internal const val VIEWTYPE_SEND = 0    // 送信、左寄りのレイアウト
internal const val VIEWTYPE_RECV = 1    // 受信、右寄りのレイアウト

class ChatAdapter(var chats: Array<Chat>)
    : RecyclerView.Adapter<RecyclerView.ViewHolder>() {

    // ----- 会話データ ----------------------------------------------
    data class Chat(
            val type: Int = VIEWTYPE_SEND,
            val who: Bitmap?,
            val word: String?)

    // ----- ビューホルダー ------------------------------------------
    inner class SendViewHolder(view: View) : RecyclerView.ViewHolder(view) {
        val imgLeft = view.findViewById<ImageView>(R.id.imgLeft)
        val txtLeft = view.findViewById<TextView>(R.id.txtLeft)
    }
    inner class RecvViewHolder(view: View) : RecyclerView.ViewHolder(view) {
        val imgRight = view.findViewById<ImageView>(R.id.imgRight)
        val txtRight = view.findViewById<TextView>(R.id.txtRight)
    }

    // ----- アダプター本体 ------------------------------------------
    override fun getItemCount() = chats.size

    override fun getItemViewType(position: Int) = chats[position].type

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int)
    : RecyclerView.ViewHolder {
        val _inflater = LayoutInflater.from(parent.context)
        return when(viewType) {
            VIEWTYPE_SEND ->
                SendViewHolder(_inflater.inflate(R.layout.item_l, parent, false))
            VIEWTYPE_RECV ->
                RecvViewHolder(_inflater.inflate(R.layout.item_r, parent, false))
            else ->
                SendViewHolder(_inflater.inflate(R.layout.item_l, parent, false))
        }
    }

    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
        when(getItemViewType(position)) {
            VIEWTYPE_SEND -> {
                if(holder is SendViewHolder) {　// スマートキャスト
                    chats[position].who?.let { holder.imgLeft.setImageBitmap(it) }
                    chats[position].word?.let { holder.txtLeft.text = it }
                }
            }
            VIEWTYPE_RECV -> {
                if(holder is RecvViewHolder) {　// スマートキャスト
                    chats[position].who?.let { holder.imgRight.setImageBitmap(it) }
                    chats[position].word?.let { holder.txtRight.text = it }
                }
            }
            else -> {}
        }
    }
}