# The MIT License (MIT)
#
# Copyright (c) 2015 David Wison (original code)
# Copyright (c) 2019 Moshe Malawach (modified for smart contract use)
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
import ctypes
import json
import os
import resource
import signal
import socket
import struct
from multiprocessing import Process
from RestrictedPython import (compile_restricted, safe_builtins,
                              utility_builtins)

builtins = {**safe_builtins, **utility_builtins}
#builtins['__metaclass__'] = type
builtins['__name__'] = "SC"
del builtins['random']
del builtins['whrandom']
_libc = ctypes.CDLL(None)
_exit = _libc._exit
_prctl = _libc.prctl
PR_SET_SECCOMP = 22
SECCOMP_MODE_STRICT = 1


def enable_seccomp():
    rc = _prctl(PR_SET_SECCOMP, SECCOMP_MODE_STRICT, 0)
    assert rc == 0


def read_exact(fp, n):
    buf = b''
    while len(buf) < n:
        buf2 = os.read(fp.fileno(), n)
        if not buf2:
            _exit(123)
        buf += buf2
    return buf2


def write_exact(fp, s):
    done = 0
    while done < len(s):
        written = os.write(fp.fileno(), s[done:])
        if not written:
            _exit(123)
        done += written


class SecureEvalHost(object):
    def __init__(self):
        self.host, self.child = socket.socketpair()
        self.pid = None

    def start_child(self):
        assert not self.pid
        self.pid = os.fork()
        if not self.pid:
            self._child_main()
        self.child.close()

    def kill_child(self):
        assert self.pid
        pid, status = os.waitpid(self.pid, os.WNOHANG)
        os.kill(self.pid, signal.SIGKILL)

    def do_eval(self, msg):
        return {'result': eval(msg['body'])}

    def _do_exec(self, msg):
        locs = {}
        globs = {'__builtins__': builtins}
        byte_code = compile(msg['body'], '<restricted-python>', 'exec')
        exec(byte_code, globs, locs)
        return locs

    def do_exec_func(self, msg):
        try:
            locs = self._do_exec(msg)
        except Exception as e:
            return {'error': repr(e), 'error_step': 'prepare', 'result': None}

        try:
            result = locs[msg['func']](*msg['args'], **msg['kwargs'])
            return {'result': result}
        except Exception as e:
            return {'error': repr(e), 'error_step': 'call', 'result': None}

    def do_construct(self, msg):
        try:
            locs = self._do_exec(msg)
        except Exception as e:
            return {'error': repr(e), 'error_step': 'prepare', 'result': None}

        try:
            item_class = locs['SmartContract']
            obj = item_class(*msg['args'], **msg['kwargs'])
            return {'result': True, 'state': obj.__dict__}
        except Exception as e:
            return {'error': repr(e), 'error_step': 'call', 'result': None}

    def do_call(self, msg):
        try:
            locs = self._do_exec(msg)
        except Exception as e:
            return {'error': repr(e), 'error_step': 'prepare', 'result': None}

        try:
            item_class = locs['SmartContract']
            instance = item_class.__new__(item_class)
            instance.__dict__ = msg['state']
            result = getattr(instance, msg['func'])(*msg['args'],
                                                    **msg['kwargs'])
            return {'result': result, 'state': instance.__dict__}
        except Exception as e:
            return {'error': repr(e), 'error_step': 'call', 'result': None}

    def _child_main(self):
        self.host.close()
        for fd in map(int, os.listdir('/proc/self/fd')):
            try:
                if fd != self.child.fileno():
                    os.close(fd)
            except OSError:
                pass
        resource.setrlimit(resource.RLIMIT_CPU, (1, 1))
        soft, hard = resource.getrlimit(resource.RLIMIT_AS)
        resource.setrlimit(resource.RLIMIT_AS, (64 * 1024, 128 * 1024))
        soft, hard = resource.getrlimit(resource.RLIMIT_AS)
        print(soft, hard)

        enable_seccomp()
        while True:
            sz, = struct.unpack('>L', read_exact(self.child, 4))
            doc = json.loads(read_exact(self.child, sz))
            try:
                if doc['cmd'] == 'eval':
                    resp = self.do_eval(doc)
                elif doc['cmd'] == 'exec_func':
                    resp = self.do_exec_func(doc)
                elif doc['cmd'] == 'construct':
                    resp = self.do_construct(doc)
                elif doc['cmd'] == 'call':
                    resp = self.do_call(doc)
                elif doc['cmd'] == 'exit':
                    _exit(0)
            except Exception as e:
                resp = {'error': repr(e), 'error_step': 'unhandled',
                        'result': None}
            goobs = json.dumps(resp)
            write_exact(self.child, struct.pack('>L', len(goobs)))
            write_exact(self.child, goobs.encode('utf-8'))

    def eval(self, s):
        msg = json.dumps({'cmd': 'eval', 'body': s})
        write_exact(self.host, struct.pack('>L', len(msg)))
        write_exact(self.host, msg.encode('utf-8'))
        sz, = struct.unpack('>L', read_exact(self.host, 4))
        goobs = json.loads(read_exact(self.host, sz).decode('utf-8'))
        return goobs['result']

    def exec_func(self, s, func, *args, **kwargs):
        msg = json.dumps({'cmd': 'exec_func', 'body': s,
                          'func': func, 'args': args,
                          'kwargs': kwargs})
        write_exact(self.host, struct.pack('>L', len(msg)))
        write_exact(self.host, msg.encode('utf-8'))
        sz, = struct.unpack('>L', read_exact(self.host, 4))
        goobs = json.loads(read_exact(self.host, sz).decode('utf-8'))
        return goobs

    def construct(self, s, args, kwargs={}):
        msg = json.dumps({'cmd': 'construct', 'body': s,
                          'args': args,
                          'kwargs': kwargs})
        write_exact(self.host, struct.pack('>L', len(msg)))
        write_exact(self.host, msg.encode('utf-8'))
        sz, = struct.unpack('>L', read_exact(self.host, 4))
        goobs = json.loads(read_exact(self.host, sz).decode('utf-8'))
        return goobs

    def call(self, s, func, state, args, kwargs={}):
        msg = json.dumps({'cmd': 'call', 'body': s, 'state': state,
                          'func': func, 'args': args,
                          'kwargs': kwargs})
        write_exact(self.host, struct.pack('>L', len(msg)))
        write_exact(self.host, msg.encode('utf-8'))
        sz, = struct.unpack('>L', read_exact(self.host, 4))
        goobs = json.loads(read_exact(self.host, sz).decode('utf-8'))
        return goobs



def go():
    insecure_code = open('token_class.py', 'r').read()
    sec = SecureEvalHost()
    sec.start_child()
    try:
        print(sec.eval('1+100'))
        res = sec.construct(insecure_code, [{'from': '0xblah'}, 'Test Token', 'TST', 1000])
        print(res)
        res = sec.call(insecure_code, 'transfer', res['state'],
                       [{'from': '0xblah'}, "0xbluh", 2])
        print(res)
        res = sec.call(insecure_code, 'transfer', res['state'],
                       [{'from': '0xbluh'}, "0xblih", 3])
        print(res)

    except:
        print("error in process")

    finally:
        sec.kill_child()
    print("finished")


if __name__ == '__main__':
    go()