Create `AdapterWithHeader` wrapper adapter

2 files changed, 119 insertions, 0 deletions

diff --git a/android/src/main/kotlin/net/mullvad/mullvadvpn/util/AdapterWithHeader.kt b/android/src/main/kotlin/net/mullvad/mullvadvpn/util/AdapterWithHeader.kt
new file mode 100644
index 0000000000..0cddaaa123
--- /dev/null
+++ b/android/src/main/kotlin/net/mullvad/mullvadvpn/util/AdapterWithHeader.kt
@@ -0,0 +1,110 @@
+package net.mullvad.mullvadvpn.util
+
+import android.support.v7.widget.RecyclerView.Adapter
+import android.support.v7.widget.RecyclerView.AdapterDataObserver
+import android.support.v7.widget.RecyclerView.ViewHolder
+import android.view.LayoutInflater
+import android.view.ViewGroup
+
+class AdapterWithHeader<H : ViewHolder>(
+    val adapter: Adapter<H>,
+    val headerLayoutId: Int
+) : Adapter<HeaderOrHolder<H>>() {
+    private val observer = object : AdapterDataObserver() {
+        override fun onChanged() {
+            notifyDataSetChanged()
+        }
+
+        override fun onItemRangeChanged(start: Int, count: Int) {
+            notifyItemRangeChanged(start + 1, count)
+        }
+
+        override fun onItemRangeChanged(start: Int, count: Int, payload: Any?) {
+            notifyItemRangeChanged(start + 1, count, payload)
+        }
+
+        override fun onItemRangeInserted(start: Int, count: Int) {
+            notifyItemRangeInserted(start + 1, count)
+        }
+
+        override fun onItemRangeMoved(from: Int, to: Int, count: Int) {
+            if (from == to) {
+                notifyItemRangeChanged(from + 1, count)
+            } else {
+                val sourceStart = from + 1
+                val sourceEnd = sourceStart + count
+                val destinationStart = to + 1
+                val destinationEnd = destinationStart + count
+
+                val ascendingIndices =
+                    (sourceStart..sourceEnd).zip(destinationStart..destinationEnd)
+
+                val indices = if (from < to) {
+                    ascendingIndices.asReversed()
+                } else {
+                    ascendingIndices
+                }
+
+                for ((source, destination) in indices) {
+                    notifyItemMoved(source, destination)
+                }
+            }
+        }
+
+        override fun onItemRangeRemoved(start: Int, count: Int) {
+            notifyItemRangeRemoved(start + 1, count)
+        }
+    }
+
+    init {
+        adapter.registerAdapterDataObserver(observer)
+    }
+
+    override fun getItemCount() = adapter.itemCount + 1
+
+    override fun getItemId(position: Int): Long {
+        if (position == 0) {
+            return 0L
+        } else {
+            return adapter.getItemId(position - 1) + 1
+        }
+    }
+
+    override fun getItemViewType(position: Int): Int {
+        if (position == 0) {
+            return 0
+        } else {
+            return adapter.getItemViewType(position - 1) + 1
+        }
+    }
+
+    override fun onBindViewHolder(holder: HeaderOrHolder<H>, position: Int) {
+        when (holder) {
+            is HeaderOrHolder.Header -> {
+                if (position != 0) {
+                    throw IllegalArgumentException("Adapter position is not for the header")
+                }
+            }
+            is HeaderOrHolder.Holder -> {
+                if (position > 0) {
+                    adapter.onBindViewHolder(holder.holder, position - 1)
+                } else {
+                    throw IllegalArgumentException("Adapter position is for the header")
+                }
+            }
+        }
+    }
+
+    override fun onCreateViewHolder(parentView: ViewGroup, viewType: Int): HeaderOrHolder<H> {
+        if (viewType == 0) {
+            val inflater = LayoutInflater.from(parentView.context)
+            val view = inflater.inflate(headerLayoutId, parentView, false)
+
+            return HeaderOrHolder.Header(view)
+        } else {
+            val holder = adapter.onCreateViewHolder(parentView, viewType - 1)
+
+            return HeaderOrHolder.Holder(holder)
+        }
+    }
+}
diff --git a/android/src/main/kotlin/net/mullvad/mullvadvpn/util/HeaderOrHolder.kt b/android/src/main/kotlin/net/mullvad/mullvadvpn/util/HeaderOrHolder.kt
new file mode 100644
index 0000000000..631d69100e
--- /dev/null
+++ b/android/src/main/kotlin/net/mullvad/mullvadvpn/util/HeaderOrHolder.kt
@@ -0,0 +1,9 @@
+package net.mullvad.mullvadvpn.util
+
+import android.support.v7.widget.RecyclerView.ViewHolder
+import android.view.View
+
+sealed class HeaderOrHolder<H : ViewHolder>(itemView: View) : ViewHolder(itemView) {
+    class Header<H : ViewHolder>(headerView: View) : HeaderOrHolder<H>(headerView)
+    class Holder<H : ViewHolder>(val holder: H) : HeaderOrHolder<H>(holder.itemView)
+}