feat: add functionality to apply Active Affects to owned Items

In the Active Effect Config, there are now additional inputs to configure the effect
to be applied to items owned by the actor instead of the actor itself. It is possible
to select the items to which to apply the effect via matching by name, or via a condition
expression, that provides similar capabilities as the evaluation of mathematical
expressions in rolls. Data from the Actor, Item, and Active Effect can be accessed
similar to how properties are accessed in roll formulas (using the prefixes `@actor`,
`@item`, and `@effect`). For example, in order to apply an effect to all ranged
weapons, the conditions would be
```js
'@item.type' === 'weapon' && '@item.data.attackType' === 'ranged'
```

src/active-effect/active-effect-config.ts

@@ -0,0 +1,31 @@
+// SPDX-FileCopyrightText: 2022 Johannes Loher
+//
+// SPDX-License-Identifier: MIT
+
+export class DS4ActiveEffectConfig extends ActiveEffectConfig {
+    static override get defaultOptions(): DocumentSheetOptions {
+        return foundry.utils.mergeObject(super.defaultOptions, {
+            template: "systems/ds4/templates/sheets/active-effect/active-effect-config.hbs",
+        });
+    }
+
+    override activateListeners(html: JQuery<HTMLElement>): void {
+        super.activateListeners(html);
+        const checkbox = html[0]?.querySelector<HTMLInputElement>(
+            'input[name="flags.ds4.itemEffectConfig.applyToItems"]',
+        );
+        checkbox?.addEventListener("change", () => this.toggleItemEffectConfig(checkbox.checked));
+    }
+
+    private toggleItemEffectConfig(active: boolean) {
+        const elements = this.element[0]?.querySelectorAll(".ds4-item-effect-config");
+        elements?.forEach((element) => {
+            if (active) {
+                element.classList.remove("ds4-hidden");
+            } else {
+                element.classList.add("ds4-hidden");
+            }
+        });
+        this.setPosition({ height: "auto" });
+    }
+}

src/active-effect/active-effect.ts

@@ -2,16 +2,26 @@
 //
 // SPDX-License-Identifier: MIT
 
-import { DS4Actor } from "./actor/actor";
-import { mathEvaluator } from "./expression-evaluation/evaluator";
-import { getGame } from "./helpers";
-
-import type { DS4Item } from "./item/item";
+import { DS4Actor } from "../actor/actor";
+import { mathEvaluator } from "../expression-evaluation/evaluator";
+import { getGame } from "../helpers";
 
+import type { DS4Item } from "../item/item";
 declare global {
     interface DocumentClassConfig {
         ActiveEffect: typeof DS4ActiveEffect;
     }
+    interface FlagConfig {
+        ActiveEffect: {
+            ds4?: {
+                itemEffectConfig?: {
+                    applyToItems?: boolean;
+                    itemName?: string;
+                    condition?: string;
+                };
+            };
+        };
+    }
 }
 
 type PromisedType<T> = T extends Promise<infer U> ? U : T;
@@ -60,15 +70,17 @@ export class DS4ActiveEffect extends ActiveEffect {
         return this.originatingItem?.activeEffectFactor ?? 1;
     }
 
-    override apply(actor: DS4Actor, change: foundry.data.ActiveEffectData["changes"][number]): unknown {
-        change.value = Roll.replaceFormulaData(change.value, actor.data);
+    override apply(document: DS4Actor | DS4Item, change: EffectChangeData): unknown {
+        change.value = Roll.replaceFormulaData(change.value, document.data);
         try {
             change.value = DS4ActiveEffect.safeEval(change.value).toString();
         } catch (e) {
             logger.warn(e);
             // this is a valid case, e.g., if the effect change simply is a string
         }
-        return super.apply(actor, change);
+        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+        // @ts-expect-error In the types and foundry's documentation, only actors are allowed, but the implementation actually works for all kinds of documents
+        return super.apply(document, change);
     }
 
     /**
@@ -114,4 +126,25 @@ export class DS4ActiveEffect extends ActiveEffect {
         }
         return result as number | `${number | boolean}`;
     }
+
+    /**
+     * Get the array of changes for this effect, considering the {@link DS4ActiveEffect#factor}.
+     * @param predicate An optional predicate to filter which changes should be considered
+     * @returns The array of changes from this effect, considering the factor.
+     */
+    getFactoredChangesWithEffect(
+        predicate: (change: EffectChangeData) => boolean = () => true,
+    ): EffectChangeDataWithEffect[] {
+        if (this.data.disabled || this.isSurpressed) {
+            return [];
+        }
+
+        return this.data.changes.filter(predicate).flatMap((change) => {
+            change.priority = change.priority ?? change.mode * 10;
+            return Array<EffectChangeDataWithEffect>(this.factor).fill({ effect: this, change });
+        });
+    }
 }
+
+export type EffectChangeData = foundry.data.ActiveEffectData["changes"][number];
+export type EffectChangeDataWithEffect = { effect: DS4ActiveEffect; change: EffectChangeData };

src/actor/actor-sheet.ts

@@ -5,7 +5,8 @@
 //
 // SPDX-License-Identifier: MIT
 
-import { DS4ActiveEffect } from "../active-effect";
+import { DS4ActiveEffect } from "../active-effect/active-effect";
+import { disableOverriddenFields } from "../apps/sheet-helpers";
 import { DS4 } from "../config";
 import { getCanvas, getGame } from "../helpers";
 import { getDS4Settings } from "../settings";
@@ -108,6 +109,8 @@ export class DS4ActorSheet extends ActorSheet<ActorSheet.Options, DS4ActorSheetD
         html.find(".rollable-check").on("click", this.onRollCheck.bind(this));
 
         html.find(".sort-items").on("click", this.onSortItems.bind(this));
+
+        disableOverriddenFields.call(this);
     }
 
     /**

src/actor/actor.ts

@@ -4,7 +4,9 @@
 // SPDX-License-Identifier: MIT
 
 import { DS4 } from "../config";
+import { mathEvaluator } from "../expression-evaluation/evaluator";
 import { getGame } from "../helpers";
+import logger from "../logger";
 import { createCheckRoll } from "../rolls/check-factory";
 import { isAttribute, isTrait } from "./actor-data-source-base";
 
@@ -14,7 +16,7 @@ import type { DS4Item } from "../item/item";
 import type { ItemType } from "../item/item-data-source";
 import type { DS4ShieldDataProperties } from "../item/shield/shield-data-properties";
 import type { Check } from "./actor-data-properties-base";
-
+import type { EffectChangeData } from "../active-effect/active-effect";
 declare global {
     interface DocumentClassConfig {
         Actor: typeof DS4Actor;
@@ -25,7 +27,10 @@ declare global {
  * The Actor class for DS4
  */
 export class DS4Actor extends Actor {
+    initialized: boolean | undefined;
+
     override prepareData(): void {
+        this.initialized = true;
         this.data.reset();
         this.prepareBaseData();
         this.prepareEmbeddedDocuments();
@@ -54,6 +59,41 @@ export class DS4Actor extends Actor {
         );
     }
 
+    private get actorEffects() {
+        return this.effects.filter((effect) => !effect.data.flags.ds4?.itemEffectConfig?.applyToItems);
+    }
+
+    /**
+     * Get the effects of this actor that should be applied to the given item.
+     * @param item The item for which to get effects
+     * @returns The array of effects that are candidates to be applied to the item
+     */
+    itemEffects(item: DS4Item) {
+        return this.effects.filter((effect) => {
+            const { applyToItems, itemName, condition } = effect.data.flags.ds4?.itemEffectConfig ?? {};
+
+            if (!applyToItems || (itemName !== undefined && itemName !== "" && itemName !== item.name)) {
+                return false;
+            }
+
+            if (condition !== undefined && condition !== "") {
+                try {
+                    const replacedCondition = Roll.replaceFormulaData(condition, {
+                        item: item.data,
+                        actor: this.data,
+                        effect: effect.data,
+                    });
+                    return Boolean(mathEvaluator.evaluate(replacedCondition));
+                } catch (error) {
+                    logger.warn(error);
+                    return false;
+                }
+            }
+
+            return true;
+        });
+    }
+
     /**
      * We override this with an empty implementation because we have our own custom way of applying
      * {@link ActiveEffect}s and {@link Actor#prepareEmbeddedDocuments} calls this.
@@ -81,31 +121,17 @@ export class DS4Actor extends Actor {
      *
      * @param predicate - The predicate that ActiveEffectChanges need to satisfy in order to be applied
      */
-    applyActiveEffectsFiltered(predicate: (change: foundry.data.ActiveEffectData["changes"][number]) => boolean): void {
+    applyActiveEffectsFiltered(predicate: (change: EffectChangeData) => boolean): void {
         const overrides: Record<string, unknown> = {};
 
         // Organize non-disabled and -surpressed effects by their application priority
-        const changes: (foundry.data.ActiveEffectData["changes"][number] & { effect: ActiveEffect })[] =
-            this.effects.reduce(
-                (changes: (foundry.data.ActiveEffectData["changes"][number] & { effect: ActiveEffect })[], e) => {
-                    if (e.data.disabled || e.isSurpressed) return changes;
-
-                    const newChanges = e.data.changes.filter(predicate).flatMap((c) => {
-                        const changeSource = c.toObject();
-                        changeSource.priority = changeSource.priority ?? changeSource.mode * 10;
-                        return Array(e.factor).fill({ ...changeSource, effect: e });
-                    });
-
-                    return changes.concat(newChanges);
-                },
-                [],
-            );
-        changes.sort((a, b) => (a.priority ?? 0) - (b.priority ?? 0));
+        const changesWithEffect = this.actorEffects.flatMap((e) => e.getFactoredChangesWithEffect(predicate));
+        changesWithEffect.sort((a, b) => (a.change.priority ?? 0) - (b.change.priority ?? 0));
 
         // Apply all changes
-        for (const change of changes) {
-            const result = change.effect.apply(this, change);
-            if (result !== null) overrides[change.key] = result;
+        for (const changeWithEffect of changesWithEffect) {
+            const result = changeWithEffect.effect.apply(this, changeWithEffect.change);
+            if (result !== null) overrides[changeWithEffect.change.key] = result;
         }
 
         // Expand the set of final overrides

src/apps/sheet-helpers.ts

@@ -0,0 +1,25 @@
+// SPDX-FileCopyrightText: 2022 Johannes Loher
+//
+// SPDX-License-Identifier: MIT
+
+import { getGame } from "../helpers";
+
+export function disableOverriddenFields<
+    Options extends FormApplicationOptions,
+    Data extends object,
+    ConcreteObject extends { overrides: Record<string, unknown> },
+>(this: FormApplication<Options, Data, ConcreteObject>): void {
+    const inputs = ["INPUT", "SELECT", "TEXTAREA", "BUTTON"];
+    const titleAddition = `(${getGame().i18n.localize("DS4.TooltipDisabledDueToEffects")})`;
+    for (const key of Object.keys(foundry.utils.flattenObject(this.object.overrides))) {
+        const elements = this.form?.querySelectorAll(`[name="${key}"]`);
+        elements?.forEach((element) => {
+            if (inputs.includes(element.tagName)) {
+                element.setAttribute("disabled", "");
+                const title = element.getAttribute("title");
+                const newTitle = title === null ? titleAddition : `${title} ${titleAddition}`;
+                element.setAttribute("title", newTitle);
+            }
+        });
+    }
+}

src/hooks/init.ts

@@ -4,7 +4,8 @@
 //
 // SPDX-License-Identifier: MIT
 
-import { DS4ActiveEffect } from "../active-effect";
+import { DS4ActiveEffect } from "../active-effect/active-effect";
+import { DS4ActiveEffectConfig } from "../active-effect/active-effect-config";
 import { DS4CharacterActorSheet } from "../actor/character/character-sheet";
 import { DS4CreatureActorSheet } from "../actor/creature/creature-sheet";
 import { DS4ActorProxy } from "../actor/proxy";
@@ -65,11 +66,16 @@ async function init() {
 
     registerSystemSettings();
 
-    Actors.unregisterSheet("core", ActorSheet);
-    Actors.registerSheet("ds4", DS4CharacterActorSheet, { types: ["character"], makeDefault: true });
-    Actors.registerSheet("ds4", DS4CreatureActorSheet, { types: ["creature"], makeDefault: true });
-    Items.unregisterSheet("core", ItemSheet);
-    Items.registerSheet("ds4", DS4ItemSheet, { makeDefault: true });
+    DocumentSheetConfig.unregisterSheet(Actor, "core", ActorSheet);
+    DocumentSheetConfig.registerSheet(Actor, "ds4", DS4CharacterActorSheet, {
+        types: ["character"],
+        makeDefault: true,
+    });
+    DocumentSheetConfig.registerSheet(Actor, "ds4", DS4CreatureActorSheet, { types: ["creature"], makeDefault: true });
+    DocumentSheetConfig.unregisterSheet(Item, "core", ItemSheet);
+    DocumentSheetConfig.registerSheet(Item, "ds4", DS4ItemSheet, { makeDefault: true });
+    DocumentSheetConfig.unregisterSheet(ActiveEffect, "core", ActiveEffectConfig);
+    DocumentSheetConfig.registerSheet(ActiveEffect, "ds4", DS4ActiveEffectConfig, { makeDefault: true });
 
     preloadFonts();
     await registerHandlebarsPartials();

src/item/item-sheet.ts

@@ -4,7 +4,8 @@
 //
 // SPDX-License-Identifier: MIT
 
-import { DS4ActiveEffect } from "../active-effect";
+import { DS4ActiveEffect } from "../active-effect/active-effect";
+import { disableOverriddenFields } from "../apps/sheet-helpers";
 import { DS4 } from "../config";
 import { getGame } from "../helpers";
 import notifications from "../ui/notifications";
@@ -41,6 +42,16 @@ export class DS4ItemSheet extends ItemSheet<ItemSheet.Options, DS4ItemSheetData>
         return data;
     }
 
+    override _getSubmitData(updateData = {}) {
+        const data = super._getSubmitData(updateData);
+        // Prevent submitting overridden values
+        const overrides = foundry.utils.flattenObject(this.item.overrides);
+        for (const k of Object.keys(overrides)) {
+            delete data[k];
+        }
+        return data;
+    }
+
     override setPosition(
         options: Partial<Application.Position> = {},
     ): (Application.Position & { height: number }) | void {
@@ -60,6 +71,8 @@ export class DS4ItemSheet extends ItemSheet<ItemSheet.Options, DS4ItemSheetData>
         if (!this.options.editable) return;
 
         html.find(".control-effect").on("click", this.onControlEffect.bind(this));
+
+        disableOverriddenFields.call(this);
     }
 
     /**
@@ -86,8 +99,6 @@ export class DS4ItemSheet extends ItemSheet<ItemSheet.Options, DS4ItemSheetData>
 
     /**
      * Creates a new embedded effect.
-     *
-     * @param event - The originating click event
      */
     protected onCreateEffect(): void {
         DS4ActiveEffect.createDefault(this.item);

src/item/item.ts

@@ -24,6 +24,39 @@ declare global {
  * The Item class for DS4
  */
 export class DS4Item extends Item {
+    /** An object that tracks the changes to the data model which were applied by active effects */
+    overrides: Record<string, unknown> = {};
+
+    override prepareData() {
+        this.data.reset();
+        this.prepareBaseData();
+        this.prepareEmbeddedDocuments();
+        this.prepareDerivedData();
+        this.applyActiveEffects();
+    }
+
+    applyActiveEffects(): void {
+        if (!this.actor?.initialized) {
+            return;
+        }
+
+        this.overrides = {};
+        const overrides: Record<string, unknown> = {};
+
+        // Organize non-disabled and -surpressed effects by their application priority
+        const changesWithEffect = this.actor?.itemEffects(this).flatMap((e) => e.getFactoredChangesWithEffect()) ?? [];
+        changesWithEffect.sort((a, b) => (a.change.priority ?? 0) - (b.change.priority ?? 0));
+
+        // Apply all changes
+        for (const changeWithEffect of changesWithEffect) {
+            const result = changeWithEffect.effect.apply(this, changeWithEffect.change);
+            if (result !== null) overrides[changeWithEffect.change.key] = result;
+        }
+
+        // Expand the set of final overrides
+        this.overrides = foundry.utils.expandObject({ ...foundry.utils.flattenObject(this.overrides), ...overrides });
+    }
+
     override prepareDerivedData(): void {
         this.data.data.rollable = false;
     }