// 坐标解析: 接受地图链接(苹果地图 / 高德, 含短链), 抠出经纬度+名称。
// 高德为 GCJ-02; 苹果地图在中国大陆同为 GCJ-02。两者都转 WGS84 再喂给 wloc;
// gcj02ToWgs84 内含 out_of_china 判断, 境外坐标原样返回(无操作)。

export function safeDecode(s) {
  if (!s) return "";
  try {
    return decodeURIComponent(String(s).replace(/\+/g, " "));
  } catch (e) {
    return String(s);
  }
}

// 从一段字符串里提取经纬度+名称。兼容:
//  苹果地图 coordinate=/ll=/sll=纬度,经度  (名称在 name=...)
//  高德 ?p=POIID,纬度,经度,名称,城市  (逗号或 %2C)
//  高德 ?q=纬度,经度,名称           (新版分享链, 逗号或 %2C)
//  纯文本 纬度,经度
export function extractFromString(s) {
  if (!s) return null;
  const str = String(s);
  let m;
  m = str.match(/(?:coordinate|ll|sll)=(-?\d{1,3}\.\d+)(?:,|%2C)(-?\d{1,3}\.\d+)/i);
  if (m) {
    const nm = str.match(/[?&]name=([^&]+)/i);
    return { lat: +m[1], lon: +m[2], name: nm ? safeDecode(nm[1]) : "", src: "apple" };
  }
  m = str.match(
    /[?&]p=[^,&%]*(?:,|%2C)(-?\d{1,3}\.\d+)(?:,|%2C)(-?\d{1,3}\.\d+)(?:(?:,|%2C)((?:(?!,|%2C|&).)+))?/i
  );
  if (m) return { lat: +m[1], lon: +m[2], name: m[3] ? safeDecode(m[3]) : "", src: "amap" };
  m = str.match(
    /[?&]q=(-?\d{1,3}\.\d+)(?:,|%2C)(-?\d{1,3}\.\d+)(?:(?:,|%2C)((?:(?!,|%2C|&).)+))?/i
  );
  if (m) return { lat: +m[1], lon: +m[2], name: m[3] ? safeDecode(m[3]) : "", src: "amap" };
  m = str.match(/(-?\d{1,3}\.\d{4,})\s*(?:,|%2C)\s*(-?\d{1,3}\.\d{4,})/);
  if (m) return { lat: +m[1], lon: +m[2], name: "", src: "text" };
  return null;
}

// 接受原文(可能含中文地名+链接), 抠出 URL, 必要时跟随重定向展开短链, 提取坐标。
export async function parseCoords(raw) {
  const text = String(raw || "").trim();
  if (!text) throw new Error("空输入");

  const urlMatch = text.match(/https?:\/\/[^\s'"<>]+/i);
  let target = urlMatch ? urlMatch[0] : text;

  let hit = extractFromString(target);
  if (hit) return hit;

  if (urlMatch) {
    let cur = target;
    for (let i = 0; i < 5; i++) {
      let resp;
      try {
        resp = await fetch(cur, {
          redirect: "manual",
          headers: {
            "user-agent":
              "Mozilla/5.0 (iPhone; CPU iPhone OS 18_7 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/27.0 Mobile/24A5370h Safari/604.1",
            accept: "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
            "accept-language": "zh-CN,zh-Hans;q=0.9",
          },
        });
      } catch (e) {
        break;
      }
      const loc = resp.headers.get("location");
      if (loc) {
        hit = extractFromString(loc);
        if (hit) return hit;
        cur = new URL(loc, cur).toString();
        hit = extractFromString(cur);
        if (hit) return hit;
        continue;
      }
      hit = extractFromString(resp.url);
      if (hit) return hit;
      try {
        const body = await resp.text();
        hit = extractFromString(body);
        if (hit) return hit;
      } catch (e) {}
      break;
    }
  }
  throw new Error("未能从链接中解析出经纬度");
}

export function round6(n) {
  return Math.round(Number(n) * 1e6) / 1e6;
}

const GCJ_A = 6378245.0;
const GCJ_EE = 0.00669342162296594323;

function gcjOutOfChina(lng, la) {
  return lng < 72.004 || lng > 137.8347 || la < 0.8293 || la > 55.8271;
}

function gcjDeltaLat(x, y) {
  let r = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.sqrt(Math.abs(x));
  r += ((20.0 * Math.sin(6.0 * x * Math.PI) + 20.0 * Math.sin(2.0 * x * Math.PI)) * 2.0) / 3.0;
  r += ((20.0 * Math.sin(y * Math.PI) + 40.0 * Math.sin((y / 3.0) * Math.PI)) * 2.0) / 3.0;
  r += ((160.0 * Math.sin((y / 12.0) * Math.PI) + 320 * Math.sin((y * Math.PI) / 30.0)) * 2.0) / 3.0;
  return r;
}

function gcjDeltaLon(x, y) {
  let r = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.sqrt(Math.abs(x));
  r += ((20.0 * Math.sin(6.0 * x * Math.PI) + 20.0 * Math.sin(2.0 * x * Math.PI)) * 2.0) / 3.0;
  r += ((20.0 * Math.sin(x * Math.PI) + 40.0 * Math.sin((x / 3.0) * Math.PI)) * 2.0) / 3.0;
  r += ((150.0 * Math.sin((x / 12.0) * Math.PI) + 300.0 * Math.sin((x / 30.0) * Math.PI)) * 2.0) / 3.0;
  return r;
}

// WGS84 -> GCJ-02 (正向偏移), 与高德/苹果中国所用偏移一致。
export function wgs84ToGcj02(lat, lon) {
  if (gcjOutOfChina(lon, lat)) return { lat, lon };
  let dLat = gcjDeltaLat(lon - 105.0, lat - 35.0);
  let dLon = gcjDeltaLon(lon - 105.0, lat - 35.0);
  const radLat = (lat / 180.0) * Math.PI;
  let magic = Math.sin(radLat);
  magic = 1 - GCJ_EE * magic * magic;
  const sqrtMagic = Math.sqrt(magic);
  dLat = (dLat * 180.0) / (((GCJ_A * (1 - GCJ_EE)) / (magic * sqrtMagic)) * Math.PI);
  dLon = (dLon * 180.0) / ((GCJ_A / sqrtMagic) * Math.cos(radLat) * Math.PI);
  return { lat: lat + dLat, lon: lon + dLon };
}

// GCJ-02 -> WGS84 (迭代反算, 亚米级)。
// 单程反算在偏移梯度大的地区会残留 1~2m, 这里用不动点迭代收敛到 <0.1m,
// 与高德自身的 WGS84->GCJ 逆运算严格对齐, 消除回看时的残差。
export function gcj02ToWgs84(lat, lon) {
  if (gcjOutOfChina(lon, lat)) return { lat, lon };
  let wgsLat = lat;
  let wgsLon = lon;
  for (let i = 0; i < 6; i++) {
    const g = wgs84ToGcj02(wgsLat, wgsLon);
    const errLat = g.lat - lat;
    const errLon = g.lon - lon;
    if (Math.abs(errLat) < 1e-9 && Math.abs(errLon) < 1e-9) break;
    wgsLat -= errLat;
    wgsLon -= errLon;
  }
  return { lat: wgsLat, lon: wgsLon };
}