"""StereoConfig 与 JSON 配置加载。

规格 docs/双目测距方案.md：全部数值参数均为配置项（§2），默认值取文档
示例值。配置校验在构造期一次性完成，热路径不读 JSON。
"""

import json
from dataclasses import dataclass, fields
from pathlib import Path
from typing import Any, Dict, Tuple


@dataclass
class StereoConfig:
    # ---- 相机参数（校正后、对应原生分辨率，§3.1 / §4.3）----
    fx_px: float = 960.0
    fy_px: float = 960.0
    cx_px: float = 960.0
    cy_px: float = 540.0
    baseline_m: float = 0.06  # 基线 B

    # ---- 目标距离窗口：关联硬约束（§6），派生视差区间 [FB/z_max, FB/z_min] ----
    z_min_m: float = 1.0
    z_max_m: float = 50.0

    # ---- 关联阈值（§6）----
    vertical_tau_px: float = 2.0  # 垂直残差 tau_y
    height_ratio_tau: float = 0.25  # 相对高度差 tau_h

    # ---- 视差取点与有效性（§5）----
    disparity_min_px: float = 3.0  # D_min：D 低于此值直接无效
    range_tol_m: float = 2.0  # Z_tol：δZ <= Z_tol 才算有效
    disp_noise_px: float = 1.0  # δD（误差模型中的边缘定位噪声）
    use_center_fallback: bool = True  # 左边缘视差越窗时回退中心（§5.1）

    # ---- 可选时间滤波（§7，一阶低通 + 跳变重置）----
    filter_enabled: bool = False
    filter_alpha: float = 0.3
    filter_jump_ratio: float = 0.2  # 相对跳变超此门限则重置滤波器

    # ---- 诊断日志节流 ----
    warn_interval_s: float = 5.0

    def disparity_bounds_px(self) -> Tuple[float, float]:
        """关联用的视差区间 (lo, hi)：由 z_min/z_max 派生（§6）。"""
        fb = self.fx_px * self.baseline_m
        return fb / self.z_max_m, fb / self.z_min_m

    def __post_init__(self) -> None:
        _require(self.fx_px > 0.0, "fx_px", "必须为正")
        _require(self.fy_px > 0.0, "fy_px", "必须为正")
        _require(self.cx_px >= 0.0, "cx_px", "必须非负")
        _require(self.cy_px >= 0.0, "cy_px", "必须非负")
        _require(self.baseline_m > 0.0, "baseline_m", "必须为正")
        _require(0.0 < self.z_min_m < self.z_max_m, "z_min_m/z_max_m", "须满足 0 < z_min_m < z_max_m")
        _require(self.vertical_tau_px > 0.0, "vertical_tau_px", "必须为正")
        _require(self.height_ratio_tau > 0.0, "height_ratio_tau", "必须为正")
        _require(self.disparity_min_px > 0.0, "disparity_min_px", "必须为正")
        _require(self.range_tol_m > 0.0, "range_tol_m", "必须为正")
        _require(self.disp_noise_px > 0.0, "disp_noise_px", "必须为正")
        _require(0.0 < self.filter_alpha <= 1.0, "filter_alpha", "须落在 (0, 1]")
        _require(self.filter_jump_ratio >= 0.0, "filter_jump_ratio", "必须非负")
        _require(self.warn_interval_s >= 0.0, "warn_interval_s", "必须非负")


def load_from_json(path: str) -> StereoConfig:
    """从 JSON 文件构建配置。字段缺失或非法取值抛 ValueError（携带字段名）。"""
    with open(path, encoding="utf-8") as f:
        data: Dict[str, Any] = json.load(f)
    known = {field.name for field in fields(StereoConfig)}
    unknown = set(data) - known
    if unknown:
        raise ValueError(f"未知配置字段: {sorted(unknown)}")
    missing = known - set(data)
    if missing:
        raise ValueError(f"缺少配置字段: {sorted(missing)}")
    return StereoConfig(**data)


def _require(ok: bool, field_name: str, message: str) -> None:
    if not ok:
        raise ValueError(f"配置非法: {field_name} {message}")