feat: add Expensive Trades module to increase villager trade costs

Author: Sybsuper

README.md

@@ -30,6 +30,7 @@ The following modules are currently available:
   inventory management more challenging.
 - **Bad Air Caves**: Sometimes, poisonous gas will fill caves, causing damage to players.
 - **Baby Creatures**: Any LivingEntity can spawn as a baby, babies are faster and smaller than their adult counterparts.
+- **Expensive Trades**: Villager trades are more expensive, making it harder to obtain valuable items.
 - **More to come**: This plugin is a work in progress, with more modules planned for future releases.
 
 ## Configuration

src/main/kotlin/com/sybsuper/sybsafetyfirst/modules/ExpensiveTrades.kt

@@ -0,0 +1,60 @@
+package com.sybsuper.sybsafetyfirst.modules
+
+import kotlinx.serialization.Serializable
+import org.bukkit.event.EventHandler
+import org.bukkit.event.entity.VillagerAcquireTradeEvent
+import org.bukkit.event.entity.VillagerReplenishTradeEvent
+
+class ExpensiveTrades : Module {
+    override val description: String = "Trades will become expensive very quickly."
+    override var options: ModuleOptions = ExpensiveTradesOptions()
+    val typeSafeOptions
+        get() = (options as? ExpensiveTradesOptions)
+            ?: error("Options are not of type ExpensiveTradesOptions")
+
+    @Serializable
+    data class ExpensiveTradesOptions(
+        override var enabled: Boolean = true,
+        /**
+         * Multiplier for the price of trades.
+         * Higher values make the price changer more quickly.
+         * Note this price change on itself goes both ways, meaning non-frequent trades (low demand) would be very cheap.
+         * Use the [startingDemand] and [restockMinimumDemand] options to control the demand for trades. Where high demand means high prices.
+         */
+        var priceMultiplierMultiplier: Float = 3f,
+        /**
+         * High demand for trades means higher prices.
+         * This only affects the initial demand for trades.
+         * To keep high prices, the demand has to stay high by trading frequently.
+         * @see restockMinimumDemand
+         */
+        var startingDemand: Int = 5,
+        /**
+         * The minimum demand for trades to be restocked.
+         * If the demand is below this value, the recipe will not be restocked.
+         * This is to prevent trades from becoming too cheap.
+         */
+        var restockMinimumDemand: Int = 5,
+        /**
+         * If true, the recipe will ignore discounts from villagers.
+         * This should be set to true to ensure that trades remain expensive.
+         * This ignores discounts from the hero of the village effect, and curing a zombie villager.
+         */
+        var ignoreDiscounts: Boolean = true,
+
+        ) : ModuleOptions
+
+    @EventHandler(ignoreCancelled = true)
+    fun on(e: VillagerAcquireTradeEvent) {
+        e.recipe.priceMultiplier *= typeSafeOptions.priceMultiplierMultiplier
+        e.recipe.demand += typeSafeOptions.startingDemand
+        if (typeSafeOptions.ignoreDiscounts)
+            e.recipe.setIgnoreDiscounts(true)
+    }
+
+    @EventHandler(ignoreCancelled = true)
+    fun on(e: VillagerReplenishTradeEvent) {
+        if (e.recipe.demand < typeSafeOptions.restockMinimumDemand)
+            e.recipe.demand = typeSafeOptions.restockMinimumDemand
+    }
+}

src/main/kotlin/com/sybsuper/sybsafetyfirst/modules/ModuleManager.kt

@@ -33,7 +33,8 @@ object ModuleManager {
         NetherPortalsDestabilize(),
         SkillBasedInventory(),
         BadAirCaves(),
-        BabyCreatures()
+        BabyCreatures(),
+        ExpensiveTrades()
     )
     private val currentModuleInstances = modules.associateBy { it.id }.toMutableMap()
     private val nameMap = modules.associateBy { it.name }