[pos] compare version from backend and show error if incompatible

2 files changed, 79 insertions, 0 deletions

diff --git a/taler-kotlin-common/src/main/java/net/taler/common/AndroidUtils.kt b/taler-kotlin-common/src/main/java/net/taler/common/AndroidUtils.kt
index ba6ee1c..b46f306 100644
--- a/taler-kotlin-common/src/main/java/net/taler/common/AndroidUtils.kt
+++ b/taler-kotlin-common/src/main/java/net/taler/common/AndroidUtils.kt
@@ -112,3 +112,12 @@ fun Long.toShortDate(context: Context): CharSequence {
     val flags = FORMAT_SHOW_DATE or FORMAT_SHOW_YEAR or FORMAT_ABBREV_ALL
     return formatDateTime(context, this, flags)
 }
+
+fun Version.getIncompatibleStringOrNull(context: Context, otherVersion: String): String? {
+    val other = Version.parse(otherVersion) ?: return context.getString(R.string.version_invalid)
+    val match = compare(other) ?: return context.getString(R.string.version_invalid)
+    if (match.compatible) return null
+    if (match.currentCmp < 0) return context.getString(R.string.version_too_old)
+    if (match.currentCmp > 0) return context.getString(R.string.version_too_new)
+    throw AssertionError("$this == $other")
+}
diff --git a/taler-kotlin-common/src/main/java/net/taler/common/Version.kt b/taler-kotlin-common/src/main/java/net/taler/common/Version.kt
new file mode 100644
index 0000000..8774115
--- /dev/null
+++ b/taler-kotlin-common/src/main/java/net/taler/common/Version.kt
@@ -0,0 +1,70 @@
+/*
+ * This file is part of GNU Taler
+ * (C) 2020 Taler Systems S.A.
+ *
+ * GNU Taler is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3, or (at your option) any later version.
+ *
+ * GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+package net.taler.common
+
+import kotlin.math.sign
+
+/**
+ * Semantic versioning, but libtool-style.
+ * See https://www.gnu.org/software/libtool/manual/html_node/Libtool-versioning.html
+ */
+data class Version(
+    val current: Int,
+    val revision: Int,
+    val age: Int
+) {
+    companion object {
+        fun parse(v: String): Version? {
+            val elements = v.split(":")
+            if (elements.size != 3) return null
+            val (currentStr, revisionStr, ageStr) = elements
+            val current = currentStr.toIntOrNull()
+            val revision = revisionStr.toIntOrNull()
+            val age = ageStr.toIntOrNull()
+            if (current == null || revision == null || age == null) return null
+            return Version(current, revision, age)
+        }
+    }
+
+    /**
+     * Compare two libtool-style versions.
+     *
+     * Returns a [VersionMatchResult] or null if the given version was null.
+     */
+    fun compare(other: Version?): VersionMatchResult? {
+        if (other == null) return null
+        val compatible = current - age <= other.current &&
+                current >= other.current - other.age
+        val currentCmp = sign((current - other.current).toDouble()).toInt()
+        return VersionMatchResult(compatible, currentCmp)
+    }
+
+    /**
+     * Result of comparing two libtool versions.
+     */
+    data class VersionMatchResult(
+        /**
+         * Is the first version compatible with the second?
+         */
+        val compatible: Boolean,
+        /**
+         * Is the first version older (-1), newer (+1) or identical (0)?
+         */
+        val currentCmp: Int
+    )
+
+}