package com.example.core.ui.fragment

import android.databinding.ObservableBoolean
import android.databinding.ObservableInt
import android.databinding.ViewDataBinding
import android.support.annotation.CallSuper
import android.support.v7.widget.RecyclerView
import android.view.View
import android.view.ViewGroup
import com.orderpost.core.R
import com.orderpost.core.ui.binding.ViewModelInflater
import com.orderpost.core.ui.binding.setViewModel

abstract class ListFragment : BaseFragment() {

    override val layoutId get() = R.layout.fragment_recycler_view

    val refreshing = ObservableBoolean(false)
    val progressVisibility = ObservableInt(View.INVISIBLE)

    open val refresherColorId get() = android.R.color.black

    protected open val itemLayoutId get() = 0

    private var adapter: RecyclerView.Adapter<*>? =
            null

    protected abstract val itemCount: Int

    abstract fun refresh()

    protected abstract fun onCreateItemViewModel(index: Int): Any

    fun createRecyclerViewAdapter(): RecyclerView.Adapter<*> {
        if (itemLayoutId == 0) {
            throw UnsupportedOperationException()
        }

        return AdapterImpl().also { adapter = it }
    }

    override fun onDestroyView() {
        adapter = null
        super.onDestroyView()
    }

    protected fun notifyPaginationStart() {
        refreshing.set(true)
        progressVisibility.set(View.INVISIBLE)
        adapter?.notifyDataSetChanged()
    }

    protected fun notifyNextPageDelivered(positionStart: Int, itemCount: Int) {
        refreshing.set(false)
        progressVisibility.set(View.VISIBLE)
        adapter?.notifyItemRangeInserted(positionStart + 1, itemCount)
    }

    protected fun notifyPaginationComplete() {
        refreshing.set(false)
        progressVisibility.set(View.INVISIBLE)
    }

    private class BindableViewHolder(private val binding: ViewDataBinding)
        : RecyclerView.ViewHolder(binding.root) {

        var viewModel: Any? = null
            set(value) {
                field = value

                if (value == null) {
                    binding.unbind()
                } else {
                    binding.setViewModel(value)
                }
            }
    }

    private inner class AdapterImpl : RecyclerView.Adapter<BindableViewHolder>() {

        override fun getItemCount() = 1 + this@ListFragment.itemCount

        override fun getItemViewType(position: Int) =
                CONTENT_ITEM.takeIf { position < this@ListFragment.itemCount }
                        ?: PROGRESS_BAR

        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
                when (viewType) {
                    CONTENT_ITEM -> itemLayoutId
                    PROGRESS_BAR -> R.layout.item_progress_bar
                    else -> throw UnsupportedOperationException()
                }.let(::ViewModelInflater)
                        .inflate(parent)
                        .let(::BindableViewHolder)

        @CallSuper
        override fun onBindViewHolder(holder: BindableViewHolder, position: Int) {
            with(holder) {
                viewModel = createItemViewModel(itemViewType, position)
            }
        }

        override fun onViewRecycled(holder: BindableViewHolder) {
            holder.viewModel = null
        }

        private fun createItemViewModel(viewType: Int, position: Int) =
                when (viewType) {
                    CONTENT_ITEM -> onCreateItemViewModel(position)
                    PROGRESS_BAR -> this@ListFragment
                    else -> throw UnsupportedOperationException()
                }
    }

    companion object {
        private val CONTENT_ITEM = 0
        private val PROGRESS_BAR = 1
    }
}