#!/bin/bash
# s3md5  Copyright (C) 2013
#        Antonio Espinosa <aespinosa at teachnova dot com>
#
# This file is part of s3md5 by Teachnova (www.teachnova.com)
#
# s3md5 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 3 of the License, or
# (at your option) any later version.
#
# s3md5 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 s3md5.  If not, see <http://www.gnu.org/licenses/>.

VERSION='1.2'
DEBUG=0

##################################################################
# s3md5 paths
root_path() {
   SOURCE="${BASH_SOURCE[0]}"
   DIR="$( dirname "$SOURCE" )"
   while [ -h "$SOURCE" ]
   do
     SOURCE="$( readlink "$SOURCE" )"
     [[ $SOURCE != /* ]] && SOURCE="$DIR/$SOURCE"
     DIR="$( cd -P "$( dirname "$SOURCE"  )" && pwd )"
   done
   DIR="$( cd -P "$( dirname "$SOURCE" )" && pwd )"

   echo "$DIR"
}

is_integer() {
   local min="$2"
   local max="$3"

   if ! [[ "$1" =~ ^[0-9]+$ ]] ; then
      return 1
   fi

   if [ -n "$2" ] && [ $2 -gt $1 ]; then return 1; fi
   if [ -n "$3" ] && [ $3 -lt $1 ]; then return 1; fi

   return 0
}

license_show() {
   cat << LICENSE
s3md5 v$VERSION
Copyright (C) 2013 Antonio Espinosa <aespinosa@teachnova.com> - TeachNova
This program comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to redistribute it GPLv3 license conditions. Read LICENSE.md for more details.

LICENSE
}

short_help() {
   option=$1
   if [[ -n "$option" ]]; then
      cat <<EOL
ERROR : Invalid argument: '$option'

EOL
   fi
   cat << HELP
Usage :
  # Get the S3 etag of a file
  $APP <chunk size in MB> <file> [-v|--verbose]

  # Verify the S3 etag of a file
  $APP -e|--etag <etag> <chunk size in MB> <file> [-v|--verbose]

  # Short help
  $APP -h

  # Extended help
  $APP --help

Example :
  # Use 15 MB chunk size (as default in s3cmd .s3cfg config file)
  # and get the etag of "myFile"
  $APP 15 myFile

  # Given the S3 etag, verify if it matches "myFile"
  $APP --etag e3ad981c2963eb533e3e58175cf1c966-8 64 myFile

HELP
}

extended_help() {
   license_show
   cat << HELP
Calculates the Etag/S3 MD5 Sum of a file, using the same algorithm that S3 uses on multipart uploaded files.
Specially usefull on files bigger than 5GB uploaded using multipart S3 API.

HELP
  short_help
}

ARGS=()
function main() {
  if [ $# -gt 0 ]; then
    case "$1" in
      -h)
        short_help
        exit 1
      ;;
      --help)
        extended_help
        exit 1
      ;;
      -e|--etag)
        shift
        ETAG=$1
        shift
        main "$@"
      ;;
      -H|--show-filename)
        shift
        SHOW_FILENAME=1
        main "$@"
      ;;
      -v|--verbose)
        shift
        DEBUG=1
        main "$@"
      ;;
      -*)
        short_help $1
        exit 1
      ;;
      *)
        ARGS+=("$1")
        shift
        main "$@"
      ;;
    esac
  else
    run "${ARGS[@]}"
  fi
}

cleanup() {
   $RM_BIN "$ERROR_FILE"
   $RM_BIN "$SUM_FILE"
   $RM_BIN "$BIN_FILE"
}

if [ "$(uname)" == "Darwin" ]; then
  IS_OSX=1
else
  IS_OSX=0
fi

ROOT_PATH=`root_path`
APP=`basename $0`

ECHO_BIN=$(which echo)
RM_BIN="$(which rm) -f"
DD_BIN=$(which dd)
if [ "$IS_OSX" -eq 0 ]; then
  MD5_BIN=$(which md5sum)
else
  MD5_BIN=$(which md5)
fi
CUT_BIN=$(which cut)
GREP_BIN=$(which grep)
CAT_BIN=$(which cat)
AWK_BIN=$(which awk)
XXD_BIN=$(which xxd)

get_chunks_from_etag() {
  $ECHO_BIN "$1" | cut -d'-' -f 2
}
get_filesize_in_bytes() {
  du -m "$1" | cut -f 1
}
get_chunk_size() {
  local filesize=$1
  local chunks=$2
  local min_chunk_size=`$ECHO_BIN "$filesize / $chunks" | bc`
  local max_chunk_size=`$ECHO_BIN "$filesize / ( $chunks - 1 )" | bc`
  $ECHO_BIN "With $chunks chunks, the possible chunk sizes are between $min_chunk_size MB and $max_chunk_size MB"
}

function run() {
  # Check parameters
  if [ $# -lt 2 ]; then short_help; exit 1; fi

  SIZE="$1"
  FILE="$2"
  local FILESIZE=`get_filesize_in_bytes "$FILE"`
  if [ $DEBUG -eq 1 ]; then
    $ECHO_BIN "File size: $FILESIZE MB"
  fi

  if [ -n "$ETAG" ]; then
    if [ $DEBUG -eq 1 ]; then
      local CHUNKS=`get_chunks_from_etag $ETAG`
      get_chunk_size $FILESIZE $CHUNKS
    fi
  fi
}

main "$@"

if [ ! -f "$FILE" ]; then
   $ECHO_BIN "ERROR : File '$FILE' not found"
   exit 2
fi

if ! is_integer "$SIZE"; then
   $ECHO_BIN "ERROR : Chunk size is not an integer number"
   exit 2
fi

ERROR_FILE="/tmp/s3md5-error-$$.out"
SUM_FILE="/tmp/s3md5-md5sumlist-$$.out"
BIN_FILE="/tmp/s3md5-md5bin-$$.out"

trap "{ cleanup; }" EXIT

$ECHO_BIN -n > "$SUM_FILE"
$ECHO_BIN -n > "$BIN_FILE"

n=0
i=0

while true; do
   sum=`$DD_BIN bs=1024k count=$SIZE skip=$i if="$FILE" 2> "$ERROR_FILE" | $MD5_BIN | $CUT_BIN -d' ' -f1`

   if $GREP_BIN -q "^0 bytes " "$ERROR_FILE"; then
      # break this loop if 0 bytes read
      if [ $DEBUG -eq 1 ]; then
         $ECHO_BIN "END"
      fi
      break
   fi
   if $GREP_BIN -q "cannot skip" "$ERROR_FILE"; then
      # End of file, break this loop
      if [ $DEBUG -eq 1 ]; then
         $ECHO_BIN "END"
      fi
      break
   else
      if [ $DEBUG -eq 1 ]; then
        part=$((n+1))
        to=$((i+SIZE))
        $ECHO_BIN -n "SUM for part $part ($i to $to MB) ... "
      fi
      # Chunk read
      if [ $DEBUG -eq 1 ]; then
         $ECHO_BIN "OK - $sum"
      fi
      i=$((i+SIZE))
      n=$((n+1))
      # Add its md5 sum to sum list file
      $ECHO_BIN "$sum" >> "$SUM_FILE"
   fi
done

if [ $DEBUG -eq 1 ]; then
   $ECHO_BIN "Converting all md5sums to binary"
fi

# Convert all md5 sums (in hex text notation) to bin and concatenate them into a file
$CAT_BIN "$SUM_FILE" | $AWK_BIN '{print $1}' | while read MD5; do $ECHO_BIN $MD5 | $XXD_BIN -r -p >> "$BIN_FILE"; done

# Calculate MD5 sum of this binary file
if [ "$IS_OSX" -eq 0 ]; then
  s3sum=`$MD5_BIN "$BIN_FILE" | $CUT_BIN -d' ' -f1`
else
  s3sum=`$MD5_BIN "$BIN_FILE" | $CUT_BIN -d' ' -f4`
fi

if [ $DEBUG -eq 1 ]; then
   $ECHO_BIN -n "Etag/S3 MD5 Sum : "
fi

filename_in_output=""
[[ -n ${SHOW_FILENAME} ]] && filename_in_output="  ${FILE}"

if [ -n "$ETAG" ]; then
  if [ $DEBUG -eq 1 ]; then
    # Return Etag/S3 MD5 Sum
    $ECHO_BIN "${s3sum}-${n}${filename_in_output}"
  fi
  if [ "${s3sum}-${n}" == "$ETAG" ]; then
    $ECHO_BIN "TRUE"
    exit 0
  else
    $ECHO_BIN "FALSE"
    exit 1
  fi
else
  # Return Etag/S3 MD5 Sum
  $ECHO_BIN "${s3sum}-${n}${filename_in_output}"
fi