Data model for paired portals

TODO

@@ -7,4 +7,4 @@
 * teleport everyone inside the portal, not just the person who closed the door
 * interrupt teleportation if portal is destroyed mid-teleportation
 * save any effects that would be overwritten by teleportation (including to disk!), and put them back when the player opens the door or arrives
-* add portal particles and ambient sounds to the teleporter
+* add portal particles and ambient sounds to the teleporter when portals are paired

build.gradle

@@ -2,6 +2,7 @@ plugins {
     id 'java'
     id 'org.jetbrains.kotlin.jvm' version '1.3.21'
     id "ru.endlesscode.bukkitgradle" version "0.8.1"
+    id 'com.google.protobuf' version '0.8.8'
 }
 
 group 'net.deliciousreya'
@@ -26,6 +27,7 @@ dependencies {
     compileOnly bukkit()
     compileOnly group: 'com.destroystokyo.paper', name: 'paper-api', version: '1.13.2-R0.1-SNAPSHOT'
     shade "com.google.guava:guava:27.1-jre"
+    shade "com.google.protobuf:protobuf-java:3.7.1"
     shade "org.jetbrains.kotlin:kotlin-stdlib-jdk8"
     testCompile group: 'junit', name: 'junit', version: '4.12'
 }

src/main/kotlin/net/deliciousreya/minecraftportal/MinecraftPortalPlugin.kt

@@ -1,8 +1,10 @@
 package net.deliciousreya.minecraftportal
 
 import com.destroystokyo.paper.event.block.BlockDestroyEvent
-import org.bukkit.Effect
+import net.deliciousreya.minecraftportal.model.DOOR_TYPES
-import org.bukkit.Material
+import net.deliciousreya.minecraftportal.model.PortalDataStore
+import net.deliciousreya.minecraftportal.model.PortalFrame
+import net.deliciousreya.minecraftportal.model.findPortalFrameConnectedTo
 import org.bukkit.Particle
 import org.bukkit.Sound
 import org.bukkit.block.Block
@@ -10,10 +12,8 @@ import org.bukkit.block.data.type.Door
 import org.bukkit.event.EventHandler
 import org.bukkit.event.Listener
 import org.bukkit.event.block.*
-import org.bukkit.event.entity.CreatureSpawnEvent
 import org.bukkit.event.entity.EntityChangeBlockEvent
 import org.bukkit.event.entity.EntityExplodeEvent
-import org.bukkit.event.player.PlayerBucketFillEvent
 import org.bukkit.event.player.PlayerInteractEvent
 import org.bukkit.plugin.java.JavaPlugin
 import org.bukkit.potion.PotionEffect
@@ -21,6 +21,8 @@ import org.bukkit.potion.PotionEffectType
 
 class MinecraftPortalPlugin() : JavaPlugin(), Listener
 {
+    val portals: PortalDataStore = PortalDataStore()
+
     override fun onEnable() {
         super.onEnable()
         logger.info("Loaded the portal plugin!")
@@ -30,12 +32,15 @@ class MinecraftPortalPlugin() : JavaPlugin(), Listener
     @EventHandler
     fun onBlockPlaced(e: BlockPlaceEvent) {
         if (e.block.type in PortalFrame.State.INACTIVE.allValidBlocks) {
-            val portalScanResults = findPortalFrameConnectedTo(e.block, PortalFrame.State.INACTIVE)
+            val newPortal = findPortalFrameConnectedTo(
-            if (portalScanResults != null) {
+                e.block,
+                PortalFrame.State.INACTIVE
+            )
+            if (newPortal != null) {
                 logger.info("found portal frame, creating portal")
-                portalScanResults.color()
+                val replacedPortal = portals.activateAndReplacePortal(newPortal)
-                e.block.world.playSound(portalScanResults.portalCenter, Sound.BLOCK_BEACON_ACTIVATE, 20f, 1f)
+                newPortal.activate()
-                e.block.world.spawnParticle(Particle.SPELL, portalScanResults.portalCenter, 40)
+                replacedPortal?.deactivate()
             } else {
                 logger.info("no portal frame found matching placed block, ignoring")
             }
@@ -87,7 +92,10 @@ class MinecraftPortalPlugin() : JavaPlugin(), Listener
         if(block.type !in DOOR_TYPES) {
             return
         }
-        val portalScanResults = findPortalFrameConnectedTo(block, PortalFrame.State.ACTIVE) ?: return
+        val portalScanResults = findPortalFrameConnectedTo(
+            block,
+            PortalFrame.State.ACTIVE
+        ) ?: return
         val door = block.blockData as Door
         if (!portalScanResults.isStandingInPortal(e.player.location)) {
             e.isCancelled = true
@@ -112,14 +120,12 @@ class MinecraftPortalPlugin() : JavaPlugin(), Listener
         if (block.type !in PortalFrame.State.ACTIVE.allValidBlocks) {
             return
         }
-        val portalScanResults = findPortalFrameConnectedTo(block, PortalFrame.State.ACTIVE)
+        val oldPortal = findPortalFrameConnectedTo(
-        if (portalScanResults != null) {
+            block,
-            logger.info("found portal frame matching destroyed block, deactivating")
+            PortalFrame.State.ACTIVE
-            portalScanResults.uncolor()
+        )
-            block.world.playSound(portalScanResults.portalCenter, Sound.BLOCK_BEACON_DEACTIVATE, 20f, 1f)
+        if (oldPortal != null && portals.deactivatePortal(oldPortal)) {
-            block.world.spawnParticle(Particle.SMOKE_NORMAL, portalScanResults.portalCenter, 40)
+            oldPortal.deactivate()
-        } else {
-            logger.info("no portal frame found matching destroyed block, ignoring")
         }
     }
 }

src/main/kotlin/net/deliciousreya/minecraftportal/extensions/Location.kt

@@ -1,7 +1,15 @@
 package net.deliciousreya.minecraftportal.extensions
 
+import net.deliciousreya.minecraftportal.model.DeserializationException
+import net.deliciousreya.minecraftportal.model.SerializationException
+import net.deliciousreya.minecraftportal.proto.PortalSaveDataProtos
 import org.bukkit.Location
+import org.bukkit.Server
+import org.bukkit.util.BlockVector
 import org.bukkit.util.Vector
+import java.lang.IllegalArgumentException
+import java.lang.IllegalStateException
+import java.util.*
 
 operator fun Location.plus(v: Vector):Location {
     return this.clone().add(v)
@@ -29,4 +37,15 @@ fun Location.minus(x: Double, y: Double, z: Double):Location {
 
 operator fun Location.times(n:Double):Location {
     return this.clone().multiply(n)
+}
+
+fun PortalSaveDataProtos.Location.toLocation(server: Server): Location {
+    val uuid = UUID.fromString(this.worldUuid)
+    val world = (server.getWorld(uuid) ?: throw DeserializationException("Couldn't find world with UUID $worldUuid"))
+    return BlockVector(this.x, this.y, this.z).toLocation(world)
+}
+
+fun Location.toProto(): PortalSaveDataProtos.Location {
+    val world = this.world ?: throw SerializationException("Can't serialize location without world")
+    return PortalSaveDataProtos.Location.newBuilder().setWorldUuid(world.uid.toString()).setX(this.blockX).setY(this.blockY).setZ(this.blockZ).build()
 }

src/main/kotlin/net/deliciousreya/minecraftportal/extensions/Material.kt

@@ -0,0 +1,26 @@
+package net.deliciousreya.minecraftportal.extensions
+
+import com.google.common.collect.ImmutableBiMap
+import net.deliciousreya.minecraftportal.model.DeserializationException
+import net.deliciousreya.minecraftportal.proto.PortalSaveDataProtos
+import org.bukkit.Material
+import java.lang.IllegalStateException
+
+val MINERAL_MAPPING: ImmutableBiMap<Material, PortalSaveDataProtos.Portal.Mineral> = ImmutableBiMap.builder<Material, PortalSaveDataProtos.Portal.Mineral>()
+    .put(Material.COAL_BLOCK, PortalSaveDataProtos.Portal.Mineral.COAL)
+    .put(Material.REDSTONE_BLOCK, PortalSaveDataProtos.Portal.Mineral.REDSTONE)
+    .put(Material.LAPIS_BLOCK, PortalSaveDataProtos.Portal.Mineral.LAPIS)
+    .put(Material.GOLD_BLOCK, PortalSaveDataProtos.Portal.Mineral.GOLD)
+    .put(Material.DIAMOND_BLOCK, PortalSaveDataProtos.Portal.Mineral.DIAMOND)
+    .put(Material.EMERALD_BLOCK, PortalSaveDataProtos.Portal.Mineral.EMERALD)
+    .put(Material.IRON_BLOCK, PortalSaveDataProtos.Portal.Mineral.IRON)
+    .put(Material.QUARTZ_BLOCK, PortalSaveDataProtos.Portal.Mineral.QUARTZ)
+    .build()
+
+fun Material.toMineralProto(): PortalSaveDataProtos.Portal.Mineral {
+    return MINERAL_MAPPING[this] ?: throw DeserializationException("Not a mineral: ${this}")
+}
+
+fun PortalSaveDataProtos.Portal.Mineral.toMaterial(): Material {
+    return MINERAL_MAPPING.inverse()[this] ?: throw DeserializationException("Not a material: ${this}")
+}

src/main/kotlin/net/deliciousreya/minecraftportal/model/DeserializationException.kt

@@ -0,0 +1,5 @@
+package net.deliciousreya.minecraftportal.model
+
+import java.lang.Exception
+
+class DeserializationException (message: String? = null, cause: Throwable? = null) : Exception(message, cause)

src/main/kotlin/net/deliciousreya/minecraftportal/model/Portal.kt

@@ -0,0 +1,27 @@
+package net.deliciousreya.minecraftportal.model
+
+import net.deliciousreya.minecraftportal.extensions.toLocation
+import net.deliciousreya.minecraftportal.extensions.toMaterial
+import net.deliciousreya.minecraftportal.extensions.toMineralProto
+import net.deliciousreya.minecraftportal.extensions.toProto
+import net.deliciousreya.minecraftportal.proto.PortalSaveDataProtos
+import org.bukkit.Material
+import org.bukkit.Server
+import java.lang.IllegalArgumentException
+
+fun PortalSaveDataProtos.Portal.toPortal(server: Server, portalTypes: Map<Material, PortalType>): Portal {
+    val portalType = portalTypes[mineral.toMaterial()] ?: throw IllegalArgumentException("No portal type for $mineral")
+    val result = Portal(PortalFrame(lowerLeftFrontCorner.toLocation(server), entranceDirection.toDirection()), portalType)
+    // TODO: assert that the saved portal and mineral match the actual state of the world
+    return result
+}
+
+class Portal(val frame: PortalFrame, val type: PortalType) {
+    fun toProto(): PortalSaveDataProtos.Portal {
+        return PortalSaveDataProtos.Portal.newBuilder()
+            .setLowerLeftFrontCorner(frame.lowerLeftFrontCorner.toProto())
+            .setEntranceDirection(frame.direction.toProto())
+            .setMineral(frame.mineral.toMineralProto())
+            .build()
+    }
+}

src/main/kotlin/net/deliciousreya/minecraftportal/model/PortalDataStore.kt

@@ -0,0 +1,82 @@
+package net.deliciousreya.minecraftportal.model
+
+import com.google.common.collect.ImmutableMap
+import net.deliciousreya.minecraftportal.extensions.MINERAL_MAPPING
+import net.deliciousreya.minecraftportal.proto.PortalSaveDataProtos
+import org.bukkit.Material
+import org.bukkit.Server
+import java.io.File
+import java.lang.IllegalArgumentException
+
+class PortalDataStore() {
+    val portalTypes: ImmutableMap<Material, PortalType>
+    init {
+        val portalTypesBuilder = ImmutableMap.builder<Material, PortalType>()
+        for (mineralType in MINERAL_MAPPING.keys) {
+            portalTypesBuilder.put(mineralType, PortalType(mineralType))
+        }
+        portalTypes = portalTypesBuilder.build()
+    }
+
+    fun onAfterChanged() {
+        // Does nothing for now.
+        // TODO: Save the data.
+    }
+
+    /** Marks the new portal as active, and removes the one that needs to be deactivated, if any. */
+    fun activateAndReplacePortal(frame: PortalFrame): PortalFrame? {
+        val type = portalTypes[frame.mineral] ?: throw IllegalArgumentException("Can't create a portal of type ${frame.mineral}")
+        val result = type.addOrReplacePortal(Portal(frame, type))?.frame
+        onAfterChanged()
+        return result
+    }
+
+    /** Deactivates the given portal. */
+    fun deactivatePortal(frame: PortalFrame): Boolean {
+        val type = portalTypes[frame.mineral] ?: throw IllegalArgumentException("There are no portals of type ${frame.mineral}")
+        val result = type.removePortalWithFrame(frame)
+        onAfterChanged()
+        return result
+    }
+
+    /** Forgets all the data without actually affecting the world. */
+    fun clear() {
+        for (portalType in this.portalTypes.values) {
+            portalType.clear()
+        }
+    }
+
+    fun loadFromProto(server: Server, proto: PortalSaveDataProtos.PortalSaveData) {
+        clear()
+        for (portalProto in proto.unpairedPortalsList) {
+            val portal = portalProto.toPortal(server, portalTypes)
+            portal.type.loadUnpairedPortal(portal)
+        }
+        for (portalPair in proto.pairedPortalsList) {
+            val olderPortal = portalPair.older.toPortal(server, portalTypes)
+            val newerPortal = portalPair.newer.toPortal(server, portalTypes)
+            if (olderPortal.type != newerPortal.type) {
+                throw DeserializationException("Pair had non-matching types: ${olderPortal.type} and ${newerPortal.type}")
+            }
+            olderPortal.type.loadPairedPortals(olderPortal, newerPortal)
+        }
+    }
+
+    fun toProto(): PortalSaveDataProtos.PortalSaveData {
+        val builder = PortalSaveDataProtos.PortalSaveData.newBuilder()
+        for (portalType in this.portalTypes.values) {
+            when {
+                portalType.isEmpty -> {
+                    // Nothing here to save. Just skip it.
+                }
+                portalType.isPaired -> {
+                    builder.addPairedPortals(portalType.toProto())
+                }
+                else -> {
+                    builder.addUnpairedPortals(portalType.getOnlyPortal.toProto())
+                }
+            }
+        }
+        return builder.build()
+    }
+}

src/main/kotlin/net/deliciousreya/minecraftportal/model/PortalFrame.kt

@@ -1,4 +1,4 @@
-package net.deliciousreya.minecraftportal
+package net.deliciousreya.minecraftportal.model
 
 import com.google.common.collect.ImmutableList
 import com.google.common.collect.ImmutableMap
@@ -7,8 +7,11 @@ import org.bukkit.Location
 import org.bukkit.block.Block
 import org.bukkit.util.Vector
 import net.deliciousreya.minecraftportal.extensions.*
+import net.deliciousreya.minecraftportal.proto.PortalSaveDataProtos
 import org.bukkit.Material
 import org.bukkit.Material.*
+import org.bukkit.Particle
+import org.bukkit.Sound
 import org.bukkit.block.BlockFace
 import org.bukkit.material.Directional
 
@@ -25,11 +28,15 @@ val MINERAL_TYPES: ImmutableMap<Material, Material> = ImmutableMap.Builder<Mater
 
 val DOOR_TYPES: ImmutableSet<Material> = ImmutableSet.of(ACACIA_DOOR, BIRCH_DOOR, DARK_OAK_DOOR, IRON_DOOR, JUNGLE_DOOR, OAK_DOOR, SPRUCE_DOOR)
 
-fun findPortalFrameConnectedTo(block:Block, state:PortalFrame.State): PortalFrame? {
+fun findPortalFrameConnectedTo(block:Block, state: PortalFrame.State): PortalFrame? {
     when {
         block.type in state.glassBlocks -> for (direction in PortalFrame.EntranceDirection.values()) {
             for (vector in direction.glassOffsets) {
-                val scanResult = checkPortalFrameAt(block.location.subtract(vector), direction, state)
+                val scanResult = checkPortalFrameAt(
+                    block.location.subtract(vector),
+                    direction,
+                    state
+                )
                 if (scanResult != null) {
                     return scanResult
                 }
@@ -37,14 +44,22 @@ fun findPortalFrameConnectedTo(block:Block, state:PortalFrame.State): PortalFram
         }
         block.type in state.doorBlocks -> for (direction in PortalFrame.EntranceDirection.values()) {
             for (vector in direction.doorOffsets) {
-                val scanResult = checkPortalFrameAt(block.location.subtract(vector), direction, state)
+                val scanResult = checkPortalFrameAt(
+                    block.location.subtract(vector),
+                    direction,
+                    state
+                )
                 if (scanResult != null) {
                     return scanResult
                 }
             }
         }
         block.type in state.mineralBlocks -> for (direction in PortalFrame.EntranceDirection.values()) {
-            val scanResult = checkPortalFrameAt(block.location.subtract(direction.mineralOffset), direction, state)
+            val scanResult = checkPortalFrameAt(
+                block.location.subtract(direction.mineralOffset),
+                direction,
+                state
+            )
             if (scanResult != null) {
                 return scanResult
             }
@@ -54,7 +69,7 @@ fun findPortalFrameConnectedTo(block:Block, state:PortalFrame.State): PortalFram
 }
 
 /** Detects whether there is a portal frame in the given state at the given location, extending in the given direction. */
-fun checkPortalFrameAt(location:Location, direction:PortalFrame.EntranceDirection, state:PortalFrame.State): PortalFrame? {
+fun checkPortalFrameAt(location:Location, direction: PortalFrame.EntranceDirection, state: PortalFrame.State): PortalFrame? {
     val mineral = (location + direction.mineralOffset).block
     if (mineral.type !in state.mineralBlocks) {
         return null
@@ -74,20 +89,31 @@ fun checkPortalFrameAt(location:Location, direction:PortalFrame.EntranceDirectio
     return PortalFrame(location, direction)
 }
 
+fun PortalSaveDataProtos.Portal.Direction.toDirection(): PortalFrame.EntranceDirection {
+    for (direction in PortalFrame.EntranceDirection.values()) {
+        if (direction.protoEnum == this) {
+            return direction
+        }
+    }
+    throw IllegalStateException("Bad enum value: $this")
+}
+
 /** Information about a portal frame. */
 data class PortalFrame(val lowerLeftFrontCorner: Location, val direction: EntranceDirection) {
     enum class State(val glassBlocks: ImmutableSet<Material>, val doorBlocks: ImmutableSet<Material>, val mineralBlocks: ImmutableSet<Material>) {
-        ACTIVE(ImmutableSet.copyOf(MINERAL_TYPES.values), DOOR_TYPES, ImmutableSet.copyOf(MINERAL_TYPES.keys)),
+        ACTIVE(ImmutableSet.copyOf(MINERAL_TYPES.values),
-        INACTIVE(ImmutableSet.of(GLASS), DOOR_TYPES, ImmutableSet.copyOf(MINERAL_TYPES.keys));
+            DOOR_TYPES, ImmutableSet.copyOf(MINERAL_TYPES.keys)),
+        INACTIVE(ImmutableSet.of(GLASS),
+            DOOR_TYPES, ImmutableSet.copyOf(MINERAL_TYPES.keys));
 
-        val allValidBlocks = ImmutableSet.Builder<Material>().addAll(glassBlocks).addAll(doorBlocks).addAll(mineralBlocks).build()
+        val allValidBlocks:ImmutableSet<Material> = ImmutableSet.Builder<Material>().addAll(glassBlocks).addAll(doorBlocks).addAll(mineralBlocks).build()
     }
     /** The direction along which a portal frame extends. */
-    enum class EntranceDirection(toRight: Vector, toBack: Vector, val doorDirection: BlockFace) {
+    enum class EntranceDirection(toRight: Vector, toBack: Vector, val doorDirection: BlockFace, val protoEnum: PortalSaveDataProtos.Portal.Direction) {
-        NORTH(Vector(1, 0, 0), Vector(0, 0, 1), BlockFace.NORTH),
+        NORTH(Vector(1, 0, 0), Vector(0, 0, 1), BlockFace.NORTH, PortalSaveDataProtos.Portal.Direction.NORTH),
-        SOUTH(Vector(1, 0, 0), Vector(0, 0, -1), BlockFace.SOUTH),
+        SOUTH(Vector(1, 0, 0), Vector(0, 0, -1), BlockFace.SOUTH, PortalSaveDataProtos.Portal.Direction.SOUTH),
-        EAST(Vector(0, 0, 1), Vector(-1, 0, 0), BlockFace.EAST),
+        EAST(Vector(0, 0, 1), Vector(-1, 0, 0), BlockFace.EAST, PortalSaveDataProtos.Portal.Direction.EAST),
-        WEST(Vector(0, 0, 1), Vector(1, 0, 0), BlockFace.WEST);
+        WEST(Vector(0, 0, 1), Vector(1, 0, 0), BlockFace.WEST, PortalSaveDataProtos.Portal.Direction.WEST);
 
         val glassOffsets: ImmutableList<Vector> = ImmutableList.of(
             // check corners first:
@@ -138,6 +164,10 @@ data class PortalFrame(val lowerLeftFrontCorner: Location, val direction: Entran
             Vector(0, 1, 0) + toRight,
             Vector(0, 2, 0) + toRight
         )
+
+        fun toProto():PortalSaveDataProtos.Portal.Direction {
+            return this.protoEnum
+        }
     }
 
     val portalCenter = lowerLeftFrontCorner + direction.doorOffsets[0]
@@ -146,16 +176,22 @@ data class PortalFrame(val lowerLeftFrontCorner: Location, val direction: Entran
         return direction.doorOffsets.any { offset -> location.block.location - offset == lowerLeftFrontCorner }
     }
 
-    fun color() {
+    val mineral = (lowerLeftFrontCorner + direction.mineralOffset).block.type
+
+    fun activate() {
         val mineral = (lowerLeftFrontCorner + direction.mineralOffset).block
         for (offset in direction.glassOffsets) {
             (lowerLeftFrontCorner + offset).block.type = MINERAL_TYPES.getOrDefault(mineral.type, BROWN_STAINED_GLASS)
         }
+        portalCenter.world?.playSound(portalCenter, Sound.BLOCK_BEACON_ACTIVATE, 20f, 1f)
+        portalCenter.world?.spawnParticle(Particle.SPELL, portalCenter, 40)
     }
 
-    fun uncolor() {
+    fun deactivate() {
         for (offset in direction.glassOffsets) {
             (lowerLeftFrontCorner + offset).block.type = GLASS
         }
+        portalCenter.world?.playSound(portalCenter, Sound.BLOCK_BEACON_DEACTIVATE, 20f, 1f)
+        portalCenter.world?.spawnParticle(Particle.SMOKE_NORMAL, portalCenter, 40)
     }
 }

src/main/kotlin/net/deliciousreya/minecraftportal/model/PortalType.kt

@@ -0,0 +1,89 @@
+package net.deliciousreya.minecraftportal.model
+
+import net.deliciousreya.minecraftportal.proto.PortalSaveDataProtos
+import org.bukkit.Material
+import java.lang.IllegalArgumentException
+import java.lang.IllegalStateException
+
+class PortalType(val mineral: Material) {
+    var oldestActivePortal: Portal? = null
+    var newestActivePortal: Portal? = null
+
+    val isEmpty: Boolean get() = oldestActivePortal == null && newestActivePortal == null
+    val isPaired: Boolean get() = oldestActivePortal != null && newestActivePortal != null
+
+    val getOnlyPortal: Portal get() = if (!isEmpty && !isPaired) oldestActivePortal!! else throw IllegalStateException("Can't getOnlyPortal for empty or paired portal type $this")
+
+    fun toProto(): PortalSaveDataProtos.PortalPair {
+        val builder = PortalSaveDataProtos.PortalPair.newBuilder()
+        val oldestPortal = oldestActivePortal
+        val newestPortal = newestActivePortal
+        if (oldestPortal != null) {
+            builder.older = oldestPortal.toProto()
+        }
+        if (newestPortal != null) {
+            builder.newer = newestPortal.toProto()
+        }
+        return builder.build()
+    }
+
+    fun addOrReplacePortal(portal: Portal): Portal? {
+        if (portal.type != this) {
+            throw DeserializationException("Tried to add $portal which didn't belong to ${this}")
+        }
+        return when {
+            this.isEmpty  -> {
+                this.oldestActivePortal = portal
+                null
+            }
+            else -> {
+                val replacedPortal = newestActivePortal
+                this.newestActivePortal = portal
+                replacedPortal
+            }
+        }
+    }
+
+    fun loadUnpairedPortal(portal: Portal) {
+        if (!this.isEmpty) {
+            throw DeserializationException("Already have a value for ${this} when adding $portal")
+        }
+        if (portal.type != this) {
+            throw DeserializationException("Tried to add $portal which didn't belong to ${this}")
+        }
+        this.oldestActivePortal = portal
+    }
+
+    fun loadPairedPortals(olderPortal: Portal, newerPortal: Portal) {
+        if (!this.isEmpty) {
+            throw DeserializationException("Already have a value for ${this} when adding $olderPortal and $newerPortal")
+        }
+        if (olderPortal.type != this) {
+            throw DeserializationException("Tried to add $olderPortal which didn't belong to ${this}")
+        }
+        if (newerPortal.type != this) {
+            throw DeserializationException("Tried to add $newerPortal which didn't belong to ${this}")
+        }
+        this.oldestActivePortal = olderPortal
+        this.newestActivePortal = newerPortal
+    }
+
+    fun clear() {
+        oldestActivePortal = null
+        newestActivePortal = null
+    }
+
+    override fun toString():String {
+        return "PortalType{mineral=$mineral, oldestActivePortal=$oldestActivePortal, newestActivePortal=$newestActivePortal}"
+    }
+
+    fun removePortalWithFrame(frame: PortalFrame):Boolean {
+        if (oldestActivePortal?.frame == frame) {
+            oldestActivePortal = newestActivePortal
+        } else if (newestActivePortal?.frame != frame) {
+            return false
+        }
+        newestActivePortal = null
+        return true
+    }
+}

src/main/kotlin/net/deliciousreya/minecraftportal/model/SerializationException.kt

@@ -0,0 +1,5 @@
+package net.deliciousreya.minecraftportal.model
+
+import java.lang.Exception
+
+class SerializationException (message: String? = null, cause: Throwable? = null) : Exception(message, cause)

src/main/proto/portal-save-data.proto

@@ -0,0 +1,47 @@
+syntax = "proto3";
+
+package net.deliciousreya.minecraftportal;
+
+option java_package = "net.deliciousreya.minecraftportal.proto";
+option java_outer_classname = "PortalSaveDataProtos";
+
+message Location {
+    string world_uuid = 1;
+    int32 x = 2;
+    int32 y = 3;
+    int32 z = 4;
+}
+
+message Portal {
+    enum Direction {
+        UNKNOWN_DIRECTION = 0;
+        NORTH = 1;
+        EAST = 2;
+        WEST = 3;
+        SOUTH = 4;
+    }
+    enum Mineral {
+        UNKNOWN_MINERAL = 0;
+        COAL = 1;
+        REDSTONE = 2;
+        LAPIS = 3;
+        GOLD = 4;
+        DIAMOND = 5;
+        EMERALD = 6;
+        IRON = 7;
+        QUARTZ = 8;
+    }
+    Location lower_left_front_corner = 1;
+    Direction entrance_direction = 2;
+    Mineral mineral = 3;
+}
+
+message PortalPair {
+    Portal older = 1;
+    Portal newer = 2;
+}
+
+message PortalSaveData {
+    repeated PortalPair paired_portals = 1;
+    repeated Portal unpaired_portals = 2;
+}