PixelDroid-App-Android/app/src/main/java/com/h/pixeldroid/fragments/feeds/HomeFragment.kt

package com.h.pixeldroid.fragments.feeds

import android.graphics.Color
import android.graphics.drawable.ColorDrawable
import android.graphics.drawable.Drawable
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.ImageView
import android.widget.TextView
import androidx.lifecycle.LiveData
import androidx.lifecycle.Observer
import androidx.paging.LivePagedListBuilder
import androidx.paging.PagedList
import androidx.recyclerview.widget.RecyclerView
import com.bumptech.glide.Glide
import com.bumptech.glide.ListPreloader
import com.bumptech.glide.RequestBuilder
import com.bumptech.glide.integration.recyclerview.RecyclerViewPreloader
import com.bumptech.glide.util.ViewPreloadSizeProvider
import com.h.pixeldroid.R
import com.h.pixeldroid.objects.Status
import com.h.pixeldroid.utils.ImageConverter
import kotlinx.android.synthetic.main.fragment_home.*
import retrofit2.Call


class HomeFragment : FeedFragment<Status, HomeFragment.HomeRecyclerViewAdapter.ViewHolder>() {

    lateinit var picRequest: RequestBuilder<Drawable>

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val view = super.onCreateView(inflater, container, savedInstanceState)

        content = makeContent()

        //RequestBuilder that is re-used for every image
        picRequest = Glide.with(this)
            .asDrawable().fitCenter()
            .placeholder(ColorDrawable(Color.GRAY))

        adapter = HomeRecyclerViewAdapter()
        list.adapter = adapter

        content.observe(viewLifecycleOwner,
            Observer { c ->
                adapter.submitList(c)
                //after a refresh is done we need to stop the pull to refresh spinner
                swipeRefreshLayout.isRefreshing = false
            })

        //Make Glide be aware of the recyclerview and pre-load images
        val sizeProvider: ListPreloader.PreloadSizeProvider<Status> = ViewPreloadSizeProvider()
        val preloader: RecyclerViewPreloader<Status> = RecyclerViewPreloader(
            Glide.with(this), adapter, sizeProvider, 4
        )
        list.addOnScrollListener(preloader)

        return view
    }

    private fun makeContent(): LiveData<PagedList<Status>> {
        fun makeInitialCall(requestedLoadSize: Int): Call<List<Status>> {
            return pixelfedAPI
                .timelineHome("Bearer $accessToken", limit="$requestedLoadSize")
        }
        fun makeAfterCall(requestedLoadSize: Int, key: String): Call<List<Status>> {
            return pixelfedAPI
                .timelineHome("Bearer $accessToken", max_id=key,
                    limit="$requestedLoadSize")
        }
        val config: PagedList.Config = PagedList.Config.Builder().setPageSize(10).build()
        factory = FeedDataSourceFactory(::makeInitialCall, ::makeAfterCall)
        return LivePagedListBuilder(factory, config).build()
    }

    /**
     * [RecyclerView.Adapter] that can display a list of Statuses
     */
    inner class HomeRecyclerViewAdapter: FeedsRecyclerViewAdapter<Status, HomeRecyclerViewAdapter.ViewHolder>() {

        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
            val view = LayoutInflater.from(parent.context)
                .inflate(R.layout.post_fragment, parent, false)
            context = view.context
            return ViewHolder(view)
        }

        /**
         * Binds the different elements of the Post Model to the view holder
         */
        override fun onBindViewHolder(holder: ViewHolder, position: Int) {
            val post = getItem(position) ?: return
            val metrics = context.resources.displayMetrics
            //Limit the height of the different images
            holder.profilePic.maxHeight = metrics.heightPixels
            holder.postPic.maxHeight = metrics.heightPixels

            //Set up the the post
            post.setupPost(holder.postView, picRequest, holder.postPic, holder.profilePic)

            //Set the image back to a placeholder if the original is too big
            if(holder.postPic.height > metrics.heightPixels) {
                ImageConverter.setDefaultImage(holder.postView, holder.postPic)
            }
        }

        /**
         * Represents the posts that will be contained within the feed
         */
        inner class ViewHolder(val postView: View) : RecyclerView.ViewHolder(postView) {
            val profilePic  : ImageView = postView.findViewById(R.id.profilePic)
            val postPic     : ImageView = postView.findViewById(R.id.postPicture)
            val username    : TextView = postView.findViewById(R.id.username)
            val usernameDesc: TextView = postView.findViewById(R.id.usernameDesc)
            val description : TextView = postView.findViewById(R.id.description)
            val nlikes      : TextView = postView.findViewById(R.id.nlikes)
            val nshares     : TextView = postView.findViewById(R.id.nshares)
        }

        override fun getPreloadItems(position: Int): MutableList<Status> {
            val status = getItem(position) ?: return mutableListOf()
            return mutableListOf(status)
        }

        override fun getPreloadRequestBuilder(item: Status): RequestBuilder<*>? {
            return picRequest.load(item.getPostUrl())
        }
    }
}