"""JSON-file-backed config: Immich connection, selected album, and cursor
state (which photo /frame/image serves next)."""

from __future__ import annotations

import json
import os
from contextlib import contextmanager
from pathlib import Path
from threading import RLock
from typing import Iterator

from pydantic import BaseModel

CONFIG_PATH = Path(os.environ.get("CONFIG_PATH", "/data/config.json"))

# Reentrant so load()/save() can each take it internally for their own I/O
# while a caller also holds it for a whole locked() span (see below).
_lock = RLock()


class FrameConfig(BaseModel):
    immich_url: str = ""
    immich_api_key: str = ""
    management_token: str = ""  # gates the web UI (see main.py); empty = no gate, open on trusted LAN
    album_id: str = ""
    order: str = "sequential"  # or "shuffle"
    refresh_interval_s: int = 3600
    smart_crop_faces: bool = True
    # How the physical frame is hung: landscape (native), portrait,
    # landscape_flipped, portrait_flipped. Purely a server-side render
    # decision -- the device always receives native 800x480 bytes.
    orientation: str = "landscape"

    # Current photo + upcoming queue (see app/photo_queue.py). current_asset_set_at
    # is what lets the server decide "has it been long enough to advance" on its
    # own clock, independent of how/why the device asked for a photo.
    current_asset_id: str = ""
    current_asset_set_at: float = 0.0
    queue: list[str] = []
    queue_cursor: int = 0  # internal bookkeeping for sequential queue top-up; not user-facing
    queue_target_len: int = 20  # how many upcoming photos to keep queued/shown in the web UI
    history: list[str] = []  # bounded stack of previously-current asset ids, most recent last
    excluded_asset_ids: list[str] = []  # permanently removed from this frame's rotation (not deleted from Immich)

    # Last battery report from the device (POST /frame/battery); -1 = never
    # reported / not battery-powered. battery_as_of mirrors the
    # current_asset_set_at timestamp pattern.
    battery_percent: int = -1
    battery_as_of: float = 0.0
    # [timestamp, percent] pairs for the CURRENT discharge cycle only --
    # reset whenever a report jumps up enough to indicate a recharge (see
    # main.py). Feeds the "on battery for" and "estimated remaining"
    # numbers in the web UI's Device panel.
    battery_history: list = []

    # Device liveness/telemetry: last_seen is touched by every /frame/*
    # request; device_firmware_version comes from the X-Frame-Version
    # header the device sends with its config poll.
    last_seen: float = 0.0
    device_firmware_version: str = ""
    # Version parsed out of the most recently uploaded OTA image
    # (POST /api/firmware); "" = none uploaded yet.
    firmware_available_version: str = ""


def load() -> FrameConfig:
    with _lock:
        if not CONFIG_PATH.exists():
            cfg = FrameConfig()
        else:
            cfg = FrameConfig(**json.loads(CONFIG_PATH.read_text()))

    # IMMICH_URL/IMMICH_API_KEY/MANAGEMENT_TOKEN set in the environment
    # (e.g. docker-compose.yml, see docker-compose.yml.example) take
    # precedence over whatever's saved in CONFIG_PATH, so credentials never
    # need to go through the web UI.
    env_url = os.environ.get("IMMICH_URL")
    env_key = os.environ.get("IMMICH_API_KEY")
    env_token = os.environ.get("MANAGEMENT_TOKEN")
    if env_url:
        cfg.immich_url = env_url
    if env_key:
        cfg.immich_api_key = env_key
    if env_token:
        cfg.management_token = env_token

    return cfg


def save(cfg: FrameConfig) -> None:
    with _lock:
        CONFIG_PATH.parent.mkdir(parents=True, exist_ok=True)
        CONFIG_PATH.write_text(cfg.model_dump_json(indent=2))


@contextmanager
def locked() -> Iterator[None]:
    """Serializes an entire load-mutate-save cycle. load()/save() each
    only lock their own I/O, which isn't enough by itself: uvicorn
    dispatches sync routes to a thread pool, so two concurrent requests
    (e.g. the device's own poll landing alongside a web UI edit) can each
    load() the same on-disk state and the second save() silently clobber
    the first's changes. Route handlers that mutate config should wrap
    their whole load/mutate/save span in this."""
    with _lock:
        yield