#!/usr/bin/env python

"""Retrieves commit contents in a patch format.

Check README.md for usage examples or run it with `-h` argument to get an interface reference.
"""

import argparse
import os
import sys

from lib.git import get_patch as git_get_patch


def parse_args():
  parser = argparse.ArgumentParser(
      description='Get a commit contents in a patch format.')

  parser.add_argument('-c', '--commit', nargs='+', required=True,
                      help='Commit hash(es).')
  parser.add_argument('-f', '--filename', nargs='*', required=False,
                      help='Filename(s) for a patch file(s). Defaults to something like {0}.'
                      .format(get_default_patch_file_name(
                          '4b825dc642cb6eb9a060e54bf8d69288fbee4904')))
  parser.add_argument('-o', '--output-dir', required=False,
                      help='Folder to save the patch in. Defaults to a current folder.')
  parser.add_argument('-r', '--repo', required=True,
                      help='Path to a repository root folder.')

  args = parser.parse_args()

  # Additional rules
  if args.filename is not None and (len(args.commit) != len(args.filename)):
    parser.error("Number of filenames ({0}) must be equal to number of commits ({1})."
        .format(len(args.filename), len(args.commit)))

  return args


def get_default_patch_file_name(commit_hash):
  template = 'backport_{commit_hash}.patch'

  number_of_hash_characters_to_preserve = 8
  commit_hash_string = commit_hash[:number_of_hash_characters_to_preserve+1]

  patch_file_name = template.format(
      commit_hash=commit_hash_string)

  return patch_file_name


def get_output_path(output_dir, output_filename, commit_hash):
  if (output_dir is None) and (output_filename is None):
    return None

  # Use current dir as a default.
  if output_dir is None:
    output_dir = '.'

  # Use the default filename if it's not provided.
  if output_filename is None:
    output_filename = get_default_patch_file_name(commit_hash)

  output_path = os.path.join(output_dir, output_filename)
  return output_path


def save_to_file(data, file_path):
  with open(file_path, 'w') as f:
    f.write(data)


def process_patch(repo, commit_hash, output_path=None):
  patch_contents = git_get_patch(repo, commit_hash)

  if output_path is None:
    sys.stdout.write(patch_contents)
  else:
    save_to_file(data=patch_contents, file_path=output_path)


def main():
  args = parse_args()

  commits = args.commit
  filenames = args.filename

  # (alexeykuzmin): Ugly hack alert.
  if filenames is None:
    filenames = [None] * len(commits)

  for (commit, filename) in zip(commits, filenames):
    output_path = get_output_path(args.output_dir, filename,
                                  commit_hash=commit)
    process_patch(args.repo, commit, output_path)

  return 0


if __name__ == '__main__':
  sys.exit(main())