Add Money

src/commonMain/kotlin/Money.kt

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+/*
+ * Copyright 2024 Kazimierz Pogoda / Xemantic
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.xemantic.ai.money
+
+import com.xemantic.ai.money.serialization.MoneyRatioSerializer
+import com.xemantic.ai.money.serialization.MoneySerializer
+import com.xemantic.ai.tool.schema.meta.Description
+import com.xemantic.ai.tool.schema.meta.Pattern
+import kotlinx.serialization.Serializable
+
+/**
+ * Represents a monetary amount, including small fractional amounts,
+ * so it can be used for expressing amounts like per token usage cost of LLM APIs,
+ * and real-time summarization of these costs.
+ *
+ * Note: This interface is not intended as a full implementation of
+ * arbitrary precision arithmetics related to monetary amounts.
+ *
+ * The [Money] is representing a multiplatform convenience wrapper around decimal
+ * arithmetics of each platform, to avoid floating point arithmetics
+ * in calculating total costs.
+ *
+ * The [Pattern] annotation, when serialized as a part of the JSON schema representing
+ * LLM tool use (function calling) input, will give the LLM a hint how to encode
+ * the financial value as a decimal number, without any string formatting.
+ */
+@Description("Represents a monetary amount with arbitrary precision and no currency information")
+@Pattern($$"""^-?\d*\.?\d+$""")
+@Serializable(MoneySerializer::class)
+public interface Money {
+
+  public operator fun plus(money: Money): Money
+
+  public operator fun minus(money: Money): Money
+
+  public operator fun times(money: Money): Money
+
+  public operator fun times(ratio: Ratio): Money
+
+  public operator fun compareTo(money: Money): Int
+
+  /**
+   * A ratio to multiply Money. I can be used for representing
+   * small ratios, like price per LLM token.
+   */
+  @Description("Represents a ratio used to multiply Money")
+  @Pattern($$"""^-?\d*\.?\d+$""")
+  @Serializable(MoneyRatioSerializer::class)
+  public interface Ratio {
+
+    public operator fun times(money: Money): Money
+
+    public companion object
+
+  }
+
+}
+
+public expect fun Money(amount: String): Money
+
+public expect val Money.Companion.ZERO: Money
+
+public expect val Money.Companion.ONE: Money
+
+public expect fun Money.Companion.Ratio(value: String): Money.Ratio
+
+public expect val Money.Ratio.Companion.ONE: Money.Ratio
+

src/commonMain/kotlin/serialization/MoneySerialization.kt

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+/*
+ * Copyright 2024 Kazimierz Pogoda / Xemantic
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.xemantic.ai.money.serialization
+
+import com.xemantic.ai.money.Money
+import com.xemantic.ai.money.Ratio
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.InternalSerializationApi
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.Serializer
+import kotlinx.serialization.descriptors.PrimitiveKind
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.descriptors.buildSerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+
+public object MoneySerializer : KSerializer<Money> {
+
+  // we can autogenerate a serializer which will retain annotations of serialized class
+  @OptIn(ExperimentalSerializationApi::class)
+  @Serializer(forClass = Money::class)
+  private object AutoSerializer
+
+  @OptIn(InternalSerializationApi::class, ExperimentalSerializationApi::class)
+  public override val descriptor: SerialDescriptor = buildSerialDescriptor(
+    serialName = AutoSerializer.descriptor.serialName,
+    kind = PrimitiveKind.STRING
+  ) {
+    annotations = AutoSerializer.descriptor.annotations
+  }
+
+  override fun serialize(encoder: Encoder, value: Money) {
+    encoder.encodeString(value.toString())
+  }
+
+  override fun deserialize(
+    decoder: Decoder
+  ): Money = Money(decoder.decodeString())
+
+}
+
+public object MoneyRatioSerializer : KSerializer<Money.Ratio> {
+
+  // we can autogenerate a serializer which will retain annotations of serialized class
+  @OptIn(ExperimentalSerializationApi::class)
+  @Serializer(forClass = Money.Ratio::class)
+  private object AutoSerializer
+
+  @OptIn(InternalSerializationApi::class, ExperimentalSerializationApi::class)
+  public override val descriptor: SerialDescriptor = buildSerialDescriptor(
+    serialName = AutoSerializer.descriptor.serialName,
+    kind = PrimitiveKind.STRING
+  ) {
+    annotations = AutoSerializer.descriptor.annotations
+  }
+
+  override fun serialize(encoder: Encoder, value: Money.Ratio) {
+    encoder.encodeString(value.toString())
+  }
+
+  override fun deserialize(
+    decoder: Decoder
+  ): Money.Ratio = Money.Ratio(decoder.decodeString())
+
+}

src/commonTest/kotlin/serialization/MoneyRatioSerializationTest.kt

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+/*
+ * Copyright 2024 Kazimierz Pogoda / Xemantic
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.xemantic.ai.money.serialization
+
+import com.xemantic.ai.money.Money
+import com.xemantic.ai.money.Ratio
+import com.xemantic.ai.money.test.shouldBe
+import com.xemantic.ai.money.test.testJson
+import com.xemantic.ai.tool.schema.meta.Description
+import com.xemantic.ai.tool.schema.meta.Pattern
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.encodeToString
+import kotlin.test.Test
+
+class MoneyRatioSerializationTest {
+
+  @Test
+  fun `Should serialize Money Ratio to JSON`() {
+    val ratio = Money.Ratio("0.000001")
+    testJson.encodeToString(ratio) shouldBe """"0.000001""""
+  }
+
+  @Test
+  fun `Should deserialize Money Ratio from JSON`() {
+    val json = """"0.000001""""
+    val ratio = testJson.decodeFromString<Money.Ratio>(json)
+    ratio shouldBe Money.Ratio("0.000001")
+  }
+
+  @Test
+  fun `Should preserve tool schema annotations of Money Ratio`() {
+    @OptIn(ExperimentalSerializationApi::class)
+    val meta = Money.Ratio.serializer().descriptor.annotations
+    (meta[0] as Description).value shouldBe "Represents a ratio used to multiply Money"
+    (meta[1] as Pattern).regex shouldBe $$"""^-?\d*\.?\d+$"""
+  }
+
+}