import cStringIO
import hashlib
import json
import requests
import tarfile
import urlparse
import uuid

from deis import settings


def publish_release(repository_path, config, tag):
	"""
	Publish a new release as a Docker image

	Given a source repository path, a dictionary of environment variables
	and a target tag, create a new lightweight Docker image on the registry.

	For example, publish_release('gabrtv/myapp', {'ENVVAR': 'values'}, 'v23')
	results in a new Docker image at: <registry_url>/gabrtv/myapp:v23
	which contains the new configuration as ENV entries.
	"""
	image_id = _get_tag(repository_path, 'latest')
	image = _get_image(image_id)
	# construct the new image
	image['parent'] = image['id']
	image['id'] = _new_id()
	image['config']['Env'] = _construct_env(image['config']['Env'], config)
	# update and tag the new image
	_put_image(image)
	cookies = _put_layer(image['id'], _empty_tar_archive())
	_put_checksum(image, cookies)
	_put_tag(image['id'], repository_path, tag)


# registry access


def _get_tag(repository, tag):
	path = "/v1/repositories/{repository}/tags/{tag}".format(**locals())
	url = urlparse.urljoin(settings.REGISTRY_URL, path)
	r = requests.get(url)
	if not r.status_code == 200:
		raise RuntimeError("GET Image Error ({}: {})".format(r.status_code, r.text))
	print r.text
	return r.json()


def _get_image(image_id):
	path = "/v1/images/{image_id}/json".format(**locals())
	url = urlparse.urljoin(settings.REGISTRY_URL, path)
	r = requests.get(url)
	if not r.status_code == 200:
		raise RuntimeError("GET Image Error ({}: {})".format(r.status_code, r.text))
	return r.json()


def _put_image(image):
	path = "/v1/images/{id}/json".format(**image)
	url = urlparse.urljoin(settings.REGISTRY_URL, path)
	r = requests.put(url, data=json.dumps(image))
	if not r.status_code == 200:
		raise RuntimeError("PUT Image Error ({}: {})".format(r.status_code, r.text))
	return r.json()


def _put_layer(image_id, layer_fileobj):
	path = "/v1/images/{image_id}/layer".format(**locals())
	url = urlparse.urljoin(settings.REGISTRY_URL, path)
	r = requests.put(url, data=layer_fileobj.read())
	if not r.status_code == 200:
		raise RuntimeError("PUT Layer Error ({}: {})".format(r.status_code, r.text))
	return r.cookies


def _put_checksum(image, cookies):
	path = "/v1/images/{id}/checksum".format(**image)
	url = urlparse.urljoin(settings.REGISTRY_URL, path)
	tarsum = TarSum(json.dumps(image)).compute()
	headers = {'X-Docker-Checksum': tarsum}
	r = requests.put(url, headers=headers, cookies=cookies)
	if not r.status_code == 200:
		raise RuntimeError("PUT Checksum Error ({}: {})".format(r.status_code, r.text))
	print r.json()


def _put_tag(image_id, repository_path, tag):
	path = "/v1/repositories/{repository_path}/tags/{tag}".format(**locals())
	url = urlparse.urljoin(settings.REGISTRY_URL, path)
	r = requests.put(url, data=json.dumps(image_id))
	if not r.status_code == 200:
		raise RuntimeError("PUT Tag Error ({}: {})".format(r.status_code, r.text))
	print r.json()


# utility functions


def _construct_env(env, config):
	"Update current environment with latest config"
	new_env = []
	# see if we need to update existing ENV vars
	for e in env:
		k, v = e.split('=', 1)
		if k in config:
			# update values defined by config
			v = config.pop(k)
			new_env.append("{}={}".format(k, v))
	# add other config ENV items
	for k, v in config.items():
		new_env.append("{}={}".format(k, v))
	return new_env


def _new_id():
	"Return 64-char UUID for use as Image ID"
	return ''.join(uuid.uuid4().hex * 2)


def _empty_tar_archive():
	"Return an empty tar archive (in memory)"
	data = cStringIO.StringIO()
	tar = tarfile.open(mode="w", fileobj=data)
	tar.close()
	data.seek(0)
	return data


#
# Below adapted from https://github.com/dotcloud/docker-registry/blob/master/lib/checksums.py
#

def sha256_file(fp, data=None):
	h = hashlib.sha256(data or '')
	if not fp:
		return h.hexdigest()
	while True:
		buf = fp.read(4096)
		if not buf:
			break
		h.update(buf)
	return h.hexdigest()


def sha256_string(s):
	return hashlib.sha256(s).hexdigest()


class TarSum(object):

	def __init__(self, json_data):
		self.json_data = json_data
		self.hashes = []
		self.header_fields = ('name', 'mode', 'uid', 'gid', 'size', 'mtime',
                              'type', 'linkname', 'uname', 'gname', 'devmajor',
                              'devminor')

	def append(self, member, tarobj):
		header = ''
		for field in self.header_fields:
			value = getattr(member, field)
			if field == 'type':
				field = 'typeflag'
			elif field == 'name':
				if member.isdir() and not value.endswith('/'):
					value += '/'
			header += '{0}{1}'.format(field, value)
		h = None
		try:
			if member.size > 0:
				f = tarobj.extractfile(member)
				h = sha256_file(f, header)
			else:
				h = sha256_string(header)
		except KeyError:
			h = sha256_string(header)
		self.hashes.append(h)

	def compute(self):
		self.hashes.sort()
		data = self.json_data + ''.join(self.hashes)
		tarsum = 'tarsum+sha256:{0}'.format(sha256_string(data))
		return tarsum