en/AscalonScans: Fix http 403 (#577)

* fix: Fix http 403 - Bypass JS Challenge

* chore: Bump version

* refactor: Apply suggestion - Explicitly close response

* refactor: Apply suggestion - add tailrec modifier

* fix: Prevent future headaches - Use the same delay as the challenge

* fix: Apply suggestion - Prevent throwing without closing response

multisrc/overrides/mangathemesia/ascalonscans/src/AscalonScans.kt

@@ -0,0 +1,55 @@
+package eu.kanade.tachiyomi.extension.en.ascalonscans
+
+import eu.kanade.tachiyomi.multisrc.mangathemesia.MangaThemesia
+import eu.kanade.tachiyomi.network.GET
+import eu.kanade.tachiyomi.network.POST
+import eu.kanade.tachiyomi.network.interceptor.rateLimitHost
+import okhttp3.FormBody
+import okhttp3.HttpUrl.Companion.toHttpUrl
+import okhttp3.Interceptor
+import okhttp3.Response
+import java.io.IOException
+import java.security.MessageDigest
+
+class AscalonScans : MangaThemesia("AscalonScans", "https://ascalonscans.com", "en") {
+    override val client = super.client.newBuilder()
+        .rateLimitHost(baseUrl.toHttpUrl(), 2)
+        .addInterceptor(::jsChallengeInterceptor)
+        .build()
+
+    private fun jsChallengeInterceptor(chain: Interceptor.Chain): Response {
+        val request = chain.request()
+        val origRes = chain.proceed(request)
+        if (origRes.code != 403) return origRes
+        origRes.close()
+
+        // Same delay as the source
+        Thread.sleep(3000L)
+        val token = fetchToken(chain).sha256()
+
+        val body = FormBody.Builder().add("challenge", token).build()
+        val challengeReq = POST("$baseUrl/hcdn-cgi/jschallenge-validate", headers, body = body)
+
+        val challengeResponse = chain.proceed(challengeReq)
+        challengeResponse.close()
+        if (challengeResponse.code != 200) throw IOException("Failed to bypass js challenge!")
+
+        return chain.proceed(request)
+    }
+
+    private tailrec fun fetchToken(chain: Interceptor.Chain, attempt: Int = 0): String {
+        if (attempt > 5) throw IOException("Failed to fetch challenge token!")
+        val request = GET("$baseUrl/hcdn-cgi/jschallenge", headers)
+        val res = chain.proceed(request).body.string()
+
+        return res.substringAfter("cjs = '").substringBefore("'")
+            .takeUnless { it == "nil" } ?: fetchToken(chain, attempt + 1)
+    }
+
+    private fun String.sha256(): String {
+        return MessageDigest
+            .getInstance("SHA-256")
+            .digest(toByteArray())
+            .fold("", { str, it -> str + "%02x".format(it) })
+    }
+}

multisrc/src/main/java/eu/kanade/tachiyomi/multisrc/mangathemesia/MangaThemesiaGenerator.kt

@@ -20,7 +20,7 @@ class MangaThemesiaGenerator : ThemeSourceGenerator {
         SingleLang("Animated Glitched Comics", "https://agscomics.com", "en"),
         SingleLang("Animated Glitched Scans", "https://anigliscans.xyz", "en", overrideVersionCode = 1),
         SingleLang("Arven Scans", "https://arvenscans.com", "en"),
-        SingleLang("AscalonScans", "https://ascalonscans.com", "en"),
+        SingleLang("AscalonScans", "https://ascalonscans.com", "en", overrideVersionCode = 1),
         SingleLang("Asura Scans", "https://asuratoon.com", "en"),
         SingleLang("Azure Scans", "https://azuremanga.com", "en", overrideVersionCode = 1),
         SingleLang("Banana-Scan", "https://banana-scan.com", "fr", className = "BananaScan", isNsfw = true),