import { Game, available, key, opposite, random, rotateBoard, solveRotations, trace, validateLevel } from './core.js';
import { exitTiming } from './exit-animation.js';
import { MOTION } from './design-tokens.js';

const positionKey = tile => `${tile.q},${tile.r}`;
const countBends = route => route.steps.filter(step => step.enter !== null && opposite(step.enter) !== step.exit).length;

function shuffled(items, rng) {
  const result = [...items];
  for (let i = result.length - 1; i > 0; i--) {
    const j = Math.floor(rng() * (i + 1));
    [result[i], result[j]] = [result[j], result[i]];
  }
  return result;
}

// Every candidate carries its independent route at orientations 0, 1 and 2.
// Grid membership only proposes a lock; the swept tracer certifies it below.
function candidatePool(base, boards, maxBends) {
  const pool = [];
  for (const cell of base.cells) for (let dir = 0; dir < 6; dir++) {
    const tile = { q: cell.q, r: cell.r, dir };
    // All six orientations: the chain only constrains 0/1/2, but the endgame
    // is played at 3/4/5 too, and leaving those to chance is what produced
    // locks that open at exactly one of the six.
    const routes = boards.map(board => trace(board, tile, [], true));
    if (routes.slice(0, 3).some(route => route.status !== 'exit')) continue;
    const bends = routes.map(r => r.status === 'exit' ? countBends(r) : Infinity);
    if (bends[1] > maxBends) continue;
    pool.push({
      tile, position: positionKey(tile), bends, cells: routes.map(route => route.steps.length),
      exits: routes.map(route => route.status === 'exit'),
      at: routes.map(route => new Set(route.steps.slice(1).map(positionKey))),
    });
  }
  return pool;
}

// A/B/C/D is a three-turn chain, not three independent long routes.
// At 0 all four are locked. At +1 only B can leave. At +2 only C can leave;
// A and D still hold each other. Turning back to +1 frees A, then D.
// The solver certifies that no one- or two-turn plan clears the board.
export function createDeepLock(base, {
  seed = 0, minHeroBends = 6, maxHeroBends = 70, maxChecks = 2000000,
} = {}) {
  const rng = random(seed);
  const boards = [0, 1, 2, 3, 4, 5].map(turn => rotateBoard(base, turn));
  const pool = candidatePool(base, boards, maxHeroBends);
  const candidates = shuffled(pool, rng);
  const heroes = candidates.filter(c => c.bends[1] >= minHeroBends);
  let checks = 0, formalChecks = 0;
  for (const a of heroes) {
    // D holds A at 0 and at +2, and never stands on A's +1 departure.
    // A and D deadlock at 0 and at +2 and open at +1 — that is the chain. The
    // added requirement is that +3 opens too: a player stuck at +2 turns one
    // way or the other and something moves either way, instead of one
    // direction being right and the other five a dead end.
    const tails = candidates.filter(d => d.position !== a.position
      && a.at[0].has(d.position) && d.at[0].has(a.position)
      && a.at[2].has(d.position) && d.at[2].has(a.position)
      && !a.at[1].has(d.position)
      && ((a.exits[3] && !a.at[3].has(d.position)) || (d.exits[3] && !d.at[3].has(a.position))));
    for (const d of tails) {
      // C holds A at +1 and leaves alone at +2 once B is gone.
      const seconds = candidates.filter(c => c.position !== a.position && c.position !== d.position
        && a.at[1].has(c.position) && !c.at[2].has(a.position) && !c.at[2].has(d.position));
      for (const c of seconds) {
        // B is A's blocker at 0 and is the only piece that leaves at +1.
        const gates = candidates.filter(b => b.position !== a.position && b.position !== c.position && b.position !== d.position
          && a.at[0].has(b.position) && !b.at[1].has(a.position) && !b.at[1].has(c.position) && !b.at[1].has(d.position)
          && (c.at[1].has(a.position) || c.at[1].has(d.position) || c.at[1].has(b.position)));
        for (const b of gates) {
          if (++checks > maxChecks) return null;
          const tiles = [a, b, c, d].map((candidate, i) => ({ ...candidate.tile, id: `t${i}`, color: i }));
          const [hero, gate, second, tail] = tiles;
          formalChecks++;
          // Formal certification of every stage with the production swept tracer.
          if (tiles.some(tile => trace(boards[0], tile, tiles).status === 'exit')) continue;
          if (trace(boards[1], gate, tiles).status !== 'exit') continue;
          const afterGate = [hero, second, tail];
          if (afterGate.some(tile => trace(boards[1], tile, afterGate).status === 'exit')) continue;
          if (trace(boards[2], second, afterGate).status !== 'exit') continue;
          const afterSecond = [hero, tail];
          if (afterSecond.some(tile => trace(boards[2], tile, afterSecond).status === 'exit')) continue;
          if (trace(boards[1], hero, afterSecond).status !== 'exit') continue;
          if (trace(boards[1], tail, [tail]).status !== 'exit') continue;
          // Certify the two-sided release with the real swept tracer, not the
          // cell-occupancy approximation the filter above uses.
          if (![hero, tail].some(t => trace(boards[3], t, afterSecond).status === 'exit')) continue;
          const level = { ...base, tiles, moveLimit: tiles.length };
          const solution = solveRotations(level);
          if (!solution.solvable || solution.exhausted || solution.rotations !== 3) continue;
          return {
            tiles, placements: [1, 1, 2, 1], hero,
            heroRoute: { bends: a.bends[1], cells: a.cells[1] },
            actions: [
              { type: 'rotate', direction: 1 }, { type: 'tap', id: gate.id },
              { type: 'rotate', direction: 1 }, { type: 'tap', id: second.id },
              { type: 'rotate', direction: -1 }, { type: 'tap', id: hero.id }, { type: 'tap', id: tail.id },
            ],
            minimumRotations: solution.rotations, solution,
            search: { checks, formalChecks, heroCandidates: heroes.length, poolSize: pool.length },
          };
        }
      }
    }
  }
  return null;
}

// Reverse insertion keeps the chain intact while raising how much of the
// board depends on turning. Each inserted piece must leave at its scheduled
// orientation, and the solver must still need exactly three turns afterwards.
// Rotation is free and it is what the game is about, so depth is the thing to
// grow, not cap. Scheduling pieces at orientations 3/4/5 as well as 0/1/2 is
// what lets a level need five or six turns instead of always exactly three —
// and each of those extra turns pays out, because the piece scheduled there is
// waiting to leave.
export function growDeepLevel(base, lock, {
  seed = 0, depth = 3, perTurn = 2, maxHeroBends = 70, minRotations = 3, target = null,
  showcase = 2, showcaseMinDistance = 6, showcaseMaxDistance = 20,
} = {}) {
  const rng = random(seed + 7919);
  const boards = [0, 1, 2, 3, 4, 5].map(turn => rotateBoard(base, turn));
  // A layer piece only needs a departure at its own orientation. Requiring
  // exits at every orientation would leave almost nothing to insert.
  const layerPool = boards.map(board => {
    const pool = [];
    for (const cell of base.cells) for (let dir = 0; dir < 6; dir++) {
      const tile = { q: cell.q, r: cell.r, dir }, route = trace(board, tile, [], true);
      if (route.status === 'exit' && countBends(route) <= maxHeroBends) pool.push({ tile, position: positionKey(tile), bends: countBends(route) });
    }
    return pool;
  });
  const tiles = [...lock.tiles], placements = [...lock.placements];
  // Depth comes from a quota per orientation, not from random shares. Shares
  // left some orientations empty, and an orientation with nothing waiting is a
  // turn that pays nothing — the one thing that reliably reads as boring.
  const schedule = [];
  for (let turn = 0; turn < depth; turn++) for (let i = 0; i < perTurn; i++) schedule.push(turn);
  if (target != null) schedule.length = Math.max(0, Math.min(schedule.length, target - tiles.length));
  let rejected = { orientationless: 0, shortcut: 0, unfilled: 0 };
  for (const orientation of [...schedule].sort((a, b) => b - a)) {
    const occupied = new Set(tiles.map(positionKey));
    const choices = shuffled(layerPool[orientation].filter(c => !occupied.has(c.position)), rng);
    let chosen = null, fallback = null;
    for (const c of choices) {
      const tile = { ...c.tile, id: `t${tiles.length}`, color: tiles.length % 7 }, proposed = [...tiles, tile];
      if (trace(boards[orientation], tile, proposed).status !== 'exit') { rejected.orientationless++; continue; }
      // Prefer pieces that genuinely wait for this turn: blocked at every earlier orientation.
      const waits = [...Array(orientation).keys()].every(earlier => trace(boards[earlier], tile, proposed).status !== 'exit');
      if (!waits && fallback) continue;
      const solution = solveRotations({ ...base, tiles: proposed, moveLimit: proposed.length });
      if (!solution.solvable || solution.exhausted || solution.rotations < minRotations) { rejected.shortcut++; continue; }
      if (waits) { chosen = tile; break; }
      fallback = tile;
    }
    chosen = chosen || fallback;
    // One orientation running out of candidates must not abandon the rest.
    if (!chosen) { rejected.unfilled++; continue; }
    tiles.push(chosen); placements.push(orientation);
  }
  // The chain locks everything at the opening by construction, so a level built
  // only from it hands a casual player two rim pieces and a third of a second
  // of animation before the thinking starts. Reserve a couple of slots for
  // pieces that are tappable immediately and whose route is worth watching:
  // long enough to read as a journey, short enough not to hit the ceiling.
  for (let i = 0; i < showcase; i++) {
    const occupied = new Set(tiles.map(positionKey));
    let best = null;
    for (const c of shuffled(layerPool[0].filter(x => !occupied.has(x.position)), rng)) {
      const tile = { ...c.tile, id: `t${tiles.length}`, color: tiles.length % 7 }, proposed = [...tiles, tile];
      const route = trace(boards[0], tile, proposed);
      if (route.status !== 'exit') continue;
      const { distance } = exitTiming(route);
      if (distance < showcaseMinDistance || distance > showcaseMaxDistance) continue;
      // It must not shortcut the lock it is decorating.
      const solution = solveRotations({ ...base, tiles: proposed, moveLimit: proposed.length });
      if (!solution.solvable || solution.exhausted || solution.rotations < minRotations) continue;
      if (!best || distance > best.distance) best = { tile, distance };
    }
    if (!best) break;
    tiles.push(best.tile); placements.push(0);
  }

  const level = {
    ...base, tiles, moveLimit: tiles.length,
    name: `${(base.name || 'route').replace(' · 路线草图', '')} · 深旋转`,
    experience: { kind: 'deep', feature: { id: lock.hero.id } },
  };
  const solution = solveRotations(level);
  level.experience.actions = solution.actions;
  const errors = validateLevel(level);
  if (errors.length) throw new Error(errors.join('; '));
  return { level, placements, solution, rejected };
}

// Structural evidence for the difficulty bands: how much of the board waits
// for a turn, how many pieces each turn releases, and whether the direction
// of the first turn is a real choice.
// How far a piece swings between "looks hopeless" and "walks straight out".
// Cost is what the eye judges from: cells travelled plus twice the bends. A
// piece that reads as a 128-cost tangle at one orientation and a 5-cost stroll
// at another is where the satisfaction comes from; families whose pieces all
// sit around the same cost no matter how the board turns feel mechanical.
export function contrastStats(level) {
  const boards = [0, 1, 2, 3, 4, 5].map(k => rotateBoard(level, k));
  const cost = route => route.status === 'exit' ? route.steps.length + 2 * countBends(route) : null;
  const HOPELESS = 60;
  const swings = [];
  for (const tile of level.tiles) {
    const costs = boards.map(board => cost(trace(board, tile, [], true)));
    const reachable = costs.filter(c => c != null);
    if (!reachable.length) continue;
    const best = Math.min(...reachable);
    const opening = trace(level, tile, level.tiles);
    const seen = opening.status === 'exit' ? cost(opening) : (costs[0] ?? HOPELESS);
    swings.push(seen - best);
  }
  if (!swings.length) return { contrast: 0, maxSwing: 0 };
  return {
    contrast: swings.reduce((a, b) => a + b, 0) / swings.length,
    maxSwing: Math.max(...swings),
  };
}

// What it costs to know what you may tap. A player verifies a piece by
// following its line until it leaves the board or meets somebody; length and
// bends are what that costs the eye. This is the difficulty the design brief
// asks for — 无法一下子判断 — and it is not board size: a wide board whose
// nearest free piece is three cells away reads instantly, while a small one
// where every free piece hides behind a thirty-cell switchback does not.
//
// Grazes are counted apart because they are not difficulty at all, they are a
// lie. A piece can have an empty line and still be held, by a neighbour the
// route never touches; following that line tells the player it is free, and
// the tap does nothing. That is the "many actions, no result" the brief rules
// out, so a level wants none of these at its opening.
export function legibility(level) {
  const occupant = new Map(level.tiles.map(t => [`${t.q},${t.r}`, t.id]));
  const costs = [];
  let grazeTraps = 0;
  for (const tile of level.tiles) {
    const geo = trace(level, tile, [], true);          // the drawn line, ignoring who sits on it
    const real = trace(level, tile, level.tiles);      // where the piece would actually stop
    const onRoute = geo.steps.some(s => { const who = occupant.get(`${s.q},${s.r}`); return who && who !== tile.id; });
    if (real.status !== 'exit' && !onRoute) grazeTraps++;
    // Verification stops where the eye stops: at the blocker, or at the edge.
    const seen = real.status === 'exit' ? geo : real;
    costs.push({ id: tile.id, free: real.status === 'exit', cost: seen.steps.length + 2 * countBends(seen) });
  }
  const free = costs.filter(c => c.free).map(c => c.cost);
  const all = costs.map(c => c.cost).sort((a, b) => a - b);
  return {
    glanceCost: free.length ? Math.min(...free) : null,   // the cheapest correct move to find
    medianVerify: all.length ? all[Math.floor(all.length / 2)] : 0,
    grazeTraps,
  };
}

// What the player actually watches. Rotation costs no steps precisely so that
// people try things; the payout is the animation of a piece threading a winding
// route and leaving. So the show is measurable: how long each departure plays,
// whether the level opens with one, and — the failure the design brief names
// outright — how many actions can pass with nothing happening at all.
// What counts as a cruise, and what counts as an opening worth watching, were
// both picked in milliseconds while a piece crossed one unit in 120ms. Speed is
// a tuning dial, so holding those milliseconds fixed while the dial moves does
// not hold the experience fixed — it silently demands longer routes. Raising
// the speed once made 20 of 50 shipped levels "fail" an opening gate they had
// passed, purely from the unscaled number. They scale with the dial instead.
const SHOW_CALIBRATED_AT = 120;
const showScale = () => MOTION.exitMsPerUnit / SHOW_CALIBRATED_AT;
export const CRUISE_MS_AT_120 = 900;
const CRUISE_MS = CRUISE_MS_AT_120 * showScale();
export const openingShowFloor = (msAt120 = 800) => msAt120 * showScale();

export function showStats(level) {
  const solution = solveRotations(level);
  if (!solution.solvable || !solution.actions) return null;
  const game = new Game(level);
  const shows = [];
  let dry = 0, maxDry = 0, firstShow = null, sinceStart = 0;
  for (const action of solution.actions) {
    if (action.type === 'rotate') { game.rotate(action.direction); dry++; sinceStart++; maxDry = Math.max(maxDry, dry); continue; }
    const result = game.tap(action.id);
    sinceStart++;
    if (result.status === 'exit') {
      const ms = exitTiming(result).duration;
      shows.push(ms);
      if (firstShow === null) firstShow = { ms, afterActions: sinceStart };
      dry = 0;
    } else { dry++; maxDry = Math.max(maxDry, dry); }
  }
  if (!shows.length) return null;
  const sorted = [...shows].sort((a, b) => a - b);
  // What the player can see straight away if they pick well, rather than what
  // the optimal script happens to tap first. An opening whose only departure is
  // a piece already touching the rim plays for 0.3s and shows nothing.
  const opening = new Game(level);
  const openingShows = available(level, opening.tiles)
    .map(t => exitTiming(trace(level, t, opening.tiles)).duration);
  return {
    exits: shows.length,
    openingChoices: openingShows.length,
    openingBestMs: openingShows.length ? Math.round(Math.max(...openingShows)) : 0,
    totalMs: Math.round(shows.reduce((a, b) => a + b, 0)),
    medianMs: Math.round(sorted[Math.floor(sorted.length / 2)]),
    longestMs: Math.round(sorted[sorted.length - 1]),
    // A cruise: long enough that watching it is the point, not a blink.
    cruises: shows.filter(ms => ms >= CRUISE_MS).length,
    firstShowMs: firstShow ? Math.round(firstShow.ms) : null,
    firstShowAfter: firstShow ? firstShow.afterActions : null,
    maxDryActions: maxDry,
  };
}

export function deepLevelStats(level) {
  const n = level.tiles.length, solution = solveRotations(level);
  let board = level, remaining = [...level.tiles];
  const drain = () => { for (;;) { const free = available(board, remaining); if (!free.length) return; const ids = new Set(free.map(t => t.id)); remaining = remaining.filter(t => !ids.has(t.id)); } };
  drain();
  const lockedAtStart = remaining.length;
  const openings = [1, -1].filter(direction => available(rotateBoard(board, direction), remaining).length > 0).length;
  const releases = [];
  for (const action of solution.actions) {
    if (action.type !== 'rotate') continue;
    const before = remaining.length;
    board = rotateBoard(board, action.direction);
    drain();
    releases.push(before - remaining.length);
  }
  return {
    pieces: n, rotations: solution.rotations, lockedShare: lockedAtStart / n, lockedAtStart,
    firstTurnDirections: openings, releasePerTurn: releases, minRelease: releases.length ? Math.min(...releases) : 0,
    waves: solution.waves.map(wave => wave.length), states: solution.states,
  };
}

// Player-side audit over every reachable state (any tap order, any turn
// sequence). Removal only reduces occupancy and turns are reversible, so no
// reachable state can be unsolvable — the audit proves it rather than assuming
// it — and it measures how many blind turns a player can run into.
// A level is judged on its endgame with this many pieces or fewer left.
const ENDGAME_PIECES = 3;

// How busy the drawing is, as two numbers taken from the same data. A cell's
// six ports are paired into three chords; a chord joining opposite ports is a
// diameter, drawn as a straight line, and two diameters in one cell always
// cross. So "the board is all straight lines" and "there are too many crossing
// points" are one property seen twice — which is why the filler that paired
// leftover ports straight across produced both at once.
export function trackShape(level) {
  let pairs = 0, straight = 0, crossings = 0, busiest = 0;
  for (const cell of level.cells) {
    const seen = new Set(), chords = [];
    for (let port = 0; port < 6; port++) {
      if (seen.has(port)) continue;
      const other = cell.tracks[port];
      seen.add(port); seen.add(other);
      chords.push([port, other]);
    }
    const between = (x, a, b) => { for (let k = (a + 1) % 6; k !== b; k = (k + 1) % 6) if (k === x) return true; return false; };
    let here = 0;
    for (let i = 0; i < chords.length; i++) {
      pairs++;
      if ((chords[i][0] + 3) % 6 === chords[i][1]) straight++;
      for (let j = i + 1; j < chords.length; j++) {
        const [a, b] = chords[i], [c, d] = chords[j];
        if (between(c, a, b) !== between(d, a, b)) here++;
      }
    }
    crossings += here;
    busiest = Math.max(busiest, here);
  }
  return {
    straightShare: pairs ? straight / pairs : 0,
    crossPerCell: level.cells.length ? crossings / level.cells.length : 0,
    crossings, busiestCell: busiest,
  };
}

// The endgame question — with a handful of pieces left, how many of the six
// orientations release anything — used to be answered from the same breadth
// search that counts dead turns. On a dense board that search hits its state
// budget long before it reaches any endgame, so it reported `null`, and the
// gate `endgameMinOpen >= 3` read null as a failure. Every level past about
// eleven pieces was rejected for an endgame nobody had measured. That is why
// no level in this project has ever been more than a third pieces.
//
// Enumerating the endgames directly costs nothing by comparison — C(26,3) is
// 2600 — and it finishes, so a dense board gets a real answer. Reachability is
// not checked: the enumeration is a superset of the endgames a player can
// arrive at, which errs toward caution rather than toward a silent pass.
//
// The statistic is the SHARE of endgames that are tight, not the minimum over
// them. A minimum taken over more subsets falls for arithmetic reasons alone —
// the same confound that made `doubleDead` look eight times worse for deep
// levels when the rate was 2% against 5%. By share, 26-piece boards come in at
// 0.0% against 0.1% for 11-piece ones: they are not worse, they were unmeasured.
export function endgameScan(level, k = ENDGAME_PIECES) {
  const boards = Array.from({ length: 6 }, (_, i) => rotateBoard(level, i));
  const ids = level.tiles.map(t => t.id);
  const counts = {};
  let subsets = 0, minOpen = 6, worst = null;
  const visit = (from, pick) => {
    if (pick.length) {
      const tiles = level.tiles.filter(t => pick.includes(t.id));
      let open = 0;
      for (let o = 0; o < 6; o++) if (available(boards[o], tiles).length) open++;
      counts[open] = (counts[open] || 0) + 1;
      subsets++;
      if (open < minOpen) { minOpen = open; worst = [...pick].sort().join(','); }
    }
    if (pick.length === k) return;
    for (let i = from; i < ids.length; i++) visit(i + 1, [...pick, ids[i]]);
  };
  visit(0, []);
  const tight = (counts[0] || 0) + (counts[1] || 0);
  return { subsets, minOpen, worst, tightStates: tight, tightShare: subsets ? tight / subsets : 0 };
}

export function deadTurnAudit(level, maxStates = 20000) {
  const boards = Array.from({ length: 6 }, (_, i) => rotateBoard(level, i));
  const keyOf = (o, rem) => o + ':' + [...rem].sort().join(',');
  const start = { o: 0, rem: new Set(level.tiles.map(t => t.id)) };
  const seen = new Map([[keyOf(0, start.rem), start]]), queue = [start];
  let stuckStates = 0, doubleDead = 0, maxDeadTurns = 0, unsolvable = 0;
  // The endgame is where every model complained: two pieces left, nothing on
  // the board saying which way to turn. Count how many of the six orientations
  // release anything at all — one is a 1-in-6 guess with a dead end behind
  // every other door, which is what made an agent give up on a solvable level.
  const openCache = new Map();
  let endgameMinOpen = 6, endgameTightStates = 0, endgameWorst = null;
  const openOrientations = rem => {
    const k = [...rem].sort().join(',');
    if (openCache.has(k)) return openCache.get(k);
    const tiles = level.tiles.filter(t => rem.has(t.id));
    let n = 0;
    for (let o = 0; o < 6; o++) if (available(boards[o], tiles).length) n++;
    openCache.set(k, n);
    return n;
  };
  while (queue.length && seen.size < maxStates) {
    const state = queue.shift();
    if (!state.rem.size) continue;
    if (state.rem.size <= ENDGAME_PIECES) {
      const open = openOrientations(state.rem);
      if (open <= 1) endgameTightStates++;
      if (open < endgameMinOpen) { endgameMinOpen = open; endgameWorst = [...state.rem].sort().join(','); }
    }
    const tiles = level.tiles.filter(t => state.rem.has(t.id)), free = available(boards[state.o], tiles);
    if (!free.length) {
      stuckStates++;
      if (![1, -1].some(d => available(boards[(state.o + d + 6) % 6], tiles).length)) doubleDead++;
      let nearest = 6;
      for (const d of [1, -1]) for (let k = 1; k < 6; k++) if (available(boards[(state.o + d * k + 6) % 6], tiles).length) { nearest = Math.min(nearest, k); break; }
      if (nearest === 6) unsolvable++; else maxDeadTurns = Math.max(maxDeadTurns, nearest - 1);
    }
    for (const t of free) {
      const rem = new Set(state.rem); rem.delete(t.id);
      const k = keyOf(state.o, rem);
      if (!seen.has(k)) { const next = { o: state.o, rem }; seen.set(k, next); queue.push(next); }
    }
    for (const d of [1, -1]) {
      const o = (state.o + d + 6) % 6, k = keyOf(o, state.rem);
      if (!seen.has(k)) { const next = { o, rem: state.rem }; seen.set(k, next); queue.push(next); }
    }
  }
  const endgame = endgameScan(level);
  return { states: seen.size, stuckStates, doubleDead, maxDeadTurns, unsolvable,
    // Endgame numbers come from the complete enumeration, never from this
    // search — it may not have reached an endgame at all.
    endgameMinOpen: endgame.minOpen, endgameTightStates: endgame.tightStates,
    endgameTightShare: endgame.tightShare, endgameSubsets: endgame.subsets,
    endgameWorst: endgame.worst, exhausted: seen.size >= maxStates };
}

export const deepLevelKey = level => level.tiles.map(t => `${t.q},${t.r},${t.dir}`).sort().join('|');
export { key as cellKey };