#!/usr/bin/python3

import argparse
import hashlib
import json
import os
import re
import subprocess
import sys
import time


parser = argparse.ArgumentParser(description='iconograph fetcher')
parser.add_argument(
    '--default-rollout',
    dest='default_rollout',
    action='store',
    type=int,
    default=0)
parser.add_argument(
    '--image-dir',
    dest='image_dir',
    action='store',
    required=True)
parser.add_argument(
    '--max-images',
    dest='max_images',
    action='store',
    type=int,
    default=0)
parser.add_argument(
    '--old-manifest',
    dest='old_manifest',
    action='store')
FLAGS = parser.parse_args()


class ManifestBuilder(object):

  _FILE_REGEX = re.compile('^(?P<timestamp>\d+)\.iso$')
  _VOLUME_ID_REGEX = re.compile(b'^Volume id: (?P<volume_id>.+)$', re.MULTILINE)
  _BUF_SIZE = 2 ** 16

  def __init__(self, image_dir, old_manifest):
    self._image_dir = image_dir
    self._old_manifest = old_manifest

  def _OldImages(self):
    if not self._old_manifest:
      return {}
    try:
      with open(self._old_manifest, 'r') as fh:
        parsed = json.load(fh)
        return dict(
            (image['timestamp'], image)
            for image in parsed['images'])
    except FileNotFoundError:
      return {}

  def _GetVolumeID(self, path):
    isoinfo = subprocess.check_output([
      'isoinfo',
      '-d',
      '-i', path,
    ])
    match = self._VOLUME_ID_REGEX.search(isoinfo)
    return match.group('volume_id').decode('ascii')

  def BuildManifest(self):
    ret = {
        'timestamp': int(time.time()),
        'images': [],
    }
    old_images = self._OldImages()
    for filename in os.listdir(self._image_dir):
      match = self._FILE_REGEX.match(filename)
      if not match:
        continue
      timestamp = int(match.group('timestamp'))
      image = {
          'timestamp': timestamp,
          'rollout_‱': FLAGS.default_rollout,
      }
      ret['images'].append(image)

      old_image = old_images.get(timestamp)
      if old_image:
        image.update(old_image)
        continue

      image_path = os.path.join(self._image_dir, filename)

      image['volume_id'] = self._GetVolumeID(image_path)

      with open(image_path, 'rb') as fh:
        hash_obj = hashlib.sha256()
        while True:
          data = fh.read(self._BUF_SIZE)
          if not data:
            break
          hash_obj.update(data)
        image['hash'] = hash_obj.hexdigest()

    ret['images'].sort(key=lambda x: x['timestamp'], reverse=True)
    return ret

  def DeleteOldImages(self, manifest, max_images):
    if not max_images:
      return
    for image in manifest['images'][max_images:]:
      filename = '%d.iso' % image['timestamp']
      print('Deleting old image:', filename, file=sys.stderr)
      path = os.path.join(self._image_dir, filename)
      os.unlink(path)
    manifest['images'] = manifest['images'][:max_images]


def main():
  builder = ManifestBuilder(FLAGS.image_dir, FLAGS.old_manifest)
  manifest = builder.BuildManifest()
  builder.DeleteOldImages(manifest, FLAGS.max_images)
  json.dump(manifest, sys.stdout, sort_keys=True, indent=4)
  sys.stdout.write('\n')


if __name__ == '__main__':
  main()