Introduce realtime log viewer

This contains a share button and a save button, the former using a
custom content provider.

Co-authored-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

18 files changed, 444 insertions, 116 deletions

diff --git a/ui/src/main/AndroidManifest.xml b/ui/src/main/AndroidManifest.xml
index 11c1102b..74bc7a20 100644
--- a/ui/src/main/AndroidManifest.xml
+++ b/ui/src/main/AndroidManifest.xml
@@ -31,6 +31,7 @@
         android:banner="@mipmap/banner">
 
         <activity android:name=".activity.TunnelToggleActivity" android:theme="@style/NoBackgroundTheme"/>
+
         <activity android:name=".activity.MainActivity">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
@@ -58,6 +59,19 @@
             android:screenOrientation="fullSensor"
             tools:replace="screenOrientation" />
 
+        <activity android:name=".activity.LogViewerActivity"
+            android:label="@string/log_viewer_title">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+            </intent-filter>
+        </activity>
+
+        <provider
+            android:name=".activity.LogViewerActivity$ExportedLogContentProvider"
+            android:authorities="${applicationId}.exported-log"
+            android:exported="false"
+            android:grantUriPermissions="true" />
+
         <receiver android:name=".BootShutdownReceiver">
             <intent-filter>
                 <action android:name="android.intent.action.ACTION_SHUTDOWN" />
diff --git a/ui/src/main/java/com/wireguard/android/activity/LogViewerActivity.kt b/ui/src/main/java/com/wireguard/android/activity/LogViewerActivity.kt
new file mode 100644
index 00000000..c94bba8d
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/activity/LogViewerActivity.kt
@@ -0,0 +1,324 @@
+/*
+ * Copyright © 2020 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.activity
+
+import android.content.ClipDescription.compareMimeTypes
+import android.content.ContentProvider
+import android.content.ContentValues
+import android.content.Intent
+import android.database.Cursor
+import android.database.MatrixCursor
+import android.graphics.Typeface.BOLD
+import android.net.Uri
+import android.os.Bundle
+import android.os.ParcelFileDescriptor
+import android.text.Spannable
+import android.text.SpannableString
+import android.text.style.ForegroundColorSpan
+import android.text.style.StyleSpan
+import android.view.LayoutInflater
+import android.view.Menu
+import android.view.MenuItem
+import android.view.View
+import android.view.ViewGroup
+import androidx.appcompat.app.AppCompatActivity
+import androidx.core.app.ShareCompat
+import androidx.recyclerview.widget.DividerItemDecoration
+import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.RecyclerView
+import com.google.android.material.snackbar.Snackbar
+import com.google.android.material.textview.MaterialTextView
+import com.wireguard.android.BuildConfig
+import com.wireguard.android.R
+import com.wireguard.android.databinding.LogViewerActivityBinding
+import com.wireguard.android.util.DownloadsFileSaver
+import com.wireguard.android.widget.EdgeToEdge.setUpFAB
+import com.wireguard.android.widget.EdgeToEdge.setUpRoot
+import com.wireguard.android.widget.EdgeToEdge.setUpScrollingContent
+import com.wireguard.crypto.KeyPair
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.cancel
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import java.io.BufferedReader
+import java.io.FileOutputStream
+import java.io.IOException
+import java.io.InputStreamReader
+import java.nio.charset.StandardCharsets
+import java.text.DateFormat
+import java.text.ParseException
+import java.text.SimpleDateFormat
+import java.util.Date
+import java.util.Locale
+import java.util.concurrent.ConcurrentHashMap
+import java.util.regex.Matcher
+import java.util.regex.Pattern
+
+class LogViewerActivity : AppCompatActivity() {
+
+    private lateinit var binding: LogViewerActivityBinding
+    private lateinit var logAdapter: LogEntryAdapter
+    private var logLines = arrayListOf<LogLine>()
+    private var rawLogLines = StringBuffer()
+    private var recyclerView: RecyclerView? = null
+    private var saveButton: MenuItem? = null
+    private val coroutineScope = CoroutineScope(Dispatchers.Default)
+    private val year by lazy {
+        val yearFormatter: DateFormat = SimpleDateFormat("yyyy", Locale.US)
+        yearFormatter.format(Date())
+    }
+
+    @Suppress("Deprecation")
+    private val defaultColor by lazy { resources.getColor(R.color.primary_text_color) }
+
+    @Suppress("Deprecation")
+    private val debugColor by lazy { resources.getColor(R.color.debug_tag_color) }
+
+    @Suppress("Deprecation")
+    private val errorColor by lazy { resources.getColor(R.color.error_tag_color) }
+
+    @Suppress("Deprecation")
+    private val infoColor by lazy { resources.getColor(R.color.info_tag_color) }
+
+    @Suppress("Deprecation")
+    private val warningColor by lazy { resources.getColor(R.color.warning_tag_color) }
+
+    private var lastUri: Uri? = null
+
+    private fun revokeLastUri() {
+        lastUri?.let {
+            LOGS.remove(it.pathSegments.lastOrNull())
+            revokeUriPermission(it, Intent.FLAG_GRANT_READ_URI_PERMISSION)
+            lastUri = null
+        }
+    }
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        binding = LogViewerActivityBinding.inflate(layoutInflater)
+        setContentView(binding.root)
+        supportActionBar?.setDisplayHomeAsUpEnabled(true)
+        setUpFAB(binding.shareFab)
+        setUpRoot(binding.root)
+        setUpScrollingContent(binding.recyclerView, binding.shareFab)
+        logAdapter = LogEntryAdapter()
+        binding.recyclerView.apply {
+            recyclerView = this
+            layoutManager = LinearLayoutManager(context)
+            adapter = logAdapter
+            addItemDecoration(DividerItemDecoration(context, LinearLayoutManager.VERTICAL))
+        }
+
+        coroutineScope.launch { streamingLog() }
+
+        binding.shareFab.setOnClickListener {
+            revokeLastUri()
+            val key = KeyPair().privateKey.toHex()
+            LOGS[key] = rawLogLines.toString().toByteArray(Charsets.UTF_8)
+            lastUri = Uri.parse("content://${BuildConfig.APPLICATION_ID}.exported-log/$key")
+            val shareIntent = ShareCompat.IntentBuilder.from(this)
+                    .setType("text/plain")
+                    .setSubject(getString(R.string.log_export_subject))
+                    .setStream(lastUri)
+                    .setChooserTitle(R.string.log_export_title)
+                    .createChooserIntent()
+                    .addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
+            grantUriPermission("android", lastUri, Intent.FLAG_GRANT_READ_URI_PERMISSION)
+            startActivityForResult(shareIntent, SHARE_ACTIVITY_REQUEST)
+        }
+    }
+
+    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
+        if (requestCode == SHARE_ACTIVITY_REQUEST) {
+            revokeLastUri()
+        }
+        super.onActivityResult(requestCode, resultCode, data)
+    }
+
+    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
+        menuInflater.inflate(R.menu.log_viewer, menu)
+        saveButton = menu?.findItem(R.id.save_log)
+        return true
+    }
+
+    override fun onOptionsItemSelected(item: MenuItem): Boolean {
+        return when (item.itemId) {
+            android.R.id.home -> {
+                finish()
+                true
+            }
+            R.id.save_log -> {
+                coroutineScope.launch { saveLog() }
+                true
+            }
+            else -> super.onOptionsItemSelected(item)
+        }
+    }
+
+    override fun onDestroy() {
+        super.onDestroy()
+        coroutineScope.cancel()
+    }
+
+    private suspend fun saveLog() {
+        val context = this
+        withContext(Dispatchers.Main) {
+            saveButton?.isEnabled = false
+            withContext(Dispatchers.IO) {
+                val outputFile = DownloadsFileSaver.save(context, "wireguard-log.txt", "text/plain", true)
+                outputFile.outputStream.use {
+                    it.write(rawLogLines.toString().toByteArray(Charsets.UTF_8))
+                }
+                withContext(Dispatchers.Main) {
+                    Snackbar.make(findViewById(android.R.id.content),
+                            getString(R.string.log_export_success, outputFile.fileName),
+                            Snackbar.LENGTH_SHORT)
+                            .setAnchorView(binding.shareFab)
+                            .show()
+                    saveButton?.isEnabled = true
+                }
+            }
+        }
+    }
+
+    private suspend fun streamingLog() = withContext(Dispatchers.IO) {
+        val builder = ProcessBuilder().command("logcat", "-b", "all", "-v", "threadtime", "*:V")
+        builder.environment()["LC_ALL"] = "C"
+        val process = try {
+            builder.start()
+        } catch (e: IOException) {
+            e.printStackTrace()
+            return@withContext
+        }
+        val stdout = BufferedReader(InputStreamReader(process!!.inputStream, StandardCharsets.UTF_8))
+        while (true) {
+            val line = stdout.readLine() ?: break
+            rawLogLines.append(line)
+            rawLogLines.append('\n')
+            val logLine = parseLine(line)
+            if (logLine != null) {
+                withContext(Dispatchers.Main) {
+                    recyclerView?.let {
+                        val shouldScroll = it.canScrollVertically(1)
+                        logLines.add(logLine)
+                        logAdapter.notifyDataSetChanged()
+                        if (!shouldScroll)
+                            it.scrollToPosition(logLines.size - 1)
+                    }
+                }
+            }
+        }
+    }
+
+    private fun parseTime(timeStr: String): Date? {
+        val formatter: DateFormat = SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS", Locale.US)
+        return try {
+            formatter.parse("$year-$timeStr")
+        } catch (e: ParseException) {
+            null
+        }
+    }
+
+    private fun parseLine(line: String): LogLine? {
+        val m: Matcher = THREADTIME_LINE.matcher(line)
+        return if (m.matches()) {
+            LogLine(m.group(2)!!.toInt(), m.group(3)!!.toInt(), parseTime(m.group(1)!!), m.group(4)!!, m.group(5)!!, m.group(6)!!)
+        } else {
+            null
+        }
+    }
+
+    private data class LogLine(val pid: Int, val tid: Int, val time: Date?, val level: String, val tag: String, val msg: String)
+
+    companion object {
+        /**
+         * Match a single line of `logcat -v threadtime`, such as:
+         *
+         * <pre>05-26 11:02:36.886 5689 5689 D AndroidRuntime: CheckJNI is OFF.</pre>
+         */
+        private val THREADTIME_LINE: Pattern = Pattern.compile("^(\\d{2}-\\d{2} \\d{2}:\\d{2}:\\d{2}.\\d{3})(?:\\s+[0-9A-Za-z]+)?\\s+(\\d+)\\s+(\\d+)\\s+([A-Z])\\s+(.+?)\\s*: (.*)$")
+        private val LOGS: MutableMap<String, ByteArray> = ConcurrentHashMap()
+        private var SHARE_ACTIVITY_REQUEST = 49133
+    }
+
+    private inner class LogEntryAdapter : RecyclerView.Adapter<LogEntryAdapter.ViewHolder>() {
+
+        private inner class ViewHolder(val layout: View, var isSingleLine: Boolean = true) : RecyclerView.ViewHolder(layout)
+
+        private fun levelToColor(level: String): Int {
+            return when (level) {
+                "D" -> debugColor
+                "E" -> errorColor
+                "I" -> infoColor
+                "W" -> warningColor
+                else -> defaultColor
+            }
+        }
+
+        override fun getItemCount() = logLines.size
+
+        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
+            val view = LayoutInflater.from(parent.context)
+                    .inflate(R.layout.log_viewer_entry, parent, false)
+            return ViewHolder(view)
+        }
+
+        override fun onBindViewHolder(holder: ViewHolder, position: Int) {
+            val line = logLines[position]
+            val spannable = if (position > 0 && logLines[position - 1].tag == line.tag)
+                SpannableString(line.msg)
+            else
+                SpannableString("${line.tag}: ${line.msg}").apply {
+                    setSpan(StyleSpan(BOLD), 0, "${line.tag}:".length, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE)
+                    setSpan(ForegroundColorSpan(levelToColor(line.level)),
+                            0, "${line.tag}:".length, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE)
+                }
+            holder.layout.apply {
+                findViewById<MaterialTextView>(R.id.log_date).text = line.time.toString()
+                findViewById<MaterialTextView>(R.id.log_msg).apply {
+                    setSingleLine()
+                    text = spannable
+                    setOnClickListener {
+                        isSingleLine = !holder.isSingleLine
+                        holder.isSingleLine = !holder.isSingleLine
+                    }
+                }
+            }
+        }
+    }
+
+    class ExportedLogContentProvider : ContentProvider() {
+        private fun logForUri(uri: Uri): ByteArray? = LOGS[uri.pathSegments.lastOrNull()]
+
+        override fun insert(uri: Uri, values: ContentValues?): Uri? = null
+
+        override fun query(uri: Uri, projection: Array<out String>?, selection: String?, selectionArgs: Array<out String>?, sortOrder: String?): Cursor? =
+                logForUri(uri)?.let {
+                    val m = MatrixCursor(arrayOf(android.provider.OpenableColumns.DISPLAY_NAME, android.provider.OpenableColumns.SIZE), 1)
+                    m.addRow(arrayOf("wireguard-log.txt", it.size.toLong()))
+                    m
+                }
+
+        override fun onCreate(): Boolean = true
+
+        override fun update(uri: Uri, values: ContentValues?, selection: String?, selectionArgs: Array<out String>?): Int = 0
+
+        override fun delete(uri: Uri, selection: String?, selectionArgs: Array<out String>?): Int = 0
+
+        override fun getType(uri: Uri): String? = logForUri(uri)?.let { "text/plain" }
+
+        override fun getStreamTypes(uri: Uri, mimeTypeFilter: String): Array<String>? = getType(uri)?.let { if (compareMimeTypes(it, mimeTypeFilter)) arrayOf(it) else null }
+
+        override fun openFile(uri: Uri, mode: String): ParcelFileDescriptor? {
+            if (mode != "r") return null
+            val log = logForUri(uri) ?: return null
+            return openPipeHelper(uri, "text/plain", null, log) { output, _, _, _, l ->
+                FileOutputStream(output.fileDescriptor).write(l!!)
+            }
+        }
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/activity/SettingsActivity.kt b/ui/src/main/java/com/wireguard/android/activity/SettingsActivity.kt
index 8bd27d00..103b6b44 100644
--- a/ui/src/main/java/com/wireguard/android/activity/SettingsActivity.kt
+++ b/ui/src/main/java/com/wireguard/android/activity/SettingsActivity.kt
@@ -4,6 +4,7 @@
  */
 package com.wireguard.android.activity
 
+import android.content.Intent
 import android.content.pm.PackageManager
 import android.os.Build
 import android.os.Bundle
@@ -100,6 +101,10 @@ class SettingsActivity : ThemeChangeAwareActivity() {
                     wgQuickOnlyPrefs.forEach { it.parent?.removePreference(it) }
                 }
             }
+            preferenceManager.findPreference<Preference>("log_viewer")?.setOnPreferenceClickListener {
+                startActivity(Intent(requireContext(), LogViewerActivity::class.java))
+                true
+            }
             val moduleInstaller = preferenceManager.findPreference<Preference>("module_downloader")
             val kernelModuleDisabler = preferenceManager.findPreference<Preference>("kernel_module_disabler")
             moduleInstaller?.isVisible = false
diff --git a/ui/src/main/java/com/wireguard/android/preference/LogExporterPreference.kt b/ui/src/main/java/com/wireguard/android/preference/LogExporterPreference.kt
deleted file mode 100644
index ede4b661..00000000
--- a/ui/src/main/java/com/wireguard/android/preference/LogExporterPreference.kt
+++ /dev/null
@@ -1,101 +0,0 @@
-/*
- * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
- * SPDX-License-Identifier: Apache-2.0
- */
-package com.wireguard.android.preference
-
-import android.Manifest
-import android.content.Context
-import android.content.pm.PackageManager
-import android.os.Build
-import android.util.AttributeSet
-import android.util.Log
-import androidx.preference.Preference
-import com.google.android.material.snackbar.Snackbar
-import com.wireguard.android.Application
-import com.wireguard.android.R
-import com.wireguard.android.util.DownloadsFileSaver
-import com.wireguard.android.util.ErrorMessages
-import com.wireguard.android.util.FragmentUtils
-import java.io.BufferedReader
-import java.io.InputStreamReader
-
-/**
- * Preference implementing a button that asynchronously exports logs.
- */
-class LogExporterPreference(context: Context, attrs: AttributeSet?) : Preference(context, attrs) {
-    private var exportedFilePath: String? = null
-    private fun exportLog() {
-        Application.getAsyncWorker().supplyAsync {
-            val outputFile = DownloadsFileSaver.save(context, "wireguard-log.txt", "text/plain", true)
-            try {
-                val process = Runtime.getRuntime().exec(arrayOf(
-                        "logcat", "-b", "all", "-d", "-v", "threadtime", "*:V"))
-                BufferedReader(InputStreamReader(process.inputStream)).use { stdout ->
-                    BufferedReader(InputStreamReader(process.errorStream)).use { stderr ->
-                        while (true) {
-                            val line = stdout.readLine() ?: break
-                            outputFile.outputStream.write(line.toByteArray())
-                            outputFile.outputStream.write('\n'.toInt())
-                        }
-                        outputFile.outputStream.close()
-                        if (process.waitFor() != 0) {
-                            val errors = StringBuilder()
-                            errors.append(R.string.logcat_error)
-                            while (true) {
-                                val line = stderr.readLine() ?: break
-                                errors.append(line)
-                            }
-                            throw Exception(errors.toString())
-                        }
-                    }
-                }
-            } catch (e: Exception) {
-                outputFile.delete()
-                throw e
-            }
-            outputFile.fileName
-        }.whenComplete(this::exportLogComplete)
-    }
-
-    private fun exportLogComplete(filePath: String, throwable: Throwable?) {
-        if (throwable != null) {
-            val error = ErrorMessages.get(throwable)
-            val message = context.getString(R.string.log_export_error, error)
-            Log.e(TAG, message, throwable)
-            Snackbar.make(
-                    FragmentUtils.getPrefActivity(this).findViewById(android.R.id.content),
-                    message, Snackbar.LENGTH_LONG).show()
-            isEnabled = true
-        } else {
-            exportedFilePath = filePath
-            notifyChanged()
-        }
-    }
-
-    override fun getSummary() = if (exportedFilePath == null)
-        context.getString(R.string.log_export_summary)
-    else
-        context.getString(R.string.log_export_success, exportedFilePath)
-
-    override fun getTitle() = context.getString(R.string.log_export_title)
-
-    override fun onClick() {
-        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) {
-            FragmentUtils.getPrefActivity(this)
-                    .ensurePermissions(arrayOf(Manifest.permission.WRITE_EXTERNAL_STORAGE)) { _, grantResults ->
-                        if (grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
-                            isEnabled = false
-                            exportLog()
-                        }
-                    }
-        } else {
-            isEnabled = false
-            exportLog()
-        }
-    }
-
-    companion object {
-        private val TAG = "WireGuard/" + LogExporterPreference::class.java.simpleName
-    }
-}
diff --git a/ui/src/main/res/drawable/ic_action_share_white.xml b/ui/src/main/res/drawable/ic_action_share_white.xml
new file mode 100644
index 00000000..4ada554b
--- /dev/null
+++ b/ui/src/main/res/drawable/ic_action_share_white.xml
@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+  <path
+      android:fillColor="#FFFFFFFF"
+      android:pathData="M18,16.08c-0.76,0 -1.44,0.3 -1.96,0.77L8.91,12.7c0.05,-0.23 0.09,-0.46 0.09,-0.7s-0.04,-0.47 -0.09,-0.7l7.05,-4.11c0.54,0.5 1.25,0.81 2.04,0.81 1.66,0 3,-1.34 3,-3s-1.34,-3 -3,-3 -3,1.34 -3,3c0,0.24 0.04,0.47 0.09,0.7L8.04,9.81C7.5,9.31 6.79,9 6,9c-1.66,0 -3,1.34 -3,3s1.34,3 3,3c0.79,0 1.5,-0.31 2.04,-0.81l7.12,4.16c-0.05,0.21 -0.08,0.43 -0.08,0.65 0,1.61 1.31,2.92 2.92,2.92 1.61,0 2.92,-1.31 2.92,-2.92s-1.31,-2.92 -2.92,-2.92z"/>
+</vector>
diff --git a/ui/src/main/res/layout/log_viewer_activity.xml b/ui/src/main/res/layout/log_viewer_activity.xml
new file mode 100644
index 00000000..7a08bc88
--- /dev/null
+++ b/ui/src/main/res/layout/log_viewer_activity.xml
@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright © 2020 WireGuard LLC. All Rights Reserved.
+  ~ SPDX-License-Identifier: Apache-2.0
+  -->
+
+<androidx.coordinatorlayout.widget.CoordinatorLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/recycler_view"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        tools:listitem="@layout/log_viewer_entry"
+        tools:itemCount="20" />
+
+    <com.google.android.material.floatingactionbutton.ExtendedFloatingActionButton
+        style="@style/Widget.MaterialComponents.ExtendedFloatingActionButton.Icon"
+        android:id="@+id/share_fab"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="bottom|end"
+        android:layout_margin="@dimen/fab_margin"
+        app:icon="@drawable/ic_action_share_white" />
+
+</androidx.coordinatorlayout.widget.CoordinatorLayout>
diff --git a/ui/src/main/res/layout/log_viewer_entry.xml b/ui/src/main/res/layout/log_viewer_entry.xml
new file mode 100644
index 00000000..37f8941d
--- /dev/null
+++ b/ui/src/main/res/layout/log_viewer_entry.xml
@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright © 2020 WireGuard LLC. All Rights Reserved.
+  ~ SPDX-License-Identifier: Apache-2.0
+  -->
+
+<androidx.constraintlayout.widget.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:padding="6dp">
+    <com.google.android.material.textview.MaterialTextView
+        style="@style/TextAppearance.MaterialComponents.Caption"
+        android:id="@+id/log_date"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:textColor="?android:attr/textColorPrimary"
+        android:textSize="10sp"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        tools:text="Fri Mar 13 10:17:37 GMT+05:30 2020" />
+
+    <com.google.android.material.textview.MaterialTextView
+        style="@style/TextAppearance.MaterialComponents.Caption"
+        android:id="@+id/log_msg"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:textColor="?android:attr/textColorPrimary"
+        app:layout_constraintTop_toBottomOf="@id/log_date"
+        tools:text="FATAL EXCEPTION: Thread-2" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/ui/src/main/res/menu/log_viewer.xml b/ui/src/main/res/menu/log_viewer.xml
new file mode 100644
index 00000000..3a9da698
--- /dev/null
+++ b/ui/src/main/res/menu/log_viewer.xml
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+    <item
+        android:id="@+id/save_log"
+        android:icon="@drawable/ic_action_save"
+        android:title="@string/log_export_title"
+        app:showAsAction="ifRoom"/>
+</menu>
diff --git a/ui/src/main/res/values-hi/strings.xml b/ui/src/main/res/values-hi/strings.xml
index c79341d7..bda0cbb2 100644
--- a/ui/src/main/res/values-hi/strings.xml
+++ b/ui/src/main/res/values-hi/strings.xml
@@ -88,9 +88,7 @@
     <string name="key_length_explanation_binary">: वायरगार्ड कीज 32 बाइट होनी चाहिए</string>
     <string name="key_length_explanation_hex">: वायरगार्ड हेक्स कीज़ 64 अक्षरों की होनी चाहिए (32 बाइट्स)</string>
     <string name="listen_port">पोर्ट सूने</string>
-    <string name="log_export_error">लॉग निर्यात करने में असमर्थ: %s</string>
     <string name="log_export_success">“%s” में सहेजा गया</string>
-    <string name="log_export_summary">लॉग फ़ाइल को डाउनलोड फ़ोल्डर में सहेजा जाएगा</string>
     <string name="log_export_title">लॉग फ़ाइल निर्यात करें</string>
     <string name="logcat_error">लॉगकैट चलाने में असमर्थ: </string>
     <string name="module_version_error">कर्नेल मॉड्यूल संस्करण निर्धारित करने में असमर्थ</string>
diff --git a/ui/src/main/res/values-id/strings.xml b/ui/src/main/res/values-id/strings.xml
index 7c6c6a0b..3f0af404 100644
--- a/ui/src/main/res/values-id/strings.xml
+++ b/ui/src/main/res/values-id/strings.xml
@@ -88,9 +88,7 @@
     <string name="key_length_explanation_binary">: Kunci WireGuard harus terdiri dari 32 bit</string>
     <string name="key_length_explanation_hex">: Kunci hex WireGuard Harus terdiri dari 64 karakter (32 bit)</string>
     <string name="listen_port">Isi port</string>
-    <string name="log_export_error">Log %s tidak bisa diekspor</string>
     <string name="log_export_success">Simpan ke “%s”</string>
-    <string name="log_export_summary">File log akan disimpan di folder download</string>
     <string name="log_export_title">Ekspor file log</string>
     <string name="logcat_error">Tidak bisa menjalankan logcat: </string>
     <string name="module_version_error">Tidak dapat menentukan versi modul kernel</string>
diff --git a/ui/src/main/res/values-it/strings.xml b/ui/src/main/res/values-it/strings.xml
index 48f36a2b..2ab211e9 100644
--- a/ui/src/main/res/values-it/strings.xml
+++ b/ui/src/main/res/values-it/strings.xml
@@ -88,9 +88,7 @@
     <string name="key_length_explanation_binary">: le chiavi di WireGuard devono essere di 32 byte</string>
     <string name="key_length_explanation_hex">: le chiavi hex di WireGuard devono essere di 64 caratteri (32 byte)</string>
     <string name="listen_port">Porta in ascolto</string>
-    <string name="log_export_error">Impossibile esportare il registro: %s</string>
     <string name="log_export_success">Salvato in “%s”</string>
-    <string name="log_export_summary">Il file del registro verrà salvato nella cartella di download</string>
     <string name="log_export_title">Esporta file registro</string>
     <string name="logcat_error">Impossibile eseguire logcat: </string>
     <string name="module_version_error">Impossibile determinare la versione modulo del kernel</string>
diff --git a/ui/src/main/res/values-ja/strings.xml b/ui/src/main/res/values-ja/strings.xml
index c753a5d5..5d342d2d 100644
--- a/ui/src/main/res/values-ja/strings.xml
+++ b/ui/src/main/res/values-ja/strings.xml
@@ -84,9 +84,7 @@
     <string name="key_length_explanation_binary">: WireGuard 鍵は32バイトでなければなりません</string>
     <string name="key_length_explanation_hex">: WireGuard hex 鍵は64文字（32バイト）でなければなりません</string>
     <string name="listen_port">Listen ポート</string>
-    <string name="log_export_error">ログをエクスポートできません: %s</string>
     <string name="log_export_success">“%s” に保存しました</string>
-    <string name="log_export_summary">ログはダウンロードフォルダに保存されます</string>
     <string name="log_export_title">ログのエクスポート</string>
     <string name="logcat_error">logcat を実行できません: </string>
     <string name="module_version_error">カーネルモジュールバージョンを特定できません</string>
diff --git a/ui/src/main/res/values-night/colors.xml b/ui/src/main/res/values-night/colors.xml
index 314142d9..e1015da8 100644
--- a/ui/src/main/res/values-night/colors.xml
+++ b/ui/src/main/res/values-night/colors.xml
@@ -14,4 +14,10 @@
     <color name="list_multiselect_background">#1aeeeeee</color>
     <color name="status_bar_color">#21242424</color>
     <color name="navigation_bar_color">#aa242424</color>
+
+    <!-- Log viewer tag colors -->
+    <color name="debug_tag_color">#aaaaaa</color>
+    <color name="error_tag_color">#ff0000</color>
+    <color name="info_tag_color">#00ff00</color>
+    <color name="warning_tag_color">#ffff00</color>
 </resources>
diff --git a/ui/src/main/res/values-ru/strings.xml b/ui/src/main/res/values-ru/strings.xml
index 557ce196..519ec24e 100644
--- a/ui/src/main/res/values-ru/strings.xml
+++ b/ui/src/main/res/values-ru/strings.xml
@@ -93,9 +93,7 @@
     <string name="key_length_explanation_binary">: Ключи WireGuard должны быть 32 байта</string>
     <string name="key_length_explanation_hex">: HEX ключи WireGuard должны содержать 64 символа (32 байта)</string>
     <string name="listen_port">Порт</string>
-    <string name="log_export_error">Не удалось экспортировать логи: %s</string>
     <string name="log_export_success">Сохранено в “%s”</string>
-    <string name="log_export_summary">Файл логов будет сохранен в папке загрузок</string>
     <string name="log_export_title">Экспорт логов в файл</string>
     <string name="logcat_error">Не удалось запустить logcat: </string>
     <string name="module_version_error">Не удалось определить версию модуля ядра</string>
diff --git a/ui/src/main/res/values-zh-rCN/strings.xml b/ui/src/main/res/values-zh-rCN/strings.xml
index 613abf46..4e3730f1 100644
--- a/ui/src/main/res/values-zh-rCN/strings.xml
+++ b/ui/src/main/res/values-zh-rCN/strings.xml
@@ -82,9 +82,7 @@
     <string name="key_length_explanation_binary">：WireGuard 密钥大小必须为 32 字节</string>
     <string name="key_length_explanation_hex">：WireGuard 的十六进制密钥长度必须为 64 个字符（32 字节）</string>
     <string name="listen_port">监听端口</string>
-    <string name="log_export_error">无法导出日志：%s</string>
     <string name="log_export_success">已保存至 “%s”</string>
-    <string name="log_export_summary">日志文件将保存至下载文件夹</string>
     <string name="log_export_title">导出日志文件</string>
     <string name="logcat_error">无法运行 logcat：</string>
     <string name="module_version_error">无法确定内核模块版本</string>
diff --git a/ui/src/main/res/values/colors.xml b/ui/src/main/res/values/colors.xml
index 06bcd143..bd304726 100644
--- a/ui/src/main/res/values/colors.xml
+++ b/ui/src/main/res/values/colors.xml
@@ -18,4 +18,9 @@
     <color name="mtrl_textinput_default_box_stroke_color" tools:override="true">@color/secondary_color</color>
     <color name="white">#ffffffff</color>
 
+    <!-- Log viewer tag colors -->
+    <color name="debug_tag_color">#444444</color>
+    <color name="error_tag_color">#aa0000</color>
+    <color name="info_tag_color">#00aa00</color>
+    <color name="warning_tag_color">#aaaa00</color>
 </resources>
diff --git a/ui/src/main/res/values/strings.xml b/ui/src/main/res/values/strings.xml
index 74c5be69..972b6244 100644
--- a/ui/src/main/res/values/strings.xml
+++ b/ui/src/main/res/values/strings.xml
@@ -93,10 +93,9 @@
     <string name="key_length_explanation_binary">: WireGuard keys must be 32 bytes</string>
     <string name="key_length_explanation_hex">: WireGuard hex keys must be 64 characters (32 bytes)</string>
     <string name="listen_port">Listen port</string>
-    <string name="log_export_error">Unable to export log: %s</string>
     <string name="log_export_success">Saved to “%s”</string>
-    <string name="log_export_summary">Log file will be saved to downloads folder</string>
     <string name="log_export_title">Export log file</string>
+    <string name="log_export_subject">WireGuard Android Log File</string>
     <string name="logcat_error">Unable to run logcat: </string>
     <string name="module_version_error">Unable to determine kernel module version</string>
     <string name="module_installer_not_found">No modules are available for your device</string>
@@ -186,4 +185,7 @@
     <string name="zip_export_title">Export tunnels to zip file</string>
     <string name="key_length_error">Incorrect key length</string>
     <string name="key_contents_error">Bad characters in key</string>
+    <string name="log_viewer_title">View application log</string>
+    <string name="log_viewer_pref_summary">Logs may assist with debugging</string>
+    <string name="log_saver_activity_label">Save log</string>
 </resources>
diff --git a/ui/src/main/res/xml/preferences.xml b/ui/src/main/res/xml/preferences.xml
index 4668fab4..06d7ac7c 100644
--- a/ui/src/main/res/xml/preferences.xml
+++ b/ui/src/main/res/xml/preferences.xml
@@ -8,7 +8,10 @@
         android:summaryOff="@string/restore_on_boot_summary_off"
         android:title="@string/restore_on_boot_title" />
     <com.wireguard.android.preference.ZipExporterPreference />
-    <com.wireguard.android.preference.LogExporterPreference />
+    <Preference
+        android:key="log_viewer"
+        android:title="@string/log_viewer_title"
+        android:summary="@string/log_viewer_pref_summary" />
     <CheckBoxPreference
         android:defaultValue="false"
         android:key="dark_theme"