Update to Android gradle plugin 4.1.0; increase target SDK level to 30; update BatchOperation to new API definition

4 files changed, 175 insertions, 189 deletions

diff --git a/build.gradle b/build.gradle
index 78f914a..981d36f 100644
--- a/build.gradle
+++ b/build.gradle
@@ -14,7 +14,7 @@ buildscript {
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:4.0.1'
+        classpath 'com.android.tools.build:gradle:4.1.0'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:${versions.kotlin}"
         classpath "org.jetbrains.dokka:dokka-gradle-plugin:${versions.dokka}"
     }
@@ -30,12 +30,12 @@ apply plugin: 'kotlin-android'
 apply plugin: 'org.jetbrains.dokka'
 
 android {
-    compileSdkVersion 29
+    compileSdkVersion 30
     buildToolsVersion '30.0.2'
 
     defaultConfig {
         minSdkVersion 16        // Android 4.1
-        targetSdkVersion 29     // Android 10
+        targetSdkVersion 30     // Android 11
     }
 
     compileOptions {
@@ -81,7 +81,7 @@ dependencies {
     // noinspection GradleDependency
     implementation "org.apache.commons:commons-text:${versions.commonsText}"
 
-    // ez-vcard to parse/generate VCards
+    // ez-vcard to parse/generate vCards
     api('com.googlecode.ez-vcard:ez-vcard:0.11.0') {
         // hCard functionality not needed
         exclude group: 'org.jsoup'
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 1e2b225..d042ef0 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.3-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.6.1-all.zip
diff --git a/src/main/java/at/bitfire/vcard4android/AndroidContact.kt b/src/main/java/at/bitfire/vcard4android/AndroidContact.kt
index 98bc509..8ab9a32 100644
--- a/src/main/java/at/bitfire/vcard4android/AndroidContact.kt
+++ b/src/main/java/at/bitfire/vcard4android/AndroidContact.kt
@@ -8,7 +8,6 @@
 
 package at.bitfire.vcard4android
 
-import android.content.ContentProviderOperation
 import android.content.ContentUris
 import android.content.ContentValues
 import android.content.EntityIterator
@@ -549,20 +548,20 @@ open class AndroidContact(
     fun add(): Uri {
         val batch = BatchOperation(addressBook.provider!!)
 
-        val builder = ContentProviderOperation.newInsert(addressBook.syncAdapterURI(RawContacts.CONTENT_URI))
+        val builder = BatchOperation.CpoBuilder.newInsert(addressBook.syncAdapterURI(RawContacts.CONTENT_URI))
         buildContact(builder, false)
-        batch.enqueue(BatchOperation.Operation(builder))
+        batch.enqueue(builder)
 
         insertDataRows(batch)
 
         batch.commit()
-        val result = batch.getResult(0) ?: throw ContactsStorageException("Empty result from content provider when adding contact")
-        id = ContentUris.parseId(result.uri)
+        val resultUri = batch.getResult(0)?.uri ?: throw ContactsStorageException("Empty result from content provider when adding contact")
+        id = ContentUris.parseId(resultUri)
 
         // we need a raw contact ID to insert the photo
         insertPhoto(contact!!.photo)
 
-        return result.uri
+        return resultUri
     }
 
     fun update(contact: Contact): Uri {
@@ -570,16 +569,16 @@ open class AndroidContact(
 
         val batch = BatchOperation(addressBook.provider!!)
         val uri = rawContactSyncURI()
-        val builder = ContentProviderOperation.newUpdate(uri)
+        val builder = BatchOperation.CpoBuilder.newUpdate(uri)
         buildContact(builder, true)
-        batch.enqueue(BatchOperation.Operation(builder))
+        batch.enqueue(builder)
 
         // Delete known data rows before adding the new ones.
         // - We don't delete group memberships.
         // - We'll only delete rows we have inserted so that unknown rows like
         //   vnd.android.cursor.item/important_people (= contact is in Samsung "edge panel") remain untouched.
-        batch.enqueue(BatchOperation.Operation(
-                ContentProviderOperation.newDelete(dataSyncURI())
+        batch.enqueue(BatchOperation.CpoBuilder
+                .newDelete(dataSyncURI())
                 .withSelection(Data.RAW_CONTACT_ID + "=? AND " +
                         Data.MIMETYPE + " IN (?,?,?,?,?,?,?,?,?,?,?,?,?)",
                         arrayOf(id.toString(),
@@ -596,7 +595,7 @@ open class AndroidContact(
                                 Event.CONTENT_ITEM_TYPE,
                                 Relation.CONTENT_ITEM_TYPE,
                                 SipAddress.CONTENT_ITEM_TYPE))
-        ))
+        )
         insertDataRows(batch)
         batch.commit()
 
@@ -609,7 +608,7 @@ open class AndroidContact(
 
 
     @CallSuper
-    protected open fun buildContact(builder: ContentProviderOperation.Builder, update: Boolean) {
+    protected open fun buildContact(builder: BatchOperation.CpoBuilder, update: Boolean) {
         if (!update)
             builder	.withValue(RawContacts.ACCOUNT_NAME, addressBook.account.name)
                     .withValue(RawContacts.ACCOUNT_TYPE, addressBook.account.type)
@@ -664,15 +663,8 @@ open class AndroidContact(
                 contact.phoneticGivenName == null && contact.phoneticMiddleName == null && contact.phoneticFamilyName == null)
             return
 
-        val op: BatchOperation.Operation
-        val builder = ContentProviderOperation.newInsert(dataSyncURI())
-        if (id == null)
-            op = BatchOperation.Operation(builder, StructuredName.RAW_CONTACT_ID, 0)
-        else {
-            op = BatchOperation.Operation(builder)
-            builder.withValue(StructuredName.RAW_CONTACT_ID, id)
-        }
-        builder .withValue(Data.MIMETYPE, StructuredName.CONTENT_ITEM_TYPE)
+        val builder = insertDataBuilder(StructuredName.RAW_CONTACT_ID)
+                .withValue(Data.MIMETYPE, StructuredName.CONTENT_ITEM_TYPE)
                 .withValue(StructuredName.DISPLAY_NAME, contact.displayName)
                 .withValue(StructuredName.PREFIX, contact.prefix)
                 .withValue(StructuredName.GIVEN_NAME, contact.givenName)
@@ -683,11 +675,8 @@ open class AndroidContact(
                 .withValue(StructuredName.PHONETIC_MIDDLE_NAME, contact.phoneticMiddleName)
                 .withValue(StructuredName.PHONETIC_FAMILY_NAME, contact.phoneticFamilyName)
 
-        if (addressBook.readOnly)
-            builder.withValue(Data.IS_READ_ONLY, 1)
-
         Constants.log.log(Level.FINER, "Built StructuredName data row", builder.build())
-        batch.enqueue(op)
+        batch.enqueue(builder)
     }
 
     protected open fun insertPhoneNumber(batch: BatchOperation, labeledNumber: LabeledProperty<Telephone>) {
@@ -765,26 +754,16 @@ open class AndroidContact(
             }
         }
 
-        val op: BatchOperation.Operation
-        val builder = ContentProviderOperation.newInsert(dataSyncURI())
-        if (id == null)
-            op = BatchOperation.Operation(builder, Phone.RAW_CONTACT_ID, 0)
-        else {
-            op = BatchOperation.Operation(builder)
-            builder.withValue(Phone.RAW_CONTACT_ID, id)
-        }
-        builder	.withValue(Phone.MIMETYPE, Phone.CONTENT_ITEM_TYPE)
+        val builder = insertDataBuilder(Phone.RAW_CONTACT_ID)
+                .withValue(Phone.MIMETYPE, Phone.CONTENT_ITEM_TYPE)
                 .withValue(Phone.NUMBER, number.text)
                 .withValue(Phone.TYPE, typeCode)
                 .withValue(Phone.LABEL, typeLabel)
                 .withValue(Phone.IS_PRIMARY, if (isPrimary) 1 else 0)
                 .withValue(Phone.IS_SUPER_PRIMARY, if (isPrimary) 1 else 0)
 
-        if (addressBook.readOnly)
-            builder.withValue(Data.IS_READ_ONLY, 1)
-
         Constants.log.log(Level.FINER, "Built Phone data row", builder.build())
-        batch.enqueue(op)
+        batch.enqueue(builder)
     }
 
     protected open fun insertEmail(batch: BatchOperation, labeledEmail: LabeledProperty<ezvcard.property.Email>) {
@@ -830,26 +809,16 @@ open class AndroidContact(
             }
         }
 
-        val op: BatchOperation.Operation
-        val builder = ContentProviderOperation.newInsert(dataSyncURI())
-        if (id == null)
-            op = BatchOperation.Operation(builder, Email.RAW_CONTACT_ID, 0)
-        else {
-            op = BatchOperation.Operation(builder)
-            builder.withValue(Email.RAW_CONTACT_ID, id)
-        }
-        builder	.withValue(Email.MIMETYPE, Email.CONTENT_ITEM_TYPE)
+        val builder = insertDataBuilder(Email.RAW_CONTACT_ID)
+                .withValue(Email.MIMETYPE, Email.CONTENT_ITEM_TYPE)
                 .withValue(Email.ADDRESS, email.value)
                 .withValue(Email.TYPE, typeCode)
                 .withValue(Email.LABEL, typeLabel)
                 .withValue(Email.IS_PRIMARY, if (isPrimary) 1 else 0)
                 .withValue(Phone.IS_SUPER_PRIMARY, if (isPrimary) 1 else 0)
 
-        if (addressBook.readOnly)
-            builder.withValue(Data.IS_READ_ONLY, 1)
-
         Constants.log.log(Level.FINER, "Built Email data row", builder.build())
-        batch.enqueue(op)
+        batch.enqueue(builder)
     }
 
     protected open fun insertOrganization(batch: BatchOperation) {
@@ -868,25 +837,15 @@ open class AndroidContact(
                 department = org.next()
         }
 
-        val op: BatchOperation.Operation
-        val builder = ContentProviderOperation.newInsert(dataSyncURI())
-        if (id == null)
-            op = BatchOperation.Operation(builder, Organization.RAW_CONTACT_ID, 0)
-        else {
-            op = BatchOperation.Operation(builder)
-            builder.withValue(Organization.RAW_CONTACT_ID, id)
-        }
-        builder .withValue(Organization.MIMETYPE, Organization.CONTENT_ITEM_TYPE)
+        val builder = insertDataBuilder(Organization.RAW_CONTACT_ID)
+                .withValue(Organization.MIMETYPE, Organization.CONTENT_ITEM_TYPE)
                 .withValue(Organization.COMPANY, company)
                 .withValue(Organization.DEPARTMENT, department)
                 .withValue(Organization.TITLE, contact.jobTitle)
                 .withValue(Organization.JOB_DESCRIPTION, contact.jobDescription)
 
-        if (addressBook.readOnly)
-            builder.withValue(Data.IS_READ_ONLY, 1)
-
         Constants.log.log(Level.FINER, "Built Organization data row", builder.build())
-        batch.enqueue(op)
+        batch.enqueue(builder)
     }
 
     protected open fun insertIMPP(batch: BatchOperation, labeledImpp: LabeledProperty<Impp>) {
@@ -940,28 +899,19 @@ open class AndroidContact(
             }
         }
 
-        val op: BatchOperation.Operation
-        val builder = ContentProviderOperation.newInsert(dataSyncURI())
-        if (id == null)
-            op = BatchOperation.Operation(builder, Im.RAW_CONTACT_ID, 0)
-        else {
-            op = BatchOperation.Operation(builder)
-            builder.withValue(Im.RAW_CONTACT_ID, id)
-        }
-
-        if (addressBook.readOnly)
-            builder.withValue(Data.IS_READ_ONLY, 1)
-
+        val builder: BatchOperation.CpoBuilder
         if (sipAddress) {
             // save as SIP address
-            builder .withValue(SipAddress.MIMETYPE, SipAddress.CONTENT_ITEM_TYPE)
+            builder = insertDataBuilder(SipAddress.RAW_CONTACT_ID)
+                    .withValue(SipAddress.MIMETYPE, SipAddress.CONTENT_ITEM_TYPE)
                     .withValue(SipAddress.DATA, impp.handle)
                     .withValue(SipAddress.TYPE, typeCode)
                     .withValue(SipAddress.LABEL, typeLabel)
             Constants.log.log(Level.FINER, "Built SipAddress data row", builder.build())
         } else {
             // save as IM address
-            builder	.withValue(Im.MIMETYPE, Im.CONTENT_ITEM_TYPE)
+            builder = insertDataBuilder(Im.RAW_CONTACT_ID)
+                    .withValue(Im.MIMETYPE, Im.CONTENT_ITEM_TYPE)
                     .withValue(Im.DATA, impp.handle)
                     .withValue(Im.TYPE, typeCode)
                     .withValue(Im.LABEL, typeLabel)
@@ -969,7 +919,7 @@ open class AndroidContact(
                     .withValue(Im.CUSTOM_PROTOCOL, protocolLabel)
             Constants.log.log(Level.FINER, "Built Im data row", builder.build())
         }
-        batch.enqueue(op)
+        batch.enqueue(builder)
     }
 
     protected open fun insertNickname(batch: BatchOperation) {
@@ -993,24 +943,14 @@ open class AndroidContact(
             }
         }
 
-        val op: BatchOperation.Operation
-        val builder = ContentProviderOperation.newInsert(dataSyncURI())
-        if (id == null)
-            op = BatchOperation.Operation(builder, Nickname.RAW_CONTACT_ID, 0)
-        else {
-            op = BatchOperation.Operation(builder)
-            builder.withValue(Nickname.RAW_CONTACT_ID, id)
-        }
-        builder .withValue(Nickname.MIMETYPE, Nickname.CONTENT_ITEM_TYPE)
+        val builder = insertDataBuilder(Nickname.RAW_CONTACT_ID)
+                .withValue(Nickname.MIMETYPE, Nickname.CONTENT_ITEM_TYPE)
                 .withValue(Nickname.NAME, nick.values.first())
                 .withValue(Nickname.TYPE, typeCode)
                 .withValue(Nickname.LABEL, typeLabel)
 
-        if (addressBook.readOnly)
-            builder.withValue(Data.IS_READ_ONLY, 1)
-
         Constants.log.log(Level.FINER, "Built Nickname data row", builder.build())
-        batch.enqueue(op)
+        batch.enqueue(builder)
     }
 
     protected open fun insertNote(batch: BatchOperation) {
@@ -1018,22 +958,12 @@ open class AndroidContact(
         if (contact.note.isNullOrEmpty())
             return
 
-        val op: BatchOperation.Operation
-        val builder = ContentProviderOperation.newInsert(dataSyncURI())
-        if (id == null)
-            op = BatchOperation.Operation(builder, Note.RAW_CONTACT_ID, 0)
-        else {
-            op = BatchOperation.Operation(builder)
-            builder.withValue(Note.RAW_CONTACT_ID, id)
-        }
-        builder .withValue(Note.MIMETYPE, Note.CONTENT_ITEM_TYPE)
+        val builder = insertDataBuilder(Note.RAW_CONTACT_ID)
+                .withValue(Note.MIMETYPE, Note.CONTENT_ITEM_TYPE)
                 .withValue(Note.NOTE, contact.note)
 
-        if (addressBook.readOnly)
-            builder.withValue(Data.IS_READ_ONLY, 1)
-
         Constants.log.log(Level.FINER, "Built Note data row", builder.build())
-        batch.enqueue(op)
+        batch.enqueue(builder)
     }
 
     protected open fun insertStructuredPostal(batch: BatchOperation, labeledAddress: LabeledProperty<Address>) {
@@ -1083,15 +1013,8 @@ open class AndroidContact(
             }
         }
 
-        val op: BatchOperation.Operation
-        val builder = ContentProviderOperation.newInsert(dataSyncURI())
-        if (id == null)
-            op = BatchOperation.Operation(builder, StructuredPostal.RAW_CONTACT_ID, 0)
-        else {
-            op = BatchOperation.Operation(builder)
-            builder.withValue(StructuredPostal.RAW_CONTACT_ID, id)
-        }
-        builder .withValue(StructuredPostal.MIMETYPE, StructuredPostal.CONTENT_ITEM_TYPE)
+        val builder = insertDataBuilder(StructuredPostal.RAW_CONTACT_ID)
+                .withValue(StructuredPostal.MIMETYPE, StructuredPostal.CONTENT_ITEM_TYPE)
                 .withValue(StructuredPostal.FORMATTED_ADDRESS, formattedAddress)
                 .withValue(StructuredPostal.TYPE, typeCode)
                 .withValue(StructuredPostal.LABEL, typeLabel)
@@ -1103,11 +1026,8 @@ open class AndroidContact(
                 .withValue(StructuredPostal.POSTCODE, address.postalCode)
                 .withValue(StructuredPostal.COUNTRY, address.country)
 
-        if (addressBook.readOnly)
-            builder.withValue(Data.IS_READ_ONLY, 1)
-
         Constants.log.log(Level.FINER, "Built StructuredPostal data row", builder.build())
-        batch.enqueue(op)
+        batch.enqueue(builder)
     }
 
     protected open fun insertWebsite(batch: BatchOperation, labeledUrl: LabeledProperty<Url>) {
@@ -1135,24 +1055,14 @@ open class AndroidContact(
             }
         }
 
-        val op: BatchOperation.Operation
-        val builder = ContentProviderOperation.newInsert(dataSyncURI())
-        if (id == null)
-            op = BatchOperation.Operation(builder, Website.RAW_CONTACT_ID, 0)
-        else {
-            op = BatchOperation.Operation(builder)
-            builder.withValue(Website.RAW_CONTACT_ID, id)
-        }
-        builder .withValue(Website.MIMETYPE, Website.CONTENT_ITEM_TYPE)
+        val builder = insertDataBuilder(Website.RAW_CONTACT_ID)
+                .withValue(Website.MIMETYPE, Website.CONTENT_ITEM_TYPE)
                 .withValue(Website.URL, url.value)
                 .withValue(Website.TYPE, typeCode)
                 .withValue(Website.LABEL, typeLabel)
 
-        if (addressBook.readOnly)
-            builder.withValue(Data.IS_READ_ONLY, 1)
-
         Constants.log.log(Level.FINER, "Built Website data row", builder.build())
-        batch.enqueue(op)
+        batch.enqueue(builder)
     }
 
     protected open fun insertEvent(batch: BatchOperation, type: Int, dateOrTime: DateOrTimeProperty) {
@@ -1170,23 +1080,13 @@ open class AndroidContact(
             }
         }
 
-        val op: BatchOperation.Operation
-        val builder = ContentProviderOperation.newInsert(dataSyncURI())
-        if (id == null)
-            op = BatchOperation.Operation(builder, Event.RAW_CONTACT_ID, 0)
-        else {
-            op = BatchOperation.Operation(builder)
-            builder.withValue(Event.RAW_CONTACT_ID, id)
-        }
-        builder .withValue(Event.MIMETYPE, Event.CONTENT_ITEM_TYPE)
+        val builder = insertDataBuilder(Event.RAW_CONTACT_ID)
+                .withValue(Event.MIMETYPE, Event.CONTENT_ITEM_TYPE)
                 .withValue(Event.TYPE, type)
                 .withValue(Event.START_DATE, dateStr)
 
-        if (addressBook.readOnly)
-            builder.withValue(Data.IS_READ_ONLY, 1)
-
-        batch.enqueue(op)
         Constants.log.log(Level.FINER, "Built Event data row", builder.build())
+        batch.enqueue(builder)
     }
 
     protected open fun insertRelation(batch: BatchOperation, related: Related) {
@@ -1206,24 +1106,14 @@ open class AndroidContact(
                 else               -> labels += type.value
             }
 
-        val op: BatchOperation.Operation
-        val builder = ContentProviderOperation.newInsert(dataSyncURI())
-        if (id == null)
-            op = BatchOperation.Operation(builder, Relation.RAW_CONTACT_ID, 0)
-        else {
-            op = BatchOperation.Operation(builder)
-            builder.withValue(Relation.RAW_CONTACT_ID, id)
-        }
-        builder .withValue(Relation.MIMETYPE, Relation.CONTENT_ITEM_TYPE)
+        val builder = insertDataBuilder(Relation.RAW_CONTACT_ID)
+                .withValue(Relation.MIMETYPE, Relation.CONTENT_ITEM_TYPE)
                 .withValue(Relation.NAME, related.text)
                 .withValue(Relation.TYPE, typeCode)
                 .withValue(Relation.LABEL, StringUtils.trimToNull(labels.joinToString(", ")))
 
-        if (addressBook.readOnly)
-            builder.withValue(Data.IS_READ_ONLY, 1)
-
         Constants.log.log(Level.FINER, "Built Relation data row", builder.build())
-        batch.enqueue(op)
+        batch.enqueue(builder)
     }
 
     protected open fun insertPhoto(orig: ByteArray?) {
@@ -1307,6 +1197,19 @@ open class AndroidContact(
 
     // helpers
 
+    protected fun insertDataBuilder(rawContactKeyName: String): BatchOperation.CpoBuilder {
+        val builder = BatchOperation.CpoBuilder.newInsert(dataSyncURI())
+        if (id == null)
+            builder.withValueBackReference(rawContactKeyName, 0)
+        else
+            builder.withValue(rawContactKeyName, id)
+
+        if (addressBook.readOnly)
+            builder.withValue(Data.IS_READ_ONLY, 1)
+
+        return builder
+    }
+
     protected open fun queryPhotoMaxDimensions(): Int {
         try {
             addressBook.provider?.query(ContactsContract.DisplayPhoto.CONTENT_MAX_DIMENSIONS_URI,
diff --git a/src/main/java/at/bitfire/vcard4android/BatchOperation.kt b/src/main/java/at/bitfire/vcard4android/BatchOperation.kt
index da09a35..8228230 100644
--- a/src/main/java/at/bitfire/vcard4android/BatchOperation.kt
+++ b/src/main/java/at/bitfire/vcard4android/BatchOperation.kt
@@ -9,6 +9,7 @@
 package at.bitfire.vcard4android
 
 import android.content.*
+import android.net.Uri
 import android.os.RemoteException
 import android.os.TransactionTooLargeException
 import java.util.*
@@ -17,13 +18,24 @@ class BatchOperation(
         private val providerClient: ContentProviderClient
 ) {
 
-    private val queue = LinkedList<Operation>()
+    companion object {
+
+        /**
+         * See https://android.googlesource.com/platform/packages/providers/ContactsProvider.git/+/refs/heads/android11-release/src/com/android/providers/contacts/AbstractContactsProvider.java#70
+         *
+         * Some operations may count more than one operation, so use a safe value of 450 instead of 500.
+         */
+        const val MAX_OPERATIONS_PER_YIELD_POINT = 450
+
+    }
+
+    private val queue = LinkedList<CpoBuilder>()
     private var results = arrayOfNulls<ContentProviderResult?>(0)
 
 
     fun nextBackrefIdx() = queue.size
 
-    fun enqueue(operation: Operation) = queue.add(operation)
+    fun enqueue(operation: CpoBuilder) = queue.add(operation)
 
     fun commit(): Int {
         var affected = 0
@@ -36,7 +48,7 @@ class BatchOperation(
 
                 for (result in results.filterNotNull())
                     when {
-                        result.count != null -> affected += result.count
+                        result.count != null -> affected += result.count ?: 0
                         result.uri != null   -> affected += 1
                     }
                 Constants.log.fine("… $affected record(s) affected")
@@ -57,9 +69,9 @@ class BatchOperation(
      * Catches [TransactionTooLargeException] and splits the operations accordingly.
      * @param start index of first operation which will be run (inclusive)
      * @param end   index of last operation which will be run (exclusive!)
-     * @throws RemoteException on contact provider errors
+     * @throws RemoteException on calendar provider errors
      * @throws OperationApplicationException when the batch can't be processed
-     * @throws ContactsStorageException if the transaction is too large
+     * @throws CalendarStorageException if the transaction is too large
      */
     private fun runBatch(start: Int, end: Int) {
         if (end == start)
@@ -90,34 +102,105 @@ class BatchOperation(
     private fun toCPO(start: Int, end: Int): ArrayList<ContentProviderOperation> {
         val cpo = ArrayList<ContentProviderOperation>(end - start)
 
-        for ((i, op) in queue.subList(start, end).withIndex()) {
-            val builder = op.builder
-            op.backrefKey?.let { key ->
-                if (op.backrefIdx < start)
-                    // back reference is outside of the current batch
-                    results[op.backrefIdx]?.let { result ->
-                        builder .withValueBackReferences(null)
-                                .withValue(key, ContentUris.parseId(result.uri))
-                    }
-                else
-                    // back reference is in current batch, apply offset
-                    builder.withValueBackReference(key, op.backrefIdx - start)
+        for ((i, cpoBuilder) in queue.subList(start, end).withIndex()) {
+            for ((backrefKey, backrefIdx) in cpoBuilder.valueBackrefs) {
+                if (backrefIdx < start) {
+                    // back reference is outside of the current batch, get result from previous execution ...
+                    val resultUri = results[backrefIdx]?.uri ?: throw ContactsStorageException("Referenced operation didn't produce a valid result")
+                    val resultId = ContentUris.parseId(resultUri)
+                    // ... and use result directly instead of using a back reference
+                    cpoBuilder  .removeValueBackReference(backrefKey)
+                                .withValue(backrefKey, resultId)
+                } else
+                    // back reference is in current batch, shift index
+                    cpoBuilder.withValueBackReference(backrefKey, backrefIdx - start)
             }
 
-            // set a yield point at least every 300 operations
-            if (i % 300 == 0)
-                builder.withYieldAllowed(true)
+            if (i % MAX_OPERATIONS_PER_YIELD_POINT == MAX_OPERATIONS_PER_YIELD_POINT - 1)
+                cpoBuilder.yieldAllowed = true
 
-            cpo += builder.build()
+            cpo += cpoBuilder.build()
         }
         return cpo
     }
 
 
-    class Operation constructor(
-            val builder: ContentProviderOperation.Builder,
-            val backrefKey: String? = null,
-            val backrefIdx: Int = -1
-    )
+    /**
+     * Wrapper for [ContentProviderOperation.Builder] that allows to reset previously-set
+     * value back references.
+     */
+    class CpoBuilder private constructor(
+            val uri: Uri,
+            val type: Type
+    ) {
+
+        enum class Type { INSERT, UPDATE, DELETE }
+
+        companion object {
+
+            fun newInsert(uri: Uri) = CpoBuilder(uri, Type.INSERT)
+            fun newUpdate(uri: Uri) = CpoBuilder(uri, Type.UPDATE)
+            fun newDelete(uri: Uri) = CpoBuilder(uri, Type.DELETE)
+
+        }
+
+
+        var selection: String? = null
+        var selectionArguments: Array<String>? = null
+
+        val values = mutableMapOf<String, Any>()
+        val valueBackrefs = mutableMapOf<String, Int>()
+
+        var yieldAllowed = false
+
+
+        fun withSelection(select: String, args: Array<String>): CpoBuilder {
+            selection = select
+            selectionArguments = args
+            return this
+        }
+
+        fun withValueBackReference(key: String, index: Int): CpoBuilder {
+            valueBackrefs[key] = index
+            return this
+        }
+
+        fun removeValueBackReference(key: String): CpoBuilder {
+            if (valueBackrefs.remove(key) == null)
+                throw IllegalArgumentException("$key was not set as value back reference")
+            return this
+        }
+
+        fun withValue(key: String, value: Any?): CpoBuilder {
+            if (value != null)
+                values[key] = value
+            else
+                values -= key
+            return this
+        }
+
+
+        fun build(): ContentProviderOperation {
+            val builder = when (type) {
+                Type.INSERT -> ContentProviderOperation.newInsert(uri)
+                Type.UPDATE -> ContentProviderOperation.newUpdate(uri)
+                Type.DELETE -> ContentProviderOperation.newDelete(uri)
+            }
+
+            if (selection != null)
+                builder.withSelection(selection, selectionArguments)
+
+            for ((key, value) in values)
+                builder.withValue(key, value)
+            for ((key, index) in valueBackrefs)
+                builder.withValueBackReference(key, index)
+
+            if (yieldAllowed)
+                builder.withYieldAllowed(true)
+
+            return builder.build()
+        }
+
+    }
 
-}
+}
\ No newline at end of file