encodeJson - encodes a JsonValue to JSON string

Author: konnik

lib/src/main/kotlin/konnik/json/encode/Encode.kt

@@ -2,6 +2,46 @@ package konnik.json.encode
 
 import konnik.json.JsonValue
 
+/**
+ * Encodes a [JsonValue] as JSON string.
+ */
+fun encodeJson(json: JsonValue): String =
+    when (json) {
+        is JsonValue.Null -> "null"
+        is JsonValue.Bool -> if (json.value) "true" else "false"
+        is JsonValue.Num -> json.value.toString()
+        is JsonValue.Str -> "\"${escapeJsonString(json.value)}\""
+        is JsonValue.Array -> json.items.joinToString(
+            prefix = "[",
+            separator = ",",
+            postfix = "]",
+            transform = ::encodeJson
+        )
+
+        is JsonValue.Object -> json.members.entries.joinToString(
+            prefix = "{", separator = ",", postfix = "}"
+        ) { (key, value) ->
+            "\"${escapeJsonString(key)}\":${encodeJson(value)}"
+        }
+    }
+
+private fun escapeJsonString(value: String): String {
+    val sb = StringBuilder()
+    value.forEach {
+        when (it) {
+            '"' -> sb.append("\\$it")
+            '\\' -> sb.append("\\$it")
+            '\b' -> sb.append("\\b")
+            '\u000C' -> sb.append("\\f")
+            '\n' -> sb.append("\\n")
+            '\r' -> sb.append("\\r")
+            '\t' -> sb.append("\\t")
+            else -> sb.append(it)
+        }
+    }
+    return sb.toString()
+}
+
 // Basic functions for encoding native Kotlin types into JsonValue's.
 
 /**

lib/src/test/kotlin/konnik/json/encode/EncodeKtTest.kt

@@ -40,4 +40,28 @@ class EncodeKtTest {
 
         assertEquals(expectedValue, myObj)
     }
+
+    @Test
+    fun `encodeJson parseJson round trip`() {
+        val myObj = obj {
+            "a" to "Sausage"
+            "b" to 3.14E-99
+            "c" to -314
+            "d" to true
+            "e" to nullValue()
+            "f" to array("one", "two", "three")
+            "g" to obj {
+                "inner" to "JSON is fantastic!!!"
+            }
+            "h" to array(str("a string"), number(42), bool(false), nullValue())
+            "i" to "escaped\"\\\t\n\b\r\u000Cstring"
+            "j" to "unicode: ©\uD83E\uDD21"
+        }
+
+        val json = encodeJson(myObj)
+        val myObj2 = parseJson(json)
+
+        assertEquals(myObj, myObj2)
+
+    }
 }