#!/usr/bin/env python2
# vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:fdm=marker:ai
from __future__ import (unicode_literals, division, absolute_import,
                        print_function)

__license__   = 'GPL v3'
__copyright__ = '2012, Kovid Goyal <kovid at kovidgoyal.net>'
__docformat__ = 'restructuredtext en'

'''
Try to read invalid zip files with missing or damaged central directories.
These are apparently produced in large numbers by the fruitcakes over at B&N.

Tries to only use the local headers to extract data from the damaged zip file.
'''

import os, sys, zlib, shutil
from struct import calcsize, unpack, pack
from collections import namedtuple, OrderedDict
from tempfile import SpooledTemporaryFile

HEADER_SIG = 0x04034b50
HEADER_BYTE_SIG = pack(b'<L', HEADER_SIG)
local_header_fmt = b'<L5HL2L2H'
local_header_sz = calcsize(local_header_fmt)
ZIP_STORED, ZIP_DEFLATED = 0, 8
DATA_DESCRIPTOR_SIG = pack(b'<L', 0x08074b50)

LocalHeader = namedtuple('LocalHeader',
        'signature min_version flags compression_method mod_time mod_date '
        'crc32 compressed_size uncompressed_size filename_length extra_length '
        'filename extra')


def decode_arcname(name):
    if isinstance(name, bytes):
        from calibre.ebooks.chardet import detect
        try:
            name = name.decode('utf-8')
        except:
            res = detect(name)
            encoding = res['encoding']
            try:
                name = name.decode(encoding)
            except:
                name = name.decode('utf-8', 'replace')
    return name


def find_local_header(f):
    pos = f.tell()
    raw = f.read(50*1024)
    try:
        f.seek(pos + raw.index(HEADER_BYTE_SIG))
    except ValueError:
        f.seek(pos)
        return
    raw = f.read(local_header_sz)
    if len(raw) != local_header_sz:
        f.seek(pos)
        return
    header = LocalHeader(*(unpack(local_header_fmt, raw) + (None, None)))
    if header.signature == HEADER_SIG:
        return header
    f.seek(pos)


def find_data_descriptor(f):
    pos = f.tell()
    DD = namedtuple('DataDescriptor', 'crc32 compressed_size uncompressed_size')
    raw = b'a'*16
    try:
        while len(raw) >= 16:
            raw = f.read(50*1024)
            idx = raw.find(DATA_DESCRIPTOR_SIG)
            if idx != -1:
                f.seek(f.tell() - len(raw) + idx + len(DATA_DESCRIPTOR_SIG))
                return DD(*unpack(b'<LLL', f.read(12)))
            # Rewind to handle the case of the signature being cut off
            # by the 50K boundary
            f.seek(f.tell()-len(DATA_DESCRIPTOR_SIG))

        raise ValueError('Failed to find data descriptor signature. '
                         'Data descriptors without signatures are not '
                         'supported.')
    finally:
        f.seek(pos)


def read_local_file_header(f):
    pos = f.tell()
    raw = f.read(local_header_sz)
    if len(raw) != local_header_sz:
        f.seek(pos)
        return
    header = LocalHeader(*(unpack(local_header_fmt, raw) + (None, None)))
    if header.signature != HEADER_SIG:
        f.seek(pos)
        header = find_local_header(f)
        if header is None:
            return
    if header.min_version > 20:
        raise ValueError('This ZIP file uses unsupported features')
    if header.flags & 0b1:
        raise ValueError('This ZIP file is encrypted')
    if header.flags & (1 << 13):
        raise ValueError('This ZIP file uses masking, unsupported.')
    if header.compression_method not in {ZIP_STORED, ZIP_DEFLATED}:
        raise ValueError('This ZIP file uses an unsupported compression method')
    has_data_descriptors = header.flags & (1 << 3)
    fname = extra = None
    if header.filename_length > 0:
        fname = f.read(header.filename_length)
        if len(fname) != header.filename_length:
            return
        try:
            fname = fname.decode('ascii')
        except UnicodeDecodeError:
            if header.flags & (1 << 11):
                try:
                    fname = fname.decode('utf-8')
                except UnicodeDecodeError:
                    pass
        fname = decode_arcname(fname).replace('\\', '/')

    if header.extra_length > 0:
        extra = f.read(header.extra_length)
        if len(extra) != header.extra_length:
            return
    if has_data_descriptors:
        desc = find_data_descriptor(f)
        header = header._replace(crc32=desc.crc32,
                                 compressed_size=desc.compressed_size,
                                 uncompressed_size=desc.uncompressed_size)
    return LocalHeader(*(
        header[:-2] + (fname, extra)
        ))


def read_compressed_data(f, header):
    cdata = f.read(header.compressed_size)
    return cdata


def copy_stored_file(src, size, dest):
    read = 0
    amt = min(size, 20*1024)
    while read < size:
        raw = src.read(min(size-read, amt))
        if not raw:
            raise ValueError('Premature end of file')
        dest.write(raw)
        read += len(raw)


def copy_compressed_file(src, size, dest):
    d = zlib.decompressobj(-15)
    read = 0
    amt = min(size, 20*1024)
    while read < size:
        raw = src.read(min(size-read, amt))
        if not raw and read < size:
            raise ValueError('Invalid ZIP file, local header is damaged')
        read += len(raw)
        dest.write(d.decompress(raw, 200*1024))
        count = 0
        while d.unconsumed_tail:
            count += 1
            dest.write(d.decompress(d.unconsumed_tail, 200*1024))

            if count > 100:
                raise ValueError('This ZIP file contains a ZIP bomb in %s'%
                        os.path.basename(dest.name))


def _extractall(f, path=None, file_info=None):
    found = False
    while True:
        header = read_local_file_header(f)
        if not header:
            break
        has_data_descriptors = header.flags & (1 << 3)
        seekval = header.compressed_size + (16 if has_data_descriptors else 0)
        found = True
        # Sanitize path changing absolute to relative paths and removing .. and
        # .
        fname = header.filename.replace(os.sep, '/')
        fname = os.path.splitdrive(fname)[1]
        parts = [x for x in fname.split('/') if x not in {'', os.path.pardir, os.path.curdir}]
        if not parts:
            continue
        if header.uncompressed_size == 0:
            # Directory
            f.seek(f.tell()+seekval)
            if path is not None:
                bdir = os.path.join(path, *parts)
                if not os.path.exists(bdir):
                    os.makedirs(bdir)
            continue

        # File
        if file_info is not None:
            file_info[header.filename] = (f.tell(), header)
        if path is not None:
            bdir = os.path.join(path, *(parts[:-1]))
            if not os.path.exists(bdir):
                os.makedirs(bdir)
            dest = os.path.join(path, *parts)
            with open(dest, 'wb') as o:
                if header.compression_method == ZIP_STORED:
                    copy_stored_file(f, header.compressed_size, o)
                else:
                    copy_compressed_file(f, header.compressed_size, o)
        else:
            f.seek(f.tell()+seekval)

    if not found:
        raise ValueError('Not a ZIP file')


def extractall(path_or_stream, path=None):
    f = path_or_stream
    close_at_end = False
    if not hasattr(f, 'read'):
        f = open(f, 'rb')
        close_at_end = True
    if path is None:
        path = os.getcwdu()
    pos = f.tell()
    try:
        _extractall(f, path)
    finally:
        f.seek(pos)
        if close_at_end:
            f.close()


class LocalZipFile(object):

    def __init__(self, stream):
        self.file_info = OrderedDict()
        _extractall(stream, file_info=self.file_info)
        self.stream = stream

    def open(self, name, spool_size=5*1024*1024):
        if isinstance(name, LocalHeader):
            name = name.filename
        try:
            offset, header = self.file_info.get(name)
        except KeyError:
            raise ValueError('This ZIP container has no file named: %s'%name)

        self.stream.seek(offset)
        dest = SpooledTemporaryFile(max_size=spool_size)

        if header.compression_method == ZIP_STORED:
            copy_stored_file(self.stream, header.compressed_size, dest)
        else:
            copy_compressed_file(self.stream, header.compressed_size, dest)
        dest.seek(0)
        return dest

    def getinfo(self, name):
        try:
            offset, header = self.file_info.get(name)
        except KeyError:
            raise ValueError('This ZIP container has no file named: %s'%name)
        return header

    def read(self, name, spool_size=5*1024*1024):
        with self.open(name, spool_size=spool_size) as f:
            return f.read()

    def extractall(self, path=None):
        self.stream.seek(0)
        _extractall(self.stream, path=(path or os.getcwdu()))

    def close(self):
        pass

    def safe_replace(self, name, datastream, extra_replacements={},
        add_missing=False):
        from calibre.utils.zipfile import ZipFile, ZipInfo
        replacements = {name:datastream}
        replacements.update(extra_replacements)
        names = frozenset(replacements.keys())
        found = set()

        def rbytes(name):
            r = replacements[name]
            if not isinstance(r, bytes):
                r = r.read()
            return r

        with SpooledTemporaryFile(max_size=100*1024*1024) as temp:
            ztemp = ZipFile(temp, 'w')
            for offset, header in self.file_info.itervalues():
                if header.filename in names:
                    zi = ZipInfo(header.filename)
                    zi.compress_type = header.compression_method
                    ztemp.writestr(zi, rbytes(header.filename))
                    found.add(header.filename)
                else:
                    ztemp.writestr(header.filename, self.read(header.filename,
                        spool_size=0))
            if add_missing:
                for name in names - found:
                    ztemp.writestr(name, rbytes(name))
            ztemp.close()
            zipstream = self.stream
            temp.seek(0)
            zipstream.seek(0)
            zipstream.truncate()
            shutil.copyfileobj(temp, zipstream)
            zipstream.flush()

if __name__ == '__main__':
    extractall(sys.argv[-1])

