Simplify base RV adapters using delegates (#630)

* Add delegate for BaseRvDiffAdapter

* Apply delegate for BaseRvAdapter and BaseRvPagingAdapter

* Fix list getting

* Replace TODO

* Remove casting

* Remove extra abstract functions

* Fix conflicts

* Move @Suppress("NotifyDataSetChanged")

* Tweak IMutableRvAdapterDelegate

* Better error message

* New IRvBindingAdapter

This reverts commit e4b069f.

* Rename IRvBindingAdapter

* Tweak RvAdapterDelegate

* Tweak ViewTypeDelegate

* Remove outdated TooManyFunctions

* Cleanups

* Use toPersistentList

* Rename

* Inline

* Tweak message

* Still use toImmutableList

* Add operator

* Cleanup

* Move refresh functions into delegate

* Tweak

* Move delegates into base interfaces

* Don't open BindingViewHolder

* Tweaks

* Suppress DELEGATED_MEMBER_HIDES_SUPERTYPE_OVERRIDE

* Tweak

* Remove redundant inline functions

* Use super.list

* Rearrange

* Move transformation into IMutableRvAdapter.Impl

* Better naming

adapter/src/main/kotlin/io/goooler/demoapp/adapter/rv/core/BaseRvAdapter.kt

@@ -1,9 +1,6 @@
 package io.goooler.demoapp.adapter.rv.core
 
-import android.view.ViewGroup
-import androidx.annotation.LayoutRes
 import androidx.recyclerview.widget.RecyclerView
-import kotlinx.collections.immutable.toImmutableList
 
 /**
  * Created on 2020/10/22.
@@ -14,62 +11,25 @@ import kotlinx.collections.immutable.toImmutableList
  * @version 1.0.0
  * @since 1.0.0
  */
-@Suppress("NotifyDataSetChanged", "TooManyFunctions")
-abstract class BaseRvAdapter<M : IVhModelType> :
-  RecyclerView.Adapter<BindingViewHolder>(),
-  IMutableRvAdapter<M> {
-
-  private val helper by lazy(LazyThreadSafetyMode.NONE) { RvAdapterHelper(this) }
-
-  override fun onAttachedToRecyclerView(recyclerView: RecyclerView) {
-    super.onAttachedToRecyclerView(recyclerView)
-    helper.onAttachedToRecyclerView(recyclerView)
-  }
-
-  override fun onDetachedFromRecyclerView(recyclerView: RecyclerView) {
-    super.onDetachedFromRecyclerView(recyclerView)
-    helper.onDetachedFromRecyclerView(recyclerView)
-  }
-
-  override fun onCreateViewHolder(parent: ViewGroup, @LayoutRes viewType: Int): BindingViewHolder =
-    helper.onCreateViewHolder(parent, viewType)
-
-  override fun onBindViewHolder(holder: BindingViewHolder, position: Int) {
-    helper.onBindViewHolder(holder, position)
-  }
-
-  override fun onBindViewHolder(
-    holder: BindingViewHolder,
-    position: Int,
-    payloads: List<Any>,
-  ) {
-    helper.onBindViewHolder(holder, position, payloads)
+@Suppress("DELEGATED_MEMBER_HIDES_SUPERTYPE_OVERRIDE")
+abstract class BaseRvAdapter<M : IVhModelType> private constructor(
+  private val delegate: IMutableRvAdapter.Impl<M, BaseRvAdapter<M>>,
+) : RecyclerView.Adapter<BindingViewHolder>(),
+  IRvBinding<M>,
+  IMutableRvAdapter<M> by delegate {
+
+  constructor() : this(IMutableRvAdapter.Impl()) {
+    @Suppress("LeakingThis")
+    delegate.adapter = this
   }
 
-  @LayoutRes
-  override fun getItemViewType(position: Int): Int =
-    helper.list[position].viewType
-
-  override fun getItemCount(): Int = helper.list.size
-
-  override operator fun get(position: Int): M = helper.list[position]
-
   override var list: List<M>
-    get() = helper.list.toImmutableList()
+    get() = delegate.list
     set(value) {
-      helper.list = value
+      delegate.list = value
+      @Suppress("NotifyDataSetChanged")
       notifyDataSetChanged()
     }
 
-  override fun refreshItems(items: List<M>) {
-    helper.refreshItems(items, ::notifyItemChanged)
-  }
-
-  override fun removeItem(index: Int) {
-    helper.removeItem(index, ::notifyItemRemoved)
-  }
-
-  override fun removeItem(item: M) {
-    helper.removeItem(item, ::notifyItemRemoved)
-  }
+  override fun getItemCount(): Int = delegate.list.size
 }

adapter/src/main/kotlin/io/goooler/demoapp/adapter/rv/core/BindingViewHolder.kt

@@ -1,5 +1,9 @@
 package io.goooler.demoapp.adapter.rv.core
 
+import android.view.LayoutInflater
+import android.view.ViewGroup
+import androidx.annotation.LayoutRes
+import androidx.databinding.DataBindingUtil
 import androidx.databinding.ViewDataBinding
 import androidx.recyclerview.widget.RecyclerView
 
@@ -12,4 +16,17 @@ import androidx.recyclerview.widget.RecyclerView
  * @version 1.0.0
  * @since 1.0.0
  */
-open class BindingViewHolder(val binding: ViewDataBinding) : RecyclerView.ViewHolder(binding.root)
+class BindingViewHolder(val binding: ViewDataBinding) : RecyclerView.ViewHolder(binding.root) {
+
+  companion object {
+    fun create(parent: ViewGroup, @LayoutRes viewType: Int): BindingViewHolder {
+      val binding = DataBindingUtil.inflate<ViewDataBinding>(
+        LayoutInflater.from(parent.context),
+        viewType,
+        parent,
+        false,
+      )
+      return BindingViewHolder(binding)
+    }
+  }
+}

adapter/src/main/kotlin/io/goooler/demoapp/adapter/rv/core/IRvAdapter.kt

@@ -1,12 +1,28 @@
 package io.goooler.demoapp.adapter.rv.core
 
-import android.view.LayoutInflater
 import android.view.ViewGroup
 import androidx.annotation.LayoutRes
 import androidx.databinding.BindingAdapter
-import androidx.databinding.DataBindingUtil
 import androidx.databinding.ViewDataBinding
+import androidx.recyclerview.widget.GridLayoutManager
 import androidx.recyclerview.widget.RecyclerView
+import androidx.recyclerview.widget.StaggeredGridLayoutManager
+import io.goooler.demoapp.adapter.rv.core.ISpanSize.Companion.SPAN_SIZE_FULL
+import kotlinx.collections.immutable.toImmutableList
+
+/**
+ * Keep the same signature as [RecyclerView.Adapter].
+ *
+ * Workaround for [KT-21955](https://youtrack.jetbrains.com/issue/KT-21955).
+ */
+internal interface RecyclerViewAdapter<VH : RecyclerView.ViewHolder> {
+  fun onAttachedToRecyclerView(recyclerView: RecyclerView)
+  fun onDetachedFromRecyclerView(recyclerView: RecyclerView)
+  fun onCreateViewHolder(parent: ViewGroup, viewType: Int): VH
+  fun onBindViewHolder(holder: BindingViewHolder, position: Int)
+  fun onBindViewHolder(holder: BindingViewHolder, position: Int, payloads: List<Any>)
+  fun getItemViewType(position: Int): Int
+}
 
 /**
  * Created on 2020/10/21.
@@ -17,13 +33,18 @@ import androidx.recyclerview.widget.RecyclerView
  * @version 1.0.0
  * @since 1.0.0
  */
-internal interface IRvAdapter<M : IVhModelType> {
+internal interface IRvAdapter<M : IVhModelType> : RecyclerViewAdapter<BindingViewHolder> {
 
   /**
    * Get data list.
    */
   val list: List<M>
 
+  /**
+   * Get item by position.
+   */
+  operator fun get(position: Int): M?
+
   /**
    * What to do when creating the viewHolder for all.
    */
@@ -34,28 +55,98 @@ internal interface IRvAdapter<M : IVhModelType> {
    */
   fun onBindVHForAll(binding: ViewDataBinding, model: M, payloads: List<Any>)
 
-  /**
-   * Create BaseViewHolder.
-   */
-  fun createVH(parent: ViewGroup, @LayoutRes viewType: Int): BindingViewHolder {
-    val binding = DataBindingUtil.inflate<ViewDataBinding>(
-      LayoutInflater.from(parent.context),
-      viewType,
-      parent,
-      false,
-    )
-    return BindingViewHolder(binding)
-  }
-
   /**
    * Init ViewTypeDelegateManager. You can add VTDs.
    */
   fun initManager(manager: ViewTypeDelegateManager<M>) {}
 
-  /**
-   * Get item by position.
-   */
-  operator fun get(position: Int): M?
+  @Suppress("TooManyFunctions")
+  open class Impl<M : IVhModelType, AP> : IRvAdapter<M>
+    where AP : IRvAdapter<M>,
+          AP : IRvBinding<M>,
+          AP : RecyclerView.Adapter<BindingViewHolder> {
+
+    private val ivdManager = ViewTypeDelegateManager<M>()
+
+    @Suppress("PropertyName", "VariableNaming", "ktlint:standard:backing-property-naming")
+    protected val _list = mutableListOf<M>()
+
+    lateinit var adapter: AP
+
+    override val list: List<M> get() = _list.toImmutableList()
+
+    override fun onAttachedToRecyclerView(recyclerView: RecyclerView) {
+      initManager(ivdManager)
+      fixSpanSize(recyclerView)
+    }
+
+    override fun onDetachedFromRecyclerView(recyclerView: RecyclerView) {
+      ivdManager.clear()
+      recyclerView.adapter = null
+    }
+
+    override operator fun get(position: Int): M = _list.getOrElse(position) {
+      // Override get in adapters as a fallback.
+      adapter[position] ?: error("No such a element in position $position in adapter $adapter.")
+    }
+
+    @LayoutRes
+    override fun getItemViewType(position: Int): Int = get(position).viewType
+
+    override fun onCreateViewHolder(
+      parent: ViewGroup,
+      @LayoutRes viewType: Int,
+    ): BindingViewHolder = BindingViewHolder.create(parent, viewType).also {
+      adapter.onCreateVHForAll(it.binding)
+      ivdManager.onCreateVH(it.binding, viewType)
+    }
+
+    override fun onBindViewHolder(holder: BindingViewHolder, position: Int) {
+      onBindViewHolder(holder, position, emptyList())
+    }
+
+    override fun onBindViewHolder(holder: BindingViewHolder, position: Int, payloads: List<Any>) {
+      get(position).let {
+        setFullSpan(holder, it)
+        adapter.onBindVHForAll(holder.binding, it, payloads)
+        ivdManager.onBindVH(holder.binding, it, payloads)
+        holder.binding.executePendingBindings()
+      }
+    }
+
+    override fun onCreateVHForAll(binding: ViewDataBinding) {
+      adapter.onCreateVH(binding)
+    }
+
+    override fun onBindVHForAll(binding: ViewDataBinding, model: M, payloads: List<Any>) {
+      adapter.onBindVH(binding, model, payloads)
+    }
+
+    /**
+     * Fix span size when recyclerView's layoutManager is [GridLayoutManager].
+     */
+    private fun fixSpanSize(recyclerView: RecyclerView) {
+      (recyclerView.layoutManager as? GridLayoutManager)?.let {
+        it.spanSizeLookup = object : GridLayoutManager.SpanSizeLookup() {
+          override fun getSpanSize(position: Int): Int {
+            (get(position) as? ISpanSize)?.spanSize?.let { size ->
+              return if (size == SPAN_SIZE_FULL) it.spanCount else size
+            }
+            return it.spanCount
+          }
+        }
+      }
+    }
+
+    /**
+     * Set full span when recyclerView's layoutManager is [StaggeredGridLayoutManager].
+     */
+    private fun setFullSpan(holder: RecyclerView.ViewHolder, item: M) {
+      (holder.itemView.layoutParams as? StaggeredGridLayoutManager.LayoutParams)?.let {
+        it.isFullSpan = (item as? ISpanSize)?.spanSize == SPAN_SIZE_FULL
+      }
+    }
+  }
 }
 
 internal interface IMutableRvAdapter<M : IVhModelType> : IRvAdapter<M> {
@@ -73,6 +164,57 @@ internal interface IMutableRvAdapter<M : IVhModelType> : IRvAdapter<M> {
   fun removeItem(index: Int)
 
   fun removeItem(item: M)
+
+  class Impl<M : IVhModelType, AP> :
+    IRvAdapter.Impl<M, AP>(),
+    IMutableRvAdapter<M>
+    where AP : IRvAdapter<M>,
+          AP : IRvBinding<M>,
+          AP : RecyclerView.Adapter<BindingViewHolder> {
+
+    override var list: List<M>
+      get() = super.list
+      set(value) {
+        _list.clear()
+        _list.addAll(flat(value))
+      }
+
+    override fun refreshItems(items: List<M>) {
+      flat(items).forEach {
+        if (it in _list) {
+          adapter.notifyItemChanged(_list.indexOf(it))
+        }
+      }
+    }
+
+    override fun removeItem(index: Int) {
+      _list.removeAt(index)
+      adapter::notifyItemRemoved
+    }
+
+    override fun removeItem(item: M) {
+      _list.indexOf(item).takeIf { it != -1 }?.let {
+        removeItem(it)
+        adapter::notifyItemRemoved
+      }
+    }
+
+    private fun flat(original: List<M>): List<M> {
+      val result = mutableListOf<M>()
+      original.forEach { findLeaf(it, result) }
+      return result
+    }
+
+    private fun findLeaf(model: M, list: MutableList<M>) {
+      if (model is IVhModelWrapper<*>) {
+        if (model.viewType != -1) list += model
+        @Suppress("UNCHECKED_CAST")
+        model.subList.forEach { findLeaf(it as M, list) }
+      } else {
+        list += model
+      }
+    }
+  }
 }
 
 @BindingAdapter("binding_rv_dataList")

adapter/src/main/kotlin/io/goooler/demoapp/adapter/rv/core/IRvBinding.kt

@@ -0,0 +1,21 @@
+package io.goooler.demoapp.adapter.rv.core
+
+import androidx.databinding.ViewDataBinding
+
+interface IRvBinding<M : IVhModelType> {
+
+  /**
+   * What to do when creating the viewHolder.
+   *
+   * @param binding ViewDataBinding
+   */
+  fun onCreateVH(binding: ViewDataBinding)
+
+  /**
+   * What to do when binding the viewHolder.
+   *
+   * @param binding ViewDataBinding
+   * @param model model
+   */
+  fun onBindVH(binding: ViewDataBinding, model: M, payloads: List<Any>)
+}