#!/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 [[ $# < 1 ]]; then
  usage
  exit 1
fi

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

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

TIMEVERBOSE=
if [[ $VERBOSE == 1 ]]; then
  TIMEVERBOSE=time
fi

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

  if [[ $SKIP_EMPTY_PAGES == 1 ]]; then
    PERCENTAGE_WHITE=$(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 [[ $SKIP_EMPTY_PAGES == 1 && $(echo "$PERCENTAGE_WHITE > 99.8" | bc -l) == 1 ]]; then
    log "Skipping empty page $IMAGE_FILE with white percentage $PERCENTAGE_WHITE"
  else
    if [[ $UNPAPER == 1 ]]; then
      log "Applying unpaper post-processing to image data..."
      PP_PREFIX="unpaper-"
      if [[ $VERBOSE == 1 ]]; then
        UNPAPERVERBOSE="-v"
      fi
      #runconstrained $TIMEVERBOSE unpaper $UNPAPERVERBOSE --no-mask-scan --overwrite --dpi $RESOLUTION --no-blackfilter $IMAGE_FILE $PP_PREFIX$IMAGE_FILE | logstdout
      runconstrained $TIMEVERBOSE unpaper $UNPAPERVERBOSE --overwrite --dpi $RESOLUTION $IMAGE_PATH $IMAGE_DIR/$PP_PREFIX$IMAGE_FILE | logstdout
    fi
    if [[ $SEARCHABLE == 1 ]]; then
      log "Converting image data to searchable pdf..."
      # tesseract uses the input's DPI header, we need to convert to a format that supports this (like tiff)
      log "...Running convert"
      runconstrained $TIMEVERBOSE convert -density ${RESOLUTION}x${RESOLUTION} -units PixelsPerInch $IMAGE_DIR/$PP_PREFIX$IMAGE_FILE $IMAGE_DIR/$PP_PREFIX${IMAGE_FILE}.tiff | logstdout
      log "...Running tesseract"
      runconstrained $TIMEVERBOSE tesseract $IMAGE_DIR/$PP_PREFIX${IMAGE_FILE}.tiff $IMAGE_DIR/${IMAGE_FILE%.*} -l $LANGUAGE pdf | logstdout
      [[ -f $IMAGE_DIR/$PP_PREFIX${IMAGE_FILE}.tiff ]] && rm $IMAGE_DIR/$PP_PREFIX${IMAGE_FILE}.tiff
    else
      log "Converting image data to pdf..."
      if [[ "$PGWIDTHIN" == "" || "$PGHEIGHTIN" == "" ]]; then
        PAGEOPTS="-equalpixels -dpi=$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 "...Running pnmtops on $IMAGE_DIR/$PP_PREFIX$IMAGE_FILE using page options: $PAGEOPTS"
      runconstrained $TIMEVERBOSE pnmtops $PNMVERBOSE $PAGEOPTS $IMAGE_DIR/$PP_PREFIX$IMAGE_FILE > $IMAGE_DIR/${IMAGE_FILE}.ps | logstdout
      log "...Running ps2pdf on $IMAGE_DIR/${IMAGE_FILE}.ps"
      runconstrained $TIMEVERBOSE ps2pdf $PS2PDF_OPTS $IMAGE_DIR/${IMAGE_FILE}.ps $IMAGE_DIR/${IMAGE_FILE}.pdf | logstdout
      [[ -f $IMAGE_DIR/${IMAGE_FILE}.ps ]] && rm $IMAGE_DIR/$PP_PREFIX${IMAGE_FILE}.ps
    fi    
  fi

  status=$?
  rm $IMAGE_PATH
  [[ -f $IMAGE_DIR/$PP_PREFIX${IMAGE_FILE} ]] && rm $IMAGE_DIR/$PP_PREFIX${IMAGE_FILE}

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

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

exit $status