"""问题一算例：官方示例目录 ``examples/q1`` + 随机交会算例。"""

from __future__ import annotations

import json
import math
import random

from project.common import ROOT

EXAMPLE_DIR = ROOT / "examples" / "q1"
EXAMPLE_IDS = ("normal", "triangle", "poor", "segment", "empty")


def load_examples() -> list[dict]:
    """读取固定算例；缺文件时跳过，保证离线可跑。"""
    cases = []
    for key in EXAMPLE_IDS:
        path = EXAMPLE_DIR / f"{key}.json"
        if not path.exists():
            continue
        raw = json.loads(path.read_text(encoding="utf-8-sig"))
        cases.append({
            "id": raw.get("id", key),
            "name": raw.get("name", key),
            "source": "examples/q1",
            "measurements": [
                {"x": float(row["x"]), "y": float(row["y"]),
                 "bearing_deg": float(row["bearing_deg"]),
                 "half_angle_deg": float(row.get("half_angle_deg", 1.0))}
                for row in raw["measurements"]
            ],
        })
    return cases


def random_case(seed: int) -> dict:
    """随机三点/四点交会：目标在 Ω 内，测站分布在不同象限。

    仅生成"区域有界且非退化"的良态算例，避免参考网格因细长区域失效；
    生成后由 ``compare`` 再用最优实现复核状态。
    """
    rng = random.Random(seed)
    target = (rng.uniform(-900, 900), rng.uniform(-900, 900))
    count = rng.choice((3, 3, 4, 5))
    stations = []
    base_angle = rng.uniform(0, 360)
    for index in range(count):
        angle = base_angle + 360 * index / count + rng.uniform(-25, 25)
        radius = rng.uniform(500, 1100)
        stations.append((target[0] + radius * math.cos(math.radians(angle)),
                         target[1] + radius * math.sin(math.radians(angle))))
    measurements = []
    for (sx, sy) in stations:
        true_bearing = math.degrees(math.atan2(target[1] - sy, target[0] - sx)) % 360.0
        # 观测误差固定在同一地点、落在 ±1° 内；读数保留两位小数
        error = rng.uniform(-0.9, 0.9)
        measurements.append({"x": round(sx, 2), "y": round(sy, 2),
                             "bearing_deg": round((true_bearing + error) % 360.0, 2),
                             "half_angle_deg": 1.0})
    return {"id": f"rand-{seed}", "name": "随机交会", "source": "synthetic",
            "target": [round(target[0], 2), round(target[1], 2)],
            "measurements": measurements}


def random_cases(count: int, base_seed: int = 7000) -> list[dict]:
    return [random_case(base_seed + index) for index in range(count)]