/**
 * Galaxy Strike Online - Galaxy System (GDD §8)
 * Procedurally generates and manages the 30×20 sector grid.
 * Visibility radius is driven by sensor_array building level + research sensorRange bonus.
 */
class GalaxySystem {
  constructor() {
    this.GRID_W = 30;
    this.GRID_H = 20;
    this._sectors = null;
  }

  /** Lazy-generate the galaxy grid once per server process */
  getSectors() {
    if (!this._sectors) this._sectors = this._generate();
    return this._sectors;
  }

  _generate() {
    const sectors = {};
    for (let y = 0; y < this.GRID_H; y++) {
      for (let x = 0; x < this.GRID_W; x++) {
        const id = `${x}_${y}`;
        const distFromCenter = Math.hypot(x - 15, y - 10) / 18;
        const typeRoll = Math.random();
        let type = 'empty';
        if (typeRoll > 0.70) type = 'asteroid';
        if (typeRoll > 0.88) type = 'npc_territory';
        if (typeRoll > 0.94) type = 'trade_hub';
        if (typeRoll > 0.97 && distFromCenter > 0.4) type = 'ruins';
        if (typeRoll > 0.99 && distFromCenter > 0.6) type = 'void_rift';

        const richness = Math.random();
        sectors[id] = {
          id, x, y, type,
          name:     this._sectorName(x, y),
          threat:   Math.min(10, Math.floor(distFromCenter * 10 + Math.random() * 3)),
          richness: type === 'asteroid' ? (0.3 + richness * 0.7) : 0,
          owner:    null,
          explored: false,
        };
      }
    }
    // Always make the start sector safe
    sectors['15_10'] = {
      id: '15_10', x: 15, y: 10, type: 'trade_hub',
      name: 'New Haven', threat: 0, richness: 0, owner: null, explored: true,
    };
    return sectors;
  }

  _sectorName(x, y) {
    const prefixes = ['Alpha','Beta','Gamma','Delta','Sigma','Tau','Zeta','Omega','Nova','Vega','Lyra','Cygni'];
    const suffixes = ['Prime','Station','Reach','Deep','Expanse','Crossing','Rift','Gate','Void','Fields'];
    const seed = (x * 31 + y * 17) % (prefixes.length * suffixes.length);
    return prefixes[seed % prefixes.length] + ' ' + suffixes[Math.floor(seed / prefixes.length) % suffixes.length];
  }

  getSector(id) { return this.getSectors()[id] || null; }

  /**
   * Mark a sector explored by a player.
   * visRadius controls how many rings of adjacent sectors are also added to exploredSectors.
   * Default radius 1 = only direct neighbours revealed.
   */
  exploreSector(sectorId, playerData, visRadius = 1) {
    const sector = this.getSector(sectorId);
    if (!sector) throw new Error('Sector not found');

    const explored = new Set(playerData.exploredSectors || []);
    explored.add(sectorId);

    // Reveal all sectors within visRadius rings
    const [cx, cy] = sectorId.split('_').map(Number);
    for (let dy = -visRadius; dy <= visRadius; dy++) {
      for (let dx = -visRadius; dx <= visRadius; dx++) {
        if (Math.abs(dx) + Math.abs(dy) > visRadius) continue; // diamond shape
        const nid = `${cx + dx}_${cy + dy}`;
        if (this.getSector(nid)) explored.add(nid);
      }
    }

    playerData.exploredSectors = Array.from(explored);
    return sector;
  }

  /**
   * Return all sectors visible to a player: explored + one ring of fog neighbours.
   * visRadius from sensor_array building + research is already applied by exploreSector;
   * here we add one extra fog ring beyond whatever has been explored.
   */
  getVisibleSectors(playerData, visRadius = 1) {
    const explored = new Set(playerData.exploredSectors || ['15_10']);
    const visible  = new Set(explored);

    // One fog ring beyond all explored sectors
    for (const id of explored) {
      const [x, y] = id.split('_').map(Number);
      for (const [dx, dy] of [[-1,0],[1,0],[0,-1],[0,1],[-1,-1],[1,-1],[-1,1],[1,1]]) {
        const nid = `${x + dx}_${y + dy}`;
        if (this.getSector(nid)) visible.add(nid);
      }
    }

    const all = this.getSectors();
    return Array.from(visible).map(id => {
      const s = { ...all[id] };
      s.explored = explored.has(id);
      if (!s.explored) {
        // Fog-of-war: hide details for unreached but adjacent sectors
        s.name     = '???';
        s.richness = 0;
        s.owner    = null;
        s.type     = 'unknown';
        s.threat   = null;
      }
      return s;
    });
  }

  /** Player claims a sector as home base */
  claimSector(sectorId, playerData) {
    const sector = this.getSector(sectorId);
    if (!sector) throw new Error('Sector not found');
    if (sector.type === 'void_rift') throw new Error('Cannot claim Void Rift sectors');
    sector.owner = playerData.userId;
    this.exploreSector(sectorId, playerData);
    playerData.homeSector = sectorId;
    return sector;
  }

  /** Calculate travel time between two sector IDs using the GDD formula */
  travelSeconds(fromId, toId, fleetSpeed = 10, travelSpeedBonus = 0) {
    const [fx, fy] = fromId.split('_').map(Number);
    const [tx, ty] = toId.split('_').map(Number);
    const distance = Math.hypot(tx - fx, ty - fy);
    const effectiveSpeed = fleetSpeed * (1 + travelSpeedBonus / 100);
    return Math.max(10, Math.round((distance * 300) / Math.max(1, effectiveSpeed)));
  }
}

module.exports = GalaxySystem;