Change: Make normalized path segments value classes

Author: acrusage-iaik

jsonpath4k/src/commonMain/kotlin/at/asitplus/jsonpath/core/NormalizedJsonPathSegment.kt

@@ -2,22 +2,32 @@ package at.asitplus.jsonpath.core
 
 import at.asitplus.jsonpath.generated.JsonPathLexer
 import at.asitplus.jsonpath.generated.JsonPathParser
+import kotlinx.serialization.KSerializer
 import kotlinx.serialization.Serializable
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+import kotlinx.serialization.json.JsonDecoder
+import kotlinx.serialization.json.JsonElement
+import kotlinx.serialization.json.jsonPrimitive
+import kotlinx.serialization.json.long
 import org.antlr.v4.kotlinruntime.CharStreams
 import org.antlr.v4.kotlinruntime.CommonTokenStream
 import org.antlr.v4.kotlinruntime.ListTokenSource
+import kotlin.jvm.JvmInline
 
 /**
  * specification: https://datatracker.ietf.org/doc/rfc9535/
  * date: 2024-02
  * section: 2.7.  Normalized Paths
  */
-@Serializable
+@Serializable(with = NormalizedJsonPathSegment.JsonDistinguishableSerializer::class)
 sealed interface NormalizedJsonPathSegment {
     fun toNormalizedJsonPathSegmentString(): String
 
     @Serializable
-    data class NameSegment(val memberName: String) : NormalizedJsonPathSegment {
+    @JvmInline
+    value class NameSegment(val memberName: String) : NormalizedJsonPathSegment {
         override fun toNormalizedJsonPathSegmentString() = toString()
 
         override fun toString(): String {
@@ -48,7 +58,8 @@ sealed interface NormalizedJsonPathSegment {
     }
 
     @Serializable
-    data class IndexSegment(val index: UInt) : NormalizedJsonPathSegment {
+    @JvmInline
+    value class IndexSegment(val index: UInt) : NormalizedJsonPathSegment {
         companion object {
             operator fun invoke(int: Int) = IndexSegment(int.also {
                 require(int >= 0)
@@ -61,4 +72,38 @@ sealed interface NormalizedJsonPathSegment {
             return "[$index]"
         }
     }
+
+    class JsonDistinguishableSerializer : KSerializer<NormalizedJsonPathSegment> {
+        override val descriptor: SerialDescriptor
+            get() = SerialDescriptor(
+                original = JsonElement.serializer().descriptor,
+                serialName = JsonDistinguishableSerializer::class.qualifiedName!!,
+            )
+
+        override fun serialize(
+            encoder: Encoder,
+            value: NormalizedJsonPathSegment
+        ) {
+            when (value) {
+                is IndexSegment -> encoder.encodeLong(value.index.toLong())
+                is NameSegment -> encoder.encodeString(value.memberName)
+            }
+        }
+
+        override fun deserialize(decoder: Decoder): NormalizedJsonPathSegment {
+            require(decoder is JsonDecoder) {
+                "Expected decoder to be ${JsonDecoder::class.qualifiedName!!}, but was `$decoder`."
+            }
+            val jsonElement = decoder.decodeJsonElement().jsonPrimitive
+            return if (jsonElement.isString) {
+                NameSegment(jsonElement.content)
+            } else {
+                IndexSegment(jsonElement.long.also {
+                    require(it >= 0) {
+                        "Expected index segment to be non-negative, but got `$it`."
+                    }
+                }.toUInt())
+            }
+        }
+    }
 }