mihon/app/src/main/java/eu/kanade/tachiyomi/util/ImageUtil.kt

package eu.kanade.tachiyomi.util

import java.io.InputStream
import java.net.URLConnection

object ImageUtil {

    fun isImage(name: String, openStream: (() -> InputStream)? = null): Boolean {
        val contentType = try {
            URLConnection.guessContentTypeFromName(name)
        } catch (e: Exception) {
            null
        } ?: openStream?.let { findImageType(it)?.mime }
        return contentType?.startsWith("image/") ?: false
    }

    fun findImageType(openStream: () -> InputStream): ImageType? {
        return openStream().use { findImageType(it) }
    }

    fun findImageType(stream: InputStream): ImageType? {
        try {
            val bytes = ByteArray(8)

            val length = if (stream.markSupported()) {
                stream.mark(bytes.size)
                stream.read(bytes, 0, bytes.size).also { stream.reset() }
            } else {
                stream.read(bytes, 0, bytes.size)
            }

            if (length == -1)
                return null

            if (bytes.compareWith(charByteArrayOf(0xFF, 0xD8, 0xFF))) {
                return ImageType.JPG
            }
            if (bytes.compareWith(charByteArrayOf(0x89, 0x50, 0x4E, 0x47))) {
                return ImageType.PNG
            }
            if (bytes.compareWith("GIF8".toByteArray())) {
                return ImageType.GIF
            }
            if (bytes.compareWith("RIFF".toByteArray())) {
                return ImageType.WEBP
            }
        } catch(e: Exception) {
        }
        return null
    }

    private fun ByteArray.compareWith(magic: ByteArray): Boolean {
        for (i in 0 until magic.size) {
            if (this[i] != magic[i]) return false
        }
        return true
    }

    private fun charByteArrayOf(vararg bytes: Int): ByteArray {
        return ByteArray(bytes.size).apply {
            for (i in 0 until bytes.size) {
                set(i, bytes[i].toByte())
            }
        }
    }

    enum class ImageType(val mime: String, val extension: String) {
        JPG("image/jpeg", "jpg"),
        PNG("image/png", "png"),
        GIF("image/gif", "gif"),
        WEBP("image/webp", "webp")
    }

}