/**
 * The quest ledger — the run's quest STATE (pure; the data is
 * data/quests.json).
 *
 * A quest's REQUIREMENTS 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. Once a step reads DONE, though, it is
 * RECORDED here (the completed set) and stays DONE — the live read is no
 * longer its source of truth (a step that stands on the home world keeps
 * standing after the ship leaves the home system; a check is monotonic,
 * it can never un-complete). What the ledger owns:
 *
 *   granted   — which quest ids the player HOLDS (the starter quest is
 *               granted on the run's first boot; the run's chain quests are
 *               granted by their unlock requirement — see isUnlockMet / grantUnlocked)
 *   claimed   — which of the held quests have PAID OUT their reward
 *   done      — the checklist steps that have read DONE (keyed by quest id
 *               + the step's stable identity, questCheckKey) with the
 *               detail line they carried when they stood (the dossier's
 *               display); done ⊆ granted, like claimed
 *   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, un-grant a quest, or
 * un-complete a step across a scene restart or a save/load.
 */
import { config } from '../config/Config.js';

/**
 * A checklist step's STABLE identity (data/quests.json → quests[].checks[]):
 * its type + parameters, in sorted key order — independent of the
 * player-facing label and of the data's key order. The ledger's completed
 * set is keyed by it (with the quest id), so a step is recognized across
 * saves even if its label is reworded; label/_comment never count.
 * @param {object} check a quests.json checks[] entry
 * @returns {string} the step's key (never empty)
 */
export function questCheckKey(check) {
  const obj = check && typeof check === 'object' ? check : {};
  const parts = [];
  for (const k of Object.keys(obj).sort()) {
    if (k === 'label' || k === '_comment') continue;
    const v = obj[k];
    parts.push(`${k}=${typeof v === 'object' && v !== null ? JSON.stringify(v) : v}`);
  }
  return parts.length ? parts.join('|') : 'unknown';
}

/** @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);
}

/**
 * The quest's unlock requirement (data/quests.json → quests[].unlocks):
 *   claimed: [ids] — the quests whose rewards must be CLAIMED (the
 *                    ledger's paid-out set) before this one is granted.
 *   acked:   [ids] — the COMMS the run must have ACKed (their ids in the
 *                    run's comms acked-ledger — registry 'commsAcked',
 *                    CommsHub's onAck hook owns it) before this one is
 *                    granted. The acknowledgment itself, not the start
 *                    (the played-ledger marks on the comm's START — a
 *                    chain's final beat can have started and still be
 *                    un-ACKed; 'the payoff comms are DONE' = ACKed).
 * Absent/empty = no requirement (the quest grants on first sight — the
 * boot's own are flagged starter:true instead). Pure: data + the ledger
 * + the caller's `gates` (the scene supplies the acked set — GameScene.
 * _grantUnlockedQuests passes { acked: this._commsAcked() }); a call
 * with no gates fails any quest carrying an acked requirement.
 * @returns {boolean}
 */
export function isUnlockMet(state, id, gates = {}) {
  const def = questDef(id);
  if (!def || !state) return false;
  const req = Array.isArray(def?.unlocks?.claimed) ? def.unlocks.claimed : [];
  if (!req.every((x) => typeof x === 'string' && x !== '' && state.claimed.has(x))) return false;
  const ack = Array.isArray(def?.unlocks?.acked) ? def.unlocks.acked : [];
  if (!ack.length) return true;
  const have =
    gates?.acked instanceof Set
      ? gates.acked
      : new Set(
          Array.isArray(gates?.acked)
            ? gates.acked.filter((x) => typeof x === 'string')
            : [],
        );
  return ack.every((x) => typeof x === 'string' && x !== '' && have.has(x));
}

/**
 * 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.done = new Map(); // "questId\u0000checkKey" → the detail line it stood with
    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);
  }

  /**
   * Grant every not-yet-held quest whose unlock requirement (unlocks.
   * claimed + unlocks.acked — isUnlockMet, the scene's `gates.acked` set
   * supplying the acked half) is met. The starter quests are the boot's
   * own (grant via starterQuestIds on a fresh ledger); this is the RUN's
   * chain — the claim that pays one quest is what arms the next (the
   * scene calls it on the claim + on scene create for loaded saves + on
   * the comm's ACK when the acked half completes last). give() is
   * idempotent, so re-calls are silent no-ops.
   * @param {{acked?: (Set<string>|string[])}} [gates] scene-side gates
   * @returns {string[]} the NEWLY granted ids (data order)
   */
  grantUnlocked(gates = {}) {
    const fresh = [];
    for (const def of questDefs()) {
      if (!def || this.granted.has(def.id) || def.starter === true) continue;
      if (isUnlockMet(this, def.id, gates) && this.give(def.id)) fresh.push(def.id);
    }
    return fresh;
  }

  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;
  }

  // ------------------------------------------------------ completed steps

  /**
   * Record a checklist step as DONE — the monotonic witness (the scene's
   * snapshot calls it the moment a step reads DONE, GameScene.
   * _questCheckView). Idempotent — re-marking keeps the step done and
   * refreshes its detail line while the live read still holds it. Only
   * HELD quests can carry completed steps (done ⊆ granted, the same
   * invariant as claimed ⊆ granted).
   * @param {string} questId a granted quest id
   * @param {string} checkKey the step's stable identity (questCheckKey)
   * @param {string} [detail] the dossier line the step stood with (e.g. "L2/L2")
   * @returns {boolean} true when NEWLY completed
   */
  markCheck(questId, checkKey, detail) {
    const k = this._doneKey(questId, checkKey);
    if (k === null) return false;
    const d = typeof detail === 'string' ? detail : '';
    if (this.done.has(k)) {
      if (this.done.get(k) !== d) this.done.set(k, d);
      return false;
    }
    this.done.set(k, d);
    return true;
  }

  /** Has this quest's checklist step already stood? (the dossier reads it done) */
  isCheckDone(questId, checkKey) {
    const k = this._doneKey(questId, checkKey);
    return k !== null && this.done.has(k);
  }

  /** The detail line the step stood with (the dossier's display) — or null. */
  checkDetail(questId, checkKey) {
    const k = this._doneKey(questId, checkKey);
    return k === null ? null : (this.done.get(k) ?? null);
  }

  /** The completed set's composite key (quest + step) — null when invalid. */
  _doneKey(questId, checkKey) {
    if (typeof questId !== 'string' || questId === '') return null;
    if (typeof checkKey !== 'string' || checkKey === '') return null;
    if (!questDef(questId) || !this.granted.has(questId)) return null;
    return `${questId}\u0000${checkKey}`;
  }

  // ------------------------------------------------------------ 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],
      done: [...this.done].map(([k, detail]) => {
        const [questId, checkKey] = k.split('\u0000');
        return { quest: questId, check: checkKey, detail };
      }),
      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 completed steps (a save predating them has no field → the live
    // evaluation stands alone, exactly as before — old saves load). Only
    // steps of HELD quests survive (done ⊆ granted — markCheck enforces
    // it); a malformed entry degrades rather than throws, and the first
    // record of a step wins (the detail is a display nicety).
    if (Array.isArray(data.done)) {
      for (const e of data.done) {
        if (!e || typeof e.quest !== 'string' || e.quest === '') continue;
        if (typeof e.check !== 'string' || e.check === '') continue;
        const d = typeof e.detail === 'string' ? e.detail : '';
        if (st.isCheckDone(e.quest, e.check)) continue;
        st.markCheck(e.quest, e.check, d);
      }
    }
    // 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;
  }
}