package com.shr4pnel.ferretirc.net

import com.shr4pnel.ferretirc.net.messages.ServerMessage
import io.github.oshai.kotlinlogging.KotlinLogging
import io.ktor.util.toUpperCasePreservingASCIIRules
import kotlinx.coroutines.channels.Channel

class MessageParser(val incoming: Channel<String>) {
    private val logger = KotlinLogging.logger("MessageParser")
    val incomingParsedMessages = Channel<ServerMessage>()

    private companion object MessageBuilder {
        sealed interface Command {
            fun toServerMessage(): ServerMessage

            class NamedCommand(val name: String, val parameters: List<String>) : Command {
                override fun toServerMessage(): ServerMessage {
                    return when (name.toUpperCasePreservingASCIIRules()) {
                        // PONG :PREFIX COMMAND HOSTNAME :TOKEN
                        "PONG" -> {
                            val tokenIndex = parameters.indexOfLast { it.contains(":") }
                            if (tokenIndex != -1) ServerMessage.Pong(
                                parameters.subList(tokenIndex, parameters.size).joinToString(" ").removePrefix(":")
                            )
                            else ServerMessage.Pong()
                        }

                        else -> ServerMessage.UNIMPLEMENTED("$name ${parameters.joinToString(" ")}")
                    }
                }
            }

            class NumericCommand(val number: Int, val parameters: List<String>?) : Command {
                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

        /**
         * Messages have this format, as rough ABNF:
         *
         *   message         ::= ['@' <tags> SPACE] [':' <source> SPACE] <command> <parameters> <crlf>
         *   SPACE           ::=  %x20 *( %x20 )   ; space character(s)
         *   crlf            ::=  %x0D %x0A        ; "carriage return" "linefeed"
         *
         * The specific parts of an IRC message are:
         *
         * tags: Optional metadata on a message, starting with ('@', 0x40).
         *
         * source: Optional note of where the message came from, starting with (':', 0x3A).
         *
         * command: The specific command this message represents.
         *
         * parameters: If it exists, data relevant to this specific command.
         *
         * ignoring tags for now ;-;.. still making space for them
         */
        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
            val commandStr = tokens.removeFirst()
            command = if (commandStr.toIntOrNull() != null) Command.NumericCommand(commandStr.toInt(), tokens)
            else Command.NamedCommand(commandStr, tokens)

            return command.toServerMessage()
        }

        fun build(command: String) = build(command.split(" "))
    }

    suspend fun start() {
        for (msg in incoming) {
            logger.debug { msg }
            incomingParsedMessages.send(build(msg))
        }
    }
}