pdf-fixup

#!/bin/bash

# SPDX-FileCopyrightText: 2021 - 2024 sudorook <daemon@nullcodon.com>
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
# 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, either version 3 of the License, or (at your option)
# any later version.
#
# This program 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 this program. If not, see <https://www.gnu.org/licenses/>.

set -euo pipefail

ROOT="$(dirname "${0}")"

source "${ROOT}"/globals

! check_command awk pdftk pdftoppm pdfinfo convert && exit 3

function adjust_page_numbers {
  local offset
  local length
  offset=$((START - 1))

  awk -i inplace -v s="${START}" -v e="${END}" \
    -f <(cat << EOF
{
  if (a ~ "InfoBegin") {
    getline c
    while (c !~ "InfoValue") {
      if (getline c == 0) break
    }
    a=c
  }
  else if (a ~ "PageMediaBegin") {
    if (e == "end") {
      if (\$2 >= s) {
        print a
        print
        getline c
        while (c !~ "Begin") {
          print c
          if (getline c == 0) break
        }
        a=c
      } else {
        getline c
        while (c !~ "Begin") {
          if (getline c == 0) break
        }
        a=c
      }
    }
    else {
      if ((\$2 >= s) && (\$2 <= e)) {
        print a
        print
        getline c
        while (c !~ "Begin") {
          print c
          if (getline c == 0) break
        }
        a=c
      } else {
        getline c
        while (c !~ "Begin") {
          if (getline c == 0) break
        }
        a=c
      }
    }
  }
  else if (a ~ "PageLabelBegin") {
    b=\$0
    if (e == "end") {
      if (\$2 >= s) {
        print a
        print b
        getline c
        while (c !~ "NumStyle") {
          print c
          if (getline c == 0) break
        }
        print c
        getline a
      } else {
        getline c
        while (c !~ "NumStyle") {
          if (getline c == 0) break
        }
        getline a
      }
    }
    else {
      if ((\$2 >= s) && (\$2 <= e)) {
        print a
        print b
        getline c
        while (c !~ "NumStyle") {
          print c
          if (getline c == 0) break
        }
        print c
        getline a
      } else {
        getline c
        while (c !~ "NumStyle") {
          if (getline c == 0) break
        }
        getline a
      }
    }
  }
  else if (a ~ "BookmarkBegin") {
    b=\$0
    getline c
    getline
    if (e == "end") {
      if (\$2 >= s) {
        print a; print b; print c; print;
      }
    }
    else {
      if ((\$2 >= s) && (\$2 <= e)) {
        print a; print b; print c; print;
      }
    }
    a=\$0
    # getline a
  }
  else {
    if (\$1 !~ "Begin\$") {
      print
    }
    a=\$0
  }
}
EOF
    ) "${DATA}"

  sed -i \
    -e '/^PageMedia\(Rect\|Dimensions\):/s/,//g' \
    -e 's/-0.[0-9]\+/0/g' "${DATA}"

  # Offset the page number metadata
  awk -i inplace -v d="${offset}" '/BookmarkPageNumber:/{$2-=d}1' "${DATA}"
  awk -i inplace -v d="${offset}" '/PageMediaNumber:/{$2-=d}1' "${DATA}"
  awk -i inplace -v d="${offset}" '/PageLabelNewIndex:/{$2-=d}1' "${DATA}"

  if [[ "${END}" = end ]]; then
    length="$(sed -n "s/^NumberOfPages: \([0-9]\+\)$/\1/p" "${DATA}")"
    length="$((length - offset))"
    sed -i "s/^NumberOfPages: \([0-9]\+\)$/NumberOfPages: ${length}/g" "${DATA}"
  else
    length="$((END - offset))"
    sed -i "s/^NumberOfPages: \([0-9]\+\)$/NumberOfPages: ${length}/g" "${DATA}"
  fi
}

function clean_meta_tags {
  sed -i \
    -e "/InfoBegin/,+2d" \
    -e "/PdfID0/d" \
    -e "/PdfID1/d" \
    -e "s/
//g" \
    -e "/^$/d" \
    -e "/^BookmarkTitle:/N;s/\n\?\(\nBookmarkLevel.*\)\?/\1/g" \
    -e "/^BookmarkTitle:/s/\t\+/\ /g" \
    -e "s/\(\ \ \+\)/\ /g" \
    "${DATA}"
}

function compare_page_dimensions {
  local in="${1}"
  local p1="${2}"
  local p2="${3}"
  local p1_size
  local p2_size
  p1_size="$(pdfinfo -f "${p1}" -l "${p1}" "${1}" |
             sed -n "s/^Page.*size:\ \+\(.*\)/\1/p")"
  p2_size="$(pdfinfo -f "${p2}" -l "${p2}" "${1}" |
             sed -n "s/^Page.*size:\ \+\(.*\)/\1/p")"

  [[ "${p1_size}" = "${p2_size}" ]] && return 0 || return 1
}

function normalize_cover {
  # Assumes the first page is the cover and the reference page is the 10th one.
  local in
  local dir="${BUILD}"
  local p01="${START}"
  local p01_file
  # local p01_size
  local p10="$((START + 10))"
  local p10_file
  local p10_size
  local pend="${END}"
  local pend_file

  if compare_page_dimensions "${TMP}" 1 10; then
    show_info "No page normalization needed."
  else
    show_info "Different cover dimensions detected. Normalizing..."
    pushd "${dir}" > /dev/null
    in="$(basename "${TMP}")"
    p01_file="${in%.*}-01"
    p10_file="${in%.*}-10"
    pend_file="${in%.*}-$((p01 + 1))_end"

    pdftk "${TMP}" cat "${p01}" output "${p01_file}.pdf"
    pdftk "${TMP}" cat "${p10}" output "${p10_file}.pdf"
    pdftk "${TMP}" cat "$((p01 + 1))-${pend}" output "${pend_file}.pdf"

    pdftoppm "${p01_file}.pdf" "${p01_file}" -png -singlefile
    pdftoppm "${p10_file}.pdf" "${p10_file}" -png -singlefile

    # p01_size="$(file -b "${p01_file}.png" | cut -d "," -f 2 | tr -d "[:space:]")"
    p10_size="$(file -b "${p10_file}.png" | cut -d "," -f 2 | tr -d "[:space:]")"

    convert "${p01_file}.png" -resize "${p10_size}!" "${p01_file}v2.png"
    convert "${p01_file}v2.png" "${p01_file}v2.pdf"

    pdftk "${p01_file}v2.pdf" "${pend_file}.pdf" cat output "${in}"
    popd > /dev/null
  fi
}

function print_usage {
  show_header "Usage: pdf-fixup"
  show_listitem "  -s|--start      first page number (default: 1)"
  show_listitem "  -e|--end        last page number (default: end)"
  show_listitem "  -k|--keep       flag to keep intermediate files (default: false)"
  show_listitem "  -o|--output     output file name (optional)"
  show_listitem "  -n|--normalize  resize 1st page to match others (default: false)"
}

START=1
END=end
KEEP=false
NORMALIZE=false

OPTIONS=e:hkno:s:
LONGOPTIONS=end:,help,keep,normalize,output:,start:
PARSED=$(getopt -o "${OPTIONS}" --long "${LONGOPTIONS}" -n "${0}" -- "${@}")
eval set -- "${PARSED}"

while [ ${#} -ge 1 ]; do
  case ${1} in
    -e | --end)
      END="${2}"
      shift 2
      ;;
    -h | --help)
      print_usage
      exit
      ;;
    -k | --keep)
      KEEP=true
      shift 1
      ;;
    -o | --output)
      OUTPUT="${2}"
      shift
      ;;
    -s | --start)
      START="${2}"
      shift 2
      ;;
    -n | --normalize)
      NORMALIZE=true
      shift 1
      ;;
    --)
      shift
      break
      ;;
    *)
      show_error "ERROR: invalid flag."
      exit 3
      ;;
  esac
done

if [[ ${#} -ne 1 ]]; then
  show_error "ERROR: please specify 1 input file."
  exit 3
else
  if ! [ -f "${1}" ]; then
    show_error "ERROR: input '${1}' not found. Exiting."
    exit 3
  fi
  if ! [[ "$(file -b "${1}")" =~ ^PDF ]]; then
    show_error "ERROR: input '${1}' is not a PDF. Exiting."
    exit 3
  fi
  INPUT="${1}"
  NAME=${1%.*}
  EXTENSION=${1##*.}
fi

if ! [[ -v OUTPUT ]]; then
  OUTPUT="${NAME} new.${EXTENSION}"
fi

BUILD="$(mktemp -d)"
TMP="${BUILD}/tmp-$$.pdf"
DATA="${BUILD}/data-$$.txt"
trap 'rm -rf "${BUILD}"; exit' INT TERM ERR EXIT

# Force UTF-8 locale, if possible.
LANG="$(locale -a | grep "utf-\?8" | head -n 1)"
if [ -n "${LANG}" ]; then
  export LC_ALL="${LANG}"
else
  show_warning "Failed to force UTF-8 locale."
fi

pdftk "${INPUT}" cat "${START}"-"${END}" output "${TMP}"
pdftk "${INPUT}" dump_data_utf8 output "${DATA}"

clean_meta_tags
adjust_page_numbers
"${NORMALIZE}" && normalize_cover

if ! ${KEEP}; then
  pdftk "${TMP}" update_info_utf8 "${DATA}" output "${OUTPUT}"
  rm -f "${TMP}" "${DATA}"
else
  mv "${TMP}" "$(basename "${TMP}")"
  mv "${DATA}" "$(basename "${DATA}")"
  TMP="$(basename "${TMP}")"
  DATA="$(basename "${DATA}")"
  show_info "To re-assemble, run:" >&2
  show_listitem "pdftk ${TMP@Q} update_info_utf8 ${DATA@Q} output ${OUTPUT@Q} && rm ${TMP@Q} ${DATA@Q}" >&2
fi