WifiScanner with regex including/excluding and LiveData

WifiScanner.kt

//package si.um.leis.


import android.arch.lifecycle.LiveData
import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import android.net.wifi.WifiManager
import android.os.Handler
import android.support.annotation.MainThread
import android.util.Log
import si.um.leis.ivent.App
import java.util.*
import java.util.regex.Pattern

/*
 * Created on: 16. 05. 2017
 * Author:     Laboratory for Electronic and Information Systems (LEIS)
 *             Bojan Potocnik
 *             bojan.potocnik@um.si
 */

/**
 * LiveData singleton providing WiFi scanning capabilities.
 */
object WifiScanner : LiveData<List<ScanResult>>() {

    private const val TAG = "WifiScanner"

    /** If `true`, (only) count of the found networks will be printed via [Log]. */
    private const val DEBUG_NETWORKS_COUNT = true
    /** If `true`, all found networks (SSID and BSSID) will be printed via [Log]. */
    private const val DEBUG_NETWORKS_SSID = false

    /** Application context used for getting system service and registering broadcast receiver. */
    private val applicationContext: Context by lazy {
        App.applicationContext
    }

    /** [WifiManager] instance. */
    private val mWifiManager: WifiManager by lazy {
        val manager = applicationContext.getSystemService(Context.WIFI_SERVICE) as WifiManager
        // Turn on WiFi if not yet enabled.
        manager.isWifiEnabled = true
        manager
    }

    /** Runnable (used by [mHandler]) for repeated scanning. */
    private val mRunnable by lazy {
        Runnable {
            if (mWifiManager.startScan()) {
                mScanStartTime = System.currentTimeMillis()
            }
        }
    }
    /** Handler executing [mRunnable] for repeated scanning. */
    private val mHandler: Handler by lazy {
        Handler()
    }
    /** Broadcast receiver for [Context.registerReceiver]. */
    private val mBroadcastReceiver: BroadcastReceiver by lazy {
        object : BroadcastReceiver() {
            @MainThread
            override fun onReceive(context: Context?, intent: Intent?) = onScanResults(context, intent)
        }
    }

    /** Discovered WiFi networks. */
    private val mNetworks: LinkedList<ScanResult> by lazy { LinkedList<ScanResult>() }

    /**
     * Regex masks for including SSIDs.
     *
     * See [configureScan].
     */
    private var mSsidRegexIncludeFilters: Array<Pattern>? = null
    /**
     * Regex masks for excluding SSIDs.
     *
     * See [configureScan].
     */
    private var mSsidRegexExcludeFilters: Array<Pattern>? = null
    /**
     * Scan repeat interval in milliseconds.
     *
     * See [configureScan].
     */
    private var mRepeatInterval = 0
    /** Timestamp when last single WiFi scan was initiated. */
    private var mScanStartTime: Long = 0
    /** See [getLastScanDuration]. */
    private var mLastScanDuration: Int = -1
    /**
     *  If `true`, value will be updated with empty or the same list even if no or no new devices
     *  (after filtering) are found.
     *
     *  See [configureScan].
     */
    private var mUpdateIfNothingNew: Boolean = true


    /**
     * Configure WiFi networks scanning parameters. If scanning is already running, changes will
     * be applied when current scan finished and it is restarted with new parameters. New filters
     * will already be used on this scan result.
     *
     * @param ssidIncludeFilter Array of regex masks. If not `null`, SSID's will be compared to
     *                          every regex string until matching one is found. If SSID does not match
     *                          any of the provided SSID strings, it is ignored and not shown.
     *                          See [Pattern (Java Class)](https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html).
     * @param ssidExcludeFilter The same as ssidIncludeFilter except if SSID matches this filter it
     *                          will not be shown. This is done after filtering by ssidIncludeFilter.
     * @param repeatInterval Scan repeat interval in milliseconds. If positive value, scan will be
     *                       restarted every such amount of milliseconds (or later, if scan itself
     *                       takes more time). If `0` negative, new scan will be initiated
     *                       immediately after results of the previous request are received.
     *                       If less than `0` or `null`, scan will be started immediately and only
     *                       once.
     * @param updateIfNothingNew If `true`, value will be updated with empty or the same list even
     *                           if no or no new devices (after filtering) are found.
     */
    fun configureScan(ssidIncludeFilter: Array<String>? = null,
                      ssidExcludeFilter: Array<String>? = null,
                      repeatInterval: Int = 0,
                      updateIfNothingNew: Boolean = true) {
        mSsidRegexIncludeFilters =
                if (ssidIncludeFilter != null)
                    Array(ssidIncludeFilter.size) { index ->
                        Pattern.compile(ssidIncludeFilter[index])
                    }
                else null
        mSsidRegexExcludeFilters =
                if (ssidExcludeFilter != null)
                    Array(ssidExcludeFilter.size) { index ->
                        Pattern.compile(ssidExcludeFilter[index])
                    }
                else null
        mRepeatInterval = repeatInterval
        mUpdateIfNothingNew = updateIfNothingNew
        mNetworks.clear()
        // This is only configuration, do not start scanning here.
        if (hasActiveObservers()) {
            // Try to apply settings as soon as possible by force restarting the scan.
            executeScan()
        }
    }

    /**
     * @return Time (in milliseconds) taken to perform one (last) scan of WiFi networks or -1 if no
     *         scan has been finished yet.
     */
    fun getLastScanDuration(): Int = mLastScanDuration


    /**
     * Execute or schedule delayed execution of the next scan.
     */
    private fun executeScan(delay: Long = 0) {
        if (delay > 0) {
            mHandler.postDelayed(mRunnable, delay)
        } else {
            // Start scan directly.
            mRunnable.run()
        }
    }

    /**
     * Called when an [WifiManager.SCAN_RESULTS_AVAILABLE_ACTION] Intent broadcast is received.
     */
    @Suppress("UNUSED_PARAMETER")
    @MainThread
    private fun onScanResults(context: Context?, intent: Intent?) {
        // Get all found networks.
        val wifiList = mWifiManager.scanResults
        // Measure time taken for the scan to finish.
        mLastScanDuration = (System.currentTimeMillis() - mScanStartTime).toInt()

        if (DEBUG_NETWORKS_COUNT) {
            Log.d(TAG, "Scan finished in $mLastScanDuration ms with " + wifiList.size + " results.")
        }

        var newNetwork = false
        var updatedNetwork = false
        // Add found networks to the internal list of matching networks.
        for (wifi in wifiList) {
            var matches = false
            // Filter networks, if filter is provided.
            if (mSsidRegexIncludeFilters != null) {
                mSsidRegexIncludeFilters!!.forEach {
                    if (it.matcher(wifi.SSID).matches()) {
                        matches = true
                        return@forEach
                    }
                }
            } else {
                matches = true
            }
            // If network passes the include filter, check also for exclude filter.
            if (matches && (mSsidRegexExcludeFilters != null)) {
                mSsidRegexExcludeFilters!!.forEach {
                    if (it.matcher(wifi.SSID).matches()) {
                        matches = false
                        return@forEach
                    }
                }
            }
            // Only add matching network or update if already in the list.
            if (matches) {
                var updated = false
                mNetworks.forEach({
                    if (it.isTheSameAs(wifi)) {
                        if (DEBUG_NETWORKS_SSID) {
                            Log.d(TAG, "Updating: " + wifi.SSID + "/" + wifi.BSSID)
                        }
                        it.sr = wifi
                        it.updated = true
                        updated = true
                        updatedNetwork = true
                        return@forEach
                    }
                })
                if (!updated) {
                    if (DEBUG_NETWORKS_SSID) {
                        Log.d(TAG, "Adding new: " + wifi.SSID + "/" + wifi.BSSID)
                    }
                    mNetworks.add(ScanResult(wifi))
                    newNetwork = true
                }
            } else {
                if (DEBUG_NETWORKS_SSID) {
                    Log.v(TAG, "Ignoring: " + wifi.SSID + "/" + wifi.BSSID)
                }
            }
        }

        // Schedule new scan.
        // Scan start time is always lower than current time, therefore the delay is always <= 0 if the mRepeatInterval is <= 0.
        executeScan(mScanStartTime + mRepeatInterval - System.currentTimeMillis())

        // Notify observers.
        if (newNetwork || updatedNetwork || mUpdateIfNothingNew) {
            value = mNetworks
        }
    }


    //----------------------------------------------------------------------------------------------
    //region LiveData

    /**
     * Called when the number of active observers change from 0 to 1 - LiveData is being used.
     */
    override fun onActive() {
        // Register receiver which will receive scan result, but do not yet start scanning.
        applicationContext.registerReceiver(mBroadcastReceiver, IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION))
        // Start (repeatedly) scanning for WiFi networks.
        executeScan()
    }

    /**
     * Called when the number of active observers change from 1 to 0.
     */
    override fun onInactive() {
        // Stop scanning for WiFi networks.
        mHandler.removeCallbacks(mRunnable)
        applicationContext.unregisterReceiver(mBroadcastReceiver)
    }

    //endregion LiveData
    //----------------------------------------------------------------------------------------------

}