#!/usr/bin/env python2
# -*- coding: utf-8 -*-
"""
    Blockstack-client
    ~~~~~
    copyright: (c) 2014-2015 by Halfmoon Labs, Inc.
    copyright: (c) 2016-2017 by Blockstack.org

    This file is part of Blockstack-client.

    Blockstack-client is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    Blockstack-client is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
    You should have received a copy of the GNU General Public License
    along with Blockstack-client.  If not, see <http://www.gnu.org/licenses/>.
"""
import os
import sys
import atexit

if sys.version_info.major != 2:
    raise Exception("Python 3 is not supported")

if sys.version_info.minor < 7:
    raise Exception("Python 2.7 or greater is required")

import traceback
import json
import argparse

# Hack around absolute paths
current_dir = os.path.abspath(os.path.dirname(__file__))
parent_dir = os.path.abspath(current_dir + "/../")

import time
import thread
import errno
import signal
import socket
import posixpath
import urllib
import urllib2
import SocketServer
from SimpleHTTPServer import SimpleHTTPRequestHandler
import re
import jsonschema
from jsonschema import ValidationError
import requests
import random
from ConfigParser import SafeConfigParser
import keylib
import shutil
import blockstack_client
import blockstack
from blockstack import virtualchain_hooks
import virtualchain
import blockstack_client.schemas as schemas

SNAPSHOTS_CONFIG_PATH = os.path.expanduser("~/.blockstack-snapshots/blockstack-snapshots.ini")

SNAPSHOT_CHECK_INTERVAL = int(os.environ.get("BLOCKSTACK_SNAPSHOT_CHECK_INTERVAL", 60))
running = True

log = blockstack_client.get_logger("blockstack-snapshots")

class BlockstackSnapshotHandler(SimpleHTTPRequestHandler):
    """
    Snapshot server request handler.

    Endpoints are:
        GET  /v1/ping           Is this server alive?
        POST /v1/snapshot       Sign a snapshot digest if it is signed by a trusted key

    server variables:
        self.server.trusted_public_key
        self.server.private_key
    """

    JSONRPC_MAX_SIZE = 1024 * 1024

    def _send_headers(self, status_code=200, content_type='application/json'):
        """
        Generate and reply headers
        """
        self.send_response(status_code)
        self.send_header('content-type', content_type)
        self.send_header('Access-Control-Allow-Origin', '*')    # CORS
        self.end_headers()


    def _reply_json(self, json_payload, status_code=200):
        """
        Return a JSON-serializable data structure
        """
        self._send_headers(status_code=status_code)
        json_str = json.dumps(json_payload)
        self.wfile.write(json_str)


    def _read_payload(self, maxlen=None):
        """
        Read raw uploaded data.
        Return the data on success
        Return None on I/O error, or if maxlen is not None and the number of bytes read is too big
        """

        client_address_str = "{}:{}".format(self.client_address[0], self.client_address[1])

        # check length
        read_len = self.headers.get('content-length', None)
        if read_len is None:
            log.error("No content-length given from {}".format(client_address_str))
            return None

        try:
            read_len = int(read_len)
        except:
            log.error("Invalid content-length")
            return None

        if maxlen is not None and read_len >= maxlen:
            log.error("Request from {} is too long ({} >= {})".format(client_address_str, read_len, maxlen))
            return None

        # get the payload
        request_str = self.rfile.read(read_len)
        return request_str


    def _read_json(self, schema=None):
        """
        Read a JSON payload from the requester
        Return the parsed payload on success
        Return None on error
        """
        # JSON post?
        request_type = self.headers.get('content-type', None)
        client_address_str = "{}:{}".format(self.client_address[0], self.client_address[1])

        if request_type != 'application/json':
            log.error("Invalid request of type {} from {}".format(request_type, client_address_str))
            return None

        request_str = self._read_payload(maxlen=self.JSONRPC_MAX_SIZE)
        if request_str is None:
            log.error("Failed to read request")
            return None

        # parse the payload
        request = None
        try:
            request = json.loads( request_str )
            if schema is not None:
                jsonschema.validate( request, schema )

        except (TypeError, ValueError, ValidationError) as ve:
            if BLOCKSTACK_DEBUG:
                log.exception(ve)

            return None

        return request


    def parse_qs(self, qs):
        """
        Parse query string, but enforce one instance of each variable.
        Return a dict with the variables on success
        Return None on parse error
        """
        qs_state = urllib2.urlparse.parse_qs(qs)
        ret = {}
        for qs_var, qs_value_list in qs_state.items():
            if len(qs_value_list) > 1:
                return None

            ret[qs_var] = qs_value_list[0]

        return ret


    def get_path_and_qs(self):
        """
        Parse and obtain the path and query values.
        We don't care about fragments.

        Return {'path': ..., 'qs_values': ...} on success
        Return {'error': ...} on error
        """
        path_parts = self.path.split("?", 1)

        if len(path_parts) > 1:
            qs = path_parts[1].split("#", 1)[0]
        else:
            qs = ""

        path = path_parts[0].split("#", 1)[0]
        path = posixpath.normpath(urllib.unquote(path))

        qs_values = self.parse_qs( qs )
        if qs_values is None:
            return {'error': 'Failed to parse query string'}

        parts = path.strip('/').split('/')

        return {'path': path, 'qs_values': qs_values, 'parts': parts}


    def sign_snapshot( self ):
        """
        Read a snapshot digest, sign it, and return the signature.
        Return 200 with {'sigb64': sigb64}€D€D€D€D on success
        Return 401 on invalid request structure
        Return 403 on invalid signature

        TODO: if this server is colocated with a blockstack server, then
        it should verify that independently calculated the same snapshot.
        Use `block_height` for that.
        """
        snapshot_schema = {
            'type': 'object',
            'properties': {
                'block_height': {
                    'type': 'integer',
                },
                'file_hash': {
                    'type': 'string',
                    'pattern': schemas.OP_HEX_PATTERN,
                },
                'sigb64': {
                    'type': 'string',
                    'pattern': schemas.OP_BASE64_PATTERN,
                },
            },
            'required': [
                'file_hash',
                'sigb64',
            ],
            'additionalProperties': False,
        }

        request = self._read_json(schema=snapshot_schema)
        if request is None:
            return self._reply_json({'error': 'Invalid snapshot request'}, status_code=401)
            
        block_height = request['block_height']
        file_hash = request['file_hash']
        sigb64 = request['sigb64']

        snapshot_info = get_snapshot_hash(self.server.snapshots_dir, block_height)
        if 'error' in snapshot_info:
            # nope
            log.debug("Failed to get snapshot hash for {}: {}".format(block_height, snapshot_info['error']))
            self._reply_json({'error': 'Failed to query local snapshot hash'}, status_code=404)

        # did any of our trusted public keys sign it?
        valid = False
        for trusted_public_key in self.server.trusted_public_keys:
            valid = blockstack_client.verify_digest( file_hash, trusted_public_key, sigb64 )
            if valid:
                break

        if not valid:
            return self._reply_json({'error': 'Invalid signature'}, status_code=403)

        # can sign 
        sigb64 = blockstack_client.sign_digest( file_hash, self.server.private_key )
        assert sigb64, "Failed to sign digest"

        return self._reply_json({'sigb64': sigb64})


    def do_POST(self):
        """
        Handle POST request
        """
        path_info = self.get_path_and_qs()
        if 'error' in path_info:
            return self._reply_json({'error': 'Invalid request'}, status_code=401)

        path = path_info['path']
        if path == '/v1/snapshots':
            return self.sign_snapshot()
        else:
            return self._reply_json({'error': 'No such method'}, status_code=404)


    def do_GET(self):
        """
        Handle GET request
        """
        path_info = self.get_path_and_qs()
        if 'error' in path_info:
            return self._reply_json({'error': 'Invalid request'}, status_code=401)
        
        path = path_info['path']
        if path == '/v1/ping':
            return self._reply_json({'status': 'alive'})
        else:
            return self._reply_json({'error': 'No such method'}, status_code=404)


class BlockstackSnapshotServer(SocketServer.TCPServer):
    """
    Snapshot server implementation
    """
    def __init__(self, port, trusted_public_keys, private_key, snapshots_dir ):
        """
        Set up a snapshot server
        """
        SocketServer.TCPServer.__init__(self, ('0.0.0.0', port), BlockstackSnapshotHandler, bind_and_activate=False)

        self.trusted_public_keys = [keylib.ECPublicKey(pk).to_hex() for pk in trusted_public_keys]
        self.private_key = keylib.ECPrivateKey(private_key).to_hex()
        self.snapshots_dir = snapshots_dir

        log.debug("Set SO_REUSADDR")
        self.socket.setsockopt( socket.SOL_SOCKET, socket.SO_REUSEADDR, 1 )

        self.server_bind()
        self.server_activate()


def make_snapshot(snapshots_dir, private_key, block_number):
    """
    Make a snapshot from the given block height at {snapshots_dir}/snapshot.bsk.{block_number}
    Symlink it to {snapshots_dir}/snapshot.bsk

    Return {'status': True} on success
    Return {'error': ...} on failure
    """

    tmp_snapshot_path = os.path.join(snapshots_dir, '.snapshot.bsk.{}'.format(block_number))
    log.debug("Make snapshot for {} in {}".format(block_number, tmp_snapshot_path))

    try:
        res = blockstack.fast_sync_snapshot( tmp_snapshot_path, private_key, block_number )
        assert res
    except Exception as e:
        log.exception(e)
        try:
            os.unlink(tmp_snapshot_path)
        except:
            pass

        return {'error': 'Failed to create snapshot'}

    # move into position 
    snapshot_path = os.path.join(snapshots_dir, 'snapshot.bsk.{}'.format(block_number))
    shutil.move( tmp_snapshot_path, snapshot_path )

    # symlink 'snapshot.bsk' to it 
    old_dir = os.getcwd()
    try:
        os.chdir(snapshots_dir)
        if os.path.exists('snapshot.bsk'):
            os.unlink('snapshot.bsk')

        # symlink it in
        os.symlink('snapshot.bsk.{}'.format(block_number), 'snapshot.bsk')
    except Exception as e:
        log.exception(e)
        return {'error': 'Failed to symlink {} to {}'.format('snapshot.bsk.{}'.format(block_number), 'snapshot.bsk')}
    finally:
        os.chdir(old_dir)

    log.debug("Snapshot at {}".format(snapshot_path))

    return {'status': True}


def get_snapshot_hash(snapshots_dir, block_number):
    """
    Get the expected hash of a snapshot payload
    Return {'status': True, 'hash': hex hash} on success
    Return {'error': ...} on failure
    """

    snapshot_path = os.path.join(snapshots_dir, 'snapshot.bsk.{}'.format(block_number))
    if not os.path.exists(snapshot_path):
        return {'error': 'No such snapshot'}

    snapshot_info = blockstack.fast_sync_inspect_snapshot(snapshot_path)
    if 'error' in snapshot_info:
        return {'error': 'Failed to query snapshot'}

    snapshot_hash = snapshot_info['hash']
    return {'status': True, 'hash': snapshot_hash}


def snapshot_exists(snapshots_dir, block_number):
    """
    Do we have a snapshot for this block height?
    """
    snapshot_path = os.path.join( snapshots_dir, "snapshot.bsk.{}".format(block_number) )
    return os.path.exists(snapshot_path)


def find_backup_blocks(working_dir):
    """
    Find the set of block numbers for which we have backups
    """
    backup_blocks = virtualchain.indexer.StateEngine.get_backup_blocks( virtualchain_hooks, working_dir=working_dir )
    return list(set(backup_blocks))


def find_snapshot_blocks(snapshots_dir):
    """
    Find the set of block numbers for which we have snapshots
    """
    snapshot_blocks = []
    names = os.listdir(snapshots_dir)
    for name in names:
        if re.match("^snapshot.bsk.[0-9]+$", name):
            # what's the block?
            _, block_num_str = name.rsplit('.', 1)
            block_num = int(block_num_str)
            snapshot_blocks.append( block_num )

    return list(set(snapshot_blocks))


def snapshotter_thread_main(working_dir, snapshots_dir, private_key, check_running):
    """
    Continuously watch the snapshots directory.
    Periodically check that we're not running with 
    check_running callable.  Meant to be run in a thread.
    """

    def _wait(timeout):
        deadline = time.time() + timeout
        while time.time() < deadline:
            if not check_running():
                return False

            time.sleep(0.5)

        return True

    if not os.path.exists(snapshots_dir):
        os.makedirs(snapshots_dir)

    block_numbers = find_snapshot_blocks(snapshots_dir)

    log.debug("Snapshotter start")
    while check_running():
        # find out which block numbers are represented in the backups directory

        cur_block_numbers = find_backup_blocks(working_dir)

        log.debug("snapshot blocks: {}".format(",".join(['{}'.format(b) for b in block_numbers])))
        log.debug("backup blocks:   {}".format(",".join(['{}'.format(b) for b in cur_block_numbers])))

        new_block_numbers = []
        for block_number in cur_block_numbers:
            if block_number not in block_numbers:
                new_block_numbers.append(block_number)

        if len(new_block_numbers) == 0:
            # no new blocks
            res = _wait(SNAPSHOT_CHECK_INTERVAL)
            if not res:
                # died
                break

            continue

        # have new snapshots to make.
        # start with the most recent
        for new_block in reversed(sorted(new_block_numbers)):
            res = make_snapshot( snapshots_dir, private_key, new_block )
            if 'error' in res:
                log.error("Failed to make snapshot for {}: {}".format(new_block, res['error']))

            else:
                block_numbers.append(new_block)

    log.debug("Snapshotter exit")
    return


def read_config(config_path=SNAPSHOTS_CONFIG_PATH):
    """
    Read our config file
    Return the config dict on success
    Return {'error': ...} on failure
    """
    
    parser = SafeConfigParser()
    parser.read( config_path )
    
    defaults = {
        'blockstack-snapshots': {
            'private_key': os.path.join( os.path.dirname(config_path), 'public_keys' ),
            'public_keys': os.path.join( os.path.dirname(config_path), 'private_key' ),
            'snapshots_dir': os.path.join( os.path.dirname(config_path), 'snapshots' ),
            'log_file': os.path.join( os.path.dirname(config_path), 'blockstack-snapshots.log' ),
            'port': 31128,
        },
    }

    private_key_path = None
    public_keys_path = None
    snapshots_dir = None
    log_file = None
    port = None

    if parser.has_section("blockstack-snapshots"):
        if parser.has_option('blockstack-snapshots', 'private_key'):
            private_key_path = parser.get('blockstack-snapshots', 'private_key')

        if parser.has_option('blockstack-snapshots', 'public_keys'):
            public_keys_path = parser.get('blockstack-snapshots', 'public_keys')

        if parser.has_option('blockstack-snapshots', 'snapshots_dir'):
            snapshots_dir = parser.get('blockstack-snapshots', 'snapshots_dir')

        if parser.has_option('blockstack-snapshots', 'log_file'):
            log_file = parser.get('blockstack-snapshots', 'log_file')

        if parser.has_option('blockstack-snapshots', 'port'):
            try:
                port = int(parser.get('blockstack-snapshots', 'port'))
            except:
                print >> sys.stderr, "Failed to parse `port` in config file"
                sys.exit(1)

    ret = {
        'blockstack-snapshots': {
            'private_key': private_key_path,
            'public_keys': public_keys_path,
            'snapshots_dir': snapshots_dir,
            'log_file': log_file,
            'port': port
        },
    }

    for sec in ret.keys():
        for field in ret[sec].keys():
            if ret[sec][field] is None:
                if defaults[sec][field] is not None:
                    ret[sec][field] = defaults[sec][field]
                else:
                    del ret[sec][field]

    return ret


def merge_config_args(conf, args):
    """
    Merge CLI arguments into our config dict
    """
    fields = {
        'private_key': 'blockstack-snapshots.private_key',
        'snapshots':   'blockstack-snapshots.snapshots_dir',
        'public_keys': 'blockstack-snapshots.public_keys',
        'log_file':    'blockstack-snapshots.log_file',
        'port':        'blockstack-snapshots.port'
    }
    
    required = fields.keys()

    for attr in fields.keys():
        attrval = getattr(args, attr, None)
        if attrval is None:
            continue

        parts = fields[attr].split('.')
        conf_sec = parts[0]
        conf_attr = parts[1]

        conf[conf_sec][conf_attr] = attrval

    return conf


def server_wait(snapshots_conf):
    """
    Wait for the server to come up
    """
    delay = 1.0
    up = False
    for i in xrange(0, 5):
        try:
            url = 'http://localhost:{}/v1/ping'.format(snapshots_conf['port'])
            req = requests.get(url)
            assert req.status_code == 200
            
            up = True
            break

        except Exception, e:
            log.exception(e)
            log.debug("Failed to ping {}. Try again in {}".format(url, delay))
            time.sleep(delay)
            delay = delay * 2 + random.random() * delay

    return up


def is_running():
    global running
    return running


def get_pid_file_path(config_path=SNAPSHOTS_CONFIG_PATH):
    """
    Get the PID file path
    """
    pid_path = os.path.join( os.path.dirname(config_path), 'blockstack-snapshots.pid' )
    return pid_path


def put_pid_file(config_path=SNAPSHOTS_CONFIG_PATH):
    """
    Put the PID file
    Return True on success
    Return False if it already exists
    """
    pid_path = get_pid_file_path(config_path=config_path)
    if os.path.exists(pid_path):
        log.debug("PID path already exists: {}".format(pid_path))
        return False

    with open(pid_path, "w") as f:
        f.write( str(os.getpid()) )

    return True


def get_pid_from_file(config_path=SNAPSHOTS_CONFIG_PATH):
    """
    Get the PID in the PID file
    Return None if there is no such file
    """
    pid_path = get_pid_file_path(config_path=config_path)
    if not os.path.exists(pid_path):
        return None

    with open(pid_path, 'r') as f:
        pid = int(f.read().strip())

    return pid


def remove_pid_file(config_path=SNAPSHOTS_CONFIG_PATH):
    """
    Remove the PID file
    Idempotent; succeeds even if it isn't there
    """
    pid_path = get_pid_file_path(config_path=config_path)
    if os.path.exists(pid_path):
        os.unlink(pid_path)

    return True


def atexit_cleanup(config_path=SNAPSHOTS_CONFIG_PATH):
    """
    Clean up at exit
    """
    log.debug("Atexit called for {}".format(os.getpid()))
    remove_pid_file(config_path)


def signal_exit(ignored_1, ignored_2):
    """
    Signal handler cleanup
    """
    sys.exit(0)


if __name__ == '__main__':

    virtualchain.setup_virtualchain( virtualchain_hooks )
    working_dir = virtualchain.get_working_dir( impl=virtualchain_hooks )
    config_path = SNAPSHOTS_CONFIG_PATH

    argparser = argparse.ArgumentParser(description="blockstack-snapshots version {}".format(blockstack.VERSION))
    subparsers = argparser.add_subparsers(
        dest='action', help='the action to be taken')

    # ---------------------------
    parser = subparsers.add_parser(
        'start',
        help='start the snapshot daemon')

    parser.add_argument(
        '--debug', action='store_true',
        help='activate debug output')

    parser.add_argument(
        '--config_file', action='store',
        help='path to the config file (Default is {})'.format(config_path))

    parser.add_argument(
        '--snapshots', action='store',
        help='the path to the snapshots output directory')

    parser.add_argument(
        '--private_key', action='store',
        help='the path to the private key to sign snapshots')

    parser.add_argument(
        '--public_keys', action='store',
        help='the path to a file with the list of public keys to verify snapshots')

    parser.add_argument(
        '--log_file', action='store',
        help='path to the log file')

    parser.add_argument(
        '--port', action='store', type=int,
        help='the port to listen on')

    parser.add_argument(
        '--foreground', action='store_true',
        help='Run in the foreground. Do not daemonize')
   
    # ---------------------------
    parser = subparsers.add_parser(
        'stop',
        help='stop the snapshot daemon')

    parser.add_argument(
        '--config_file', action='store',
        help='path to the config file (Default is {})'.format(config_path))

    parser.add_argument(
        '--debug', action='store_true',
        help='activate debug output')

    # ---------------------------
    parser = subparsers.add_parser(
        'snapshot',
        help='make a snapshot for each backup')

    parser.add_argument(
        '--config_file', action='store',
        help='path to the config file (Default is {})'.format(config_path))

    parser.add_argument(
        '--snapshots', action='store',
        help='the path to the snapshots output directory')

    parser.add_argument(
        '--private_key', action='store',
        help='the path to the private key to sign snapshots')

    parser.add_argument(
        '--debug', action='store_true',
        help='activate debug output')
    
    args, _ = argparser.parse_known_args()

    if hasattr(args, 'debug') and args.debug:
        # re-exec without --debug, but set debug 
        os.environ['BLOCKSTACK_DEBUG'] = "1"
        new_argv = []
        for a in sys.argv:
            if a != '--debug':
                new_argv.append(a)

        os.execv(sys.argv[0], new_argv)

    config_path = getattr(args, 'config_path', config_path)

    conf = read_config(config_path=config_path)
    conf = merge_config_args(conf, args)

    snapshots_conf = conf['blockstack-snapshots']

    if args.action == 'start':
        # start up 
        snapshots_path = snapshots_conf.get('snapshots_dir', None)
        private_key_path = snapshots_conf.get('private_key', None)
        public_keys_path = snapshots_conf.get('public_keys', None)
        log_file = snapshots_conf.get('log_file', None)
        port = snapshots_conf.get('port', None)

        if snapshots_path is None or private_key_path is None or public_keys_path is None or log_file is None or port is None:
            argparser.print_help()
            print >> sys.stderr, "\nMissing configuration file information or arguments:\n   {}\n".format( 
                ', '.join( filter( lambda x: snapshots_conf.get(x, None) is None, ['snapshots_dir', 'private_key', 'public_keys', 'log_file', 'port'] ) )
            )

            sys.exit(1)

        private_key = None
        trusted_public_keys = []
        
        if not os.path.exists(snapshots_path) or not os.path.isdir(snapshots_path):
            print >> sys.stderr, "{} does not exist or is not a directory".format(snapshots_path)
            sys.exit(1)

        if not os.path.exists(private_key_path):
            print >> sys.stderr, 'Failed to read {}: no such file or directory'.format(private_key_path)
            sys.exit(1)

        if not os.path.exists(public_keys_path):
            print >> sys.stderr, 'Failed to read {}: no such file or directory'.format(public_keys_path)
            sys.exit(1)

        with open(private_key_path) as f:
            private_key = f.read().strip()

        with open(public_keys_path) as f:
            trusted_public_key_list = f.read().strip()
            trusted_public_keys = trusted_public_key_list.split()

        try:
            private_key = keylib.ECPrivateKey(private_key).to_hex()

            pks = []
            for pk_str in trusted_public_keys:
                pk = keylib.ECPublicKey(pk_str).to_hex()
                pks.append(pk)

            trusted_public_keys = pks

        except:
            print >> sys.stderr, "Invalid key data"
            sys.exit(1)
        
        if not args.foreground:
            # is another daemon running?
            existing_pid = get_pid_from_file(config_path=config_path)
            if existing_pid is not None:
                # is it actually running?
                try:
                    os.kill(existing_pid, 0)
                    print >> sys.stderr, "Another daemon is already running ({})".format(existing_pid)
                    sys.exit(1)

                except OSError as oe:
                    if oe.errno == errno.ESRCH:
                        print >> sys.stderr, "Removing stale PID file"
                        remove_pid_file(config_path=config_path)

                    else:
                        log.exception(oe)
                        sys.exit(1)

                except Exception as e:
                    log.exception(e)
                    sys.exit(1)

            # daemonize
            res = blockstack_client.daemonize( log_file, child_wait=lambda: server_wait(snapshots_conf) )
            if res < 0:
                print >> sys.stderr, "Failed to start server"
                sys.exit(1)

            if res > 0:
                log.debug("Parent {} forked intermediate child {}".format(os.getpid(), res))
                sys.exit(0)

            # daemon child
            # put PID file 
            res = put_pid_file(config_path=config_path)
            if not res:
                print >> sys.stderr, "Failed to write PID file"
                sys.exit(1)


        atexit.register( atexit_cleanup, config_path )
        signal.signal(signal.SIGINT, signal_exit )
        signal.signal(signal.SIGQUIT, signal_exit )
        signal.signal(signal.SIGTERM, signal_exit )

        # daemon child continues here
        # start snapshotter thread
        thr = thread.start_new_thread( snapshotter_thread_main, (working_dir, snapshots_path, private_key, is_running) )

        # start HTTP server
        srv = BlockstackSnapshotServer( port, trusted_public_keys, private_key, snapshots_path )

        try:
            srv.serve_forever()
        except Exception as e:
            log.exception(e)
            running = False

        thr.join()
        sys.exit(0)

    elif args.action == 'stop':
        # stop running snapshot server
        existing_pid = get_pid_from_file(config_path=config_path)
        if existing_pid is not None:
            # is it running?
            try:
                log.debug("Send SIGTERM to {}".format(existing_pid))
                os.kill(existing_pid, signal.SIGTERM)
            except OSError as oe:
                if oe.errno == errno.ESRCH:
                    print >> sys.stderr, "No such process"
                    remove_pid_file(config_path=config_path)
                    sys.exit(0)

                else:
                    log.exception(oe)
                    sys.exit(1)
            
            except Exception as e:
                log.exception(e)
                sys.exit(1)

    elif args.action == 'snapshot':
        # make all snapshots
        snapshots_path = snapshots_conf.get('snapshots_dir', None)
        private_key_path = snapshots_conf.get('private_key', None)

        if snapshots_path is None or private_key_path is None:
            argparser.print_help()
            print >> sys.stderr, "\nMissing configuration file information or arguments\n"
            sys.exit(1)

        if not os.path.exists(snapshots_path) or not os.path.isdir(snapshots_path):
            print >> sys.stderr, "{} does not exist or is not a directory"
            sys.exit(1)

        if not os.path.exists(private_key_path):
            print >> sys.stderr, 'Failed to read {}: no such file or directory'.format(private_key_path)
            sys.exit(1)

        def _snapshot_running():
            global running
            if running:
                running = False
                return True

            else:
                return running

        with open(private_key_path, "r") as f:
            private_key = f.read().strip()

        try:
            private_key = keylib.ECPrivateKey(private_key).to_hex()
        except Exception as e:
            print >> sys.stderr, "Invalid key data"
            sys.exit(1)

        snapshotter_thread_main(working_dir, snapshots_path, private_key, _snapshot_running)
        sys.exit(0)