"""Parsing/validation for the x-beacon-controls custom notification hint.

Sending apps opt into rich, embedded controls (beyond the spec's plain
fire-and-dismiss `actions` array) via a hint whose value is a JSON string —
chosen over a nested D-Bus variant struct so any app, in any language, can
produce it without touching GVariant construction. Advertised in
GetCapabilities as "x-beacon-controls" so senders can detect support and
fall back to plain `actions` against any other freedesktop-compliant daemon.

Shape:
  [
    {"type": "button", "id": "reply",  "label": "Reply"},
    {"type": "toggle", "id": "mute",   "label": "Mute",   "value": false},
    {"type": "slider", "id": "volume", "label": "Volume", "value": 40, "min": 0, "max": 100},
    {"type": "entry",  "id": "msg",    "label": "Message", "placeholder": "Type a reply..."}
  ]

Unknown "type"s and unrecognised extra keys are silently dropped rather than
erroring — forward-compatible with control types added later, and never lets
a malformed/hostile payload (any local session-bus process can call Notify)
crash the daemon.
"""

from __future__ import annotations

import json
from typing import Optional

_TYPES = {"button", "toggle", "slider", "entry"}
# a button auto-dismisses like a classic action by default; the stateful
# controls default to staying on-screen so you can keep adjusting them.
_DEFAULT_DISMISS = {"button": True, "toggle": False, "slider": False, "entry": False}


def parse_controls(raw: Optional[str]) -> list[dict]:
    if not raw:
        return []
    try:
        data = json.loads(raw)
    except (json.JSONDecodeError, TypeError):
        return []
    if not isinstance(data, list):
        return []

    out: list[dict] = []
    for item in data:
        if not isinstance(item, dict):
            continue
        ctype = item.get("type")
        cid = item.get("id")
        if ctype not in _TYPES or not isinstance(cid, str) or not cid:
            continue
        label = item.get("label")
        label = label if isinstance(label, str) else cid
        dismiss = item.get("dismiss")
        dismiss = bool(dismiss) if isinstance(dismiss, bool) else _DEFAULT_DISMISS[ctype]

        control = {"type": ctype, "id": cid, "label": label, "dismiss": dismiss}

        if ctype == "toggle":
            control["value"] = bool(item.get("value", False))
        elif ctype == "slider":
            control["value"] = _as_float(item.get("value"), 0.0)
            control["min"] = _as_float(item.get("min"), 0.0)
            control["max"] = _as_float(item.get("max"), 100.0)
            control["step"] = _as_float(item.get("step"), 1.0)
            if control["max"] <= control["min"]:
                control["max"] = control["min"] + 1.0
        elif ctype == "entry":
            placeholder = item.get("placeholder")
            control["placeholder"] = placeholder if isinstance(placeholder, str) else ""

        out.append(control)
    return out


def _as_float(value, default: float) -> float:
    try:
        return float(value)
    except (TypeError, ValueError):
        return default