SpaceRace/server/src/game/Grid.ts

import {
  Position,
  TileType,
  GRID_WIDTH,
} from '@spacerace/shared';
import { GAME_CONFIG } from '../config.js';

export class Grid {
  private cols: Map<number, TileType[]> = new Map();
  private _deathLineX: number;
  private _generatedUpToX: number;
  private seed: number;

  constructor(seed: number = 42) {
    this.seed = seed;
    this._deathLineX = 0;
    this._generatedUpToX = 12;
    this.generateCols(0, 25);
    this.clearRunway(0, 20);
  }

  private clearRunway(fromX: number, toX: number): void {
    const start = Math.min(fromX, toX);
    const end = Math.max(fromX, toX);
    for (let x = start; x <= end; x++) {
      this.cols.set(x, Array(GRID_WIDTH).fill('space'));
    }
  }

  get deathLineY(): number {
    return this._deathLineX;
  }

  get generatedUpToY(): number {
    return this._generatedUpToX;
  }

  private randFor(seed: number): number {
    let h = ((this.seed + seed) * 31 + seed * 7 + seed * seed * 13) % 2147483647;
    return (h & 0x7fffffff) / 0x7fffffff;
  }

  getTile(pos: Position): TileType {
    this.ensureCol(pos.y);
    const col = this.cols.get(pos.y);
    if (!col) return 'space';
    return col[pos.x] ?? 'space';
  }

  private ensureCol(y: number): void {
    if (this.cols.has(y)) return;
    if (y > this._generatedUpToX) {
      this.generateCols(this._generatedUpToX, y);
    } else {
      this.generateCols(0, y);
    }
  }

  setTile(pos: Position, tile: TileType): void {
    this.ensureCol(pos.y);
    const col = this.cols.get(pos.y)!;
    col[pos.x] = tile;
  }

  isBlocked(pos: Position): boolean {
    const tile = this.getTile(pos);
    return tile !== 'space';
  }

  isInBounds(pos: Position): boolean {
    return pos.x >= 0 && pos.x < GRID_WIDTH;
  }

  advanceDeathLine(leadingY?: number): number {
    let advance: number = GAME_CONFIG.DEATH_LINE_ADVANCE;
    if (leadingY !== undefined) {
      const maxBehind = 10;
      const distance = leadingY - this._deathLineX;
      if (distance > maxBehind) {
        advance = Math.max(advance, distance - maxBehind);
      }
    }
    this._deathLineX += advance;
    return this._deathLineX;
  }

  generateCols(fromX: number, toX: number): void {
    const start = Math.min(fromX, toX);
    const end = Math.max(fromX, toX);

    for (let x = start; x <= end; x++) {
      if (this.cols.has(x)) continue;

      const col: TileType[] = [];
      const r = this.randFor(x * 7919);

      const pattern = Math.abs((x * 13 + this.seed * 7) % 5);

      for (let lane = 0; lane < GRID_WIDTH; lane++) {
        const tileR = this.randFor(x * 1000 + lane);
        switch (pattern) {
          case 0: col.push(tileR < GAME_CONFIG.TRACK_DENSITY * 0.5 ? 'asteroid' : 'space'); break;
          case 1: col.push(lane < 3 && tileR < 0.6 ? 'asteroid' : 'space'); break;
          case 2: col.push(lane >= 5 && tileR < 0.6 ? 'asteroid' : 'space'); break;
          case 3: col.push((lane < 2 || lane > 5) && tileR < 0.7 ? 'asteroid' : 'space'); break;
          case 4: col.push(tileR < GAME_CONFIG.TRACK_DENSITY * 1.5 ? 'asteroid' : 'space'); break;
        }
      }
      // Ensure at least 1 lane is open
      const blocked = col.every((t) => t !== 'space');
      if (blocked) {
        const openLane = Math.floor(this.randFor(x * 31337) * GRID_WIDTH);
        (col as any)[openLane] = 'space';
      }
      this.cols.set(x, col);
    }

    if (toX > this._generatedUpToX) {
      this._generatedUpToX = Math.max(this._generatedUpToX, toX);
    }
  }

  ensureAheadOf(leadingX: number): number {
    const neededX = leadingX + 5;
    if (neededX > this._generatedUpToX) {
      this.generateCols(this._generatedUpToX + 1, neededX);
      this._generatedUpToX = neededX;
    }
    return this._generatedUpToX;
  }

  toState(): Record<number, (TileType | null)[]> {
    const state: Record<number, (TileType | null)[]> = {};
    for (const [x, col] of this.cols) {
      state[x] = [...col];
    }
    return state;
  }

  findSafeStart(usedPositions: Position[], startX: number, columnSpread: number = 2): Position | null {
    const candidates: Position[] = [];
    for (let lane = 0; lane < GRID_WIDTH; lane++) {
      for (let colX = startX; colX <= startX + columnSpread; colX++) {
        const pos = { x: lane, y: colX };
        if (
          !this.isBlocked(pos) &&
          !usedPositions.some((p) => p.y === pos.y && p.x === pos.x)
        ) {
          candidates.push(pos);
        }
      }
    }
    if (candidates.length === 0) return null;
    return candidates[Math.floor(this.randFor(startX * 7) * candidates.length)];
  }
}