package com.keylesspalace.tusky.util

import com.bumptech.glide.RequestBuilder
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 kotlin.coroutines.Continuation
import kotlin.coroutines.resume
import kotlin.coroutines.resumeWithException
import kotlinx.coroutines.suspendCancellableCoroutine

/**
 * Allows waiting for a Glide request to complete without blocking a background thread.
 */
suspend fun <R> RequestBuilder<R>.submitAsync(
    width: Int = Target.SIZE_ORIGINAL,
    height: Int = Target.SIZE_ORIGINAL
): R {
    return suspendCancellableCoroutine { continuation ->
        val target = addListener(ContinuationRequestListener(continuation))
            .submit(width, height)
        continuation.invokeOnCancellation { target.cancel(true) }
    }
}

private class ContinuationRequestListener<R>(continuation: Continuation<R>) : RequestListener<R> {
    private var continuation: Continuation<R>? = continuation

    override fun onLoadFailed(
        e: GlideException?,
        model: Any?,
        target: Target<R>,
        isFirstResource: Boolean
    ): Boolean {
        continuation?.let {
            continuation = null
            it.resumeWithException(e ?: GlideException("Image loading failed"))
        }
        return false
    }

    override fun onResourceReady(
        resource: R & Any,
        model: Any,
        target: Target<R>?,
        dataSource: DataSource,
        isFirstResource: Boolean
    ): Boolean {
        continuation?.let {
            if (target?.request?.isComplete == true) {
                continuation = null
                it.resume(resource)
            }
        }
        return false
    }
}