Pretty Print | Pretty JSON Stringify in Kotlin

pretty_json_stringify.kt

fun main() {
    fun prettyJsonStringify(anything: Any? = null, indent: String = "    "): String {
        var indentLevel = 0
        fun prettyJsonStringifyInner(anythingInner: Any?, indentInner: String): String {
            if (anythingInner == null) return "null"
            if (anythingInner is String) return "\"${anythingInner}\""
            if (anythingInner is Number || anythingInner is Boolean) return "${anythingInner}"
            if (anythingInner is MutableList<*>) {
                if (anythingInner.size == 0) return "[]"
                indentLevel += 1
                var result = "[\n${indentInner.repeat(indentLevel)}"
                for ((arrayItemIndex, arrayItem) in anythingInner.withIndex()) {
                    result += prettyJsonStringifyInner(arrayItem, indentInner)
                    if ((arrayItemIndex + 1) != anythingInner.size) result += ",\n${indentInner.repeat(indentLevel)}"
                }
                indentLevel -= 1
                result += "\n${indentInner.repeat(indentLevel)}]"
                return result
            }
            if (anythingInner is MutableMap<*, *>) {
                if (anythingInner.entries.size == 0) return "{}"
                indentLevel += 1
                var result = "{\n${indentInner.repeat(indentLevel)}"
                anythingInner.entries.forEachIndexed { entryIndex, entryItem ->
                    val objectKey = entryItem.key
                    val objectValue = entryItem.value
                    result += "\"${objectKey}\": ${prettyJsonStringifyInner(objectValue, indentInner)}"
                    if ((entryIndex + 1) != anythingInner.entries.size) result += ",\n${indentInner.repeat(indentLevel)}"
                }
                indentLevel -= 1
                result += "\n${indentInner.repeat(indentLevel)}}"
                return result
            }
            return "null"
        }
        return prettyJsonStringifyInner(anything, indent)
    }

    val products = mutableListOf<Any?>(
        mutableMapOf<String, Any?>(
            "id" to "P1",
            "name" to "bubble gum"
        ),
        mutableMapOf<String, Any?>(
            "id" to "P2",
            "name" to "potato chips"
        ),
    )
    println("products: ${prettyJsonStringify(products)}")
}