"""Board state: the ordered collection of sound buttons.

Pure/headless (no audio or GUI imports) so add/remove/rename/persistence are unit-testable.
The GUI observes changes via an optional ``on_change`` callback and renders from
``board.buttons``.
"""

from __future__ import annotations

import os
from typing import Any, Callable, Optional

from config import default_config, load_config, save_config


def _base_label(file_path: str) -> str:
    """Default button label from a file path: the base name without extension."""
    return os.path.splitext(os.path.basename(file_path))[0]


class Board:
    def __init__(self, config_path: str):
        self.config_path = config_path
        cfg = load_config(config_path)
        self.output_device: Optional[str] = cfg["output_device"]
        self.volume: int = cfg["volume"]
        self.buttons: list[dict[str, Any]] = cfg["buttons"]
        self._next_id = self._compute_next_id()
        self.on_change: Optional[Callable[[], None]] = None

    # ---- id allocation -----------------------------------------------------
    def _compute_next_id(self) -> int:
        """Next free numeric suffix for ids of the form ``btn_NNN``."""
        highest = 0
        for b in self.buttons:
            bid = b.get("id", "")
            if bid.startswith("btn_"):
                try:
                    highest = max(highest, int(bid[4:]))
                except ValueError:
                    pass
        return highest + 1

    def _new_id(self) -> str:
        bid = f"btn_{self._next_id:03d}"
        self._next_id += 1
        return bid

    # ---- internal ----------------------------------------------------------
    def _index_of(self, button_id: str) -> int:
        for i, b in enumerate(self.buttons):
            if b["id"] == button_id:
                return i
        raise KeyError(button_id)

    def _changed(self):
        self.save()
        if self.on_change:
            self.on_change()

    # ---- mutations ---------------------------------------------------------
    def add_button(self, file_path: str, label: Optional[str] = None) -> dict[str, Any]:
        """Register a sound file as a new button (file is referenced, never copied)."""
        button = {
            "id": self._new_id(),
            "label": label if label else _base_label(file_path),
            "file_path": file_path,
        }
        self.buttons.append(button)
        self._changed()
        return button

    def remove_button(self, button_id: str) -> None:
        del self.buttons[self._index_of(button_id)]
        self._changed()

    def rename_button(self, button_id: str, new_label: str) -> None:
        new_label = new_label.strip()
        if not new_label:
            raise ValueError("label must not be empty")
        self.buttons[self._index_of(button_id)]["label"] = new_label
        self._changed()

    def get_button(self, button_id: str) -> dict[str, Any]:
        return self.buttons[self._index_of(button_id)]

    # ---- settings ----------------------------------------------------------
    def set_output_device(self, device_name: Optional[str]) -> None:
        self.output_device = device_name
        self._changed()

    def set_volume(self, volume: int) -> None:
        self.volume = int(max(0, min(100, volume)))
        self._changed()

    # ---- persistence -------------------------------------------------------
    def to_config(self) -> dict[str, Any]:
        cfg = default_config()
        cfg["output_device"] = self.output_device
        cfg["volume"] = self.volume
        cfg["buttons"] = [dict(b) for b in self.buttons]
        return cfg

    def save(self) -> None:
        save_config(self.config_path, self.to_config())