Add Spectate command

Author: Rothes

bukkit/src/main/kotlin/io/github/rothes/esu/bukkit/module/EssentialCommandsModule.kt

@@ -10,7 +10,7 @@ object EssentialCommandsModule: BukkitModule<BaseModuleConfiguration, EssentialC
 
     init {
         listOf(
-            ClientLocale, DimensionTravel, Feed, Heal, Ip, IpGroup, Ping, PlayerChunkTickets, Speed, Suicide, TpChunk
+            ClientLocale, DimensionTravel, Feed, Heal, Ip, IpGroup, Ping, PlayerChunkTickets, Spectate, Speed, Suicide, TpChunk
         ).forEach { cmd -> registerFeature(cmd) }
     }
 

bukkit/src/main/kotlin/io/github/rothes/esu/bukkit/module/essentialcommands/Spectate.kt

@@ -0,0 +1,57 @@
+package io.github.rothes.esu.bukkit.module.essentialcommands
+
+import io.github.rothes.esu.bukkit.user.PlayerUser
+import io.github.rothes.esu.bukkit.util.ComponentBukkitUtils.player
+import io.github.rothes.esu.bukkit.util.ServerCompatibility.tp
+import io.github.rothes.esu.bukkit.util.scheduler.Scheduler.nextTick
+import io.github.rothes.esu.bukkit.util.scheduler.Scheduler.nextTickDeferred
+import io.github.rothes.esu.bukkit.util.version.adapter.TickThreadAdapter.Companion.checkTickThread
+import io.github.rothes.esu.core.command.annotation.ShortPerm
+import io.github.rothes.esu.core.configuration.data.MessageData
+import io.github.rothes.esu.core.configuration.data.MessageData.Companion.message
+import io.github.rothes.esu.core.module.configuration.FeatureToggle
+import org.bukkit.GameMode
+import org.bukkit.entity.Player
+import org.incendo.cloud.annotations.Argument
+import org.incendo.cloud.annotations.Command
+
+object Spectate: BaseCommand<FeatureToggle.DefaultTrue, Spectate.Lang>() {
+
+    override fun onEnable() {
+        registerCommands(object {
+            @Command("spectate <target>")
+            @ShortPerm
+            suspend fun spectate(sender: PlayerUser, @Argument("target") target: Player) {
+                val caller = sender.player
+                if (caller == target) {
+                    return sender.message(lang, { cannotSpectateSelf })
+                }
+                if (caller.gameMode != GameMode.SPECTATOR) {
+                    caller.nextTickDeferred {
+                        caller.gameMode = GameMode.SPECTATOR
+                    }.join()
+                }
+                target.nextTick {
+                    if (caller.checkTickThread())
+                        caller.spectatorTarget = target
+                    else {
+                        caller.tp(target.location) {
+                            caller.spectatorTarget = target
+                        }
+                    }
+                    sender.message(lang, { spectatingTarget }, player(target, "target"))
+                }
+            }
+        }) { parser ->
+            parser.registerBuilderDecorator {
+                it.senderType(PlayerUser::class.java)
+            }
+        }
+    }
+
+    data class Lang(
+        val cannotSpectateSelf: MessageData = "<ec>You cannot spectate yourself!".message,
+        val spectatingTarget: MessageData = "<pc>Spectating <pdc><target></pdc> now.".message,
+    )
+
+}

bukkit/src/main/kotlin/io/github/rothes/esu/bukkit/util/scheduler/Scheduler.kt

@@ -108,14 +108,18 @@ object Scheduler {
             BukkitTask(Bukkit.getScheduler().runTaskTimerAsynchronously(plugin, func, delayTicks, periodTicks))
     }
 
-    fun <T> Entity.nextTick(plugin: Plugin = esuPlugin, func: () -> T): CompletableDeferred<T> {
+    fun <T> Entity.nextTickDeferred(plugin: Plugin = esuPlugin, func: () -> T): CompletableDeferred<T> {
         val deferred = CompletableDeferred<T>()
         schedule(this, plugin) {
             deferred.complete(func())
         } ?: error("Failed to schedule task")
         return deferred
     }
 
+    fun Entity.nextTick(plugin: Plugin = esuPlugin, func: () -> Unit): ScheduledTask? {
+        return schedule(this, plugin, func)
+    }
+
     fun cancelTasks(plugin: Plugin = esuPlugin) {
         if (isFolia) {
             Bukkit.getGlobalRegionScheduler().cancelTasks(plugin)