// Inbound dial. A turn moves a notch on a 6-mark ring. It does not slide tracks
// under aircraft, and it does not call rotateBoard. Mouths are fixed world
// objects: open iff mouth.tick === dial.
import { opposite, trace } from '../../src/core.js';
import { pathPoints, position, sweepPath, PORTS } from '../../src/path-math.js';
import { visualSide, SIDES } from '../airport/core.js';

export { SIDES };
export const COLORS = {
  0: { name: '草莓', color: '#EE5398' },
  8: { name: '可可', color: '#B5806A' },
};

const boardOf = level => ({ cells: level.cells });
const clone = value => structuredClone(value);

function departure(level, q, r, dir) {
  const route = trace(boardOf(level), { id: 'probe', q, r, dir }, [], true);
  if (route.status !== 'exit') return { status: route.status, route, points: pathPoints(route) };
  const last = route.steps.at(-1);
  return { status: 'exit', route, points: pathPoints(route), side: visualSide(last.q, last.r, last.exit), exitDir: last.exit };
}

export function catalog(level) {
  return level.mouths.map(mouth => {
    const stand = level.stands.find(item => item.id === mouth.standId);
    const inbound = departure(level, stand.q, stand.r, mouth.departDir);
    const parkedDir = opposite(mouth.departDir);
    const outbound = departure(level, stand.q, stand.r, parkedDir);
    return {
      ...mouth,
      stand,
      side: inbound.side,
      sideName: SIDES[inbound.side],
      parkedDir,
      exitSide: outbound.side,
      exitSideName: SIDES[outbound.side],
      arrivalPoints: [...inbound.points].reverse(),
      departPoints: outbound.points,
      cells: inbound.route.steps.length,
    };
  });
}

export function createState(level) {
  return {
    dial: level.dial,
    stars: 0,
    planes: level.arrivals.map(plane => ({
      id: plane.id, color: plane.color, side: plane.side, state: 'waiting',
      q: null, r: null, dir: null, standId: null, mouthId: null,
    })),
  };
}

const parked = state => state.planes.filter(plane => plane.state === 'parked');
const obstacles = planes => planes.map(plane => ({ ...position(plane.q, plane.r), id: plane.id }));

export function checkLanding(level, state, planeId) {
  const plane = state.planes.find(item => item.id === planeId);
  if (!plane || plane.state !== 'waiting') return { status: 'invalid' };
  const mouths = catalog(level).filter(mouth => mouth.tick === state.dial && mouth.side === plane.side && mouth.stand.color === plane.color);
  if (!mouths.length) return { status: 'no-route', plane };
  const taken = new Set(parked(state).map(item => `${item.q},${item.r}`));
  const free = mouths.filter(mouth => !taken.has(`${mouth.stand.q},${mouth.stand.r}`));
  if (!free.length) return { status: 'no-stand', plane };
  const blocks = obstacles(parked(state));
  const legal = [], blocked = [];
  for (const mouth of free) {
    const hit = sweepPath(mouth.arrivalPoints, blocks);
    if (!hit) legal.push(mouth);
    else blocked.push({ mouth, blocker: hit.blocker, point: hit.point, travel: hit.points });
  }
  if (legal.length > 1) return { status: 'ambiguous', plane, candidates: legal };
  if (legal.length === 1) return { status: 'land', plane, mouth: legal[0] };
  if (blocked.length === 1) return { status: 'blocked', plane, ...blocked[0] };
  return { status: 'ambiguous', plane, candidates: blocked };
}

export function checkRelocate(level, state, planeId) {
  const plane = state.planes.find(item => item.id === planeId);
  if (!plane || plane.state !== 'parked') return { status: 'invalid' };
  const outbound = departure(level, plane.q, plane.r, plane.dir);
  if (outbound.status !== 'exit') return { status: 'no-route', plane };
  const end = outbound.points.at(-1), port = PORTS[outbound.exitDir];
  const swept = [...outbound.points, { x: end.x + port.x * 4, y: end.y + port.y * 4 }];
  const hit = sweepPath(swept, obstacles(parked(state).filter(item => item.id !== plane.id)));
  if (hit) return { status: 'blocked', plane, blocker: hit.blocker, point: hit.point, travel: hit.points, side: outbound.side };
  return { status: 'relocate', plane, side: outbound.side, sideName: SIDES[outbound.side], points: outbound.points };
}

function applyLanding(state, check) {
  const next = clone(state);
  const plane = next.planes.find(item => item.id === check.plane.id);
  plane.state = 'parked';
  plane.q = check.mouth.stand.q;
  plane.r = check.mouth.stand.r;
  plane.dir = check.mouth.parkedDir;
  plane.standId = check.mouth.standId;
  plane.mouthId = check.mouth.id;
  plane.side = null;
  next.stars += 1;
  return next;
}

function applyRelocate(state, check) {
  const next = clone(state);
  const plane = next.planes.find(item => item.id === check.plane.id);
  plane.state = 'waiting';
  plane.side = check.side;
  plane.q = plane.r = plane.dir = plane.standId = plane.mouthId = null;
  next.stars += 1;
  return next;
}

export function transition(level, state, action) {
  if (action.type === 'confirm') {
    const dial = action.dial, steps = action.steps;
    if (!Number.isInteger(dial) || dial < 0 || dial > 5 || !Number.isInteger(steps) || steps < 1) return { commit: false, result: { status: 'invalid' } };
    const next = clone(state);
    next.dial = dial;
    next.stars += steps;
    return { commit: true, state: next, result: { status: 'confirmed', dial, steps } };
  }
  if (action.type === 'land') {
    const check = checkLanding(level, state, action.id);
    if (check.status !== 'land') return { commit: false, result: check };
    return { commit: true, state: applyLanding(state, check), result: check };
  }
  if (action.type === 'relocate') {
    const check = checkRelocate(level, state, action.id);
    if (check.status !== 'relocate') return { commit: false, result: check };
    return { commit: true, state: applyRelocate(state, check), result: check };
  }
  return { commit: false, result: { status: 'invalid' } };
}

export function isWon(state) {
  return state.planes.length > 0 && state.planes.every(plane => plane.state === 'parked');
}

export class Inbound {
  constructor(level) {
    this.level = level;
    this.state = createState(level);
    this.history = [];
  }
  get won() { return isWon(this.state); }
  act(action) {
    if (action.type === 'undo') {
      if (!this.history.length) return { status: 'invalid' };
      this.state = this.history.pop();
      return { status: 'undone' };
    }
    const outcome = transition(this.level, this.state, action);
    if (!outcome.commit) return outcome.result;
    this.history.push(clone(this.state));
    this.state = outcome.state;
    return { ...outcome.result, won: this.won, stars: this.state.stars };
  }
}

export function validateInbound(level) {
  const issues = [];
  const mouths = catalog(level);
  for (const mouth of mouths) {
    if (mouth.side === undefined) issues.push(`${mouth.id} 没有出口`);
    if (mouth.cells < 1 || mouth.cells > 5) issues.push(`${mouth.id} 路径 ${mouth.cells} 格，超出 1–5`);
  }
  for (let dial = 0; dial < 6; dial++) {
    const groups = new Map();
    for (const mouth of mouths.filter(item => item.tick === dial)) {
      const group = `${mouth.side}:${mouth.stand.color}`;
      groups.set(group, (groups.get(group) || 0) + 1);
    }
    for (const [group, count] of groups) if (count > 1) issues.push(`朝向 ${dial} ${group} 有 ${count} 个口`);
  }
  const seen = new Set();
  for (const mouth of mouths) {
    const signature = `${mouth.side}:${mouth.tick}:${mouth.standId}`;
    if (seen.has(signature)) issues.push(`重复口 ${signature}`);
    seen.add(signature);
  }
  return issues;
}

// What a reader can count before touching preview. Independent of dial mutation.
export function reading(level, dial) {
  return catalog(level).map(mouth => ({
    id: mouth.id,
    side: mouth.sideName,
    tick: mouth.tick,
    open: mouth.tick === dial,
    right: (mouth.tick - dial + 6) % 6,
    left: (dial - mouth.tick + 6) % 6,
    exitSide: mouth.exitSideName,
    cells: mouth.cells,
  }));
}