/**
 * iwlist - a powerful tool with a horrible output
 * Created by kc on 04.04.16.
 */

const _ = require('lodash');
// usually located in /usr/bin/ but as it could be at another location, allow all found in PATH (but we're in trouble
// when the default location, /usr/bin/ is not in the PATH!). GitHub issue #1
const tool     = 'iwlist';
const cmdLine  = tool + ' scan';
const detector = tool + ' --help';


const macRegex  = /([0-9a-zA-Z]{1}[0-9a-zA-Z]{1}[:]{1}){5}[0-9a-zA-Z]{1}[0-9a-zA-Z]{1}/;
const cellRegex = /Cell [0-9]{2,} - Address:/;
const encryptedRegex = /Encryption key:on/g;

/**
 * Parsing the output of iwlist, tool having a lot of different faces :-(
 * @param str output of the tool
 * @param callback
 */
function parseOutput(str, callback) {
  let err   = null;
  let wifis = [];

  try {
    let blocks = str.split(cellRegex);

    blocks.forEach(block => {
      let network = {encrypted: encryptedRegex.test(block)};

      let lines   = block.split('\n');
      if (macRegex.exec(lines[0])) {
        // First line is the mac address (always! (?))
        network.mac = lines[0].trim();

        lines.forEach(line => {
          // SSID
          if (line.indexOf('ESSID:') > 0) {
            network.ssid = _.trim(line.split(':')[1], '"');
            if (_.startsWith(network.ssid, '\\x00')) {
              // The raspi 3 interprets a string terminator as character, it's an empty SSID
              network.ssid = '';
            }
          }

          // Channel, an ugly thing to get it
          else if (_.startsWith(line.trim(), 'Channel:')) {
            network.channel = parseInt(_.trim(line, ' )').split(/:/)[1]);
          }

          // Another ugly thing, the signal which can have different formats, even worse als
          // having different identifiers
          else if (line.indexOf('Signal level') > -1) {
            if (line.indexOf('Quality') > -1) {
              // This is a "Quality=40/70  Signal level=-70 dBm" line
              network.rssi = parseInt(line.substr(line.indexOf('Signal level') + 13), 10);
            } else {
              // This is a "Signal level=60/100" line
              let elements = line.split('=');
              elements.forEach(e => {
                if (e.indexOf('/') > 0) {
                  // that's our part
                  let parts    = e.split('/');
                  let level    = Math.floor(100 * parseInt(parts[0], 10) / parseInt(parts[1], 10));
                  network.rssi = level / 2 - 100;
                }
              })
            }
          }
        });
        wifis.push(network);
      }
    });
  }
  catch (ex) {
    err = ex;
  }

  callback(err, wifis);
}


module.exports = {
  parseOutput: parseOutput,
  cmdLine    : cmdLine,
  detector   : detector,
  tool       : tool
};