#!/usr/bin/env python3

## Copyright 2015, 2019-2020 Codethink Limited

# gzip archive frontend for git-fast-import

from gzip import GzipFile
import os.path
import struct
import subprocess
import sys


branch_name = 'master'
branch_ref = 'refs/heads/%s' % branch_name
committer_name = 'Lorry Gzip Importer'
committer_email = 'lorry-gzip-importer@lorry'


# The size of a gzip file is stored in the last 4 bytes
def uncompressedsize(filename):
    with open(filename, 'rb') as f:
        f.seek(-4, 2)
        return struct.unpack('I', f.read(4))[0]


def export(zipfile, fast_import):
    def printlines(list):
        for str in list:
            fast_import.write(str.encode('utf-8') + b"\n")

    # Gzip does have an encoded mtime, however Python's GzipFile
    # just ignores it, so we just yank the mtime of the zip file itself.
    mtime = os.path.getmtime(zipfile);
    file_size = uncompressedsize (zipfile);
    zip = GzipFile(zipfile, 'rb')

    printlines(('blob', 'mark :1', 'data ' + str(file_size)))
    fast_import.write(zip.read() + b"\n")

    committer = committer_name + ' <' + committer_email + '> %d +0000' % \
        mtime

    zipfile_basename = os.path.basename(zipfile)
    printlines(('commit ' + branch_ref, 'committer ' + committer, \
        'data <<EOM', 'Imported from ' + zipfile_basename + '.', 'EOM', \
        '', 'deleteall'))

    last_dot = zipfile_basename[:-1].rfind('.')
    unzipped_file = zipfile_basename[:last_dot]
    printlines(('M 100644 :1 ' + unzipped_file,));

    zipname, _ = os.path.splitext(zipfile_basename)
    printlines(('',  'tag ' + zipname, \
        'from ' + branch_ref, 'tagger ' + committer, \
        'data <<EOM', 'Package ' + zipfile, 'EOM', ''))


def main():
    if len(sys.argv) < 2:
        print('usage:', sys.argv[0], '<gzipfile>...')
        sys.exit(1)

    with subprocess.Popen('git fast-import --quiet', shell=True,
                          stdin=subprocess.PIPE) as import_proc:
        for zipfile in sys.argv[1:]:
            export(zipfile, import_proc.stdin)
        import_proc.stdin.close()
        if import_proc.wait() != 0:
            sys.exit(1)


main()