export class SkillTree {
  constructor() {
    this.nodes = [];
    this.chosen = new Set();
  }

  load(data) {
    this.nodes = data.nodes;
  }

  /** Returns nodes available to pick at next level-up (roots or children of chosen). */
  getAvailable() {
    return this.nodes.filter(n => {
      if (this.chosen.has(n.id)) return false;
      if (n.parent === null) return true;
      return this.chosen.has(n.parent);
    });
  }

  /** Apply a node's effect to the player stats object and mark it chosen. */
  applyNode(nodeId, playerStats) {
    const node = this.nodes.find(n => n.id === nodeId);
    if (!node) return;

    const { stat, add, multiply } = node.effect;
    if (add !== undefined) {
      playerStats[stat] = (playerStats[stat] || 0) + add;
    }
    if (multiply !== undefined) {
      playerStats[stat] = (playerStats[stat] || 1) * multiply;
    }

    this.chosen.add(nodeId);
    return node;
  }

  reset() {
    this.chosen.clear();
  }
}