# vim: tabstop=4 shiftwidth=4 softtabstop=4

#
#    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 functools
import webob

from heat.common import context
from heat.db import api as db_api
from heat.engine import api
from heat.engine import identifier
from heat.engine import parser
from heat.engine import watchrule

from heat.openstack.common import cfg
from heat.openstack.common import log as logging
from heat.openstack.common import threadgroup
from heat.openstack.common.gettextutils import _
from heat.openstack.common.rpc import service


logger = logging.getLogger(__name__)


def request_context(func):
    @functools.wraps(func)
    def wrapped(self, ctx, *args, **kwargs):
        if ctx is not None and not isinstance(ctx, context.RequestContext):
            ctx = context.RequestContext.from_dict(ctx.to_dict())
        return func(self, ctx, *args, **kwargs)
    return wrapped


class EngineService(service.Service):
    """
    Manages the running instances from creation to destruction.
    All the methods in here are called from the RPC backend.  This is
    all done dynamically so if a call is made via RPC that does not
    have a corresponding method here, an exception will be thrown when
    it attempts to call into this class.  Arguments to these methods
    are also dynamically added and will be named as keyword arguments
    by the RPC caller.
    """
    def __init__(self, host, topic, manager=None):
        super(EngineService, self).__init__(host, topic)
        # stg == "Stack Thread Groups"
        self.stg = {}

    def _start_in_thread(self, stack_id, stack_name, func, *args, **kwargs):
        if stack_id not in self.stg:
            thr_name = '%s-%s' % (stack_name, stack_id)
            self.stg[stack_id] = threadgroup.ThreadGroup(thr_name)
        self.stg[stack_id].add_thread(func, *args, **kwargs)

    def _timer_in_thread(self, stack_id, stack_name, func, *args, **kwargs):
        """
        Define a periodic task, to be run in a separate thread, in the stack
        threadgroups.  Periodicity is cfg.CONF.periodic_interval
        """
        if stack_id not in self.stg:
            thr_name = '%s-%s' % (stack_name, stack_id)
            self.stg[stack_id] = threadgroup.ThreadGroup(thr_name)
        self.stg[stack_id].add_timer(cfg.CONF.periodic_interval,
                                     func, *args, **kwargs)

    def _service_task(self):
        """
        This is a dummy task which gets queued on the service.Service
        threadgroup.  Without this service.Service sees nothing running
        i.e has nothing to wait() on, so the process exits..
        This could also be used to trigger periodic non-stack-specific
        housekeeping tasks
        """
        pass

    def start(self):
        super(EngineService, self).start()

        # Create dummy service task, because when there is nothing queued
        # on self.tg the process exits
        self.tg.add_timer(cfg.CONF.periodic_interval,
                          self._service_task)

        # Create a periodic_watcher_task per-stack
        admin_context = context.get_admin_context()
        stacks = db_api.stack_get_all(admin_context)
        for s in stacks:
            self._timer_in_thread(s.id, s.name,
                                  self._periodic_watcher_task,
                                  sid=s.id)

    @request_context
    def identify_stack(self, context, stack_name):
        """
        The identify_stack method returns the full stack identifier for a
        single, live stack given the stack name.
        arg1 -> RPC context.
        arg2 -> Name or UUID of the stack to look up.
        """
        if identifier.HeatIdentifier.is_uuid(stack_name):
            s = db_api.stack_get(context, stack_name)
        else:
            s = db_api.stack_get_by_name(context, stack_name)
        if s:
            stack = parser.Stack.load(context, stack=s)
            return dict(stack.identifier())
        else:
            raise AttributeError('Unknown stack name')

    def _get_stack(self, context, stack_identity):
        identity = identifier.HeatIdentifier(**stack_identity)

        if identity.tenant != context.tenant_id:
            raise AttributeError('Invalid tenant')

        s = db_api.stack_get(context, identity.stack_id)

        if s is None:
            raise AttributeError('Stack not found')

        if identity.path or s.name != identity.stack_name:
            raise AttributeError('Invalid stack ID')

        return s

    @request_context
    def show_stack(self, context, stack_identity):
        """
        The show_stack method returns the attributes of one stack.
        arg1 -> RPC context.
        arg2 -> Name of the stack you want to see
        """
        if stack_identity is None:
            raise AttributeError('No stack_identity provided')

        stacks = [self._get_stack(context, stack_identity)]

        def format_stack_detail(s):
            stack = parser.Stack.load(context, stack=s)
            return api.format_stack(stack)

        return {'stacks': [format_stack_detail(s) for s in stacks]}

    @request_context
    def list_stacks(self, context):
        """
        The list_stacks method returns attributes of all stacks.
        arg1 -> RPC context.
        """
        stacks = db_api.stack_get_all_by_tenant(context) or []

        def format_stack_detail(s):
            stack = parser.Stack.load(context, stack=s, resolve_data=False)
            return api.format_stack(stack)

        return {'stacks': [format_stack_detail(s) for s in stacks]}

    @request_context
    def create_stack(self, context, stack_name, template, params, args):
        """
        The create_stack method creates a new stack using the template
        provided.
        Note that at this stage the template has already been fetched from the
        heat-api process if using a template-url.
        arg1 -> RPC context.
        arg2 -> Name of the stack you want to create.
        arg3 -> Template of stack you want to create.
        arg4 -> Stack Input Params
        arg4 -> Request parameters/args passed from API
        """
        logger.info('template is %s' % template)

        if db_api.stack_get_by_name(context, stack_name):
            raise AttributeError('Stack already exists with that name')

        tmpl = parser.Template(template)

        # Extract the template parameters, and any common query parameters
        template_params = parser.Parameters(stack_name, tmpl, params)
        common_params = api.extract_args(args)

        stack = parser.Stack(context, stack_name, tmpl, template_params,
                             **common_params)

        response = stack.validate()
        if response:
            return {'Description': response}

        stack_id = stack.store()

        self._start_in_thread(stack_id, stack_name, stack.create)

        # Schedule a periodic watcher task for this stack
        self._timer_in_thread(stack_id, stack_name,
                              self._periodic_watcher_task,
                              sid=stack_id)

        return dict(stack.identifier())

    @request_context
    def update_stack(self, context, stack_identity, template, params, args):
        """
        The update_stack method updates an existing stack based on the
        provided template and parameters.
        Note that at this stage the template has already been fetched from the
        heat-api process if using a template-url.
        arg1 -> RPC context.
        arg2 -> Name of the stack you want to create.
        arg3 -> Template of stack you want to create.
        arg4 -> Stack Input Params
        arg4 -> Request parameters/args passed from API
        """
        logger.info('template is %s' % template)

        # Get the database representation of the existing stack
        db_stack = self._get_stack(context, stack_identity)

        current_stack = parser.Stack.load(context, stack=db_stack)

        # Now parse the template and any parameters for the updated
        # stack definition.
        tmpl = parser.Template(template)
        stack_name = current_stack.name
        template_params = parser.Parameters(stack_name, tmpl, params)
        common_params = api.extract_args(args)

        updated_stack = parser.Stack(context, stack_name, tmpl,
                                     template_params, **common_params)

        response = updated_stack.validate()
        if response:
            return {'Description': response}

        self._start_in_thread(db_stack.id, db_stack.name,
                              current_stack.update,
                              updated_stack)

        return dict(current_stack.identifier())

    @request_context
    def validate_template(self, context, template):
        """
        The validate_template method uses the stack parser to check
        the validity of a template.

        arg1 -> RPC context.
        arg3 -> Template of stack you want to create.
        arg4 -> Stack Input Params
        """
        logger.info('validate_template')
        if template is None:
            msg = _("No Template provided.")
            return webob.exc.HTTPBadRequest(explanation=msg)

        tmpl = parser.Template(template)
        resources = template.get('Resources', [])

        if not resources:
            return {'Error': 'At least one Resources member must be defined.'}

        for res in resources.values():
            if not res.get('Type'):
                return {'Error':
                        'Every Resources object must contain a Type member.'}

        def describe_param(p):
            description = {'NoEcho': p.no_echo() and 'true' or 'false',
                           'ParameterKey': p.name,
                           'Description': p.description()}
            if p.has_default():
                description['DefaultValue'] = p.default()

            return description

        params = parser.Parameters(None, tmpl).map(describe_param)

        result = {
            'Description': template.get('Description', ''),
            'Parameters': params.values(),
        }
        return result

    @request_context
    def get_template(self, context, stack_identity):
        """
        Get the template.
        arg1 -> RPC context.
        arg2 -> Name of the stack you want to see.
        """
        s = self._get_stack(context, stack_identity)
        if s:
            return s.raw_template.template
        return None

    @request_context
    def delete_stack(self, context, stack_identity):
        """
        The delete_stack method deletes a given stack.
        arg1 -> RPC context.
        arg2 -> Name of the stack you want to delete.
        """
        st = self._get_stack(context, stack_identity)

        logger.info('deleting stack %s' % st.name)

        stack = parser.Stack.load(context, stack=st)

        # Kill any pending threads by calling ThreadGroup.stop()
        if st.id in self.stg:
            self.stg[st.id].stop()
            del self.stg[st.id]
        # use the service ThreadGroup for deletes
        self.tg.add_thread(stack.delete)
        return None

    @request_context
    def list_events(self, context, stack_identity):
        """
        The list_events method lists all events associated with a given stack.
        arg1 -> RPC context.
        arg2 -> Name of the stack you want to get events for.
        """
        if stack_identity is not None:
            st = self._get_stack(context, stack_identity)

            events = db_api.event_get_all_by_stack(context, st.id)
        else:
            events = db_api.event_get_all_by_tenant(context)

        return {'events': [api.format_event(context, e) for e in events]}

    @request_context
    def describe_stack_resource(self, context, stack_identity, resource_name):
        s = self._get_stack(context, stack_identity)

        stack = parser.Stack.load(context, stack=s)
        if resource_name not in stack:
            raise AttributeError('Unknown resource name')

        resource = stack[resource_name]
        if resource.id is None:
            raise AttributeError('Resource not created')

        return api.format_stack_resource(stack[resource_name])

    @request_context
    def describe_stack_resources(self, context, stack_identity,
                                 physical_resource_id, logical_resource_id):
        if stack_identity is not None:
            s = self._get_stack(context, stack_identity)
        else:
            rs = db_api.resource_get_by_physical_resource_id(context,
                    physical_resource_id)
            if not rs:
                msg = "The specified PhysicalResourceId doesn't exist"
                raise AttributeError(msg)
            s = rs.stack

        if not s:
            raise AttributeError("The specified stack doesn't exist")

        stack = parser.Stack.load(context, stack=s)

        if logical_resource_id is not None:
            name_match = lambda r: r.name == logical_resource_id
        else:
            name_match = lambda r: True

        return [api.format_stack_resource(resource)
                for resource in stack if resource.id is not None and
                                         name_match(resource)]

    @request_context
    def list_stack_resources(self, context, stack_identity):
        s = self._get_stack(context, stack_identity)

        stack = parser.Stack.load(context, stack=s)

        return [api.format_stack_resource(resource, detail=False)
                for resource in stack if resource.id is not None]

    @request_context
    def metadata_update(self, context, stack_id, resource_name, metadata):
        """
        Update the metadata for the given resource.
        """
        s = db_api.stack_get(None, stack_id)
        if s is None:
            logger.warn("Stack %s not found" % stack_id)
            return ['stack', None]

        stack = parser.Stack.load(None, stack=s)
        if resource_name not in stack:
            logger.warn("Resource not found %s:%s." % (stack_id,
                                                       resource_name))
            return ['resource', None]

        resource = stack[resource_name]
        resource.metadata = metadata

        return [None, resource.metadata]

    def _periodic_watcher_task(self, sid):
        """
        Periodic task, created for each stack, triggers watch-rule
        evaluation for all rules defined for the stack
        sid = stack ID
        """
        # Retrieve the stored credentials & create context
        # Require admin=True to the stack_get to defeat tenant
        # scoping otherwise we fail to retrieve the stack
        logger.debug("Periodic watcher task for stack %s" % sid)
        admin_context = context.get_admin_context()
        stack = db_api.stack_get(admin_context, sid, admin=True)
        if not stack:
            logger.error("Unable to retrieve stack %s for periodic task" %
                        sid)
            return
        user_creds = db_api.user_creds_get(stack.user_creds_id)
        stack_context = context.RequestContext.from_dict(user_creds)

        # Get all watchrules for this stack and evaluate them
        try:
            wrs = db_api.watch_rule_get_all_by_stack(stack_context, sid)
        except Exception as ex:
            logger.warn('periodic_task db error (%s) %s' %
                        ('watch rule removed?', str(ex)))
            return
        for wr in wrs:
            rule = watchrule.WatchRule.load(stack_context, watch=wr)
            rule.evaluate()

    @request_context
    def create_watch_data(self, context, watch_name, stats_data):
        '''
        This could be used by CloudWatch and WaitConditions
        and treat HA service events like any other CloudWatch.
        '''
        rule = watchrule.WatchRule.load(context, watch_name)
        rule.create_watch_data(stats_data)
        logger.debug('new watch:%s data:%s' % (watch_name, str(stats_data)))
        return stats_data

    @request_context
    def show_watch(self, context, watch_name):
        '''
        The show_watch method returns the attributes of one watch/alarm
        arg1 -> RPC context.
        arg2 -> Name of the watch you want to see, or None to see all
        '''
        if watch_name:
            wrn = [watch_name]
        else:
            try:
                wrn = [w.name for w in db_api.watch_rule_get_all(context)]
            except Exception as ex:
                logger.warn('show_watch (all) db error %s' % str(ex))
                return

        wrs = [watchrule.WatchRule.load(context, w) for w in wrn]
        result = [api.format_watch(w) for w in wrs]
        return result

    @request_context
    def show_watch_metric(self, context, namespace=None, metric_name=None):
        '''
        The show_watch method returns the datapoints for a metric
        arg1 -> RPC context.
        arg2 -> Name of the namespace you want to see, or None to see all
        arg3 -> Name of the metric you want to see, or None to see all
        '''

        # DB API and schema does not yet allow us to easily query by
        # namespace/metric, but we will want this at some point
        # for now, the API can query all metric data and filter locally
        if namespace != None or metric_name != None:
            logger.error("Filtering by namespace/metric not yet supported")
            return

        try:
            wds = db_api.watch_data_get_all(context)
        except Exception as ex:
            logger.warn('show_metric (all) db error %s' % str(ex))
            return

        result = [api.format_watch_data(w) for w in wds]
        return result

    @request_context
    def set_watch_state(self, context, watch_name, state):
        '''
        Temporarily set the state of a given watch
        arg1 -> RPC context.
        arg2 -> Name of the watch
        arg3 -> State (must be one defined in WatchRule class
        '''
        wr = watchrule.WatchRule.load(context, watch_name)
        wr.set_watch_state(state)

        # Return the watch with the state overriden to indicate success
        # We do not update the timestamps as we are not modifying the DB
        result = api.format_watch(wr)
        result[api.WATCH_STATE_VALUE] = state
        return result