daggerheart/module/data/armor.mjs

export default class DhpArmor extends foundry.abstract.TypeDataModel {
    static defineSchema() {
      const fields = foundry.data.fields;
      return {
        baseScore: new fields.NumberField({ initial: 1, integer: true }),
        feature: new fields.StringField({ choices: SYSTEM.ITEM.armorFeatures, integer: false }),
        marks: new fields.SchemaField({
          max: new fields.NumberField({ initial: 6, integer: true }),
          value: new fields.NumberField({ initial: 0, integer: true }),
        }),
        description: new fields.HTMLField({}),
      }
    }

    get featureInfo() {
      return this.feature ? CONFIG.daggerheart.ITEM.armorFeatures[this.feature] : null;
    }

    prepareDerivedData(){
      if(this.parent.parent){
        this.applyLevels();
      }
    }

    // Currently bugged as it double triggers. Should get fixed in an updated foundry version.
    applyLevels(){  
      // let armorBonus = 0;
      // for(var level in this.parent.parent.system.levelData.levelups){
      //   var levelData = this.parent.parent.system.levelData.levelups[level];
      //   for(var tier in levelData){
      //     var tierData = levelData[tier];
      //     if(tierData){
      //       armorBonus += Object.keys(tierData.armorOrEvasionSlot).filter(x => tierData.armorOrEvasionSlot[x] === 'armor').length;
      //     }
      //   }
      // }

      // this.marks.max += armorBonus;
    }
}