Tusky-App-Android/app/src/main/java/com/keylesspalace/tusky/fragment/ViewImageFragment.kt

/* Copyright 2017 Andrew Dawson
 *
 * This file is a part of Tusky.
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the
 * GNU General Public License as published by the Free Software Foundation; either version 3 of the
 * License, or (at your option) any later version.
 *
 * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
 * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
 * Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with Tusky; if not,
 * see <http://www.gnu.org/licenses>. */

package com.keylesspalace.tusky.fragment

import android.animation.Animator
import android.animation.AnimatorListenerAdapter
import android.annotation.SuppressLint
import android.content.Context
import android.graphics.drawable.Drawable
import android.os.Bundle
import android.view.*
import android.widget.ImageView
import android.widget.TextView
import com.bumptech.glide.Glide
import com.bumptech.glide.load.DataSource
import com.bumptech.glide.load.engine.GlideException
import com.bumptech.glide.request.RequestListener
import com.bumptech.glide.request.target.Target
import com.github.chrisbanes.photoview.PhotoViewAttacher
import com.keylesspalace.tusky.R
import com.keylesspalace.tusky.entity.Attachment
import com.keylesspalace.tusky.util.hide
import com.keylesspalace.tusky.util.visible
import io.reactivex.subjects.BehaviorSubject
import kotlinx.android.synthetic.main.activity_view_media.*
import kotlinx.android.synthetic.main.fragment_view_image.*
import kotlin.math.abs

class ViewImageFragment : ViewMediaFragment() {
    interface PhotoActionsListener {
        fun onBringUp()
        fun onDismiss()
        fun onPhotoTap()
    }

    private lateinit var attacher: PhotoViewAttacher
    private lateinit var photoActionsListener: PhotoActionsListener
    private lateinit var toolbar: View
    private var transition = BehaviorSubject.create<Unit>()
    private var shouldStartTransition = false

    // Volatile: Image requests happen on background thread and we want to see updates to it
    // immediately on another thread. Atomic is an overkill for such thing.
    @Volatile
    private var startedTransition = false

    override lateinit var descriptionView: TextView
    override fun onAttach(context: Context) {
        super.onAttach(context)
        photoActionsListener = context as PhotoActionsListener
    }

    @SuppressLint("ClickableViewAccessibility")
    override fun setupMediaView(url: String, previewUrl: String?) {
        descriptionView = mediaDescription
        photoView.transitionName = url
        attacher = PhotoViewAttacher(photoView).apply {
            // This prevents conflicts with ViewPager
            setAllowParentInterceptOnEdge(true)

            // Clicking outside the photo closes the viewer.
            setOnOutsidePhotoTapListener { photoActionsListener.onDismiss() }
            setOnClickListener { onMediaTap() }

            /* A vertical swipe motion also closes the viewer. This is especially useful when the photo
             * mostly fills the screen so clicking outside is difficult. */
            setOnSingleFlingListener { _, _, velocityX, velocityY ->
                var result = false
                if (abs(velocityY) > abs(velocityX)) {
                    photoActionsListener.onDismiss()
                    result = true
                }
                result
            }
        }

        val gestureDetector = GestureDetector(requireContext(), object : GestureDetector.SimpleOnGestureListener() {
            override fun onSingleTapConfirmed(e: MotionEvent?): Boolean {
                onMediaTap()
                return true
            }
        })

        var lastY = 0f

        photoView.setOnTouchListener { v, event ->
            // This part is for scaling/translating on vertical move.
            // We use raw coordinates to get the correct ones during scaling

            gestureDetector.onTouchEvent(event)

            if (event.action == MotionEvent.ACTION_DOWN) {
                lastY = event.rawY
            } else if (event.pointerCount == 1
                    && attacher.scale == 1f
                    && event.action == MotionEvent.ACTION_MOVE
            ) {
                val diff = event.rawY - lastY
                // This code is to prevent transformations during page scrolling
                // If we are already translating or we reached the threshold, then transform.
                if (photoView.translationY != 0f || abs(diff) > 40) {
                    photoView.translationY += (diff)
                    val scale = (-abs(photoView.translationY) / 720 + 1).coerceAtLeast(0.5f)
                    photoView.scaleY = scale
                    photoView.scaleX = scale
                    lastY = event.rawY
                    return@setOnTouchListener true
                }
            } else if (event.action == MotionEvent.ACTION_UP || event.action == MotionEvent.ACTION_CANCEL) {
                onGestureEnd()
            }
            attacher.onTouch(v, event)
        }

        startedTransition = false
        loadImageFromNetwork(url, previewUrl, photoView)
    }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
        toolbar = requireActivity().toolbar
        this.transition = BehaviorSubject.create()
        return inflater.inflate(R.layout.fragment_view_image, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)


        val arguments = this.requireArguments()
        val attachment = arguments.getParcelable<Attachment>(ARG_ATTACHMENT)
        this.shouldStartTransition = arguments.getBoolean(ARG_START_POSTPONED_TRANSITION)
        val url: String?
        var description: String? = null

        if (attachment != null) {
            url = attachment.url
            description = attachment.description
        } else {
            url = arguments.getString(ARG_AVATAR_URL)
            if (url == null) {
                throw IllegalArgumentException("attachment or avatar url has to be set")
            }
        }

        finalizeViewSetup(url, attachment?.previewUrl, description)
    }

    private fun onGestureEnd() {
        if (abs(photoView.translationY) > 180) {
            photoActionsListener.onDismiss()
        } else {
            photoView.animate().translationY(0f).scaleX(1f).scaleY(1f).start()
        }
    }

    private fun onMediaTap() {
        photoActionsListener.onPhotoTap()
    }

    override fun onToolbarVisibilityChange(visible: Boolean) {
        if (photoView == null || !userVisibleHint) {
            return
        }
        isDescriptionVisible = showingDescription && visible
        val alpha = if (isDescriptionVisible) 1.0f else 0.0f
        descriptionView.animate().alpha(alpha)
                .setListener(object : AnimatorListenerAdapter() {
                    override fun onAnimationEnd(animation: Animator) {
                        descriptionView.visible(isDescriptionVisible)
                        animation.removeListener(this)
                    }
                })
                .start()
    }

    override fun onDestroyView() {
        Glide.with(this).clear(photoView)
        transition.onComplete()
        super.onDestroyView()
    }

    private fun loadImageFromNetwork(url: String, previewUrl: String?, photoView: ImageView) {
        val glide = Glide.with(this)
        // Request image from the any cache
        glide
                .load(url)
                .dontAnimate()
                .onlyRetrieveFromCache(true)
                .let {
                    if (previewUrl != null)
                        it.thumbnail(glide
                                .load(previewUrl)
                                .dontAnimate()
                                .onlyRetrieveFromCache(true)
                                .centerInside()
                                .addListener(ImageRequestListener(true, isThumnailRequest = true)))
                    else it
                }
                //Request image from the network on fail load image from cache
                .error(glide.load(url)
                        .centerInside()
                        .addListener(ImageRequestListener(false, isThumnailRequest = false))
                )
                .centerInside()
                .addListener(ImageRequestListener(true, isThumnailRequest = false))
                .into(photoView)
    }

    /**
     * We start transition as soon as we think reasonable but we must take care about couple of
     * things>
     *  - Do not change image in the middle of transition. It messes up the view.
     *  - Do not transition for the views which don't require it. Starting transition from
     *      multiple fragments does weird things
     *  - Do not wait to transition until the image loads from network
     *
     * Preview, cached image, network image, x - failed, o - succeeded
     * P C N - start transition after...
     * x x x - the cache fails
     * x x o - the cache fails
     * x o o - the cache succeeds
     * o x o - the preview succeeds. Do not start on cache.
     * o o o - the preview succeeds. Do not start on cache.
     *
     * So start transition after the first success or after anything with the cache
     *
     * @param isCacheRequest - is this listener for request image from cache or from the network
     */
    private inner class ImageRequestListener(
            private val isCacheRequest: Boolean,
            private val isThumnailRequest: Boolean) : RequestListener<Drawable> {

        override fun onLoadFailed(e: GlideException?, model: Any, target: Target<Drawable>,
                                  isFirstResource: Boolean): Boolean {
            // If cache for full image failed complete transition
            if (isCacheRequest && !isThumnailRequest && shouldStartTransition
                    && !startedTransition) {
                photoActionsListener.onBringUp()
            }
            // Hide progress bar only on fail request from internet
            if (!isCacheRequest) progressBar?.hide()
            // We don't want to overwrite preview with null when main image fails to load
            return !isCacheRequest
        }

        @SuppressLint("CheckResult")
        override fun onResourceReady(resource: Drawable, model: Any, target: Target<Drawable>,
                                     dataSource: DataSource, isFirstResource: Boolean): Boolean {
            progressBar?.hide() // Always hide the progress bar on success

            if (!startedTransition || !shouldStartTransition) {
                // Set this right away so that we don't have to concurrent post() requests
                startedTransition = true
                // post() because load() replaces image with null. Sometimes after we set
                // the thumbnail.
                photoView.post {
                    target.onResourceReady(resource, null)
                    if (shouldStartTransition) photoActionsListener.onBringUp()
                }
            } else {
                // This wait for transition. If there's no transition then we should hit
                // another branch. take() will unsubscribe after we have it to not leak menmory
                transition
                        .take(1)
                        .subscribe {
                            target.onResourceReady(resource, null)
                            // It's needed. Don't ask why, I don't know, setImageDrawable() should
                            // do it by itself but somehow it doesn't work automatically.
                            // Just do it. If you don't, image will jump around when touched.
                            attacher.update()
                        }
            }
            return true
        }
    }

    override fun onTransitionEnd() {
        this.transition.onNext(Unit)
    }
}