#!/bin/bash
# Usage: scan_perpage <imagefile>
#   where imagefile is the data just scanned
# (specify this script to scanadf via -S)

usage()
{
  echo "Usage: $0 <imagefile>"
  echo "Set the following environment variables:"
  echo "  UNPAPER"
  echo "  SEARCHABLE"
  echo "  LANGUAGE"
  echo "  RESOLUTION"
  echo "  PGWIDTHIN"
  echo "  PGHEIGHTIN"
  echo "  SKIP_EMPTY_PAGES"
  echo "  PS2PDF_OPTS (optional)"
  echo "  VERBOSE (optional)"
  echo "  LOCKFILE (required if VERBOSE=1)"
}

log()
{
  if [ $VERBOSE = 1 ]; then
    echo "scan_perpage: $1"
  fi
}

logstdout()
{
  if [ $VERBOSE = 1 ]; then
    cat
  else
    cat > /dev/null
  fi
}

runconstrained()
{
  if [ -x "$(command -v sem)" ]; then
    # use up to 75% of the cores available
    sem --jobs 75% --id scan_perpage --fg "$@"
  else
    "$@"
  fi
}

if [ $# -lt 1 ]; then
  usage
  exit 1
fi

if [ "$UNPAPER" == "" -o "$SEARCHABLE" == "" -o "$RESOLUTION" == "" -o "$RESOLUTION" == "" -o "$SKIP_EMPTY_PAGES" == "" ]; then
  usage
  exit 1
fi

IMAGE_PATH=$1
IMAGE_DIR=$(dirname $1)
IMAGE_FILE=$(basename $1)

process_page() {
  log ""
  log "-------------------------------------------------------------------------------"
  log "Post-processing scanned page ${IMAGE_PATH}, deskew=$UNPAPER, searchable=$SEARCHABLE..."


  if [[ $SKIP_EMPTY_PAGES -eq 1 ]]; then
    PERCENTAGE_WHITE=$(convert "$IMAGE_PATH" -fuzz 0% -negate -threshold 0 -negate -format "%[fx:100*mean]" info:) || PERCENTAGE_WHITE=0
    log "$IMAGE_PATH has $PERCENTAGE_WHITE % white"
  else
    PERCENTAGE_WHITE=0
  fi

  PP_PREFIX=
  if (( $(echo "$PERCENTAGE_WHITE < 99.8" | bc -l) )); then
    if [ $UNPAPER -eq 1 ]; then
      log "Applying unpaper post-processing to image data..."
      PP_PREFIX="unpaper-"
      if [ $VERBOSE = 1 ]; then
        UNPAPERVERBOSE="-v"
      fi
      #runconstrained unpaper $UNPAPERVERBOSE --no-mask-scan --overwrite --dpi $RESOLUTION --no-blackfilter $IMAGE_FILE $PP_PREFIX$IMAGE_FILE | logstdout
      runconstrained unpaper $UNPAPERVERBOSE --overwrite --dpi $RESOLUTION $IMAGE_PATH $IMAGE_DIR/$PP_PREFIX$IMAGE_FILE | logstdout
    fi
    log ""
    log "-------------------------------------------------------------------------------"
    if [ $SEARCHABLE -eq 1 ]; then
      log "Converting image data to searchable pdf..."
      runconstrained tesseract $IMAGE_DIR/$PP_PREFIX$IMAGE_FILE $IMAGE_DIR/${IMAGE_FILE%.*} -l $LANGUAGE pdf | logstdout
    else
      log "Converting image data to pdf..."
      if [ "$PGWIDTHIN" == "" -o "$PGHEIGHTIN" == "" ]; then
        PAGEOPTS="-equalpixels -dpi=$RESOLUTION -noturn"
      else
        PAGEOPTS="-imagewidth $PGWIDTHIN -imageheight $PGHEIGHTIN"
      fi
      PNMVERBOSE=
      # older versions of pnmtops (Ubuntu, Debian) don't have the -verbose option, test for it
      if [[ $VERBOSE = 1 && ! "$(pnmtops -verbose 2>&1 < /dev/null)" =~ "unrecognized option" ]]; then
        PNMVERBOSE="-verbose"
      fi
      log "Using page options: $PAGEOPTS"
      runconstrained pnmtops $PNMVERBOSE $PAGEOPTS $IMAGE_DIR/$PP_PREFIX$IMAGE_FILE | ps2pdf $PS2PDF_OPTS - > $IMAGE_DIR/${IMAGE_FILE%.*}.pdf | logstdout
    fi    
  else
    log "Skipping empty page $IMAGE_FILE with white percentage $PERCENTAGE_WHITE"
  fi

  status=$?
  rm $IMAGE_PATH
  if [ -f $IMAGE_DIR/$PP_PREFIX$IMAGE_FILE ]; then
    rm $IMAGE_DIR/$PP_PREFIX$IMAGE_FILE
  fi

  log ""
  log "Scan processing done, status = $status"
}

if [ $VERBOSE = 1 ]; then
  (
    flock 200
    process_page
  ) 200>$LOCKFILE
else
  process_page
fi;

exit $status