/**
 * Canonical tile patterns for linear features.
 * Each pattern is defined by a base edge mask and a human-readable name.
 * Patterns can be rotated by 60° increments to produce all placements.
 */

import type { EdgeMask } from './types.js';
import { HexEdge } from './types.js';
import { edgeMask, rotateMask, edgeCount } from './edge-connectivity.js';

export interface TilePattern {
  id: string;
  name: string;
  baseMask: EdgeMask;
  /** Number of distinct rotations (accounting for symmetry) */
  rotations: number;
}

/** All canonical patterns for linear features */
export const TILE_PATTERNS: TilePattern[] = [
  {
    id: 'dead-end',
    name: 'Dead End',
    baseMask: edgeMask(HexEdge.E),
    rotations: 6,
  },
  {
    id: 'straight',
    name: 'Straight',
    baseMask: edgeMask(HexEdge.E, HexEdge.W),
    rotations: 3, // Symmetric: E-W = same as W-E
  },
  {
    id: 'gentle-curve',
    name: 'Wide Curve',
    baseMask: edgeMask(HexEdge.E, HexEdge.SW),
    rotations: 6,
  },
  {
    id: 'sharp-bend',
    name: 'Sharp Bend',
    baseMask: edgeMask(HexEdge.E, HexEdge.SE),
    rotations: 6,
  },
  {
    id: 'y-junction',
    name: 'Y Split',
    baseMask: edgeMask(HexEdge.NE, HexEdge.SE, HexEdge.W),
    rotations: 6,
  },
  {
    id: 'y-junction-wide',
    name: 'Y Wide',
    baseMask: edgeMask(HexEdge.NE, HexEdge.SW, HexEdge.SE),
    rotations: 6,
  },
  {
    id: 'crossroads',
    name: 'Cross',
    baseMask: edgeMask(HexEdge.NE, HexEdge.E, HexEdge.SW, HexEdge.W),
    rotations: 3,
  },
];

/**
 * Get all unique rotations for a pattern.
 * Returns array of { mask, rotation } where rotation is the number of 60° steps.
 */
export function getPatternRotations(pattern: TilePattern): Array<{ mask: EdgeMask; rotation: number }> {
  const seen = new Set<EdgeMask>();
  const result: Array<{ mask: EdgeMask; rotation: number }> = [];

  for (let r = 0; r < 6; r++) {
    const mask = rotateMask(pattern.baseMask, r);
    if (!seen.has(mask)) {
      seen.add(mask);
      result.push({ mask, rotation: r });
    }
  }

  return result;
}

/**
 * Rotate a mask by N steps (each step = 60° clockwise).
 */
export function rotatePattern(mask: EdgeMask, steps: number): EdgeMask {
  return rotateMask(mask, steps);
}