import logging
import io
import os.path
import tarfile
import base64
from StringIO import StringIO

from github import Github, UnknownObjectException, GithubException
from tempfile import SpooledTemporaryFile

from app import app, userfiles as user_files


client = app.config['HTTPCLIENT']


logger = logging.getLogger(__name__)


TARBALL_MIME = 'application/gzip'
CHUNK_SIZE = 512 * 1024


def should_skip_commit(message):
  return '[skip build]' in message or '[build skip]' in message


class BuildArchiveException(Exception):
  pass

class InvalidServiceException(Exception):
  pass

class TriggerActivationException(Exception):
  pass

class TriggerDeactivationException(Exception):
  pass

class TriggerStartException(Exception):
  pass

class ValidationRequestException(Exception):
  pass

class SkipRequestException(Exception):
  pass

class EmptyRepositoryException(Exception):
  pass

class RepositoryReadException(Exception):
  pass


class BuildTrigger(object):
  def __init__(self):
    pass

  def dockerfile_url(self, auth_token, config):
    """
    Returns the URL at which the Dockerfile for the trigger can be found or None if none/not applicable.
    """
    return None

  def load_dockerfile_contents(self, auth_token, config):
    """
    Loads the Dockerfile found for the trigger's config and returns them or None if none could
    be found/loaded.
    """
    return None

  def list_build_sources(self, auth_token):
    """
    Take the auth information for the specific trigger type and load the
    list of build sources(repositories).
    """
    raise NotImplementedError

  def list_build_subdirs(self, auth_token, config):
    """
    Take the auth information and the specified config so far and list all of
    the possible subdirs containing dockerfiles.
    """
    raise NotImplementedError

  def handle_trigger_request(self, request, auth_token, config):
    """
    Transform the incoming request data into a set of actions. Returns a tuple
    of usefiles resource id, docker tags, build name, and resource subdir.
    """
    raise NotImplementedError

  def is_active(self, config):
    """
    Returns True if the current build trigger is active. Inactive means further
    setup is needed.
    """
    raise NotImplementedError

  def activate(self, trigger_uuid, standard_webhook_url, auth_token, config):
    """ 
    Activates the trigger for the service, with the given new configuration.
    Returns new configuration that should be stored if successful.
    """
    raise NotImplementedError

  def deactivate(self, auth_token, config):
    """
    Deactivates the trigger for the service, removing any hooks installed in
    the remote service. Returns the new config that should be stored if this
    trigger is going to be re-activated.
    """
    raise NotImplementedError

  def manual_start(self, auth_token, config, run_parameters = None):
    """
    Manually creates a repository build for this trigger.
    """
    raise NotImplementedError

  def list_field_values(self, auth_token, config, field_name):
    """
    Lists all values for the given custom trigger field. For example, a trigger might have a
    field named "branches", and this method would return all branches.
    """
    raise NotImplementedError

  @classmethod
  def service_name(cls):
    """
    Particular service implemented by subclasses.
    """
    raise NotImplementedError

  @classmethod
  def get_trigger_for_service(cls, service):
    for subc in cls.__subclasses__():
      if subc.service_name() == service:
        return subc()

    raise InvalidServiceException('Unable to find service: %s' % service)


def raise_unsupported():
  raise io.UnsupportedOperation


class GithubBuildTrigger(BuildTrigger):
  @staticmethod
  def _get_client(auth_token):
    return Github(auth_token, client_id=app.config['GITHUB_CLIENT_ID'],
                  client_secret=app.config['GITHUB_CLIENT_SECRET'])

  @classmethod
  def service_name(cls):
    return 'github'

  def is_active(self, config):
    return 'hook_id' in config

  def activate(self, trigger_uuid, standard_webhook_url, auth_token, config):
    new_build_source = config['build_source']
    gh_client = self._get_client(auth_token)

    try:
      to_add_webhook = gh_client.get_repo(new_build_source)
    except UnknownObjectException:
      msg = 'Unable to find GitHub repository for source: %s'
      raise TriggerActivationException(msg % new_build_source)

    webhook_config = {
      'url': standard_webhook_url,
      'content_type': 'json',
    }

    try:
      hook = to_add_webhook.create_hook('web', webhook_config)
      config['hook_id'] = hook.id
      config['master_branch'] = to_add_webhook.default_branch
    except GithubException:
      msg = 'Unable to create webhook on repository: %s'
      raise TriggerActivationException(msg % new_build_source)

    return config

  def deactivate(self, auth_token, config):
    gh_client = self._get_client(auth_token)

    try:
      repo = gh_client.get_repo(config['build_source'])
      to_delete = repo.get_hook(config['hook_id'])
      to_delete.delete()
    except GithubException:
      msg = 'Unable to remove hook: %s' % config['hook_id']
      raise TriggerDeactivationException(msg)

    config.pop('hook_id', None)

    return config

  def list_build_sources(self, auth_token):
    gh_client = self._get_client(auth_token)
    usr = gh_client.get_user()

    personal = {
      'personal': True,
      'repos': [repo.full_name for repo in usr.get_repos()],
      'info': {
        'name': usr.login,
        'avatar_url': usr.avatar_url,
      }
    }

    repos_by_org = [personal]

    for org in usr.get_orgs():
      repo_list = []
      for repo in org.get_repos(type='member'):
        repo_list.append(repo.full_name)

      repos_by_org.append({
        'personal': False,
        'repos': repo_list,
        'info': {
          'name': org.name,
          'avatar_url': org.avatar_url
        }
      })

    return repos_by_org

  def list_build_subdirs(self, auth_token, config):
    gh_client = self._get_client(auth_token)
    source = config['build_source']

    try:
      repo = gh_client.get_repo(source)
      default_commit = repo.get_branch(repo.default_branch or 'master').commit
      commit_tree = repo.get_git_tree(default_commit.sha, recursive=True)

      return [os.path.dirname(elem.path) for elem in commit_tree.tree
              if (elem.type == u'blob' and
                  os.path.basename(elem.path) == u'Dockerfile')]
    except GithubException as ge:
      message = ge.data.get('message', 'Unable to list contents of repository: %s' % source)
      if message == 'Branch not found':
        raise EmptyRepositoryException()

      raise RepositoryReadException(message)

  def dockerfile_url(self,  auth_token, config):
    source = config['build_source']
    subdirectory = config.get('subdir', '')
    path = subdirectory + '/Dockerfile' if subdirectory else 'Dockerfile'

    gh_client = self._get_client(auth_token)
    try:
      repo = gh_client.get_repo(source)
      master_branch = repo.default_branch or 'master'
      return 'https://github.com/%s/blob/%s/%s' % (source, master_branch, path)
    except GithubException as ge:
      return None

  def load_dockerfile_contents(self, auth_token, config):
    gh_client = self._get_client(auth_token)

    source = config['build_source']
    subdirectory = config.get('subdir', '')
    path = subdirectory + '/Dockerfile' if subdirectory else 'Dockerfile'

    try:
      repo = gh_client.get_repo(source)
      file_info = repo.get_file_contents(path)
      if file_info is None:
        return None

      content = file_info.content
      if file_info.encoding == 'base64':
        content = base64.b64decode(content)
      return content

    except GithubException as ge:
      message = ge.data.get('message', 'Unable to read Dockerfile: %s' % source)
      raise RepositoryReadException(message)

  @staticmethod
  def _prepare_build(config, repo, commit_sha, build_name, ref):
    # Prepare the download and upload URLs
    archive_link = repo.get_archive_link('tarball', commit_sha)
    download_archive = client.get(archive_link, stream=True)

    tarball_subdir = ''
    with SpooledTemporaryFile(CHUNK_SIZE) as tarball:
      for chunk in download_archive.iter_content(CHUNK_SIZE):
        tarball.write(chunk)

      # Seek to position 0 to make tarfile happy
      tarball.seek(0)

      # Pull out the name of the subdir that GitHub generated.
      with tarfile.open(fileobj=tarball) as archive:
        tarball_subdir = archive.getnames()[0]        
        tarball_subdir_info = archive.getmember(tarball_subdir)  

      # Seek to position 0 to make tarfile happy
      tarball.seek(0)

      with SpooledTemporaryFile(CHUNK_SIZE) as updated_tarball:
        def add_entry(arch, dir_path, base_info, contents=None):
          info = tarfile.TarInfo(dir_path)

          info.uid = base_info.uid
          info.gid = base_info.gid
          info.uname = base_info.uname
          info.gname = base_info.gname
          info.mode = base_info.mode
          info.mtime = base_info.mtime

          info.type = tarfile.REGTYPE if contents else tarfile.DIRTYPE
          if contents:
            info.size = len(contents)

          arch.addfile(info, fileobj=StringIO(contents) if contents else None)

        with tarfile.open(fileobj=updated_tarball, mode='w|gz') as updated_archive:
          # Copy existing members of the tar to the updated archive.
          with tarfile.open(fileobj=tarball) as archive:
            for tar_info in archive:
              if tar_info.isreg():
                updated_archive.addfile(tar_info, archive.extractfile(tar_info.name))
              else:
                updated_archive.addfile(tar_info)
          
          # Add the synthetic .git directory to the tarball, containing the commit_sha.
          add_entry(updated_archive, tarball_subdir + '/.git/HEAD', tarball_subdir_info,
                   contents=commit_sha)
          add_entry(updated_archive, tarball_subdir + '/.git/objects/', tarball_subdir_info)
          add_entry(updated_archive, tarball_subdir + '/.git/refs/', tarball_subdir_info)

        # Seek to position 0 to make boto multipart happy
        updated_tarball.seek(0)

        dockerfile_id = user_files.store_file(updated_tarball, TARBALL_MIME)

    logger.debug('Successfully prepared job')

    # compute the tag(s)
    branch = ref.split('/')[-1]
    tags = {branch}
    if branch == repo.default_branch:
      tags.add('latest')
    logger.debug('Pushing to tags: %s' % tags)

    # compute the subdir
    repo_subdir = config['subdir']
    joined_subdir = os.path.join(tarball_subdir, repo_subdir)
    logger.debug('Final subdir: %s' % joined_subdir)

    return dockerfile_id, list(tags), build_name, joined_subdir

  @staticmethod
  def get_display_name(sha):
    return sha[0:7]

  def handle_trigger_request(self, request, auth_token, config):
    payload = request.get_json()
    if not payload or payload.get('head_commit') is None:
      raise SkipRequestException()
    
    if 'zen' in payload:
      raise ValidationRequestException()

    logger.debug('Payload %s', payload)
    ref = payload['ref']
    commit_sha = payload['head_commit']['id']
    commit_message = payload['head_commit'].get('message', '')

    if should_skip_commit(commit_message):
      raise SkipRequestException() 

    short_sha = GithubBuildTrigger.get_display_name(commit_sha)

    gh_client = self._get_client(auth_token)

    repo_full_name = '%s/%s' % (payload['repository']['owner']['name'],
                                payload['repository']['name'])
    repo = gh_client.get_repo(repo_full_name)

    logger.debug('Github repo: %s', repo)

    return GithubBuildTrigger._prepare_build(config, repo, commit_sha,
                                             short_sha, ref)

  def manual_start(self, auth_token, config, run_parameters = None):
    try:
      source = config['build_source']
      run_parameters = run_parameters or {}

      gh_client = self._get_client(auth_token)
      repo = gh_client.get_repo(source)
      master = repo.get_branch(repo.default_branch)
      master_sha = master.commit.sha
      short_sha = GithubBuildTrigger.get_display_name(master_sha)
      ref = 'refs/heads/%s' % (run_parameters.get('branch_name') or repo.default_branch)

      return self._prepare_build(config, repo, master_sha, short_sha, ref)
    except GithubException as ghe:
      raise TriggerStartException(ghe.data['message'])


  def list_field_values(self, auth_token, config, field_name):
    if field_name == 'branch_name':
      gh_client = self._get_client(auth_token)
      source = config['build_source']
      repo = gh_client.get_repo(source)
      branches = [branch.name for branch in repo.get_branches()]

      if not repo.default_branch in branches:
        branches.insert(0, repo.default_branch)

      if branches[0] != repo.default_branch:
        branches.remove(repo.default_branch)
        branches.insert(0, repo.default_branch)

      return branches

    return None