"""
Persona routing — per-request identity context.

Each HTTP request sets the active persona via set_persona() at entry.
Everything downstream (context_loader, tools, session_logger) calls
persona_path() to get the right working directory without needing to
pass the name through every function signature.

Directory layout:
  personas/
    inara/        ← Scott's agent
    holly/        ← Second persona (add IDENTITY.md + SOUL.md + USER.md)
    ...

Background tasks (cron runner, memory distiller) don't have a request
context — they pass persona by name explicitly to persona_path(name).

Future Aether integration: persona name maps to account_id_random.
Replace the directory lookup in persona_path() with a DB lookup at
that point; the ContextVar contract stays the same.
"""

import re
from contextvars import ContextVar
from pathlib import Path

from config import settings

_current: ContextVar[str] = ContextVar("persona", default="inara")

# Only alphanumeric + underscore + hyphen, 1–32 chars.  Prevents path traversal.
_VALID = re.compile(r"^[a-zA-Z0-9_-]{1,32}$")


def set_persona(name: str) -> None:
    """Set the active persona for the current async task/coroutine."""
    _current.set(name)


def get_persona() -> str:
    """Return the active persona name for the current task."""
    return _current.get()


def persona_path(name: str | None = None) -> Path:
    """
    Return the filesystem path for a persona's data directory.

    If name is omitted, uses the persona set for the current request.
    Pass name explicitly for background tasks (cron, distiller).
    """
    return settings.personas_root() / (name or _current.get())


def list_personas() -> list[str]:
    """Return all persona names that have an IDENTITY.md (i.e. are real personas)."""
    root = settings.personas_root()
    if not root.exists():
        return []
    return sorted(
        d.name for d in root.iterdir()
        if d.is_dir() and (d / "IDENTITY.md").exists()
    )


def validate(name: str) -> str:
    """
    Validate a persona name from an untrusted source (e.g. HTTP request).
    Returns the name if valid, raises ValueError otherwise.
    """
    if not _VALID.match(name):
        raise ValueError(
            f"Invalid persona name {name!r}. "
            f"Use letters, digits, underscores, or hyphens (max 32 chars)."
        )
    if not (settings.personas_root() / name / "IDENTITY.md").exists():
        raise ValueError(f"Unknown persona: {name!r}")
    return name