Enable setting the default posting language from Tusky (#2946)

* Extract locale utils

* Extract makeIcon

* Allow setting the (server-synchronized) default posting language from Tusky.
Closes #2902

* Add copyright headers

* Address review feedback

app/src/main/java/com/keylesspalace/tusky/util/IconUtils.kt

@@ -0,0 +1,31 @@
+/* Copyright 2022 Tusky Contributors
+ *
+ * This file is a part of Tusky.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Tusky; if not,
+ * see <http://www.gnu.org/licenses>. */
+
+package com.keylesspalace.tusky.util
+
+import android.content.Context
+import androidx.annotation.Px
+import com.keylesspalace.tusky.R
+import com.mikepenz.iconics.IconicsDrawable
+import com.mikepenz.iconics.typeface.library.googlematerial.GoogleMaterial
+import com.mikepenz.iconics.utils.colorInt
+import com.mikepenz.iconics.utils.sizePx
+
+fun makeIcon(context: Context, icon: GoogleMaterial.Icon, @Px iconSize: Int): IconicsDrawable {
+    return IconicsDrawable(context, icon).apply {
+        sizePx = iconSize
+        colorInt = ThemeUtils.getColor(context, R.attr.iconColor)
+    }
+}

app/src/main/java/com/keylesspalace/tusky/util/LocaleExtensions.kt

@@ -1,5 +1,22 @@
+/* Copyright 2022 Tusky Contributors
+ *
+ * This file is a part of Tusky.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Tusky; if not,
+ * see <http://www.gnu.org/licenses>. */
+
 package com.keylesspalace.tusky.util
 
+import android.content.Context
+import com.keylesspalace.tusky.R
 import java.util.Locale
 
 // When a language code has changed, `language` *explicitly* returns the obsolete version,
@@ -9,3 +26,11 @@ val Locale.modernLanguageCode: String
     get() {
         return this.toLanguageTag().split('-', limit = 2)[0]
     }
+
+fun Locale.getTuskyDisplayName(context: Context): String {
+    return context.getString(
+        R.string.language_display_name_format,
+        this?.displayLanguage,
+        this?.getDisplayLanguage(this)
+    )
+}

app/src/main/java/com/keylesspalace/tusky/util/LocaleUtils.kt

@@ -0,0 +1,89 @@
+/* Copyright 2022 Tusky Contributors
+ *
+ * This file is a part of Tusky.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Tusky; if not,
+ * see <http://www.gnu.org/licenses>. */
+
+package com.keylesspalace.tusky.util
+
+import android.util.Log
+import androidx.appcompat.app.AppCompatDelegate
+import androidx.core.os.LocaleListCompat
+import com.keylesspalace.tusky.db.AccountEntity
+import java.util.Locale
+
+private const val TAG: String = "LocaleUtils"
+
+private fun mergeLocaleListCompat(list: MutableList<Locale>, localeListCompat: LocaleListCompat) {
+    for (index in 0 until localeListCompat.size()) {
+        val locale = localeListCompat[index]
+        if (locale != null && list.none { locale.language == it.language }) {
+            list.add(locale)
+        }
+    }
+}
+
+// Ensure that the locale whose code matches the given language is first in the list
+private fun ensureLanguageIsFirst(locales: MutableList<Locale>, language: String) {
+    var currentLocaleIndex = locales.indexOfFirst { it.language == language }
+    if (currentLocaleIndex < 0) {
+        // Recheck against modern language codes
+        // This should only happen when replying or when the per-account post language is set
+        // to a modern code
+        currentLocaleIndex = locales.indexOfFirst { it.modernLanguageCode == language }
+
+        if (currentLocaleIndex < 0) {
+            // This can happen when:
+            // - Your per-account posting language is set to one android doesn't know (e.g. toki pona)
+            // - Replying to a post in a language android doesn't know
+            locales.add(0, Locale(language))
+            Log.w(TAG, "Attempting to use unknown language tag '$language'")
+            return
+        }
+    }
+
+    if (currentLocaleIndex > 0) {
+        // Move preselected locale to the top
+        locales.add(0, locales.removeAt(currentLocaleIndex))
+    }
+}
+
+fun getInitialLanguage(language: String? = null, activeAccount: AccountEntity? = null): String {
+    return if (language.isNullOrEmpty()) {
+        // Account-specific language set on the server
+        if (activeAccount?.defaultPostLanguage?.isNotEmpty() == true) {
+            activeAccount.defaultPostLanguage
+        } else {
+            // Setting the application ui preference sets the default locale
+            AppCompatDelegate.getApplicationLocales()[0]?.language
+                ?: Locale.getDefault().language
+        }
+    } else {
+        language
+    }
+}
+
+fun getLocaleList(initialLanguage: String): List<Locale> {
+    val locales = mutableListOf<Locale>()
+    mergeLocaleListCompat(locales, AppCompatDelegate.getApplicationLocales()) // configured app languages first
+    mergeLocaleListCompat(locales, LocaleListCompat.getDefault()) // then configured system languages
+    locales.addAll( // finally, other languages
+        // Only "base" languages, "en" but not "en_DK"
+        Locale.getAvailableLocales().filter {
+            it.country.isNullOrEmpty() &&
+                it.script.isNullOrEmpty() &&
+                it.variant.isNullOrEmpty()
+        }
+    )
+    ensureLanguageIsFirst(locales, initialLanguage)
+    return locales
+}