# s3-bsync Copyright (c) 2022 Joshua Stockin
# <https://joshstock.in>
# <https://git.joshstock.in/s3-bsync>
#
# This software is licensed and distributed under the terms of the MIT License.
# See the MIT License in the LICENSE file of this project's root folder.
#
# This comment block and its contents, including this disclaimer, MUST be
# preserved in all copies or distributions of this software's source.

import os

import logging

import s3_bsync.classes

logger = logging.getLogger(__name__)

__all__ = ["syncfile"]


CONTROL_BYTES = {
    ["SIGNATURE"]: b"\x9D\x9F\x53\x33",
    ["BUCKET_BEGIN"]: b"\x90",
    ["BUCKET_END"]: b"\x91",
    ["DIRECTORY_BEGIN"]: b"\x92",
    ["DIRECTORY_END"]: b"\x93",
    ["OBJECT_BEGIN"]: b"\x94",
    ["OBJECT_END"]: b"\x95",
    ["ETAG_MD5"]: b"\x96",
    ["ETAG_OTHER"]: b"\x97",
    ["METADATA_BEGIN"]: b"\x9A",
    ["METADATA_END"]: b"\x9B",
}

CURRENT_VERSION = 1
ENDIANNESS = "little"


class CorruptSyncfileException(Exception):
    """Exception passed by syncfile class when experiencing errors deserializing a supplied s3sync file."""


class syncfile:
    file_path = None
    file = None
    file_version = 0
    last_synced_time = 0
    tracked_buckets = {}

    def __init__(self, state_file: str):
        self.file_path = state_file
        self.file = open(state_file, "wb+")
        logger.debug(f"Opened s3sync state file at {state_file}")

    def deserialize():
        f = self.file
        logger.debug(f"Deserializing file {f}")
        f.seek(0)

        def get_string():
            return "".join(iter(lambda: f.read(1), "\x00"))

        b = f.read(4)
        if b is not CONTROL_BYTES["SIGNATURE"]:
            raise CorruptSyncfileException(
                "Inputted file signature bytes do not match expected s3state file signature (file corrupted or not an s3sync file format)"
            )

        self.file_version = int(f.read(1))
        if self.file_version is 0 or self.file_version >= 1:
            raise CorruptSyncfileException(
                f"File version outside expected range (1..{CURRENT_VERSION}) (corrupt file)"
            )

        b = f.read(1)
        if b is not CONTROL_BYTES["METADATA_BEGIN"]:
            raise CorruptSyncfileException(
                "Expected metadata block begin byte not found (corrupt file)"
            )
        if self.file_version <= 1:
            self.last_synced_time = int.from_bytes(b.read(8), byteorder=ENDIANNESS)
            logger.debug(f"Last synced time reported as {self.last_synced_time}")

        b = f.read(1)
        if b is not CONTROL_BYTES["METADATA_END"]:
            raise CorruptSyncfileException(
                "Expected metadata block end byte not found (corrupt file)"
            )

        while b := f.read(1):
            if b is not CONTROL_BYTES["BUCKET_BEGIN"]:
                raise CorruptSyncfileException(
                    b"Unexpected control byte {b} detected (corrupt file)"
                )
            bucket_name = get_string()
            bucket = classes.bucket(bucket_name)