Add applyEffect

terms/Term.ts

@@ -28,7 +28,7 @@ export interface Term {
 	canPrecedeVariable: boolean;
 }
 
-export interface Action extends Term {
+export interface ActionTerm extends Term {
 	action: ActionFn;
 	category: "action";
 }

terms/actions.ts

@@ -1,5 +1,10 @@
-import Scene from "../Scene.ts";
-import Player from "../Player.ts";
+import type Scene from "../Scene.ts";
+import type Player from "../Player.ts";
+import type { ApplyEffectArgs, ItemAction } from "../types.ts";
+
+const ITEM_MISSING = "You don't have that.";
+const ITEM_UNUSABLE = "I don't know how to use that.";
+const ITEM_ALREADY_USED = "I already did that.";
 
 export function look(player: Player, scene: Scene): string {
 	return scene.look(player.activeEffects, scene.activeEffects);
@@ -23,6 +28,66 @@ export function pickUpItem(
 	return "Taken.";
 }
 
-export function checkInventory(player: Player) {
+export function checkInventory(player: Player): string {
 	return player.look();
 }
+
+export function use(player: Player, scene: Scene, target?: string): string {
+	if (!target) {
+		return "What do you want to use?";
+	}
+
+	const { inventory } = player;
+
+	if (inventory === null) {
+		return ITEM_MISSING;
+	}
+
+	const item = inventory.find((i) => i.name === target);
+
+	if (item === undefined) {
+		return ITEM_MISSING;
+	}
+
+	const itemAction = item?.actions["use"];
+
+	if (itemAction === undefined) {
+		return ITEM_UNUSABLE;
+	}
+
+	return executeItemAction(player, scene, itemAction);
+}
+
+function executeItemAction(
+	player: Player,
+	scene: Scene,
+	{ args, type }: ItemAction
+): string {
+	switch (type) {
+		case "applyEffect":
+			return applyEffect(player, scene, args as ApplyEffectArgs);
+		default:
+			return ITEM_UNUSABLE;
+	}
+}
+
+function applyEffect(
+	player: Player,
+	scene: Scene,
+	{ applyTo, effect, reverseResult, reversible, result }: ApplyEffectArgs
+): string {
+	const target = applyTo === "player" ? player : scene;
+	const isApplied = target.hasActiveEffect(effect);
+
+	if (!reversible && isApplied) {
+		return ITEM_ALREADY_USED;
+	}
+
+	if (isApplied) {
+		target.removeEffect(effect);
+		return reverseResult || result;
+	} else {
+		target.addEffect(effect);
+		return result;
+	}
+}

terms/terms.ts

@@ -1,7 +1,7 @@
 import * as actions from "./actions.ts";
-import { Action } from "./Term.ts";
+import { ActionTerm } from "./Term.ts";
 
-const inventory: Action = {
+const inventory: ActionTerm = {
 	action: actions.checkInventory,
 	canPrecedeVariable: false,
 	category: "action",
@@ -10,7 +10,7 @@ const inventory: Action = {
 	precedesConstants: [],
 };
 
-const look: Action = {
+const look: ActionTerm = {
 	action: actions.look,
 	canPrecedeVariable: false,
 	category: "action",
@@ -19,7 +19,7 @@ const look: Action = {
 	precedesConstants: [],
 };
 
-const take: Action = {
+const take: ActionTerm = {
 	action: actions.pickUpItem,
 	canPrecedeVariable: true,
 	category: "action",
@@ -28,8 +28,18 @@ const take: Action = {
 	precedesConstants: [],
 };
 
+const use: ActionTerm = {
+	action: actions.use,
+	canPrecedeVariable: true,
+	category: "action",
+	constant: "use",
+	precedesCategories: [],
+	precedesConstants: [],
+};
+
 export const terms = {
 	[inventory.constant]: inventory,
 	[look.constant]: look,
 	[take.constant]: take,
+	[use.constant]: use,
 };