feat(card-browser): search history

AnkiDroid/src/main/java/com/ichi2/anki/CrashReportService.kt

@@ -93,7 +93,7 @@ object CrashReportService {
         val builder =
             CoreConfigurationBuilder()
                 .withBuildConfigClass(com.ichi2.anki.BuildConfig::class.java) // AnkiDroid BuildConfig - Acrarium#319
-                .withExcludeMatchingSharedPreferencesKeys("username", "hkey")
+                .withExcludeMatchingSharedPreferencesKeys("username", "hkey", "browser_search_history")
                 .withSharedPreferencesName("acra")
                 .withReportContent(
                     ReportField.REPORT_ID,

AnkiDroid/src/main/java/com/ichi2/anki/browser/SearchHistory.kt

@@ -0,0 +1,105 @@
+/*
+ *  Copyright (c) 2026 David Allison <[email protected]>
+ *
+ *  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.
+ *
+ *  This program 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
+ *  this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.ichi2.anki.browser
+
+import com.ichi2.anki.R
+import com.ichi2.anki.settings.Prefs
+import com.ichi2.anki.settings.PrefsRepository
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
+import timber.log.Timber
+
+/**
+ * The user's past searches in the Card Browser.
+ *
+ * Displayed in most recently used order.
+ */
+class SearchHistory(
+    private val prefs: PrefsRepository = Prefs,
+    private val maxEntries: Int = MAX_ENTRIES,
+) {
+    /**
+     * The user's past searches in the Card Browser.
+     * Displayed in most recently used order.
+     */
+    var entries: List<SearchHistoryEntry>
+        get() {
+            val jsonString = prefs.getString(R.string.pref_browser_search_history, "[]") ?: "[]"
+            return runCatching {
+                Json.decodeFromString<List<SearchHistoryEntry>>(jsonString)
+            }.getOrElse { emptyList() }
+        }
+        private set(value) {
+            Timber.i("updating history entries: %d values", value.size)
+            val json = Json.encodeToString(value)
+            prefs.putString(R.string.pref_browser_search_history, json)
+        }
+
+    /**
+     * Adds the provided entry to the head of the list. Returns the updated list.
+     *
+     * If the entry already exists, it will be moved to the head.
+     */
+    fun addRecent(entry: SearchHistoryEntry): List<SearchHistoryEntry> {
+        val updatedEntries = entries.toMutableList()
+        updatedEntries.remove(entry)
+        updatedEntries.add(0, entry)
+        return updatedEntries.take(maxEntries).also {
+            this.entries = it.toMutableList()
+            Timber.d("updated history with '%s'", entry)
+        }
+    }
+
+    /**
+     * Removes [entry] from [entries]. Returning whether the element was contained in the collection.
+     */
+    fun removeEntry(entry: SearchHistoryEntry): Boolean {
+        val newEntries = entries.toMutableList()
+        Timber.d("removing entry '%s'", entry)
+        return newEntries.remove(entry).also {
+            this.entries = newEntries
+        }
+    }
+
+    fun clear() {
+        Timber.i("clearing all entries")
+        this.entries = listOf()
+    }
+
+    /**
+     * An entry in the history of the card browser.
+     * This is user-supplied, so may contain PII.
+     * @see SearchHistory
+     */
+    // !! When updating this, consider equality in addRecent
+    @Serializable
+    data class SearchHistoryEntry(
+        @SerialName("q")
+        val query: String,
+    ) {
+        override fun toString() = query
+    }
+
+    companion object {
+        /**
+         * The maximum number of search history entries to store.
+         * https://github.com/ankitects/anki/blob/e9cc65569807771f548fc9c2634aabc7b2f90ed2/qt/aqt/browser/browser.py#L541
+         */
+        const val MAX_ENTRIES = 30
+    }
+}

AnkiDroid/src/main/res/values/browser.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~  Copyright (c) 2026 David Allison <[email protected]>
+  ~
+  ~  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.
+  ~
+  ~  This program 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
+  ~  this program.  If not, see <http://www.gnu.org/licenses/>.
+  -->
+<resources>
+    <string name="pref_browser_search_history">browser_search_history</string>
+</resources>

AnkiDroid/src/test/java/com/ichi2/anki/browser/SearchHistoryTest.kt

@@ -0,0 +1,139 @@
+/*
+ *  Copyright (c) 2026 David Allison <[email protected]>
+ *
+ *  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.
+ *
+ *  This program 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
+ *  this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.ichi2.anki.browser
+
+import androidx.annotation.CheckResult
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.ichi2.anki.R
+import com.ichi2.anki.RobolectricTest
+import com.ichi2.anki.browser.SearchHistory.SearchHistoryEntry
+import com.ichi2.anki.settings.Prefs
+import com.ichi2.testutils.getString
+import org.hamcrest.MatcherAssert.assertThat
+import org.hamcrest.Matchers.empty
+import org.hamcrest.Matchers.equalTo
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.junit.runner.RunWith
+
+/**
+ * Tests for [SearchHistory]
+ */
+@RunWith(AndroidJUnit4::class)
+class SearchHistoryTest : RobolectricTest() {
+    private val history =
+        SearchHistory(maxEntries = 5).apply {
+            this.clear()
+        }
+
+    @Test
+    fun `entries is empty if no key is set`() {
+        assertThat(history.entries, empty())
+    }
+
+    @Test
+    fun `entries is empty if corrupt`() {
+        writeSearchHistoryRaw("A")
+        assertThat(history.entries, empty())
+    }
+
+    @Test
+    fun `entries returns written value`() {
+        history.addRecent(SearchHistoryEntry("A"))
+        assertEntriesEquals("A")
+    }
+
+    @Test
+    fun `entries skips duplicate values`() {
+        history.addRecent(SearchHistoryEntry("A"))
+        history.addRecent(SearchHistoryEntry("A"))
+        assertEntriesEquals("A")
+    }
+
+    @Test
+    fun `entries returns latest values first`() {
+        history.addRecent(SearchHistoryEntry("A"))
+        history.addRecent(SearchHistoryEntry("B"))
+        assertEntriesEquals("B", "A")
+    }
+
+    @Test
+    fun `entries truncates least recently used`() {
+        addNumberedEntries(6)
+        assertEntriesEquals("6", "5", "4", "3", "2")
+
+        // no more truncation occurs
+        history.addRecent(SearchHistoryEntry("2"))
+        assertEntriesEquals("2", "6", "5", "4", "3")
+    }
+
+    @Test
+    fun `clear on empty list does nothing`() {
+        history.clear()
+        assertThat(history.entries, empty())
+    }
+
+    @Test
+    fun `clear on full list empties list`() {
+        addNumberedEntries(6)
+        history.clear()
+        assertThat(history.entries, empty())
+    }
+
+    @Test
+    fun `remove non-existing entry`() {
+        assertFalse(history.removeEntry(SearchHistoryEntry("AA")))
+    }
+
+    @Test
+    fun `remove existing entry`() {
+        addNumberedEntries(6)
+        assertTrue(history.removeEntry(SearchHistoryEntry("5")))
+        assertEntriesEquals("6", "4", "3", "2")
+    }
+
+    @Test
+    fun `pref key is unchanged`() {
+        // this is checked in CrashReportService to ensure user data isn't sent to our servers.
+        assertThat(getString(R.string.pref_browser_search_history), equalTo("browser_search_history"))
+    }
+
+    @Test
+    fun `v1 serialization is unchanged`() {
+        // additional properties will be added; make sure we don't corrupt past entries
+        addNumberedEntries(1)
+        assertThat(readSearchHistoryRaw(), equalTo("""[{"q":"1"}]"""))
+        assertThat(history.entries.single().query, equalTo("1"))
+    }
+
+    /** Adds numbered entries from 1 to [count] inclusive */
+    fun addNumberedEntries(count: Int) =
+        repeat(count) {
+            history.addRecent(SearchHistoryEntry((it + 1).toString()))
+        }
+
+    fun assertEntriesEquals(vararg entries: String) {
+        val listOfEntities = entries.map(::SearchHistoryEntry)
+        assertThat(history.entries, equalTo(listOfEntities))
+    }
+}
+
+fun writeSearchHistoryRaw(value: String?) = Prefs.putString(R.string.pref_browser_search_history, value)
+
+@CheckResult
+fun readSearchHistoryRaw() = Prefs.getString(R.string.pref_browser_search_history, null)!!