For #1104 - Adds SectionedAdapter

app/src/main/java/org/mozilla/fenix/components/SectionedAdapter.kt

@@ -0,0 +1,76 @@
+package org.mozilla.fenix.components
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import android.view.ViewGroup
+import androidx.recyclerview.widget.RecyclerView
+import java.lang.IllegalStateException
+
+abstract class SectionedAdapter : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
+    sealed class SectionType {
+        data class Header(val index: Int) : SectionType()
+        data class Row(val section: Int, val row: Int) : SectionType()
+
+        val viewType: Int
+            get() = when (this) {
+                is Header -> HeaderViewType
+                is Row -> RowViewType
+            }
+
+        companion object {
+            const val HeaderViewType = 0
+            const val RowViewType = 1
+        }
+    }
+
+    abstract fun numberOfSections(): Int
+    abstract fun numberOfRowsInSection(section: Int): Int
+
+    abstract fun onCreateHeaderViewHolder(parent: ViewGroup): RecyclerView.ViewHolder
+    abstract fun onBindHeaderViewHolder(holder: RecyclerView.ViewHolder, header: SectionType.Header)
+    abstract fun onCreateItemViewHolder(parent: ViewGroup): RecyclerView.ViewHolder
+    abstract fun onBindItemViewHolder(holder: RecyclerView.ViewHolder, row: SectionType.Row)
+
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
+        return when  (viewType) {
+            SectionType.HeaderViewType -> onCreateHeaderViewHolder(parent)
+            SectionType.RowViewType -> onCreateItemViewHolder(parent)
+            else -> throw IllegalStateException("ViewType: $viewType is invalid ")
+        }
+    }
+
+    override fun getItemViewType(position: Int): Int {
+        return sectionTypeForPosition(position).viewType
+    }
+
+    override fun getItemCount(): Int {
+        val numberOfSections = numberOfSections()
+        return numberOfSections + (0..numberOfSections).reduce { a, b -> a + numberOfRowsInSection(b) }
+    }
+
+    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
+        val sectionType = sectionTypeForPosition(position)
+
+        when (sectionType) {
+            is SectionType.Header -> onBindHeaderViewHolder(holder, sectionType)
+            is SectionType.Row -> onBindItemViewHolder(holder, sectionType)
+        }
+    }
+
+    private fun sectionTypeForPosition(position: Int): SectionType {
+        var counter = 0
+
+        for (section in 0..numberOfSections()) {
+            if (counter == position) { return SectionType.Header(section) }
+            counter += 1
+
+            for (row in 0..numberOfRowsInSection(section)) {
+                if (counter == position) { return SectionType.Row(section, row) }
+                counter += 1
+            }
+        }
+    }
+}