#!/usr/bin/env python2.7
from __future__ import absolute_import, unicode_literals, print_function, division

from sys import argv
from os import environ, stat, remove as _delete_file
from os.path import isfile
from hashlib import sha256
from subprocess import check_call as run

from boto.s3.connection import S3Connection
from boto.s3.key import Key
from boto.exception import S3ResponseError


NODE_MODULES_TARBALL = 'node_modules.tar.gz'
NEED_TO_UPLOAD_MARKER = '.need-to-upload'
BYTES_PER_MB = 1024 * 1024
try:
    BUCKET_NAME = environ['TWBS_S3_BUCKET']
except KeyError:
    raise SystemExit("TWBS_S3_BUCKET environment variable not set!")


def _sha256_of_file(filename):
    hasher = sha256()
    with open(filename, 'rb') as input_file:
        hasher.update(input_file.read())
    return hasher.hexdigest()


def _delete_file_quietly(filename):
    try:
        _delete_file(filename)
    except (OSError, IOError):
        pass


def _tarball_size():
    kib = stat(NODE_MODULES_TARBALL).st_size // BYTES_PER_MB
    return "{} MiB".format(kib)


if __name__ == '__main__':
    # Uses environment variables:
    #   AWS_ACCESS_KEY_ID - AWS Access Key ID
    #   AWS_SECRET_ACCESS_KEY - AWS Secret Access Key
    argv.pop(0)
    if len(argv) != 1:
        raise SystemExit("USAGE: node_modules_cache.py <download | upload>")
    mode = argv.pop()

    conn = S3Connection()
    bucket = conn.lookup(BUCKET_NAME)
    if bucket is None:
        raise SystemExit("Could not access bucket!")

    package_json_hash = _sha256_of_file('package.json')
    print('sha256(package.json) = ' + package_json_hash)

    key = Key(bucket, package_json_hash)
    key.storage_class = 'REDUCED_REDUNDANCY'

    if mode == 'download':
        _delete_file_quietly(NEED_TO_UPLOAD_MARKER)
        try:
            print("Downloading tarball from S3...")
            key.get_contents_to_filename(NODE_MODULES_TARBALL)
        except S3ResponseError as err:
            open(NEED_TO_UPLOAD_MARKER, 'a').close()
            print(err)
            raise SystemExit("Cached node_modules download failed!")
        print("Downloaded {}.".format(_tarball_size()))
        print("Extracting tarball...")
        run(['tar', 'xzf', NODE_MODULES_TARBALL])
        print("node_modules successfully installed from cache.")
    elif mode == 'upload':
        if isfile(NEED_TO_UPLOAD_MARKER):
            print("Creating tarball...")
            run(['tar', 'czf', NODE_MODULES_TARBALL, 'node_modules'])
            print("Uploading tarball to S3... ({})".format(_tarball_size()))
            key.set_contents_from_filename(NODE_MODULES_TARBALL)
            print("node_modules cache successfully updated.")
            _delete_file_quietly(NEED_TO_UPLOAD_MARKER)
        else:
            print("No need to upload anything.")
    else:
        raise SystemExit("Unrecognized mode {!r}".format(mode))