// The CONTESTED (contested regions / frontlines) ability (v0.44.0, #66) as a
// modular LLM-ability (v0.40.0, #67) — a THIRD region state, besides "owned by
// one nation" and "no man's land": a war frontline that is in **no** nation's
// `territory` and not in `unowned`, contested by two or more nations at war.
//
// Each turn the LLM may `open` a region as a contested frontline and/or
// `resolve` an existing one. `open` requires the region to have a SOLE owner
// that is at war with at least one of the parties, or to be no man's land (in
// `unowned`) with two or more of the parties at war with each other; a region
// with two or more owners, or whose owner is not at war with any party, cannot
// be contested (dropped). On a successful open the key is removed from its
// owner's `territory` (sole ownership is preserved — a contested key is in NO
// territory) and from `unowned`, its `regionStats` entry is deleted, and a
// `{ regionKey, parties }` entry (parties = resolved nation ids) is added to
// `GameState.contested` (unique by `regionKey` — re-opening replaces it).
// `resolve` removes the entry and releases the key to no man's land — UNLESS a
// concurrent winning claim by one of the parties (allowed by the
// territory-step guard in engine.ts) already re-owned it, in which case it
// stays owned and its stats are kept.
//
// A still-contested key is NOT a valid normal-claim target: a plain `gain` on
// it is dropped in the territory step (only a resolving party's claim
// re-owns it). The layer NEVER moves a key into two territories (sole
// ownership is sacrosanct), never touches borders directly (the key simply
// leaves ownership), and is deterministic (no hidden randomness — the LLM
// declares, the engine applies fixed rules).
//
// This is a DURABLE ability (unlike the turn-transient hybrid / disasters /
// migration layers): it owns the `GameState.contested` field, and the user
// payload carries the current contested list (only when non-empty).

import { deriveNationStats } from '../../shared/protocol';
import type { ContestedOps, ContestedRegion } from '../../shared/protocol';
// The map-fill constants + tooltip label live in the shared protocol module
// (like the sea-zone / no-man's-land constants); re-exported here so the
// index / engine re-export surface is one consistent place.
export {
  CONTESTED_FILL,
  CONTESTED_STROKE,
  contestedTooltipLabel,
} from '../../shared/protocol';
import type { GameState } from '../../shared/types';
import { atWar } from './apply-helpers';
import { resolveNationRef, resolveRegionKey, str } from './shared';
import type { Ability, AbilityCtx } from './types';

/**
 * (v0.44.0, #66) The SOLE owners of a region key in `next` (a key that is in no
 * nation's `territory` yields `[]`; a corrupt 2+ owner key yields both). Pure.
 */
function currentOwners(next: GameState, key: string): string[] {
  const owners: string[] = [];
  for (const n of Object.values(next.nations)) {
    if (n.territory.includes(key)) owners.push(n.id);
  }
  return owners;
}

/**
 * (v0.44.0, #66) Resolve a region reference (a raw key or a human name) to a
 * concrete region key: exact key first, then a unique case-insensitive name
 * match. With no region-key manifest loaded (`validKeys` undefined) the raw
 * string is accepted as the key (a name cannot be resolved without the
 * manifest). Returns `null` when the reference is empty or unresolvable.
 */
function resolveKey(
  ref: string,
  validKeys?: ReadonlySet<string>,
  nameOf?: (key: string) => string | undefined,
): string | null {
  const r = (ref ?? '').trim();
  if (!r) return null;
  if (!validKeys) return r; // no manifest: accept the raw key as-is
  return resolveRegionKey(r, validKeys, nameOf ?? (() => undefined));
}

/**
 * (v0.44.0, #66) Resolve a list of party references to distinct nation ids
 * (id first, then a case-insensitive unique name), preserving first-appearance
 * order. An unresolvable ref is dropped. Pure.
 */
function resolveParties(next: GameState, refs: string[]): string[] {
  const out: string[] = [];
  for (const ref of refs) {
    const id = resolveNationRef(next, ref);
    if (id && !out.includes(id)) out.push(id);
  }
  return out;
}

/**
 * (v0.44.0, #66) Re-derive a nation's aggregate `stats` from its regions'
 * per-region stats, with the same 0-region / no-entry guards as the engine's
 * main recompute (a nation with no region, or none with a stats entry, keeps
 * its directly-mutated `stats`). Used after a contested open strips a region
 * from its owner. Never throws.
 */
function rederiveOwnerStats(
  next: GameState,
  ownerId: string,
  geoOf?: (key: string) => { area: number; population: number } | undefined,
): void {
  const n = next.nations[ownerId];
  if (!n) return;
  if (n.territory.length > 0 && n.territory.some((k) => next.regionStats[k])) {
    n.stats = deriveNationStats(n.territory, next.regionStats, geoOf);
  }
}

/**
 * (v0.44.0, #66) Validate the raw `contested` field of a turn into a safe
 * {@link ContestedOps}. Defensive like the rest of the parser — never throws.
 * `open`: each op needs a non-empty `regionKey` (capped at 120 chars) and
 * TWO OR MORE non-empty `parties` refs (each capped at 200 chars); an op with
 * a missing `regionKey` or fewer than two party refs is dropped. `resolve`:
 * each entry is a non-empty region key (capped at 120 chars); empty / non-
 * string entries are dropped. Both region keys and party refs are kept RAW
 * here (like the hybrid / economy / industry refs) — whether a ref resolves to
 * a real region / nation, and whether the war-linkage / ownership conditions
 * hold, is checked at apply time (a ref that does not resolve, or a region that
 * is not contestable, is dropped there). A missing / malformed top-level object
 * yields `{ open: [], resolve: [] }`.
 */
export function validateContestedOps(raw: unknown): ContestedOps {
  const out: ContestedOps = { open: [], resolve: [] };
  if (!raw || typeof raw !== 'object' || Array.isArray(raw)) return out;
  const o = raw as Record<string, unknown>;
  if (Array.isArray(o.open)) {
    for (const e of o.open) {
      if (!e || typeof e !== 'object') continue;
      const p = e as Record<string, unknown>;
      const regionKey = str(p.regionKey, 120);
      if (!regionKey) continue; // missing / empty region key: drop
      if (!Array.isArray(p.parties)) continue; // missing / malformed parties: drop
      const parties = p.parties
        .map((x) => str(x, 200))
        .filter((x): x is string => x !== null);
      if (parties.length < 2) continue; // need at least two party refs
      out.open.push({ regionKey, parties });
    }
  }
  if (Array.isArray(o.resolve)) {
    for (const e of o.resolve) {
      const key = str(e, 120);
      if (key) out.resolve.push(key);
    }
  }
  return out;
}

/**
 * (v0.44.0, #66) Apply the turn's contested-region ops to `next`, mutating in
 * place and never throwing. Runs in the `ABILITIES` loop AFTER the territory
 * step and the derived-stats recompute, and BEFORE markers / nationOps, so the
 * owner / unowned / wars it inspects are all final for this turn.
 *
 *  (1) RESOLVE (first): each key in `resolve` that is currently contested is
 *      removed from `next.contested` and released to no man's land (into
 *      `unowned`, out of any territory, `regionStats` deleted) — UNLESS a
 *      concurrent winning claim by one of the parties (the only claim the
 *      territory step permits on a contested key) already re-owned it, in
 *      which case it stays owned and keeps (or re-inits) its stats.
 *  (2) OPEN: each op that resolves to a contestable region (a sole owner at
 *      war with a party, or a no-man's-land region whose parties are at war
 *      with each other) is moved out of ownership (the owner's territory /
 *      `unowned`), its `regionStats` is deleted, and it is added to
 *      `next.contested` (unique by `regionKey` — an open replaces a kept
 *      entry for the same key). The stripped owner's derived stats are
 *      re-derived.
 *
 * A contested key is never placed into two territories and is never left in
 * `unowned` (the two states are mutually exclusive), so the sole-ownership
 * invariant holds after every op.
 */
export function applyContested(next: GameState, ops: ContestedOps, ctx: AbilityCtx): void {
  const validKeys = ctx.validRegionKeys;
  const nameOf = ctx.regionNameOf;
  const geoOf = ctx.geoOf;
  const open = Array.isArray(ops?.open) ? ops.open : [];
  const resolve = Array.isArray(ops?.resolve) ? ops.resolve : [];
  const prevContested = Array.isArray(next.contested) ? next.contested : [];

  // (1) RESOLVE first: rebuild the kept list, dropping resolved keys. A
  // resolved key is released to no man's land unless a party re-owned it.
  const resolveSet = new Set(resolve);
  const kept: ContestedRegion[] = [];
  for (const c of prevContested) {
    if (!resolveSet.has(c.regionKey)) {
      kept.push(c); // not resolved this turn: keep
      continue;
    }
    const owners = currentOwners(next, c.regionKey);
    if (owners.length === 1 && c.parties.includes(owners[0])) {
      // A party re-owned it via a concurrent winning claim (the territory step
      // allowed it): keep it owned, ensure it has stats (the claim re-inits an
      // absent entry; the post-claim recompute already reflected the gain).
      if (!next.regionStats[c.regionKey]) {
        next.regionStats[c.regionKey] = { ...next.nations[owners[0]].stats };
      }
      continue; // stays owned — not re-added to `contested`
    }
    // Release to no man's land: out of any territory (defensive — a contested
    // key is normally in none), into `unowned`, and its per-region stats leave.
    for (const n of Object.values(next.nations)) {
      const i = n.territory.indexOf(c.regionKey);
      if (i !== -1) n.territory.splice(i, 1);
    }
    if (!next.unowned.includes(c.regionKey)) next.unowned.push(c.regionKey);
    delete next.regionStats[c.regionKey];
  }

  // (2) OPEN: each op that resolves to a contestable region is moved out of
  // ownership and added to the contested list (unique by region key).
  const opened = new Map<string, string[]>(); // region key -> resolved party ids
  for (const op of open) {
    const key = resolveKey(op.regionKey, validKeys, nameOf);
    if (!key) continue;
    const parties = resolveParties(next, op.parties);
    if (parties.length < 2) continue; // fewer than two distinct resolved parties

    const owners = currentOwners(next, key);
    let ok = false;
    if (owners.length === 1) {
      // Sole owner present: the owner must be at war with at least one party
      // (the owner may itself be a party — atWar is false for a==b, so this
      // checks the owner against the OTHER parties).
      ok = parties.some((p) => atWar(next.wars, owners[0], p));
    } else if (owners.length === 0 && next.unowned.includes(key)) {
      // No owner + no man's land: two of the parties must be at war with
      // each other.
      for (let i = 0; i < parties.length && !ok; i++) {
        for (let j = i + 1; j < parties.length; j++) {
          if (atWar(next.wars, parties[i], parties[j])) {
            ok = true;
            break;
          }
        }
      }
    }
    // Two or more owners (corrupt), an owner not at war with any party, or a
    // not-in-unowned keyless region: never contestable (dropped).
    if (!ok) continue;

    if (owners.length === 1) {
      const n = next.nations[owners[0]];
      const i = n.territory.indexOf(key);
      if (i !== -1) n.territory.splice(i, 1);
      rederiveOwnerStats(next, owners[0], geoOf);
    } else {
      const i = next.unowned.indexOf(key);
      if (i !== -1) next.unowned.splice(i, 1);
    }
    delete next.regionStats[key];
    opened.set(key, parties);
  }

  // Rebuild `next.contested`: the kept (unresolved) entries plus the newly
  // opened ones, unique by region key (an open replaces a kept entry for the
  // same key; a resolve removed its key from `kept` above).
  const final: ContestedRegion[] = [];
  const seen = new Set<string>();
  for (const c of kept) {
    if (opened.has(c.regionKey)) continue; // replaced by a re-open this turn
    if (seen.has(c.regionKey)) continue; // dedupe (should not happen, but safe)
    seen.add(c.regionKey);
    final.push(c);
  }
  for (const [key, parties] of opened) {
    if (seen.has(key)) continue;
    seen.add(key);
    final.push({ regionKey: key, parties });
  }
  next.contested = final;
}

export const contested: Ability<'contested'> = {
  field: 'contested',
  default: () => ({ open: [], resolve: [] }),
  validate: (raw) => validateContestedOps(raw),
  apply: (state, data, ctx) => applyContested(state, data, ctx),
  schemaLine: () =>
    '  "contested": {"open":[{"regionKey":"<region key>","parties":["<nation 1>","<nation 2>"]}],"resolve":["<region key>"]},',
  constraint: () =>
    '- Contested regions ("contested") are WAR FRONTLINES: a region that no nation controls and that is not no man\'s land, contested by two or more nations at war. An "open" op ({"regionKey":"<key>","parties":["<a>","<b>"]}) makes a region a frontline — it leaves its owner\'s territory (or no-man\'s-land) and is contested: the region\'s sole owner must be at war with at least one of the parties, or (for a no-man\'s-land region) two of the parties must be at war with each other. A "resolve" op (["<key>"]) ends a frontline, releasing the region to no man\'s land — unless a party\'s concurrent claim re-owns it. A contested region is in NO nation\'s territory (never two) and is never no man\'s land while contested. The user message\'s "contested" field lists the current frontlines (region key + party names). Propose at most 1-2 contested-region changes per turn and narrate each one in "events" (a "military" event).',
  isMeaningful: (data) => data.open.length > 0 || data.resolve.length > 0,
  stateFields: ['contested'],
  stub: () => ({ open: [], resolve: [] }),
  // The user payload carries the current contested frontlines (region key +
  // party NAMES, resolved from the stored ids) — but only when non-empty (a
  // fresh / no-frontline world contributes nothing, like the turn-transient
  // layers).
  payload: (ctx) => {
    if (!ctx.contested || ctx.contested.length === 0) return {};
    return {
      contested: ctx.contested.map((c) => ({
        regionKey: c.regionKey,
        parties: c.parties.map((id) => ctx.state.nations[id]?.name ?? id),
      })),
    };
  },
};