"""Format-Erkennung. Dispatcher: schaut auf Magic + Dateinamen, leitet an
den passenden Parser weiter. Liefert ein einheitliches Dict mit den Feldern,
die in die DB gehen.

Aktuell unterstützt:
  - Huawei update.app (vollständig)

Geplant (Stubs als Hinweis):
  - MediaTek scatter (txt + bin)
  - Samsung Odin (.tar.md5 mit AP/BL/CP/CSC)
  - Qualcomm rawprogram*.xml
"""
from __future__ import annotations

import json
import struct
from pathlib import Path

from . import huawei

HUAWEI_MAGIC = struct.pack("<I", huawei.UPDATE_MAGIC)


def _peek(path: Path, n: int = 0x200) -> bytes:
    try:
        with path.open("rb") as f:
            return f.read(n)
    except OSError:
        return b""


def identify(path: Path, root: Path) -> dict:
    """Rückgabe: dict für db.upsert. Enthält mindestens rel_path, size, mtime,
    format. Erkennungs-Misserfolg -> format='unknown'."""
    rel = str(path.resolve().relative_to(root.resolve())).replace("\\", "/")
    stat = path.stat()
    base: dict = {
        "rel_path": rel,
        "size": stat.st_size,
        "mtime": stat.st_mtime,
        "sha256": None,
        "format": "unknown",
        "vendor": None,
        "model": None,
        "soc": None,
        "version": None,
        "region": None,
        "extra_json": None,
    }

    head = _peek(path)

    # Huawei update.app — Magic taucht innerhalb der ersten 0x100 Bytes auf
    if HUAWEI_MAGIC in head[:0x200]:
        info = huawei.parse(path)
        if info is not None:
            base.update(
                format="huawei-update.app",
                vendor="Huawei",
                model=info.hardware_id or None,
                soc=huawei.soc_for(info.hardware_id) if info.hardware_id else None,
                version=info.earliest_date,  # bessere Quelle wenn verfügbar
                region=_region_from_filename(path.name),
                extra_json=json.dumps({
                    "section_count": info.section_count,
                    "has_boot": info.has_boot,
                    "has_system": info.has_system,
                    "first_sections": [
                        s.type for s in info.sections[:10]
                    ],
                }),
            )
            return base

    # Fallback: Filename-Heuristik (MTK scatter etc. — TODO)
    name = path.name.lower()
    if name.startswith("mt") and name.endswith(".txt"):
        base["format"] = "mtk-scatter-candidate"
    elif name.endswith(".tar.md5"):
        base["format"] = "samsung-odin-candidate"
        base["vendor"] = "Samsung"

    return base


def _region_from_filename(name: str) -> str | None:
    """Huawei-Region oft im Filename: '...C432B198...' -> 'C432'."""
    upper = name.upper()
    for marker in ("C432", "C636", "C185", "C233", "C605", "C10", "C461"):
        if marker in upper:
            return marker
    return None