const mysql = require('../utils/mysql_db')
const numbers = require('../utils/numbers')

async function Locating() {
    try {
        //首先获取已计算生成的非法电台目录
        let sql = `SELECT id,frequency,confirm FROM fm_t_illegal_radio;`;
        let result = await mysql.query(sql);
        let map_illegal_radio = {};
        for (let i = 0; i < result.length; i++) {
            map_illegal_radio[result[i].frequency] = result[i];
        }
        //获取扫描记录中所有非法电台记录 用以计算
        sql = `
        SELECT frequency, signal_strength, lon, lat, max(upload_time) AS upload_time
        FROM fm_t_scan_record a
        LEFT JOIN fm_t_task_record b ON a.task_record_id = b.id
        WHERE result <> '0' AND result <> '1' AND signal_strength IS NOT NULL AND lon IS NOT NULL AND lat IS NOT NULL
        GROUP BY frequency, device_lgid ;`;
        result = await mysql.query(sql);
        let map_data = {};
        for (let i = 0; i < result.length; i++) {
            if (map_data[result[i].frequency]) {
                map_data[result[i].frequency].push(result[i]);
            } else {
                map_data[result[i].frequency] = [result[i]];
            }
        }
        //依次计算每个非法电台的位置
        for (let freq in map_data) {
            if (map_illegal_radio[freq] && map_illegal_radio[freq].confirm == "已确认") {
                continue; //如果电台信息已经经过确认，则不再计算
            }
            let data = map_data[freq];
            let xy = [];
            let dis = [];
            for (let i = 0; i < data.length; i++) {
                xy.push([data[i].lon, data[i].lat]);
                dis.push(getDistanceByRSS(data[i].signal_strength)); //计算距离
            }
            let location = equationSolving(xy, dis); //求解坐标
            if (!location) {
                continue;
            }
            //保存计算结果到数据库
            if (map_illegal_radio[freq]) {
                sql = `UPDATE fm_t_illegal_radio 
                   SET lon=${location[0][0]},
                       lat=${location[1][0]},
                       time=NOW() 
                   WHERE id=${map_illegal_radio[freq].id};`;
            } else {
                sql = `INSERT INTO fm_t_illegal_radio (frequency,lon,lat,confirm,time,detail) 
                   VALUES(${freq},
                          ${location[0][0]},
                          ${location[1][0]},
                          '待确认',
                          NOW(),
                          '平台计算');`;
            }
            result = await mysql.query(sql);
        }
        return true;
    } catch (err) {
        return false;
    }
}
//通过接收信号强度近似计算电台距离 便于计算返回值单位转为 度
function getDistanceByRSS(rss) {
    let dis = -0.0236 * rss - 2.0394; //距离近似计算公式
    return dis > 0 ? dis : 0;
}
//求解距离方程组 得到电台坐标
//xy为n x 2 的矩阵，表示n个已知点的坐标
//dis为n个已知点到未知点的距离
function equationSolving(xy, dis) {
    try {
        if (dis.length == 1) {
            let theta = Math.random() * Math.PI;
            return [
                [xy[0][0] + dis * Math.cos(theta)],
                [xy[0][1] + dis * Math.sin(theta)]
            ];
        } else if (dis.length == 2) {
            //仅粗略计算，直接返回 中点 ------ 待改进
            return [
                [0.5 * (xy[0][0] + xy[1][0])],
                [0.5 * (xy[0][1] + xy[1][1])]
            ];
        } else {
            let n = dis.length;
            let A = [];
            let b = [];
            const c = dis[n - 1] * dis[n - 1] - xy[n - 1][0] * xy[n - 1][0] - xy[n - 1][1] * xy[n - 1][1];
            for (let i = 0; i < n - 1; i++) {
                A.push([2 * (xy[i][0] - xy[n - 1][0]), 2 * (xy[i][1] - xy[n - 1][1])]);
                b.push([xy[i][0] * xy[i][0] + xy[i][1] * xy[i][1] - dis[i] * dis[i] + c]);
            }
            let AT = [
                numbers.matrix.getCol(A, 0),
                numbers.matrix.getCol(A, 1)
            ];
            let X = numbers.matrix.multiply(
                numbers.matrix.multiply(
                    numbers.matrix.inverse(numbers.matrix.multiply(AT, A)),
                    AT),
                b);
            return X;
        }
    } catch (err) {
        return null;
    }
}

Locating();