/**
 * The quest ledger — the run's quest STATE (pure; the data is
 * data/quests.json).
 *
 * A quest's REQUIREMENTS are not tracked here — they are computed LIVE
 * from the run when the scene snapshots the dossier (GameScene.
 * questSnapshot): research progress, lifetime minerals mined from
 * asteroids, the home world's tether standing, the discovery ledger.
 * Only the two things the run owns are state:
 *
 *   granted   — which quest ids the player HOLDS (the starter quest is
 *               granted on the run's first boot; future quests are granted
 *               by whatever event issues them)
 *   claimed   — which of the held quests have PAID OUT their reward
 *   priority  — the ONE priority quest the tracker HUD features (title +
 *               live checklist). The player sets/clears it; the ledger
 *               also auto-assigns it (see resolvePriority) so there is
 *               always a priority while an active story quest exists.
 *   cleared   — the player CLEARED the priority; the auto-assignment is
 *               re-armed by any grant or claim (the active set changed).
 *
 * …and that is exactly what gets saved (SaveData capture/prepare), so a
 * save can never hand out a reward twice or un-grant a quest.
 */
import { config } from '../config/Config.js';

/** @returns {Array<object>} every quest defined (data/quests.json → quests) */
export function questDefs() {
  const list = config.get('quests.quests', []);
  return Array.isArray(list) ? list : [];
}

/** @returns {object|null} the quest definition with this id (or null) */
export function questDef(id) {
  return questDefs().find((q) => q && q.id === id) ?? null;
}

/** @returns {string[]} the ids granted on a FRESH run (quests.json → starter) */
export function starterQuestIds() {
  return questDefs()
    .filter((q) => q && q.starter === true)
    .map((q) => q.id);
}

/**
 * A held-quest ledger. The ids come from data/quests.json (validated
 * against it on load — a save pointing at a removed quest just drops it).
 */
export class QuestState {
  constructor() {
    this.granted = new Set();
    this.claimed = new Set();
    this.priority = null; // the active quest id, or null
    this.priorityCleared = false; // the player declined a priority (sticks until a grant/claim)
  }

  /**
   * Grant a quest (idempotent — re-granting one already held is a no-op).
   * Unknown ids are ignored. @returns {boolean} true when NEWLY granted
   */
  give(id) {
    if (typeof id !== 'string' || id === '') return false;
    if (!questDef(id)) return false;
    if (this.granted.has(id)) return false;
    this.granted.add(id);
    this.priorityCleared = false; // a new quest re-arms the auto-priority
    return true;
  }

  isGranted(id) {
    return this.granted.has(id);
  }

  isClaimed(id) {
    return this.claimed.has(id);
  }

  /**
   * Mark a quest's reward as paid out (idempotent). Only quests that are
   * held + fully satisfied should be claimed — the satisfaction is the
   * scene's call (GameScene.claimQuest checks the live snapshot).
   * @returns {boolean} true when NEWLY claimed
   */
  claim(id) {
    if (!this.granted.has(id)) return false;
    if (this.claimed.has(id)) return false;
    this.claimed.add(id);
    if (this.priority === id) this.priority = null; // it can't feature itself
    this.priorityCleared = false; // the active set changed → re-arm the auto-priority
    return true;
  }

  // ------------------------------------------------------------ priority

  /**
   * Set the priority quest (the tracker HUD's featured quest: title +
   * checklist). Must be HELD and not yet CLAIMED. Idempotent — re-setting
   * the current priority is a no-op.
   * @returns {boolean} true when the priority CHANGED
   */
  setPriority(id) {
    if (typeof id !== 'string' || id === '') return false;
    if (!this.granted.has(id) || this.claimed.has(id)) return false;
    if (this.priority === id) return false;
    this.priority = id;
    this.priorityCleared = false;
    return true;
  }

  /**
   * Clear the priority (the player's "no priority right now"). It STICKS
   * — the auto-assignment stays off until a new quest is granted or one
   * is claimed (either re-arms it, the active set changed).
   * @returns {boolean} true when there WAS a priority to clear
   */
  clearPriority() {
    if (!this.priority) return false;
    this.priority = null;
    this.priorityCleared = true;
    return true;
  }

  /**
   * Resolve the effective priority from the ACTIVE quests (held + not
   * claimed) in DISPLAY order — main story first, then side quests
   * (data/quests.json order within a category):
   *   - the stored priority when it is still active (the player's choice,
   *     or the last auto-assignment);
   *   - otherwise the FIRST active quest — unless the player cleared the
   *     priority (clearPriority), in which case null until a grant/claim;
   *   - otherwise null (nothing active).
   * Auto-assignment is persisted on the ledger (idempotent), so the
   * choice survives scene restarts + saves.
   * @param {string[]} activeIds the active quest ids, display order
   * @returns {string|null}
   */
  resolvePriority(activeIds) {
    const ids = Array.isArray(activeIds) ? activeIds.filter((x) => typeof x === 'string' && x !== '') : [];
    if (this.priority && ids.includes(this.priority)) return this.priority;
    if (this.priorityCleared) return null;
    const first = ids[0] ?? null;
    if (first) {
      this.priority = first;
      this.priorityCleared = false;
    }
    return first;
  }

  toJSON() {
    return {
      granted: [...this.granted],
      claimed: [...this.claimed],
      priority: this.priority ?? null,
      priorityCleared: this.priorityCleared === true,
    };
  }

  /**
   * Restore a ledger from a save record (SaveData prepareLoad). A
   * malformed record yields an empty ledger rather than a throw — quests
   * are a progression nicety, not a crash vector.
   */
  static fromJSON(data) {
    const st = new QuestState();
    if (!data || typeof data !== 'object') return st;
    const grant = (arr) => (Array.isArray(arr) ? arr.filter((x) => typeof x === 'string') : []);
    for (const id of grant(data.granted)) {
      if (questDef(id)) st.granted.add(id);
    }
    for (const id of grant(data.claimed)) {
      if (st.granted.has(id)) st.claimed.add(id); // claimed ⊆ granted
    }
    // The priority — a save predating it has no field (null). A saved id
    // that is no longer held (or was claimed) is dropped rather than
    // resurrected; the cleared flag survives as stored.
    st.priority =
      typeof data.priority === 'string' && data.priority !== '' &&
      st.granted.has(data.priority) && !st.claimed.has(data.priority)
        ? data.priority
        : null;
    st.priorityCleared = data.priorityCleared === true;
    return st;
  }
}