KStarbound/src/main/kotlin/ru/dbotthepony/kstarbound/io/BinaryJson.kt

package ru.dbotthepony.kstarbound.io

import com.google.gson.*
import java.io.DataInputStream
import java.io.InputStream
import java.io.RandomAccessFile

/**
 * Represents interface to read binary json format by Chucklefish
 */
object BinaryJson {
	const val TYPE_NULL = 0x01
	const val TYPE_FLOAT = 0x02
	const val TYPE_DOUBLE = TYPE_FLOAT
	const val TYPE_BOOLEAN = 0x03

	/**
	 * На самом деле, variable int
	 */
	const val TYPE_INT = 0x04
	const val TYPE_STRING = 0x05
	const val TYPE_ARRAY = 0x06
	const val TYPE_OBJECT = 0x07

	fun readElement(reader: RandomAccessFile): JsonElement {
		return when (val id = reader.read()) {
			TYPE_NULL -> JsonNull.INSTANCE
			TYPE_DOUBLE -> JsonPrimitive(reader.readDouble())
			TYPE_BOOLEAN -> JsonPrimitive(reader.readBoolean())
			TYPE_INT -> {
				var read = reader.readVarLong()
				val sign = read and 0x1L
				read = read ushr 1

				if (sign == 1L) {
					JsonPrimitive(read - 1L)
				} else {
					JsonPrimitive(read)
				}
			}
			TYPE_STRING -> JsonPrimitive(reader.readASCIIString(reader.readVarInt()))
			TYPE_ARRAY -> readArray(reader)
			TYPE_OBJECT -> readObject(reader)
			else -> throw JsonParseException("Unknown element type $id")
		}
	}

	fun readElement(reader: DataInputStream): JsonElement {
		return when (val id = reader.read()) {
			TYPE_NULL -> JsonNull.INSTANCE
			TYPE_DOUBLE -> JsonPrimitive(reader.readDouble())
			TYPE_BOOLEAN -> JsonPrimitive(reader.readBoolean())
			TYPE_INT -> {
				var read = reader.readVarLong()
				val sign = read and 0x1L
				read = read ushr 1

				if (sign == 1L) {
					JsonPrimitive(read - 1L)
				} else {
					JsonPrimitive(read)
				}
			}
			TYPE_STRING -> JsonPrimitive(reader.readASCIIString(reader.readVarInt()))
			TYPE_ARRAY -> readArray(reader)
			TYPE_OBJECT -> readObject(reader)
			else -> throw JsonParseException("Unknown element type $id")
		}
	}

	fun readObject(reader: RandomAccessFile): JsonObject {
		val values = reader.readVarInt() - 1

		if (values == -1) {
			return JsonObject()
		}

		if (values < -1) {
			throw JsonParseException("Tried to read json object with $values elements in it")
		}

		val build = JsonObject()

		for (i in 0 .. values) {
			val key: String

			try {
				key = reader.readASCIIString(reader.readVarInt())
			} catch(err: Throwable) {
				throw JsonParseException("Reading json object at $i", err)
			}

			try {
				build.add(key, readElement(reader))
			} catch(err: Throwable) {
				throw JsonParseException("Reading json object at $i with name $key", err)
			}
		}

		return build
	}

	fun readObject(reader: DataInputStream): JsonObject {
		val values = reader.readVarInt() - 1

		if (values == -1) {
			return JsonObject()
		}

		if (values < -1) {
			throw JsonParseException("Tried to read json object with $values elements in it")
		}

		val build = JsonObject()

		for (i in 0 .. values) {
			val key: String

			try {
				key = reader.readASCIIString(reader.readVarInt())
			} catch(err: Throwable) {
				throw JsonParseException("Reading json object at $i", err)
			}

			try {
				build.add(key, readElement(reader))
			} catch(err: Throwable) {
				throw JsonParseException("Reading json object at $i with name $key", err)
			}
		}

		return build
	}

	fun readArray(reader: RandomAccessFile): JsonArray {
		val values = reader.readVarInt() - 1

		if (values == -1) {
			return JsonArray()
		}

		if (values < -1) {
			throw JsonParseException("Tried to read json array with $values elements in it")
		}

		val build = JsonArray()

		for (i in 0 .. values) {
			build.add(readElement(reader))
		}

		return build
	}

	fun readArray(reader: DataInputStream): JsonArray {
		val values = reader.readVarInt() - 1

		if (values == -1) {
			return JsonArray()
		}

		if (values < -1) {
			throw JsonParseException("Tried to read json array with $values elements in it")
		}

		val build = JsonArray()

		for (i in 0 .. values) {
			build.add(readElement(reader))
		}

		return build
	}
}

class VersionedJSON(var name: String = "Versioned JSON") {
	var isVersioned = false
	var version = 0
	var data: JsonElement? = null

	constructor(stream: DataInputStream) : this() {
		name = stream.readASCIIString(stream.readVarInt())
		isVersioned = stream.readBoolean()

		if (isVersioned) {
			version = stream.readInt()
		}

		data = BinaryJson.readElement(stream)
	}
}