If depicted Wikidata item has no associated Commons category property, then suggest categories from its P18 (#6130)

* Fix NPE with UploadMediaDetails.captionText

* Store P18 instead of processed image url in DepictedItem

* Add routes for fetching category info from titles

* Consider depict's P18 when suggesting categories

* Add tests

* Corrected DepictedItem constructor arguments

* Add test for DepictedItem::primaryImage

app/src/main/java/fr/free/nrw/commons/category/CategoriesModel.kt

@@ -127,14 +127,41 @@ class CategoriesModel
         /**
          * Fetches details of every category associated with selected depictions, converts them into
          * CategoryItem and returns them in a list.
+         * If a selected depiction has no categories, the categories in which its P18 belongs are
+         * returned in the list.
          *
          * @param selectedDepictions selected DepictItems
          * @return List of CategoryItem associated with selected depictions
          */
-        private fun categoriesFromDepiction(selectedDepictions: List<DepictedItem>): Observable<MutableList<CategoryItem>>? =
+        private fun categoriesFromDepiction(selectedDepictions: List<DepictedItem>): Observable<MutableList<CategoryItem>>? {
+            val observables =  selectedDepictions.map { depictedItem ->
+                if (depictedItem.commonsCategories.isEmpty()) {
+                    if (depictedItem.primaryImage == null) {
+                        return@map Observable.just(emptyList<CategoryItem>())
+                    }
+                    Observable.just(
+                            depictedItem.primaryImage
+                        ).map { image ->
+                            categoryClient
+                                .getCategoriesOfImage(
+                                    image,
+                                    SEARCH_CATS_LIMIT,
+                                ).map {
+                                    it.map { category ->
+                                        CategoryItem(
+                                            category.name,
+                                            category.description,
+                                            category.thumbnail,
+                                            category.isSelected,
+                                        )
+                                    }
+                                }.blockingGet()
+                        }.flatMapIterable { it }.toList()
+                        .toObservable()
+                } else {
                     Observable
                         .fromIterable(
-                    selectedDepictions.map { it.commonsCategories }.flatten(),
+                            depictedItem.commonsCategories,
                         ).map { categoryItem ->
                             categoryClient
                                 .getCategoriesByName(
@@ -151,6 +178,13 @@ class CategoriesModel
                                 }.blockingGet()
                         }.toList()
                         .toObservable()
+                }
+            }
+            return Observable.concat(observables)
+                .scan(mutableListOf<CategoryItem>()) { accumulator, currentList ->
+                    accumulator.apply { addAll(currentList) }
+                }
+        }
 
         /**
          * Fetches details of every category by their name, converts them into

app/src/main/java/fr/free/nrw/commons/category/CategoryClient.kt

@@ -78,6 +78,24 @@ class CategoryClient
                 ),
             )
 
+        /**
+         * Fetches categories belonging to an image (P18 of some wikidata entity).
+         *
+         * @param image P18 of some wikidata entity
+         * @param itemLimit How many categories to return
+         * @return Single Observable emitting the list of categories
+         */
+        fun getCategoriesOfImage(
+            image: String,
+            itemLimit: Int,
+        ): Single<List<CategoryItem>> =
+            responseMapper(
+                categoryInterface.getCategoriesByTitles(
+                    "File:${image}",
+                    itemLimit,
+                ),
+            )
+
         /**
          * The method takes categoryName as input and returns a List of Subcategories
          * It uses the generator query API to get the subcategories in a category, 500 at a time.

app/src/main/java/fr/free/nrw/commons/category/CategoryInterface.kt

@@ -61,6 +61,21 @@ interface CategoryInterface {
         @Query("gacoffset") offset: Int,
     ): Single<MwQueryResponse>
 
+    /**
+     * Fetches non-hidden categories by titles.
+     *
+     * @param titles titles to fetch categories for (e.g. File:<P18 of a wikidata entity>)
+     * @param itemLimit How many categories to return
+     * @return MwQueryResponse
+     */
+    @GET(
+        "w/api.php?action=query&format=json&formatversion=2&generator=categories&prop=categoryinfo|description|pageimages&piprop=thumbnail&pithumbsize=70&gclshow=!hidden",
+    )
+    fun getCategoriesByTitles(
+        @Query("titles") titles: String?,
+        @Query("gcllimit") itemLimit: Int,
+    ): Single<MwQueryResponse>
+
     @GET("w/api.php?action=query&format=json&formatversion=2&generator=categorymembers&gcmtype=subcat&prop=info&gcmlimit=50")
     fun getSubCategoryList(
         @Query("gcmtitle") categoryName: String,

app/src/main/java/fr/free/nrw/commons/upload/structure/depictions/DepictedItem.kt

@@ -68,6 +68,9 @@ data class DepictedItem constructor(
         entity.id(),
     )
 
+    val primaryImage: String?
+        get() = imageUrl?.split('-')?.lastOrNull()
+
     override fun equals(other: Any?) =
         when {
             this === other -> true

app/src/test/kotlin/fr/free/nrw/commons/category/CategoriesModelTest.kt

@@ -1,7 +1,9 @@
 package fr.free.nrw.commons.category
 
 import categoryItem
+import com.nhaarman.mockitokotlin2.any
 import com.nhaarman.mockitokotlin2.mock
+import com.nhaarman.mockitokotlin2.times
 import com.nhaarman.mockitokotlin2.verify
 import com.nhaarman.mockitokotlin2.whenever
 import depictedItem
@@ -99,6 +101,10 @@ class CategoriesModelTest {
                     ),
                 ),
             )
+        val depictedItemWithoutCategories =
+            depictedItem(
+                imageUrl = "testUrl"
+            )
 
         whenever(gpsCategoryModel.categoriesFromLocation)
             .thenReturn(
@@ -159,6 +165,23 @@ class CategoriesModelTest {
                 ),
             ),
         )
+        whenever(
+            categoryClient.getCategoriesOfImage(
+                "testUrl",
+                25,
+            ),
+        ).thenReturn(
+            Single.just(
+                listOf(
+                    CategoryItem(
+                        "categoriesOfP18",
+                        "",
+                        "",
+                        false,
+                    ),
+                ),
+            ),
+        )
         val imageTitleList = listOf("Test")
         CategoriesModel(categoryClient, categoryDao, gpsCategoryModel)
             .searchAll("", imageTitleList, listOf(depictedItem))
@@ -171,8 +194,21 @@ class CategoriesModelTest {
                     categoryItem("recentCategories"),
                 ),
             )
+        CategoriesModel(categoryClient, categoryDao, gpsCategoryModel)
+            .searchAll("", imageTitleList, listOf(depictedItemWithoutCategories))
+            .test()
+            .assertValue(
+                listOf(
+                    categoryItem("categoriesOfP18"),
+                    categoryItem("gpsCategory"),
+                    categoryItem("titleSearch"),
+                    categoryItem("recentCategories"),
+                ),
+            )
         imageTitleList.forEach {
-            verify(categoryClient).searchCategories(it, CategoriesModel.SEARCH_CATS_LIMIT)
+            verify(categoryClient, times(2)).searchCategories(it, CategoriesModel.SEARCH_CATS_LIMIT)
+            verify(categoryClient).getCategoriesByName(any(), any(), any(), any())
+            verify(categoryClient).getCategoriesOfImage(any(), any())
         }
     }
 

app/src/test/kotlin/fr/free/nrw/commons/category/CategoryClientTest.kt

@@ -132,6 +132,45 @@ class CategoryClientTest {
             )
     }
 
+    @Test
+    fun getCategoriesByTitlesFound() {
+        val mockResponse = withMockResponse("Category:Test")
+        whenever(
+            categoryInterface.getCategoriesByTitles(
+                anyString(),
+                anyInt(),
+            ),
+        ).thenReturn(Single.just(mockResponse))
+        categoryClient
+            .getCategoriesOfImage("tes", 10)
+            .test()
+            .assertValues(
+                listOf(
+                    CategoryItem(
+                        "Test",
+                        "",
+                        "",
+                        false,
+                    ),
+                ),
+            )
+        categoryClient
+            .getCategoriesOfImage(
+                "tes",
+                10,
+            ).test()
+            .assertValues(
+                listOf(
+                    CategoryItem(
+                        "Test",
+                        "",
+                        "",
+                        false,
+                    ),
+                ),
+            )
+    }
+
     @Test
     fun getCategoriesByNameNull() {
         val mockResponse = withNullPages()
@@ -160,6 +199,29 @@ class CategoryClientTest {
             .assertValues(emptyList())
     }
 
+    @Test
+    fun getCategoriesByTitlesNull() {
+        val mockResponse = withNullPages()
+        whenever(
+            categoryInterface.getCategoriesByTitles(
+                anyString(),
+                anyInt(),
+            ),
+        ).thenReturn(Single.just(mockResponse))
+        categoryClient
+            .getCategoriesOfImage(
+                "tes",
+                10,
+            ).test()
+            .assertValues(emptyList())
+        categoryClient
+            .getCategoriesOfImage(
+                "tes",
+                10,
+            ).test()
+            .assertValues(emptyList())
+    }
+
     @Test
     fun getParentCategoryListFound() {
         val mockResponse = withMockResponse("Category:Test")

app/src/test/kotlin/fr/free/nrw/commons/upload/structure/depictions/DepictedItemTest.kt

@@ -181,4 +181,20 @@ class DepictedItemTest {
     fun `hashCode returns different values for objects with different name`() {
         Assert.assertNotEquals(depictedItem(name = "a").hashCode(), depictedItem(name = "b").hashCode())
     }
+
+    @Test
+    fun `primaryImage is derived correctly from imageUrl`() {
+        Assert.assertEquals(
+            DepictedItem(
+                entity(
+                    statements = mapOf(
+                        WikidataProperties.IMAGE.propertyName to listOf(
+                            statement(snak(dataValue = valueString("prefix: example_image name"))),
+                        ),
+                    ),
+                ),
+            ).primaryImage,
+            "_example_image_name",
+        )
+    }
 }