"""Configuration loading with built-in defaults, overridable via config.yaml."""

from __future__ import annotations

from dataclasses import dataclass, field, fields, is_dataclass
from pathlib import Path
from typing import Any

import yaml


@dataclass
class CaptureConfig:
    sample_fps: float = 8.0
    processing_width: int = 960


@dataclass
class AudioConfig:
    sample_rate: int = 16000


@dataclass
class MotionConfig:
    blur_ksize: int = 21
    pixel_threshold: int = 12
    threshold: float = 0.02
    stable_min_duration_s: float = 1.0


@dataclass
class DocumentConfig:
    min_area_ratio: float = 0.04
    canny_low: int = 50
    canny_high: int = 150
    enhance: bool = False


@dataclass
class SpeechConfig:
    window_before_s: float = 3.0
    window_after_s: float = 5.0


@dataclass
class OutputConfig:
    dir: str = "./output"
    consume_dir: str | None = None


@dataclass
class Config:
    capture: CaptureConfig = field(default_factory=CaptureConfig)
    audio: AudioConfig = field(default_factory=AudioConfig)
    motion: MotionConfig = field(default_factory=MotionConfig)
    document: DocumentConfig = field(default_factory=DocumentConfig)
    speech: SpeechConfig = field(default_factory=SpeechConfig)
    output: OutputConfig = field(default_factory=OutputConfig)


def _merge_into(instance: Any, data: dict[str, Any]) -> Any:
    """Overlay a dict of overrides onto a dataclass instance, recursively."""
    for f in fields(instance):
        if f.name not in data:
            continue
        value = data[f.name]
        current = getattr(instance, f.name)
        if is_dataclass(current) and isinstance(value, dict):
            _merge_into(current, value)
        else:
            setattr(instance, f.name, value)
    return instance


def load_config(path: str | Path | None = None) -> Config:
    """Load config.yaml if present; unknown keys are ignored, missing keys use defaults."""
    cfg = Config()
    if path is None:
        return cfg
    path = Path(path)
    if not path.exists():
        raise FileNotFoundError(f"Config file not found: {path}")
    data = yaml.safe_load(path.read_text()) or {}
    return _merge_into(cfg, data)


def config_to_dict(cfg: Config) -> dict[str, Any]:
    """Serialize the effective config (for embedding in run reports)."""
    from dataclasses import asdict

    return asdict(cfg)