"""
Path Utilities
==============
Centralized helpers for building filesystem paths used across the pipeline.

- get_project_root()       → absolute path to the News-Whisper repo root
- get_timestamp_folder()   → human-readable timestamp for output dirs (e.g. "24_mar_10_37_pm")
- sanitize_query_folder()  → filesystem-safe folder name from search queries (Unicode-safe)
- find_latest_json()       → most recently modified JSON file in a directory
- find_latest_audio_dir()  → most recently modified timestamp subfolder for a category

These are imported via:
    from backend.common import get_project_root, get_timestamp_folder
or:
    from backend.common.paths import get_project_root
"""

import re
from pathlib import Path
from datetime import datetime
from typing import Optional


def get_project_root() -> Path:
    """Return the absolute path to the News-Whisper project root.

    Works regardless of which module calls it — always resolves to the
    directory containing main.py/app.py (two levels up from this file).
    """
    return Path(__file__).parent.parent.parent.absolute()


def get_timestamp_folder() -> str:
    """Generate a human-readable timestamp folder name.

    Format: {day}_{month}_{hour}_{minute}_{am/pm}
    Examples: "1_feb_2_30_pm", "15_jan_9_45_am"
    """
    now = datetime.now()
    day = now.day
    month = now.strftime("%b").lower()
    hour = now.strftime("%I").lstrip("0")
    minute = now.strftime("%M")
    am_pm = now.strftime("%p").lower()
    return f"{day}_{month}_{hour}_{minute}_{am_pm}"


def sanitize_query_folder(query: str) -> str:
    """Build a filesystem-safe folder name while preserving Unicode queries.

    Used for search query output directories. Hindi/Devanagari characters
    are preserved; only OS-illegal characters are replaced with underscores.

    Args:
        query: The raw search query string (e.g. "climate change" or "पुणे")

    Returns:
        A safe folder name string (e.g. "climate_change" or "पुणे")
    """
    safe = query.strip()
    safe = re.sub(r'[<>:"/\\|?*\x00-\x1F]', '_', safe)
    safe = re.sub(r'\s+', '_', safe)
    safe = re.sub(r'_+', '_', safe).strip(' ._')
    return safe or "query"


def find_latest_json(directory: Path) -> Optional[Path]:
    """Return the most recently modified JSON file in a directory.

    Returns None if the directory doesn't exist or contains no JSON files.
    """
    if not directory.exists():
        return None
    json_files = list(directory.glob("*.json"))
    return max(json_files, key=lambda f: f.stat().st_mtime) if json_files else None


def find_latest_audio_dir(base_dir: Path, category_name: str) -> Optional[Path]:
    """Return the most recently modified timestamp sub-directory for a category.

    Looks inside: base_dir/categories/{category_name_lower}/

    Returns None if the directory doesn't exist or has no subdirectories.
    """
    category_dir = base_dir / "categories" / category_name.lower().replace(" ", "_")
    if not category_dir.exists():
        return None
    dirs = [d for d in category_dir.iterdir() if d.is_dir()]
    return max(dirs, key=lambda d: d.stat().st_mtime) if dirs else None