daggerheart/module/applications/sheets/companion.mjs

import DhCompanionlevelUp from '../levelup/companionLevelup.mjs';
import DaggerheartSheet from './daggerheart-sheet.mjs';

const { ActorSheetV2 } = foundry.applications.sheets;
export default class DhCompanionSheet extends DaggerheartSheet(ActorSheetV2) {
    static DEFAULT_OPTIONS = {
        tag: 'form',
        classes: ['daggerheart', 'sheet', 'actor', 'dh-style', 'companion'],
        position: { width: 700, height: 1000 },
        actions: {
            attackRoll: this.attackRoll,
            levelUp: this.levelUp
        },
        form: {
            handler: this.updateForm,
            submitOnChange: true,
            closeOnSubmit: false
        }
    };

    static PARTS = {
        sidebar: { template: 'systems/daggerheart/templates/sheets/actors/companion/tempMain.hbs' }
    };

    _attachPartListeners(partId, htmlElement, options) {
        super._attachPartListeners(partId, htmlElement, options);

        htmlElement.querySelector('.partner-value')?.addEventListener('change', this.onPartnerChange.bind(this));
    }

    async _prepareContext(_options) {
        const context = await super._prepareContext(_options);
        context.document = this.document;
        context.playerCharacters = game.users
            .filter(x => !x.isGM && x.character)
            .map(x => ({ key: x.character.uuid, name: x.character.name }));

        return context;
    }

    static async updateForm(event, _, formData) {
        await this.document.update(formData.object);
        this.render();
    }

    async onPartnerChange(event) {
        if (event.target.value) {
            const partner = game.actors.find(a => a.uuid === event.target.value);
            await partner.update({ 'system.companion': this.document.uuid });
        } else {
            await this.document.system.partner.update({ 'system.companion': null });
        }

        await this.document.update({ 'system.partner': event.target.value });
    }

    static async attackRoll(event) {
        this.actor.system.attack.use(event);
    }

    static async levelUp() {
        new DhCompanionlevelUp(this.document).render(true);
    }
}