Fix IDs (#1016)

* Allow any String IDs as long as they're sortable

* Allow any String IDs as long as they're sortable

app/src/main/java/com/keylesspalace/tusky/util/StringUtils.kt

@@ -0,0 +1,72 @@
+@file:JvmName("StringUtils")
+
+package com.keylesspalace.tusky.util
+
+import java.util.Random
+
+
+private const val POSSIBLE_CHARS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+
+fun randomAlphanumericString(count: Int): String {
+    val chars = CharArray(count)
+    val random = Random()
+    for (i in 0 until count) {
+        chars[i] = POSSIBLE_CHARS[random.nextInt(POSSIBLE_CHARS.length)]
+    }
+    return String(chars)
+}
+
+// We sort statuses by ID. Something we need to invent some ID for placeholder.
+// Not sure if inc()/dec() should be made `operator` or not
+
+/**
+ * "Increment" string so that during sorting it's bigger than [this].
+ */
+fun String.inc(): String {
+    // We assume that we will stay in the safe range for now
+    val builder = this.toCharArray()
+    builder.last().inc()
+    return String(builder)
+}
+
+
+/**
+ * "Decrement" string so that during sorting it's smaller than [this].
+ */
+fun String.dec(): String {
+    val builder = this.toCharArray()
+    var i = builder.lastIndex
+    while (i > 0) {
+        if (builder[i] > '0') {
+            builder[i] = builder[i].dec()
+            break
+        } else {
+            builder[i] = 'z'
+        }
+        i--
+    }
+    // All characters were '0'
+    if (i == 0 && this.isNotEmpty()) {
+        // Remove one character
+        return String(builder.copyOfRange(1, builder.size))
+    }
+
+    return String(builder)
+}
+
+/**
+ * A < B (strictly) by length and then by content.
+ * Examples:
+ * "abc" < "bcd"
+ * "ab"  < "abc"
+ * "cb"  < "abc"
+ * not: "ab" < "ab"
+ * not: "abc" > "cb"
+ */
+fun String.isLessThan(other: String): Boolean {
+    return when {
+        this.length < other.length -> true
+        this.length > other.length -> false
+        else -> this < other
+    }
+}