"""Build .d64/.d71/.d81 Commodore disk images with VICE's `c1541`.

We shell out to `c1541` rather than re-implementing CBM-DOS: it is battle-tested
and handles BAM/directory layout for all three formats correctly.
"""

from __future__ import annotations

import os
import shutil
import subprocess
import tempfile

FORMATS = {
    "d64": ("d64", 174848),   # 35 tracks, 664 blocks free
    "d71": ("d71", 349696),   # double sided
    "d81": ("d81", 819200),   # 3.5" 800K
}

# Per-format usable data budget (blocks * 254), conservative.
BLOCKS_FREE = {"d64": 664, "d71": 1328, "d81": 3160}


class DiskError(RuntimeError):
    pass


def have_c1541() -> bool:
    return shutil.which("c1541") is not None


def petscii_name(text: str, maxlen: int = 16) -> str:
    """Sanitise a host string into a legal CBM filename.

    Letters are forced to lower case: c1541 maps lower-case ASCII into the
    standard PETSCII letter range ($41-$5A), which renders as clean letters in a
    C64 directory listing, whereas upper-case ASCII lands in the shifted range
    that displays oddly.
    """
    out = []
    for ch in text.lower():
        if ch.isalnum() or ch in " -+.":
            out.append(ch)
    name = "".join(out).strip() or "8bitlenser"
    return name[:maxlen]


def fmt_from_path(path: str, override: str | None) -> str:
    if override:
        if override not in FORMATS:
            raise DiskError(f"unknown disk format: {override}")
        return override
    ext = os.path.splitext(path)[1].lower().lstrip(".")
    return ext if ext in FORMATS else "d64"


def build_disk(path: str, disk_format: str, disk_name: str, disk_id: str,
               files: list[tuple[str, bytes]]) -> str:
    """Create ``path`` of ``disk_format`` containing ``files`` (cbm_name, prg_bytes).

    The first file in the list lands first in the directory, so ``LOAD"*",8,1``
    loads it -- make that the viewer.
    """
    if not have_c1541():
        raise DiskError(
            "VICE's 'c1541' tool was not found on PATH.\n"
            "Install it with:  sudo apt install vice   (Debian/Ubuntu)\n"
            "or build from https://vice-emu.sourceforge.io/")

    total = sum(len(b) for _, b in files)
    budget = BLOCKS_FREE[disk_format] * 254
    if total > budget:
        raise DiskError(
            f"data ({total} bytes) exceeds {disk_format} capacity (~{budget} bytes); "
            f"use a larger disk format")

    vtype = FORMATS[disk_format][0]
    name = petscii_name(disk_name)
    did = petscii_name(disk_id, 2) or "01"
    path = os.path.abspath(path)
    if os.path.exists(path):
        os.remove(path)

    with tempfile.TemporaryDirectory() as td:
        cmd = ["c1541", "-format", f"{name},{did}", vtype, path]
        for i, (cbm, data) in enumerate(files):
            host = os.path.join(td, f"f{i}.prg")
            with open(host, "wb") as f:
                f.write(data)
            cmd += ["-write", host, petscii_name(cbm)]
        proc = subprocess.run(cmd, capture_output=True, text=True,
                              errors="replace")
        # c1541 prints a harmless "OPENCBM ... libopencbm.so" warning; only fail
        # if the image was not actually produced.
        if not os.path.exists(path):
            raise DiskError(f"c1541 failed:\n{proc.stdout}{proc.stderr}")
    return path


def directory(path: str) -> str:
    """Return the disk directory listing (for verification)."""
    proc = subprocess.run(["c1541", "-attach", path, "-dir"],
                          capture_output=True, text=True, errors="replace")
    return proc.stdout