import os
import time
import zlib
import struct
from datetime import datetime

from .util import fsenc


def dostime2unix(buf):
    t, d = struct.unpack("<HH", buf)

    ts = (t & 0x1F) * 2
    tm = (t >> 5) & 0x3F
    th = t >> 11

    dd = d & 0x1F
    dm = (d >> 5) & 0xF
    dy = (d >> 9) + 1980

    tt = (dy, dm, dd, th, tm, ts)
    tf = "{:04d}-{:02d}-{:02d} {:02d}:{:02d}:{:02d}"
    iso = tf.format(*tt)

    dt = datetime.strptime(iso, "%Y-%m-%d %H:%M:%S")
    return int(dt.timestamp())


def unixtime2dos(ts):
    tt = time.gmtime(ts)
    dy, dm, dd, th, tm, ts = list(tt)[:6]

    bd = ((dy - 1980) << 9) + (dm << 5) + dd
    bt = (th << 11) + (tm << 5) + ts // 2
    return struct.pack("<HH", bt, bd)


def gen_fdesc(sz, crc32, z64):
    ret = b"\x50\x4b\x07\x08"
    fmt = "<LQQ" if z64 else "<LLL"
    ret += struct.pack(fmt, crc32, sz, sz)
    return ret


def gen_hdr(h_pos, fn, sz, lastmod, utf8, crc32, pre_crc):
    """
    does regular file headers
    and the central directory meme if h_pos is set
    (h_pos = absolute position of the regular header)
    """

    # appnote 4.5 / zip 3.0 (2008) / unzip 6.0 (2009) says to add z64
    # extinfo for values which exceed H, but that becomes an off-by-one
    # (can't tell if it was clamped or exactly maxval), make it obvious
    z64 = sz >= 0xFFFFFFFF
    z64v = [sz, sz] if z64 else []
    if h_pos and h_pos >= 0xFFFFFFFF:
        # central, also consider ptr to original header
        z64v.append(h_pos)

    # confusingly this doesn't bump if h_pos
    req_ver = b"\x2d\x00" if z64 else b"\x0a\x00"

    if crc32:
        crc32 = struct.pack("<L", crc32)
    else:
        crc32 = b"\x00" * 4

    if h_pos is None:
        # 4b magic, 2b min-ver
        ret = b"\x50\x4b\x03\x04" + req_ver
    else:
        # 4b magic, 2b spec-ver, 2b min-ver
        ret = b"\x50\x4b\x01\x02\x1e\x03" + req_ver

    ret += b"\x00" if pre_crc else b"\x08"  # streaming
    ret += b"\x08" if utf8 else b"\x00"  # appnote 6.3.2 (2007)

    # 2b compression, 4b time, 4b crc
    ret += b"\x00\x00" + unixtime2dos(lastmod) + crc32

    # spec says to put zeros when !crc if bit3 (streaming)
    # however infozip does actual sz and it even works on winxp
    # (same reasning for z64 extradata later)
    vsz = 0xFFFFFFFF if z64 else sz
    ret += struct.pack("<LL", vsz, vsz)

    bfn = fn.encode("utf-8" if utf8 else "cp437", "replace")

    z64_len = len(z64v) * 8 + 4 if z64v else 0
    ret += struct.pack("<HH", len(bfn), z64_len)

    if h_pos is not None:
        # 2b comment, 2b diskno, 2b internal.attr,
        # 4b external.attr (infozip-linux: 0000(a481|ff81)) idk
        ret += b"\x00" * 10

        # 4b local-header-ofs
        ret += struct.pack("<L", min(h_pos, 0xFFFFFFFF))

    ret += bfn

    if z64v:
        ret += struct.pack("<HH" + "Q" * len(z64v), 1, len(z64v) * 8, *z64v)

    return ret


def gen_ecdr(items, cdir_pos, cdir_end):
    """
    summary of all file headers,
    usually the zipfile footer unless something clamps
    """

    ret = b"\x50\x4b\x05\x06"

    # 2b ndisk, 2b disk0
    ret += b"\x00" * 4

    cdir_sz = cdir_end - cdir_pos

    nitems = min(0xFFFF, len(items))
    csz = min(0xFFFFFFFF, cdir_sz)
    cpos = min(0xFFFFFFFF, cdir_pos)

    need_64 = nitems == 0xFFFF or 0xFFFFFFFF in [csz, cpos]

    # 2b tnfiles, 2b dnfiles, 4b dir sz, 4b dir pos
    ret += struct.pack("<HHLL", nitems, nitems, csz, cpos)

    # 2b comment length
    ret += b"\x00\x00"

    return [ret, need_64]


def gen_ecdr64(items, cdir_pos, cdir_end):
    """
    z64 end of central directory
    added when numfiles or a headerptr clamps
    """

    ret = b"\x50\x4b\x06\x06"

    # 8b own length from hereon
    ret += b"\x2c" + b"\x00" * 7

    # 2b spec-ver, 2b min-ver
    ret += b"\x1e\x03\x2d\x00"

    # 4b ndisk, 4b disk0
    ret += b"\x00" * 8

    # 8b tnfiles, 8b dnfiles, 8b dir sz, 8b dir pos
    cdir_sz = cdir_end - cdir_pos
    ret += struct.pack("<QQQQ", len(items), len(items), cdir_sz, cdir_pos)

    return ret


def gen_ecdr64_loc(ecdr64_pos):
    """
    z64 end of central directory locator
    points to ecdr64
    why
    """

    ret = b"\x50\x4b\x06\x07"

    # 4b cdisk, 8b start of ecdr64, 4b ndisks
    ret += struct.pack("<LQL", 0, ecdr64_pos, 1)

    return ret


class StreamZip(object):
    def __init__(self, top, fgen, utf8, pre_crc):
        self.top = top
        self.fgen = fgen
        self.utf8 = utf8
        self.pre_crc = pre_crc

        self.pos = 0
        self.items = []

    def _ct(self, buf):
        self.pos += len(buf)
        return buf

    def gen(self):
        for f in self.fgen:
            src = f["a"]
            name = f["n"]

            st = os.stat(fsenc(src))
            sz = st.st_size
            ts = st.st_mtime + 1

            h_pos = self.pos
            buf = gen_hdr(None, name, sz, ts, self.utf8, None, self.pre_crc)
            yield self._ct(buf)

            crc = 0
            with open(src, "rb") as f:
                while True:
                    buf = f.read(32768)
                    if not buf:
                        break

                    crc = zlib.crc32(buf, crc)
                    yield self._ct(buf)

            crc &= 0xFFFFFFFF

            self.items.append([name, sz, ts, crc, h_pos])

            z64 = sz >= 4 * 1024 * 1024 * 1024

            if z64 or not self.pre_crc:
                buf = gen_fdesc(sz, crc, z64)
                yield self._ct(buf)

        cdir_pos = self.pos
        for name, sz, ts, crc, h_pos in self.items:
            buf = gen_hdr(h_pos, name, sz, ts, self.utf8, crc, self.pre_crc)
            yield self._ct(buf)
        cdir_end = self.pos

        _, need_64 = gen_ecdr(self.items, cdir_pos, cdir_end)
        if need_64:
            ecdir64_pos = self.pos
            buf = gen_ecdr64(self.items, cdir_pos, cdir_end)
            yield self._ct(buf)

            buf = gen_ecdr64_loc(ecdir64_pos)
            yield self._ct(buf)

        ecdr, _ = gen_ecdr(self.items, cdir_pos, cdir_end)
        yield self._ct(ecdr)