"""Ralph UX flow state — short-lived per (adapter, chat, user) state for interactive menus.

Tracks state for multi-step flows like "user clicked Propose → next message is description".
Persisted in sessions/ralph_flow.json so it survives Echo Core restart.
TTL: 10 min default; cleanup_expired() drops stale entries.
"""

import json
import logging
import os
import tempfile
from datetime import datetime, timedelta, timezone
from pathlib import Path

log = logging.getLogger(__name__)

PROJECT_ROOT = Path(__file__).resolve().parent.parent
SESSIONS_DIR = PROJECT_ROOT / "sessions"
_STATE_FILE = SESSIONS_DIR / "ralph_flow.json"

DEFAULT_TTL_SECONDS = 600  # 10 minutes

# Step values used across adapters
STEP_INPUT_DESCRIPTION = "input_description"
STEP_IN_PLANNING = "in_planning"  # reserved for W2 (planning agent)


def _key(adapter: str, chat_id: str, user_id: str) -> str:
    return f"{adapter}:{chat_id}:{user_id}"


def _load() -> dict:
    try:
        text = _STATE_FILE.read_text(encoding="utf-8")
        if not text.strip():
            return {}
        return json.loads(text)
    except (FileNotFoundError, json.JSONDecodeError):
        return {}


def _save(data: dict) -> None:
    SESSIONS_DIR.mkdir(parents=True, exist_ok=True)
    fd, tmp_path = tempfile.mkstemp(
        dir=SESSIONS_DIR, prefix=".ralph_flow_", suffix=".json"
    )
    try:
        with os.fdopen(fd, "w", encoding="utf-8") as f:
            json.dump(data, f, indent=2, ensure_ascii=False)
            f.write("\n")
        os.replace(tmp_path, _STATE_FILE)
    except BaseException:
        try:
            os.unlink(tmp_path)
        except OSError:
            pass
        raise


def _is_expired(entry: dict, now: datetime | None = None) -> bool:
    expires_at = entry.get("expires_at")
    if not expires_at:
        return False
    try:
        return datetime.fromisoformat(expires_at) < (now or datetime.now(timezone.utc))
    except ValueError:
        return True


def get_state(adapter: str, chat_id: str, user_id: str) -> dict | None:
    """Return current state or None if absent/expired. Drops expired entries on read."""
    data = _load()
    key = _key(adapter, chat_id, user_id)
    entry = data.get(key)
    if entry is None:
        return None
    if _is_expired(entry):
        del data[key]
        _save(data)
        return None
    return entry


def set_state(
    adapter: str,
    chat_id: str,
    user_id: str,
    step: str,
    project: str | None = None,
    ttl_seconds: int = DEFAULT_TTL_SECONDS,
    **extras,
) -> None:
    """Set state for (adapter, chat, user). Overwrites any previous state."""
    data = _load()
    expires_at = (
        datetime.now(timezone.utc) + timedelta(seconds=ttl_seconds)
    ).isoformat()
    entry: dict = {"step": step, "expires_at": expires_at}
    if project is not None:
        entry["project"] = project
    entry.update(extras)
    data[_key(adapter, chat_id, user_id)] = entry
    _save(data)


def clear_state(adapter: str, chat_id: str, user_id: str) -> bool:
    """Clear state. Returns True if anything was cleared."""
    data = _load()
    key = _key(adapter, chat_id, user_id)
    if key in data:
        del data[key]
        _save(data)
        return True
    return False


def cleanup_expired() -> int:
    """Drop all expired entries. Returns count dropped."""
    data = _load()
    now = datetime.now(timezone.utc)
    dropped = 0
    for k in list(data.keys()):
        if _is_expired(data[k], now=now):
            del data[k]
            dropped += 1
    if dropped:
        _save(data)
    return dropped