A json DSL builder for google gson library.

GsonDSL.kt

import com.google.gson.JsonArray
import com.google.gson.JsonElement
import com.google.gson.JsonObject
import com.google.gson.JsonPrimitive

@DslMarker
annotation class JsonMarker

@JsonMarker
fun json(block: JsonObjectBuilder.() -> Unit): JsonObject {
    return JsonObjectBuilder().apply(block).element
}

interface JsonBuilder<T : JsonElement> {
    val element: T
}

class JsonObjectBuilder : JsonBuilder<JsonObject> {
    override val element = JsonObject()

    infix fun String.value(n: Number) { element.addProperty(this, n) }
    infix fun String.value(b: Boolean) { element.addProperty(this, b) }
    infix fun String.value(str: String) { element.addProperty(this, str) }
    infix fun String.value(c: Char) { element.addProperty(this, c) }

    infix fun String.value(json: JsonObject) { element.add(this, json) }
    infix fun String.value(array: JsonArray) { element.add(this, array) }

    @JsonMarker
    fun array(block: JsonArrayBuilder.() -> Unit) = JsonArrayBuilder().apply(block).element
}

class JsonArrayBuilder : JsonBuilder<JsonArray> {
    override val element = JsonArray()

    operator fun String.unaryPlus() { element.add(JsonPrimitive(this)) }
    operator fun Boolean.unaryPlus() { element.add(JsonPrimitive(this)) }
    operator fun Number.unaryPlus() { element.add(JsonPrimitive(this)) }
    operator fun Char.unaryPlus() { element.add(JsonPrimitive(this)) }

    fun add(str: String) { +str }
    fun add(bool: Boolean) { +bool }
    fun add(number: Number) { +number }
    fun add(char: Char) { +char }

    @JsonMarker
    fun json(block: JsonObjectBuilder.() -> Unit) {
        element.add(JsonObjectBuilder().apply(block).element)
    }

    @JsonMarker
    fun array(block: JsonArrayBuilder.() -> Unit) = element.add(JsonArrayBuilder().apply(block).element)
}