refactor: move MiniFhir/MedicalData parsing from Jackson to Kotlin Serialization

Replace the Jackson-based FHIR resource parser with kotlinx.serialization.
The `resourceType` polymorphism is now handled by a JsonContentPolymorphicSerializer
that dispatches to the modeled types (Practitioner, Patient, Bundle,
VisionPrescription) and falls back to a new UnknownResource for anything else,
so a Bundle mixing known and unknown resources still parses.

The reader is lenient (ignoreUnknownKeys, isLenient, explicitNulls=false,
coerceInputValues) so we parse what we can and tolerate the missing or extra
fields that many FHIR implementations add.

Adds MiniFhirTest covering the vision-prescription bundle, extra/unknown field
tolerance, unknown-resourceType fallback, mixed bundles, and garbage input.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MUeR8YFNHvBELCaLRDTpCn

amethyst/src/main/java/com/vitorpamplona/amethyst/model/MiniFhir.kt

@@ -21,51 +21,71 @@
 package com.vitorpamplona.amethyst.model
 
 import androidx.compose.runtime.Stable
-import com.fasterxml.jackson.annotation.JsonSubTypes
-import com.fasterxml.jackson.annotation.JsonTypeInfo
-import com.fasterxml.jackson.databind.DeserializationFeature
-import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
-import com.fasterxml.jackson.module.kotlin.readValue
 import com.vitorpamplona.quartz.utils.Log
 import kotlinx.collections.immutable.ImmutableMap
 import kotlinx.collections.immutable.persistentMapOf
 import kotlinx.collections.immutable.toImmutableMap
+import kotlinx.serialization.DeserializationStrategy
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.JsonContentPolymorphicSerializer
+import kotlinx.serialization.json.JsonElement
+import kotlinx.serialization.json.jsonObject
+import kotlinx.serialization.json.jsonPrimitive
 
-@JsonTypeInfo(
-    use = JsonTypeInfo.Id.NAME,
-    include = JsonTypeInfo.As.PROPERTY,
-    property = "resourceType",
-)
-@JsonSubTypes(
-    JsonSubTypes.Type(value = Practitioner::class, name = "Practitioner"),
-    JsonSubTypes.Type(value = Patient::class, name = "Patient"),
-    JsonSubTypes.Type(value = Bundle::class, name = "Bundle"),
-    JsonSubTypes.Type(value = VisionPrescription::class, name = "VisionPrescription"),
-)
+/**
+ * FHIR resources are polymorphic on the `resourceType` string. We only model the
+ * handful of types Amethyst renders; anything else (and any resource with a
+ * missing/unrecognized type) decodes into [UnknownResource] so a mixed [Bundle]
+ * never fails to parse just because it carries a type we don't know about.
+ */
+object ResourceSerializer : JsonContentPolymorphicSerializer<Resource>(Resource::class) {
+    override fun selectDeserializer(element: JsonElement): DeserializationStrategy<Resource> =
+        when (element.jsonObject["resourceType"]?.jsonPrimitive?.content) {
+            "Practitioner" -> Practitioner.serializer()
+            "Patient" -> Patient.serializer()
+            "Bundle" -> Bundle.serializer()
+            "VisionPrescription" -> VisionPrescription.serializer()
+            else -> UnknownResource.serializer()
+        }
+}
+
+@Serializable(with = ResourceSerializer::class)
 @Stable
-open class Resource(
-    var resourceType: String? = null,
-    var id: String = "",
-)
+abstract class Resource {
+    abstract val resourceType: String?
+    abstract val id: String
+}
 
+/** Fallback for any FHIR resourceType we don't model. */
+@Serializable
+@Stable
+class UnknownResource(
+    override val resourceType: String? = null,
+    override val id: String = "",
+) : Resource()
+
+@Serializable
 @Stable
 class Practitioner(
-    resourceType: String? = null,
-    id: String = "",
+    override val resourceType: String? = null,
+    override val id: String = "",
     var active: Boolean? = null,
     var name: ArrayList<HumanName> = arrayListOf(),
     var gender: String? = null,
-) : Resource(resourceType, id)
+) : Resource()
 
+@Serializable
 @Stable
 class Patient(
-    resourceType: String? = null,
-    id: String = "",
+    override val resourceType: String? = null,
+    override val id: String = "",
     var active: Boolean? = null,
     var name: ArrayList<HumanName> = arrayListOf(),
     var gender: String? = null,
-) : Resource(resourceType, id)
+) : Resource()
 
+@Serializable
 @Stable
 class HumanName(
     var use: String? = null,
@@ -75,19 +95,21 @@ class HumanName(
     fun assembleName(): String = given.joinToString(" ") + " " + family
 }
 
+@Serializable
 @Stable
 class Bundle(
-    resourceType: String? = null,
-    id: String = "",
+    override val resourceType: String? = null,
+    override val id: String = "",
     var type: String? = null,
     var created: String? = null,
     var entry: List<Resource> = arrayListOf(),
-) : Resource(resourceType, id)
+) : Resource()
 
+@Serializable
 @Stable
 class VisionPrescription(
-    resourceType: String? = null,
-    id: String = "",
+    override val resourceType: String? = null,
+    override val id: String = "",
     var status: String? = null,
     var created: String? = null,
     var patient: Reference? = Reference(),
@@ -95,7 +117,7 @@ class VisionPrescription(
     var dateWritten: String? = null,
     var prescriber: Reference? = Reference(),
     var lensSpecification: List<LensSpecification> = arrayListOf(),
-) : Resource(resourceType, id) {
+) : Resource() {
     fun glasses() = lensSpecification.filter { it.product == "lens" }
 
     fun contacts() = lensSpecification.filter { it.product == "contacts" }
@@ -109,6 +131,7 @@ class VisionPrescription(
     fun contactsLeftEyes() = lensSpecification.filter { it.product == "contacts" && it.eye == "left" }
 }
 
+@Serializable
 @Stable
 class LensSpecification(
     var product: String? = null,
@@ -129,12 +152,14 @@ class LensSpecification(
     var note: String? = null,
 )
 
+@Serializable
 @Stable
 class Prism(
     var amount: Double? = null,
     var base: String? = null,
 )
 
+@Serializable
 class Reference(
     var reference: String? = null,
 )
@@ -156,12 +181,22 @@ fun findReferenceInDb(
     }
 }
 
-fun parseResourceBundleOrNull(json: String): FhirElementDatabase? {
-    val mapper =
-        jacksonObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
+/**
+ * Lenient FHIR JSON reader: unknown keys are ignored (implementations routinely add
+ * their own fields) and missing keys fall back to the property defaults, so we parse
+ * as much of a resource as we can rather than rejecting the whole document.
+ */
+val FhirJson =
+    Json {
+        ignoreUnknownKeys = true
+        isLenient = true
+        explicitNulls = false
+        coerceInputValues = true
+    }
 
-    return try {
-        val resource = mapper.readValue<Resource>(json)
+fun parseResourceBundleOrNull(json: String): FhirElementDatabase? =
+    try {
+        val resource = FhirJson.decodeFromString(ResourceSerializer, json)
 
         val db =
             when (resource) {
@@ -182,4 +217,3 @@ fun parseResourceBundleOrNull(json: String): FhirElementDatabase? {
         Log.e("RenderEyeGlassesPrescription", "Parser error", e)
         null
     }
-}

amethyst/src/test/java/com/vitorpamplona/amethyst/model/MiniFhirTest.kt

@@ -0,0 +1,127 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.model
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class MiniFhirTest {
+    @Test
+    fun parsesVisionPrescriptionBundle() {
+        val json =
+            """
+            {"resourceType":"Bundle","id":"bundle-vision-test","type":"document","entry":[
+              {"resourceType":"Practitioner","id":"2","active":true,"name":[{"use":"official","family":"Careful","given":["Adam"]}],"gender":"male"},
+              {"resourceType":"Patient","id":"1","active":true,"name":[{"use":"official","family":"Duck","given":["Donald"]}],"gender":"male"},
+              {"resourceType":"VisionPrescription","id":"3","status":"active","created":"2014-06-15","patient":{"reference":"#1"},"dateWritten":"2014-06-15","prescriber":{"reference":"#2"},"lensSpecification":[
+                {"product":"lens","eye":"right","sphere":-2,"prism":{"amount":0.5,"base":"down"},"add":2},
+                {"product":"lens","eye":"left","sphere":-1,"cylinder":-0.5,"axis":180,"prism":{"amount":0.5,"base":"up"},"add":2}
+              ]}
+            ]}
+            """.trimIndent()
+
+        val result = parseResourceBundleOrNull(json)
+        assertNotNull(result)
+
+        val bundle = result!!.baseResource as Bundle
+        assertEquals(3, bundle.entry.size)
+
+        val patient = findReferenceInDb("#1", result.localDb) as Patient
+        assertEquals("Donald Duck", patient.name.first().assembleName())
+
+        val prescriber = findReferenceInDb("#2", result.localDb) as Practitioner
+        assertEquals("Adam Careful", prescriber.name.first().assembleName())
+
+        val vision = bundle.entry.filterIsInstance<VisionPrescription>().first()
+        assertEquals(2, vision.glasses().size)
+        assertEquals(-2.0, vision.glassesRightEyes().first().sphere!!, 0.001)
+        assertEquals(
+            "down",
+            vision
+                .glassesRightEyes()
+                .first()
+                .prism
+                ?.base,
+        )
+    }
+
+    @Test
+    fun ignoresUnknownAndExtraFields() {
+        // resourceType we don't model + extra top-level and nested fields that many
+        // implementations add. Should still parse the known bits, not throw.
+        val json =
+            """
+            {"resourceType":"VisionPrescription","id":"7","status":"active","meta":{"versionId":"1"},
+             "extraField":"whatever","lensSpecification":[
+               {"eye":"right","sphere":-1.25,"vendorSpecific":{"foo":"bar"},"tags":["a","b"]}
+             ]}
+            """.trimIndent()
+
+        val result = parseResourceBundleOrNull(json)
+        assertNotNull(result)
+
+        val vision = result!!.baseResource as VisionPrescription
+        assertEquals("active", vision.status)
+        assertEquals(-1.25, vision.lensSpecification.first().sphere!!, 0.001)
+    }
+
+    @Test
+    fun fallsBackForUnknownResourceType() {
+        val json = """{"resourceType":"Observation","id":"obs-1","valueQuantity":{"value":9.5}}"""
+
+        val result = parseResourceBundleOrNull(json)
+        assertNotNull(result)
+
+        val base = result!!.baseResource
+        assertTrue(base is UnknownResource)
+        assertEquals("obs-1", base!!.id)
+    }
+
+    @Test
+    fun keepsUnknownEntriesInsideBundle() {
+        // A Bundle mixing a known and an unknown resource must not fail wholesale.
+        val json =
+            """
+            {"resourceType":"Bundle","id":"b","entry":[
+              {"resourceType":"Observation","id":"obs","code":{"text":"bp"}},
+              {"resourceType":"Patient","id":"p","name":[{"family":"Doe","given":["Jane"]}]}
+            ]}
+            """.trimIndent()
+
+        val result = parseResourceBundleOrNull(json)
+        assertNotNull(result)
+
+        val bundle = result!!.baseResource as Bundle
+        assertEquals(2, bundle.entry.size)
+        assertTrue(bundle.entry.first() is UnknownResource)
+
+        val patient = findReferenceInDb("p", result.localDb) as Patient
+        assertEquals("Jane Doe", patient.name.first().assembleName())
+    }
+
+    @Test
+    fun returnsNullOnGarbage() {
+        assertNull(parseResourceBundleOrNull("not json at all"))
+    }
+}