#!/usr/bin/env python3
# A command tool that use PyPDF2 to merge pdf files
# Usage: python3 pdf_merge.py -i file1.pdf,1-3 file2.pdf -o output.pdf
# -i: input pdf file, followed by the page range to merge, the page range is separated by '-' and it is optional, if not provided, merge all pages
#     e.g. file1.pdf,1-3, merge page 1 to 3 of file1.pdf, file2.pdf, merge all pages of file2.pdf
# -o: output pdf file
# author: Ryan <ouyang.em@gmail.com>

import argparse
from PyPDF2 import PdfFileMerger


def merge_pdf(input_files, output_file):
  merger = PdfFileMerger()
  for input_file in input_files:
    file_name, *page_range = input_file.split(',')
    if page_range:
      start, end = map(int, page_range[0].split('-'))
      merger.append(file_name, pages=(start - 1, end))
    else:
      merger.append(file_name)
  merger.write(output_file)
  merger.close()


if __name__ == '__main__':
  parser = argparse.ArgumentParser(description='Merge PDF files')
  parser.add_argument('-i', '--input', nargs='+', help='Input PDF files')
  parser.add_argument('-o', '--output', help='Output PDF file')
  args = parser.parse_args()
  merge_pdf(args.input, args.output)