Split out common code into multiplatform Kotlin library

26 files changed, 275 insertions, 1079 deletions

diff --git a/taler-kotlin-common/.gitlab-ci.yml b/taler-kotlin-common/.gitlab-ci.yml
index 49d3e98..c241e31 100644
--- a/taler-kotlin-common/.gitlab-ci.yml
+++ b/taler-kotlin-common/.gitlab-ci.yml
@@ -4,8 +4,4 @@ taler_kotlin_common_test:
     changes:
       - taler-kotlin-common/**/*
       - build.gradle
-  script: ./gradlew :taler-kotlin-common:check
-  artifacts:
-    paths:
-      - taler-kotlin-common/build/reports/lint-results.html
-    expire_in: 1 week
+  script: ./gradlew :taler-kotlin-common:jvmTest
diff --git a/taler-kotlin-common/build.gradle b/taler-kotlin-common/build.gradle
index dd083b7..129881d 100644
--- a/taler-kotlin-common/build.gradle
+++ b/taler-kotlin-common/build.gradle
@@ -1,72 +1,82 @@
-/*
- * 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/>
- */
-
 plugins {
-    id 'com.android.library'
-    id 'kotlin-android'
-    id 'kotlin-android-extensions'
+    id 'org.jetbrains.kotlin.multiplatform'
     id 'kotlinx-serialization'
 }
 
-android {
-    compileSdkVersion 29
-    //noinspection GradleDependency
-    buildToolsVersion "$build_tools_version"
+group 'net.taler'
+version '0.0.1'
 
-    defaultConfig {
-        minSdkVersion 24
-        targetSdkVersion 29
-        versionCode 1
-        versionName "0.1"
+apply plugin: 'maven-publish'
 
-        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
-        consumerProguardFiles 'consumer-rules.pro'
+kotlin {
+    jvm()
+    // This is for iPhone simulator
+    // Switch here to iosArm64 (or iosArm32) to build library for iPhone device
+    iosX64("ios") {
+        binaries {
+            framework()
+        }
     }
-
-    buildTypes {
-        release {
-            minifyEnabled false
-            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+    linuxX64("linux")
+    js {
+        browser {
+        }
+        nodejs {
+        }
+    }
+    sourceSets {
+        def serialization_version = "0.20.0"
+        commonMain {
+            dependencies {
+                implementation kotlin('stdlib-common')
+                implementation "org.jetbrains.kotlinx:kotlinx-serialization-runtime-common:$serialization_version"
+            }
+        }
+        commonTest {
+            dependencies {
+                implementation kotlin('test-common')
+                implementation kotlin('test-annotations-common')
+            }
+        }
+        jvmMain {
+            dependencies {
+                implementation kotlin('stdlib-jdk8')
+                implementation "org.jetbrains.kotlinx:kotlinx-serialization-runtime:$serialization_version"
+            }
+        }
+        jvmTest {
+            dependencies {
+                implementation kotlin('test')
+                implementation kotlin('test-junit')
+            }
+        }
+        jsMain {
+            dependencies {
+                implementation kotlin('stdlib-js')
+                implementation "org.jetbrains.kotlinx:kotlinx-serialization-runtime-js:$serialization_version"
+            }
+        }
+        jsTest {
+            dependencies {
+                implementation kotlin('test-js')
+            }
+        }
+        nativeMain {
+            dependsOn commonMain
+            dependencies {
+                implementation "org.jetbrains.kotlinx:kotlinx-serialization-runtime-native:$serialization_version"
+            }
+        }
+        nativeTest {
+            dependsOn commonTest
+        }
+        configure([targets.linux, targets.ios]) {
+            compilations.main.source(sourceSets.nativeMain)
+            compilations.test.source(sourceSets.nativeTest)
         }
     }
-
 }
 
-dependencies {
-    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
-    implementation 'androidx.appcompat:appcompat:1.1.0'
-    implementation 'androidx.core:core-ktx:1.3.0'
-
-    // Navigation
-    implementation "androidx.navigation:navigation-ui-ktx:$nav_version"
-    implementation "androidx.navigation:navigation-fragment-ktx:$nav_version"
-
-    // ViewModel and LiveData
-    def lifecycle_version = "2.2.0"
-    implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"
-
-    // QR codes
-    implementation 'com.google.zxing:core:3.4.0'  // needs minSdkVersion 24+
-
-    // JSON parsing and serialization
-    api "org.jetbrains.kotlinx:kotlinx-serialization-runtime:0.20.0"
-    implementation "com.fasterxml.jackson.module:jackson-module-kotlin:2.10.2"
-
-    lintChecks 'com.github.thirdegg:lint-rules:0.0.4-alpha'
-
-    testImplementation 'junit:junit:4.13'
-    testImplementation 'org.json:json:20190722'
+configurations {
+    compileClasspath
 }
diff --git a/taler-kotlin-common/consumer-rules.pro b/taler-kotlin-common/consumer-rules.pro
deleted file mode 100644
index e69de29..0000000
--- a/taler-kotlin-common/consumer-rules.pro
+++ /dev/null
diff --git a/taler-kotlin-common/proguard-rules.pro b/taler-kotlin-common/proguard-rules.pro
deleted file mode 100644
index f1b4245..0000000
--- a/taler-kotlin-common/proguard-rules.pro
+++ /dev/null
@@ -1,21 +0,0 @@
-# Add project specific ProGuard rules here.
-# You can control the set of applied configuration files using the
-# proguardFiles setting in build.gradle.
-#
-# For more details, see
-#   http://developer.android.com/guide/developing/tools/proguard.html
-
-# If your project uses WebView with JS, uncomment the following
-# and specify the fully qualified class name to the JavaScript interface
-# class:
-#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
-#   public *;
-#}
-
-# Uncomment this to preserve the line number information for
-# debugging stack traces.
-#-keepattributes SourceFile,LineNumberTable
-
-# If you keep the line number information, uncomment this to
-# hide the original source file name.
-#-renamesourcefileattribute SourceFile
diff --git a/taler-kotlin-common/src/main/java/net/taler/common/Amount.kt b/taler-kotlin-common/src/commonMain/kotlin/net/taler/common/Amount.kt
index 992f93b..84d10c5 100644
--- a/taler-kotlin-common/src/main/java/net/taler/common/Amount.kt
+++ b/taler-kotlin-common/src/commonMain/kotlin/net/taler/common/Amount.kt
@@ -16,23 +16,12 @@
 
 package net.taler.common
 
-import android.annotation.SuppressLint
-import com.fasterxml.jackson.core.JsonGenerator
-import com.fasterxml.jackson.core.JsonParser
-import com.fasterxml.jackson.databind.DeserializationContext
-import com.fasterxml.jackson.databind.JsonMappingException
-import com.fasterxml.jackson.databind.SerializerProvider
-import com.fasterxml.jackson.databind.annotation.JsonDeserialize
-import com.fasterxml.jackson.databind.annotation.JsonSerialize
-import com.fasterxml.jackson.databind.deser.std.StdDeserializer
-import com.fasterxml.jackson.databind.ser.std.StdSerializer
 import kotlinx.serialization.Decoder
 import kotlinx.serialization.Encoder
 import kotlinx.serialization.KSerializer
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.Serializer
-import org.json.JSONObject
-import java.lang.Math.floorDiv
+import kotlin.math.floor
 import kotlin.math.pow
 import kotlin.math.roundToInt
 
@@ -40,8 +29,6 @@ class AmountParserException(msg: String? = null, cause: Throwable? = null) : Exc
 class AmountOverflowException(msg: String? = null, cause: Throwable? = null) : Exception(msg, cause)
 
 @Serializable(with = KotlinXAmountSerializer::class)
-@JsonSerialize(using = AmountSerializer::class)
-@JsonDeserialize(using = AmountDeserializer::class)
 data class Amount(
     /**
      * name of the currency using either a three-character ISO 4217 currency code,
@@ -70,29 +57,21 @@ data class Amount(
 
         private const val FRACTIONAL_BASE: Int = 100000000 // 1e8
 
-        @Suppress("unused")
-        private val REGEX = Regex("""^[-_*A-Za-z0-9]{1,12}:([0-9]+)\.?([0-9]+)?$""")
         private val REGEX_CURRENCY = Regex("""^[-_*A-Za-z0-9]{1,12}$""")
-        private val MAX_VALUE = 2.0.pow(52)
+        val MAX_VALUE = 2.0.pow(52).toLong()
         private const val MAX_FRACTION_LENGTH = 8
-        private const val MAX_FRACTION = 99_999_999
+        const val MAX_FRACTION = 99_999_999
 
-        @Throws(AmountParserException::class)
-        @SuppressLint("CheckedExceptions")
         fun zero(currency: String): Amount {
             return Amount(checkCurrency(currency), 0, 0)
         }
 
-        @Throws(AmountParserException::class)
-        @SuppressLint("CheckedExceptions")
         fun fromJSONString(str: String): Amount {
             val split = str.split(":")
             if (split.size != 2) throw AmountParserException("Invalid Amount Format")
             return fromString(split[0], split[1])
         }
 
-        @Throws(AmountParserException::class)
-        @SuppressLint("CheckedExceptions")
         fun fromString(currency: String, str: String): Amount {
             // value
             val valueSplit = str.split(".")
@@ -110,31 +89,23 @@ data class Amount(
             return Amount(checkCurrency(currency), value, fraction)
         }
 
-        @Throws(AmountParserException::class)
-        @SuppressLint("CheckedExceptions")
-        fun fromJsonObject(json: JSONObject): Amount {
-            val currency = checkCurrency(json.optString("currency"))
-            val value = checkValue(json.optString("value").toLongOrNull())
-            val fraction = checkFraction(json.optString("fraction").toIntOrNull())
-            return Amount(currency, value, fraction)
-        }
+        fun min(currency: String): Amount = Amount(currency, 0, 1)
+        fun max(currency: String): Amount = Amount(currency, MAX_VALUE, MAX_FRACTION)
+
 
-        @Throws(AmountParserException::class)
-        private fun checkCurrency(currency: String): String {
+        internal fun checkCurrency(currency: String): String {
             if (!REGEX_CURRENCY.matches(currency))
                 throw AmountParserException("Invalid currency: $currency")
             return currency
         }
 
-        @Throws(AmountParserException::class)
-        private fun checkValue(value: Long?): Long {
+        internal fun checkValue(value: Long?): Long {
             if (value == null || value > MAX_VALUE)
                 throw AmountParserException("Value $value greater than $MAX_VALUE")
             return value
         }
 
-        @Throws(AmountParserException::class)
-        private fun checkFraction(fraction: Int?): Int {
+        internal fun checkFraction(fraction: Int?): Int {
             if (fraction == null || fraction > MAX_FRACTION)
                 throw AmountParserException("Fraction $fraction greater than $MAX_FRACTION")
             return fraction
@@ -153,25 +124,23 @@ data class Amount(
             "$value.$fractionStr"
         }
 
-    @Throws(AmountOverflowException::class)
     operator fun plus(other: Amount): Amount {
         check(currency == other.currency) { "Can only subtract from same currency" }
-        val resultValue = value + other.value + floorDiv(fraction + other.fraction, FRACTIONAL_BASE)
+        val resultValue = value + other.value + floor((fraction + other.fraction).toDouble() / FRACTIONAL_BASE).toLong()
         if (resultValue > MAX_VALUE)
             throw AmountOverflowException()
         val resultFraction = (fraction + other.fraction) % FRACTIONAL_BASE
         return Amount(currency, resultValue, resultFraction)
     }
 
-    @Throws(AmountOverflowException::class)
     operator fun times(factor: Int): Amount {
+        // TODO consider replacing with a faster implementation
         if (factor == 0) return zero(currency)
         var result = this
         for (i in 1 until factor) result += this
         return result
     }
 
-    @Throws(AmountOverflowException::class)
     operator fun minus(other: Amount): Amount {
         check(currency == other.currency) { "Can only subtract from same currency" }
         var resultValue = value
@@ -227,20 +196,3 @@ object KotlinXAmountSerializer: KSerializer<Amount> {
         return Amount.fromJSONString(decoder.decodeString())
     }
 }
-
-class AmountSerializer : StdSerializer<Amount>(Amount::class.java) {
-    override fun serialize(value: Amount, gen: JsonGenerator, provider: SerializerProvider) {
-        gen.writeString(value.toJSONString())
-    }
-}
-
-class AmountDeserializer : StdDeserializer<Amount>(Amount::class.java) {
-    override fun deserialize(p: JsonParser, ctxt: DeserializationContext): Amount {
-        val node = p.codec.readValue(p, String::class.java)
-        try {
-            return Amount.fromJSONString(node)
-        } catch (e: AmountParserException) {
-            throw JsonMappingException(p, "Error parsing Amount", e)
-        }
-    }
-}
diff --git a/taler-kotlin-common/src/commonMain/kotlin/net/taler/common/Time.kt b/taler-kotlin-common/src/commonMain/kotlin/net/taler/common/Time.kt
new file mode 100644
index 0000000..962e004
--- /dev/null
+++ b/taler-kotlin-common/src/commonMain/kotlin/net/taler/common/Time.kt
@@ -0,0 +1,81 @@
+/*
+ * 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 kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+import net.taler.common.Duration.Companion.FOREVER
+import kotlin.math.max
+
+expect fun nowMillis(): Long
+
+@Serializable
+data class Timestamp(
+    @SerialName("t_ms")
+    val ms: Long
+) : Comparable<Timestamp> {
+
+    companion object {
+        const val NEVER: Long = -1  // TODO or UINT64_MAX?
+        fun now(): Timestamp = Timestamp(nowMillis())
+    }
+
+    /**
+     * Returns a copy of this [Timestamp] rounded to seconds.
+     */
+    fun truncateSeconds(): Timestamp {
+        if (ms == NEVER) return Timestamp(ms)
+        return Timestamp((ms / 1000L) * 1000L)
+    }
+
+    operator fun minus(other: Timestamp): Duration = when {
+        ms == NEVER -> Duration(FOREVER)
+        other.ms == NEVER -> throw Error("Invalid argument for timestamp comparision")
+        ms < other.ms -> Duration(0)
+        else -> Duration(ms - other.ms)
+    }
+
+    operator fun minus(other: Duration): Timestamp = when {
+        ms == NEVER -> this
+        other.ms == FOREVER -> Timestamp(0)
+        else -> Timestamp(max(0, ms - other.ms))
+    }
+
+    override fun compareTo(other: Timestamp): Int {
+        return if (ms == NEVER) {
+            if (other.ms == NEVER) 0
+            else 1
+        } else {
+            if (other.ms == NEVER) -1
+            else ms.compareTo(other.ms)
+        }
+    }
+
+}
+
+@Serializable
+data class Duration(
+    /**
+     * Duration in milliseconds.
+     */
+    @SerialName("d_ms")
+    val ms: Long
+) {
+    companion object {
+        const val FOREVER: Long = -1  // TODO or UINT64_MAX?
+    }
+}
diff --git a/taler-kotlin-common/src/main/java/net/taler/common/Version.kt b/taler-kotlin-common/src/commonMain/kotlin/net/taler/common/Version.kt
index 8774115..8774115 100644
--- a/taler-kotlin-common/src/main/java/net/taler/common/Version.kt
+++ b/taler-kotlin-common/src/commonMain/kotlin/net/taler/common/Version.kt
diff --git a/taler-kotlin-common/src/test/java/net/taler/common/AmountTest.kt b/taler-kotlin-common/src/commonTest/kotlin/net/taler/common/AmountTest.kt
index 97d9667..e184307 100644
--- a/taler-kotlin-common/src/test/java/net/taler/common/AmountTest.kt
+++ b/taler-kotlin-common/src/commonTest/kotlin/net/taler/common/AmountTest.kt
@@ -16,20 +16,26 @@
 
 package net.taler.common
 
-import com.fasterxml.jackson.databind.ObjectMapper
-import com.fasterxml.jackson.module.kotlin.KotlinModule
-import com.fasterxml.jackson.module.kotlin.readValue
-import org.json.JSONObject
-import org.junit.Assert.assertEquals
-import org.junit.Assert.assertFalse
-import org.junit.Assert.assertTrue
-import org.junit.Assert.fail
-import org.junit.Test
+import kotlin.random.Random
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+import kotlin.test.fail
 
 class AmountTest {
 
+    companion object {
+        fun getRandomAmount() = getRandomAmount(getRandomString(1, Random.nextInt(1, 12)))
+        fun getRandomAmount(currency: String): Amount {
+            val value = Random.nextLong(0, Amount.MAX_VALUE)
+            val fraction = Random.nextInt(0, Amount.MAX_FRACTION)
+            return Amount(currency, value, fraction)
+        }
+    }
+
     @Test
-    fun `test fromJSONString() works`() {
+    fun testFromJSONString() {
         var str = "TESTKUDOS:23.42"
         var amount = Amount.fromJSONString(str)
         assertEquals(str, amount.toJSONString())
@@ -56,7 +62,7 @@ class AmountTest {
     }
 
     @Test
-    fun `test fromJSONString() accepts max values, rejects above`() {
+    fun testFromJSONStringAcceptsMaxValuesRejectsAbove() {
         val maxValue = 4503599627370496
         val str = "TESTKUDOS123:$maxValue.99999999"
         val amount = Amount.fromJSONString(str)
@@ -82,35 +88,7 @@ class AmountTest {
     }
 
     @Test
-    fun `test JSON deserialization()`() {
-        val mapper = ObjectMapper().registerModule(KotlinModule())
-        var str = "TESTKUDOS:23.42"
-        var amount: Amount = mapper.readValue("\"$str\"")
-        assertEquals(str, amount.toJSONString())
-        assertEquals("TESTKUDOS", amount.currency)
-        assertEquals(23, amount.value)
-        assertEquals((0.42 * 1e8).toInt(), amount.fraction)
-        assertEquals("23.42 TESTKUDOS", amount.toString())
-
-        str = "EUR:500000000.00000001"
-        amount = mapper.readValue("\"$str\"")
-        assertEquals(str, amount.toJSONString())
-        assertEquals("EUR", amount.currency)
-        assertEquals(500000000, amount.value)
-        assertEquals(1, amount.fraction)
-        assertEquals("500000000.00000001 EUR", amount.toString())
-
-        str = "EUR:1500000000.00000003"
-        amount = mapper.readValue("\"$str\"")
-        assertEquals(str, amount.toJSONString())
-        assertEquals("EUR", amount.currency)
-        assertEquals(1500000000, amount.value)
-        assertEquals(3, amount.fraction)
-        assertEquals("1500000000.00000003 EUR", amount.toString())
-    }
-
-    @Test
-    fun `test fromJSONString() rejections`() {
+    fun testFromJSONStringRejections() {
         assertThrows<AmountParserException> {
             Amount.fromJSONString("TESTKUDOS:0,5")
         }
@@ -132,71 +110,7 @@ class AmountTest {
     }
 
     @Test
-    fun `test fromJsonObject() works`() {
-        val map = mapOf(
-            "currency" to "TESTKUDOS",
-            "value" to "23",
-            "fraction" to "42000000"
-        )
-
-        val amount = Amount.fromJsonObject(JSONObject(map))
-        assertEquals("TESTKUDOS:23.42", amount.toJSONString())
-        assertEquals("TESTKUDOS", amount.currency)
-        assertEquals(23, amount.value)
-        assertEquals(42000000, amount.fraction)
-        assertEquals("23.42 TESTKUDOS", amount.toString())
-    }
-
-    @Test
-    fun `test fromJsonObject() accepts max values, rejects above`() {
-        val maxValue = 4503599627370496
-        val maxFraction = 99999999
-        var map = mapOf(
-            "currency" to "TESTKUDOS123",
-            "value" to "$maxValue",
-            "fraction" to "$maxFraction"
-        )
-
-        val amount = Amount.fromJsonObject(JSONObject(map))
-        assertEquals("TESTKUDOS123:$maxValue.$maxFraction", amount.toJSONString())
-        assertEquals("TESTKUDOS123", amount.currency)
-        assertEquals(maxValue, amount.value)
-        assertEquals(maxFraction, amount.fraction)
-        assertEquals("$maxValue.$maxFraction TESTKUDOS123", amount.toString())
-
-        // longer currency not accepted
-        assertThrows<AmountParserException>("longer currency was accepted") {
-            map = mapOf(
-                "currency" to "TESTKUDOS1234",
-                "value" to "$maxValue",
-                "fraction" to "$maxFraction"
-            )
-            Amount.fromJsonObject(JSONObject(map))
-        }
-
-        // max value + 1 not accepted
-        assertThrows<AmountParserException>("max value + 1 was accepted") {
-            map = mapOf(
-                "currency" to "TESTKUDOS123",
-                "value" to "${maxValue + 1}",
-                "fraction" to "$maxFraction"
-            )
-            Amount.fromJsonObject(JSONObject(map))
-        }
-
-        // max fraction + 1 not accepted
-        assertThrows<AmountParserException>("max fraction + 1 was accepted") {
-            map = mapOf(
-                "currency" to "TESTKUDOS123",
-                "value" to "$maxValue",
-                "fraction" to "${maxFraction + 1}"
-            )
-            Amount.fromJsonObject(JSONObject(map))
-        }
-    }
-
-    @Test
-    fun `test addition`() {
+    fun testAddition() {
         assertEquals(
             Amount.fromJSONString("EUR:2"),
             Amount.fromJSONString("EUR:1") + Amount.fromJSONString("EUR:1")
@@ -218,7 +132,7 @@ class AmountTest {
     }
 
     @Test
-    fun `test times`() {
+    fun testTimes() {
         assertEquals(
             Amount.fromJSONString("EUR:2"),
             Amount.fromJSONString("EUR:2") * 1
@@ -231,6 +145,12 @@ class AmountTest {
             Amount.fromJSONString("EUR:4.5"),
             Amount.fromJSONString("EUR:1.5") * 3
         )
+        assertEquals(Amount.fromJSONString("EUR:0"), Amount.fromJSONString("EUR:1.11") * 0)
+        assertEquals(Amount.fromJSONString("EUR:1.11"), Amount.fromJSONString("EUR:1.11") * 1)
+        assertEquals(Amount.fromJSONString("EUR:2.22"), Amount.fromJSONString("EUR:1.11") * 2)
+        assertEquals(Amount.fromJSONString("EUR:3.33"), Amount.fromJSONString("EUR:1.11") * 3)
+        assertEquals(Amount.fromJSONString("EUR:4.44"), Amount.fromJSONString("EUR:1.11") * 4)
+        assertEquals(Amount.fromJSONString("EUR:5.55"), Amount.fromJSONString("EUR:1.11") * 5)
         assertEquals(
             Amount.fromJSONString("EUR:1500000000.00000003"),
             Amount.fromJSONString("EUR:500000000.00000001") * 3
@@ -241,7 +161,7 @@ class AmountTest {
     }
 
     @Test
-    fun `test subtraction`() {
+    fun testSubtraction() {
         assertEquals(
             Amount.fromJSONString("EUR:0"),
             Amount.fromJSONString("EUR:1") - Amount.fromJSONString("EUR:1")
@@ -263,7 +183,7 @@ class AmountTest {
     }
 
     @Test
-    fun `test isZero()`() {
+    fun testIsZero() {
         assertTrue(Amount.zero("EUR").isZero())
         assertTrue(Amount.fromJSONString("EUR:0").isZero())
         assertTrue(Amount.fromJSONString("EUR:0.0").isZero())
@@ -276,14 +196,17 @@ class AmountTest {
     }
 
     @Test
-    fun `test comparision`() {
+    fun testComparision() {
         assertTrue(Amount.fromJSONString("EUR:0") <= Amount.fromJSONString("EUR:0"))
         assertTrue(Amount.fromJSONString("EUR:0") <= Amount.fromJSONString("EUR:0.00000001"))
         assertTrue(Amount.fromJSONString("EUR:0") < Amount.fromJSONString("EUR:0.00000001"))
         assertTrue(Amount.fromJSONString("EUR:0") < Amount.fromJSONString("EUR:1"))
-        assertTrue(Amount.fromJSONString("EUR:0") == Amount.fromJSONString("EUR:0"))
-        assertTrue(Amount.fromJSONString("EUR:42") == Amount.fromJSONString("EUR:42"))
-        assertTrue(Amount.fromJSONString("EUR:42.00000001") == Amount.fromJSONString("EUR:42.00000001"))
+        assertEquals(Amount.fromJSONString("EUR:0"), Amount.fromJSONString("EUR:0"))
+        assertEquals(Amount.fromJSONString("EUR:42"), Amount.fromJSONString("EUR:42"))
+        assertEquals(
+            Amount.fromJSONString("EUR:42.00000001"),
+            Amount.fromJSONString("EUR:42.00000001")
+        )
         assertTrue(Amount.fromJSONString("EUR:42.00000001") >= Amount.fromJSONString("EUR:42.00000001"))
         assertTrue(Amount.fromJSONString("EUR:42.00000002") >= Amount.fromJSONString("EUR:42.00000001"))
         assertTrue(Amount.fromJSONString("EUR:42.00000002") > Amount.fromJSONString("EUR:42.00000001"))
diff --git a/taler-kotlin-common/src/main/java/net/taler/common/SignedAmount.kt b/taler-kotlin-common/src/commonTest/kotlin/net/taler/common/TestUtils.kt
index 03a0d6e..e3a6c17 100644
--- a/taler-kotlin-common/src/main/java/net/taler/common/SignedAmount.kt
+++ b/taler-kotlin-common/src/commonTest/kotlin/net/taler/common/TestUtils.kt
@@ -16,25 +16,11 @@
 
 package net.taler.common
 
-import android.annotation.SuppressLint
+import kotlin.random.Random
 
-data class SignedAmount(
-    val positive: Boolean,
-    val amount: Amount
-) {
-
-    companion object {
-        @Throws(AmountParserException::class)
-        @SuppressLint("CheckedExceptions")
-        fun fromJSONString(str: String): SignedAmount = when (str.substring(0, 1)) {
-            "-" -> SignedAmount(false, Amount.fromJSONString(str.substring(1)))
-            "+" -> SignedAmount(true, Amount.fromJSONString(str.substring(1)))
-            else -> SignedAmount(true, Amount.fromJSONString(str))
-        }
-    }
-
-    override fun toString(): String {
-        return if (positive) "$amount" else "-$amount"
-    }
-
-}
\ No newline at end of file
+private val charPool: List<Char> = ('a'..'z') + ('A'..'Z') + ('0'..'9')
+fun getRandomString(minLength: Int = 1, maxLength: Int = Random.nextInt(0, 1337)) =
+    (minLength..maxLength)
+        .map { Random.nextInt(0, charPool.size) }
+        .map(charPool::get)
+        .joinToString("")
diff --git a/taler-kotlin-common/src/test/java/net/taler/common/VersionTest.kt b/taler-kotlin-common/src/commonTest/kotlin/net/taler/common/VersionTest.kt
index 70f30eb..f4f17ea 100644
--- a/taler-kotlin-common/src/test/java/net/taler/common/VersionTest.kt
+++ b/taler-kotlin-common/src/commonTest/kotlin/net/taler/common/VersionTest.kt
@@ -16,9 +16,9 @@
 
 package net.taler.common
 
-import org.junit.Assert.assertEquals
-import org.junit.Assert.assertNull
-import org.junit.Test
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNull
 
 class VersionTest {
 
diff --git a/taler-kotlin-common/src/jsMain/kotlin/net/taler/common/Time.kt b/taler-kotlin-common/src/jsMain/kotlin/net/taler/common/Time.kt
new file mode 100644
index 0000000..b114022
--- /dev/null
+++ b/taler-kotlin-common/src/jsMain/kotlin/net/taler/common/Time.kt
@@ -0,0 +1,23 @@
+/*
+ * 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.js.Date
+
+actual fun nowMillis(): Long {
+    return Date().getMilliseconds().toLong()
+}
diff --git a/taler-kotlin-common/src/jvmMain/kotlin/net/taler/common/Time.kt b/taler-kotlin-common/src/jvmMain/kotlin/net/taler/common/Time.kt
new file mode 100644
index 0000000..6cd9040
--- /dev/null
+++ b/taler-kotlin-common/src/jvmMain/kotlin/net/taler/common/Time.kt
@@ -0,0 +1,21 @@
+/*
+ * 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
+
+actual fun nowMillis(): Long {
+    return System.currentTimeMillis()
+}
diff --git a/taler-kotlin-common/src/main/AndroidManifest.xml b/taler-kotlin-common/src/main/AndroidManifest.xml
deleted file mode 100644
index 902ddc1..0000000
--- a/taler-kotlin-common/src/main/AndroidManifest.xml
+++ /dev/null
@@ -1,24 +0,0 @@
-<!--
-  ~ 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/>
-  -->
-
-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="net.taler.common">
-
-    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
-    <uses-permission android:name="android.permission.INTERNET" />
-    <uses-permission android:name="android.permission.NFC" />
-
-</manifest>
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
deleted file mode 100644
index b46f306..0000000
--- a/taler-kotlin-common/src/main/java/net/taler/common/AndroidUtils.kt
+++ /dev/null
@@ -1,123 +0,0 @@
-/*
- * 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 android.content.Context
-import android.content.Context.CONNECTIVITY_SERVICE
-import android.content.Intent
-import android.content.pm.PackageManager.MATCH_DEFAULT_ONLY
-import android.net.ConnectivityManager
-import android.net.NetworkCapabilities.NET_CAPABILITY_INTERNET
-import android.os.Build.VERSION.SDK_INT
-import android.os.Looper
-import android.text.format.DateUtils.DAY_IN_MILLIS
-import android.text.format.DateUtils.FORMAT_ABBREV_ALL
-import android.text.format.DateUtils.FORMAT_ABBREV_MONTH
-import android.text.format.DateUtils.FORMAT_ABBREV_RELATIVE
-import android.text.format.DateUtils.FORMAT_NO_YEAR
-import android.text.format.DateUtils.FORMAT_SHOW_DATE
-import android.text.format.DateUtils.FORMAT_SHOW_TIME
-import android.text.format.DateUtils.FORMAT_SHOW_YEAR
-import android.text.format.DateUtils.MINUTE_IN_MILLIS
-import android.text.format.DateUtils.formatDateTime
-import android.text.format.DateUtils.getRelativeTimeSpanString
-import android.view.View
-import android.view.View.INVISIBLE
-import android.view.View.VISIBLE
-import android.view.inputmethod.InputMethodManager
-import androidx.core.content.ContextCompat.getSystemService
-import androidx.fragment.app.Fragment
-import androidx.navigation.NavDirections
-import androidx.navigation.fragment.findNavController
-
-fun View.fadeIn(endAction: () -> Unit = {}) {
-    if (visibility == VISIBLE && alpha == 1f) return
-    alpha = 0f
-    visibility = VISIBLE
-    animate().alpha(1f).withEndAction {
-        if (context != null) endAction.invoke()
-    }.start()
-}
-
-fun View.fadeOut(endAction: () -> Unit = {}) {
-    if (visibility == INVISIBLE) return
-    animate().alpha(0f).withEndAction {
-        if (context == null) return@withEndAction
-        visibility = INVISIBLE
-        alpha = 1f
-        endAction.invoke()
-    }.start()
-}
-
-fun View.hideKeyboard() {
-    getSystemService(context, InputMethodManager::class.java)
-        ?.hideSoftInputFromWindow(windowToken, 0)
-}
-
-fun assertUiThread() {
-    check(Looper.getMainLooper().thread == Thread.currentThread())
-}
-
-/**
- * Use this with 'when' expressions when you need it to handle all possibilities/branches.
- */
-val <T> T.exhaustive: T
-    get() = this
-
-fun Context.isOnline(): Boolean {
-    val cm = getSystemService(CONNECTIVITY_SERVICE) as ConnectivityManager
-    return if (SDK_INT < 29) {
-        @Suppress("DEPRECATION")
-        cm.activeNetworkInfo?.isConnected == true
-    } else {
-        val capabilities = cm.getNetworkCapabilities(cm.activeNetwork) ?: return false
-        capabilities.hasCapability(NET_CAPABILITY_INTERNET)
-    }
-}
-
-fun Intent.isSafe(context: Context): Boolean {
-    return context.packageManager.queryIntentActivities(this, MATCH_DEFAULT_ONLY).isNotEmpty()
-}
-
-fun Fragment.navigate(directions: NavDirections) = findNavController().navigate(directions)
-
-fun Long.toRelativeTime(context: Context): CharSequence {
-    val now = System.currentTimeMillis()
-    return if (now - this > DAY_IN_MILLIS * 2) {
-        val flags = FORMAT_SHOW_TIME or FORMAT_SHOW_DATE or FORMAT_ABBREV_MONTH or FORMAT_NO_YEAR
-        formatDateTime(context, this, flags)
-    } else getRelativeTimeSpanString(this, now, MINUTE_IN_MILLIS, FORMAT_ABBREV_RELATIVE)
-}
-
-fun Long.toAbsoluteTime(context: Context): CharSequence {
-    val flags = FORMAT_SHOW_TIME or FORMAT_SHOW_DATE or FORMAT_SHOW_YEAR
-    return formatDateTime(context, this, flags)
-}
-
-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/ByteArrayUtils.kt b/taler-kotlin-common/src/main/java/net/taler/common/ByteArrayUtils.kt
deleted file mode 100644
index fba0d07..0000000
--- a/taler-kotlin-common/src/main/java/net/taler/common/ByteArrayUtils.kt
+++ /dev/null
@@ -1,53 +0,0 @@
-/*
- * 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
-
-object ByteArrayUtils {
-
-    private const val HEX_CHARS = "0123456789ABCDEF"
-
-    fun hexStringToByteArray(data: String): ByteArray {
-        val result = ByteArray(data.length / 2)
-
-        for (i in data.indices step 2) {
-            val firstIndex = HEX_CHARS.indexOf(data[i])
-            val secondIndex = HEX_CHARS.indexOf(data[i + 1])
-
-            val octet = firstIndex.shl(4).or(secondIndex)
-            result[i.shr(1)] = octet.toByte()
-        }
-        return result
-    }
-
-
-    private val HEX_CHARS_ARRAY = HEX_CHARS.toCharArray()
-
-    @Suppress("unused")
-    fun toHex(byteArray: ByteArray): String {
-        val result = StringBuffer()
-
-        byteArray.forEach {
-            val octet = it.toInt()
-            val firstIndex = (octet and 0xF0).ushr(4)
-            val secondIndex = octet and 0x0F
-            result.append(HEX_CHARS_ARRAY[firstIndex])
-            result.append(HEX_CHARS_ARRAY[secondIndex])
-        }
-        return result.toString()
-    }
-
-}
diff --git a/taler-kotlin-common/src/main/java/net/taler/common/CombinedLiveData.kt b/taler-kotlin-common/src/main/java/net/taler/common/CombinedLiveData.kt
deleted file mode 100644
index 4e7016b..0000000
--- a/taler-kotlin-common/src/main/java/net/taler/common/CombinedLiveData.kt
+++ /dev/null
@@ -1,51 +0,0 @@
-/*
- * 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 androidx.lifecycle.LiveData
-import androidx.lifecycle.MediatorLiveData
-import androidx.lifecycle.Observer
-
-class CombinedLiveData<T, K, S>(
-    source1: LiveData<T>,
-    source2: LiveData<K>,
-    private val combine: (data1: T?, data2: K?) -> S
-) : MediatorLiveData<S>() {
-
-    private var data1: T? = null
-    private var data2: K? = null
-
-    init {
-        super.addSource(source1) { t ->
-            data1 = t
-            value = combine(data1, data2)
-        }
-        super.addSource(source2) { k ->
-            data2 = k
-            value = combine(data1, data2)
-        }
-    }
-
-    override fun <S : Any?> addSource(source: LiveData<S>, onChanged: Observer<in S>) {
-        throw UnsupportedOperationException()
-    }
-
-    override fun <T : Any?> removeSource(toRemote: LiveData<T>) {
-        throw UnsupportedOperationException()
-    }
-
-}
diff --git a/taler-kotlin-common/src/main/java/net/taler/common/ContractTerms.kt b/taler-kotlin-common/src/main/java/net/taler/common/ContractTerms.kt
deleted file mode 100644
index b891ef7..0000000
--- a/taler-kotlin-common/src/main/java/net/taler/common/ContractTerms.kt
+++ /dev/null
@@ -1,91 +0,0 @@
-/*
- * 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 androidx.annotation.RequiresApi
-import com.fasterxml.jackson.annotation.JsonIgnore
-import com.fasterxml.jackson.annotation.JsonIgnoreProperties
-import com.fasterxml.jackson.annotation.JsonInclude
-import com.fasterxml.jackson.annotation.JsonInclude.Include.NON_EMPTY
-import com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL
-import com.fasterxml.jackson.annotation.JsonProperty
-import kotlinx.serialization.SerialName
-import kotlinx.serialization.Serializable
-import net.taler.common.TalerUtils.getLocalizedString
-
-@Serializable
-@JsonIgnoreProperties(ignoreUnknown = true)
-data class ContractTerms(
-    val summary: String,
-    @SerialName("summary_i18n")
-    val summaryI18n: Map<String, String>? = null,
-    val amount: Amount,
-    @SerialName("fulfillment_url")
-    val fulfillmentUrl: String,
-    val products: List<ContractProduct>
-)
-
-@JsonInclude(NON_NULL)
-abstract class Product {
-    @get:JsonProperty("product_id")
-    abstract val productId: String?
-    abstract val description: String
-
-    @get:JsonProperty("description_i18n")
-    abstract val descriptionI18n: Map<String, String>?
-    abstract val price: Amount
-
-    @get:JsonProperty("delivery_location")
-    abstract val location: String?
-    abstract val image: String?
-
-    @get:JsonIgnore
-    val localizedDescription: String
-        @RequiresApi(26)
-        get() = getLocalizedString(descriptionI18n, description)
-}
-
-@Serializable
-data class ContractProduct(
-    @SerialName("product_id")
-    override val productId: String? = null,
-    override val description: String,
-    @SerialName("description_i18n")
-    override val descriptionI18n: Map<String, String>? = null,
-    override val price: Amount,
-    @SerialName("delivery_location")
-    override val location: String? = null,
-    override val image: String? = null,
-    val quantity: Int
-) : Product() {
-    @get:JsonIgnore
-    val totalPrice: Amount by lazy {
-        price * quantity
-    }
-}
-
-data class ContractMerchant(
-    val name: String
-)
-
-@Serializable
-@JsonInclude(NON_EMPTY)
-class Timestamp(
-    @SerialName("t_ms")
-    @JsonProperty("t_ms")
-    val ms: Long
-)
diff --git a/taler-kotlin-common/src/main/java/net/taler/common/Event.kt b/taler-kotlin-common/src/main/java/net/taler/common/Event.kt
deleted file mode 100644
index 779247f..0000000
--- a/taler-kotlin-common/src/main/java/net/taler/common/Event.kt
+++ /dev/null
@@ -1,51 +0,0 @@
-/*
- * 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 androidx.lifecycle.LiveData
-import androidx.lifecycle.Observer
-import java.util.concurrent.atomic.AtomicBoolean
-
-/**
- * Used as a wrapper for data that is exposed via a [LiveData] that represents an one-time event.
- */
-open class Event<out T>(private val content: T) {
-
-    private val isConsumed = AtomicBoolean(false)
-
-    /**
-     * Returns the content and prevents its use again.
-     */
-    fun getIfNotConsumed(): T? {
-        return if (isConsumed.compareAndSet(false, true)) content else null
-    }
-
-}
-
-fun <T> T.toEvent() = Event(this)
-
-/**
- * An [Observer] for [Event]s, simplifying the pattern of checking if the [Event]'s content has
- * already been consumed.
- *
- * [onEvent] is *only* called if the [Event]'s contents has not been consumed.
- */
-class EventObserver<T>(private val onEvent: (T) -> Unit) : Observer<Event<T>> {
-    override fun onChanged(event: Event<T>?) {
-        event?.getIfNotConsumed()?.let { onEvent(it) }
-    }
-}
diff --git a/taler-kotlin-common/src/main/java/net/taler/common/NfcManager.kt b/taler-kotlin-common/src/main/java/net/taler/common/NfcManager.kt
deleted file mode 100644
index 11e1e1e..0000000
--- a/taler-kotlin-common/src/main/java/net/taler/common/NfcManager.kt
+++ /dev/null
@@ -1,234 +0,0 @@
-/*
- * 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 android.app.Activity
-import android.content.Context
-import android.nfc.NfcAdapter
-import android.nfc.NfcAdapter.FLAG_READER_NFC_A
-import android.nfc.NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK
-import android.nfc.NfcAdapter.getDefaultAdapter
-import android.nfc.Tag
-import android.nfc.tech.IsoDep
-import android.util.Log
-import net.taler.common.ByteArrayUtils.hexStringToByteArray
-import org.json.JSONObject
-import java.io.ByteArrayOutputStream
-import java.net.URL
-import javax.net.ssl.HttpsURLConnection
-
-@Suppress("unused")
-private const val TALER_AID = "A0000002471001"
-
-class NfcManager : NfcAdapter.ReaderCallback {
-
-    companion object {
-        const val TAG = "taler-merchant"
-
-        /**
-         * Returns true if NFC is supported and false otherwise.
-         */
-        fun hasNfc(context: Context): Boolean {
-            return getNfcAdapter(context) != null
-        }
-
-        /**
-         * Enables NFC reader mode. Don't forget to call [stop] afterwards.
-         */
-        fun start(activity: Activity, nfcManager: NfcManager) {
-            getNfcAdapter(activity)?.enableReaderMode(activity, nfcManager, nfcManager.flags, null)
-        }
-
-        /**
-         * Disables NFC reader mode. Call after [start].
-         */
-        fun stop(activity: Activity) {
-            getNfcAdapter(activity)?.disableReaderMode(activity)
-        }
-
-        private fun getNfcAdapter(context: Context): NfcAdapter? {
-            return getDefaultAdapter(context)
-        }
-    }
-
-    private val flags = FLAG_READER_NFC_A or FLAG_READER_SKIP_NDEF_CHECK
-
-    private var tagString: String? = null
-    private var currentTag: IsoDep? = null
-
-    fun setTagString(tagString: String) {
-        this.tagString = tagString
-    }
-
-    override fun onTagDiscovered(tag: Tag?) {
-
-        Log.v(TAG, "tag discovered")
-
-        val isoDep = IsoDep.get(tag)
-        isoDep.connect()
-
-        currentTag = isoDep
-
-        isoDep.transceive(apduSelectFile())
-
-        val tagString: String? = tagString
-        if (tagString != null) {
-            isoDep.transceive(apduPutTalerData(1, tagString.toByteArray()))
-        }
-
-        // FIXME: use better pattern for sleeps in between requests
-        // -> start with fast polling, poll more slowly if no requests are coming
-
-        while (true) {
-            try {
-                val reqFrame = isoDep.transceive(apduGetData())
-                if (reqFrame.size < 2) {
-                    Log.v(TAG, "request frame too small")
-                    break
-                }
-                val req = ByteArray(reqFrame.size - 2)
-                if (req.isEmpty()) {
-                    continue
-                }
-                reqFrame.copyInto(req, 0, 0, reqFrame.size - 2)
-                val jsonReq = JSONObject(req.toString(Charsets.UTF_8))
-                val reqId = jsonReq.getInt("id")
-                Log.v(TAG, "got request $jsonReq")
-                val jsonInnerReq = jsonReq.getJSONObject("request")
-                val method = jsonInnerReq.getString("method")
-                val urlStr = jsonInnerReq.getString("url")
-                Log.v(TAG, "url '$urlStr'")
-                Log.v(TAG, "method '$method'")
-                val url = URL(urlStr)
-                val conn: HttpsURLConnection = url.openConnection() as HttpsURLConnection
-                conn.setRequestProperty("Accept", "application/json")
-                conn.connectTimeout = 5000
-                conn.doInput = true
-                when (method) {
-                    "get" -> {
-                        conn.requestMethod = "GET"
-                    }
-                    "postJson" -> {
-                        conn.requestMethod = "POST"
-                        conn.doOutput = true
-                        conn.setRequestProperty("Content-Type", "application/json; utf-8")
-                        val body = jsonInnerReq.getString("body")
-                        conn.outputStream.write(body.toByteArray(Charsets.UTF_8))
-                    }
-                    else -> {
-                        throw Exception("method not supported")
-                    }
-                }
-                Log.v(TAG, "connecting")
-                conn.connect()
-                Log.v(TAG, "connected")
-
-                val statusCode = conn.responseCode
-                val tunnelResp = JSONObject()
-                tunnelResp.put("id", reqId)
-                tunnelResp.put("status", conn.responseCode)
-
-                if (statusCode == 200) {
-                    val stream = conn.inputStream
-                    val httpResp = stream.buffered().readBytes()
-                    tunnelResp.put("responseJson", JSONObject(httpResp.toString(Charsets.UTF_8)))
-                }
-
-                Log.v(TAG, "sending: $tunnelResp")
-
-                isoDep.transceive(apduPutTalerData(2, tunnelResp.toString().toByteArray()))
-            } catch (e: Exception) {
-                Log.v(TAG, "exception during NFC loop: $e")
-                break
-            }
-        }
-
-        isoDep.close()
-    }
-
-    private fun writeApduLength(stream: ByteArrayOutputStream, size: Int) {
-        when {
-            size == 0 -> {
-                // No size field needed!
-            }
-            size <= 255 -> // One byte size field
-                stream.write(size)
-            size <= 65535 -> {
-                stream.write(0)
-                // FIXME: is this supposed to be little or big endian?
-                stream.write(size and 0xFF)
-                stream.write((size ushr 8) and 0xFF)
-            }
-            else -> throw Error("payload too big")
-        }
-    }
-
-    private fun apduSelectFile(): ByteArray {
-        return hexStringToByteArray("00A4040007A0000002471001")
-    }
-
-    private fun apduPutData(payload: ByteArray): ByteArray {
-        val stream = ByteArrayOutputStream()
-
-        // Class
-        stream.write(0x00)
-
-        // Instruction 0xDA = put data
-        stream.write(0xDA)
-
-        // Instruction parameters
-        // (proprietary encoding)
-        stream.write(0x01)
-        stream.write(0x00)
-
-        writeApduLength(stream, payload.size)
-
-        stream.write(payload)
-
-        return stream.toByteArray()
-    }
-
-    private fun apduPutTalerData(talerInst: Int, payload: ByteArray): ByteArray {
-        val realPayload = ByteArrayOutputStream()
-        realPayload.write(talerInst)
-        realPayload.write(payload)
-        return apduPutData(realPayload.toByteArray())
-    }
-
-    private fun apduGetData(): ByteArray {
-        val stream = ByteArrayOutputStream()
-
-        // Class
-        stream.write(0x00)
-
-        // Instruction 0xCA = get data
-        stream.write(0xCA)
-
-        // Instruction parameters
-        // (proprietary encoding)
-        stream.write(0x01)
-        stream.write(0x00)
-
-        // Max expected response size, two
-        // zero bytes denotes 65536
-        stream.write(0x0)
-        stream.write(0x0)
-
-        return stream.toByteArray()
-    }
-
-}
diff --git a/taler-kotlin-common/src/main/java/net/taler/common/QrCodeManager.kt b/taler-kotlin-common/src/main/java/net/taler/common/QrCodeManager.kt
deleted file mode 100644
index e2a9a55..0000000
--- a/taler-kotlin-common/src/main/java/net/taler/common/QrCodeManager.kt
+++ /dev/null
@@ -1,42 +0,0 @@
-/*
- * 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 android.graphics.Bitmap
-import android.graphics.Bitmap.Config.RGB_565
-import android.graphics.Color.BLACK
-import android.graphics.Color.WHITE
-import com.google.zxing.BarcodeFormat.QR_CODE
-import com.google.zxing.qrcode.QRCodeWriter
-
-object QrCodeManager {
-
-    fun makeQrCode(text: String, size: Int = 256): Bitmap {
-        val qrCodeWriter = QRCodeWriter()
-        val bitMatrix = qrCodeWriter.encode(text, QR_CODE, size, size)
-        val height = bitMatrix.height
-        val width = bitMatrix.width
-        val bmp = Bitmap.createBitmap(width, height, RGB_565)
-        for (x in 0 until width) {
-            for (y in 0 until height) {
-                bmp.setPixel(x, y, if (bitMatrix.get(x, y)) BLACK else WHITE)
-            }
-        }
-        return bmp
-    }
-
-}
diff --git a/taler-kotlin-common/src/main/java/net/taler/common/TalerUtils.kt b/taler-kotlin-common/src/main/java/net/taler/common/TalerUtils.kt
deleted file mode 100644
index 444caa4..0000000
--- a/taler-kotlin-common/src/main/java/net/taler/common/TalerUtils.kt
+++ /dev/null
@@ -1,58 +0,0 @@
-/*
- * 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 androidx.annotation.RequiresApi
-import androidx.core.os.LocaleListCompat
-import java.util.*
-import kotlin.collections.ArrayList
-
-object TalerUtils {
-
-    @RequiresApi(26)
-    fun getLocalizedString(map: Map<String, String>?, default: String): String {
-        // just return the default, if it is the only element
-        if (map == null) return default
-        // create a priority list of language ranges from system locales
-        val locales = LocaleListCompat.getDefault()
-        val priorityList = ArrayList<Locale.LanguageRange>(locales.size())
-        for (i in 0 until locales.size()) {
-            priorityList.add(Locale.LanguageRange(locales[i].toLanguageTag()))
-        }
-        // create a list of locales available in the given map
-        val availableLocales = map.keys.mapNotNull {
-            if (it == "_") return@mapNotNull null
-            val list = it.split("_")
-            when (list.size) {
-                1 -> Locale(list[0])
-                2 -> Locale(list[0], list[1])
-                3 -> Locale(list[0], list[1], list[2])
-                else -> null
-            }
-        }
-        val match = Locale.lookup(priorityList, availableLocales)
-        return match?.toString()?.let { map[it] } ?: default
-    }
-
-}
-
-/**
- * Returns the current time in milliseconds epoch rounded to nearest seconds.
- */
-fun now(): Long {
-    return ((System.currentTimeMillis() + 500) / 1000) * 1000
-}
diff --git a/taler-kotlin-common/src/main/res/drawable/selectable_background.xml b/taler-kotlin-common/src/main/res/drawable/selectable_background.xml
deleted file mode 100644
index 3c383a8..0000000
--- a/taler-kotlin-common/src/main/res/drawable/selectable_background.xml
+++ /dev/null
@@ -1,21 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<!--
-  ~ 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/>
-  -->
-
-<selector xmlns:android="http://schemas.android.com/apk/res/android">
-    <item android:drawable="@color/selectedBackground" android:state_activated="true" />
-    <item android:drawable="@android:color/transparent" />
-</selector>
diff --git a/taler-kotlin-common/src/main/res/values-night/colors.xml b/taler-kotlin-common/src/main/res/values-night/colors.xml
deleted file mode 100644
index 10bdbb9..0000000
--- a/taler-kotlin-common/src/main/res/values-night/colors.xml
+++ /dev/null
@@ -1,5 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<resources>
-    <color name="highlightedBackground">#2E2E2E</color>
-    <color name="selectedBackground">#363636</color>
-</resources>
diff --git a/taler-kotlin-common/src/main/res/values/colors.xml b/taler-kotlin-common/src/main/res/values/colors.xml
deleted file mode 100644
index c916442..0000000
--- a/taler-kotlin-common/src/main/res/values/colors.xml
+++ /dev/null
@@ -1,24 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<!--
-  ~ 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/>
-  -->
-
-<resources>
-    <color name="highlightedBackground">#E4E4E4</color>
-    <color name="selectedBackground">#DADADA</color>
-
-    <color name="green">#388E3C</color>
-    <color name="red">#C62828</color>
-</resources>
diff --git a/taler-kotlin-common/src/main/res/values/strings.xml b/taler-kotlin-common/src/main/res/values/strings.xml
deleted file mode 100644
index a5b1df1..0000000
--- a/taler-kotlin-common/src/main/res/values/strings.xml
+++ /dev/null
@@ -1,21 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?><!--
-  ~ 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/>
-  -->
-
-<resources>
-    <string name="version_invalid">Invalid version. Please try again later!</string>
-    <string name="version_too_old">App too old. Please upgrade!</string>
-    <string name="version_too_new">Service outdated. Please wait until it gets upgraded.</string>
-</resources>
diff --git a/taler-kotlin-common/src/nativeMain/kotlin/net/taler/common/Time.kt b/taler-kotlin-common/src/nativeMain/kotlin/net/taler/common/Time.kt
new file mode 100644
index 0000000..8a4091a
--- /dev/null
+++ b/taler-kotlin-common/src/nativeMain/kotlin/net/taler/common/Time.kt
@@ -0,0 +1,23 @@
+/*
+ * 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.system.getTimeMillis
+
+actual fun nowMillis(): Long {
+    return getTimeMillis()
+}