"""Build a TRS-80 CoCo Program Pak cartridge ROM (.ccc) holding viewer + image.

The CoCo autostarts the cartridge at $C000.  Layout: viewer code, then the
6144-byte PMODE 4 image, padded to an 8KB ROM ($C000-$DFFF)."""

from __future__ import annotations

from . import viewer

CART_BASE = 0xC000
CART_SIZE = 0x2000           # 8 KB


def build_rom(data: bytes, vdg: int = 0xF8, display: str = "forever",
              seconds: int = 0) -> bytes:
    if len(data) != viewer.SCREEN_BYTES:
        raise ValueError(f"unexpected image length {len(data)}")
    vk = dict(vdg=vdg, display=display, seconds=seconds)
    code = viewer.build(0, **vk)                 # pass 1: measure code length
    data_src = CART_BASE + len(code)
    code = viewer.build(data_src, **vk)          # pass 2: real data address
    rom = code + bytes(data)
    if len(rom) > CART_SIZE:
        raise ValueError("viewer + image exceed the 8KB cartridge")
    return rom + bytes(CART_SIZE - len(rom))


def write_ccc(rom: bytes, path: str) -> str:
    with open(path, "wb") as f:
        f.write(rom)
    return path