#!/usr/bin/env python
#
# This program creates archives compatible with ESP32-S* ROM DFU implementation.
#
# The archives are in CPIO format. Each file which needs to be flashed is added to the archive
# as a separate file. In addition to that, a special index file, 'dfuinfo0.dat', is created.
# This file must be the first one in the archive. It contains binary structures describing each
# subsequent file (for example, where the file needs to be flashed/loaded).
#

import argparse
from collections import namedtuple
import hashlib
import os
import struct
import zlib

try:
    import typing
except ImportError:
    # Only used for type annotations
    pass

# CPIO ("new ASCII") format related things
CPIO_MAGIC = b"070701"
CPIO_STRUCT = b"=6s" + b"8s" * 13
CPIOHeader = namedtuple(
    "CPIOHeader",
    [
        "magic",
        "ino",
        "mode",
        "uid",
        "gid",
        "nlink",
        "mtime",
        "filesize",
        "devmajor",
        "devminor",
        "rdevmajor",
        "rdevminor",
        "namesize",
        "check",
    ],
)
CPIO_TRAILER = "TRAILER!!!"


def make_cpio_header(
    filename_len, file_len, is_trailer=False
):  # type: (int, int, bool) -> CPIOHeader
    """ Returns CPIOHeader for the given file name and file size """

    def as_hex(val):  # type: (int) -> bytes
        return "{:08x}".format(val).encode("ascii")

    hex_0 = as_hex(0)
    mode = hex_0 if is_trailer else as_hex(0o0100644)
    nlink = as_hex(1) if is_trailer else hex_0
    return CPIOHeader(
        magic=CPIO_MAGIC,
        ino=hex_0,
        mode=mode,
        uid=hex_0,
        gid=hex_0,
        nlink=nlink,
        mtime=hex_0,
        filesize=as_hex(file_len),
        devmajor=hex_0,
        devminor=hex_0,
        rdevmajor=hex_0,
        rdevminor=hex_0,
        namesize=as_hex(filename_len),
        check=hex_0,
    )


# DFU format related things
# Structure of one entry in dfuinfo0.dat
DFUINFO_STRUCT = b"<I I 64s 16s"
DFUInfo = namedtuple("DFUInfo", ["address", "flags", "name", "md5"])
DFUINFO_FILE = "dfuinfo0.dat"
# Structure which gets added at the end of the entire DFU file
DFUSUFFIX_STRUCT = b"<H H H H 3s B"
DFUSuffix = namedtuple(
    "DFUSuffix", ["bcd_device", "pid", "vid", "bcd_dfu", "sig", "len"]
)
ESPRESSIF_VID = 12346
# TODO: set PID based on the chip type (add a command line argument)
DFUSUFFIX_DEFAULT = DFUSuffix(0xFFFF, 0xFFFF, ESPRESSIF_VID, 0x0100, b"UFD", 16)
# This CRC32 gets added after DFUSUFFIX_STRUCT
DFUCRC_STRUCT = b"<I"


def dfu_crc(data, crc=0):  # type: (bytes, int) -> int
    """ Calculate CRC32/JAMCRC of data, with an optional initial value """
    uint32_max = 0xFFFFFFFF
    return uint32_max - (zlib.crc32(data, crc) & uint32_max)


def pad_bytes(b, multiple, padding=b"\x00"):  # type: (bytes, int, bytes) -> bytes
    """ Pad 'b' to a length divisible by 'multiple' """
    padded_len = (len(b) + multiple - 1) // multiple * multiple
    return b + padding * (padded_len - len(b))


class EspDfuWriter(object):
    def __init__(self, dest_file):  # type: (typing.BinaryIO) -> None
        self.dest = dest_file
        self.entries = []  # type: typing.List[bytes]
        self.index = []  # type: typing.List[DFUInfo]

    def add_file(self, flash_addr, path):  # type: (int, str) -> None
        """ Add file to be written into flash at given address """
        with open(path, "rb") as f:
            self._add_cpio_flash_entry(os.path.basename(path), flash_addr, f.read())

    def finish(self):  # type: () -> None
        """ Write DFU file """
        # Prepare and add dfuinfo0.dat file
        dfuinfo = b"".join([struct.pack(DFUINFO_STRUCT, *item) for item in self.index])
        self._add_cpio_entry(DFUINFO_FILE, dfuinfo, first=True)

        # Add CPIO archive trailer
        self._add_cpio_entry(CPIO_TRAILER, b"", trailer=True)

        # Combine all the entries and pad the file
        out_data = b"".join(self.entries)
        cpio_block_size = 10240
        out_data = pad_bytes(out_data, cpio_block_size)

        # Add DFU suffix and CRC
        out_data += struct.pack(DFUSUFFIX_STRUCT, *DFUSUFFIX_DEFAULT)
        out_data += struct.pack(DFUCRC_STRUCT, dfu_crc(out_data))

        # Finally write the entire binary
        self.dest.write(out_data)

    def _add_cpio_flash_entry(
        self, filename, flash_addr, data
    ):  # type: (str, int, bytes) -> None
        md5 = hashlib.md5()
        md5.update(data)
        self.index.append(
            DFUInfo(
                address=flash_addr,
                flags=0,
                name=filename.encode("utf-8"),
                md5=md5.digest(),
            )
        )
        self._add_cpio_entry(filename, data)

    def _add_cpio_entry(
        self, filename, data, first=False, trailer=False
    ):  # type: (str, bytes, bool, bool) -> None
        filename_b = filename.encode("utf-8") + b"\x00"
        cpio_header = make_cpio_header(len(filename_b), len(data), is_trailer=trailer)
        entry = pad_bytes(
            struct.pack(CPIO_STRUCT, *cpio_header) + filename_b, 4
        ) + pad_bytes(data, 4)
        if not first:
            self.entries.append(entry)
        else:
            self.entries.insert(0, entry)


def action_write(args):
    writer = EspDfuWriter(args.output_file)
    for addr, file in args.files:
        writer.add_file(addr, file)
    writer.finish()


class WriteArgsAction(argparse.Action):
    """ Helper for argparse to parse <address, filename> argument pairs """

    def __init__(self, *args, **kwargs):
        super(WriteArgsAction, self).__init__(*args, **kwargs)

    def __call__(self, parser, namespace, values, option_string=None):
        # TODO: add validation
        addr = 0
        result = []
        for i, value in enumerate(values):
            if i % 2 == 0:
                addr = int(value, 0)
            else:
                result.append((addr, value))

        setattr(namespace, self.dest, result)


def main():
    parser = argparse.ArgumentParser("mkdfu")

    # Provision to add "info" command
    subparsers = parser.add_subparsers(dest="command")
    write_parser = subparsers.add_parser("write")
    write_parser.add_argument("-o", "--output-file", type=argparse.FileType("wb"))
    write_parser.add_argument(
        "files", metavar="<address> <file>", action=WriteArgsAction, nargs="+"
    )

    args = parser.parse_args()
    print(repr(args))
    if args.command == "write":
        action_write(args)


if __name__ == "__main__":
    main()