"""DMS gemeinsame Helper & Konstanten — BUG-018 God-Object-Split."""

from __future__ import annotations

import os
import uuid

from fastapi import HTTPException

OFFICE_EXTENSIONS = {
    ".docx": "docx",
    ".xlsx": "xlsx",
    ".pptx": "pptx",
}

# Max file size: 100 MB
MAX_FILE_SIZE = 100 * 1024 * 1024


def _parse_uuid(val: str, field: str) -> uuid.UUID:
    try:
        return uuid.UUID(val)
    except (ValueError, TypeError):
        raise HTTPException(
            400, detail={"detail": f"Invalid {field}", "code": "invalid_id"}
        ) from None


def _file_storage_path(tenant_id: uuid.UUID, file_id: uuid.UUID) -> str:
    """Build relative storage path for a file (relative to storage base)."""
    return f"{tenant_id}/{file_id}"


def _get_file_extension(filename: str) -> str:
    """Extract lowercase extension including dot."""
    return os.path.splitext(filename)[1].lower()



def _sanitize_filename(filename: str) -> str:
    """Sanitize a filename for safe use in Content-Disposition headers."""
    import re
    # Extract basename only (strip any path components)
    safe = os.path.basename(filename.replace('\\', '/'))
    # Remove dangerous characters (keep alnum, dot, dash, underscore, space, unicode)
    safe = re.sub(r'[^a-zA-Z0-9.\-_\u00c0-\u017f\u4e00-\u9fff ]', '_', safe)
    # Collapse consecutive dots (path traversal prevention)
    safe = re.sub(r'\.{2,}', '_', safe)
    # Collapse multiple spaces
    safe = re.sub(r' {2,}', ' ', safe)
    # Strip leading dots and whitespace
    safe = safe.lstrip('.').strip()
    # Limit length
    if len(safe) > 200:
        name, ext = safe.rsplit('.', 1) if '.' in safe[:200] else (safe[:200], '')
        safe = name[:200] + ('.' + ext if ext else '')
    return safe or 'file'

# Blocked file extensions for security
BLOCKED_EXTENSIONS = {
    ".exe", ".bat", ".cmd", ".sh", ".jar", ".com", ".scr", ".msi",
    ".dll", ".vbs", ".ps1", ".app", ".bin", ".reg", ".inf",
    ".php", ".py", ".pl", ".asp", ".aspx", ".jsp", ".svg", ".htaccess",
    ".phtml", ".pht", ".cgi", ".cfm", ".erb",
}

# Allowed MIME types for upload validation
ALLOWED_MIME_PREFIXES = {
    "application/pdf",
    "application/msword",
    "application/vnd.openxmlformats-officedocument",
    "application/vnd.oasis.opendocument",
    "application/vnd.ms-excel",
    "application/vnd.ms-powerpoint",
    "application/zip",
    "application/gzip",
    "application/x-tar",
    "application/json",
    "application/xml",
    "application/rtf",
    "application/x-7z-compressed",
    "application/x-rar-compressed",
    "text/plain",
    "text/csv",
    "text/html",
    "text/markdown",
    "image/png",
    "image/jpeg",
    "image/gif",
    "image/webp",
    "image/bmp",
    "image/tiff",
    "image/x-icon",
    "audio/",
    "video/",
    "application/octet-stream",
}


def _is_blocked_filetype(filename: str) -> bool:
    """Check if a file has a blocked (dangerous) extension."""
    ext = os.path.splitext(filename)[1].lower()
    return ext in BLOCKED_EXTENSIONS


chunk_size = 1024 * 1024  # 1MB chunks for streaming uploads

# ─── Folders ───