"""Unpack a game archive (ISO9660 or ZIP) into a directory.

`bsdtar` (libarchive — ships with macOS and most Linuxes) reads ISO *and* ZIP, so
it is the primary path. A pure-Python `zipfile` fallback covers ZIPs when bsdtar
is missing. ISOs without bsdtar raise, with a clear hint.
"""

from __future__ import annotations

import os
import shutil
import subprocess
import tempfile
import zipfile

from .identify import is_pe


class UnpackError(RuntimeError):
    pass


def detect_kind(path: str) -> str:
    """One of: 'dir', 'iso', 'zip', 'pe', 'unknown' — by directory check then magic bytes."""
    if os.path.isdir(path):
        return "dir"
    try:
        with open(path, "rb") as fh:
            head = fh.read(4)
            # ISO9660: the primary volume descriptor carries 'CD001' at offset 0x8001.
            fh.seek(0x8001)
            iso_magic = fh.read(5)
    except OSError as e:
        raise UnpackError("cannot read {0}: {1}".format(path, e))
    if head[:4] in (b"PK\x03\x04", b"PK\x05\x06", b"PK\x07\x08"):
        return "zip"
    if iso_magic == b"CD001":
        return "iso"
    if is_pe(path):
        return "pe"
    return "unknown"


def _has_bsdtar() -> bool:
    return shutil.which("bsdtar") is not None


def _bsdtar_extract(archive: str, dest: str) -> None:
    try:
        proc = subprocess.run(
            ["bsdtar", "-x", "-f", archive, "-C", dest],
            stdout=subprocess.PIPE, stderr=subprocess.PIPE,
        )
    except OSError as e:
        raise UnpackError("bsdtar failed to launch: {0}".format(e))
    if proc.returncode != 0:
        raise UnpackError("bsdtar exited {0}: {1}".format(
            proc.returncode, proc.stderr.decode("utf-8", "replace").strip()))


def unpack(archive: str, dest: str | None = None) -> str:
    """Extract `archive` into `dest` (a fresh temp dir if None) and return that directory.

    Directories pass through unchanged. A bare PE/DLL is rejected here — callers that
    accept loose binaries should branch on `detect_kind` first."""
    kind = detect_kind(archive)
    if kind == "dir":
        return archive
    if kind == "pe":
        raise UnpackError("{0} is a bare PE image, not an archive".format(archive))
    if kind == "unknown":
        raise UnpackError("unrecognised archive (not ISO/ZIP): {0}".format(archive))

    created = dest is None
    dest = dest or tempfile.mkdtemp(prefix="ams_unpack_")
    try:
        if _has_bsdtar():
            _bsdtar_extract(archive, dest)
        elif kind == "zip":
            with zipfile.ZipFile(archive) as zf:
                zf.extractall(dest)
        else:  # iso without bsdtar
            raise UnpackError(
                "ISO extraction needs bsdtar (libarchive); install it or unpack the ISO manually")
    except Exception:
        if created:
            shutil.rmtree(dest, ignore_errors=True)
        raise
    return dest