#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

import itertools
import re

from oslo_config import cfg
from oslo_serialization import jsonutils
import six
import yaml

from heat.common import exception
from heat.common.i18n import _

if hasattr(yaml, 'CSafeLoader'):
    yaml_loader = yaml.CSafeLoader
else:
    yaml_loader = yaml.SafeLoader

if hasattr(yaml, 'CSafeDumper'):
    yaml_dumper = yaml.CSafeDumper
else:
    yaml_dumper = yaml.SafeDumper


def _construct_yaml_str(self, node):
    # Override the default string handling function
    # to always return unicode objects
    return self.construct_scalar(node)

yaml_loader.add_constructor(u'tag:yaml.org,2002:str', _construct_yaml_str)
# Unquoted dates like 2013-05-23 in yaml files get loaded as objects of type
# datetime.data which causes problems in API layer when being processed by
# openstack.common.jsonutils. Therefore, make unicode string out of timestamps
# until jsonutils can handle dates.
yaml_loader.add_constructor(u'tag:yaml.org,2002:timestamp',
                            _construct_yaml_str)


def simple_parse(tmpl_str):
    try:
        tpl = jsonutils.loads(tmpl_str)
    except ValueError:
        try:
            tpl = yaml.load(tmpl_str, Loader=yaml_loader)
        except yaml.YAMLError:
            # NOTE(prazumovsky): we need to return more informative error for
            # user, so use SafeLoader, which return error message with template
            # snippet where error has been occurred.
            try:
                tpl = yaml.load(tmpl_str, Loader=yaml.SafeLoader)
            except yaml.YAMLError as yea:
                yea = six.text_type(yea)
                msg = _('Error parsing template: %s') % yea
                raise ValueError(msg)
        else:
            if tpl is None:
                tpl = {}

    if not isinstance(tpl, dict):
        raise ValueError(_('The template is not a JSON object '
                           'or YAML mapping.'))

    return tpl


def validate_template_limit(contain_str):
    """Validate limit for the template.

    Check if the contain exceeds allowed size range.
    """

    if len(contain_str) > cfg.CONF.max_template_size:
        msg = _("Template size (%(actual_len)s bytes) exceeds maximum "
                "allowed size (%(limit)s bytes)."
                ) % {'actual_len': len(contain_str),
                     'limit': cfg.CONF.max_template_size}
        raise exception.RequestLimitExceeded(message=msg)


def parse(tmpl_str):
    """Takes a string and returns a dict containing the parsed structure.

    This includes determination of whether the string is using the
    JSON or YAML format.
    """

    # TODO(ricolin): Move this validation to api side.
    # Validate nested stack template.
    validate_template_limit(six.text_type(tmpl_str))

    tpl = simple_parse(tmpl_str)
    # Looking for supported version keys in the loaded template
    if not ('HeatTemplateFormatVersion' in tpl
            or 'heat_template_version' in tpl
            or 'AWSTemplateFormatVersion' in tpl):
        raise ValueError(_("Template format version not found."))
    return tpl


def convert_json_to_yaml(json_str):
    """Convert AWS JSON template format to Heat YAML format.

    :param json_str: a string containing the AWS JSON template format.
    :returns: the equivalent string containing the Heat YAML format.
    """

    # Replace AWS format version with Heat format version
    json_str = re.sub('"AWSTemplateFormatVersion"\s*:\s*"[^"]+"\s*,',
                      '', json_str)

    # insert a sortable order into the key to preserve file ordering
    key_order = itertools.count()

    def order_key(matchobj):
        key = '%s"__%05d__order__%s" :' % (
            matchobj.group(1),
            next(key_order),
            matchobj.group(2))
        return key
    key_re = re.compile('(\s*)"([^"]+)"\s*:')
    json_str = key_re.sub(order_key, json_str)

    # parse the string as json to a python structure
    tpl = yaml.load(json_str, Loader=yaml_loader)

    # dump python structure to yaml
    tpl["HeatTemplateFormatVersion"] = '2012-12-12'
    yml = yaml.dump(tpl, Dumper=yaml_dumper)

    # remove ordering from key names
    yml = re.sub('__\d*__order__', '', yml)

    # convert integer keys back to string
    yml = re.sub('([\s,{])(\d+)(\s*):', r"\1'\2'\3:", yml)
    return yml
