"""
participants.py
Local participant records for InsightUX's multi-participant tracking.

A participant is NOT an InsightUX login/profile (see auth.py) — it's a
tracking SUBJECT that an owner creates to keep another person's sessions
separate from their own, e.g. a UX researcher running sessions on Rahul,
Priya, Aman. Participants never authenticate and always live nested inside
their owner's own folder (users/<owner_id>/participants/<id>/), not as a
sibling top-level directory — so a participant's data cannot structurally
exist outside their owner's folder at all.

One profile.json per participant folder, not a shared index file — a
participant folder is always a complete, self-contained, movable/deletable
unit, the same way users/<owner_id>/ already is relative to DATA_DIR.

No heavy imports (stdlib only) — same reasoning as theme.py/auth.py.
"""

import os
import json
import shutil
import uuid
from datetime import datetime, timezone


class ParticipantError(Exception):
    """User-facing failures (missing name, not found, ...)."""


def participant_dir(owner_dir, participant_id):
    return os.path.join(owner_dir, "participants", participant_id)


def _profile_path(owner_dir, participant_id):
    return os.path.join(participant_dir(owner_dir, participant_id), "profile.json")


def _save_profile(owner_dir, participant_id, record):
    path = _profile_path(owner_dir, participant_id)
    os.makedirs(os.path.dirname(path), exist_ok=True)
    tmp = path + ".tmp"
    with open(tmp, "w", encoding="utf-8") as f:
        json.dump(record, f, indent=2)
    os.replace(tmp, path)  # atomic on POSIX and Windows


def create_participant(owner_dir, name, notes=""):
    name = (name or "").strip()
    if not name:
        raise ParticipantError("Name is required.")
    participant_id = uuid.uuid4().hex[:12]
    record = {
        "id": participant_id,
        "name": name,
        "notes": (notes or "").strip(),
        "created_at": datetime.now(timezone.utc).isoformat(),
        "session_count": 0,
        "last_session_at": None,
    }
    _save_profile(owner_dir, participant_id, record)
    return record


def get_participant(owner_dir, participant_id):
    if not participant_id:
        return None
    path = _profile_path(owner_dir, participant_id)
    if not os.path.exists(path):
        return None
    try:
        with open(path, "r", encoding="utf-8") as f:
            return json.load(f)
    except (json.JSONDecodeError, OSError):
        return None


def list_participants(owner_dir):
    """Sorted by name — same predictable-picker convention as
    auth.list_profiles()."""
    root = os.path.join(owner_dir, "participants")
    out = []
    if os.path.isdir(root):
        for name in os.listdir(root):
            if not os.path.isdir(os.path.join(root, name)):
                continue
            record = get_participant(owner_dir, name)
            if record:
                out.append(record)
    out.sort(key=lambda p: p["name"].lower())
    return out


def update_participant(owner_dir, participant_id, name=None, notes=None):
    """In-place edit — name/notes are only touched when explicitly passed
    (None means "leave as-is"), so a caller updating just one field can't
    accidentally blank out the other. id/created_at/session_count/
    last_session_at are never touched here; renaming a participant must
    never look like a new one to anything reading session_count."""
    record = get_participant(owner_dir, participant_id)
    if not record:
        raise ParticipantError("That participant no longer exists.")
    if name is not None:
        name = name.strip()
        if not name:
            raise ParticipantError("Name is required.")
        record["name"] = name
    if notes is not None:
        record["notes"] = notes.strip()
    _save_profile(owner_dir, participant_id, record)
    return record


def delete_participant(owner_dir, participant_id):
    """Removes the participant's entire folder — profile.json, sessions/,
    calibration.pkl, everything nested under it. Irreversible; the caller
    (Api.delete_participant()) is expected to have already confirmed with
    the user and to have refused this while that participant is the
    active tracking subject mid-session."""
    if not participant_id:
        raise ParticipantError("No participant specified.")
    pdir = participant_dir(owner_dir, participant_id)
    if not os.path.isdir(pdir):
        raise ParticipantError("That participant no longer exists.")
    shutil.rmtree(pdir)


def touch_session_stats(owner_dir, participant_id):
    """Called once a session for this participant actually starts — keeps
    session_count/last_session_at current without needing to re-scan every
    session folder just to show them in the picker/details view later."""
    record = get_participant(owner_dir, participant_id)
    if not record:
        return
    record["session_count"] = record.get("session_count", 0) + 1
    record["last_session_at"] = datetime.now(timezone.utc).isoformat()
    _save_profile(owner_dir, participant_id, record)