#!/usr/bin/python3

# Copyright (C) 2012-2016
#
# * Volker Diels-Grabsch <v@njh.eu>
# * art0int <zvn_mail@mail.ru>
# * guillaume <guillaume@atto.be>
#
# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

import hashlib
import os
import os.path
import struct
import subprocess
import sys

# device_function: filters or transforms device names
device_function = lambda dev : dev

# remote_command: command to run bscp on the remote host
remote_command = __file__

def serve():
    global allowed_devices
    (size, blocksize, filename_len, hashname_len) = struct.unpack('<QQQQ', sys.stdin.buffer.read(8+8+8+8))
    filename = sys.stdin.buffer.read(filename_len).decode()
    hashname = sys.stdin.buffer.read(hashname_len).decode()
    
    filename = device_function(filename)

    if filename == None or len(filename) == 0:
        return

    if not os.path.exists(filename):
        # Create sparse file
        with open(filename, 'wb') as f:
            f.truncate(size)
        os.chmod(filename, 0o600)

    with open(filename, 'rb+') as f:
        f.seek(0, 2)
        sys.stdout.buffer.write(struct.pack('<Q', f.tell()))
        readremain = size
        rblocksize = blocksize
        f.seek(0)
        while True:
            if readremain <= blocksize:
                rblocksize = readremain
            block = f.read(rblocksize)
            if len(block) == 0:
                break
            digest = hashlib.new(hashname, block).digest()
            sys.stdout.buffer.write(digest)
            readremain -= rblocksize
            if readremain == 0:
                break
        sys.stdout.flush()
        while True:
            position_s = sys.stdin.buffer.read(8)
            if len(position_s) == 0:
                break
            (position,) = struct.unpack('<Q', position_s)
            block = sys.stdin.buffer.read(blocksize)
            f.seek(position)
            f.write(block)
        readremain = size
        rblocksize = blocksize
        hash_total = hashlib.new(hashname)
        f.seek(0)
        while True:
            if readremain <= blocksize:
                rblocksize = readremain
            block = f.read(rblocksize)
            if len(block) == 0:
                break
            hash_total.update(block)
            readremain -= rblocksize
            if readremain == 0:
                break
    sys.stdout.buffer.write(hash_total.digest())

class IOCounter:
    def __init__(self, in_stream, out_stream):
        self.in_stream = in_stream
        self.out_stream = out_stream
        self.in_total = 0
        self.out_total = 0
    def read(self, size=None):
        if size is None:
            s = self.in_stream.read()
        else:
            s = self.in_stream.read(size)
        self.in_total += len(s)
        return s
    def write(self, s):
        self.out_stream.write(s)
        self.out_total += len(s)
    def flush(self):
        self.out_stream.flush()

def bscp(local_filename, remote_host, remote_filename, blocksize, hashname):
    hash_total = hashlib.new(hashname)
    with open(local_filename, 'rb') as f:
        f.seek(0, 2)
        size = f.tell()
        f.seek(0)

        # Calculate number of blocks, including the last block which may be smaller
        blockcount = int((size + blocksize - 1) / blocksize)

        command = ('ssh', remote_host, '--', remote_command)
        p = subprocess.Popen(command, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
        io = IOCounter(p.stdout, p.stdin)

        remote_filename_bytes = remote_filename.encode()
        hashname_bytes = hashname.encode()
        io.write(struct.pack('<QQQQ', size, blocksize, len(remote_filename_bytes), len(hashname_bytes)))
        io.write(remote_filename_bytes)
        io.write(hashname_bytes)
        io.flush()

        (remote_size,) = struct.unpack('<Q', io.read(8))
        if remote_size < size:
            raise RuntimeError('Remote size less than local (local: %i, remote: %i)' % (size, remote_size))
        remote_digest_list = [io.read(hash_total.digest_size) for i in range(blockcount)]

        for remote_digest in remote_digest_list:
            position = f.tell()
            block = f.read(blocksize)
            hash_total.update(block)
            digest = hashlib.new(hashname, block).digest()
            if digest != remote_digest:
                try:
                    io.write(struct.pack('<Q', position))
                    io.write(block)
                except IOError:
                    break
        io.flush()
        p.stdin.close()

        remote_digest_total = io.read()
        p.wait()
        if remote_digest_total != hash_total.digest():
            raise RuntimeError('Checksum mismatch after transfer')
    return (io.in_total, io.out_total, size)

if __name__ == '__main__':
    try:
        local_filename = sys.argv[1]
        (remote_host, remote_filename) = sys.argv[2].split(':')
        if len(sys.argv) >= 4:
            blocksize = int(sys.argv[3])
        else:
            blocksize = 64 * 1024
        if len(sys.argv) >= 5:
            hashname = sys.argv[4]
        else:
            hashname = 'sha1'
        assert len(sys.argv) <= 5
    except:
        usage = 'bscp SRC HOST:DEST [BLOCKSIZE] [HASH]'
        sys.stderr.write('Usage:\n\n    %s\n\n' % (usage,))
        sys.exit(1)
    (in_total, out_total, size) = bscp(local_filename, remote_host, remote_filename, blocksize, hashname)
    speedup = size * 1.0 / (in_total + out_total)
    sys.stderr.write('in=%i out=%i size=%i speedup=%.2f\n' % (in_total, out_total, size, speedup))