#!/usr/bin/python3
# -*- encoding: Utf-8 -*-
from pathlib import Path

from google.protobuf.descriptor_pb2 import FileDescriptorProto
from google.protobuf.internal.decoder import _DecodeVarint

from extract.descpb_to_proto import descpb_to_proto


def walk_binary(binr):
    with open(binr, "rb") as fd:
        binr = fd.read()

    # Search for:
    # ".proto" or ".protodevel", as part of the "name" (1) field
    cursor = 0
    while cursor < len(binr):
        cursor = binr.find(b".proto", cursor)

        if cursor == -1:
            break
        cursor += len(".proto")
        cursor += (binr[cursor : cursor + 5] == b"devel") * 5

        # Search back for the (1, length-delimited) marker
        start = binr.rfind(b"\x0a", max(cursor - 1024, 0), cursor)

        if start > 0 and binr[start - 1] == 0x0A == (cursor - start - 1):
            start -= 1

        # Check whether length byte is coherent
        if start == -1:
            continue
        varint, end = _DecodeVarint(binr, start + 1)
        if cursor - end != varint:
            continue

        # Look just after for subsequent markers
        tags = b"\x12\x1a\x22\x2a\x32\x3a\x42\x4a\x50\x58\x62"
        if binr[cursor] not in tags:
            continue

        while cursor < len(binr) and binr[cursor] in tags:
            tags = tags[tags.index(binr[cursor]) :]

            varint, end = _DecodeVarint(binr, cursor + 1)
            cursor = end + varint * (binr[cursor] & 0b111 == 2)

        # Parse descriptor
        proto = FileDescriptorProto()
        proto.ParseFromString(binr[start:cursor])

        # Convert to ascii
        yield descpb_to_proto(proto)


if __name__ == "__main__":
    base = Path(__file__).resolve().parent
    proto_base = base / "proto"
    proto_base.mkdir(exist_ok=True)

    for name, proto in walk_binary("./mgt"):
        if (
            name.startswith("google")
            or name.startswith("grpc")
            or name.startswith("github.com/golang/protobuf")
        ):
            continue
        p = proto_base / name
        p.parent.mkdir(parents=True, exist_ok=True)
        print(p)
        with open(p, "w") as fd:
            fd.write(proto)