"""Configuration and layout persistence for AR Display Manager."""
from __future__ import annotations

import json
from dataclasses import dataclass, field
from pathlib import Path

REPO_ROOT = Path(__file__).resolve().parents[1]
CONFIG_DIR = Path.home() / ".ar-autopilot" / "display_manager"
CONFIG_FILE = CONFIG_DIR / "config.json"
LAYOUT_FILE = CONFIG_DIR / "layout.json"


@dataclass
class AppExeConfig:
    """Path + launch args for one application."""
    exe: str = ""
    args: list[str] = field(default_factory=list)
    title_hint: str = ""   # substring to match window title when searching


_DEFAULT_EXES: dict[str, AppExeConfig] = {
    "autopilot": AppExeConfig(
        exe=str(
            REPO_ROOT / "display" / "build" / "windows" / "x64" / "runner"
            / "Release" / "display.exe"
        ),
        title_hint="AR Autopilot",
    ),
    "ecdis": AppExeConfig(exe="", title_hint="AR-ECDIS"),
    "compass": AppExeConfig(exe="", title_hint="Compass"),
    "gps": AppExeConfig(exe="", title_hint="GPS Navigator"),
}


@dataclass
class DisplayManagerConfig:
    apps: dict[str, AppExeConfig] = field(default_factory=dict)
    button_position: str = "top-right"   # top-right | top-left | bottom-right | bottom-left
    button_margin: int = 12              # px from screen edge
    autolaunch: bool = False             # launch all apps on startup (False = on-demand only)

    # ------------------------------------------------------------------ I/O
    @classmethod
    def load(cls) -> "DisplayManagerConfig":
        cfg = cls(apps=dict(_DEFAULT_EXES))
        if not CONFIG_FILE.exists():
            return cfg
        try:
            with open(CONFIG_FILE, encoding="utf-8") as f:
                data = json.load(f)
            cfg.button_position = data.get("button_position", cfg.button_position)
            cfg.button_margin = int(data.get("button_margin", cfg.button_margin))
            cfg.autolaunch = bool(data.get("autolaunch", cfg.autolaunch))
            for app_id, raw in data.get("apps", {}).items():
                cfg.apps[app_id] = AppExeConfig(
                    exe=raw.get("exe", ""),
                    args=raw.get("args", []),
                    title_hint=raw.get("title_hint", ""),
                )
        except Exception:
            pass
        return cfg

    def save(self) -> None:
        CONFIG_DIR.mkdir(parents=True, exist_ok=True)
        with open(CONFIG_FILE, "w", encoding="utf-8") as f:
            json.dump(
                {
                    "button_position": self.button_position,
                    "button_margin": self.button_margin,
                    "autolaunch": self.autolaunch,
                    "apps": {
                        k: {"exe": v.exe, "args": v.args, "title_hint": v.title_hint}
                        for k, v in self.apps.items()
                    },
                },
                f,
                indent=2,
            )


# --------------------------------------------------------------------------- Layout

class LayoutStore:
    """Persists {screen_serial → app_id} so layout survives restarts."""

    def __init__(self) -> None:
        self._data: dict[str, str] = {}
        self._load()

    def _load(self) -> None:
        if LAYOUT_FILE.exists():
            try:
                with open(LAYOUT_FILE, encoding="utf-8") as f:
                    self._data = json.load(f)
            except Exception:
                self._data = {}

    def get(self, screen_serial: str) -> str | None:
        return self._data.get(screen_serial)

    def set(self, screen_serial: str, app_id: str) -> None:
        self._data[screen_serial] = app_id
        self._save()

    def _save(self) -> None:
        CONFIG_DIR.mkdir(parents=True, exist_ok=True)
        with open(LAYOUT_FILE, "w", encoding="utf-8") as f:
            json.dump(self._data, f, indent=2)