#!/usr/bin/env python3

# SPDX-FileCopyrightText: © 2024 ZeldaRET
# SPDX-License-Identifier: CC0-1.0

from __future__ import annotations

import hashlib
import io
import struct
from pathlib import Path
import argparse

import crunch64
import ipl3checksum
import zlib


def decompress_zlib(data: bytes) -> bytes:
    decomp = zlib.decompressobj(-zlib.MAX_WBITS)
    output = bytearray()
    output.extend(decomp.decompress(data))
    while decomp.unconsumed_tail:
        output.extend(decomp.decompress(decomp.unconsumed_tail))
    output.extend(decomp.flush())
    return bytes(output)


def decompress(data: bytes, is_zlib_compressed: bool) -> bytes:
    if is_zlib_compressed:
        return decompress_zlib(data)
    return crunch64.yaz0.decompress(data)


FILE_TABLE_OFFSET = {
    "gc-eu-mq-dbg":     0x12F70,
}

VERSIONS_MD5S = {
    "gc-eu-mq-dbg":     "f0b7f35375f9cc8ca1b2d59d78e35405",
}


def round_up(n, shift):
    mod = 1 << shift
    return (n + mod - 1) >> shift << shift


def as_word_list(b) -> list[int]:
    return [i[0] for i in struct.iter_unpack(">I", b)]


def read_dmadata_entry(file_content: bytearray, addr: int) -> list[int]:
    return as_word_list(file_content[addr : addr + 0x10])


def read_dmadata(file_content: bytearray, start) -> list[list[int]]:
    dmadata = []
    addr = start
    entry = read_dmadata_entry(file_content, addr)
    i = 0
    while any([e != 0 for e in entry]):
        dmadata.append(entry)
        addr += 0x10
        i += 1
        entry = read_dmadata_entry(file_content, addr)
    return dmadata


def update_crc(decompressed: io.BytesIO) -> io.BytesIO:
    print("Recalculating crc...")
    calculated_checksum = ipl3checksum.CICKind.CIC_X105.calculateChecksum(
        bytes(decompressed.getbuffer())
    )
    new_crc = struct.pack(f">II", calculated_checksum[0], calculated_checksum[1])

    decompressed.seek(0x10)
    decompressed.write(new_crc)
    return decompressed


def decompress_rom(
    file_content: bytearray, dmadata_addr: int, dmadata: list[list[int]], version: str
) -> bytearray:
    rom_segments = {}  # vrom start : data s.t. len(data) == vrom_end - vrom_start
    new_dmadata = bytearray()  # new dmadata: {vrom start , vrom end , vrom start , 0}

    decompressed = io.BytesIO(b"")

    for v_start, v_end, p_start, p_end in dmadata:
        if p_start == 0xFFFFFFFF and p_end == 0xFFFFFFFF:
            new_dmadata.extend(struct.pack(">IIII", v_start, v_end, p_start, p_end))
            continue
        if p_end == 0:  # uncompressed
            rom_segments.update(
                {v_start: file_content[p_start : p_start + v_end - v_start]}
            )
        else:  # compressed
            rom_segments.update(
                {
                    v_start: decompress(
                        file_content[p_start:p_end], version in {"ique-cn", "ique-zh"}
                    )
                }
            )
        new_dmadata.extend(struct.pack(">IIII", v_start, v_end, v_start, 0))

    # write rom segments to vaddrs
    for vrom_st, data in rom_segments.items():
        decompressed.seek(vrom_st)
        decompressed.write(data)
    # write new dmadata
    decompressed.seek(dmadata_addr)
    decompressed.write(new_dmadata)
    # pad to size
    padding_end = round_up(dmadata[-1][1], 14)
    decompressed.seek(padding_end - 1)
    decompressed.write(bytearray([0]))
    # re-calculate crc
    return bytearray(update_crc(decompressed).getbuffer())


def get_str_hash(byte_array):
    return str(hashlib.md5(byte_array).hexdigest())


def check_existing_rom(rom_path: Path, correct_str_hash: str):
    # If the baserom exists and is correct, we don't need to change anything
    if rom_path.exists():
        if get_str_hash(rom_path.read_bytes()) == correct_str_hash:
            return True
    return False


def word_swap(file_content: bytearray) -> bytearray:
    words = str(int(len(file_content) / 4))
    little_byte_format = "<" + words + "I"
    big_byte_format = ">" + words + "I"
    tmp = struct.unpack_from(little_byte_format, file_content, 0)
    struct.pack_into(big_byte_format, file_content, 0, *tmp)
    return file_content


def byte_swap(file_content: bytearray) -> bytearray:
    halfwords = str(int(len(file_content) / 2))
    little_byte_format = "<" + halfwords + "H"
    big_byte_format = ">" + halfwords + "H"
    tmp = struct.unpack_from(little_byte_format, file_content, 0)
    struct.pack_into(big_byte_format, file_content, 0, *tmp)
    return file_content


def per_version_fixes(file_content: bytearray, version: str) -> bytearray:
    if version == "gc-eu-mq-dbg":
        # Strip the overdump
        print("Stripping overdump...")
        file_content = file_content[0:0x3600000]

        # Patch the header
        print("Patching header...")
        file_content[0x3E] = 0x50
    return file_content


def pad_rom(file_content: bytearray, dmadata: list[list[int]]) -> bytearray:
    padding_start = round_up(dmadata[-1][1], 12)
    padding_end = round_up(dmadata[-1][1], 14)
    print(f"Padding from {padding_start:X} to {padding_end:X}...")
    for i in range(padding_start, padding_end):
        file_content[i] = 0xFF
    return file_content

# Determine if we have a ROM file
ROM_FILE_EXTENSIONS = ["z64", "n64", "v64"]

def find_baserom(version: str) -> Path | None:
    for rom_file_ext_lower in ROM_FILE_EXTENSIONS:
        for rom_file_ext in (rom_file_ext_lower, rom_file_ext_lower.upper()):
            rom_file_name_candidate =  Path(f"baseroms/{version}/baserom.{rom_file_ext}")
            if rom_file_name_candidate.exists():
                return rom_file_name_candidate
    return None


def main():
    description = "Convert a rom that uses dmadata to an uncompressed one."

    parser = argparse.ArgumentParser(description=description)
    parser.add_argument("version", help="Version of the game to decompress.", choices=list(VERSIONS_MD5S.keys()))

    args = parser.parse_args()

    version = args.version

    uncompressed_path = Path(f"baseroms/{version}/baserom-decompressed.z64")

    file_table_offset = FILE_TABLE_OFFSET[version]
    correct_str_hash = VERSIONS_MD5S[version]

    if check_existing_rom(uncompressed_path, correct_str_hash):
        print("Found valid baserom - exiting early")
        return

    rom_file_name = find_baserom(version)

    if rom_file_name is None:
        path_list = [
            f"baseroms/{version}/baserom.{rom_file_ext}" for rom_file_ext in ROM_FILE_EXTENSIONS
        ]
        print(f"Error: Could not find {','.join(path_list)}.")
        exit(1)

    # Read in the original ROM
    print(f"File '{rom_file_name}' found.")

    file_content = bytearray(rom_file_name.read_bytes())

    # Check if ROM needs to be byte/word swapped
    # Little-endian
    if file_content[0] == 0x40:
        # Word Swap ROM
        print("ROM needs to be word swapped...")
        file_content = word_swap(file_content)
        print("Word swapping done.")

    # Byte-swapped
    elif file_content[0] == 0x37:
        # Byte Swap ROM
        print("ROM needs to be byte swapped...")
        file_content = byte_swap(file_content)
        print("Byte swapping done.")

    file_content = per_version_fixes(file_content, version)

    dmadata = read_dmadata(file_content, file_table_offset)
    # Decompress
    if any(
        [
            b != 0
            for b in file_content[
                file_table_offset + 0xAC : file_table_offset + 0xAC + 0x4
            ]
        ]
    ):
        print("Decompressing rom...")
        file_content = decompress_rom(file_content, file_table_offset, dmadata, version)

    file_content = pad_rom(file_content, dmadata)

    # Check to see if the ROM is a "vanilla" ROM
    str_hash = get_str_hash(file_content)
    if str_hash != correct_str_hash:
        print(
            f"Error: Expected a hash of {correct_str_hash} but got {str_hash}. The baserom has probably been tampered, find a new one"
        )

        if version == "gc-eu-mq-dbg":
            if str_hash == "32fe2770c0f9b1a9cd2a4d449348c1cb":
                print(
                    "The provided baserom is a rom which has been edited with ZeldaEdit and is not suitable for use with decomp. Find a new one."
                )

        exit(1)

    # Write out our new ROM
    print(f"Writing new ROM {uncompressed_path}.")
    uncompressed_path.write_bytes(file_content)

    print("Done!")


if __name__ == "__main__":
    main()