package net.lacolaco.smileessence.view

import android.app.Fragment
import android.app.FragmentManager
import android.os.Bundle
import android.support.v13.app.FragmentPagerAdapter
import android.support.v4.view.ViewPager
import android.view.ViewGroup
import net.lacolaco.smileessence.World
import net.lacolaco.smileessence.data.PageInfo
import net.lacolaco.smileessence.view.page.PageFragment
import java.util.*

class MainFragmentPagerAdapter(private val world: World, private val viewPager: ViewPager, fm: FragmentManager) :
        FragmentPagerAdapter(fm) {
    private val pages = Collections.unmodifiableList(world.pages.map { Page(it) })

    @Suppress("UNCHECKED_CAST")
    fun getPageFragmentAt(position: Int): PageFragment<*> =
            pages[position].fragment ?: instantiateItem(viewPager, position) as PageFragment<*>

    override fun getItem(position: Int): Fragment {
        val args = Bundle()
        args.putLong(PageFragment.KEY_WORLD_USER_ID, world.id)
        args.putInt(PageFragment.KEY_PAGE_POSITION, position)

        val info = pages[position]
        assert(info.fragment == null)
        return info.pageInfo.fragmentClass.newInstance().apply { arguments = args }
    }

    override fun getCount(): Int {
        return pages.size
    }

    override fun instantiateItem(container: ViewGroup, position: Int): Any {
        val info = pages[position]
        val fragment = super.instantiateItem(container, position)
        info.fragment = fragment as PageFragment<*>
        return fragment
    }

    override fun destroyItem(container: ViewGroup?, position: Int, `object`: Any?) {
        throw IllegalStateException("Fragments must not be destroyed by ViewPager")
    }

    private class Page(var pageInfo: PageInfo, var fragment: PageFragment<*>? = null)
}