"""
Path utilities for cross-session / cross-project isolation.

Goal:
- Avoid file overwrites across concurrent users/projects by namespacing all temp artifacts
  under temp/projects/{project_id}/...
- Provide safe unique filename helpers.
"""

from __future__ import annotations

import os
import re
import time
import uuid
from pathlib import Path
from typing import Optional

import config


_SAFE_CHARS_RE = re.compile(r"[^A-Za-z0-9._-]+")


def sanitize_filename(name: str) -> str:
    """Keep only safe filename characters and strip path separators."""
    if not isinstance(name, str):
        return "file"
    name = name.replace("\\", "_").replace("/", "_").strip()
    name = _SAFE_CHARS_RE.sub("_", name)
    return name or "file"


def ensure_dir(path: Path) -> Path:
    path.mkdir(parents=True, exist_ok=True)
    return path


def project_root(project_id: str) -> Path:
    pid = sanitize_filename(project_id or "UNKNOWN")
    return ensure_dir(config.TEMP_DIR / "projects" / pid)


def project_upload_dir(project_id: str) -> Path:
    return ensure_dir(project_root(project_id) / "uploads")


def project_images_dir(project_id: str) -> Path:
    return ensure_dir(project_root(project_id) / "images")


def project_videos_dir(project_id: str) -> Path:
    return ensure_dir(project_root(project_id) / "videos")


def project_audio_dir(project_id: str) -> Path:
    return ensure_dir(project_root(project_id) / "audio")


def project_compose_dir(project_id: str, output_name: str) -> Path:
    out = sanitize_filename(output_name or f"compose_{int(time.time())}")
    return ensure_dir(project_root(project_id) / "compose" / out)


def unique_filename(
    prefix: str,
    ext: str,
    project_id: Optional[str] = None,
    scene_id: Optional[int] = None,
    extra: Optional[str] = None,
) -> str:
    """
    Build a unique filename.
    Example: scene_1_PROJ-xxx_173..._a1b2c3.mp4
    """
    pfx = sanitize_filename(prefix or "file")
    e = (ext or "").lstrip(".") or "bin"
    pid = sanitize_filename(project_id) if project_id else None
    sid = str(int(scene_id)) if scene_id is not None else None
    ex = sanitize_filename(extra) if extra else None
    ts = str(int(time.time() * 1000))
    rnd = uuid.uuid4().hex[:8]
    parts = [pfx]
    if sid:
        parts.append(f"s{sid}")
    if pid:
        parts.append(pid)
    if ex:
        parts.append(ex)
    parts.extend([ts, rnd])
    return f"{'_'.join(parts)}.{e}"