"""
Host-side helpers for file_hashes.json (same format as led-driver/src/file_hashes.py).
"""

import hashlib
import json
import os

MANIFEST_VERSION = 1
MANIFEST_FILENAME = "file_hashes.json"
HASH_ALGO = "sha256"


def normalize_remote_path(remote_file: str) -> str:
    """Device-relative path with forward slashes (no leading slash)."""
    return remote_file.replace("\\", "/").lstrip("/")


def sha256_hex_file(path: str) -> str:
    h = hashlib.sha256()
    with open(path, "rb") as f:
        for chunk in iter(lambda: f.read(65536), b""):
            h.update(chunk)
    return h.hexdigest()


def parse_manifest(data: bytes) -> dict:
    """Return path -> hash map from manifest bytes."""
    try:
        doc = json.loads(data.decode("utf-8"))
    except (UnicodeDecodeError, json.JSONDecodeError, TypeError, ValueError):
        return {}
    if not isinstance(doc, dict):
        return {}
    files = doc.get("files")
    return dict(files) if isinstance(files, dict) else {}


def build_manifest_bytes(files: dict) -> bytes:
    doc = {
        "version": MANIFEST_VERSION,
        "algorithm": HASH_ALGO,
        "files": files,
    }
    return json.dumps(doc, separators=(",", ":")).encode("utf-8")