/**
 * ENCOUNTER DIRECTOR — the periodic random ship encounters in neutral
 * wild space. Pure rules, no Phaser, no scene (the same contract as
 * js/combat/XpManager.js — it runs in bare Node; dev/encounters.test.mjs
 * drives it with a fake clock + an injected rng).
 *
 * WHAT IT DECIDES (GameScene does the spawning):
 *
 *   WHEN — while the system allows encounters (NEUTRAL — faction null —,
 *     or a FACTION system with a war context (the local faction + one of
 *     its rivals — never pirates/neutrals)), not home, no wave run in
 *     flight, the player upright; the scene passes `ctx.allowed`,
 *     `encounterAllowed` is the pure gate) AND the scene's own quest hold
 *     stands off — GameScene ANDs in `_encountersLockedByQuest`, the
 *     'Special Delivery' gate: the rolls stay off until that quest is
 *     completed and claimed (a scene-side state, so it never crosses this
 *     module's pure contract). A roll then lands on the interval schedule
 *     (data/combat.json → encounters.rollIntervalMin..rollIntervalMax,
 *     seconds — in FACTION space `ctx.faction === true` and the tighter
 *     encounters.faction.rollIntervalMin..rollIntervalMax stand), each
 *     roll fires at chanceMin..chanceMax probability. ONE AT A TIME: the
 *     schedule holds while an encounter is engaged.
 *
 *   QUIET — when the encounter ends (its ships all dead or off-screen →
 *     the scene reports ctx.live = false) the next roll waits out
 *     cooldownMin..cooldownMax seconds (or
 *     encounters.faction.cooldownMin..cooldownMax in faction space), and
 *     the cadence resumes from there.
 *
 *   WHAT — `rollKind` picks the kind at `weights` (shipped even — ~1/3
 *     each), and `compose` sizes the group off the player's combat
 *     level band (shipped: 1–2 ships at low levels, 4–5 at high; mixed
 *     keeps BOTH kinds present). FACTION SPACE: both groups are sized
 *     off the band's pirate count, one per faction.
 *
 * IT OWNS NO SHIPS, NO AUDIO, NO SAVE STATE — scene-local, like the
 * 'Pirate Problems' ambush: a fresh GameScene starts a fresh director.
 */

/** Uniform float in [min, max] (a degenerate band just returns the value). */
function rand(rng, min, max) {
  const a = Math.min(min, max);
  const b = Math.max(min, max);
  return a + rng() * (b - a);
}

/** Uniform INT in [lo, hi] inclusive (a degenerate band is that value). */
function randInt(rng, lo, hi) {
  let a = Math.max(0, Math.floor(Number(lo) || 0));
  let b = Math.max(0, Math.floor(Number(hi) || 0));
  if (b < a) [a, b] = [b, a];
  return Math.min(b, a + Math.floor(rng() * (b - a + 1)));
}

const KINDS = ['pirates', 'neutrals', 'mixed', 'faction'];

/**
 * The encounter kind at `weights` (data/combat.json → encounters.weights;
 * shipped even — ~1/3 each). A zero/absent weight is just never rolled.
 * @param {object} weights kind → weight
 * @param {() => number} rng
 * @returns {'pirates'|'neutrals'|'mixed'}
 */
export function rollKind(weights, rng) {
  const w = weights && typeof weights === 'object' ? weights : {};
  const total = KINDS.reduce((s, k) => s + Math.max(0, Number(w[k]) || 0), 0);
  if (total <= 0) return KINDS[0];
  let x = rng() * total;
  for (const k of KINDS) {
    x -= Math.max(0, Number(w[k]) || 0);
    if (x < 0) return k;
  }
  return KINDS[KINDS.length - 1];
}

/**
 * The size band for a combat level (data/combat.json →
 * encounters.bands — minLevel..maxLevel, inclusive). A level past every
 * band takes the LAST one (the top of the roster).
 * @param {object[]} bands
 * @param {number} level
 * @returns {object|null}
 */
export function bandFor(bands, level) {
  const lv = Math.max(0, Math.floor(Number(level) || 0));
  const list = Array.isArray(bands) ? bands : [];
  for (const b of list) {
    if (b && lv >= (Number(b.minLevel) || 0) && lv <= (Number(b.maxLevel) || 0)) return b;
  }
  return list.length ? list[list.length - 1] : null;
}

const DEFAULT_BAND = {
  pirates: [1, 2],
  neutrals: [1, 2],
  mixedPirates: [1, 1],
  mixedNeutrals: [1, 1],
};

/**
 * A band's pirate ROSTER as type → weight entries: a `{ type: weight }`
 * object (the tiers' weighted mixes) or an array of type ids (equal
 * weight). Unknown ids are left to the spawn side (a roster typo degrades
 * to the base craft there — the EnemyTypes.js rule); a roster that
 * empties yields null (the scene then picks its own way).
 * @returns {?Array<[string, number]>} | null
 */
function rosterEntries(band) {
  const raw = band?.roster;
  const out = [];
  if (Array.isArray(raw)) {
    for (const t of raw) {
      const k = String(t).trim();
      if (k !== '') out.push([k, 1]);
    }
  } else if (raw && typeof raw === 'object' && !Array.isArray(raw)) {
    for (const [t, w] of Object.entries(raw)) {
      const k = String(t).trim();
      const wt = Number(w);
      if (k !== '' && Number.isFinite(wt) && wt > 0) out.push([k, wt]);
    }
  }
  return out.length > 0 ? out : null;
}

/** Draw `n` type ids from the band's roster (weighted, with replacement). Null when the band carries none. */
function drawRoster(band, n, rng) {
  const entries = rosterEntries(band);
  if (!entries) return null;
  const sum = entries.reduce((a, [, w]) => a + w, 0);
  const out = [];
  for (let i = 0; i < n; i++) {
    let x = rng() * sum;
    let pick = entries[0][0];
    for (const [t, w] of entries) {
      x -= w;
      if (x <= 0) {
        pick = t;
        break;
      }
    }
    out.push(pick);
  }
  return out;
}

/**
 * The encounter's composition — the kind at `weights`, the group sized
 * off the level band. `pirates`/`neutrals` are the per-kind counts
 * (the OTHER kind is 0); `mixedPirates`/`mixedNeutrals` are the mixed
 * per-kind floors/ceilings — BOTH kinds stay present. `pirateTypes` (new)
 * — the band's weighted ROSTER drawn out to the pirate count (the tiers
 * mix their types — a band without a roster leaves it unset and the scene
 * picks as it always did).
 *
 * FACTION SPACE (`context`, new — the war-zones): `context` of
 * `{ mode: 'faction', local: { id, types: [...] }, enemies: [{ id,
 * types: [...] }] }` (the scene builds it — this module stays
 * roster-free): the roll is ALWAYS a FACTION kind — the LOCAL faction
 * (the system's controller) AND one of the OTHER factions (never
 * pirates or neutrals), EACH group sized off the band's pirate count
 * (independent rolls) with its types drawn from THAT faction's roster
 * (repeated for the count — the scene spawns `types[i % types.length]`).
 * A context with no local roster or no rostered rival degrades to the
 * neutral roll (defensive).
 *
 * @param {object} cfg the encounters section (data/combat.json)
 * @param {number} xpLevel the player's combat level (a fresh run: 0)
 * @param {() => number} rng
 * @param {object} [context] the space's encounter context (see above)
 * @returns {{kind:string, pirates:number, neutrals:number, pirateTypes?:string[],
 *           faction?:string, groups?:Array<{id:string, count:number, types:string[]}>}}
 */
export function compose(cfg, xpLevel, rng, context = null) {
  const rostered = (e) => e && Array.isArray(e.types) && e.types.length > 0;
  if (
    context &&
    context.mode === 'faction' &&
    rostered(context.local) &&
    Array.isArray(context.enemies) &&
    context.enemies.some(rostered)
  ) {
    const live = context.enemies.filter(rostered);
    const pick = live[Math.floor(rng() * live.length) % live.length];
    const band = bandFor(cfg && cfg.bands, xpLevel) || DEFAULT_BAND;
    const group = (roster) => {
      const b = Array.isArray(band.pirates) ? band.pirates : [1, 1];
      const n = randInt(rng, b[0], b[1]);
      const types = [];
      for (let i = 0; i < n; i++) types.push(roster.types[i % roster.types.length]);
      return { id: String(roster.id), count: n, types };
    };
    const home = group(context.local);
    const rival = group(pick);
    return {
      kind: 'faction',
      faction: home.id,
      groups: [home, rival],
      pirates: home.count + rival.count,
      neutrals: 0,
    };
  }
  const cfg2 = cfg && typeof cfg === 'object' ? cfg : {};
  const band = bandFor(cfg2.bands, xpLevel) || DEFAULT_BAND;
  const ri = (key, fb) =>
    Array.isArray(band[key]) ? randInt(rng, band[key][0], band[key][1]) : randInt(rng, fb[0], fb[1]);
  const kind = rollKind(cfg2.weights, rng);
  const types = (n) => drawRoster(band, n, rng);
  if (kind === 'pirates') {
    const n = ri('pirates', [1, 2]);
    const pt = types(n);
    return { kind, pirates: n, neutrals: 0, ...(pt ? { pirateTypes: pt } : {}) };
  }
  if (kind === 'neutrals') return { kind, pirates: 0, neutrals: ri('neutrals', [1, 2]) };
  const np = ri('mixedPirates', [1, 1]);
  const nt = ri('mixedNeutrals', [1, 1]);
  const pt = types(np);
  return { kind: 'mixed', pirates: np, neutrals: nt, ...(pt ? { pirateTypes: pt } : {}) };
}

/**
 * The pure gate (GameScene passes its state; the test passes fixtures):
 * encounters host in NEUTRAL (faction == null) non-HOME space — or in a
 * FACTION system that carries a war context (the scene's
 * `_encounterContext` — the controller's rivals with rosters; the roll
 * there is always an opposing faction, never pirates/neutrals) — with no
 * wave run in flight (a run that is already done/cancelled is over —
 * its ships are spent), and the player upright (no spawn on a downed
 * ship). `ship` must stand — there is no flying without one.
 * @param {object} gate { ship, isHomeSystem, faction, factionContext, waveRunLive, playerDown }
 * @returns {boolean}
 */
export function encounterAllowed(gate = {}) {
  return (
    !!gate.ship &&
    gate.isHomeSystem !== true &&
    (gate.faction == null || gate.factionContext != null) &&
    gate.waveRunLive !== true &&
    gate.playerDown !== true
  );
}

/**
 * The director's clock (one per GameScene — `this.encounters`).
 *
 *   update(time, ctx)  →  { kind, pirates, neutrals } | null
 *
 *   ctx.allowed — the pure gate above (the scene decides)
 *   ctx.live    — an encounter's ships are still up (CombatSystem.active)
 *   ctx.xpLevel — the player's combat level (the size bands)
 *   ctx.faction — true in FACTION space (the roll takes the
 *                 encounters.faction interval + quiet; the scene passes
 *                 its war context on ctx.context for compose)
 *
 * `time` is the scene clock (ms — Phaser's `time`, the same ms clock the
 * combat's own nextFireAt/respawn clocks run on).
 */
export class EncounterDirector {
  constructor(cfg, opts = {}) {
    this.cfg = cfg && typeof cfg === 'object' ? cfg : {};
    this.rng = typeof (opts && opts.rng) === 'function' ? opts.rng : Math.random;
    this.state = 'idle'; // 'idle' | 'engaged' | 'cooldown'
    this.nextRollAt = null; // ms clock; null = the first schedule is pending
    this.quietUntil = 0; // ms clock (the cooldown's end)
  }

  _intervalMs(src) {
    // BOTH bounds in the SAME unit (seconds) before scaling to ms: clamping
    // max to >= min must compare like-with-like, or the band's top collapses to
    // min*1000 (a 45–90 s roll becomes 45 s–12.5 h). Regression-guarded in
    // dev/encounters.test.mjs (rng=0 lower bound, rng=1 upper bound).
    // `src` — the FACTION SPACE's own schedule (data/combat.json →
    // encounters.faction) when the roll lands in faction territory;
    // absent, the neutral-space schedule stands.
    const c = src && typeof src === 'object' ? src : this.cfg;
    const minS = Math.max(0, Number(c.rollIntervalMin) || 45);
    const maxS = Math.max(minS, Number(c.rollIntervalMax) || 90);
    return rand(this.rng, minS * 1000, maxS * 1000);
  }

  _cooldownMs(src) {
    const c = src && typeof src === 'object' ? src : this.cfg;
    const minS = Math.max(0, Number(c.cooldownMin) || 30);
    const maxS = Math.max(minS, Number(c.cooldownMax) || 60);
    return rand(this.rng, minS * 1000, maxS * 1000);
  }

  _chance() {
    const min = Math.min(1, Math.max(0, Number(this.cfg.chanceMin) ?? 0.5));
    const max = Math.min(1, Math.max(min, Number(this.cfg.chanceMax) ?? 0.6));
    return rand(this.rng, min, max);
  }

  /** One tick of the encounter clock (see the class doc). `ctx.faction`
   *  true = the roll lands in FACTION space — the encounters.faction
   *  schedule (its own interval + quiet) stands instead of the
   *  neutral-space one. */
  update(time, ctx = {}) {
    if (this.cfg.enabled === false) return null; // the data can hold it off
    time = Number(time) || 0;
    // The schedule source (faction space's tighter timers, or the
    // neutral-space one) — sampled per tick, so a scene that swaps
    // systems flips the cadence with it.
    const fac =
      ctx.faction === true && this.cfg.faction && typeof this.cfg.faction === 'object'
        ? this.cfg.faction
        : null;

    if (this.state === 'engaged') {
      if (ctx.live !== true) {
        this.state = 'cooldown';
        this.quietUntil = time + this._cooldownMs(fac);
      }
      return null; // one at a time: the schedule holds while it's live
    }

    if (this.state === 'cooldown') {
      if (time < this.quietUntil) return null;
      this.state = 'idle';
      this.nextRollAt = this.quietUntil; // the cadence resumes on the quiet's end
    }

    // 'idle'
    if (this.nextRollAt === null) {
      this.nextRollAt = time + this._intervalMs(fac);
      return null;
    }
    if (ctx.allowed !== true) {
      // Out of allowed space (home / a wave run): the clock SLIDES — the
      // first roll here lands a full interval out, never on the arrival
      // frame.
      this.nextRollAt = time + this._intervalMs(fac);
      return null;
    }
    if (time < this.nextRollAt) return null;
    this.nextRollAt = time + this._intervalMs(fac);
    if (this.rng() < this._chance()) {
      this.state = 'engaged';
      return compose(this.cfg, ctx.xpLevel ?? 0, this.rng, ctx.context ?? null);
    }
    return null;
  }
}