feat: add revenue helper class (#6)

main/java/com/amplitude/Amplitude.kt

@@ -3,6 +3,7 @@ package com.amplitude
 import com.amplitude.events.BaseEvent
 import com.amplitude.events.Identify
 import com.amplitude.events.Revenue
+import com.amplitude.events.RevenueEvent
 import com.amplitude.platform.Plugin
 import com.amplitude.platform.Timeline
 import com.amplitude.platform.plugins.AmplitudeDestination
@@ -75,8 +76,22 @@ open class Amplitude internal constructor(
         revenue(revenue)
     }
 
+    /**
+     * Create a Revenue object to hold your revenue data and properties,
+     * and log it as a revenue event using this method.
+     */
     fun revenue(revenue: Revenue) {
+        if (!revenue.isValid()) {
+            return
+        }
+        revenue(revenue.toRevenueEvent())
+    }
 
+    /**
+     * Log a Revenue Event
+     */
+    fun revenue(event: RevenueEvent) {
+        process(event)
     }
 
     fun process(event: BaseEvent) {

main/java/com/amplitude/events/BaseEvent.kt

@@ -3,7 +3,7 @@ package com.amplitude.events
 import org.json.JSONObject
 
 open class BaseEvent : EventOptions() {
-    lateinit var eventType: String
+    open lateinit var eventType: String
     var eventProperties: JSONObject? = null
     var userProperties: JSONObject? = null
     var groups:JSONObject? = null

main/java/com/amplitude/events/Revenue.kt

@@ -1,4 +1,113 @@
 package com.amplitude.events
 
+import org.json.JSONException
+import org.json.JSONObject
+
 class Revenue {
-}
+    /**
+     * The Product ID field.
+     */
+    var productId: String? = null
+        set(value) {
+            if (!value.isNullOrEmpty()) {
+                field = value
+            }
+        }
+
+    /**
+     * The Quantity field (defaults to 1).
+     */
+    var quantity: Int = 1
+        set(value) {
+            if (value > 0) {
+                field = value
+            }
+        }
+
+    /**
+     * The Price field (required).
+     */
+    var price: Double? = null
+        set(value) {
+            value?.let {
+                field = value
+            }
+        }
+
+    /**
+     * The Revenue Type field (optional).
+     */
+    var revenueType: String? = null
+
+    /**
+     * The Receipt field (required if you want to verify the revenue event).
+     */
+    private var receipt: String? = null
+
+    /**
+     * The Receipt Signature field (required if you want to verify the revenue event).
+     */
+    private var receiptSig: String? = null
+
+    /**
+     * The Revenue Event Properties field with (optional).
+     */
+    var properties: JSONObject? = null
+
+    /**
+     * The revenue amount
+     */
+    var revenue: Double? = null
+        set(value) {
+            value?.let {
+                field = value
+            }
+        }
+
+    companion object {
+        internal const val REVENUE_PRODUCT_ID = "\$productId"
+        internal const val REVENUE_QUANTITY = "\$quantity"
+        internal const val REVENUE_PRICE = "\$price"
+        internal const val REVENUE_TYPE = "\$revenueType"
+        internal const val REVENUE_RECEIPT = "\$receipt"
+        internal const val REVENUE_RECEIPT_SIG = "\$receiptSig"
+        internal const val REVENUE = "\$revenue"
+    }
+
+    /**
+     * Set the receipt and receipt signature. Both fields are required to verify the revenue event.
+     */
+    fun setReceipt(receipt: String, receiptSignature: String): Revenue {
+        this.receipt = receipt
+        receiptSig = receiptSignature
+        return this
+    }
+
+    /**
+     * Verifies that revenue object is valid and contains the required fields
+     */
+    fun isValid(): Boolean {
+        if (price == null) {
+            return false
+        }
+        return true
+    }
+
+    fun toRevenueEvent(): RevenueEvent {
+        val event = RevenueEvent()
+        val eventProperties = properties ?: JSONObject()
+        try {
+            eventProperties.put(REVENUE_PRODUCT_ID, productId)
+            eventProperties.put(REVENUE_QUANTITY, quantity)
+            eventProperties.put(REVENUE_PRICE, price)
+            eventProperties.put(REVENUE_TYPE, revenueType)
+            eventProperties.put(REVENUE_RECEIPT, receipt)
+            eventProperties.put(REVENUE_RECEIPT_SIG, receiptSig)
+            eventProperties.put(REVENUE, revenue)
+        } catch (e: JSONException) {
+            e.printStackTrace()
+        }
+        event.eventProperties = eventProperties
+        return event
+    }
+}

main/java/com/amplitude/events/RevenueEvent.kt

@@ -1,4 +1,7 @@
 package com.amplitude.events
 
+import com.amplitude.Constants
+
 class RevenueEvent : BaseEvent() {
+    override var eventType = Constants.AMP_REVENUE_EVENT
 }