feat(NetworkConfig): add QR code scan for WiFi credentials

closes #1192

app/src/main/java/com/geeksville/mesh/ui/components/config/NetworkConfigItemList.kt

@@ -1,10 +1,16 @@
 package com.geeksville.mesh.ui.components.config
 
+import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.text.KeyboardActions
 import androidx.compose.foundation.text.KeyboardOptions
+import androidx.compose.material.Button
 import androidx.compose.material.Divider
+import androidx.compose.material.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
@@ -15,6 +21,7 @@ import androidx.compose.ui.platform.LocalFocusManager
 import androidx.compose.ui.text.input.ImeAction
 import androidx.compose.ui.text.input.KeyboardType
 import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.unit.dp
 import com.geeksville.mesh.ConfigProtos.Config.NetworkConfig
 import com.geeksville.mesh.copy
 import com.geeksville.mesh.ui.components.DropDownPreference
@@ -24,6 +31,8 @@ import com.geeksville.mesh.ui.components.EditTextPreference
 import com.geeksville.mesh.ui.components.PreferenceCategory
 import com.geeksville.mesh.ui.components.PreferenceFooter
 import com.geeksville.mesh.ui.components.SwitchPreference
+import com.journeyapps.barcodescanner.ScanContract
+import com.journeyapps.barcodescanner.ScanOptions
 
 @Composable
 fun NetworkConfigItemList(
@@ -34,6 +43,33 @@ fun NetworkConfigItemList(
     val focusManager = LocalFocusManager.current
     var networkInput by rememberSaveable { mutableStateOf(networkConfig) }
 
+    fun extractWifiCredentials(qrCode: String) = Regex("""WIFI:S:(.*?);.*?P:(.*?);""")
+        .find(qrCode)?.destructured
+        ?.let { (ssid, password) -> ssid to password }
+        ?: (null to null)
+
+    val barcodeLauncher = rememberLauncherForActivityResult(ScanContract()) { result ->
+        if (result.contents != null) {
+            val (ssid, psk) = extractWifiCredentials(result.contents)
+            if (ssid != null && psk != null) {
+                networkInput = networkInput.copy { wifiSsid = ssid }
+                networkInput = networkInput.copy { wifiPsk = psk }
+            } else {
+                // TODO show: "Invalid WiFi Credential QR code format"
+            }
+        }
+    }
+
+    fun zxingScan() {
+        val zxingScan = ScanOptions().apply {
+            setCameraId(0)
+            setPrompt("")
+            setBeepEnabled(false)
+            setDesiredBarcodeFormats(ScanOptions.QR_CODE)
+        }
+        barcodeLauncher.launch(zxingScan)
+    }
+
     LazyColumn(
         modifier = Modifier.fillMaxSize()
     ) {
@@ -71,6 +107,18 @@ fun NetworkConfigItemList(
                 onValueChanged = { networkInput = networkInput.copy { wifiPsk = it } })
         }
 
+        item {
+            Button(
+                onClick = { zxingScan() },
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(vertical = 8.dp)
+                    .height(48.dp),
+            ) {
+                Text(text = "Scan WiFi QR code")
+            }
+        }
+
         item {
             EditTextPreference(title = "NTP server",
                 value = networkInput.ntpServer,