#    Copyright (C) 2013 Yahoo! Inc. All Rights Reserved.
#
#    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 contextlib
import hashlib
import logging
import os
import random
import sys
import time

logging.basicConfig(level=logging.ERROR)

self_dir = os.path.abspath(os.path.dirname(__file__))
top_dir = os.path.abspath(os.path.join(os.path.dirname(__file__),
                                       os.pardir,
                                       os.pardir))
sys.path.insert(0, top_dir)
sys.path.insert(0, self_dir)

import futurist
from oslo_utils import uuidutils

from taskflow import engines
from taskflow import exceptions as exc
from taskflow.patterns import graph_flow as gf
from taskflow.patterns import linear_flow as lf
from taskflow.persistence import models
from taskflow import task

import example_utils as eu  # noqa

# INTRO: These examples show how a hierarchy of flows can be used to create a
# vm in a reliable & resumable manner using taskflow + a miniature version of
# what nova does while booting a vm.


@contextlib.contextmanager
def slow_down(how_long=0.5):
    try:
        yield how_long
    finally:
        if len(sys.argv) > 1:
            # Only both to do this if user input provided.
            print("** Ctrl-c me please!!! **")
            time.sleep(how_long)


class PrintText(task.Task):
    """Just inserts some text print outs in a workflow."""
    def __init__(self, print_what, no_slow=False):
        content_hash = hashlib.md5(print_what.encode('utf-8')).hexdigest()[0:8]
        super().__init__(name="Print: %s" % (content_hash))
        self._text = print_what
        self._no_slow = no_slow

    def execute(self):
        if self._no_slow:
            eu.print_wrapped(self._text)
        else:
            with slow_down():
                eu.print_wrapped(self._text)


class DefineVMSpec(task.Task):
    """Defines a vm specification to be."""
    def __init__(self, name):
        super().__init__(provides='vm_spec', name=name)

    def execute(self):
        return {
            'type': 'kvm',
            'disks': 2,
            'vcpu': 1,
            'ips': 1,
            'volumes': 3,
        }


class LocateImages(task.Task):
    """Locates where the vm images are."""
    def __init__(self, name):
        super().__init__(provides='image_locations', name=name)

    def execute(self, vm_spec):
        image_locations = {}
        for i in range(0, vm_spec['disks']):
            url = "http://www.yahoo.com/images/%s" % (i)
            image_locations[url] = "/tmp/%s.img" % (i)
        return image_locations


class DownloadImages(task.Task):
    """Downloads all the vm images."""
    def __init__(self, name):
        super().__init__(provides='download_paths',
                         name=name)

    def execute(self, image_locations):
        for src, loc in image_locations.items():
            with slow_down(1):
                print("Downloading from {} => {}".format(src, loc))
        return sorted(image_locations.values())


class CreateNetworkTpl(task.Task):
    """Generates the network settings file to be placed in the images."""
    SYSCONFIG_CONTENTS = """DEVICE=eth%s
BOOTPROTO=static
IPADDR=%s
ONBOOT=yes"""

    def __init__(self, name):
        super().__init__(provides='network_settings',
                         name=name)

    def execute(self, ips):
        settings = []
        for i, ip in enumerate(ips):
            settings.append(self.SYSCONFIG_CONTENTS % (i, ip))
        return settings


class AllocateIP(task.Task):
    """Allocates the ips for the given vm."""
    def __init__(self, name):
        super().__init__(provides='ips', name=name)

    def execute(self, vm_spec):
        ips = []
        for _i in range(0, vm_spec.get('ips', 0)):
            ips.append("192.168.0.%s" % (random.randint(1, 254)))
        return ips


class WriteNetworkSettings(task.Task):
    """Writes all the network settings into the downloaded images."""
    def execute(self, download_paths, network_settings):
        for j, path in enumerate(download_paths):
            with slow_down(1):
                print("Mounting {} to /tmp/{}".format(path, j))
            for i, setting in enumerate(network_settings):
                filename = ("/tmp/etc/sysconfig/network-scripts/"
                            "ifcfg-eth%s" % (i))
                with slow_down(1):
                    print("Writing to %s" % (filename))
                    print(setting)


class BootVM(task.Task):
    """Fires off the vm boot operation."""
    def execute(self, vm_spec):
        print("Starting vm!")
        with slow_down(1):
            print("Created: %s" % (vm_spec))


class AllocateVolumes(task.Task):
    """Allocates the volumes for the vm."""
    def execute(self, vm_spec):
        volumes = []
        for i in range(0, vm_spec['volumes']):
            with slow_down(1):
                volumes.append("/dev/vda%s" % (i + 1))
                print("Allocated volume %s" % volumes[-1])
        return volumes


class FormatVolumes(task.Task):
    """Formats the volumes for the vm."""
    def execute(self, volumes):
        for v in volumes:
            print("Formatting volume %s" % v)
            with slow_down(1):
                pass
            print("Formatted volume %s" % v)


def create_flow():
    # Setup the set of things to do (mini-nova).
    flow = lf.Flow("root").add(
        PrintText("Starting vm creation.", no_slow=True),
        lf.Flow('vm-maker').add(
            # First create a specification for the final vm to-be.
            DefineVMSpec("define_spec"),
            # This does all the image stuff.
            gf.Flow("img-maker").add(
                LocateImages("locate_images"),
                DownloadImages("download_images"),
            ),
            # This does all the network stuff.
            gf.Flow("net-maker").add(
                AllocateIP("get_my_ips"),
                CreateNetworkTpl("fetch_net_settings"),
                WriteNetworkSettings("write_net_settings"),
            ),
            # This does all the volume stuff.
            gf.Flow("volume-maker").add(
                AllocateVolumes("allocate_my_volumes", provides='volumes'),
                FormatVolumes("volume_formatter"),
            ),
            # Finally boot it all.
            BootVM("boot-it"),
        ),
        # Ya it worked!
        PrintText("Finished vm create.", no_slow=True),
        PrintText("Instance is running!", no_slow=True))
    return flow

eu.print_wrapped("Initializing")

# Setup the persistence & resumption layer.
with eu.get_backend() as backend:

    # Try to find a previously passed in tracking id...
    try:
        book_id, flow_id = sys.argv[2].split("+", 1)
        if not uuidutils.is_uuid_like(book_id):
            book_id = None
        if not uuidutils.is_uuid_like(flow_id):
            flow_id = None
    except (IndexError, ValueError):
        book_id = None
        flow_id = None

    # Set up how we want our engine to run, serial, parallel...
    try:
        executor = futurist.GreenThreadPoolExecutor(max_workers=5)
    except RuntimeError:
        # No eventlet installed, just let the default be used instead.
        executor = None

    # Create/fetch a logbook that will track the workflows work.
    book = None
    flow_detail = None
    if all([book_id, flow_id]):
        # Try to find in a prior logbook and flow detail...
        with contextlib.closing(backend.get_connection()) as conn:
            try:
                book = conn.get_logbook(book_id)
                flow_detail = book.find(flow_id)
            except exc.NotFound:
                pass
    if book is None and flow_detail is None:
        book = models.LogBook("vm-boot")
        with contextlib.closing(backend.get_connection()) as conn:
            conn.save_logbook(book)
        engine = engines.load_from_factory(create_flow,
                                           backend=backend, book=book,
                                           engine='parallel',
                                           executor=executor)
        print("!! Your tracking id is: '{}+{}'".format(
            book.uuid, engine.storage.flow_uuid))
        print("!! Please submit this on later runs for tracking purposes")
    else:
        # Attempt to load from a previously partially completed flow.
        engine = engines.load_from_detail(flow_detail, backend=backend,
                                          engine='parallel', executor=executor)

    # Make me my vm please!
    eu.print_wrapped('Running')
    engine.run()

# How to use.
#
# 1. $ python me.py "sqlite:////tmp/nova.db"
# 2. ctrl-c before this finishes
# 3. Find the tracking id (search for 'Your tracking id is')
# 4. $ python me.py "sqlite:////tmp/cinder.db" "$tracking_id"
# 5. Watch it pick up where it left off.
# 6. Profit!