/* 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.PointF
import android.graphics.drawable.Drawable
import android.os.Bundle
import android.view.GestureDetector
import android.view.LayoutInflater
import android.view.MotionEvent
import android.view.View
import android.view.ViewGroup
import android.widget.ImageView
import androidx.core.os.BundleCompat
import androidx.core.view.GestureDetectorCompat
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.keylesspalace.tusky.R
import com.keylesspalace.tusky.ViewMediaActivity
import com.keylesspalace.tusky.databinding.FragmentViewImageBinding
import com.keylesspalace.tusky.entity.Attachment
import com.keylesspalace.tusky.util.hide
import com.keylesspalace.tusky.util.viewBinding
import com.keylesspalace.tusky.util.visible
import com.ortiz.touchview.OnTouchCoordinatesListener
import com.ortiz.touchview.TouchImageView
import io.reactivex.rxjava3.subjects.BehaviorSubject
import kotlin.math.abs

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

    private val binding by viewBinding(FragmentViewImageBinding::bind)

    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 fun onAttach(context: Context) {
        super.onAttach(context)
        photoActionsListener = context as PhotoActionsListener
    }

    override fun setupMediaView(
        url: String,
        previewUrl: String?,
        description: String?,
        showingDescription: Boolean
    ) {
        binding.photoView.transitionName = url
        binding.mediaDescription.text = description
        binding.captionSheet.visible(showingDescription)

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

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

    @SuppressLint("ClickableViewAccessibility")
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        val arguments = this.requireArguments()
        val attachment = BundleCompat.getParcelable(arguments, ARG_ATTACHMENT, Attachment::class.java)
        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_SINGLE_IMAGE_URL)
            if (url == null) {
                throw IllegalArgumentException("attachment or image url has to be set")
            }
        }

        val singleTapDetector = GestureDetectorCompat(
            requireContext(),
            object : GestureDetector.SimpleOnGestureListener() {
                override fun onDown(e: MotionEvent) = true
                override fun onSingleTapConfirmed(e: MotionEvent): Boolean {
                    photoActionsListener.onPhotoTap()
                    return false
                }
            }
        )

        binding.photoView.setOnTouchCoordinatesListener(object : OnTouchCoordinatesListener {
            /** Y coordinate of the last single-finger drag */
            var lastDragY: Float? = null

            override fun onTouchCoordinate(view: View, event: MotionEvent, bitmapPoint: PointF) {
                singleTapDetector.onTouchEvent(event)

                // Two fingers have gone down after a single finger drag. Finish the drag
                if (event.pointerCount == 2 && lastDragY != null) {
                    onGestureEnd(view)
                    lastDragY = null
                }

                // Stop the parent view from handling touches if either (a) the user has 2+
                // fingers on the screen, or (b) the image has been zoomed in, and can be scrolled
                // horizontally in both directions.
                //
                // This stops things like ViewPager2 from trying to intercept a left/right swipe
                // and ensures that the image does not appear to "stick" to the screen as different
                // views fight over who should be handling the swipe.
                //
                // If the view can be scrolled in one direction it's OK to let the parent intercept,
                // which allows the user to swipe between images even if one or more of them have
                // been zoomed in.
                if (event.pointerCount >= 2 || view.canScrollHorizontally(1) && view.canScrollHorizontally(-1)) {
                    when (event.action) {
                        MotionEvent.ACTION_DOWN, MotionEvent.ACTION_MOVE -> {
                            view.parent.requestDisallowInterceptTouchEvent(true)
                        }

                        MotionEvent.ACTION_UP -> {
                            view.parent.requestDisallowInterceptTouchEvent(false)
                        }
                    }
                    return
                }

                // The user is dragging the image around
                if (event.pointerCount == 1) {
                    // If the image is zoomed then the swipe-to-dismiss functionality is disabled
                    if ((view as TouchImageView).isZoomed) return

                    // The user's finger just went down, start recording where they are dragging from
                    if (event.action == MotionEvent.ACTION_DOWN) {
                        lastDragY = event.rawY
                        return
                    }

                    // The user is dragging the un-zoomed image to possibly fling it up or down
                    // to dismiss.
                    if (event.action == MotionEvent.ACTION_MOVE) {
                        // lastDragY may be null; e.g., the user was performing a two-finger drag,
                        // and has lifted one finger. In this case do nothing
                        lastDragY ?: return

                        // Compute the Y offset of the drag, and scale/translate the photoview
                        // accordingly.
                        val diff = event.rawY - lastDragY!!
                        if (view.translationY != 0f || abs(diff) > 40) {
                            // Drag has definitely started, stop the parent from interfering
                            view.parent.requestDisallowInterceptTouchEvent(true)
                            view.translationY += diff
                            val scale = (-abs(view.translationY) / 720 + 1).coerceAtLeast(0.5f)
                            view.scaleY = scale
                            view.scaleX = scale
                            lastDragY = event.rawY
                        }
                        return
                    }

                    // The user has finished dragging. Allow the parent to handle touch events if
                    // appropriate, and end the gesture.
                    if (event.action == MotionEvent.ACTION_UP || event.action == MotionEvent.ACTION_CANCEL) {
                        view.parent.requestDisallowInterceptTouchEvent(false)
                        if (lastDragY != null) onGestureEnd(view)
                        lastDragY = null
                        return
                    }
                }
            }

            /**
             * Handle the end of the user's gesture.
             *
             * If the user was previously dragging, and the image has been dragged a sufficient
             * distance then we are done. Otherwise, animate the image back to its starting position.
             */
            private fun onGestureEnd(view: View) {
                if (abs(view.translationY) > 180) {
                    photoActionsListener.onDismiss()
                } else {
                    view.animate().translationY(0f).scaleX(1f).start()
                }
            }
        })

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

    override fun onToolbarVisibilityChange(visible: Boolean) {
        if (!userVisibleHint) return

        isDescriptionVisible = showingDescription && visible
        val alpha = if (isDescriptionVisible) 1.0f else 0.0f
        binding.captionSheet.animate().alpha(alpha)
            .setListener(object : AnimatorListenerAdapter() {
                override fun onAnimationEnd(animation: Animator) {
                    view ?: return
                    binding.captionSheet.visible(isDescriptionVisible)
                    animation.removeListener(this)
                }
            })
            .start()
    }

    override fun onStop() {
        super.onStop()
        Glide.with(this).clear(binding.photoView)
    }

    override fun onDestroyView() {
        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, isThumbnailRequest = true))
                    )
                } else {
                    it
                }
            }
            // Request image from the network on fail load image from cache
            .error(
                glide.load(url)
                    .centerInside()
                    .addListener(ImageRequestListener(false, isThumbnailRequest = false))
            )
            .centerInside()
            .addListener(ImageRequestListener(true, isThumbnailRequest = 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 isThumbnailRequest: 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 && !isThumbnailRequest && shouldStartTransition &&
                !startedTransition
            ) {
                photoActionsListener.onBringUp()
            }
            // Hide progress bar only on fail request from internet
            if (!isCacheRequest) binding.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 {
            binding.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.
                binding.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 memory
                transition
                    .take(1)
                    .subscribe {
                        target.onResourceReady(resource, null)
                    }
            }
            return true
        }
    }

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