Migrate to Android 29

Re-Added Cache clear to prevent deleting downloading images

app/src/main/java/xyz/quaver/pupil/util/lock.kt

@@ -0,0 +1,39 @@
+package xyz.quaver.pupil.util
+
+import android.content.Context
+import android.content.ContextWrapper
+import java.security.MessageDigest
+
+fun hash(password: String): String {
+    val bytes = password.toByteArray()
+    val md = MessageDigest.getInstance("SHA-256")
+
+    return md.digest(bytes).fold("") { str, it -> str + "%02x".format(it) }
+}
+
+// Ret1: SHA-256 Hash
+// Ret2: Hash salt
+fun hashWithSalt(password: String): Pair<String, String> {
+    val salt = (0 until 12).map { source.random() }.joinToString()
+
+    return Pair(hash(password+salt), salt)
+}
+
+val source = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
+
+data class Lock(private val type: Type, private val hash: String, private val salt: String) {
+
+    enum class Type {
+        PATTERN
+    }
+
+    fun match(password: String): Boolean {
+        return hash(password+salt) == hash
+    }
+}
+
+class LockManager(base: Context): ContextWrapper(base) {
+
+
+
+}