// The DISASTERS & PANDEMICS ability (v0.41.0, #63) as a modular LLM-ability
// (v0.40.0, #67). Natural and man-made catastrophes — earthquakes, floods,
// volcanic eruptions, wildfires, famines, plagues, and epidemics — hit a
// nation or a single region each turn. Unlike most other abilities this one
// is **turn-transient**: it owns NO `GameState` field (no durable list, no
// `db.ts` change) — exactly like the hybrid layer. Each event carries a
// `type` and a `severity`, and the engine applies a DETERMINISTIC stat dip
// chosen from the `(type, severity)` lookup table below (no hidden
// randomness — the LLM chooses the type and severity, the table decides the
// magnitude). The dip lands on the target nation's `stats` (clamped 0–100)
// AND on the target's regions (`regionStats` — the single named region when
// the target was a region key, otherwise every region the target owns), and
// the target's derived `stats` are re-derived afterwards (the same 0-region /
// no-entry guards as hybrid / economy / industry, so a 0-region nation keeps
// its directly-mutated value and the dip persists to the next turn). The
// target is a nation (resolved by the shared `resolveNationRef`) or a region
// key (which hits its SOLE owner); a key with 0 or 2+ owners is untargetable.
// There is no acting-nation (`from`) field on a disaster — a catastrophe is
// not an attack, so the hybrid's self-target drop does not apply. Malformed
// events and unresolvable targets are dropped, never thrown.

import { clampStat, deriveNationStats } from '../../shared/protocol';
import type {
  DisasterEvent,
  DisasterSeverity,
  DisasterType,
} from '../../shared/protocol';
import type { GameState, Nation, NationStats, StatKey } from '../../shared/types';
import { resolveNationRef, str } from './shared';
import type { Ability } from './types';

/** The seven disaster types a turn can declare (v0.41.0, #63). */
export const DISASTER_TYPES: readonly DisasterType[] = [
  'earthquake',
  'flood',
  'volcanic',
  'wildfire',
  'famine',
  'plague',
  'epidemic',
];

/** The three severity levels a disaster event can carry (v0.41.0, #63). */
export const DISASTER_SEVERITIES: readonly DisasterSeverity[] = ['minor', 'moderate', 'severe'];

const VALID_DISASTER_TYPES = new Set<string>(DISASTER_TYPES);
const VALID_SEVERITIES = new Set<string>(DISASTER_SEVERITIES);

/** True when `t` is one of the seven known disaster types (v0.41.0, #63). */
export function isDisasterType(t: unknown): t is DisasterType {
  return typeof t === 'string' && VALID_DISASTER_TYPES.has(t);
}

/** True when `s` is one of the three known disaster severities (v0.41.0, #63). */
export function isDisasterSeverity(s: unknown): s is DisasterSeverity {
  return typeof s === 'string' && VALID_SEVERITIES.has(s);
}

/**
 * (v0.41.0, #63) The DETERMINISTIC per-`(type, severity)` stat dip of a
 * disaster event. Each pair maps to a small set of signed (negative) stat
 * deltas: no hidden randomness — the LLM picks the type and severity, the
 * table decides the magnitude. Population is never touched (a disaster hurts
 * military / economy / stability, never the head-count). Every (type,
 * severity) combination dips at least one stat (none is purely
 * informational).
 */
export const DISASTER_EFFECTS: Record<DisasterType, Record<DisasterSeverity, Partial<Record<StatKey, number>>>> = {
  earthquake: {
    minor: { stability: -2, economy: -2 },
    moderate: { stability: -4, economy: -4 },
    severe: { stability: -7, economy: -7 },
  },
  flood: {
    minor: { economy: -2, stability: -1 },
    moderate: { economy: -3, stability: -2 },
    severe: { economy: -6, stability: -4 },
  },
  volcanic: {
    minor: { economy: -2, stability: -2 },
    moderate: { economy: -4, stability: -3 },
    severe: { economy: -7, stability: -6 },
  },
  wildfire: {
    minor: { economy: -2 },
    moderate: { economy: -4 },
    severe: { economy: -7 },
  },
  famine: {
    minor: { economy: -2, stability: -2 },
    moderate: { economy: -4, stability: -4 },
    severe: { economy: -7, stability: -7 },
  },
  plague: {
    minor: { stability: -3, military: -2 },
    moderate: { stability: -5, military: -3 },
    severe: { stability: -9, military: -6 },
  },
  epidemic: {
    minor: { stability: -2, military: -1 },
    moderate: { stability: -4, military: -2 },
    severe: { stability: -7, military: -4 },
  },
};

/**
 * (v0.41.0, #63) Validate the raw `disasters` field of a turn into a safe
 * list of {@link DisasterEvent}s. Defensive like the rest of the parser — never throws.
 * The raw value may be the object `{ events: [...] }` (the TurnResult shape)
 * or a bare array (be lenient about either). Each event needs a known `type`
 * (one of {@link DISASTER_TYPES}), a known `severity` (one of
 * {@link DISASTER_SEVERITIES}), and a non-empty `target` (a nation id/name or
 * a region key, capped at 200 chars); a non-empty `detail` is capped at 300
 * chars. An event with an unknown / missing `type`, an unknown / missing
 * `severity`, or an empty `target` is dropped. Resolution of `target` to a
 * concrete nation (or a region's sole owner) happens at apply time
 * (`applyDisasterEvent`), not here. A missing / malformed top-level value
 * yields `{ events: [] }`.
 */
export function validateDisasterEvents(raw: unknown): DisasterEvent[] {
  let list: unknown[] | null = null;
  if (Array.isArray(raw)) {
    list = raw;
  } else if (raw && typeof raw === 'object') {
    const inner = (raw as Record<string, unknown>).events;
    if (Array.isArray(inner)) list = inner;
  }
  if (!list) return [];
  const out: DisasterEvent[] = [];
  for (const e of list) {
    if (!e || typeof e !== 'object') continue;
    const o = e as Record<string, unknown>;
    if (!isDisasterType(o.type)) continue; // unknown / missing type: drop
    if (!isDisasterSeverity(o.severity)) continue; // unknown / missing severity: drop
    const target = str(o.target, 200);
    if (!target) continue; // empty / missing target: drop
    const detail = str(o.detail, 300);
    out.push({
      type: o.type,
      target,
      severity: o.severity,
      ...(detail ? { detail } : {}),
    });
  }
  return out;
}

/**
 * (v0.41.0, #63) Resolve a disaster event's `target` (a nation id/name OR a
 * region key) to the concrete nation it affects. A nation ref resolves via
 * {@link resolveNationRef}; a region key resolves to its SOLE owner (a region
 * with zero or 2+ owners can't be a valid target). Returns the affected
 * nation plus the specific region key (when the target was a region) so the
 * dip can land on just that region's entry. `validKeys` (when supplied)
 * gates the region-key path; a ref that is neither a known nation nor a
 * valid region key returns `null`. Pure; never throws.
 *
 * NOTE: there is no acting-nation (`from`) field on a disaster — a
 * catastrophe is not an attack, so (unlike the hybrid layer) a self-target
 * drop does NOT apply: an earthquake can hit the nation it is declared
 * against.
 */
function resolveDisasterTarget(
  state: GameState,
  target: string,
  validKeys?: ReadonlySet<string>,
): { nation: Nation; regionKey?: string } | null {
  const id = resolveNationRef(state, target);
  if (id !== null) {
    const n = state.nations[id];
    return n ? { nation: n } : null;
  }
  const key = (target ?? '').trim();
  if (!key) return null;
  if (validKeys && !validKeys.has(key)) return null; // unknown region key
  const owners = Object.values(state.nations).filter((n) => n.territory.includes(key));
  if (owners.length !== 1) return null; // 0 or 2+ owners: not a targetable region
  return { nation: owners[0], regionKey: key };
}

/** Apply each signed dip in `dips` to a stats record in place (clamped). */
function applyDips(stats: NationStats, dips: Partial<Record<StatKey, number>>): void {
  (Object.keys(dips) as StatKey[]).forEach((k) => {
    const d = dips[k];
    if (typeof d === 'number') stats[k] = clampStat(stats[k] + d);
  });
}

/**
 * (v0.41.0, #63) Apply ONE disaster event to the (cloned) `next` state,
 * mutating it in place and never throwing. Resolution order:
 *   1. `target` must resolve to a concrete nation (a nation ref, or a region
 *      key's sole owner); an unresolvable target (unknown / ambiguous ref, a
 *      region with 0 or 2+ owners, or an unknown region key) drops the event.
 * Then the deterministic `(type, severity)` dip from {@link DISASTER_EFFECTS}
 * is applied:
 *   - the target nation's `stats` is dipped on each affected stat (clamped
 *     0–100);
 *   - the dip is mirrored to the target's regions — the single named region
 *     when the target was a region key, otherwise every region the target
 *     owns (regions with no `regionStats` entry are skipped);
 *   - the target nation's derived `stats` are re-derived afterwards (the
 *     same 0-region / no-entry guards as the main recompute, so a 0-region
 *     nation keeps its directly-mutated value and a dip persists).
 * A disaster never moves territory (sole ownership is untouched) and never
 * touches `population`.
 */
export function applyDisasterEvent(
  next: GameState,
  ev: DisasterEvent,
  geoOf?: (key: string) => { area: number; population: number } | undefined,
  validKeys?: ReadonlySet<string>,
): void {
  const target = resolveDisasterTarget(next, ev.target, validKeys);
  if (target === null) return; // unresolvable target: drop
  const dips = DISASTER_EFFECTS[ev.type][ev.severity];
  if (!dips) return; // defensive: unknown (type, severity) pair
  applyDips(target.nation.stats, dips);
  if (target.regionKey !== undefined) {
    const rs = next.regionStats[target.regionKey];
    if (rs) applyDips(rs, dips);
  } else {
    for (const key of target.nation.territory) {
      const rs = next.regionStats[key];
      if (!rs) continue; // a key with no entry is skipped
      applyDips(rs, dips);
    }
  }
  // Re-derive the target nation's aggregate stats so the dip persists (the
  // main recompute ran earlier this turn; without this the dip would be
  // washed out next turn). Same 0-region / no-entry guards as hybrid /
  // economy: a nation with no region stats entry keeps its directly-mutated
  // `stats`.
  if (target.nation.territory.length > 0 && target.nation.territory.some((k) => next.regionStats[k])) {
    target.nation.stats = deriveNationStats(target.nation.territory, next.regionStats, geoOf);
  }
}

export const disasters: Ability<'disasters'> = {
  field: 'disasters',
  default: () => ({ events: [] }),
  // The low-level validator returns a bare list; the field's shape is the
  // `{ events }` object (mirrors the historical TurnResult shape).
  validate: (raw) => ({ events: validateDisasterEvents(raw) }),
  apply: (state, data, ctx) => {
    for (const ev of data.events) {
      applyDisasterEvent(state, ev, ctx.geoOf, ctx.validRegionKeys);
    }
  },
  schemaLine: () =>
    '  "disasters": {"events":[{"type":"<earthquake|flood|volcanic|wildfire|famine|plague|epidemic>","target":"<nation id or name, or region key>","severity":"<minor|moderate|severe>","detail":"<short detail>"}]},',
  constraint: () =>
    '- Disasters & pandemics ("disasters.events") are natural and man-made catastrophes — earthquakes, floods, volcanic eruptions, wildfires, famines, plagues, and epidemics — that hit a nation or a single region this turn. Each event names a "target" (a nation id / name, or a region key that hits that region\'s SOLE owner — a region with 0 or 2+ owners can\'t be hit) and a "severity" (minor / moderate / severe); the engine applies a small, DETERMINISTIC stat dip from the (type, severity) table (a severe plague is the hardest hit; none of them touch population, and none move borders — sole ownership is untouched). There is NO memory of past disasters (the layer is turn-transient): a plague or epidemic that persists is simply RE-DECLARED each turn it continues, with a fresh "severity". Propose at most 1-2 events per turn and narrate each one in "events" (a "disaster" event).',
  isMeaningful: (data) => data.events.length > 0,
  stub: () => ({ events: [] }),
  // The layer is turn-transient — it contributes nothing to the user payload
  // (no durable state to show the model), so the payload is always empty.
  payload: () => ({}),
};