lightbox: Add download button to bottom app bar.

Fixes: #42

Author: chimnayajith

android/app/src/main/kotlin/com/zulip/flutter/DownloadManager.g.kt

@@ -0,0 +1,99 @@
+// Autogenerated from Pigeon (v22.7.2), do not edit directly.
+// See also: https://pub.dev/packages/pigeon
+@file:Suppress("UNCHECKED_CAST", "ArrayInDataClass")
+
+package com.zulip.flutter
+
+import android.util.Log
+import io.flutter.plugin.common.BasicMessageChannel
+import io.flutter.plugin.common.BinaryMessenger
+import io.flutter.plugin.common.EventChannel
+import io.flutter.plugin.common.MessageCodec
+import io.flutter.plugin.common.StandardMethodCodec
+import io.flutter.plugin.common.StandardMessageCodec
+import java.io.ByteArrayOutputStream
+import java.nio.ByteBuffer
+
+private fun wrapResult(result: Any?): List<Any?> {
+  return listOf(result)
+}
+
+private fun wrapError(exception: Throwable): List<Any?> {
+  return if (exception is DownloadManagerError) {
+    listOf(
+      exception.code,
+      exception.message,
+      exception.details
+    )
+  } else {
+    listOf(
+      exception.javaClass.simpleName,
+      exception.toString(),
+      "Cause: " + exception.cause + ", Stacktrace: " + Log.getStackTraceString(exception)
+    )
+  }
+}
+
+/**
+ * Error class for passing custom error details to Flutter via a thrown PlatformException.
+ * @property code The error code.
+ * @property message The error message.
+ * @property details The error details. Must be a datatype supported by the api codec.
+ */
+class DownloadManagerError (
+  val code: String,
+  override val message: String? = null,
+  val details: Any? = null
+) : Throwable()
+private open class DownloadManagerPigeonCodec : StandardMessageCodec() {
+  override fun readValueOfType(type: Byte, buffer: ByteBuffer): Any? {
+    return     super.readValueOfType(type, buffer)
+  }
+  override fun writeValue(stream: ByteArrayOutputStream, value: Any?)   {
+    super.writeValue(stream, value)
+  }
+}
+
+
+/** Generated interface from Pigeon that represents a handler of messages from Flutter. */
+interface DownloadManagerHostApi {
+  /**
+   * Downloads a file using the given URL and saves it with the specified file name in the Downloads directory.
+   * Returns a success message or an error message.
+   */
+  fun downloadFile(fileUrl: String, fileName: String, header: String, callback: (Result<String>) -> Unit)
+
+  companion object {
+    /** The codec used by DownloadManagerHostApi. */
+    val codec: MessageCodec<Any?> by lazy {
+      DownloadManagerPigeonCodec()
+    }
+    /** Sets up an instance of `DownloadManagerHostApi` to handle messages through the `binaryMessenger`. */
+    @JvmOverloads
+    fun setUp(binaryMessenger: BinaryMessenger, api: DownloadManagerHostApi?, messageChannelSuffix: String = "") {
+      val separatedMessageChannelSuffix = if (messageChannelSuffix.isNotEmpty()) ".$messageChannelSuffix" else ""
+      run {
+        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.zulip.DownloadManagerHostApi.downloadFile$separatedMessageChannelSuffix", codec)
+        if (api != null) {
+          channel.setMessageHandler { message, reply ->
+            val args = message as List<Any?>
+            val fileUrlArg = args[0] as String
+            val fileNameArg = args[1] as String
+            val headerArg = args[2] as String
+            api.downloadFile(fileUrlArg, fileNameArg, headerArg) { result: Result<String> ->
+              val error = result.exceptionOrNull()
+              if (error != null) {
+                reply.reply(wrapError(error))
+              } else {
+                val data = result.getOrNull()
+                reply.reply(wrapResult(data))
+              }
+            }
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
+    }
+  }
+}

android/app/src/main/kotlin/com/zulip/flutter/ZulipPlugin.kt

@@ -1,11 +1,13 @@
 package com.zulip.flutter
 
 import android.annotation.SuppressLint
+import android.app.DownloadManager
 import android.content.ContentUris
 import android.content.ContentValues
 import android.content.Context
 import android.content.Intent
 import android.media.AudioAttributes
+import android.media.MediaScannerConnection
 import android.net.Uri
 import android.os.Build
 import android.os.Bundle
@@ -19,7 +21,7 @@ import androidx.core.app.NotificationCompat
 import androidx.core.app.NotificationManagerCompat
 import androidx.core.graphics.drawable.IconCompat
 import io.flutter.embedding.engine.plugins.FlutterPlugin
-
+import org.json.JSONObject
 private const val TAG = "ZulipPlugin"
 
 fun toAndroidPerson(person: Person): androidx.core.app.Person {
@@ -283,17 +285,50 @@ private class AndroidNotificationHost(val context: Context)
     }
 }
 
+/** Host class for handling downloads via DownloadManager */
+class DownloadHost(private val context: Context) : DownloadManagerHostApi {
+
+    /** Downloads a file from the given URL and saves it to the specified filename in the Downloads folder. */
+    override fun downloadFile(url: String, fileName: String, header: String, callback: (Result<String>) -> Unit) {
+        val downloadManager = context.getSystemService(Context.DOWNLOAD_SERVICE) as DownloadManager
+        val headersJsonObject = JSONObject(header)
+        val headersMap = mutableMapOf<String, String>()
+        for (key in headersJsonObject.keys()) {
+            headersMap[key] = headersJsonObject.getString(key)
+        }
+        val uri = Uri.parse(url)
+
+        val request = DownloadManager.Request(uri).apply {
+            setTitle("Downloading $fileName")
+            setDescription("File is being downloaded...")
+            setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, fileName)
+            setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED)
+
+            for ((key, value) in headersMap) {
+                addRequestHeader(key, value)
+            }
+        }
+        // Queue the download
+        downloadManager.enqueue(request)
+        callback(Result.success("Download started successfully for: $fileName"))
+    }
+}
+
 /** A Flutter plugin for the Zulip app's ad-hoc needs. */
 // @Keep is needed because this class is used only
 // from ZulipShimPlugin, via reflection.
 @Keep
-class ZulipPlugin : FlutterPlugin { // TODO ActivityAware too?
+class ZulipPlugin : FlutterPlugin {
     private var notificationHost: AndroidNotificationHost? = null
+    private var downloadHost: DownloadHost? = null
 
     override fun onAttachedToEngine(binding: FlutterPlugin.FlutterPluginBinding) {
         Log.d(TAG, "Attaching to Flutter engine.")
         notificationHost = AndroidNotificationHost(binding.applicationContext)
+        downloadHost = DownloadHost(binding.applicationContext)
+
         AndroidNotificationHostApi.setUp(binding.binaryMessenger, notificationHost)
+        DownloadManagerHostApi.setUp(binding.binaryMessenger, downloadHost)
     }
 
     override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
@@ -302,6 +337,9 @@ class ZulipPlugin : FlutterPlugin { // TODO ActivityAware too?
             return
         }
         AndroidNotificationHostApi.setUp(binding.binaryMessenger, null)
+        DownloadManagerHostApi.setUp(binding.binaryMessenger, null)
+
         notificationHost = null
+        downloadHost = null
     }
-}
+}

assets/l10n/app_en.arb

@@ -395,6 +395,22 @@
   "@lightboxCopyLinkTooltip": {
     "description": "Tooltip in lightbox for the copy link action."
   },
+  "lightboxDownloadImageTooltip": "Download image",
+  "@lightboxDownloadImageTooltip": {
+    "description": "Tooltip in lightbox for the download image action."
+  },
+  "lightboxDownloadImageSuccess": "Image downloaded successfully!",
+  "@lightboxDownloadImageSuccess": {
+    "description": "Message shown when the image downloads successfully."
+  },
+  "lightboxDownloadImageFailed": "Failed to download the image.",
+  "@lightboxDownloadImageFailed": {
+    "description": "Message shown when the image download fails."
+  },
+  "lightboxDownloadImageError": "An error occurred while downloading the image.",
+  "@lightboxDownloadImageError": {
+    "description": "Message shown when an unexpected error occurs during image download."
+  },
   "loginPageTitle": "Log in",
   "@loginPageTitle": {
     "description": "Title for login page."

lib/generated/l10n/zulip_localizations.dart

@@ -633,6 +633,30 @@ abstract class ZulipLocalizations {
   /// **'Copy link'**
   String get lightboxCopyLinkTooltip;
 
+  /// Tooltip in lightbox for the download image action.
+  ///
+  /// In en, this message translates to:
+  /// **'Download image'**
+  String get lightboxDownloadImageTooltip;
+
+  /// Message shown when the image downloads successfully.
+  ///
+  /// In en, this message translates to:
+  /// **'Image downloaded successfully!'**
+  String get lightboxDownloadImageSuccess;
+
+  /// Message shown when the image download fails.
+  ///
+  /// In en, this message translates to:
+  /// **'Failed to download the image.'**
+  String get lightboxDownloadImageFailed;
+
+  /// Message shown when an unexpected error occurs during image download.
+  ///
+  /// In en, this message translates to:
+  /// **'An error occurred while downloading the image.'**
+  String get lightboxDownloadImageError;
+
   /// Title for login page.
   ///
   /// In en, this message translates to:

lib/generated/l10n/zulip_localizations_ar.dart

@@ -310,6 +310,18 @@ class ZulipLocalizationsAr extends ZulipLocalizations {
   @override
   String get lightboxCopyLinkTooltip => 'Copy link';
 
+  @override
+  String get lightboxDownloadImageTooltip => 'Download image';
+
+  @override
+  String get lightboxDownloadImageSuccess => 'Image downloaded successfully!';
+
+  @override
+  String get lightboxDownloadImageFailed => 'Failed to download the image.';
+
+  @override
+  String get lightboxDownloadImageError => 'An error occurred while downloading the image.';
+
   @override
   String get loginPageTitle => 'Log in';
 

lib/generated/l10n/zulip_localizations_en.dart

@@ -310,6 +310,18 @@ class ZulipLocalizationsEn extends ZulipLocalizations {
   @override
   String get lightboxCopyLinkTooltip => 'Copy link';
 
+  @override
+  String get lightboxDownloadImageTooltip => 'Download image';
+
+  @override
+  String get lightboxDownloadImageSuccess => 'Image downloaded successfully!';
+
+  @override
+  String get lightboxDownloadImageFailed => 'Failed to download the image.';
+
+  @override
+  String get lightboxDownloadImageError => 'An error occurred while downloading the image.';
+
   @override
   String get loginPageTitle => 'Log in';
 

lib/generated/l10n/zulip_localizations_ja.dart

@@ -310,6 +310,18 @@ class ZulipLocalizationsJa extends ZulipLocalizations {
   @override
   String get lightboxCopyLinkTooltip => 'Copy link';
 
+  @override
+  String get lightboxDownloadImageTooltip => 'Download image';
+
+  @override
+  String get lightboxDownloadImageSuccess => 'Image downloaded successfully!';
+
+  @override
+  String get lightboxDownloadImageFailed => 'Failed to download the image.';
+
+  @override
+  String get lightboxDownloadImageError => 'An error occurred while downloading the image.';
+
   @override
   String get loginPageTitle => 'Log in';
 

lib/generated/l10n/zulip_localizations_nb.dart

@@ -310,6 +310,18 @@ class ZulipLocalizationsNb extends ZulipLocalizations {
   @override
   String get lightboxCopyLinkTooltip => 'Copy link';
 
+  @override
+  String get lightboxDownloadImageTooltip => 'Download image';
+
+  @override
+  String get lightboxDownloadImageSuccess => 'Image downloaded successfully!';
+
+  @override
+  String get lightboxDownloadImageFailed => 'Failed to download the image.';
+
+  @override
+  String get lightboxDownloadImageError => 'An error occurred while downloading the image.';
+
   @override
   String get loginPageTitle => 'Log in';
 

lib/generated/l10n/zulip_localizations_pl.dart

@@ -310,6 +310,18 @@ class ZulipLocalizationsPl extends ZulipLocalizations {
   @override
   String get lightboxCopyLinkTooltip => 'Skopiuj odnośnik';
 
+  @override
+  String get lightboxDownloadImageTooltip => 'Download image';
+
+  @override
+  String get lightboxDownloadImageSuccess => 'Image downloaded successfully!';
+
+  @override
+  String get lightboxDownloadImageFailed => 'Failed to download the image.';
+
+  @override
+  String get lightboxDownloadImageError => 'An error occurred while downloading the image.';
+
   @override
   String get loginPageTitle => 'Zaloguj';
 

lib/generated/l10n/zulip_localizations_ru.dart

@@ -310,6 +310,18 @@ class ZulipLocalizationsRu extends ZulipLocalizations {
   @override
   String get lightboxCopyLinkTooltip => 'Скопировать ссылку';
 
+  @override
+  String get lightboxDownloadImageTooltip => 'Download image';
+
+  @override
+  String get lightboxDownloadImageSuccess => 'Image downloaded successfully!';
+
+  @override
+  String get lightboxDownloadImageFailed => 'Failed to download the image.';
+
+  @override
+  String get lightboxDownloadImageError => 'An error occurred while downloading the image.';
+
   @override
   String get loginPageTitle => 'Вход в систему';