Improve readability in Parser, parse numeric commands, extract logic into body of abstract parent class

src/main/kotlin/com/shr4pnel/ferretirc/net/MessageParser.kt

@@ -9,66 +9,70 @@ import org.slf4j.helpers.NOPLogger
 
 class MessageParser(val incoming: Channel<String>) {
     val incomingParsedMessages = Channel<ServerMessage>()
-
-    private companion object MessageBuilder {
-        fun getTrailingParameterIndex(params: List<String>) = params.indexOfLast { it.startsWith(":") }
-
-        sealed interface Command {
-            fun toServerMessage(): ServerMessage
-
-            class NamedCommand(val name: String, val parameters: List<String>) : Command {
-                override fun toServerMessage(): ServerMessage {
-                    logger.debug { "Parsing ${name.toUpperCasePreservingASCIIRules()}, with params $parameters" }
-
-                    return when (name.toUpperCasePreservingASCIIRules()) {
-                        // PONG :PREFIX COMMAND HOSTNAME :TOKEN
-                        "PONG" -> {
-                            val tokenIndex = getTrailingParameterIndex(parameters)
-                            if (tokenIndex != -1) ServerMessage.Pong(
-                                parameters.subList(tokenIndex, parameters.size).joinToString(" ").removePrefix(":")
-                            )
-                            else ServerMessage.Pong()
-                        }
-                        // MODE :PREFIX NICK :MODES
-                        "MODE" -> {
-                            ServerMessage.Mode(parameters.first(), parameters.last().removePrefix(":")) // TODO MODE, CHANMODE, LOCALMODE
-                        }
-
-                        "NOTICE", "PRIVMSG" -> {
-                            val cmd = name.toUpperCasePreservingASCIIRules()
-                            val trailingIndex = getTrailingParameterIndex(parameters)
-                            if (trailingIndex < 1) {
-                                logger.warn { "Received malformed $cmd. Returning unimplemented as fallback." }
-                                return ServerMessage.UNIMPLEMENTED("$cmd ${parameters.joinToString(" ")}")
-                            }
-                            val targets = parameters.subList(0, trailingIndex - 1)
-                            if (cmd == "NOTICE")
-                                ServerMessage.Notice(targets, "")
-                            else
-                                ServerMessage.PrivMsg(targets, "")
-
-                        }
-
-                        else -> {
-                            logger.warn { "$name left unparsed" }
-                            ServerMessage.UNIMPLEMENTED("$name ${parameters.joinToString(" ")}")
-                        }
-                    }
-                }
-            }
     private val logger = if (Helpers.enableLogging) KotlinLogging.logger {} else KotlinLogging.logger(NOPLogger.NOP_LOGGER)
 
-            class NumericCommand(val number: Int, val parameters: List<String>?) : Command {
+    class MessageBuilder {
-                override fun toServerMessage(): ServerMessage {
-                    return ServerMessage.UNIMPLEMENTED("$number ${parameters?.joinToString(" ")}")
-                }
-            }
-        }
-
         private var tags: String? = null
         private var prefix: String? = null
         private lateinit var command: Command
 
+        abstract class Command(open val command: String, open val parameters: List<String>) {
+            abstract fun toServerMessage(): ServerMessage
+            fun getTrailingParameterIndex() = parameters.indexOfFirst { it.startsWith(":") }
+
+            fun getTrailingParameterString() =
+                parameters
+                    .subList(getTrailingParameterIndex(), parameters.size)
+                    .joinToString(" ")
+                    .removePrefix(":")
+
+            fun getNonTrailingParameterString() =
+                parameters
+                    .subList(0, getTrailingParameterIndex())
+                    .joinToString(" ")
+                    .removePrefix(":")
+
+            fun getNonTrailingParameters() = getNonTrailingParameterString().split(" ")
+
+            class NamedCommand(override val command: String, override val parameters: List<String>) : Command(command, parameters) {
+                override fun toServerMessage() = when (command.uppercase()) {
+                    "PONG" -> ServerMessage.Pong(getTrailingParameterString().removePrefix(":"))
+                    "MODE" -> ServerMessage.Mode(
+                        parameters.first(),
+                        parameters.last().removePrefix(":")
+                    ) // TODO MODE, CHANMODE, LOCALMODE
+
+                    "NOTICE" -> ServerMessage.Notice(
+                        getNonTrailingParameters(),
+                        getTrailingParameterString()
+                    )
+
+                    "PRIVMSG" -> ServerMessage.PrivMsg(
+                        getNonTrailingParameters(),
+                        getTrailingParameterString()
+                    )
+
+                    else -> {
+                        ServerMessage.UNIMPLEMENTED("$command ${parameters.joinToString(" ")}")
+                    }
+                }
+            }
+
+            class NumericCommand(override val command: String, override val parameters: List<String>) : Command(command, parameters) {
+                override fun toServerMessage() = when (command.toInt()) {
+                    5 -> ServerMessage.Numeric.RPL_ISUPPORT(getNonTrailingParameterString())
+                    321 -> ServerMessage.Numeric.RPL_LISTSTART()
+                    322 -> ServerMessage.Numeric.RPL_LIST(
+                        parameters[1],
+                        parameters[2].toInt(),
+                        getTrailingParameterString()
+                    )
+                    323 -> ServerMessage.Numeric.RPL_LISTEND()
+                    else -> ServerMessage.UNIMPLEMENTED(parameters.toString())
+                }
+            }
+        }
+
         /**
          * Messages have this format, as rough ABNF:
          *
@@ -86,15 +90,30 @@ class MessageParser(val incoming: Channel<String>) {
          *
          * parameters: If it exists, data relevant to this specific command.
          *
-         * ignoring tags for now ;-;.. still making space for them
+         * ===================
+         *
+         * Convert line from server into tokens split on strings and remove elements that belong
+         * to different segments of the IRC message e.g. tags, prefixes etc
          */
         fun build(commandList: List<String>): ServerMessage {
             val tokens = commandList.toMutableList()
-            tags = if (tokens.first().startsWith("@")) tokens.removeFirst() else null
+
-            prefix = if (tokens.first().startsWith(":")) tokens.removeFirst() else null
+            // remove tags from strlist if present
+            tags = if (tokens.first().startsWith("@")) {
+                tokens.removeFirst()
+            } else null
+
+            // remove client prefix (nick&opt hostname) if present
+            prefix = if (tokens.first().startsWith(":")) {
+                tokens.removeFirst()
+            } else null
+
+            // get command e.g. PING
             val commandStr = tokens.removeFirst()
-            command = if (commandStr.toIntOrNull() != null) Command.NumericCommand(commandStr.toInt(), tokens)
+
-            else Command.NamedCommand(commandStr, tokens)
+            // Check if command is a numeric (RPL/ERR) or named
+            command = if (commandStr.toIntOrNull() == null) Command.NamedCommand(commandStr, tokens)
+            else Command.NumericCommand(commandStr, tokens)
 
             return command.toServerMessage()
         }
@@ -103,9 +122,11 @@ class MessageParser(val incoming: Channel<String>) {
     }
 
     suspend fun start() {
+
+        val builder = MessageBuilder()
         for (msg in incoming) {
-            incomingParsedMessages.send(build(msg))
             logger.trace { "Receiving: $msg" }
+            incomingParsedMessages.send(builder.build(msg))
         }
     }
 }