compose-jb/components/AnimatedImage/library/src/desktopMain/kotlin/org/jetbrains/compose/animatedimage/DesktopAnimatedImage.kt

package org.jetbrains.compose.animatedimage

import androidx.compose.animation.core.*
import androidx.compose.runtime.*
import androidx.compose.ui.graphics.ImageBitmap
import androidx.compose.ui.graphics.asComposeImageBitmap
import org.jetbrains.skia.AnimationFrameInfo
import org.jetbrains.skia.Bitmap
import org.jetbrains.skia.Codec
import java.net.MalformedURLException
import java.net.URL

private const val DEFAULT_FRAME_DURATION = 100

actual class AnimatedImage(val codec: Codec)

actual suspend fun loadAnimatedImage(path: String): AnimatedImage {
    val loader = getAnimatedImageLoaderByPath(path)
    return loader.loadAnimatedImage()
}

actual suspend fun loadResourceAnimatedImage(path: String): AnimatedImage {
    val loader = ResourceAnimatedImageLoader(path)
    return loader.loadAnimatedImage()
}

@Composable
actual fun AnimatedImage.animate(): ImageBitmap {
    when (codec.frameCount) {
        0 -> return ImageBitmap.Blank // No frames at all
        1 -> {
            // Just one frame, no animation
            val bitmap = remember(codec) { Bitmap().apply { allocPixels(codec.imageInfo) } }
            remember(bitmap) {
                codec.readPixels(bitmap, 0)
            }
            return bitmap.asComposeImageBitmap()
        }
        else -> {
            val transition = rememberInfiniteTransition()
            val frameIndex by transition.animateValue(
                initialValue = 0,
                targetValue = codec.frameCount - 1,
                Int.VectorConverter,
                animationSpec = infiniteRepeatable(
                    animation = keyframes {
                        durationMillis = 0
                        for ((index, frame) in codec.framesInfo.withIndex()) {
                            index at durationMillis
                            val frameDuration = calcFrameDuration(frame)

                            durationMillis += frameDuration
                        }
                    }
                )
            )

            val bitmap = remember(codec) { Bitmap().apply { allocPixels(codec.imageInfo) } }

            remember(bitmap, frameIndex) {
                codec.readPixels(bitmap, frameIndex)
            }

            return bitmap.asComposeImageBitmap()
        }
    }
}

private fun calcFrameDuration(frame: AnimationFrameInfo): Int {
    // If the frame does not contain information about a duration, set a reasonable constant duration
    val frameDuration = frame.duration
    return if (frameDuration == 0) DEFAULT_FRAME_DURATION else frameDuration
}

/**
 * Depending on the [path], provide a specific implementation of [AnimatedImageLoader]
 * @return [NetworkAnimatedImageLoader] if it is a network URL, [LocalAnimatedImageLoader] otherwise
 */
private fun getAnimatedImageLoaderByPath(path: String): AnimatedImageLoader {
    return if (isNetworkPath(path)) {
        NetworkAnimatedImageLoader(path)
    } else {
        LocalAnimatedImageLoader(path)
    }
}

private fun isNetworkPath(path: String): Boolean {
    return try {
        URL(path)
        true
    } catch (e: MalformedURLException) {
        false
    }
}