import struct
from dataclasses import dataclass

@dataclass
class RegionArrayTile:
    last_region: int
    z_clear: int
    flush_accumulate: int
    tile_y_position: int
    tile_x_position: int

    def __init__(self, value):
        assert (value >> 29) & 1 == 0, value
        assert (value >> 14) & 0x3fff == 0, value
        assert (value >> 0) & 0b11 == 0, value
        self.last_region = (value >> 31) & 0b1
        self.z_clear = (value >> 30) & 0b1
        self.flush_accumulate = (value >> 28) & 0b1
        self.tile_y_position = (value >> 8) & 0b111111
        self.tile_x_position = (value >> 2) & 0b111111

@dataclass
class RegionArrayPointer:
    empty_ptr: int
    pointer_to_object_list: int

    def __init__(self, value):
        assert (value >> 24) & 0x7f == 0
        assert (value >> 0) & 0b11 == 0
        self.empty_ptr = (value >> 31) & 1
        self.pointer_to_object_list = value & 0xffffff

@dataclass
class RegionArrayEntry:
    tile: RegionArrayTile
    opaque_list_pointer: RegionArrayPointer
    opaque_modifier_volume_list_pointer: RegionArrayPointer
    translucent_list_pointer: RegionArrayPointer
    translucent_modifier_volume_list_pointer: RegionArrayPointer
    punch_through_list_pointer: RegionArrayPointer

def decode_region_array_entry(mem, offset):
    next_offset = offset + 6 * 4
    tile, *pointers = struct.unpack("<IIIIII", mem[offset:next_offset])
    return next_offset, RegionArrayEntry(
        RegionArrayTile(tile),
        *map(RegionArrayPointer, pointers),
    )

def decode_region_array_entries(mem, offset):
    entries = []
    while True:
        offset, entry = decode_region_array_entry(mem, offset)
        entries.append(entry)
        if entry.tile.last_region:
            break
    return entries