#!/usr/bin/env python3
"""Minimal .bin -> .uf2 converter for the VersaMCU UF2 bootloader.

Standalone reimplementation of the block format microsoft/uf2-samdx1's
uf2conv.py produces (256-byte payload per 512-byte block); see
bootloader/inc/uf2format.h for the struct this has to match on the device
side. No external dependencies, Python 3 only.

Usage:
    python uf2conv.py <input.bin> <output.uf2> [--base 0x2000] [--family 0x68ed2b88]
"""
import argparse
import struct

UF2_MAGIC_START0 = 0x0A324655  # "UF2\n"
UF2_MAGIC_START1 = 0x9E5D5157  # randomly selected, must match the device
UF2_MAGIC_END = 0x0AB16F30  # ditto
UF2_FLAG_FAMILYID_PRESENT = 0x00002000

SAMD21_FAMILY_ID = 0x68ED2B88  # bootloader/inc/uf2format.h, #ifdef SAMD21
PAYLOAD_SIZE = 256  # bytes per block; matches the upstream uf2conv.py convention


def convert(bin_path: str, uf2_path: str, base_addr: int, family_id: int) -> int:
    with open(bin_path, "rb") as f:
        data = f.read()

    # Pad to a whole number of blocks; the bootloader writes payloadSize
    # bytes per block regardless of how much of it is real firmware.
    if len(data) % PAYLOAD_SIZE != 0:
        data += b"\x00" * (PAYLOAD_SIZE - len(data) % PAYLOAD_SIZE)
    num_blocks = len(data) // PAYLOAD_SIZE

    blocks = []
    for block_no in range(num_blocks):
        offset = block_no * PAYLOAD_SIZE
        chunk = data[offset : offset + PAYLOAD_SIZE]
        header = struct.pack(
            "<IIIIIIII",
            UF2_MAGIC_START0,
            UF2_MAGIC_START1,
            UF2_FLAG_FAMILYID_PRESENT,
            base_addr + offset,
            PAYLOAD_SIZE,
            block_no,
            num_blocks,
            family_id,
        )
        padding = b"\x00" * (476 - PAYLOAD_SIZE)
        footer = struct.pack("<I", UF2_MAGIC_END)
        blocks.append(header + chunk + padding + footer)

    with open(uf2_path, "wb") as f:
        f.write(b"".join(blocks))

    return num_blocks


def main() -> None:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("input", help="Path to the raw firmware .bin")
    parser.add_argument("output", help="Path to write the .uf2 to")
    parser.add_argument(
        "--base",
        type=lambda s: int(s, 0),
        default=0x2000,
        help="Flash base address the .bin was linked for (default: 0x2000, matches "
        "variants/versapad/linker_scripts/gcc/flash_with_bootloader.ld)",
    )
    parser.add_argument(
        "--family",
        type=lambda s: int(s, 0),
        default=SAMD21_FAMILY_ID,
        help="UF2 family ID (default: SAMD21, 0x68ed2b88)",
    )
    args = parser.parse_args()

    num_blocks = convert(args.input, args.output, args.base, args.family)
    print(f"Wrote {args.output}: {num_blocks} blocks, base 0x{args.base:08x}")


if __name__ == "__main__":
    main()