*)"/$1/' "$f".err |
#    perl -ne 's/line (\d+) column (\d+) - Warning:/:$1.$2 / and print'
#
# while read line
# do
#   Erro $line
# done < "$f".err

  rm -f "$f".repaired "$f".err
}


#--- cmdline parse ---#
#

opt_e=no
opt_f=no
opt_v=no
opt_0=no

while [ $# -gt 0 ]
do
  case "$1" in
  -c)
    opt_c=yes
    shift
    ;;
  -f)
    opt_f=yes
    shift
    ;;
  -v)
    opt_v=yes
    shift
    ;;
  -0)
    opt_0=yes
    shift
    ;;
  -h|-?)
    Usage
    exit 0
    ;;
  -*)
    Erro "invalid option $1"
    Usage
    exit 1
    ;;
  *)
    break
    ;;
  esac
done

if [ $# -eq 0 ]
then
  Erro "no command supplied"
  exit 1
fi

cmd="$1"
shift

if [ $# -eq 0 ]
then
  Erro "no files or directories supplied"
  exit 1
fi

case yes in
"$opt_c"|"$opt_f")
  ;;
*)
  if type "$cmd" >/dev/null 2>&1
  then
    ErroV "OK, the command '$cmd' is executable"
  else
    Erro "the command '$cmd' is not executable, did you forget -c?"
    exit 2
  fi
  ;;
esac

if [ $# = 0 ]
then
  Erro "no file or directory arguments provided"
  exit 3
fi


#--- go go go! ---#
#

for arg in "$@"
do
  case "$arg" in
  *.err|*.repaired|*.unrepaired)
    ;;
  *)
    Repair "$arg"
    ;;
  esac
done